Characterization system for research on energy storage capacitors.

PubMed

Noriega, J R; Iyore, O D; Budime, C; Gnade, B; Vasselli, J

2013-05-01

In this work a characterization system for high energy-density capacitors is described and demonstrated. Capacitors are being designed using thin-film technology in an attempt to achieve higher energy-density levels by operating the devices at a high voltage. These devices are fabricated from layers of 100 nm aluminum and a layer of polyvinylidene fluoride-hexafluoropropylene on a polyethylene naphthalate plastic substrate. The devices have been designed to store electrical charge at up to 200 V. Characterizations of these devices focus on the measurement of capacitance vs bias voltage and temperature, equivalent series resistance, and charge/discharge cycles. For the purpose of the characterization of these capacitors, an electronic charge/discharge interface was designed and tested.

A Hybrid Redox-Supercapacitor System with Anionic Catholyte and Cationic Anolyte

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, B; Macia-Agullo, JA; Prendiville, DG

A significant challenge for energy storage technologies is to realize battery-level energy density and capacitor-level durability and power density in one device. By introducing an electrolyte composed of an anionic catholyte and a cationic anolyte into a symmetric carbon-based supercapacitor configuration, a hybrid electrochemical battery-supercapacitor system using soluble redox species delivers significantly improved energy density from 20 to 42 W.h/kg (based on the electrode mass) and stable capacities for > 10(4) cycles. The ionic species formed in the electrolyte are studied by UV-Vis, Raman and mass spectroscopy to probe the energy storage mechanism. The strategy is general and may providemore » a route to critically-needed fast-charging devices with both high energy density and power. (C) 2014 The Electrochemical Society. All rights reserved.« less

Chemically Integrated Inorganic-Graphene Two-Dimensional Hybrid Materials for Flexible Energy Storage Devices.

PubMed

Peng, Lele; Zhu, Yue; Li, Hongsen; Yu, Guihua

2016-12-01

State-of-the-art energy storage devices are capable of delivering reasonably high energy density (lithium ion batteries) or high power density (supercapacitors). There is an increasing need for these power sources with not only superior electrochemical performance, but also exceptional flexibility. Graphene has come on to the scene and advancements are being made in integration of various electrochemically active compounds onto graphene or its derivatives so as to utilize their flexibility. Many innovative synthesis techniques have led to novel graphene-based hybrid two-dimensional nanostructures. Here, the chemically integrated inorganic-graphene hybrid two-dimensional materials and their applications for energy storage devices are examined. First, the synthesis and characterization of different kinds of inorganic-graphene hybrid nanostructures are summarized, and then the most relevant applications of inorganic-graphene hybrid materials in flexible energy storage devices are reviewed. The general design rules of using graphene-based hybrid 2D materials for energy storage devices and their current limitations and future potential to advance energy storage technologies are also discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Graphene, a material for high temperature devices – intrinsic carrier density, carrier drift velocity, and lattice energy

PubMed Central

Yin, Yan; Cheng, Zengguang; Wang, Li; Jin, Kuijuan; Wang, Wenzhong

2014-01-01

Heat has always been a killing matter for traditional semiconductor machines. The underlining physical reason is that the intrinsic carrier density of a device made from a traditional semiconductor material increases very fast with a rising temperature. Once reaching a temperature, the density surpasses the chemical doping or gating effect, any p-n junction or transistor made from the semiconductor will fail to function. Here, we measure the intrinsic Fermi level (|EF| = 2.93 kBT) or intrinsic carrier density (nin = 3.87 × 106 cm−2K−2·T2), carrier drift velocity, and G mode phonon energy of graphene devices and their temperature dependencies up to 2400 K. Our results show intrinsic carrier density of graphene is an order of magnitude less sensitive to temperature than those of Si or Ge, and reveal the great potentials of graphene as a material for high temperature devices. We also observe a linear decline of saturation drift velocity with increasing temperature, and identify the temperature coefficients of the intrinsic G mode phonon energy. Above knowledge is vital in understanding the physical phenomena of graphene under high power or high temperature. PMID:25044003

Chemical-to-Electricity Carbon: Water Device.

PubMed

He, Sisi; Zhang, Yueyu; Qiu, Longbin; Zhang, Longsheng; Xie, Yun; Pan, Jian; Chen, Peining; Wang, Bingjie; Xu, Xiaojie; Hu, Yajie; Dinh, Cao Thang; De Luna, Phil; Banis, Mohammad Norouzi; Wang, Zhiqiang; Sham, Tsun-Kong; Gong, Xingao; Zhang, Bo; Peng, Huisheng; Sargent, Edward H

2018-05-01

The ability to release, as electrical energy, potential energy stored at the water:carbon interface is attractive, since water is abundant and available. However, many previous reports of such energy converters rely on either flowing water or specially designed ionic aqueous solutions. These requirements restrict practical application, particularly in environments with quiescent water. Here, a carbon-based chemical-to-electricity device that transfers the chemical energy to electrical form when coming into contact with quiescent deionized water is reported. The device is built using carbon nanotube yarns, oxygen content of which is modulated using oxygen plasma-treatment. When immersed in water, the device discharges electricity with a power density that exceeds 700 mW m -2 , one order of magnitude higher than the best previously published result. X-ray absorption and density functional theory studies support a mechanism of operation that relies on the polarization of sp 2 hybridized carbon atoms. The devices are incorporated into a flexible fabric for powering personal electronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High energy density redox flow device

DOEpatents

Chiang, Yet-Ming; Carter, W. Craig; Ho, Bryan Y; Duduta, Mihai; Limthongkul, Pimpa

2014-05-13

Redox flow devices are described in which at least one of the positive electrode or negative electrode-active materials is a semi-solid or is a condensed ion-storing electroactive material, and in which at least one of the electrode-active materials is transported to and from an assembly at which the electrochemical reaction occurs, producing electrical energy. The electronic conductivity of the semi-solid is increased by the addition of conductive particles to suspensions and/or via the surface modification of the solid in semi-solids (e.g., by coating the solid with a more electron conductive coating material to increase the power of the device). High energy density and high power redox flow devices are disclosed. The redox flow devices described herein can also include one or more inventive design features. In addition, inventive chemistries for use in redox flow devices are also described.

Trauma potential and ballistic parameters of cal. 9 mm P.A. dummy launchers.

PubMed

Frank, Matthias; Bockholdt, Britta; Philipp, Klaus-Peter; Ekkernkamp, Axel

2010-07-15

Blank cartridge actuated dummy launching devices are used by migratory bird hunters to train dogs to retrieve downed birds. The devices create a loud noise while simultaneously propelling a hard foam dummy for retrieval. A newly developed dummy launcher is based on a modified cal. 9 mm P.A. blank handgun with an extension tube pinned and welded to the barrel imitation. Currently, there are no experimental investigations on the ballistic background and trauma potential of these uncommon shooting devices. An experimental test set-up consisting of a photoelectric infrared light barrier was used for measurement of the velocity of hard foam dummies propelled with an automatic dummy launcher. Ballistic parameters of the dummies and an aluminium sleeve as improvised projectile (kinetic energy (E), impulse (p), energy density (E') and threshold velocity (v(tsh)) to cause penetrating wounds as a function of cross-sectional density (S)) were calculated. The average velocity (v) of the dummies was measured 25.71 m/s exerting an average impulse (p) of 3.342 Ns. The average kinetic energy (E) was calculated 43.04 J with an average energy density (E') of 0.069 J/mm(2). The average velocity (v) of the aluminium sleeves as improvised projectiles was measured 79.58 m/s exerting an average impulse (p) of 2.228 Ns. The average kinetic energy (E) of the aluminium sleeves was calculated as 88.70 J with an average energy density (E') of 0.282 J/mm(2). The energy delivered by these shooting devices is high enough to cause relevant injuries. The absence of skin penetration must not mislead the emergency physician or forensic expert into neglecting the potential damage from these devices. (c) 2010 Elsevier Ireland Ltd. All rights reserved.

Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors

PubMed Central

Wang, Wei; Guo, Shirui; Lee, Ilkeun; Ahmed, Kazi; Zhong, Jiebin; Favors, Zachary; Zaera, Francisco; Ozkan, Mihrimah; Ozkan, Cengiz S.

2014-01-01

In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO2) anchored graphene and CNT hybrid foam (RGM) architecture for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO2 nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g−1, areal capacitance: 1.11 F cm−2) which leads to an exceptionally high energy density of 39.28 Wh kg−1 and power density of 128.01 kW kg−1. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications. PMID:24663242

Hydrous ruthenium oxide nanoparticles anchored to graphene and carbon nanotube hybrid foam for supercapacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, Wei; Guo, S.; Lee, I.

2014-03-25

In real life applications, supercapacitors (SCs) often can only be used as part of a hybrid system together with other high energy storage devices due to their relatively lower energy density in comparison to other types of energy storage devices such as batteries and fuel cells. Increasing the energy density of SCs will have a huge impact on the development of future energy storage devices by broadening the area of application for SCs. Here, we report a simple and scalable way of preparing a three-dimensional (3D) sub-5 nm hydrous ruthenium oxide (RuO₂) anchored graphene and CNT hybrid foam (RGM) architecturemore » for high-performance supercapacitor electrodes. This RGM architecture demonstrates a novel graphene foam conformally covered with hybrid networks of RuO₂ nanoparticles and anchored CNTs. SCs based on RGM show superior gravimetric and per-area capacitive performance (specific capacitance: 502.78 F g⁻¹, areal capacitance: 1.11 F cm⁻²) which leads to an exceptionally high energy density of 39.28 Wh kg⁻¹ and power density of 128.01 kW kg⁻¹. The electrochemical stability, excellent capacitive performance, and the ease of preparation suggest this RGM system is promising for future energy storage applications.« less

Alkaline Capacitors Based on Nitride Nanoparticles

NASA Technical Reports Server (NTRS)

Aldissi, Matt

2003-01-01

High-energy-density alkaline electrochemical capacitors based on electrodes made of transition-metal nitride nanoparticles are undergoing development. Transition- metal nitrides (in particular, Fe3N and TiN) offer a desirable combination of high electrical conductivity and electrochemical stability in aqueous alkaline electrolytes like KOH. The high energy densities of these capacitors are attributable mainly to their high capacitance densities, which, in turn, are attributable mainly to the large specific surface areas of the electrode nanoparticles. Capacitors of this type could be useful as energy-storage components in such diverse equipment as digital communication systems, implanted medical devices, computers, portable consumer electronic devices, and electric vehicles.

Metal sulfide electrodes and energy storage devices thereof

DOEpatents

Chiang, Yet-Ming; Woodford, William Henry; Li, Zheng; Carter, W. Craig

2017-02-28

The present invention generally relates to energy storage devices, and to metal sulfide energy storage devices in particular. Some aspects of the invention relate to energy storage devices comprising at least one flowable electrode, wherein the flowable electrode comprises an electroactive metal sulfide material suspended and/or dissolved in a carrier fluid. In some embodiments, the flowable electrode further comprises a plurality of electronically conductive particles suspended and/or dissolved in the carrier fluid, wherein the electronically conductive particles form a percolating conductive network. An energy storage device comprising a flowable electrode comprising a metal sulfide electroactive material and a percolating conductive network may advantageously exhibit, upon reversible cycling, higher energy densities and specific capacities than conventional energy storage devices.

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors

NASA Astrophysics Data System (ADS)

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-10-01

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm-3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm-3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors.

PubMed

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-10-17

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm(-3), 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm(-3), which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs.

Sol-gel Technology and Advanced Electrochemical Energy Storage Materials

NASA Technical Reports Server (NTRS)

Chu, Chung-tse; Zheng, Haixing

1996-01-01

Advanced materials play an important role in the development of electrochemical energy devices such as batteries, fuel cells, and electrochemical capacitors. The sol-gel process is a versatile solution for use in the fabrication of ceramic materials with tailored stoichiometry, microstructure, and properties. This processing technique is particularly useful in producing porous materials with high surface area and low density, two of the most desirable characteristics for electrode materials. In addition,the porous surface of gels can be modified chemically to create tailored surface properties, and inorganic/organic micro-composites can be prepared for improved material performance device fabrication. Applications of several sol-gel derived electrode materials in different energy storage devices are illustrated in this paper. V2O5 gels are shown to be a promising cathode material for solid state lithium batteries. Carbon aerogels, amorphous RuO2 gels and sol-gel derived hafnium compounds have been studied as electrode materials for high energy density and high power density electrochemical capacitors.

Graphene-Based Ultra-Light Batteries for Aircraft

NASA Technical Reports Server (NTRS)

Calle, Carlos I.; Kaner, Richard B.

2014-01-01

Develop a graphene-based ultracapacitor prototype that is flexible, thin, lightweight, durable, low cost, and safe and that will demonstrate the feasibility for use in aircraft center dot These graphene-based devices store charge on graphene sheets and take advantage of the large accessible surface area of graphene (2,600 m2/g) to increase the electrical energy that can be stored. center dot The proposed devices should have the electrical storage capacity of thin-film-ion batteries but with much shorter charge/discharge cycle times as well as longer lives center dot The proposed devices will be carbon-based and so will not have the same issues with flammability or toxicity as the standard lithium-based storage cells There are two main established methods for the storage and delivery of electrical energy: center dot Batteries - Store energy with electrochemical reactions - High energy densities - Slow charge/discharge cycles - Used in applications requiring large amounts of energy ? aircraft center dot Electrochemical capacitors - Store energy in electrochemical double layers - Fast charge/discharge cycles - Low energy densities - Used in electronics devices - Large capacitors are used in truck engine cranking

Solid-State High Performance Flexible Supercapacitors Based on Polypyrrole-MnO2-Carbon Fiber Hybrid Structure

NASA Astrophysics Data System (ADS)

Tao, Jiayou; Liu, Nishuang; Ma, Wenzhen; Ding, Longwei; Li, Luying; Su, Jun; Gao, Yihua

2013-07-01

A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an ``in situ growth for conductive wrapping'' and an electrode material of polypyrrole (PPy)-MnO2 nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3 F cm-3 at a discharge current density of 0.1 A cm-3 and an energy density of 6.16 × 10-3 Wh cm-3 at a power density of 0.04 W cm-3, the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the ``in situ growth for conductive wrapping'' method might be generalized to open up new strategies for designing next-generation energy storage devices.

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage

NASA Astrophysics Data System (ADS)

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-11-01

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO2 nanowire/carbon nanotube (CNT) composites and MoO3 nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm-3 at a scan rate of 2 mV s-1 and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm-3 at a power density of 261.4 mW cm-3, and exhibits excellent cycling performance of 99.6% capacitance retention over 10 000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr04819a

Achieving High-Energy-High-Power Density in a Flexible Quasi-Solid-State Sodium Ion Capacitor.

PubMed

Li, Hongsen; Peng, Lele; Zhu, Yue; Zhang, Xiaogang; Yu, Guihua

2016-09-14

Simultaneous integration of high-energy output with high-power delivery is a major challenge for electrochemical energy storage systems, limiting dual fine attributes on a device. We introduce a quasi-solid-state sodium ion capacitor (NIC) based on a battery type urchin-like Na2Ti3O7 anode and a capacitor type peanut shell derived carbon cathode, using a sodium ion conducting gel polymer as electrolyte, achieving high-energy-high-power characteristics in solid state. Energy densities can reach 111.2 Wh kg(-1) at power density of 800 W kg(-1), and 33.2 Wh kg(-1) at power density of 11200 W kg(-1), which are among the best reported state-of-the-art NICs. The designed device also exhibits long-term cycling stability over 3000 cycles with capacity retention ∼86%. Furthermore, we demonstrate the assembly of a highly flexible quasi-solid-state NIC and it shows no obvious capacity loss under different bending conditions.

The strain capacitor: A novel energy storage device

DOE Office of Scientific and Technical Information (OSTI.GOV)

Deb Shuvra, Pranoy; McNamara, Shamus, E-mail: shamus.mcnamara@louisville.edu

2014-12-15

A novel electromechanical energy storage device is reported that has the potential to have high energy densities. It can efficiently store both mechanical strain energy and electrical energy in the form of an electric field between the electrodes of a strain-mismatched bilayer capacitor. When the charged device is discharged, both the electrical and mechanical energy are extracted in an electrical form. The charge-voltage profile of the device is suitable for energy storage applications since a larger portion of the stored energy can be extracted at higher voltage levels compared to a normal capacitor. Its unique features include the potential formore » long lifetime, safety, portability, wide operating temperature range, and environment friendliness. The device can be designed to operate over varied operating voltage ranges by selecting appropriate materials and by changing the dimensions of the device. In this paper a finite element model of the device is developed to verify and demonstrate the potential of the device as an energy storage element. This device has the potential to replace conventional energy storage devices.« less

Structural design of graphene for use in electrochemical energy storage devices.

PubMed

Chen, Kunfeng; Song, Shuyan; Liu, Fei; Xue, Dongfeng

2015-10-07

There are many practical challenges in the use of graphene materials as active components in electrochemical energy storage devices. Graphene has a much lower capacitance than the theoretical capacitance of 550 F g(-1) for supercapacitors and 744 mA h g(-1) for lithium ion batteries. The macroporous nature of graphene limits its volumetric energy density and the low packing density of graphene-based electrodes prevents its use in commercial applications. Increases in the capacity, energy density and power density of electroactive graphene materials are strongly dependent on their microstructural properties, such as the number of defects, stacking, the use of composite materials, conductivity, the specific surface area and the packing density. The structural design of graphene electrode materials is achieved via six main strategies: the design of non-stacking and three-dimensional graphene; the synthesis of highly packed graphene; the production of graphene with a high specific surface area and high conductivity; the control of defects; functionalization with O, N, B or P heteroatoms; and the formation of graphene composites. These methodologies of structural design are needed for fast electrical charge storage/transfer and the transport of electrolyte ions (Li(+), H(+), K(+), Na(+)) in graphene electrodes. We critically review state-of-the-art progress in the optimization of the electrochemical performance of graphene-based electrode materials. The structure of graphene needs to be designed to develop novel electrochemical energy storage devices that approach the theoretical charge limit of graphene and to deliver electrical energy rapidly and efficiently.

Cobalt-Doped Nickel Phosphite for High Performance of Electrochemical Energy Storage.

PubMed

Li, Bing; Shi, Yuxin; Huang, Kesheng; Zhao, Mingming; Qiu, Jiaqing; Xue, Huaiguo; Pang, Huan

2018-03-01

Compared to single metallic Ni or Co phosphides, bimetallic Ni-Co phosphides own ameliorative properties, such as high electrical conductivity, remarkable rate capability, upper specific capacity, and excellent cycle performance. Here, a simple one-step solvothermal process is proposed for the synthesis of bouquet-like cobalt-doped nickel phosphite (Ni 11 (HPO 3 ) 8 (OH) 6 ), and the effect of the structure on the pseudocapacitive performance is investigated via a series of electrochemical measurements. It is found that when the cobalt content is low, the glycol/deionized water ratio is 1, and the reaction is under 200 °C for 20 h, the morphology of the sample is uniform and has the highest specific surface area. The cobalt-doped Ni 11 (HPO 3 ) 8 (OH) 6 electrode presents a maximum specific capacitance of 714.8 F g -1 . More significantly, aqueous and solid-state flexible electrochemical energy storage devices are successfully assembled. The aqueous device shows a high energy density of 15.48 mWh cm -2 at the power density of 0.6 KW cm -2 . The solid-state device shows a high energy density of 14.72 mWh cm -2 at the power density of 0.6 KW cm -2 . These excellent performances confirm that the cobalt-doped Ni 11 (HPO 3 ) 8 (OH) 6 are promising materials for applications in electrochemical energy storage devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Electrodeposited nickel-cobalt sulfide nanosheet on polyacrylonitrile nanofibers: a binder-free electrode for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Kamran Sami, Syed; Siddiqui, Saqib; Tajmeel Feroze, Muhammad; Chung, Chan-Hwa

2017-11-01

To pursue high-performance energy storage devices with both high energy density and power density, one-dimensional (1D) nanostructures play a key role in the development of functional devices including energy conversion, energy storage, and environmental devices. The polyacrylonitrile (PAN) nanofibers were obtained by the versatile electrospinning method. An ultra-thin nickel-cobalt sulfide (NiCoS) layer was conformably electrodeposited on a self-standing PAN nanofibers by cyclic voltammetry to fabricate the light-weighted porous electrodes for supercapacitors. The porous web of PAN nanofibers acts as a high-surface-area scaffold with significant electrochemical performance, while the electrodeposition of metal sulfide nanosheet further enhances the specific capacitance. The fabricated NiCoS on PAN (NiCoS/PAN) nanofibers exhibits a very high capacitance of 1513 F g-1 at 5 A g-1 in 1 M potassium chloride (KCl) aqueous electrolyte with superior rate capability and excellent electrochemical stability as a hybrid electrode. The high capacitance of the NiCoS is attributed to the large surface area of the electrospun PAN nanofibers scaffold, which has offered a large number of active sites for possible redox reaction of ultra-thin NiCoS layer. Benefiting from the compositional features and electrode architectures, the hybrid electrode of NiCoS/PAN nanofibers shows greatly improved electrochemical performance with an ultra-high capacitance (1124 F g-1 at 50 A g-1). Moreover, a binder-free asymmetric supercapacitor device is also fabricated by using NiCoS/PAN nanofibers as the positive electrode and activated carbon (MSP-20) on PAN nanofibers as the negative electrode; this demonstrates high energy density of 56.904 W h kg-1 at a power density of 1.445 kW kg-1, and it still delivers the energy density of 33.3923 W h kg-1 even at higher power density of 16.5013 kW kg-1.

In Situ Growth of Free-Standing All Metal Oxide Asymmetric Supercapacitor.

PubMed

Yin, Bo-Si; Wang, Zhen-Bo; Zhang, Si-Wen; Liu, Chang; Ren, Qing-Qing; Ke, Ke

2016-10-05

Metal oxides have attracted renewed interest in applications as energy storage and conversion devices. Here, a new design is reported to acquire an asymmetric supercapacitor assembled by all free-standing metal oxides. The positive electrode is made of 3D NiO open porous nanoribbons network on nickel foam and the negative electrode is composed of SnO 2 /MnO 2 nanoflakes grown on carbon cloth (CC) substrate. The combination of two metal oxide electrodes which replaced the traditional group of carbon materials together with metal oxide has achieved a higher energy density. The self-supported 3D NiO nanoribbons network demonstrates a high specific capacitance and better cycle performance without obvious mechanical deformation despite of undergoing harsh bulk redox reactions. The SnO 2 /MnO 2 nanoflakes as the pseudocapacitive electrode exhibit a wide range of voltage window (-1 to 1 V), which is conducive to electrochemical energy storage. The (CC/SnO 2 /MnO 2 )(-)//(NiO/Ni foam)(+) asymmetric supercapacitor device delivers an energy density of 64.4 Wh kg -1 (at a power density of 250 W kg -1 ) and two devices in series are applied to light up 24 red LEDs for about 60 s. The outstanding electrochemical properties of the device hold great promise for long-life, high-energy, and high-power energy storage/conversion applications.

A Nonaqueous Potassium-Based Battery-Supercapacitor Hybrid Device.

PubMed

Fan, Ling; Lin, Kairui; Wang, Jue; Ma, Ruifang; Lu, Bingan

2018-05-01

A low cost nonaqueous potassium-based battery-supercapacitor hybrid device (BSH) is successfully established for the first time with soft carbon as the anode, commercialized activated carbon as the cathode, and potassium bis(fluoro-slufonyl)imide in dimethyl ether as the electrolyte. This BSH reconciles the advantages of potassium ion batteries and supercapacitors, achieving a high energy density of 120 W h kg -1 , a high power density of 599 W kg -1 , a long cycle life of 1500 cycles, and an ultrafast charge/slow discharge performance (energy density and power density are calculated based on the total mass of active materials in the anode and cathode). This work demonstrates a great potential of applying the nonaqueous BSH for low cost electric energy storage systems. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Device for plasma confinement and heating by high currents and nonclassical plasma transport properties

DOEpatents

Coppi, B.; Montgomery, D.B.

1973-12-11

A toroidal plasma containment device having means for inducing high total plasma currents and current densities and at the same time emhanced plasma heating, strong magnetic confinement, high energy density containment, magnetic modulation, microwaveinduced heating, and diagnostic accessibility is described. (Official Gazette)

Towards ultrahigh volumetric capacitance: graphene derived highly dense but porous carbons for supercapacitors

PubMed Central

Tao, Ying; Xie, Xiaoying; Lv, Wei; Tang, Dai-Ming; Kong, Debin; Huang, Zhenghong; Nishihara, Hirotomo; Ishii, Takafumi; Li, Baohua; Golberg, Dmitri; Kang, Feiyu; Kyotani, Takashi; Yang, Quan-Hong

2013-01-01

A small volumetric capacitance resulting from a low packing density is one of the major limitations for novel nanocarbons finding real applications in commercial electrochemical energy storage devices. Here we report a carbon with a density of 1.58 g cm−3, 70% of the density of graphite, constructed of compactly interlinked graphene nanosheets, which is produced by an evaporation-induced drying of a graphene hydrogel. Such a carbon balances two seemingly incompatible characteristics: a porous microstructure and a high density, and therefore has a volumetric capacitance for electrochemical capacitors (ECs) up to 376 F cm−3, which is the highest value so far reported for carbon materials in an aqueous electrolyte. More promising, the carbon is conductive and moldable, and thus could be used directly as a well-shaped electrode sheet for the assembly of a supercapacitor device free of any additives, resulting in device-level high energy density ECs. PMID:24131954

Designing Carbon Based Supercapacitors with High Energy Density: A Summary of Recent Progress.

PubMed

Han, Yi; Lai, Zhengzhe; Wang, Zifan; Yu, Minghao; Tong, Yexiang; Lu, Xihong

2018-05-23

Carbon based supercapacitors (CSCs), with high output power and long lifespan, are considered as promising power sources for modern electronic devices. The rush to find new approaches for optimizing their electrochemical behaviors is still vibrant, and particularly, widespread enthusiasm was focused on improving the energy density of CSCs through improving the specific capacitance and expanding the operating voltage. In this regard, this article provides a brief review about recent progress and new understanding about the assembly of CSCs with high energy density. Novel applied strategies were highlighted and discussed from the aspects of electrolyte, electrodes, and device modulation. Dynamic and mechanism factors associated with the energy storage process of CSCs are particularly emphasized. Finally, the opportunities and challenges are elaborated in the hope of guiding the promising direction for the design of high-energy CSCs. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Transparent, flexible, and high-performance supercapacitor based on ultrafine nickel cobaltite nanospheres

NASA Astrophysics Data System (ADS)

Liu, Xinyue; Wang, Jianxing; Yang, Guowei

2017-07-01

There has been growing interest in transparent and flexible electronic devices such as wrist watch, cell phone, and so on. These devices need the power sources which also have transparent and flexible features. Here, we demonstrate a transparent and flexible energy storage device with outstanding electrochemical performance, high energy density, and super-long life based on ultrafine NiCo2O4 nanospheres which are synthesized by an innovative method concerning laser ablation in liquid and hydrothermal process. The ultrafine NiCo2O4 nanospheres provide high electrochemical activity and the synthesized colloidal solution is suitable for transparent devices. The transparent and flexible device shows a high specific capacitance of 299.7 F/g at the scan rate of 1 mV/s and a long cycling life of 90.4% retention rate after 10,000 cycles at a scan rate of 10 mV/s, which is superior to that of previously reported transparent and flexible energy storage device. In addition, an optical transmittance up to 55% at the wavelength of 550 nm is obtained, and the bending test shows that the bending angle makes no difference to the specific capacitance of the device. In addition, it shows an outstanding energy density of 10.41 Wh/kg. The integrated electrochemical performances of the device are good based on NiCo2O4 nanospheres. These findings make the ultrafine NiCo2O4 nanospheres being promising electrode materials for transparent and flexible energy storage devices.

Design optimization of PVDF-based piezoelectric energy harvesters.

PubMed

Song, Jundong; Zhao, Guanxing; Li, Bo; Wang, Jin

2017-09-01

Energy harvesting is a promising technology that powers the electronic devices via scavenging the ambient energy. Piezoelectric energy harvesters have attracted considerable interest for their high conversion efficiency and easy fabrication in minimized sensors and transducers. To improve the output capability of energy harvesters, properties of piezoelectric materials is an influential factor, but the potential of the material is less likely to be fully exploited without an optimized configuration. In this paper, an optimization strategy for PVDF-based cantilever-type energy harvesters is proposed to achieve the highest output power density with the given frequency and acceleration of the vibration source. It is shown that the maximum power output density only depends on the maximum allowable stress of the beam and the working frequency of the device, and these two factors can be obtained by adjusting the geometry of piezoelectric layers. The strategy is validated by coupled finite-element-circuit simulation and a practical device. The fabricated device within a volume of 13.1 mm 3 shows an output power of 112.8 μW which is comparable to that of the best-performing piezoceramic-based energy harvesters within the similar volume reported so far.

3D direct writing fabrication of electrodes for electrochemical storage devices

NASA Astrophysics Data System (ADS)

Wei, Min; Zhang, Feng; Wang, Wei; Alexandridis, Paschalis; Zhou, Chi; Wu, Gang

2017-06-01

Among different printing techniques, direct ink writing is commonly used to fabricate 3D battery and supercapacitor electrodes. The major advantages of using the direct ink writing include effectively building 3D structure for energy storage devices and providing higher power density and higher energy density than traditional techniques due to the increased surface area of electrode. Nevertheless, direct ink writing has high standards for the printing inks, which requires high viscosity, high yield stress under shear and compression, and well-controlled viscoelasticity. Recently, a number of 3D-printed energy storage devices have been reported, and it is very important to understand the printing process and the ink preparation process for further material design and technology development. We discussed current progress of direct ink writing technologies by using various electrode materials including carbon nanotube-based material, graphene-based material, LTO (Li4Ti5O12), LFP (LiFePO4), LiMn1-xFexPO4, and Zn-based metallic oxide. Based on achieve electrochemical performance, these 3D-printed devices deliver performance comparable to the energy storage device fabricated using traditional methods still leaving large room for further improvement. Finally, perspectives are provided on the potential future direction of 3D printing for all solid-state electrochemical energy storage devices.

Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films

NASA Astrophysics Data System (ADS)

Pandya, Shishir; Wilbur, Joshua; Kim, Jieun; Gao, Ran; Dasgupta, Arvind; Dames, Chris; Martin, Lane W.

2018-05-01

The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3. Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m-2 K-1) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm-3, 526 W cm-3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.

Pyroelectric energy conversion with large energy and power density in relaxor ferroelectric thin films.

PubMed

Pandya, Shishir; Wilbur, Joshua; Kim, Jieun; Gao, Ran; Dasgupta, Arvind; Dames, Chris; Martin, Lane W

2018-05-01

The need for efficient energy utilization is driving research into ways to harvest ubiquitous waste heat. Here, we explore pyroelectric energy conversion from low-grade thermal sources that exploits strong field- and temperature-induced polarization susceptibilities in the relaxor ferroelectric 0.68Pb(Mg 1/3 Nb 2/3 )O 3 -0.32PbTiO 3 . Electric-field-driven enhancement of the pyroelectric response (as large as -550 μC m -2  K -1 ) and suppression of the dielectric response (by 72%) yield substantial figures of merit for pyroelectric energy conversion. Field- and temperature-dependent pyroelectric measurements highlight the role of polarization rotation and field-induced polarization in mediating these effects. Solid-state, thin-film devices that convert low-grade heat into electrical energy are demonstrated using pyroelectric Ericsson cycles, and optimized to yield maximum energy density, power density and efficiency of 1.06 J cm -3 , 526 W cm -3 and 19% of Carnot, respectively; the highest values reported to date and equivalent to the performance of a thermoelectric with an effective ZT ≈ 1.16 for a temperature change of 10 K. Our findings suggest that pyroelectric devices may be competitive with thermoelectric devices for low-grade thermal harvesting.

Laser and acoustic lens for lithotripsy

DOEpatents

Visuri, Steven R.; Makarewicz, Anthony J.; London, Richard A.; Benett, William J.; Krulevitch, Peter; Da Silva, Luiz B.

2002-01-01

An acoustic focusing device whose acoustic waves are generated by laser radiation through an optical fiber. The acoustic energy is capable of efficient destruction of renal and biliary calculi and deliverable to the site of the calculi via an endoscopic procedure. The device includes a transducer tip attached to the distal end of an optical fiber through which laser energy is directed. The transducer tip encapsulates an exogenous absorbing dye. Under proper irradiation conditions (high absorbed energy density, short pulse duration) a stress wave is produced via thermoelastic expansion of the absorber for the destruction of the calculi. The transducer tip can be configured into an acoustic lens such that the transmitted acoustic wave is shaped or focused. Also, compressive stress waves can be reflected off a high density/low density interface to invert the compressive wave into a tensile stress wave, and tensile stresses may be more effective in some instances in disrupting material as most materials are weaker in tension than compression. Estimations indicate that stress amplitudes provided by this device can be magnified more than 100 times, greatly improving the efficiency of optical energy for targeted material destruction.

On the configuration of supercapacitors for maximizing electrochemical performance.

PubMed

Zhang, Jintao; Zhao, X S

2012-05-01

Supercapacitors, which are attracting rapidly growing interest from both academia and industry, are important energy-storage devices for acquiring sustainable energy. Recent years have seen a number of significant breakthroughs in the research and development of supercapacitors. The emergence of innovative electrode materials (e.g., graphene) has clearly provided great opportunities for advancing the science in the field of electrochemical energy storage. Conversely, smart configurations of electrode materials and new designs of supercapacitor devices have, in many cases, boosted the electrochemical performance of the materials. We attempt to summarize recent research progress towards the design and configuration of electrode materials to maximize supercapacitor performance in terms of energy density, power density, and cycle stability. With a brief description of the structure, energy-storage mechanism, and electrode configuration of supercapacitor devices, the design and configuration of symmetric supercapacitors are discussed, followed by that of asymmetric and hybrid supercapacitors. Emphasis is placed on the rational design and configuration of supercapacitor electrodes to maximize the electrochemical performance of the device. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Integrated spectral photocurrent density and reproducibility analyses of excitonic ZnO/NiO heterojunction.

PubMed

Patel, Malkeshkumar; Kim, Joondong

2017-12-01

In this data article, the excitonic ZnO/NiO heterojunction device (Patel et al., 2017) [1] was measured for the integrated photocurrent density and reproducibility. Photograph of the prepared devices of ZnO/NiO on the FTO/glass is presented. Integrated photocurrent density as a function of photon energy from the sunlight is presented. Quantum efficiency measurement system (McScienceK3100, Korea) compliance with International Measurement System was employed to measure ZnO/NIO devices. These data are shown for the 300-440 nm of segment of the sunlight (AM1.5G, http://rredc.nrel.gov/solar/spectra/am1.5/). Reproducibility measure of ZnO/NiO device was presented for nine devices with the estimated device performance parameters including the open circuit voltage, short circuit current density, fill factor and power conversion efficiency.

Hierarchically porous Li3VO4/C nanocomposite as an advanced anode material for high-performance lithium-ion capacitors

NASA Astrophysics Data System (ADS)

Xu, Xuena; Niu, Feier; Zhang, Dapeng; Chu, Chenxiao; Wang, Chunsheng; Yang, Jian; Qian, Yitai

2018-04-01

Lithium-ion capacitors, as a hybrid electrochemical energy storage device, realize high specific energy and power density within one device, thus attracting extensive attention. Here, hierarchically porous Li3VO4/C nanocomposite is prepared by a solvo-thermal reaction, followed with a post-annealing process. This composite has macropores at the center and mesopores in the wall, thus effectively promoting electrolyte penetration and structure stability upon cycling simultaneously. Compared to mesoporous Li3VO4, the enhanced rate capability and specific capacity of hierarchically porous Li3VO4/C indicate the synergistic effect of mesopores and macropores. Inspired by these results, this composite is coupled with mesoporous carbon (CMK-3) for lithium-ion capacitors, generating a specific energy density of 105 Wh kg-1 at a power density of 188 W kg-1. Even if the power density increases to 9.3 kW kg-1, the energy density still remains 62 Wh kg-1. All these results demonstrate the promising potential of hierarchically porous Li3VO4 in lithium ion capacitors.

An Asymmetric Supercapacitor with Both Ultra-High Gravimetric and Volumetric Energy Density Based on 3D Ni(OH)2/MnO2@Carbon Nanotube and Activated Polyaniline-Derived Carbon.

PubMed

Shen, Juanjuan; Li, Xiaocheng; Wan, Liu; Liang, Kun; Tay, Beng Kang; Kong, Lingbin; Yan, Xingbin

2017-01-11

Development of a supercapacitor device with both high gravimetric and volumetric energy density is one of the most important requirements for their practical application in energy storage/conversion systems. Currently, improvement of the gravimetric/volumetric energy density of a supercapacitor is restricted by the insufficient utilization of positive materials at high loading density and the inferior capacitive behavior of negative electrodes. To solve these problems, we elaborately designed and prepared a 3D core-shell structured Ni(OH) 2 /MnO 2 @carbon nanotube (CNT) composite via a facile solvothermal process by using the thermal chemical vapor deposition grown-CNTs as support. Owing to the superiorities of core-shell architecture in improving the service efficiency of pseudocapacitive materials at high loading density, the prepared Ni(OH) 2 /MnO 2 @CNT electrode demonstrated a high capacitance value of 2648 F g -1 (1 A g -1 ) at a high loading density of 6.52 mg cm -2 . Coupled with high-performance activated polyaniline-derived carbon (APDC, 400 F g -1 at 1 A g -1 ), the assembled Ni(OH) 2 /MnO 2 @CNT//APDC asymmetric device delivered both high gravimetric and volumetric energy density (126.4 Wh kg -1 and 10.9 mWh cm -3 , respectively), together with superb rate performance and cycling lifetime. Moreover, we demonstrate an effective approach for building a high-performance supercapacitor with high gravimetric/volumetric energy density.

Solid-State Thin-Film Supercapacitors with Ultrafast Charge/Discharge Based on N-Doped-Carbon-Tubes/Au-Nanoparticles-Doped-MnO2 Nanocomposites.

PubMed

Lv, Qiying; Wang, Shang; Sun, Hongyu; Luo, Jun; Xiao, Jian; Xiao, JunWu; Xiao, Fei; Wang, Shuai

2016-01-13

Although carbonaceous materials possess long cycle stability and high power density, their low-energy density greatly limits their applications. On the contrary, metal oxides are promising pseudocapacitive electrode materials for supercapacitors due to their high-energy density. Nevertheless, poor electrical conductivity of metal oxides constitutes a primary challenge that significantly limits their energy storage capacity. Here, an advanced integrated electrode for high-performance pseudocapacitors has been designed by growing N-doped-carbon-tubes/Au-nanoparticles-doped-MnO2 (NCTs/ANPDM) nanocomposite on carbon fabric. The excellent electrical conductivity and well-ordered tunnels of NCTs together with Au nanoparticles of the electrode cause low internal resistance, good ionic contact, and thus enhance redox reactions for high specific capacitance of pure MnO2 in aqueous electrolyte, even at high scan rates. A prototype solid-state thin-film symmetric supercapacitor (SSC) device based on NCTs/ANPDM exhibits large energy density (51 Wh/kg) and superior cycling performance (93% after 5000 cycles). In addition, the asymmetric supercapacitor (ASC) device assembled from NCTs/ANPDM and Fe2O3 nanorods demonstrates ultrafast charge/discharge (10 V/s), which is among the best reported for solid-state thin-film supercapacitors with both electrodes made of metal oxide electroactive materials. Moreover, its superior charge/discharge behavior is comparable to electrical double layer type supercapacitors. The ASC device also shows superior cycling performance (97% after 5000 cycles). The NCTs/ANPDM nanomaterial demonstrates great potential as a power source for energy storage devices.

Solid-State High Performance Flexible Supercapacitors Based on Polypyrrole-MnO2-Carbon Fiber Hybrid Structure

PubMed Central

Tao, Jiayou; Liu, Nishuang; Ma, Wenzhen; Ding, Longwei; Li, Luying; Su, Jun; Gao, Yihua

2013-01-01

A solid-state flexible supercapacitor (SC) based on organic-inorganic composite structure was fabricated through an “in situ growth for conductive wrapping” and an electrode material of polypyrrole (PPy)-MnO2 nanoflakes-carbon fiber (CF) hybrid structure was obtained. The conductive organic material of PPy greatly improved the electrochemical performance of the device. With a high specific capacitance of 69.3 F cm−3 at a discharge current density of 0.1 A cm−3 and an energy density of 6.16 × 10−3 Wh cm−3 at a power density of 0.04 W cm−3, the device can drive a commercial liquid crystal display (LCD) after being charged. The organic-inorganic composite active materials have enormous potential in energy management and the “in situ growth for conductive wrapping” method might be generalized to open up new strategies for designing next-generation energy storage devices. PMID:23884478

Hierarchical Pore-Patterned Carbon Electrodes for High-Volumetric Energy Density Micro-Supercapacitors.

PubMed

Kim, Cheolho; Moon, Jun Hyuk

2018-06-13

Micro-supercapacitors (MSCs) are attractive for applications in next-generation mobile and wearable devices and have the potential to complement or even replace lithium batteries. However, many previous MSCs have often exhibited a low volumetric energy density with high-loading electrodes because of the nonuniform pore structure of the electrodes. To address this issue, we introduced a uniform-pore carbon electrode fabricated by 3D interference lithography. Furthermore, a hierarchical pore-patterned carbon (hPC) electrode was formed by introducing a micropore by chemical etching into the macropore carbon skeleton. The hPC electrodes were applied to solid-state MSCs. We achieved a constant volumetric capacitance and a corresponding volumetric energy density for electrodes of various thicknesses. The hPC MSC reached a volumetric energy density of approximately 1.43 mW h/cm 3 . The power density of the hPC MSC was 1.69 W/cm 3 . We could control the capacitance and voltage additionally by connecting the unit MSC cells in series or parallel, and we confirmed the operation of a light-emitting diode. We believe that our pore-patterned electrodes will provide a new platform for compact but high-performance energy storage devices.

Ultrahigh Energy Density in SrTiO3 Film Capacitors.

PubMed

Hou, Chuangming; Huang, Weichuan; Zhao, Wenbo; Zhang, Dalong; Yin, Yuewei; Li, Xiaoguang

2017-06-21

Solid-state dielectric film capacitors with high-energy-storage density will further promote advanced electronic devices and electrical power systems toward miniaturization, lightweight, and integration. In this study, the influence of interface and thickness on energy storage properties of SrTiO 3 (STO) films grown on La 0.67 Sr 0.33 MnO 3 (LSMO) electrode are systematically studied. The cross-sectional high resolution transmission electron microscopy reveals an ion interdiffusion layer and oxygen vacancies at the STO/LSMO interface. The capacitors show good frequency stability and increased dielectric constant with increasing STO thickness (410-710 nm). The breakdown strength (E b ) increases with decreasing STO thickness and reaches 6.8 MV/cm. Interestingly, the E b under positive field is enhanced significantly and an ultrahigh energy density up to 307 J/cm 3 with a high efficiency of 89% is realized. The enhanced E b may be related to the modulation of local electric field and redistribution of oxygen vacancies at the STO/LSMO interface. Our results should be helpful for potential strategies to design devices with ultrahigh energy density.

APPARATUS FOR THE DENSIFICATION AND ENERGIZATION OF CHARGED PARTICLES

DOEpatents

Post, R.F.; Coensgen, F.H.

1962-12-18

This patent relates to a device for materially increasing the energy and density of a plasma to produce conditions commensurate with the establishment and promotion of controlled thermonuclear reactions. To this end the device employs three successive stages of magnetic compression, each stage having magnetic mirrors to compress a plasma, the mirrors being moveable to transfer the plasma to successive stages for further compression. Accordingly, a plasma introduced to the first stage is increased in density and energy in stepwide fashion by virtue of the magnetic compression in the successive stages such that the plasma upon reaching the last stage is of extremely high energy and density commensurate the plasma particles undergoing thermonuclear reactions. The principal novelty of the device resides in the provision of a unidirectional magnetic field which increases in stepwise fashion in coaxially communicating compression chambers of progressively decreasing lengths and diameters. Pulsed magnetic fields are superimposed upon the undirectional field and are manipulated to establish resultant magnetic compression fields which increase in intensity and progressively move, with respect to time, through the compression chambers in the direction of the smallest one thereof. The resultant field in the last compression chamber is hence of relatively high intensity, and the density and energy of the plasma confined therein are correspondingly high. (AEC)

Recoverable Wire-Shaped Supercapacitors with Ultrahigh Volumetric Energy Density for Multifunctional Portable and Wearable Electronics.

PubMed

Shi, Minjie; Yang, Cheng; Song, Xuefeng; Liu, Jing; Zhao, Liping; Zhang, Peng; Gao, Lian

2017-05-24

Wire-shaped supercapacitors (SCs) based on shape memory materials are of considerable interest for next-generation portable and wearable electronics. However, the bottleneck in this field is how to develop the devices with excellent electrochemical performance while well-maintaining recoverability and flexibility. Herein, a unique asymmetric electrode concept is put forward to fabricate smart wire-shaped SCs with ultrahigh energy density, which is realized by using porous carbon dodecahedra coated on NiTi alloy wire and flexible graphene fiber as yarn electrodes. Notably, the wire-shaped SCs not only exhibit high flexibility that can be readily woven into real clothing but also represent the available recoverable ability. When irreversible plastic deformations happen, the deformed shape of the devices can automatically resume the initial predesigned shape in a warm environment (about 35 °C). More importantly, the wire-shaped SCs act as efficient energy storage devices, which display high volumetric energy density (8.9 mWh/cm 3 ), volumetric power density (1080 mW/cm 3 ), strong durability in multiple mechanical states, and steady electrochemical behavior after repeated shape recovery processes. Considering their relative facile fabrication technology and excellent electrochemical performance, this asymmetric electrode strategy produced smart wire-shaped supercapacitors desirable for multifunctional portable and wearable electronics.

Ignitor with stable low-energy thermite igniting system

DOEpatents

Kelly, Michael D.; Munger, Alan C.

1991-02-05

A stable compact low-energy igniting system in an ignitor utilizes two components, an initiating charge and an output charge. The initiating charge is a thermite in ultra-fine powder form compacted to 50-70% of theoretical maximum density and disposed in a cavity of a header of the ignitor adjacent to an electrical ignition device, or bridgewire, mounted in the header cavity. The initiating charge is ignitable by operation of the ignition device in a hot-wire mode. The output charge is a thermite in high-density consoladated form compacted to 90-99% of theoretical maximum density and disposed adjacent to the initiating charge on an opposite end thereof from the electrical ignition device and ignitable by the initiating charge. A sleeve is provided for mounting the output charge to the ignitor header with the initiating charge confined therebetween in the cavity.

Flexible Hybrid Battery/Pseudocapacitor

NASA Technical Reports Server (NTRS)

Tucker, Dennis S.; Paley, Steven

2015-01-01

Batteries keep devices working by utilizing high energy density, however, they can run down and take tens of minutes to hours to recharge. For rapid power delivery and recharging, high-power density devices, i.e., supercapacitors, are used. The electrochemical processes which occur in batteries and supercapacitors give rise to different charge-storage properties. In lithium ion (Li+) batteries, the insertion of Li+, which enables redox reactions in bulk electrode materials, is diffusion controlled and can be slow. Supercapacitor devices, also known as electrical double-layer capacitors (EDLCs) store charge by adsorption of electrolyte ions onto the surface of electrode materials. No redox reactions are necessary, so the response to changes in potential without diffusion limitations is rapid and leads to high power. However, the charge in EDLCs is confined to the surface, so the energy density is lower than that of batteries.

Self-assembling graphene-anthraquinone-2-sulphonate supramolecular nanostructures with enhanced energy density for supercapacitors

NASA Astrophysics Data System (ADS)

Gao, Lifang; Gan, Shiyu; Li, Hongyan; Han, Dongxue; Li, Fenghua; Bao, Yu; Niu, Li

2017-07-01

Boosting the energy density of capacitive energy storage devices remains a crucial issue for facilitating applications. Herein, we report a graphene-anthraquinone supramolecular nanostructure by self-assembly for supercapacitors. The sulfonated anthraquinone exhibits high water solubility, a π-conjugated structure and redox active features, which not only serve as a spacer to interact with and stabilize graphene but also introduce extra pseudocapacitance contributions. The formed nest-like three-dimensional (3D) nanostructure with further hydrothermal treatment enhances the accessibility of ion transfer and exposes the redox-active quinone groups in the electrolytes. A fabricated all-solid-state flexible symmetric device delivers a high specific capacitance of 398.5 F g-1 at 1 A g-1 (1.5 times higher than graphene), superior energy density (52.24 Wh kg-1 at about 1 kW kg-1) and good stability (82% capacitance retention after 10 000 cycles).

Energy density and rate limitations in structural composite supercapacitors

NASA Astrophysics Data System (ADS)

Snyder, J. F.; Gienger, E.; Wetzel, E. D.; Xu, K.

2012-06-01

The weight and volume of conventional energy storage technologies greatly limits their performance in mobile platforms. Traditional research efforts target improvements in energy density to reduce device size and mass. Enabling a device to perform additional functions, such as bearing mechanical load, is an alternative approach as long as the total mass efficiency exceeds that of the individual materials it replaces. Our research focuses on structural composites that function as batteries and supercapacitors. These multifunctional devices could be used to replace conventional structural components, such as vehicle frame elements, to provide significant system-level weight reductions and extend mission times. Our approach is to design structural properties directly into the electrolyte and electrode materials. Solid polymer electrolyte materials bind the system and transfer load to the fibers while conducting ions between the electrodes. Carbon fiber electrodes provide a route towards optimizing both energy storage and load-bearing capabilities, and may also obviate the need for a separate current collector. The components are being integrated using scalable, cost-effective composite processing techniques that are amenable to complex part shapes. Practical considerations of energy density and rate behavior are described here as they relate to materials used. Our results highlight the viability as well as the challenges of this multifunctional approach towards energy storage.

Measurements of Plasma Density in a Fast and Compact Plasma Focus Operating at Hundreds of Joules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pavez, Cristian; Universidad de Concepcion, Facultad de Ciencias, Departamento de Fisica, Concepcion; Silva, Patricio

2006-12-04

It is known that there are plasma parameters that remain relatively constant for plasma focus facilities operating in a wide range of de energy, from 1kJ to 1MJ, such as: electron density, temperature and plasma energy density. Particularly the electron density is of the order of 1025m-3. Recently the experimental studies in plasma focus has been extended to devices operating under 1kJ, in the range of hundreds and tens of joules. In this work an optical refractive system was implemented in order to measure the electron density in a plasma focus devices of hundred of joules, PF-400J (880 nF, 30more » kV, 120 kA, 400 J, 300 ns time to peak current, dI/dt{approx}4x1011 A/s. The plasma discharge was synchronized with a pulsed Nd-YAG laser ({approx}6ns FWHM at 532nm) in order to obtain optical diagnostics as interferometry and Schlieren. An electron density of (0.9{+-}0.25)x1025m-3 was obtained at the axis of the plasma column close to the pinch time. This value is of the same order that the obtained in devices oparating in the energy range of 1kJ to 1MJ.« less

Materials for electrochemical capacitors

NASA Astrophysics Data System (ADS)

Simon, Patrice; Gogotsi, Yury

2008-11-01

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

Materials for electrochemical capacitors.

PubMed

Simon, Patrice; Gogotsi, Yury

2008-11-01

Electrochemical capacitors, also called supercapacitors, store energy using either ion adsorption (electrochemical double layer capacitors) or fast surface redox reactions (pseudo-capacitors). They can complement or replace batteries in electrical energy storage and harvesting applications, when high power delivery or uptake is needed. A notable improvement in performance has been achieved through recent advances in understanding charge storage mechanisms and the development of advanced nanostructured materials. The discovery that ion desolvation occurs in pores smaller than the solvated ions has led to higher capacitance for electrochemical double layer capacitors using carbon electrodes with subnanometre pores, and opened the door to designing high-energy density devices using a variety of electrolytes. Combination of pseudo-capacitive nanomaterials, including oxides, nitrides and polymers, with the latest generation of nanostructured lithium electrodes has brought the energy density of electrochemical capacitors closer to that of batteries. The use of carbon nanotubes has further advanced micro-electrochemical capacitors, enabling flexible and adaptable devices to be made. Mathematical modelling and simulation will be the key to success in designing tomorrow's high-energy and high-power devices.

Hybrid Power Management Program Evaluated Fuel Cell/Ultracapacitor Combinations and Developed Other New Applications

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2004-01-01

In fiscal year 2003, the continuation of the Hybrid Power Management (HPM) Program through NASA Glenn Research Center's Commercial Technology Office resulted in several new successful applications of this pioneering technology. HPM is the innovative integration of diverse, state-of-the-art power devices in an optimal configuration for space and terrestrial applications. The appropriate application and control of the various power devices significantly improves overall system performance and efficiency. The advanced power devices include ultracapacitors, fuel cells, and photovoltaics. HPM has extremely wide potential, with applications from nanowatts to megawatts--including power generation, transportation systems, biotechnology systems, and space power systems. HPM has the potential to significantly alleviate global energy concerns, improve the environment, and stimulate the economy. Fuel cells provide excellent efficiency and energy density, but do not have good power density. In contrast, ultracapacitors have excellent power density and virtually unlimited cycle life. To improve the power density of the fuel cell, the combination of fuel cells and ultracapacitors was evaluated.

Hierarchical ternary Ni-Co-Se nanowires for high-performance supercapacitor device design.

PubMed

Guo, Kailu; Cui, Shizhong; Hou, Hongwei; Chen, Weihua; Mi, Liwei

2016-12-06

Large-scale uniform Ni-Co-Se bimetallic ternary nanowires have been successfully synthesized through a successive cation exchange. First, NiSe nanowires in situ grown on nickel foam (NF) were prepared by a facile solvothermal route. Next, a series of ternary materials possessing different proportions of Ni and Co were fabricated by a Co-exchange method using the Ni@NiSe material as a template, which effectively achieved morphological inheritance from the parent material. To explore the electrochemical performance, all synthetic materials were assembled into asymmetric supercapacitor devices. Among asymmetric supercapacitor devices, the Ni@Ni 0.8 Co 0.2 Se//active carbon (AC) device exhibited a high specific capacitance of 86 F g -1 at a current density of 1 A g -1 and excellent cycling stability with virtually no decrease in capacitance after 2000 continuous charge-discharge cycles. This device still delivered an energy density of 17 Wh kg -1 even at a high power density of 1526.8 W kg -1 . These superior electrochemical properties of Ni@Ni 0.8 Co 0.2 Se as an electrode material for supercapacitor devices confirmed the synergistic effect between Co and Ni ions, suggesting their potential application in the field of energy storage.

Transition metal sulfides grown on graphene fibers for wearable asymmetric supercapacitors with high volumetric capacitance and high energy density

NASA Astrophysics Data System (ADS)

Cai, Weihua; Lai, Ting; Lai, Jianwei; Xie, Haoting; Ouyang, Liuzhang; Ye, Jianshan; Yu, Chengzhong

2016-06-01

Fiber shaped supercapacitors are promising candidates for wearable electronics because they are flexible and light-weight. However, a critical challenge of the widespread application of these energy storage devices is their low cell voltages and low energy densities, resulting in limited run-time of the electronics. Here, we demonstrate a 1.5 V high cell voltage and high volumetric energy density asymmetric fiber supercapacitor in aqueous electrolyte. The lightweight (0.24 g cm-3), highly conductive (39 S cm-1), and mechanically robust (221 MPa) graphene fibers were firstly fabricated and then coated by NiCo2S4 nanoparticles (GF/NiCo2S4) via the solvothermal deposition method. The GF/NiCo2S4 display high volumetric capacitance up to 388 F cm-3 at 2 mV s-1 in a three-electrode cell and 300 F cm-3 at 175.7 mA cm-3 (568 mF cm-2 at 0.5 mA cm-2) in a two-electrode cell. The electrochemical characterizations show 1000% higher capacitance of the GF/NiCo2S4 as compared to that of neat graphene fibers. The fabricated device achieves high energy density up to 12.3 mWh cm-3 with a maximum power density of 1600 mW cm-3, outperforming the thin-film lithium battery. Therefore, these supercapacitors are promising for the next generation flexible and wearable electronic devices.

Transition metal sulfides grown on graphene fibers for wearable asymmetric supercapacitors with high volumetric capacitance and high energy density

PubMed Central

Cai, Weihua; Lai, Ting; Lai, Jianwei; Xie, Haoting; Ouyang, Liuzhang; Ye, Jianshan; Yu, Chengzhong

2016-01-01

Fiber shaped supercapacitors are promising candidates for wearable electronics because they are flexible and light-weight. However, a critical challenge of the widespread application of these energy storage devices is their low cell voltages and low energy densities, resulting in limited run-time of the electronics. Here, we demonstrate a 1.5 V high cell voltage and high volumetric energy density asymmetric fiber supercapacitor in aqueous electrolyte. The lightweight (0.24 g cm−3), highly conductive (39 S cm−1), and mechanically robust (221 MPa) graphene fibers were firstly fabricated and then coated by NiCo2S4 nanoparticles (GF/NiCo2S4) via the solvothermal deposition method. The GF/NiCo2S4 display high volumetric capacitance up to 388 F cm−3 at 2 mV s−1 in a three-electrode cell and 300 F cm−3 at 175.7 mA cm−3 (568 mF cm−2 at 0.5 mA cm−2) in a two-electrode cell. The electrochemical characterizations show 1000% higher capacitance of the GF/NiCo2S4 as compared to that of neat graphene fibers. The fabricated device achieves high energy density up to 12.3 mWh cm−3 with a maximum power density of 1600 mW cm−3, outperforming the thin-film lithium battery. Therefore, these supercapacitors are promising for the next generation flexible and wearable electronic devices. PMID:27248510

Application of a high-energy-density permanent magnet material in underwater systems

NASA Astrophysics Data System (ADS)

Cho, C. P.; Egan, C.; Krol, W. P.

1996-06-01

This paper addresses the application of high-energy-density permanent magnet (PM) technology to (1) the brushless, axial-field PM motor and (2) the integrated electric motor/pump system for under-water applications. Finite-element analysis and lumped parameter magnetic circuit analysis were used to calculate motor parameters and performance characteristics and to conduct tradeoff studies. Compact, efficient, reliable, and quiet underwater systems are attainable with the development of high-energy-density PM material, power electronic devices, and power integrated-circuit technology.

High energy devices versus low energy devices in orthopedics treatment modalities

NASA Astrophysics Data System (ADS)

Schultheiss, Reiner

2003-10-01

The orthopedic consensus group defined in 1997 the 42 most likely relevant parameters of orthopedic shock wave devices. The idea of this approach was to correlate the different clinical outcomes with the physical properties of the different devices with respect to their acoustical waves. Several changes in the hypothesis of the dose effect relationship have been noticed since the first orthopedic treatments. The relation started with the maximum pressure p+, followed by the total energy, the energy density; and finally the single treatment approach using high, and then the multiple treatment method using low energy. Motivated by the reimbursement situation in Germany some manufacturers began to redefine high and low energy devices independent of the treatment modality. The OssaTron as a high energy, single treatment electro hydraulic device gained FDA approval as the first orthopedic ESWT device for plantar fasciitis and, more recently, for lateral epicondylitis. Two low energy devices have now also gained FDA approval based upon a single treatment. Comparing the acoustic data, differences between the OssaTron and the other devices are obvious and will be elaborated upon. Cluster analysis of the outcomes and the acoustical data are presented and new concepts will be suggested.

Functional Carbon Materials for Electrochemical Energy Storage

NASA Astrophysics Data System (ADS)

Zhou, Huihui

The ability to harvest and convert solar energy has been associated with the evolution of human civilization. The increasing consumption of fossil fuels since the industrial revolution, however, has brought to concerns in ecological deterioration and depletion of the fossil fuels. Facing these challenges, humankind is forced to seek for clean, sustainable and renewable energy resources, such as biofuels, hydraulic power, wind power, geothermal energy and other kinds of alternative energies. However, most alternative energy sources, generally in the form of electrical energy, could not be made available on a continuous basis. It is, therefore, essential to store such energy into chemical energy, which are portable and various applications. In this context, electrochemical energy-storage devices hold great promises towards this goal. The most common electrochemical energy-storage devices are electrochemical capacitors (ECs, also called supercapacitors) and batteries. In comparison to batteries, ECs posses high power density, high efficiency, long cycling life and low cost. ECs commonly utilize carbon as both (symmetric) or one of the electrodes (asymmetric), of which their performance is generally limited by the capacitance of the carbon electrodes. Therefore, developing better carbon materials with high energy density has been emerging as one the most essential challenges in the field. The primary objective of this dissertation is to design and synthesize functional carbon materials with high energy density at both aqueous and organic electrolyte systems. The energy density (E) of ECs are governed by E = CV 2/2, where C is the total capacitance and V is the voltage of the devices. Carbon electrodes with high capacitance and high working voltage should lead to high energy density. In the first part of this thesis, a new class of nanoporous carbons were synthesized for symmetric supercapacitors using aqueous Li2SO4 as the electrolyte. A unique precursor was adopted to create uniformly distributed nanopores with large surface area, leading to high-performance electrodes with high capacitance, excellent rate performance and stable cycling, even under a high working voltage of 1.6V. The second part of this dissertation work further improved the capacitance of the carbon electrodes by fluorine doping. This doping process enhances the affinity of the carbon surface with organic electrolytes, leading to further improved capacitance and energy density. In the third part, carbon materials were synthesized with high surface area, capacitance and working voltage of 4V in organic electrolyte, leading to the construction of prototyped devices with energy density comparable to those of the current lead-acid batteries. Besides the abovementioned research, hierarchical graphitic carbons were also explored for lithium ion batteries and supercapacitors. Overall, through rational design of carbons with optimized pore configuration and surface chemistry, carbon electrodes with improved energy density and rate performance were improved significantly. Collectively, this thesis work systematically unveils simple yet effective strategies to achieve high performance carbon-based supercapacitors with high power density and high energy density, including the following aspects: 1) Constructed electrodes with high capacitance through building favorable ion/electron transportation pathways, tuning pore structure and pore size. 2) Improved the capacitance through enhancing the affinity between the carbon electrodes and electrolytes by doping the carbons with heteroatoms. 3) Explored and understand the roles of heteroatom doping in the capacitive behavior by both experimental measurement and computational modeling. 4) Improved energy density of carbon electrodes by enlarging their working voltage in aqueous and organic electrolyte. 5) Scalable and effective production of hierarchically porous graphite particles through aerosol process for use as the anode materials of lithium ion batteries. These strategies can be extended as a general design platform for other high-performance energy storage materials such as fuel cells and lithium-ion batteries.

Dependence of mobility on shallow localized gap states in single-crystal organic field-effect-transistors

NASA Astrophysics Data System (ADS)

Butko, V. Y.; So, W.; Lang, D. V.; Chi, X.; Lashley, J. C.; Ramirez, A. P.

2009-12-01

In order to optimize the performance of molecular organic electronic devices it is important to study the intermolecular density of states and charge transport mechanisms in the environment of crystalline organic material. Using this approach in Field Effect Transistors (FETs) we show that material purification improves carrier mobility and decreases density of the deep localized electronic state. We also report a general exponential energy dependence of the density of localized states in a vicinity of the mobility edge (Fermi energies up to ∼7 times higher than the thermal energy (kT)) in a variety of the extensively purified molecular organic crystal FETs. This observation and the low activation energy of the order of ∼kT suggest that molecular structural misplacements of the sizes that are comparable with thermal molecular modes rather than impurity deep traps play a role in formation of these shallow states. We find that the charge carrier mobility in the FET nanochannels, μeff, is parameterized by two factors, the free-carrier mobility, μ0, and the ratio of the free carrier density to the total carrier density induced by gate bias. Crystalline FETs fabricated from rubrene, pentacene, and tetracene have a high free-carrier mobility, μ0∼50 cm2/Vs, at 300 K with lower device μeff dominated by localized shallow gap states. This relationship suggests that further improvements in electronic performance could be possible with enhanced device quality.

Roll-to-roll production of spray coated N-doped carbon nanotube electrodes for supercapacitors

NASA Astrophysics Data System (ADS)

Karakaya, Mehmet; Zhu, Jingyi; Raghavendra, Achyut J.; Podila, Ramakrishna; Parler, Samuel G.; Kaplan, James P.; Rao, Apparao M.

2014-12-01

Although carbon nanomaterials are being increasingly used in energy storage, there has been a lack of inexpensive, continuous, and scalable synthesis methods. Here, we present a scalable roll-to-roll (R2R) spray coating process for synthesizing randomly oriented multi-walled carbon nanotubes electrodes on Al foils. The coin and jellyroll type supercapacitors comprised such electrodes yield high power densities (˜700 mW/cm3) and energy densities (1 mW h/cm3) on par with Li-ion thin film batteries. These devices exhibit excellent cycle stability with no loss in performance over more than a thousand cycles. Our cost analysis shows that the R2R spray coating process can produce supercapacitors with 10 times the energy density of conventional activated carbon devices at ˜17% lower cost.

Suppressing the Coffee-Ring Effect in Semitransparent MnO2 Film for a High-Performance Solar-Powered Energy Storage Window.

PubMed

Jin, Huanyu; Qian, Jiasheng; Zhou, Limin; Yuan, Jikang; Huang, Haitao; Wang, Yu; Tang, Wing Man; Chan, Helen Lai Wa

2016-04-13

We introduce a simple and effective method to deposit a highly uniform and semitransparent MnO2 film without coffee-ring effect (CRE) by adding ethanol into MnO2 ink for transparent capacitive energy storage devices. By carefully controlling the amount of ethanol added in the MnO2 droplet, we could significantly reduce the CRE and thus improve the film uniformity. The electrochemical properties of supercapacitor (SC) devices using semitransparent MnO2 film electrodes with or without CRE were measured and compared. The SC device without CRE shows a superior capacitance, high rate capability, and lower contact resistance. The CRE-free device could achieve a considerable volumetric capacitance of 112.2 F cm(-3), resulting in a high volumetric energy density and power density of 10 mWh cm(-3) and 8.6 W cm(-3), respectively. For practical consideration, both flexible SC and large-area rigid SC devices were fabricated to demonstrate their potential for flexible transparent electronic application and capacitive energy-storage window application. Moreover, a solar-powered energy storage window which consists of a commercial solar cell and our studied semitransparent MnO2-film-based SCs was assembled. These SCs could be charged by the solar cell and light up a light emitting diode (LED), demonstrating their potential for self-powered systems and energy-efficient buildings.

Performance testing of supercapacitors: Important issues and uncertainties

NASA Astrophysics Data System (ADS)

Zhao, Jingyuan; Gao, Yinghan; Burke, Andrew F.

2017-09-01

Supercapacitors are a promising technology for high power energy storage, which have been used in some industrial and vehicles applications. Hence, it is important that information concerning the performance of supercapacitors be detailed and reliable so system designers can make rational decisions regarding the selection of the energy storage components. This paper is concerned with important issues and uncertainties regarding the performance testing of supercapacitors. The effect of different test procedures on the measured characteristics of both commercial and prototype supercapacitors including hybrid supercapacitors have been studied. It was found that the test procedure has a relatively minor effect on the capacitance of carbon/carbon devices and a more significant effect on the capacitance of hybrid supercapacitors. The device characteristic with the greatest uncertainty is the resistance and subsequently the claimed power capability of the device. The energy density should be measured by performing constant power discharges between appropriate voltage limits. This is particularly important in the case of hybrid supercapacitors for which the energy density is rate dependent and the simple relationship E = ½CV2 does not yield accurate estimates of the energy stored. In general, most of the important issues for testing carbon/carbon devices become more serious for hybrid supercapacitors.

Series asymmetric supercapacitors based on free-standing inner-connection electrodes for high energy density and high output voltage.

PubMed

Tao, Jiayou; Liu, Nishuang; Rao, Jiangyu; Ding, Longwei; Al Bahrani, Majid Raissan; Li, Luying; Su, Jun; Gao, Yihua

2014-12-21

Asymmetric supercapacitors (ASCs) based on free-standing membranes with high energy density and high output voltage are reported. MnO(2) nanowire/carbon nanotube (CNT) composites and MoO(3) nanobelt/CNT composites are selected as the anode and the cathode materials of the devices, respectively. The ASC has a high volumetric capacitance of 50.2 F cm(-3) at a scan rate of 2 mV s(-1) and a high operation voltage window of 2.0 V. Especially, after a middle layer with an inner-connection structure was inserted between the anode and the cathode, the output voltage of the whole device can achieve 4.0 V. The full cell of series ASCs (SASC) with an inner-connection middle layer has a high energy density of 28.6 mW h cm(-3) at a power density of 261.4 mW cm(-3), and exhibits excellent cycling performance of 99.6% capacitance retention over 10,000 cycles. This strategy of designing the hybridized structure for SASCs provides a promising route for next-generation SCs with high energy density and high output voltage.

Homogeneous/Inhomogeneous-Structured Dielectrics and their Energy-Storage Performances.

PubMed

Yao, Zhonghua; Song, Zhe; Hao, Hua; Yu, Zhiyong; Cao, Minghe; Zhang, Shujun; Lanagan, Michael T; Liu, Hanxing

2017-05-01

The demand for dielectric capacitors with higher energy-storage capability is increasing for power electronic devices due to the rapid development of electronic industry. Existing dielectrics for high-energy-storage capacitors and potential new capacitor technologies are reviewed toward realizing these goals. Various dielectric materials with desirable permittivity and dielectric breakdown strength potentially meeting the device requirements are discussed. However, some significant limitations for current dielectrics can be ascribed to their low permittivity, low breakdown strength, and high hysteresis loss, which will decrease their energy density and efficiency. Thus, the implementation of dielectric materials for high-energy-density applications requires the comprehensive understanding of both the materials design and processing. The optimization of high-energy-storage dielectrics will have far-reaching impacts on the sustainable energy and will be an important research topic in the near future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The impact of hybrid energy storage on power quality, when high power pulsed DC loads are operated on a microgrid testbed

NASA Astrophysics Data System (ADS)

Kelley, Jay Paul

As the Navy's demands for high power transient loads evolves, so too does the need for alternative energy sources to back-up the more traditional power generation. Such applications in need of support include electrical grid backup and directed energy weapon systems such as electromagnetic launchers, laser systems, and high power microwave generators, among others. Among the alternative generation sources receiving considerable attention are energy storage devices such as rechargeable electrochemical batteries and capacitors. In such applications as those mentioned above, these energy storage devices offer the ability to serve a dual role as both a power source to the various loads as well high power loads themselves to the continual generation when the high power transient loads are in periods of downtime. With the recent developments in electrochemical energy storage, lithium-ion batteries (LIBs) seem like the obvious choice, but previous research has shown that the elevated rates of charging can be detrimental to both the cycle life and the operational life span of the device. In order to preserve the batteries, their charge rate must be limited. One proposed method to accomplish the dual role task mentioned above, while preserving the life of the batteries, is by combining high energy density LIBs with high power density electric double layer capacitors (EDLCs) or lithium-ion capacitors (LICs) using controllable power electronics to adjust the flow of power to and from each device. Such a configuration is typically referred to as hybrid energy storage module (HESM). While shipboard generators start up, the combined high energy density and high power density of the HESM provides the capability to source critical loads for an extended period of time at the high rates they demand. Once the generator is operationally efficient, the HESM can act as a high energy reservoir to harvest the energy from the generator while the loads are in short periods of inactivity. This enables the generator to maintain its operation at levels of high efficiency thereby increasing the power quality of the AC bus. The work discussed here is aimed at evaluating how the use of energy storage impacts the power quality on MicroGrid's AC bus when high rate DC and AC loads are sourced simultaneously. Also HESM has been developed and evaluated as a mean to optimizing both the power and energy density of the energy storage installed.

Toward Wearable Self-Charging Power Systems: The Integration of Energy-Harvesting and Storage Devices.

PubMed

Pu, Xiong; Hu, Weiguo; Wang, Zhong Lin

2018-01-01

One major challenge for wearable electronics is that the state-of-the-art batteries are inadequate to provide sufficient energy for long-term operations, leading to inconvenient battery replacement or frequent recharging. Other than the pursuit of high energy density of secondary batteries, an alternative approach recently drawing intensive attention from the research community, is to integrate energy-generation and energy-storage devices into self-charging power systems (SCPSs), so that the scavenged energy can be simultaneously stored for sustainable power supply. This paper reviews recent developments in SCPSs with the integration of various energy-harvesting devices (including piezoelectric nanogenerators, triboelectric nanogenerators, solar cells, and thermoelectric nanogenerators) and energy-storage devices, such as batteries and supercapacitors. SCPSs with multiple energy-harvesting devices are also included. Emphasis is placed on integrated flexible or wearable SCPSs. Remaining challenges and perspectives are also examined to suggest how to bring the appealing SCPSs into practical applications in the near future. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible Asymmetric Supercapacitor Based on Functionalized Reduced Graphene Oxide Aerogels with Wide Working Potential Window.

PubMed

Bora, Anindita; Mohan, Kiranjyoti; Doley, Simanta; Dolui, Swapan Kumar

2018-03-07

Flexible energy storage devices are in great demand since the advent of flexible electronics. Until now, flexible supercapacitors based on graphene analogues usually have had low operating potential windows. To this end, two dissimilar electrode materials with complementary potential ranges are employed to obtain an optimum cell voltage of 1.8 V. A low-temperature organic sol-gel method is used to prepare two different types of functionalized reduced graphene oxide aerogels (rGOA) where Ag nanorod functionalized rGOA acts as a negative electrode while polyaniline nanotube functionalized rGOA acts as a positive electrode. Both materials comprehensively exploit their unique properties to produce a device that has high energy and power densities. An assembled all-solid-state asymmetric supercapacitor gives a high energy density of 52.85 W h kg -1 and power density of 31.5 kW kg -1 with excellent cycling and temperature stability. The device also performs extraordinarily well under different bending conditions, suggesting its potential to meet the requirements for flexible electronics.

Novel Quaternary Chalcogenide/Reduced Graphene Oxide-Based Asymmetric Supercapacitor with High Energy Density.

PubMed

Sarkar, Samrat; Howli, Promita; Das, Biswajit; Das, Nirmalya Sankar; Samanta, Madhupriya; Das, G C; Chattopadhyay, K K

2017-07-12

In this work we have synthesized quaternary chalcogenide Cu 2 NiSnS 4 (QC) nanoparticles grown in situ on 2D reduced graphene oxide (rGO) for application as anode material of solid-state asymmetric supercapacitors (ASCs). Thorough characterization of the synthesized composite validates the proper phase, stoichiometry, and morphology. Detailed electrochemical study of the electrode materials and ASCs has been performed. The as-fabricated device delivers an exceptionally high areal capacitance (655.1 mF cm -2 ), which is much superior to that of commercial micro-supercapacitors. Furthermore, a remarkable volumetric capacitance of 16.38 F cm -3 is obtained at a current density of 5 mA cm -2 combined with a very high energy density of 5.68 mW h cm -3 , which is comparable to that of commercially available lithium thin film batteries. The device retains 89.2% of the initial capacitance after running for 2000 cycles, suggesting its long-term capability. Consequently, the enhanced areal and volumetric capacitances combined with decent cycle stability and impressive energy density endow the uniquely decorated QC/rGO composite material as a promising candidate in the arena of energy storage devices. Moreover, Cu 2 NiSnS 4 being a narrow band gap photovoltaic material, this work offers a novel protocol for the development of self-charging supercapacitors in the days to come.

Solar-microbial hybrid device based on oxygen-deficient niobium pentoxide anodes for sustainable hydrogen production.

PubMed

Li, Mingyang; He, Xinjun; Zeng, Yinxiang; Chen, Meiqiong; Zhang, Ziyang; Yang, Hao; Fang, Pingping; Lu, Xihong; Tong, Yexiang

2015-12-01

Hydrogen gas is emerging as an attractive fuel with high energy density for the direction of energy resources in the future. Designing integrated devices based on a photoelectrochemical (PEC) cell and a microbial fuel cell (MFC) represents a promising strategy to produce hydrogen fuel at a low price. In this work, we demonstrate a new solar-microbial (PEC-MFC) hybrid device based on the oxygen-deficient Nb 2 O 5 nanoporous (Nb 2 O 5- x NPs) anodes for sustainable hydrogen generation without external bias for the first time. Owing to the improved conductivity and porous structure, the as-prepared Nb 2 O 5- x NPs film yields a remarkable photocurrent density of 0.9 mA cm -2 at 0.6 V ( vs. SCE) in 1 M KOH aqueous solution under light irradiation, and can achieve a maximum power density of 1196 mW m -2 when used as an anode in a MFC device. More importantly, a solar-microbial hybrid system by combining a PEC cell with a MFC is designed, in which the Nb 2 O 5- x NPs electrodes function as both anodes. The as-fabricated PEC-MFC hybrid device can simultaneously realize electricity and hydrogen using organic matter and solar light at zero external bias. This novel design and attempt might provide guidance for other materials to convert and store energy.

Flexible and Lightweight Fuel Cell with High Specific Power Density.

PubMed

Ning, Fandi; He, Xudong; Shen, Yangbin; Jin, Hehua; Li, Qingwen; Li, Da; Li, Shuping; Zhan, Yulu; Du, Ying; Jiang, Jingjing; Yang, Hui; Zhou, Xiaochun

2017-06-27

Flexible devices have been attracting great attention recently due to their numerous advantages. But the energy densities of current energy sources are still not high enough to support flexible devices for a satisfactory length of time. Although proton exchange membrane fuel cells (PEMFCs) do have a high-energy density, traditional PEMFCs are usually too heavy, rigid, and bulky to be used in flexible devices. In this research, we successfully invented a light and flexible air-breathing PEMFC by using a new design of PEMFC and a flexible composite electrode. The flexible air-breathing PEMFC with 1 × 1 cm 2 working area can be as light as 0.065 g and as thin as 0.22 mm. This new PEMFC exhibits an amazing specific volume power density as high as 5190 W L -1 , which is much higher than traditional (air-breathing) PEMFCs. Also outstanding is that the flexible PEMFC retains 89.1% of its original performance after being bent 600 times, and it retains its original performance after being dropped five times from a height of 30 m. Moreover, the research has demonstrated that when stacked, the flexible PEMFCs are also useful in mobile applications such as mobile phones. Therefore, our research shows that PEMFCs can be made light, flexible, and suitable for applications in flexible devices. These innovative flexible PEMFCs may also notably advance the progress in the PEMFC field, because flexible PEMFCs can achieve high specific power density with small size, small volume, low weight, and much lower cost; they are also much easier to mass produce.

Two-Dimensional Metal Oxide Nanomaterials for Next-Generation Rechargeable Batteries.

PubMed

Mei, Jun; Liao, Ting; Kou, Liangzhi; Sun, Ziqi

2017-12-01

The exponential increase in research focused on two-dimensional (2D) metal oxides has offered an unprecedented opportunity for their use in energy conversion and storage devices, especially for promising next-generation rechargeable batteries, such as lithium-ion batteries (LIBs) and sodium-ion batteries (NIBs), as well as some post-lithium batteries, including lithium-sulfur batteries, lithium-air batteries, etc. The introduction of well-designed 2D metal oxide nanomaterials into next-generation rechargeable batteries has significantly enhanced the performance of these energy-storage devices by providing higher chemically active interfaces, shortened ion-diffusion lengths, and improved in-plane carrier-/charge-transport kinetics, which have greatly promoted the development of nanotechnology and the practical application of rechargeable batteries. Here, the recent progress in the application of 2D metal oxide nanomaterials in a series of rechargeable LIBs, NIBs, and other post lithium-ion batteries is reviewed relatively comprehensively. Current opportunities and future challenges for the application of 2D nanomaterials in energy-storage devices to achieve high energy density, high power density, stable cyclability, etc. are summarized and outlined. It is believed that the integration of 2D metal oxide nanomaterials in these clean energy devices offers great opportunities to address challenges driven by increasing global energy demands. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode

NASA Astrophysics Data System (ADS)

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-08-01

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm-2 (specific capacitance of 50 F g-1) at a charge/discharge current density of 1 mA cm-2 and a maximum energy density of 39.9 W h kg-1 (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm-2, with a capacitance retention of 95% after 3000 cycles.

High energy density asymmetric supercapacitors with a nickel oxide nanoflake cathode and a 3D reduced graphene oxide anode.

PubMed

Luan, Feng; Wang, Gongming; Ling, Yichuan; Lu, Xihong; Wang, Hanyu; Tong, Yexiang; Liu, Xiao-Xia; Li, Yat

2013-09-07

Here we demonstrate a high energy density asymmetric supercapacitor with nickel oxide nanoflake arrays as the cathode and reduced graphene oxide as the anode. Nickel oxide nanoflake arrays were synthesized on a flexible carbon cloth substrate using a seed-mediated hydrothermal method. The reduced graphene oxide sheets were deposited on three-dimensional (3D) nickel foam by hydrothermal treatment of nickel foam in graphene oxide solution. The nanostructured electrodes provide a large effective surface area. The asymmetric supercapacitor device operates with a voltage of 1.7 V and achieved a remarkable areal capacitance of 248 mF cm(-2) (specific capacitance of 50 F g(-1)) at a charge/discharge current density of 1 mA cm(-2) and a maximum energy density of 39.9 W h kg(-1) (based on the total mass of active materials of 5.0 mg). Furthermore, the device showed an excellent charge/discharge cycling performance in 1.0 M KOH electrolyte at a current density of 5 mA cm(-2), with a capacitance retention of 95% after 3000 cycles.

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

DOE PAGES

Shi, Ji -Lei; Xiao, Dong -Dong; Ge, Mingyuan; ...

2018-01-15

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-richmore » cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.« less

High-Capacity Cathode Material with High Voltage for Li-Ion Batteries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Ji -Lei; Xiao, Dong -Dong; Ge, Mingyuan

Electrochemical energy storage devices with a high energy density are an important technology in modern society, especially for electric vehicles. The most effective approach to improve the energy density of batteries is to search for high-capacity electrode materials. According to the concept of energy quality, a high-voltage battery delivers a highly useful energy, thus providing a new insight to improve energy density. Based on this concept, a novel and successful strategy to increase the energy density and energy quality by increasing the discharge voltage of cathode materials and preserving high capacity is proposed. The proposal is realized in high-capacity Li-richmore » cathode materials. The average discharge voltage is increased from 3.5 to 3.8 V by increasing the nickel content and applying a simple after-treatment, and the specific energy is improved from 912 to 1033 Wh kg-1. The current work provides an insightful universal principle for developing, designing, and screening electrode materials for high energy density and energy quality.« less

High Energy Density Capacitors

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2010-07-01

BEEST Project: Recapping is developing a capacitor that could rival the energy storage potential and price of today’s best EV batteries. When power is needed, the capacitor rapidly releases its stored energy, similar to lightning being discharged from a cloud. Capacitors are an ideal substitute for batteries if their energy storage capacity can be improved. Recapping is addressing storage capacity by experimenting with the material that separates the positive and negative electrodes of its capacitors. These separators could significantly improve the energy density of electrochemical devices.

Freestanding Gold/Graphene-Oxide/Manganese Oxide Microsupercapacitor Displaying High Areal Energy Density.

PubMed

Morag, Ahiud; Becker, James Y; Jelinek, Raz

2017-07-10

Microsupercapacitors are touted as one of the promising "next frontiers" in energy-storage research and applications. Despite their potential, significant challenges still exist in terms of physical properties and electrochemical performance, particularly attaining high energy density, stability, ease of synthesis, and feasibility of large-scale production. We present new freestanding microporous electrodes comprising self-assembled scaffold of gold and reduced graphene oxide (rGO) nanowires coated with MnO 2 . The electrodes exhibited excellent electrochemical characteristics, particularly superior high areal capacitance. Moreover, the freestanding Au/rGO scaffold also served as the current collector, obviating the need for an additional electrode support required in most reported supercapacitors, thus enabling low volume and weight devices with a high overall device specific energy. Stacked symmetrical solid-state supercapacitors were fabricated using the Au/rGO/MnO 2 electrodes in parallel configurations showing the advantage of using freestanding electrodes in the fabrication of low-volume devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Recent Progress in Micro-Supercapacitors with In-Plane Interdigital Electrode Architecture.

PubMed

Liu, Nishuang; Gao, Yihua

2017-12-01

Due to the boom of miniaturized electronic devices in the last decade, there are great demands for ultrathin and flexible on-chip rechargeable energy storage microdevices. Supercapacitor, as one of the most hopeful appearing energy storage devices, can provide a wonderful alternative to batteries or electrolytic capacitors, owing to its fast charge and discharge rates, high power density, and long cycling stability. Especially for the recently developed micro-supercapacitors, the unique in-plane interdigital electrode architecture can fully meet the integration requirements of rapidly developed miniaturized electronic devices, and improve the power density of the unit via shortening the ionic diffusion distance between the interdigital electrodes. This concept introduces the recent advances on the design, fabrication, and application of planar micro-supercapacitors for on-chip energy storage from an overall perspective. Moreover, challenges and future development trends are discussed. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy harvesting for human wearable and implantable bio-sensors.

PubMed

Mitcheson, Paul D

2010-01-01

There are clear trade-offs between functionality, battery lifetime and battery volume for wearable and implantable wireless-biosensors which energy harvesting devices may be able to overcome. Reliable energy harvesting has now become a reality for machine condition monitoring and is finding applications in chemical process plants, refineries and water treatment works. However, practical miniature devices that can harvest sufficient energy from the human body to power a wireless bio-sensor are still in their infancy. This paper reviews the options for human energy harvesting in order to determine power availability for harvester-powered body sensor networks. The main competing technologies for energy harvesting from the human body are inertial kinetic energy harvesting devices and thermoelectric devices. These devices are advantageous to some other types as they can be hermetically sealed. In this paper the fundamental limit to the power output of these devices is compared as a function of generator volume when attached to a human whilst walking and running. It is shown that the kinetic energy devices have the highest fundamental power limits in both cases. However, when a comparison is made between the devices using device effectivenesses figures from previously demonstrated prototypes presented in the literature, the thermal device is competitive with the kinetic energy harvesting device when the subject is running and achieves the highest power density when the subject is walking.

Nonaqueous lithium-ion capacitors with high energy densities using trigol-reduced graphene oxide nanosheets as cathode-active material.

PubMed

Aravindan, Vanchiappan; Mhamane, Dattakumar; Ling, Wong Chui; Ogale, Satishchandra; Madhavi, Srinivasan

2013-12-01

One HEC of a material: The use of trigol-reduced graphene oxide nanosheets as cathode material in hybrid lithium-ion electrochemical capacitors (Li-HECs) results in an energy density of 45 Wh kg(-1) ; much enhanced when compared to similar devices. The mass loading of the active materials is optimized, and the devices show good cycling performance. Li-HECs employing these materials outperform other supercapacitors, making them attractive for use in power sources. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-assembling graphene-anthraquinone-2-sulphonate supramolecular nanostructures with enhanced energy density for supercapacitors.

PubMed

Gao, Lifang; Gan, Shiyu; Li, Hongyan; Han, Dongxue; Li, Fenghua; Bao, Yu; Niu, Li

2017-07-07

Boosting the energy density of capacitive energy storage devices remains a crucial issue for facilitating applications. Herein, we report a graphene-anthraquinone supramolecular nanostructure by self-assembly for supercapacitors. The sulfonated anthraquinone exhibits high water solubility, a π-conjugated structure and redox active features, which not only serve as a spacer to interact with and stabilize graphene but also introduce extra pseudocapacitance contributions. The formed nest-like three-dimensional (3D) nanostructure with further hydrothermal treatment enhances the accessibility of ion transfer and exposes the redox-active quinone groups in the electrolytes. A fabricated all-solid-state flexible symmetric device delivers a high specific capacitance of 398.5 F g -1 at 1 A g -1 (1.5 times higher than graphene), superior energy density (52.24 Wh kg -1 at about 1 kW kg -1 ) and good stability (82% capacitance retention after 10 000 cycles).

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions.

PubMed

Martins, Vitor L; Rennie, Anthony J R; Sanchez-Ramirez, Nedher; Torresi, Roberto M; Hall, Peter J

2018-02-01

Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN) 4 ] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm -1 ). Herein, we report the use of ILs containing the [B(CN) 4 ] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two-electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g -1 @ 15 A g -1 ). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs.

Highly compressible three-dimensional graphene hydrogel for foldable all-solid-state supercapacitor

NASA Astrophysics Data System (ADS)

Liu, Xianbin; Zou, Shuai; Liu, Kaixi; Lv, Chao; Wu, Ziping; Yin, Yanhong; Liang, Tongxiang; Xie, Zailai

2018-04-01

The fabrication of three-dimensional (3D) graphene-based macroscopic materials with superior mechanical and electrical properties for flexible energy storage devices is still extremely challenging. Here, we report a novel 3D graphene hydrogel decorated by the biomass phytic acid (PAGH) with developed porosity and strengthen mechanical property via hydrothermal and freeze-drying methods. The phytic acid molecules are intercalated into the graphene sheets, enabling robust network structure. This induces the formation of materials with larger specific surface area, lower density and enhanced compressive strength compared with pure GH. When directly employed as an electrode, the PAGH exhibits a high specific capacitance of 248.8 F g-1 at 1 A g-1 and excellent rate performance of 67.9% as current density increasing to 20 A g-1. Furthermore, the all-solid-state supercapacitor based PAGH can deliver outstanding cycle life (86.2% after cycling 10,000 times), glorious energy density (26.5 Wh kg-1) and power density (5135.1 W kg-1). The prepared device shows stable electrochemical behaviors at random bending angles. Therefore, the present work will open a new avenue to design and fabricate new flexible and portable graphene-based electrodes for future applications in energy storage devices.

Advanced materials and concepts for energy storage devices

NASA Astrophysics Data System (ADS)

Teng, Shiang Jen

Over the last decade, technological progress and advances in the miniaturization of electronic devices have increased demands for light-weight, high-efficiency, and carbon-free energy storage devices. These energy storage devices are expected to play important roles in automobiles, the military, power plants, and consumer electronics. Two main types of electrical energy storage systems studied in this research are Li ion batteries and supercapacitors. Several promising solid state electrolytes and supercapacitor electrode materials are investigated in this research. The first section of this dissertation is focused on the novel results on pulsed laser annealing of Li7La3Zr2O12 (LLZO). LLZO powders with a tetragonal structure were prepared by a sol-gel technique, then a pulsed laser annealing process was employed to convert the tetragonal powders to cubic LLZO without any loss of lithium. The second section of the dissertation reports on how Li5La 3Nb2O12 (LLNO) was successfully synthesized via a novel molten salt synthesis (MSS) method at the relatively low temperature of 900°C. The low sintering temperature prevented the loss of lithium that commonly occurs during synthesis using conventional solid state or wet chemical reactions. The second type of energy storage device studied is supercapacitors. Currently, research on supercapacitors is focused on increasing their energy densities and lowering their overall production costs by finding suitable electrode materials. The third section of this dissertation details how carbonized woods electrodes were used as supercapacitor electrode materials. A high energy density of 45.6 Wh/kg and a high power density of 2000 W/kg were obtained from the supercapacitor made from carbonized wood electrodes. The high performance of the supercapacitor was discovered to originate from the hierarchical porous structures of the carbonized wood. Finally, the fourth section of this dissertation is on the electrochemical effects of embedding Cu nanoparticles into a carbonized wood supercapacitor. The nano-composites were fabricated using a solution method. The electrochemical measurements indicated that Cu nanoparticles did enhance the energy density of the supercapacitor by a factor of three. Both cyclic voltammetry and cyclic charge-discharge measurements showed that the electrode has typical reversible pseudocapacitive behavior, with two pairs of redox reaction peaks.

Laser Scribed Graphene Cathode for Next Generation of High Performance Hybrid Supercapacitors.

PubMed

Lee, Seung-Hwan; Kim, Jin Hyeon; Yoon, Jung-Rag

2018-05-25

Hybrid supercapacitors have been regarded as next-generation energy storage devices due to their outstanding performances. However, hybrid supercapacitors remain a great challenge to enhance the energy density of hybrid supercapacitors. Herein, a novel approach for high-energy density hybrid supercapacitors based on a laser scribed graphene cathode and AlPO 4 -carbon hybrid coated H 2 Ti 12 O 25 (LSG/H-HTO) was designed. Benefiting from high-energy laser scribed graphene and high-power H-HTO, it was demonstrated that LSG/H-HTO delivers superior energy and power densities with excellent cyclability. Compared to previous reports on other hybrid supercapacitors, LSG/H-HTO electrode composition shows extraordinary energy densities of ~70.8 Wh/kg and power densities of ~5191.9 W/kg. Therefore, LSG/H-HTO can be regarded as a promising milestone in hybrid supercapacitors.

Solar Thermal Energy Storage Device: Hybrid Nanostructures for High-Energy-Density Solar Thermal Fuels

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2012-01-09

HEATS Project: MIT is developing a thermal energy storage device that captures energy from the sun; this energy can be stored and released at a later time when it is needed most. Within the device, the absorption of sunlight causes the solar thermal fuel’s photoactive molecules to change shape, which allows energy to be stored within their chemical bonds. A trigger is applied to release the stored energy as heat, where it can be converted into electricity or used directly as heat. The molecules would then revert to their original shape, and can be recharged using sunlight to begin themore » process anew. MIT’s technology would be 100% renewable, rechargeable like a battery, and emissions-free. Devices using these solar thermal fuels—called Hybrisol—can also be used without a grid infrastructure for applications such as de-icing, heating, cooking, and water purification.« less

On-chip supercapacitors with ultrahigh volumetric performance based on electrochemically co-deposited CuO/polypyrrole nanosheet arrays

NASA Astrophysics Data System (ADS)

Qian, Tao; Zhou, Jinqiu; Xu, Na; Yang, Tingzhou; Shen, Xiaowei; Liu, Xuejun; Wu, Shishan; Yan, Chenglin

2015-10-01

We introduce a new method for fabricating unique on-chip supercapacitors based on CuO/polypyrrole core/shell nanosheet arrays by means of direct electrochemical co-deposition on interdigital-like electrodes. The prepared all-solid-state device demonstrates exceptionally high specific capacitance of 1275.5 F cm-3 (˜40 times larger than that of CuO-only supercapacitors) and high-energy-density of 28.35 mWh cm-3, which are both significantly greater than other solid-state supercapacitors. More importantly, the device maintains approximately 100% capacity retention at 2.5 A cm-3 after 3000 cycles. The in situ co-deposition of CuO/polypyrrole nanosheets on interdigital substrate enables effective charge transport, electrode fabrication integrity, and device integration. Because of their high energy, power density, and stable cycling stability, these newly developed on-chip supercapacitors permit fast, reliable applications in portable and miniaturized electronic devices.

On-chip supercapacitors with ultrahigh volumetric performance based on electrochemically co-deposited CuO/polypyrrole nanosheet arrays.

PubMed

Qian, Tao; Zhou, Jinqiu; Xu, Na; Yang, Tingzhou; Shen, Xiaowei; Liu, Xuejun; Wu, Shishan; Yan, Chenglin

2015-10-23

We introduce a new method for fabricating unique on-chip supercapacitors based on CuO/polypyrrole core/shell nanosheet arrays by means of direct electrochemical co-deposition on interdigital-like electrodes. The prepared all-solid-state device demonstrates exceptionally high specific capacitance of 1275.5 F cm(-3) (∼40 times larger than that of CuO-only supercapacitors) and high-energy-density of 28.35 mWh cm(-3), which are both significantly greater than other solid-state supercapacitors. More importantly, the device maintains approximately 100% capacity retention at 2.5 A cm(-3) after 3000 cycles. The in situ co-deposition of CuO/polypyrrole nanosheets on interdigital substrate enables effective charge transport, electrode fabrication integrity, and device integration. Because of their high energy, power density, and stable cycling stability, these newly developed on-chip supercapacitors permit fast, reliable applications in portable and miniaturized electronic devices.

High-Performance Supercapacitors from Niobium Nanowire Yarns.

PubMed

Mirvakili, Seyed M; Mirvakili, Mehr Negar; Englezos, Peter; Madden, John D W; Hunter, Ian W

2015-07-01

The large-ion-accessible surface area of carbon nanotubes (CNTs) and graphene sheets formed as yarns, forests, and films enables miniature high-performance supercapacitors with power densities exceeding those of electrolytics while achieving energy densities equaling those of batteries. Capacitance and energy density can be enhanced by depositing highly pseudocapacitive materials such as conductive polymers on them. Yarns formed from carbon nanotubes are proposed for use in wearable supercapacitors. In this work, we show that high power, energy density, and capacitance in yarn form are not unique to carbon materials, and we introduce niobium nanowires as an alternative. These yarns show higher capacitance and energy per volume and are stronger and 100 times more conductive than similarly spun carbon multiwalled nanotube (MWNT) and graphene yarns. The long niobium nanowires, formed by repeated extrusion and drawing, achieve device volumetric peak power and energy densities of 55 MW·m(-3) (55 W·cm(-3)) and 25 MJ·m(-3) (7 mWh·cm(-3)), 2 and 5 times higher than that for state-of-the-art CNT yarns, respectively. The capacitance per volume of Nb nanowire yarn is lower than the 158 MF·m(-3) (158 F·cm(-3)) reported for carbon-based materials such as reduced graphene oxide (RGO) and CNT wet-spun yarns, but the peak power and energy densities are 200 and 2 times higher, respectively. Achieving high power in long yarns is made possible by the high conductivity of the metal, and achievement of high energy density is possible thanks to the high internal surface area. No additional metal backing is needed, unlike for CNT yarns and supercapacitors in general, saving substantial space. As the yarn is infiltrated with pseudocapacitive materials such as poly(3,4-ethylenedioxythiophene) (PEDOT), the energy density is further increased to 10 MJ·m(-3) (2.8 mWh·cm(-3)). Similar to CNT yarns, niobium nanowire yarns are highly flexible and show potential for weaving into textiles and use in wearable devices.

Symmetric Sodium-Ion Capacitor Based on Na0.44MnO2 Nanorods for Low-Cost and High-Performance Energy Storage.

PubMed

Chen, Zhongxue; Yuan, Tianci; Pu, Xiangjun; Yang, Hanxi; Ai, Xinping; Xia, Yongyao; Cao, Yuliang

2018-04-11

Batteries and electrochemical capacitors play very important roles in the portable electronic devices and electric vehicles and have shown promising potential for large-scale energy storage applications. However, batteries or capacitors alone cannot meet the energy and power density requirements because rechargeable batteries have a poor power property, whereas supercapacitors offer limited capacity. Here, a novel symmetric sodium-ion capacitor (NIC) is developed based on low-cost Na 0.44 MnO 2 nanorods. The Na 0.44 MnO 2 with unique nanoarchitectures and iso-oriented feature offers shortened diffusion path lengths for both electronic and Na + transport and reduces the stress associated with Na + insertion and extraction. Benefiting from these merits, the symmetric device achieves a high power density of 2432.7 W kg -1 , an improved energy density of 27.9 Wh kg -1 , and a capacitance retention of 85.2% over 5000 cycles. Particularly, the symmetric NIC based on Na 0.44 MnO 2 permits repeatedly reverse-polarity characteristics, thus simplifying energy management system and greatly enhancing the safety under abuse condition. This cost-effective, high-safety, and high-performance symmetric NIC can balance the energy and power density between batteries and capacitors and serve as an electric power source for future low-maintenance large-scale energy storage systems.

Energetic Combustion Devices for Aerospace Propulsion and Power

NASA Technical Reports Server (NTRS)

Litchford, Ron J.

2000-01-01

Chemical reactions have long been the mainstay thermal energy source for aerospace propulsion and power. Although it is widely recognized that the intrinsic energy density limitations of chemical bonds place severe constraints on maximum realizable performance, it will likely be several years before systems based on high energy density nuclear fuels can be placed into routine service. In the mean time, efforts to develop high energy density chemicals and advanced combustion devices which can utilize such energetic fuels may yield worthwhile returns in overall system performance and cost. Current efforts in this vein are being carried out at NASA MSFC under the direction of the author in the areas of pulse detonation engine technology development and light metals combustion devices. Pulse detonation engines are touted as a low cost alternative to gas turbine engines and to conventional rocket engines, but actual performance and cost benefits have yet to be convincingly demonstrated. Light metal fueled engines also offer potential benefits in certain niche applications such as aluminum/CO2 fueled engines for endo-atmospheric Martian propulsion. Light metal fueled MHD generators also present promising opportunities with respect to electric power generation for electromagnetic launch assist. This presentation will discuss the applications potential of these concepts with respect to aero ace propulsion and power and will review the current status of the development efforts.

Estimation of energy density of Li-S batteries with liquid and solid electrolytes

NASA Astrophysics Data System (ADS)

Li, Chunmei; Zhang, Heng; Otaegui, Laida; Singh, Gurpreet; Armand, Michel; Rodriguez-Martinez, Lide M.

2016-09-01

With the exponential growth of technology in mobile devices and the rapid expansion of electric vehicles into the market, it appears that the energy density of the state-of-the-art Li-ion batteries (LIBs) cannot satisfy the practical requirements. Sulfur has been one of the best cathode material choices due to its high charge storage (1675 mAh g-1), natural abundance and easy accessibility. In this paper, calculations are performed for different cell design parameters such as the active material loading, the amount/thickness of electrolyte, the sulfur utilization, etc. to predict the energy density of Li-S cells based on liquid, polymeric and ceramic electrolytes. It demonstrates that Li-S battery is most likely to be competitive in gravimetric energy density, but not volumetric energy density, with current technology, when comparing with LIBs. Furthermore, the cells with polymer and thin ceramic electrolytes show promising potential in terms of high gravimetric energy density, especially the cells with the polymer electrolyte. This estimation study of Li-S energy density can be used as a good guidance for controlling the key design parameters in order to get desirable energy density at cell-level.

Advanced materials for energy storage.

PubMed

Liu, Chang; Li, Feng; Ma, Lai-Peng; Cheng, Hui-Ming

2010-02-23

Popularization of portable electronics and electric vehicles worldwide stimulates the development of energy storage devices, such as batteries and supercapacitors, toward higher power density and energy density, which significantly depends upon the advancement of new materials used in these devices. Moreover, energy storage materials play a key role in efficient, clean, and versatile use of energy, and are crucial for the exploitation of renewable energy. Therefore, energy storage materials cover a wide range of materials and have been receiving intensive attention from research and development to industrialization. In this Review, firstly a general introduction is given to several typical energy storage systems, including thermal, mechanical, electromagnetic, hydrogen, and electrochemical energy storage. Then the current status of high-performance hydrogen storage materials for on-board applications and electrochemical energy storage materials for lithium-ion batteries and supercapacitors is introduced in detail. The strategies for developing these advanced energy storage materials, including nanostructuring, nano-/microcombination, hybridization, pore-structure control, configuration design, surface modification, and composition optimization, are discussed. Finally, the future trends and prospects in the development of advanced energy storage materials are highlighted.

High temperature electrical energy storage: advances, challenges, and frontiers.

PubMed

Lin, Xinrong; Salari, Maryam; Arava, Leela Mohana Reddy; Ajayan, Pulickel M; Grinstaff, Mark W

2016-10-24

With the ongoing global effort to reduce greenhouse gas emission and dependence on oil, electrical energy storage (EES) devices such as Li-ion batteries and supercapacitors have become ubiquitous. Today, EES devices are entering the broader energy use arena and playing key roles in energy storage, transfer, and delivery within, for example, electric vehicles, large-scale grid storage, and sensors located in harsh environmental conditions, where performance at temperatures greater than 25 °C are required. The safety and high temperature durability are as critical or more so than other essential characteristics (e.g., capacity, energy and power density) for safe power output and long lifespan. Consequently, significant efforts are underway to design, fabricate, and evaluate EES devices along with characterization of device performance limitations such as thermal runaway and aging. Energy storage under extreme conditions is limited by the material properties of electrolytes, electrodes, and their synergetic interactions, and thus significant opportunities exist for chemical advancements and technological improvements. In this review, we present a comprehensive analysis of different applications associated with high temperature use (40-200 °C), recent advances in the development of reformulated or novel materials (including ionic liquids, solid polymer electrolytes, ceramics, and Si, LiFePO 4 , and LiMn 2 O 4 electrodes) with high thermal stability, and their demonstrative use in EES devices. Finally, we present a critical overview of the limitations of current high temperature systems and evaluate the future outlook of high temperature batteries with well-controlled safety, high energy/power density, and operation over a wide temperature range.

Heat to electricity conversion by cold carrier emissive energy harvesters

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strandberg, Rune

2015-12-07

This paper suggests a method to convert heat to electricity by the use of devices called cold carrier emissive energy harvesters (cold carrier EEHs). The working principle of such converters is explained and theoretical power densities and efficiencies are calculated for ideal devices. Cold carrier EEHs are based on the same device structure as hot carrier solar cells, but works in an opposite way. Whereas a hot carrier solar cell receives net radiation from the sun and converts some of this radiative heat flow into electricity, a cold carrier EEH sustains a net outflux of radiation to the surroundings whilemore » converting some of the energy supplied to it into electricity. It is shown that the most basic type of cold carrier EEHs have the same theoretical efficiency as the ideal emissive energy harvesters described earlier by Byrnes et al. In the present work, it is also shown that if the emission from the cold carrier EEH originates from electron transitions across an energy gap where a difference in the chemical potential of the electrons above and below the energy gap is sustained, power densities slightly higher than those given by Byrnes et al. can be achieved.« less

Integrated Photoelectrochemical Solar Energy Conversion and Organic Redox Flow Battery Devices.

PubMed

Li, Wenjie; Fu, Hui-Chun; Li, Linsen; Cabán-Acevedo, Miguel; He, Jr-Hau; Jin, Song

2016-10-10

Building on regenerative photoelectrochemical solar cells and emerging electrochemical redox flow batteries (RFBs), more efficient, scalable, compact, and cost-effective hybrid energy conversion and storage devices could be realized. An integrated photoelectrochemical solar energy conversion and electrochemical storage device is developed by integrating regenerative silicon solar cells and 9,10-anthraquinone-2,7-disulfonic acid (AQDS)/1,2-benzoquinone-3,5-disulfonic acid (BQDS) RFBs. The device can be directly charged by solar light without external bias, and discharged like normal RFBs with an energy storage density of 1.15 Wh L -1 and a solar-to-output electricity efficiency (SOEE) of 1.7 % over many cycles. The concept exploits a previously undeveloped design connecting two major energy technologies and promises a general approach for storing solar energy electrochemically with high theoretical storage capacity and efficiency. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Design of Supercapacitor Electrodes Using Molecular Dynamics Simulations

NASA Astrophysics Data System (ADS)

Bo, Zheng; Li, Changwen; Yang, Huachao; Ostrikov, Kostya; Yan, Jianhua; Cen, Kefa

2018-06-01

Electric double-layer capacitors (EDLCs) are advanced electrochemical devices for energy storage and have attracted strong interest due to their outstanding properties. Rational optimization of electrode-electrolyte interactions is of vital importance to enhance device performance for practical applications. Molecular dynamics (MD) simulations could provide theoretical guidelines for the optimal design of electrodes and the improvement of capacitive performances, e.g., energy density and power density. Here we discuss recent MD simulation studies on energy storage performance of electrode materials containing porous to nanostructures. The energy storage properties are related to the electrode structures, including electrode geometry and electrode modifications. Altering electrode geometry, i.e., pore size and surface topography, can influence EDL capacitance. We critically examine different types of electrode modifications, such as altering the arrangement of carbon atoms, doping heteroatoms and defects, which can change the quantum capacitance. The enhancement of power density can be achieved by the intensified ion dynamics and shortened ion pathway. Rational control of the electrode morphology helps improve the ion dynamics by decreasing the ion diffusion pathway. Tuning the surface properties (e.g., the affinity between the electrode and the ions) can affect the ion-packing phenomena. Our critical analysis helps enhance the energy and power densities of EDLCs by modulating the corresponding electrode structures and surface properties.[Figure not available: see fulltext.

Application of hybrid supercapacitor using granule Li4Ti5O12/activated carbon with variation of current density

NASA Astrophysics Data System (ADS)

Lee, Byung-Gwan; Lee, Seung-Hwan

2017-03-01

We report the electrochemical performance of asymmetric hybrid supercapacitors composed of granule Li4Ti5O12 as an anode and activated carbon as a cathode with different current densities. It is demonstrated that the hybrid supercapacitors show good initial discharge capacities were ranged from 39.8 to 46.4 F g-1 in the current densities range of 0.3-1 A g-1. The performance degradation is proportional to the current density due to quick gassing, resulting from H2O and HF formation. In particular, the hybrid supercapacitors show the pretty good cycling stability of 97.4%, even at the high current density of 0.8 A g-1, which are among most important performance in the real application for energy storage devices. Therefore, we believe that hybrid supercapacitors using granule Li4Ti5O12/activated carbon are eligible for the promising next generation energy devices.

Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

PubMed Central

Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

2016-01-01

Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm−2 & 19.1 Wh Kg−1 and 194 mF cm−2 & 4.5 Wh Kg−1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm−2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices. PMID:26936283

Microwave Assisted Synthesis of Porous NiCo2O4 Microspheres: Application as High Performance Asymmetric and Symmetric Supercapacitors with Large Areal Capacitance

NASA Astrophysics Data System (ADS)

Khalid, Syed; Cao, Chuanbao; Wang, Lin; Zhu, Youqi

2016-03-01

Large areal capacitance is essentially required to integrate the energy storage devices at the microscale electronic appliances. Energy storage devices based on metal oxides are mostly fabricated with low mass loading per unit area which demonstrated low areal capacitance. It is still a challenge to fabricate supercapacitor devices of porous metal oxides with large areal capacitance. Herein we report microwave method followed by a pyrolysis of the as-prepared precursor is used to synthesize porous nickel cobaltite microspheres. Porous NiCo2O4 microspheres are capable to deliver large areal capacitance due to their high specific surface area and small crystallite size. The facile strategy is successfully demonstrated to fabricate aqueous-based asymmetric & symmetric supercapacitor devices of porous NiCo2O4 microspheres with high mass loading of electroactive materials. The asymmetric & symmetric devices exhibit maximum areal capacitance and energy density of 380 mF cm-2 & 19.1 Wh Kg-1 and 194 mF cm-2 & 4.5 Wh Kg-1 (based on total mass loading of 6.25 & 6.0 mg) respectively at current density of 1 mA cm-2. The successful fabrication of symmetric device also indicates that NiCo2O4 can also be used as the negative electrode material for futuristic asymmetric devices.

Piezoelectric Energy Harvesting Solutions

PubMed Central

Caliò, Renato; Rongala, Udaya Bhaskar; Camboni, Domenico; Milazzo, Mario; Stefanini, Cesare; de Petris, Gianluca; Oddo, Calogero Maria

2014-01-01

This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions. PMID:24618725

Graphene-based in-plane micro-supercapacitors with high power and energy densities

PubMed Central

Wu, Zhong–Shuai; Parvez, Khaled; Feng, Xinliang; Müllen, Klaus

2013-01-01

Micro-supercapacitors are important on-chip micro-power sources for miniaturized electronic devices. Although the performance of micro-supercapacitors has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures, their power or energy densities remain far from those of electrolytic capacitors or lithium thin-film batteries. Here we demonstrate graphene-based in-plane interdigital micro-supercapacitors on arbitrary substrates. The resulting micro-supercapacitors deliver an area capacitance of 80.7 μF cm−2 and a stack capacitance of 17.9 F cm−3. Further, they show a power density of 495 W cm−3 that is higher than electrolytic capacitors, and an energy density of 2.5 mWh cm−3 that is comparable to lithium thin-film batteries, in association with superior cycling stability. Such microdevices allow for operations at ultrahigh rate up to 1,000 V s−1, three orders of magnitude higher than that of conventional supercapacitors. Micro-supercapacitors with an in-plane geometry have great promise for numerous miniaturized or flexible electronic applications. PMID:24042088

Graphene-based in-plane micro-supercapacitors with high power and energy densities.

PubMed

Wu, Zhong-Shuai; Parvez, Khaled; Feng, Xinliang; Müllen, Klaus

2013-01-01

Micro-supercapacitors are important on-chip micro-power sources for miniaturized electronic devices. Although the performance of micro-supercapacitors has been significantly advanced by fabricating nanostructured materials, developing thin-film manufacture technologies and device architectures, their power or energy densities remain far from those of electrolytic capacitors or lithium thin-film batteries. Here we demonstrate graphene-based in-plane interdigital micro-supercapacitors on arbitrary substrates. The resulting micro-supercapacitors deliver an area capacitance of 80.7 μF cm⁻² and a stack capacitance of 17.9 F cm⁻³. Further, they show a power density of 495 W cm⁻³ that is higher than electrolytic capacitors, and an energy density of 2.5 mWh cm⁻³ that is comparable to lithium thin-film batteries, in association with superior cycling stability. Such microdevices allow for operations at ultrahigh rate up to 1,000 V s⁻¹, three orders of magnitude higher than that of conventional supercapacitors. Micro-supercapacitors with an in-plane geometry have great promise for numerous miniaturized or flexible electronic applications.

Low-crystalline iron oxide hydroxide nanoparticle anode for high-performance supercapacitors

PubMed Central

Owusu, Kwadwo Asare; Qu, Longbing; Li, Jiantao; Wang, Zhaoyang; Zhao, Kangning; Yang, Chao; Hercule, Kalele Mulonda; Lin, Chao; Shi, Changwei; Wei, Qiulong; Zhou, Liang; Mai, Liqiang

2017-01-01

Carbon materials are generally preferred as anodes in supercapacitors; however, their low capacitance limits the attained energy density of supercapacitor devices with aqueous electrolytes. Here, we report a low-crystalline iron oxide hydroxide nanoparticle anode with comprehensive electrochemical performance at a wide potential window. The iron oxide hydroxide nanoparticles present capacitances of 1,066 and 716 F g−1 at mass loadings of 1.6 and 9.1 mg cm−2, respectively, a rate capability with 74.6% of capacitance retention at 30 A g−1, and cycling stability retaining 91% of capacitance after 10,000 cycles. The performance is attributed to a dominant capacitive charge-storage mechanism. An aqueous hybrid supercapacitor based on the iron oxide hydroxide anode shows stability during float voltage test for 450 h and an energy density of 104 Wh kg−1 at a power density of 1.27 kW kg−1. A packaged device delivers gravimetric and volumetric energy densities of 33.14 Wh kg−1 and 17.24 Wh l−1, respectively. PMID:28262797

The high energy multicharged particle exposure of the microbial ecology evaluation device on board the Apollo 16 spacecraft

NASA Technical Reports Server (NTRS)

Benton, E. V.; Henke, R. P.

1973-01-01

The high energy multicharged cosmic-ray-particle exposure of the Microbial Ecology Evaluation Device package on board the Apollo 16 spacecraft was monitored using cellulose nitrate, Lexan polycarbonate, nuclear emulsion, and silver chloride crystal nuclear-track detectors. The results of the analysis of these detectors include the measured particle fluences, the linear energy transfer spectra, and the integral atomic number spectrum of stopping particle density. The linear energy transfer spectrum is used to compute the fractional cell loss in human kidney (T1) cells caused by heavy particles. Because the Microbial Ecology Evaluation Device was better shielded, the high-energy multicharged particle exposure was less than that measured on the crew passive dosimeters.

Aloe vera Derived Activated High-Surface-Area Carbon for Flexible and High-Energy Supercapacitors.

PubMed

Karnan, M; Subramani, K; Sudhan, N; Ilayaraja, N; Sathish, M

2016-12-28

Materials which possess high specific capacitance in device configuration with low cost are essential for viable application in supercapacitors. Herein, a flexible high-energy supercapacitor device was fabricated using porous activated high-surface-area carbon derived from aloe leaf (Aloe vera) as a precursor. The A. vera derived activated carbon showed mesoporous nature with high specific surface area of ∼1890 m 2 /g. A high specific capacitance of 410 and 306 F/g was achieved in three-electrode and symmetric two-electrode system configurations in aqueous electrolyte, respectively. The fabricated all-solid-state device showed a high specific capacitance of 244 F/g with an energy density of 8.6 Wh/kg. In an ionic liquid electrolyte, the fabricated device showed a high specific capacitance of 126 F/g and a wide potential window up to 3 V, which results in a high energy density of 40 Wh/kg. Furthermore, it was observed that the activation temperature has significant role in the electrochemical performance, as the activated sample at 700 °C showed best activity than the samples activated at 600 and 800 °C. The electron microscopic images (FE-SEM and HR-TEM) confirmed the formation of pores by the chemical activation. A fabricated supercapacitor device in ionic liquid with 3 V could power up a red LED for 30 min upon charging for 20s. Also, it is shown that the operation voltage and capacitance of flexible all-solid-state symmetric supercapacitors fabricated using aloe-derived activated carbon could be easily tuned by series and parallel combinations. The performance of fabricated supercapacitor devices using A. vera derived activated carbon in all-solid-state and ionic liquid indicates their viable applications in flexible devices and energy storage.

Low Li+ Insertion Barrier Carbon for High Energy Efficient Lithium-Ion Capacitor.

PubMed

Lee, Wee Siang Vincent; Huang, Xiaolei; Tan, Teck Leong; Xue, Jun Min

2018-01-17

Lithium-ion capacitor (LIC) is an attractive energy-storage device (ESD) that promises high energy density at moderate power density. However, the key challenge in its design is the low energy efficient negative electrode, which barred the realization of such research system in fulfilling the current ESD technological inadequacy due to its poor overall energy efficiency. Large voltage hysteresis is the main issue behind high energy density alloying/conversion-type materials, which reduces the electrode energy efficiency. Insertion-type material though averted in most research due to the low capacity remains to be highly favorable in commercial application due to its lower voltage hysteresis. To further reduce voltage hysteresis and increase capacity, amorphous carbon with wider interlayer spacing has been demonstrated in the simulation result to significantly reduce Li + insertion barrier. Hence, by employing such amorphous carbon, together with disordered carbon positive electrode, a high energy efficient LIC with round-trip energy efficiency of 84.3% with a maximum energy density of 133 Wh kg -1 at low power density of 210 W kg -1 can be achieved.

Maximizing the performance of photothermal actuators by combining smart materials with supplementary advantages

PubMed Central

Wang, Tongyu; Torres, David; Fernández, Félix E.; Wang, Chuan; Sepúlveda, Nelson

2017-01-01

The search for higher-performance photothermal microactuators has typically involved unavoidable trade-offs that hinder the demonstration of ubiquitous devices with high energy density, speed, flexibility, efficiency, sensitivity, and multifunctionality. Improving some of these parameters often implies deterioration of others. Photothermal actuators are driven by the conversion of absorbed optical energy into thermal energy, which, by different mechanisms, can produce mechanical displacement of a structure. We present a device that has been strategically designed to show high performance in every metric and respond to optical radiation of selected wavelength bands. The device combines the large energy densities and sensitivity of vanadium dioxide (VO2)–based actuators with the wavelength-selective absorption properties of single-walled carbon nanotube (SWNT) films of different chiralities. SWNT coatings increased the speed of VO2 actuators by a factor of 2 while decreasing the power consumption by approximately 50%. Devices coated with metallic SWNT were found to be 1.57 times more responsive to red light than to near-infrared, whereas semiconducting SWNT coatings resulted in 1.42 times higher responsivities to near-infrared light than to red light. The added functionality establishes a link between optical and mechanical domains of high-performance photoactuators and enables the future development of mechanical logic gates and electronic devices that are triggered by optical radiation from different frequency bands. PMID:28439553

Characterization of pi-Conjugated Polymers for Transistor and Photovoltaic Applications

NASA Astrophysics Data System (ADS)

Paulsen, Bryan D.

pi-Conjugated polymers represent a unique class of optoelectronic materials. Being polymers, they are solution processable and inherently "soft" materials. This makes them attractive candidates for the production of roll-to-roll printed electronic devices on flexible substrates. The optical and electronic properties of pi-conjugated polymers are synthetically tunable allowing material sets to be tailored to specific applications. Two of the most heavily researched applications are the thin film transistor, the building block of electronic circuits, and the bulk heterojunction solar cell, which holds great potential as a renewable energy source. Key to developing commercially feasible pi-conjugated polymer devices is a thorough understanding of the electronic structure and charge transport behavior of these materials in relationship with polymer structure. Here this structure property relationship has been investigated through electrical and electrochemical means in concert with a variety of other characterization techniques and device test beds. The tunability of polymer optical band gap and frontier molecular orbital energy level was investigated in systems of vinyl incorporating statistical copolymers. Energy levels and band gaps are crucial parameters in developing efficient photovoltaic devices, with control of these parameters being highly desirable. Additionally, charge transport and density of electronic states were investigated in pi-conjugated polymers at extremely high electrochemically induced charge density. Finally, the effects of molecular weight on pi-conjugated polymer optical properties, energy levels, charge transport, morphology, and photovoltaic device performance was examined.

Hierarchical Ni-Co layered double hydroxide nanosheets on functionalized 3D-RGO films for high energy density asymmetric supercapacitor

NASA Astrophysics Data System (ADS)

Jiang, Liyang; Sui, Yanwei; Qi, Jiqiu; Chang, Yuan; He, Yezeng; Meng, Qingkun; Wei, Fuxiang; Sun, Zhi; Jin, Yunxue

2017-12-01

In this paper, ultrathin reduced graphene oxide films on nickel foam were fabricated via a facile dip-coating method combined with thermal reduction. Hierarchical Ni-Co layered double hydroxide nanosheets with network structure were electrodeposited on the ultrathin reduced graphene oxide films in a simple three-electrode system. The thickness of Ni-Co layered double hydroxide nanosheets can be controlled through adjusting the deposition temperature. The as-prepared electrode exhibited excellent electrochemical performance with specific capacitance of 1454.2 F g-1 at a current density of 1 A g-1. An asymmetric supercapacitor device was designed with the as-prepared composites as positive electrode material and Nitrogen-doped reduced graphene oxide as negative electrode material. This device could be operated in a working voltage range of 0-1.8 V in 1 M KOH aqueous electrolyte, delivering a high energy density of 56.4 W h kg-1 at a power density of 882.5 W kg-1. One supercapacitor can power two LEDs with rated voltage of 1.8-2.0 V. After 10,000 consecutive charge-discharge tests at 10 A g-1, this asymmetric supercapacitor revealed an excellent cycle life with 98.3% specific capacitance retention. These excellent electrochemical performances make it become one of most promising candidates for high energy supercapacitor device.

Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices.

PubMed

Nukala, Pavan; Lin, Chia-Chun; Composto, Russell; Agarwal, Ritesh

2016-01-25

Crystal-amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier-lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13-0.6 MA cm(-2)) compared with the melt-quench strategy (∼50 MA cm(-2)). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation.

Ultralow-power switching via defect engineering in germanium telluride phase-change memory devices

PubMed Central

Nukala, Pavan; Lin, Chia-Chun; Composto, Russell; Agarwal, Ritesh

2016-01-01

Crystal–amorphous transformation achieved via the melt-quench pathway in phase-change memory involves fundamentally inefficient energy conversion events; and this translates to large switching current densities, responsible for chemical segregation and device degradation. Alternatively, introducing defects in the crystalline phase can engineer carrier localization effects enhancing carrier–lattice coupling; and this can efficiently extract work required to introduce bond distortions necessary for amorphization from input electrical energy. Here, by pre-inducing extended defects and thus carrier localization effects in crystalline GeTe via high-energy ion irradiation, we show tremendous improvement in amorphization current densities (0.13–0.6 MA cm−2) compared with the melt-quench strategy (∼50 MA cm−2). We show scaling behaviour and good reversibility on these devices, and explore several intermediate resistance states that are accessible during both amorphization and recrystallization pathways. Existence of multiple resistance states, along with ultralow-power switching and scaling capabilities, makes this approach promising in context of low-power memory and neuromorphic computation. PMID:26805748

Binder-free three-dimensional high energy density electrodes for ionic-liquid supercapacitors.

PubMed

Tran, Chau; Lawrence, Daniel; Richey, Francis W; Dillard, Caitlin; Elabd, Yossef A; Kalra, Vibha

2015-09-18

We demonstrate a facile methodology to fabricate binder-free porous carbon nanofiber electrodes for room temperature ionic-liquid supercapacitors. The device provides an energy density of 80 W h kg(-1) based on the mass of two electrodes while retaining the high rate capability of supercapacitors with near-ideal CV curves at a high scan rate of 200 mV s(-1).

Carbon foams for energy storage devices

DOEpatents

Kaschmitter, James L.; Mayer, Steven T.; Pekala, Richard W.

1996-01-01

A high energy density capacitor incorporating a variety of carbon foam electrodes is described. The foams, derived from the pyrolysis of resorcinol-formaldehyde and related polymers, are high density (0.1 g/cc-1.0 g/cc) electrically conductive and have high surface areas (400 m.sup.2 /g-1000 m.sup.2 /g). Capacitances on the order of several tens of farad per gram of electrode are achieved.

Wearable energy-smart ribbons for synchronous energy harvest and storage

PubMed Central

Li, Chao; Islam, Md. Monirul; Moore, Julian; Sleppy, Joseph; Morrison, Caleb; Konstantinov, Konstantin; Dou, Shi Xue; Renduchintala, Chait; Thomas, Jayan

2016-01-01

A promising energy source for many current and future applications is a ribbon-like device that could simultaneously harvest and store energy. Due to the high flexibility and weavable property, a fabric/matrix made using these ribbons could be highly beneficial for powering wearable electronics. Unlike the approach of using two separate devices, here we report a ribbon that integrates a solar cell and a supercapacitor. The electrons generated by the solar cell are directly transferred and stored on the reverse side of its electrode which in turn also functions as an electrode for the supercapacitor. When the flexible solar ribbon is illuminated with simulated solar light, the supercapacitor holds an energy density of 1.15 mWh cm−3 and a power density of 243 mW cm−3. Moreover, these ribbons are successfully woven into a fabric form. Our all-solid-state ribbon unveils a highly flexible and portable self-sufficient energy system with potential applications in wearables, drones and electric vehicles. PMID:27834367

Wearable energy-smart ribbons for synchronous energy harvest and storage

NASA Astrophysics Data System (ADS)

Li, Chao; Islam, Md. Monirul; Moore, Julian; Sleppy, Joseph; Morrison, Caleb; Konstantinov, Konstantin; Dou, Shi Xue; Renduchintala, Chait; Thomas, Jayan

2016-11-01

A promising energy source for many current and future applications is a ribbon-like device that could simultaneously harvest and store energy. Due to the high flexibility and weavable property, a fabric/matrix made using these ribbons could be highly beneficial for powering wearable electronics. Unlike the approach of using two separate devices, here we report a ribbon that integrates a solar cell and a supercapacitor. The electrons generated by the solar cell are directly transferred and stored on the reverse side of its electrode which in turn also functions as an electrode for the supercapacitor. When the flexible solar ribbon is illuminated with simulated solar light, the supercapacitor holds an energy density of 1.15 mWh cm-3 and a power density of 243 mW cm-3. Moreover, these ribbons are successfully woven into a fabric form. Our all-solid-state ribbon unveils a highly flexible and portable self-sufficient energy system with potential applications in wearables, drones and electric vehicles.

Wearable energy-smart ribbons for synchronous energy harvest and storage.

PubMed

Li, Chao; Islam, Md Monirul; Moore, Julian; Sleppy, Joseph; Morrison, Caleb; Konstantinov, Konstantin; Dou, Shi Xue; Renduchintala, Chait; Thomas, Jayan

2016-11-11

A promising energy source for many current and future applications is a ribbon-like device that could simultaneously harvest and store energy. Due to the high flexibility and weavable property, a fabric/matrix made using these ribbons could be highly beneficial for powering wearable electronics. Unlike the approach of using two separate devices, here we report a ribbon that integrates a solar cell and a supercapacitor. The electrons generated by the solar cell are directly transferred and stored on the reverse side of its electrode which in turn also functions as an electrode for the supercapacitor. When the flexible solar ribbon is illuminated with simulated solar light, the supercapacitor holds an energy density of 1.15 mWh cm -3 and a power density of 243 mW cm -3 . Moreover, these ribbons are successfully woven into a fabric form. Our all-solid-state ribbon unveils a highly flexible and portable self-sufficient energy system with potential applications in wearables, drones and electric vehicles.

Coaxial wet-spun yarn supercapacitors for high-energy density and safe wearable electronics

NASA Astrophysics Data System (ADS)

Kou, Liang; Huang, Tieqi; Zheng, Bingna; Han, Yi; Zhao, Xiaoli; Gopalsamy, Karthikeyan; Sun, Haiyan; Gao, Chao

2014-05-01

Yarn supercapacitors have great potential in future portable and wearable electronics because of their tiny volume, flexibility and weavability. However, low-energy density limits their development in the area of wearable high-energy density devices. How to enhance their energy densities while retaining their high-power densities is a critical challenge for yarn supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres, which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and 177 mF cm-2 and energy densities of 5.91 and 3.84 μWh cm-2, respectively. A cloth supercapacitor superior to commercial capacitor is further interwoven from two individual 40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology and excellent performance of yarn supercapacitors paves the way to wearable and safe electronics.

Coaxial wet-spun yarn supercapacitors for high-energy density and safe wearable electronics

PubMed Central

Kou, Liang; Huang, Tieqi; Zheng, Bingna; Han, Yi; Zhao, Xiaoli; Gopalsamy, Karthikeyan; Sun, Haiyan; Gao, Chao

2014-01-01

Yarn supercapacitors have great potential in future portable and wearable electronics because of their tiny volume, flexibility and weavability. However, low-energy density limits their development in the area of wearable high-energy density devices. How to enhance their energy densities while retaining their high-power densities is a critical challenge for yarn supercapacitor development. Here we propose a coaxial wet-spinning assembly approach to continuously spin polyelectrolyte-wrapped graphene/carbon nanotube core-sheath fibres, which are used directly as safe electrodes to assembly two-ply yarn supercapacitors. The yarn supercapacitors using liquid and solid electrolytes show ultra-high capacitances of 269 and 177 mF cm−2 and energy densities of 5.91 and 3.84 μWh cm−2, respectively. A cloth supercapacitor superior to commercial capacitor is further interwoven from two individual 40-cm-long coaxial fibres. The combination of scalable coaxial wet-spinning technology and excellent performance of yarn supercapacitors paves the way to wearable and safe electronics. PMID:24786366

A Thin Film Flexible Supercapacitor Based on Oblique Angle Deposited Ni/NiO Nanowire Arrays.

PubMed

Ma, Jing; Liu, Wen; Zhang, Shuyuan; Ma, Zhe; Song, Peishuai; Yang, Fuhua; Wang, Xiaodong

2018-06-11

With high power density, fast charging-discharging speed, and a long cycling life, supercapacitors are a kind of highly developed novel energy-storage device that has shown a growing performance and various unconventional shapes such as flexible, linear-type, stretchable, self-healing, etc. Here, we proposed a rational design of thin film, flexible micro-supercapacitors with in-plane interdigital electrodes, where the electrodes were fabricated using the oblique angle deposition technique to grow oblique Ni/NiO nanowire arrays directly on polyimide film. The obtained electrodes have a high specific surface area and good adhesion to the substrate compared with other in-plane micro-supercapacitors. Meanwhile, the as-fabricated micro-supercapacitors have good flexibility and satisfactory energy-storage performance, exhibiting a high specific capacity of 37.1 F/cm³, a high energy density of 5.14 mWh/cm³, a power density of up to 0.5 W/cm³, and good stability during charge-discharge cycles and repeated bending-recovery cycles, respectively. Our micro-supercapacitors can be used as ingenious energy storage devices for future portable and wearable electronic applications.

Strain controlled ferromagnetic-ferrimagnetic transition and vacancy formation energy of defective graphene.

PubMed

Zhang, Yajun; Sahoo, Mpk; Wang, Jie

2016-09-23

Single vacancy (SV)-induced magnetism in graphene has attracted much attention motivated by its potential in achieving new functionalities. However, a much higher vacancy formation energy limits its direct application in electronic devices and the dependency of spin interaction on the strain is unclear. Here, through first-principles density-functional theory calculations, we investigate the possibility of strain engineering towards lowering vacancy formation energy and inducing new magnetic states in defective graphene. It is found that the SV-graphene undergoes a phase transition from an initial ferromagnetic state to a ferrimagnetic state under a biaxial tensile strain. At the same time, the biaxial tensile strain significantly lowers the vacancy formation energy. The charge density, density of states and band theory successfully identify the origin and underlying physics of the transition. The predicted magnetic phase transition is attributed to the strain driven spin flipping at the C-atoms nearest to the SV-site. The magnetic semiconducting graphene induced by defect and strain engineering suggests an effective way to modulate both spin and electronic degrees of freedom in future spintronic devices.

Improved Performance of Ionic Liquid Supercapacitors by using Tetracyanoborate Anions

PubMed Central

Martins, Vitor L.; Rennie, Anthony J. R.; Sanchez‐Ramirez, Nedher; Torresi, Roberto M.; Hall, Peter J.

2018-01-01

Abstract Supercapacitors are energy storage devices designed to operate at higher power densities than conventional batteries, but their energy density is still too low for many applications. Efforts are made to design new electrolytes with wider electrochemical windows than aqueous or conventional organic electrolytes in order to increase energy density. Ionic liquids (ILs) with wide electrochemical stability windows are excellent candidates to be employed as supercapacitor electrolytes. ILs containing tetracyanoborate anions [B(CN)4] offer wider electrochemical stability than conventional electrolytes and maintain a high ionic conductivity (6.9 mS cm−1). Herein, we report the use of ILs containing the [B(CN)4] anion for such an application. They presented a high maximum operating voltage of 3.7 V, and two‐electrode devices demonstrate high specific capacitances even when operating at relatively high rates (ca. 20 F g−1 @ 15 A g−1). This supercapacitor stored more energy and operated at a higher power at all rates studied when compared with cells using a commonly studied ILs. PMID:29577008

CoNi2 S4 Nanoparticle/Carbon Nanotube Sponge Cathode with Ultrahigh Capacitance for Highly Compressible Asymmetric Supercapacitor.

PubMed

Cao, Xin; He, Jin; Li, Huan; Kang, Liping; He, Xuexia; Sun, Jie; Jiang, Ruibing; Xu, Hua; Lei, Zhibin; Liu, Zong-Huai

2018-05-30

Compared with other flexible energy-storage devices, the design and construction of the compressible energy-storage devices face more difficulty because they must accommodate large strain and shape deformations. In the present work, CoNi 2 S 4 nanoparticles/3D porous carbon nanotube (CNT) sponge cathode with highly compressible property and excellent capacitance is prepared by electrodepositing CoNi 2 S 4 on CNT sponge, in which CoNi 2 S 4 nanoparticles with size among 10-15 nm are uniformly anchored on CNT, causing the cathode to show a high compression property and gives high specific capacitance of 1530 F g -1 . Meanwhile, Fe 2 O 3 /CNT sponge anode with specific capacitance of 460 F g -1 in a prolonged voltage window is also prepared by electrodepositing Fe 2 O 3 nanosheets on CNT sponge. An asymmetric supercapacitor (CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT) is assembled by using CoNi 2 S 4 /CNT sponge as positive electrode and Fe 2 O 3 /CNT sponge as negative electrode in 2 m KOH solution. It exhibits excellent energy density of up to 50 Wh kg -1 at a power density of 847 W kg -1 and excellent cycling stability at high compression. Even at a strain of 85%, about 75% of the initial capacitance is retained after 10 000 consecutive cycles. The CoNi 2 S 4 /CNT//Fe 2 O 3 /CNT device is a promising candidate for flexible energy devices due to its excellent compressibility and high energy density. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Wearable energy-dense and power-dense supercapacitor yarns enabled by scalable graphene-metallic textile composite electrodes.

PubMed

Liu, Libin; Yu, You; Yan, Casey; Li, Kan; Zheng, Zijian

2015-06-11

One-dimensional flexible supercapacitor yarns are of considerable interest for future wearable electronics. The bottleneck in this field is how to develop devices of high energy and power density, by using economically viable materials and scalable fabrication technologies. Here we report a hierarchical graphene-metallic textile composite electrode concept to address this challenge. The hierarchical composite electrodes consist of low-cost graphene sheets immobilized on the surface of Ni-coated cotton yarns, which are fabricated by highly scalable electroless deposition of Ni and electrochemical deposition of graphene on commercial cotton yarns. Remarkably, the volumetric energy density and power density of the all solid-state supercapacitor yarn made of one pair of these composite electrodes are 6.1 mWh cm(-3) and 1,400 mW cm(-3), respectively. In addition, this SC yarn is lightweight, highly flexible, strong, durable in life cycle and bending fatigue tests, and integratable into various wearable electronic devices.

Wearable energy-dense and power-dense supercapacitor yarns enabled by scalable graphene–metallic textile composite electrodes

PubMed Central

Liu, Libin; Yu, You; Yan, Casey; Li, Kan; Zheng, Zijian

2015-01-01

One-dimensional flexible supercapacitor yarns are of considerable interest for future wearable electronics. The bottleneck in this field is how to develop devices of high energy and power density, by using economically viable materials and scalable fabrication technologies. Here we report a hierarchical graphene–metallic textile composite electrode concept to address this challenge. The hierarchical composite electrodes consist of low-cost graphene sheets immobilized on the surface of Ni-coated cotton yarns, which are fabricated by highly scalable electroless deposition of Ni and electrochemical deposition of graphene on commercial cotton yarns. Remarkably, the volumetric energy density and power density of the all solid-state supercapacitor yarn made of one pair of these composite electrodes are 6.1 mWh cm−3 and 1,400 mW cm−3, respectively. In addition, this SC yarn is lightweight, highly flexible, strong, durable in life cycle and bending fatigue tests, and integratable into various wearable electronic devices. PMID:26068809

Superelastic Few-Layer Carbon Foam Made from Natural Cotton for All-Solid-State Electrochemical Capacitors.

PubMed

Lin, Tianquan; Liu, Fengxin; Xu, Feng; Bi, Hui; Du, Yahui; Tang, Yufeng; Huang, Fuqiang

2015-11-18

Flexible/stretchable devices for energy storage are essential for future wearable and flexible electronics. Electrochemical capacitors (ECs) are an important technology for supplement batteries in the energy storage and harvesting field, but they are limited by relatively low energy density. Herein, we report a superelastic foam consisting of few-layer carbon nanowalls made from natural cotton as a good scaffold to growth conductive polymer polyaniline for stretchable, lightweight, and flexible all-solid-state ECs. As-prepared superelastic bulk tubular carbon foam (surface area ∼950 m(2)/g) can withstand >90% repeated compression cycling and support >45,000 times its own weight but no damage. The flexible device has a high specific capacitance of 510 F g(-1), a specific energy of 25.5 Wh kg(-1) and a power density of 28.5 kW kg(-1) in weight of the total electrode materials and withstands 5,000 charging/discharging cycles.

Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

PubMed Central

Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; Grant, Richard P.; Monson, Todd C.

2017-01-01

Many challenges must be overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. To begin addressing these challenges (and others), we report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers. The tethered array of nanoparticles, MnO in this case, bound directly to a gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). This strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles. PMID:28287183

Preparation of 3D Architecture Graphdiyne Nanosheets for High-Performance Sodium-Ion Batteries and Capacitors.

PubMed

Wang, Kun; Wang, Ning; He, Jianjiang; Yang, Ze; Shen, Xiangyan; Huang, Changshui

2017-11-22

Here, we apply three-dimensional (3D) architecture graphdiyne nanosheet (GDY-NS) as anode materials for sodium-ion storage devices achieving high energy and power performance along with excellent cyclic ability. The contribution of 3D architecture nanostructure and intramolecular pores of the GDY-NS can substantially optimize the sodium storage behavior through the accommodated intramolecular pore, 3D interconnective porous structure, and increased activity sites to facilitate a fast sodium-ion-diffusion channel. The contribution of butadiyne linkages and the formation of a stable solid electrolyte interface layer are directly confirmed through the in situ Raman measurement. The GDY-NS-based sodium-ion batteries exhibit a stable reversible capacity of approximately 812 mAh g -1 at a current density of 0.05 A g -1 ; they maintain more than 405 mAh g -1 over 1000 cycles at a current density of 1 A g -1 . Furthermore, the sodium-ion capacitors could deliver a capacitance more than 200 F g -1 over 3000 cycles at 1 A g -1 and display an initial specific energy as high as 182.3 Wh kg -1 at a power density of 300 W kg -1 and maintain specific energy of 166 Wh kg -1 even at a power density of 15 000 W kg -1 . The high energy and power density along with excellent cyclic performance based on the GDY-NS anode offers a great potential toward application on next-generation energy storage devices.

Effect of density of localized states on the ovonic threshold switching characteristics of the amorphous GeSe films

NASA Astrophysics Data System (ADS)

Ahn, Hyung-Woo; Seok Jeong, Doo; Cheong, Byung-ki; Lee, Hosuk; Lee, Hosun; Kim, Su-dong; Shin, Sang-Yeol; Kim, Donghwan; Lee, Suyoun

2013-07-01

We investigated the effect of nitrogen (N) doping on the threshold voltage of an ovonic threshold switching device using amorphous GeSe. Using the spectroscopic ellipsometry, we found that the addition of N brought about significant changes in electronic structure of GeSe, such as the density of localized states and the band gap energy. Besides, it was observed that the characteristics of OTS devices strongly depended on the doping of N, which could be attributed to those changes in electronic structure suggesting a method to modulate the threshold voltage of the device.

Nanostructured mesoporous materials for lithium-ion battery applications

NASA Astrophysics Data System (ADS)

Balaya, P.; Saravanan, K.; Hariharan, S.; Ramar, V.; Lee, H. S.; Kuezma, M.; Devaraj, S.; Nagaraju, D. H.; Ananthanarayanan, K.; Mason, C. W.

2011-06-01

The Energy crisis happens to be one of the greatest challenges we are facing today. In this view, much effort has been made in developing new, cost effective, environmentally friendly energy conversion and storage devices. The performance of such devices is fundamentally related to material properties. Hence, innovative materials engineering is important in solving the energy crisis problem. One such innovation in materials engineering is porous materials for energy storage. Porous electrode materials for lithium-ion batteries (LIBs) offer a high degree of electrolyte-electrode wettability, thus enhancing the electrochemical activity within the material. Among the porous materials, mesoporous materials draw special attention, owing to shorter diffusion lengths for Li+ and electronic movement. Nanostructured mesoporous materials also offer better packing density compared to their nanostructured counterparts such as nanopowders, nanowires, nanotubes etc., thus opening a window for developing electrode materials with high volumetric energy densities. This would directly translate into a scenario of building batteries which are much lighter than today's commercial LIBs. In this article, the authors present a simple, soft template approach for preparing both cathode and anode materials with high packing density for LIBs. The impact of porosity on the electrochemical storage performance is highlighted.

Stimulus-Responsive Micro-Supercapacitors with Ultrahigh Energy Density and Reversible Electrochromic Window.

PubMed

Zhang, Panpan; Zhu, Feng; Wang, Faxing; Wang, Jinhui; Dong, Renhao; Zhuang, Xiaodong; Schmidt, Oliver G; Feng, Xinliang

2017-02-01

Stimulus-responsive micro-supercapacitors (SR-MSCs) with ultrahigh volumetric energy density and reversible electrochromic effect are successfully fabricated by employing a vanadium pentoxide and electrochemical exfoliated graphene-based hybrid nanopaper and viologen as electrode and stimulus-responsive material, respectively. The fabricated high-performance SR-MSCs offer new opportunities for intuitively observing the working state of energy devices without the aid of extra equipment and techniques. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Surface State Density Determines the Energy Level Alignment at Hybrid Perovskite/Electron Acceptors Interfaces.

PubMed

Zu, Fengshuo; Amsalem, Patrick; Ralaiarisoa, Maryline; Schultz, Thorsten; Schlesinger, Raphael; Koch, Norbert

2017-11-29

Substantial variations in the electronic structure and thus possibly conflicting energetics at interfaces between hybrid perovskites and charge transport layers in solar cells have been reported by the research community. In an attempt to unravel the origin of these variations and enable reliable device design, we demonstrate that donor-like surface states stemming from reduced lead (Pb 0 ) directly impact the energy level alignment at perovskite (CH 3 NH 3 PbI 3-x Cl x ) and molecular electron acceptor layer interfaces using photoelectron spectroscopy. When forming the interfaces, it is found that electron transfer from surface states to acceptor molecules occurs, leading to a strong decrease in the density of ionized surface states. As a consequence, for perovskite samples with low surface state density, the initial band bending at the pristine perovskite surface can be flattened upon interface formation. In contrast, for perovskites with a high surface state density, the Fermi level is strongly pinned at the conduction band edge, and only minor changes in surface band bending are observed upon acceptor deposition. Consequently, depending on the initial perovskite surface state density, very different interface energy level alignment situations (variations over 0.5 eV) are demonstrated and rationalized. Our findings help explain the rather dissimilar reported energy levels at interfaces with perovskites, refining our understanding of the operating principles in devices comprising this material.

Flexible asymmetric supercapacitors with high energy and high power density in aqueous electrolytes

NASA Astrophysics Data System (ADS)

Cheng, Yingwen; Zhang, Hongbo; Lu, Songtao; Varanasi, Chakrapani V.; Liu, Jie

2013-01-01

Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s-1 to 500 mV s-1. Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg-1) under high power density (7.8 kW kg-1) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required.Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO2, activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s-1 to 500 mV s-1. Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg-1) under high power density (7.8 kW kg-1) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required. Electronic supplementary information (ESI) available. See DOI: 10.1039/c2nr33136e

Rapid and semi-analytical design and simulation of a toroidal magnet made with YBCO and MgB 2 superconductors

DOE PAGES

Dimitrov, I. K.; Zhang, X.; Solovyov, V. F.; ...

2015-07-07

Recent advances in second-generation (YBCO) high-temperature superconducting wire could potentially enable the design of super high performance energy storage devices that combine the high energy density of chemical storage with the high power of superconducting magnetic storage. However, the high aspect ratio and the considerable filament size of these wires require the concomitant development of dedicated optimization methods that account for the critical current density in type-II superconductors. In this study, we report on the novel application and results of a CPU-efficient semianalytical computer code based on the Radia 3-D magnetostatics software package. Our algorithm is used to simulate andmore » optimize the energy density of a superconducting magnetic energy storage device model, based on design constraints, such as overall size and number of coils. The rapid performance of the code is pivoted on analytical calculations of the magnetic field based on an efficient implementation of the Biot-Savart law for a large variety of 3-D “base” geometries in the Radia package. The significantly reduced CPU time and simple data input in conjunction with the consideration of realistic input variables, such as material-specific, temperature, and magnetic-field-dependent critical current densities, have enabled the Radia-based algorithm to outperform finite-element approaches in CPU time at the same accuracy levels. Comparative simulations of MgB 2 and YBCO-based devices are performed at 4.2 K, in order to ascertain the realistic efficiency of the design configurations.« less

Simulation of electric vehicles with hybrid power systems

NASA Astrophysics Data System (ADS)

Burke, A. F.; Cole, G. H.

Computer programs for the simulation of the operation of electric vehicles with hybrid power systems are described. These programs treat cases in which high energy density ultracapacitors or high power density pulse batteries are used to load level the main energy storage battery in the vehicle. A generalized control strategy for splitting the power between the main battery and the pulse power devices is implemented such that the user can specify the nominal battery power as a function of the state-of-charge of the ultracapacitor or pulse power battery. The programs display graphically on the screen, as they run, the power from both the main battery and the pulse power device and the state-of-charge of the pulse power device. After each run is completed, a summary is printed out from which the effect of load leveling the battery on vehicle range and energy consumption can be determined. Default input files are provided with the programs so various combinations of vehicles, driveline components, and batteries of special current interest to the EV community can be run with either type of pulse power device. Typical simulation results are shown including cases in which the pulse power devices are connected in parallel with the main battery without interface electronics.

Molecular solar thermal energy storage in photoswitch oligomers increases energy densities and storage times.

PubMed

Mansø, Mads; Petersen, Anne Ugleholdt; Wang, Zhihang; Erhart, Paul; Nielsen, Mogens Brøndsted; Moth-Poulsen, Kasper

2018-05-16

Molecular photoswitches can be used for solar thermal energy storage by photoisomerization into high-energy, meta-stable isomers; we present a molecular design strategy leading to photoswitches with high energy densities and long storage times. High measured energy densities of up to 559 kJ kg -1 (155 Wh kg -1 ), long storage lifetimes up to 48.5 days, and high quantum yields of conversion of up to 94% per subunit are demonstrated in norbornadiene/quadricyclane (NBD/QC) photo-/thermoswitch couples incorporated into dimeric and trimeric structures. By changing the linker unit between the NBD units, we can at the same time fine-tune light-harvesting and energy densities of the dimers and trimers so that they exceed those of their monomeric analogs. These new oligomers thereby meet several of the criteria to be met for an optimum molecule to ultimately enter actual devices being able to undergo closed cycles of solar light-harvesting, energy storage, and heat release.

Flexible solid-state supercapacitors based on carbon nanoparticles/MnO2 nanorods hybrid structure.

PubMed

Yuan, Longyan; Lu, Xi-Hong; Xiao, Xu; Zhai, Teng; Dai, Junjie; Zhang, Fengchao; Hu, Bin; Wang, Xue; Gong, Li; Chen, Jian; Hu, Chenguo; Tong, Yexiang; Zhou, Jun; Wang, Zhong Lin

2012-01-24

A highly flexible solid-state supercapacitor was fabricated through a simple flame synthesis method and electrochemical deposition process based on a carbon nanoparticles/MnO(2) nanorods hybrid structure using polyvinyl alcohol/H(3)PO(4) electrolyte. Carbon fabric is used as a current collector and electrode (mechanical support), leading to a simplified, highly flexible, and lightweight architecture. The device exhibited good electrochemical performance with an energy density of 4.8 Wh/kg at a power density of 14 kW/kg, and a demonstration of a practical device is also presented, highlighting the path for its enormous potential in energy management. © 2011 American Chemical Society

Device and method for electron beam heating of a high density plasma

DOEpatents

Thode, Lester E.

1981-01-01

A device and method for relativistic electron beam heating of a high density plasma in a small localized region. A relativistic electron beam generator produces a high voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target plasma is ionized prior to application of the electron beam by means of a laser or other preionization source. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region within the high density plasma target.

Electrokinetic Supercapacitor for Simultaneous Harvesting and Storage of Mechanical Energy.

PubMed

Yang, Peihua; Qu, Xiaopeng; Liu, Kang; Duan, Jiangjiang; Li, Jia; Chen, Qian; Xue, Guobin; Xie, Wenke; Xu, Zhimou; Zhou, Jun

2018-03-07

Energy harvesting and storage are two distinct processes that are generally achieved using two separated parts based on different physical and chemical principles. Here we report a self-charging electrokinetic supercapacitor that directly couples the energy harvesting and storage processes into one device. The device consists of two identical carbon nanotube/titanium electrodes, separated by a piece of anodic aluminum oxide nanochannels membrane. Pressure-driven electrolyte flow through the nanochannels generates streaming potential, which can be used to charge the capacitive electrodes, accomplishing simultaneous energy generation and storage. The device stores electric charge density of 0.4 mC cm -2 after fully charging under pressure of 2.5 bar. This work may offer a train of thought for the development of a new type of energy unit for self-powered systems.

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array.

PubMed

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao; Luo, Hang

2018-02-01

Polymer-based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400-600 kV mm -1 , which may bring more challenges relating to the failure probability. Here, a simple two-step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm -3 is achieved at low electric fields, i.e., 143 kV mm -1 , which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm -2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis.

Process for producing carbon foams for energy storage devices

DOEpatents

Kaschmitter, James L.; Mayer, Steven T.; Pekala, Richard W.

1998-01-01

A high energy density capacitor incorporating a variety of carbon foam electrodes is described. The foams, derived from the pyrolysis of resorcinol-formaldehyde and related polymers, are high density (0.1 g/cc-1.0 g/cc) electrically conductive and have high surface areas (400 m.sup.2 /g-1000 m.sup.2 /g). Capacitances on the order of several tens of farad per gram of electrode are achieved.

Carbon foams for energy storage devices

DOEpatents

Kaschmitter, J.L.; Mayer, S.T.; Pekala, R.W.

1996-06-25

A high energy density capacitor incorporating a variety of carbon foam electrodes is described. The foams, derived from the pyrolysis of resorcinol-formaldehyde and related polymers, are high density (0.1 g/cc--1.0 g/cc) electrically conductive and have high surface areas (400 m{sup 2}/g-1000 m{sup 2}/g). Capacitances on the order of several tens of farad per gram of electrode are achieved. 9 figs.

Biredox ionic liquids with solid-like redox density in the liquid state for high-energy supercapacitors.

PubMed

Mourad, Eléonore; Coustan, Laura; Lannelongue, Pierre; Zigah, Dodzi; Mehdi, Ahmad; Vioux, André; Freunberger, Stefan A; Favier, Frédéric; Fontaine, Olivier

2017-04-01

Kinetics of electrochemical reactions are several orders of magnitude slower in solids than in liquids as a result of the much lower ion diffusivity. Yet, the solid state maximizes the density of redox species, which is at least two orders of magnitude lower in liquids because of solubility limitations. With regard to electrochemical energy storage devices, this leads to high-energy batteries with limited power and high-power supercapacitors with a well-known energy deficiency. For such devices the ideal system should endow the liquid state with a density of redox species close to the solid state. Here we report an approach based on biredox ionic liquids to achieve bulk-like redox density at liquid-like fast kinetics. The cation and anion of these biredox ionic liquids bear moieties that undergo very fast reversible redox reactions. As a first demonstration of their potential for high-capacity/high-rate charge storage, we used them in redox supercapacitors. These ionic liquids are able to decouple charge storage from an ion-accessible electrode surface, by storing significant charge in the pores of the electrodes, to minimize self-discharge and leakage current as a result of retaining the redox species in the pores, and to raise working voltage due to their wide electrochemical window.

Design of activated carbon/activated carbon asymmetric capacitors

NASA Astrophysics Data System (ADS)

Piñeiro-Prado, Isabel; Salinas-Torres, David; Ruiz Rosas, Ramiro; Morallon, Emilia; Cazorla-Amoros, Diego

2016-03-01

Supercapacitors are energy storage devices that offer a high power density and a low energy density in comparison with batteries. Their limited energy density can be overcome by using asymmetric configuration in mass electrodes, where each electrode works within their maximum available potential window, rendering the maximum voltage output of the system. Such asymmetric capacitors must be optimized through careful electrochemical characterization of the electrodes for accurate determination of the capacitance and the potential stability limits. The results of the characterization are then used for optimizing mass ratio of the electrodes from the balance of stored charge. The reliability of the design largely depends on the approach taken for the electrochemical characterization. Therefore, the performance could be lower than expected and even the system could break down, if a well thought out procedure is not followed. In this work, a procedure for the development of asymmetric supercapacitors based on activated carbons is detailed. Three activated carbon materials with different textural properties and surface chemistry have been systematically characterized in neutral aqueous electrolyte. The asymmetric configuration of the masses of both electrodes in the supercapacitor has allowed to cover a higher potential window, resulting in an increase of the energy density of the three devices studied when compared with the symmetric systems, and an improved cycle life.

A Low-Cost Neutral Zinc-Iron Flow Battery with High Energy Density for Stationary Energy Storage.

PubMed

Xie, Congxin; Duan, Yinqi; Xu, Wenbin; Zhang, Huamin; Li, Xianfeng

2017-11-20

Flow batteries (FBs) are one of the most promising stationary energy-storage devices for storing renewable energy. However, commercial progress of FBs is limited by their high cost and low energy density. A neutral zinc-iron FB with very low cost and high energy density is presented. By using highly soluble FeCl 2 /ZnBr 2 species, a charge energy density of 56.30 Wh L -1 can be achieved. DFT calculations demonstrated that glycine can combine with iron to suppress hydrolysis and crossover of Fe 3+ /Fe 2+ . The results indicated that an energy efficiency of 86.66 % can be obtained at 40 mA cm -2 and the battery can run stably for more than 100 cycles. Furthermore, a low-cost porous membrane was employed to lower the capital cost to less than $ 50 per kWh, which was the lowest value that has ever been reported. Combining the features of low cost, high energy density and high energy efficiency, the neutral zinc-iron FB is a promising candidate for stationary energy-storage applications. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Flexible Nb2O5 nanowires/graphene film electrode for high-performance hybrid Li-ion supercapacitors

NASA Astrophysics Data System (ADS)

Song, Hao; Fu, Jijiang; Ding, Kang; Huang, Chao; Wu, Kai; Zhang, Xuming; Gao, Biao; Huo, Kaifu; Peng, Xiang; Chu, Paul K.

2016-10-01

The hybrid Li-ion electrochemical supercapacitor (Li-HSC) combining the battery-like anode with capacitive cathode is a promising energy storage device boasting large energy and power densities. Orthorhombic Nb2O5 is a good anode material in Li-HSCs because of its large pseudocapacitive Li-ion intercalation capacity. Herein, we report a high-performance, binder-free and flexible anode consisting of long Nb2O5 nanowires and graphene (L-Nb2O5 NWs/rGO). The paper-like L-Nb2O5 NWs/rGO film electrode has a large mass loading of Nb2O5 of 93.5 wt% as well as short solid-state ion diffusion length, and enhanced conductivity (5.1 S cm-1). The hybrid L-Nb2O5 NWs/rGO paper electrode shows a high reversible specific capacity of 160 mA h g-1 at a current density of 0.2 A g-1, superior rate capability with capacitance retention of 60% when the current density increases from 0.2 to 5 A g-1, as well as excellent cycle stability. The Li-HSC device based on the L-Nb2O5/rGO anode and the cathode of biomass-derived carbon nanosheets delivers an energy density of 106 Wh kg-1 at 580 W kg-1 and 32 Wh kg-1 at a large power density of 14 kW kg-1. Moreover, the Li-HSC device exhibits excellent cycling performance without obvious capacitance decay after 1000 cycles.

High-energy green supercapacitor driven by ionic liquid electrolytes as an ultra-high stable next-generation energy storage device

NASA Astrophysics Data System (ADS)

Thangavel, Ranjith; Kannan, Aravindaraj G.; Ponraj, Rubha; Thangavel, Vigneysh; Kim, Dong-Won; Lee, Yun-Sung

2018-04-01

Development of supercapacitors with high energy density and long cycle life using sustainable materials for next-generation applications is of paramount importance. The ongoing challenge is to elevate the energy density of supercapacitors on par with batteries, while upholding the power and cyclability. In addition, attaining such superior performance with green and sustainable bio-mass derived compounds is very crucial to address the rising environmental concerns. Herein, we demonstrate the use of watermelon rind, a bio-waste from watermelons, towards high energy, and ultra-stable high temperature green supercapacitors with a high-voltage ionic liquid electrolyte. Supercapacitors assembled with ultra-high surface area, hierarchically porous carbon exhibits a remarkable performance both at room temperature and at high temperature (60 °C) with maximum energy densities of ∼174 Wh kg-1 (25 °C), and 177 Wh kg-1 (60 °C) - based on active mass of both electrodes. Furthermore, an ultra-high specific power of ∼20 kW kg-1 along with an ultra-stable cycling performance with 90% retention over 150,000 cycles has been achieved even at 60 °C, outperforming supercapacitors assembled with other carbon based materials. These results demonstrate the potential to develop high-performing, green energy storage devices using eco-friendly materials for next generation electric vehicles and other advanced energy storage systems.

Unleashing the Power and Energy of LiFePO4-Based Redox Flow Lithium Battery with a Bifunctional Redox Mediator.

PubMed

Zhu, Yun Guang; Du, Yonghua; Jia, Chuankun; Zhou, Mingyue; Fan, Li; Wang, Xingzhu; Wang, Qing

2017-05-10

Redox flow batteries, despite great operation flexibility and scalability for large-scale energy storage, suffer from low energy density and relatively high cost as compared to the state-of-the-art Li-ion batteries. Here we report a redox flow lithium battery, which operates via the redox targeting reactions of LiFePO 4 with a bifunctional redox mediator, 2,3,5,6-tetramethyl-p-phenylenediamine, and presents superb energy density as the Li-ion battery and system flexibility as the redox flow battery. The battery has achieved a tank energy density as high as 1023 Wh/L, power density of 61 mW/cm 2 , and voltage efficiency of 91%. Operando X-ray absorption near-edge structure measurements were conducted to monitor the evolution of LiFePO 4 , which provides insightful information on the redox targeting process, critical to the device operation and optimization.

A novel high-density power energy harvesting methodology for transmission line online monitoring devices.

PubMed

Liu, Yadong; Xie, Xiaolei; Hu, Yue; Qian, Yong; Sheng, Gehao; Jiang, Xiuchen; Liu, Yilu

2016-07-01

This paper presents a novel energy-harvesting model which takes the primary current, secondary turns, dimension, the magnitude of magnetic flux density B, and the core loss resistance into consideration systematically. The relationship among the potential maximum output power, the dimension of energy harvesting coil (EHC), the load type of EHC, and the secondary turns is predicted by theoretical analysis and further verified by experiments. A high power density harvester is also developed and tested. It is shown that the power density of this novel harvester is 0.7 mW/g at 10 A, which is more than 2 times powerful than the traditional ones. Hence, it could lighten the half weight of the harvester at the same conditions.

Electrochemical energy storage in montmorillonite K10 clay based composite as supercapacitor using ionic liquid electrolyte.

PubMed

Maiti, Sandipan; Pramanik, Atin; Chattopadhyay, Shreyasi; De, Goutam; Mahanty, Sourindra

2016-02-15

Exploring new electrode materials is the key to realize high performance energy storage devices for effective utilization of renewable energy. Natural clays with layered structure and high surface area are prospective materials for electrical double layer capacitors (EDLC). In this work, a novel hybrid composite based on acid-leached montmorillonite (K10), multi-walled carbon nanotube (MWCNT) and manganese dioxide (MnO2) was prepared and its electrochemical properties were investigated by fabricating two-electrode asymmetric supercapacitor cells against activated carbon (AC) using 1.0M tetraethylammonium tetrafluroborate (Et4NBF4) in acetonitrile (AN) as electrolyte. The asymmetric supercapacitors, capable of operating in a wide potential window of 0.0-2.7V, showed a high energy density of 171Whkg(-1) at a power density of ∼1.98kWkg(-1). Such high EDLC performance could possibly be linked to the acid-base interaction of K10 through its surface hydroxyl groups with the tetraethylammonium cation [(C2H5)4N(+) or TEA(+)] of the ionic liquid electrolyte. Even at a very high power density of 96.4kWkg(-1), the cells could still deliver an energy density of 91.1Whkg(-1) exhibiting an outstanding rate capability. The present study demonstrates for the first time, the excellent potential of clay-based composites for high power energy storage device applications. Copyright © 2015 Elsevier Inc. All rights reserved.

Nano-RuO2 -Decorated Holey Graphene Composite Fibers for Micro-Supercapacitors with Ultrahigh Energy Density.

PubMed

Zhai, Shengli; Wang, Chaojun; Karahan, Huseyin Enis; Wang, Yanqing; Chen, Xuncai; Sui, Xiao; Huang, Qianwei; Liao, Xiaozhou; Wang, Xin; Chen, Yuan

2018-06-07

Compactness and versatility of fiber-based micro-supercapacitors (FMSCs) make them promising for emerging wearable electronic devices as energy storage solutions. But, increasing the energy storage capacity of microscale fiber electrodes, while retaining their high power density, remains a significant challenge. Here, this issue is addressed by incorporating ultrahigh mass loading of ruthenium oxide (RuO 2 ) nanoparticles (up to 42.5 wt%) uniformly on nanocarbon-based microfibers composed largely of holey reduced graphene oxide (HrGO) with a lower amount of single-walled carbon nanotubes as nanospacers. This facile approach involes (1) space-confined hydrothermal assembly of highly porous but 3D interconnected carbon structure, (2) impregnating wet carbon structures with aqueous Ru 3+ ions, and (3) anchoring RuO 2 nanoparticles on HrGO surfaces. Solid-state FMSCs assembled using those fibers demonstrate a specific volumetric capacitance of 199 F cm -3 at 2 mV s -1 . Fabricated FMSCs also deliver an ultrahigh energy density of 27.3 mWh cm -3 , the highest among those reported for FMSCs to date. Furthermore, integrating 20 pieces of FMSCs with two commercial flexible solar cells as a self-powering energy system, a light-emitting diode panel can be lit up stably. The current work highlights the excellent potential of nano-RuO 2 -decorated HrGO composite fibers for constructing micro-supercapacitors with high energy density for wearable electronic devices. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

3D Freeze-Casting of Cellular Graphene Films for Ultrahigh-Power-Density Supercapacitors.

PubMed

Shao, Yuanlong; El-Kady, Maher F; Lin, Cheng-Wei; Zhu, Guanzhou; Marsh, Kristofer L; Hwang, Jee Youn; Zhang, Qinghong; Li, Yaogang; Wang, Hongzhi; Kaner, Richard B

2016-08-01

3D cellular graphene films with open porosity, high electrical conductivity, and good tensile strength, can be synthesized by a method combining freeze-casting and filtration. The resulting supercapacitors based on 3D porous reduced graphene oxide (RGO) film exhibit extremely high specific power densities and high energy densities. The fabrication process provides an effective means for controlling the pore size, electronic conductivity, and loading mass of the electrode materials, toward devices with high energy-storage performance. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy storage options for space power

NASA Astrophysics Data System (ADS)

Hoffman, H. W.; Martin, J. F.; Olszewski, M.

Including energy storage in a space power supply enhances the feasibility of using thermal power cycles (Rankine or Brayton) and providing high-power pulses. Superconducting magnets, capacitors, electrochemical batteries, thermal phase-change materials (PCM), and flywheels are assessed; the results obtained suggest that flywheels and phase-change devices hold the most promise. Latent heat storage using inorganic salts and metallic eutectics offers thermal energy storage densities of 1500 kJ/kg to 2000 kJ/kg at temperatures to 1675 K. Innovative techniques allow these media to operate in direct contact with the heat engine working fluid. Enhancing thermal conductivity and/or modifying PCM crystallization habit provide other options. Flywheels of low-strain graphite and Kevlar fibers have achieved mechanical energy storage densities of 300 kJ/kg. With high-strain graphite fibers, storage densities appropriate to space power needs (about 500 kJ/kg) seem feasible. Coupling advanced flywheels with emerging high power density homopolar generators and compulsators could result in electric pulse-power storage modules of significantly higher energy density.

Room-temperature vertically-aligned copper oxide nanoblades synthesized by electrochemical restructuring of copper hydroxide nanorods: An electrode for high energy density hybrid device

NASA Astrophysics Data System (ADS)

Zhang, Xuetao; Zhou, Jinyuan; Dou, Wei; Wang, Junya; Mu, Xuemei; Zhang, Yue; Abas, Asim; Su, Qing; Lan, Wei; Xie, Erqing; Zhang, Chuanfang (John)

2018-04-01

The fast growing of portable electronics has greatly stimulated the development of energy storage materials, such as transition metal oxides (TMOs). However, TMOs usually involve harsh synthesis conditions, such as high temperature. Here we take advantage of the metastable nature of Cu(OH)2 and grow CuO nanoblades (NBs) on Cu foam under the electric field at room temperature. The electrochemical polarization accelerates the dissolution of Cu(OH)2 nanorods, guides the deposition of the as-dissolved Cu(OH)42- species and eventually leads to the phase transformation of CuO NBs. The unique materials architecture render the vertically-aligned CuO NBs with enhanced electronic and ionic diffusion kinetics, high charge storage (∼779 mC cm-2 at 1 mA cm-2), excellent rate capability and long-term cycling performances. Further matching with activated carbon electrode results in high-performance hybrid device, which displays a wide voltage window (1.7 V) in aqueous electrolyte, high energy density (0.17 mWh cm-2) and power density (34 mW cm-2) coupled with long lifetime, surpassing the best CuO based device known. The hybrid device can be randomly connected and power several light-emitting diodes. Importantly, such an electrochemical restructuring approach is cost-effective, environmentally green and universal, and can be extended to synthesize other metastable hydroxides to in-situ grow corresponding oxides.

Effect of gas filling pressure and operation energy on ion and neutron emission in a medium energy plasma focus device

NASA Astrophysics Data System (ADS)

Niranjan, Ram; Rout, R. K.; Srivastava, Rohit; Kaushik, T. C.

2018-03-01

The effects of gas filling pressure and operation energy on deuterium ions and neutrons have been studied in a medium energy plasma focus device, MEPF-12. The deuterium gas filling pressure was varied from 1 to 10 mbar at an operation energy of 9.7 kJ. Also, the operation energy was varied from 3.9 to 9.7 kJ at a deuterium gas filling pressure of 4 mbar. Time resolved emission of deuterium ions was measured using a Faraday cup. Simultaneously, time integrated and time resolved emissions of neutrons were measured using a silver activation detector and plastic scintillator detector, respectively. Various characteristics (fluence, peak density, and most probable energy) of deuterium ions were estimated using the Faraday cup signal. The fluence was found to be nearly independent of the gas filling pressure and operation energy, but the peak density and most probable energy of deuterium ions were found to be varying. The neutron yield was observed to be varying with the gas filling pressure and operation energy. The effect of ions on neutrons emission was observed at each operation condition.

An aqueous electrolyte, sodium ion functional, large format energy storage device for stationary applications

NASA Astrophysics Data System (ADS)

Whitacre, J. F.; Wiley, T.; Shanbhag, S.; Wenzhuo, Y.; Mohamed, A.; Chun, S. E.; Weber, E.; Blackwood, D.; Lynch-Bell, E.; Gulakowski, J.; Smith, C.; Humphreys, D.

2012-09-01

An approach to making large format economical energy storage devices based on a sodium-interactive set of electrodes in a neutral pH aqueous electrolyte is described. The economics of materials and manufacturing are examined, followed by a description of an asymmetric/hybrid device that has λ-MnO2 positive electrode material and low cost activated carbon as the negative electrode material. Data presented include materials characterization of the active materials, cyclic voltammetry, galvanostatic charge/discharge cycling, and application-specific performance of an 80 V, 2.4 kW h pack. The results indicate that this set of electrochemical couples is stable, low cost, requires minimal battery management control electronics, and therefore has potential for use in stationary applications where device energy density is not a concern.

Studies of the Hard X-ray Emission from the Filippov Type Plasma Focus Device, Dena

NASA Astrophysics Data System (ADS)

Tafreshi, M. A.; Saeedzadeh, E.

2006-12-01

This article is about the characteristics of the hard X-ray (HXR) emission from the Filippov type plasma focus (PF) device, Dena. The article begins with a brief presentation of Dena, and the mechanism of the HXR production in PF devices. Then using the differential absorption spectrometry, the energy resolved spectrum of the HXR emission from a 37 kJ discharge in Dena, is estimated. The energy flux density and the energy fluence of this emission have also been calculated to be 1.9 kJ cm-2 s-1 and 9.4 × 10-5 J cm-2. In the end, after presentation of radiography of sheep bones and calf ribs, the medical application of the PF devices has been discussed.

High-power-density, high-energy-density fluorinated graphene for primary lithium batteries

NASA Astrophysics Data System (ADS)

Zhong, Guiming; Chen, Huixin; Huang, Xingkang; Yue, Hongjun; Lu, Canzhong

2018-03-01

Li/CFx is one of the highest-energy-density primary batteries; however, poor rate capability hinders its practical applications in high-power devices. Here we report a preparation of fluorinated graphene (GFx) with superior performance through a direct gas fluorination. We find that the so-called “semi-ionic” C-F bond content in all C-F bonds presents a more critical impact on rate performance of the GFx in comparison with sp2 C content in the GFx, morphology, structure, and specific surface area of the materials. The rate capability remains excellent before the semi-ionic C-F bond proportion in the GFx decreases. Thus, by optimizing semi-ionic C-F content in our GFx, we obtain the optimal x of 0.8, with which the GF0.8 exhibits a very high energy density of 1073 Wh kg-1 and an excellent power density of 21460 W kg-1 at a high current density of 10 A g-1. More importantly, our approach opens a new avenue to obtain fluorinated carbon with high energy densities without compromising high power densities.

An Electrothermal Plasma Source Developed for Simulation of Transient Heat Loads in Future Large Fusion Devices

NASA Astrophysics Data System (ADS)

Gebhart, Trey; Baylor, Larry; Winfrey, Leigh

2016-10-01

The realization of fusion energy requires materials that can withstand high heat and particle fluxes at the plasma material interface. In this work, an electrothermal (ET) plasma source has been designed as a possible transient heat flux source for a linear plasma material interaction device. An ET plasma source operates in the ablative arc regime, which is driven by a DC capacitive discharge. The current travels through the 4mm bore of a boron nitride liner and subsequently ablates and ionizes the liner material. This results in a high density plasma with a large unidirectional bulk flow out of the source exit. The pulse length for the ET source has been optimized using a pulse forming network to have a duration of 1ms at full-width half maximum. The peak currents and maximum source energies seen in this system are 2kA and 5kJ. The goal of this work is to show that the ET source produces electron densities and heat fluxes that are comparable to transient events in future large magnetic confinement fusion devices. Heat flux, plasma temperature, and plasma density were determined for each test shot using infrared imaging and optical spectroscopy techniques. This work will compare the ET source output (heat flux, temperature, and density) with and without an applied magnetic field. Research sponsored by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the U. S. Department of Energy.

Nanoscale temperature mapping in operating microelectronic devices

DOE PAGES

Mecklenburg, Matthew; Hubbard, William A.; White, E. R.; ...

2015-02-05

We report that modern microelectronic devices have nanoscale features that dissipate power nonuniformly, but fundamental physical limits frustrate efforts to detect the resulting temperature gradients. Contact thermometers disturb the temperature of a small system, while radiation thermometers struggle to beat the diffraction limit. Exploiting the same physics as Fahrenheit’s glass-bulb thermometer, we mapped the thermal expansion of Joule-heated, 80-nanometer-thick aluminum wires by precisely measuring changes in density. With a scanning transmission electron microscope (STEM) and electron energy loss spectroscopy (EELS), we quantified the local density via the energy of aluminum’s bulk plasmon. Rescaling density to temperature yields maps with amore » statistical precision of 3 kelvin/hertz ₋1/2, an accuracy of 10%, and nanometer-scale resolution. Lastly, many common metals and semiconductors have sufficiently sharp plasmon resonances to serve as their own thermometers.« less

Flat panel ferroelectric electron emission display system

DOEpatents

Sampayan, Stephen E.; Orvis, William J.; Caporaso, George J.; Wieskamp, Ted F.

1996-01-01

A device which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density.

Charge storage mechanism in nanoporous carbons and its consequence for electrical double layer capacitors.

PubMed

Simon, Patrice; Gogotsi, Yury

2010-07-28

Electrochemical capacitors, also known as supercapacitors, are energy storage devices that fill the gap between batteries and dielectric capacitors. Thanks to their unique features, they have a key role to play in energy storage and harvesting, acting as a complement to or even a replacement of batteries which has already been achieved in various applications. One of the challenges in the supercapacitor area is to increase their energy density. Some recent discoveries regarding ion adsorption in microporous carbon exhibiting pores in the nanometre range can help in designing the next generation of high-energy-density supercapacitors.

Process for producing carbon foams for energy storage devices

DOEpatents

Kaschmitter, J.L.; Mayer, S.T.; Pekala, R.W.

1998-08-04

A high energy density capacitor incorporating a variety of carbon foam electrodes is described. The foams, derived from the pyrolysis of resorcinol-formaldehyde and related polymers, are high density (0.1 g/cc--1.0 g/cc) electrically conductive and have high surface areas (400 m{sup 2}/g--1,000 m{sup 2}/g). Capacitances on the order of several tens of farad per gram of electrode are achieved. 9 figs.

A single-walled carbon nanotubes/poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)/copper hexacyanoferrate hybrid film for high-volumetric performance flexible supercapacitors

NASA Astrophysics Data System (ADS)

Li, Jianmin; Li, Haizeng; Li, Jiahui; Wu, Guiqing; Shao, Yuanlong; Li, Yaogang; Zhang, Qinghong; Wang, Hongzhi

2018-05-01

Volumetric energy density is generally considered to be detrimental to the actual application of supercapacitors, which has provoked a range of research work on increasing the packing density of electrodes. Herein, we fabricate a free-standing single-walled carbon nanotubes (SWCNTs)/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)/copper hexacyanoferrate (CuHCF) nanoparticles (NPs) composite supercapacitor electrode, with a high packing density of 2.67 g cm-3. The pseudocapacitive CuHCF NPs are decorated onto the SWCNTs/PEDOT:PSS networks and filled in interspace to increase both of packing density and specific capacitance. This hybrid electrode exhibits a series of outstanding performances, such as high electric conductivity, ultrahigh areal and volumetric capacitances (969.8 mF cm-2 and 775.2 F cm-3 at scan rate of 5 mV s-1), long cycle life and superior rate capability. The asymmetric supercapacitor built by using the SWCNTs/PEDOT:PSS/CuHCF film as positive electrode and Mo-doped WO3/SWCNTs film as negative electrode, can deliver a high energy density of 30.08 Wh L-1 with a power density of 4.25 kW L-1 based on the total volume of the device. The approach unveiled in this study could provide important insights to improving the volumetric performance of energy storage devices and help to reach the critical targets for high rate and high power density demand applications.

Probability density of tunneled carrier states near heterojunctions calculated numerically by the scattering method.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wampler, William R.; Myers, Samuel M.; Modine, Normand A.

2017-09-01

The energy-dependent probability density of tunneled carrier states for arbitrarily specified longitudinal potential-energy profiles in planar bipolar devices is numerically computed using the scattering method. Results agree accurately with a previous treatment based on solution of the localized eigenvalue problem, where computation times are much greater. These developments enable quantitative treatment of tunneling-assisted recombination in irradiated heterojunction bipolar transistors, where band offsets may enhance the tunneling effect by orders of magnitude. The calculations also reveal the density of non-tunneled carrier states in spatially varying potentials, and thereby test the common approximation of uniform- bulk values for such densities.

Peapod-like Li3 VO4 /N-Doped Carbon Nanowires with Pseudocapacitive Properties as Advanced Materials for High-Energy Lithium-Ion Capacitors.

PubMed

Shen, Laifa; Lv, Haifeng; Chen, Shuangqiang; Kopold, Peter; van Aken, Peter A; Wu, Xiaojun; Maier, Joachim; Yu, Yan

2017-07-01

Lithium ion capacitors are new energy storage devices combining the complementary features of both electric double-layer capacitors and lithium ion batteries. A key limitation to this technology is the kinetic imbalance between the Faradaic insertion electrode and capacitive electrode. Here, we demonstrate that the Li 3 VO 4 with low Li-ion insertion voltage and fast kinetics can be favorably used for lithium ion capacitors. N-doped carbon-encapsulated Li 3 VO 4 nanowires are synthesized through a morphology-inheritance route, displaying a low insertion voltage between 0.2 and 1.0 V, a high reversible capacity of ≈400 mAh g -1 at 0.1 A g -1 , excellent rate capability, and long-term cycling stability. Benefiting from the small nanoparticles, low energy diffusion barrier and highly localized charge-transfer, the Li 3 VO 4 /N-doped carbon nanowires exhibit a high-rate pseudocapacitive behavior. A lithium ion capacitor device based on these Li 3 VO 4 /N-doped carbon nanowires delivers a high energy density of 136.4 Wh kg -1 at a power density of 532 W kg -1 , revealing the potential for application in high-performance and long life energy storage devices. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

High energy density propulsion systems and small engine dynamometer

NASA Astrophysics Data System (ADS)

Hays, Thomas

2009-07-01

Scope and Method of Study. This study investigates all possible methods of powering small unmanned vehicles, provides reasoning for the propulsion system down select, and covers in detail the design and production of a dynamometer to confirm theoretical energy density calculations for small engines. Initial energy density calculations are based upon manufacturer data, pressure vessel theory, and ideal thermodynamic cycle efficiencies. Engine tests are conducted with a braking type dynamometer for constant load energy density tests, and show true energy densities in excess of 1400 WH/lb of fuel. Findings and Conclusions. Theory predicts lithium polymer, the present unmanned system energy storage device of choice, to have much lower energy densities than other conversion energy sources. Small engines designed for efficiency, instead of maximum power, would provide the most advantageous method for powering small unmanned vehicles because these engines have widely variable power output, loss of mass during flight, and generate rotational power directly. Theoretical predictions for the energy density of small engines has been verified through testing. Tested values up to 1400 WH/lb can be seen under proper operating conditions. The implementation of such a high energy density system will require a significant amount of follow-on design work to enable the engines to tolerate the higher temperatures of lean operation. Suggestions are proposed to enable a reliable, small-engine propulsion system in future work. Performance calculations show that a mature system is capable of month long flight times, and unrefueled circumnavigation of the globe.

Special Issue: Materials for Electrochemical Capacitors and Batteries.

PubMed

Wang, Jian-Gan; Wei, Bingqing

2017-04-22

Electrochemical capacitors and rechargeable batteries have received worldwide attention due to their excellent energy storage capability for a variety of applications. The rapid development of these technologies is propelled by the advanced electrode materials and new energy storage systems. It is believed that research efforts can improve the device performance to meet the ever-increasing requirements of high energy density, high power density and long cycle life. This Special Issue aims to provide readers with a glimpse of different kinds of electrode materials for electrochemical capacitors and batteries.

Helically coiled carbon nanotube forests for use as electrodes in supercapacitors

NASA Astrophysics Data System (ADS)

Childress, Anthony; Ferri, Kevin; Podila, Ramakrishna; Rao, Apparao

Supercapacitors are a class of devices which combine the high energy density of batteries with the power delivery of capacitors, and have benefitted greatly from the incorporation of carbon nanomaterials. In an effort to improve the specific capacitance of these devices, we have produced binder-free electrodes composed of helically coiled carbon nanotube forests grown on stainless steel current collectors with a performance superior to traditional carbon nanomaterials. By virtue of their helicity, the coiled nanotubes provide a greater surface area for energy storage than their straight counterparts, thus improving the specific capacitance. Furthermore, we used an Ar plasma treatment to increase the electronic density of states, and thereby the quantum capacitance, through the introduction of defects.

Wrapping Aligned Carbon Nanotube Composite Sheets around Vanadium Nitride Nanowire Arrays for Asymmetric Coaxial Fiber-Shaped Supercapacitors with Ultrahigh Energy Density.

PubMed

Zhang, Qichong; Wang, Xiaona; Pan, Zhenghui; Sun, Juan; Zhao, Jingxin; Zhang, Jun; Zhang, Cuixia; Tang, Lei; Luo, Jie; Song, Bin; Zhang, Zengxing; Lu, Weibang; Li, Qingwen; Zhang, Yuegang; Yao, Yagang

2017-04-12

The emergence of fiber-shaped supercapacitors (FSSs) has led to a revolution in portable and wearable electronic devices. However, obtaining high energy density FSSs for practical applications is still a key challenge. This article exhibits a facile and effective approach to directly grow well-aligned three-dimensional vanadium nitride (VN) nanowire arrays (NWAs) on carbon nanotube (CNT) fiber with an ultrahigh specific capacitance of 715 mF/cm 2 in a three-electrode system. Benefiting from their intriguing structural features, we successfully fabricated a prototype asymmetric coaxial FSS (ACFSS) with a maximum operating voltage of 1.8 V. From core to shell, this ACFSS consists of a CNT fiber core coated with VN@C NWAs as the negative electrode, Na 2 SO 4 poly(vinyl alcohol) (PVA) as the solid electrolyte, and MnO 2 /conducting polymer/CNT sheets as the positive electrode. The novel coaxial architecture not only fully enables utilization of the effective surface area and decreases the contact resistance between the two electrodes but also, more importantly, provides a short pathway for the ultrafast transport of axial electrons and ions. The electrochemical results show that the optimized ACFSS exhibits a remarkable specific capacitance of 213.5 mF/cm 2 and an exceptional energy density of 96.07 μWh/cm 2 , the highest areal capacitance and areal energy density yet reported in FSSs. Furthermore, the device possesses excellent flexibility in that its capacitance retention reaches 96.8% after bending 5000 times, which further allows it to be woven into flexible electronic clothes with conventional weaving techniques. Therefore, the asymmetric coaxial architectural design allows new opportunities to fabricate high-performance flexible FSSs for future portable and wearable electronic devices.

A binder-free wet chemical synthesis approach to decorate nanoflowers of bismuth oxide on Ni-foam for fabricating laboratory scale potential pencil-type asymmetric supercapacitor device.

PubMed

Shinde, N M; Xia, Qi Xun; Yun, Je Moon; Singh, Saurabh; Mane, Rajaram S; Kim, Kwang-Ho

2017-05-23

The present study involves the synthesis of a bismuth oxide (Bi 2 O 3 ) electrode consisting of an arranged nano-platelets for evolving a flower-type surface appearance on nickel-foam (Bi 2 O 3 -Ni-F) by a simple, inexpensive, binder-free and one-step chemical bath deposition (CBD) method, popularly known as a wet chemical method. The as-prepared Bi 2 O 3 on Ni-foam, as an electrode material, demonstrates 557 F g -1 specific capacitance (SC, at 1 mA cm -2 ), of which 85% is retained even after 2000 cycles. With specific power density of 500 kW kg -1 , the Bi 2 O 3 -Ni-F electrode documents a specific energy density of 80 Wh kg -1 . Furthermore, a portable asymmetric supercapacitor device, i.e. a pencil-type cell consisting of Bi 2 O 3 -Ni-F as an anode and graphite as a cathode in 6 M KOH aqueous electrolyte solution, confirms 11 Wh kg -1 and 720 kW kg -1 specific energy and specific power densities, respectively. An easy and a simple synthesis approach for manufacturing a portable laboratory scale pencil-type supercapacitor device is a major outcome of this study, which can also be applied for ternary and quaternary metal oxides for recording an enhanced performance. In addition, we presented a demonstration of lighting a light emitting diode (LED) using a home-made pencil-type supercapacitor device which, finally, has confirmed the scaling and technical potentiality of Bi 2 O 3 -Ni-F in energy storage devices.

Lithium-Sulfur Capacitors.

PubMed

Kim, Mok-Hwa; Kim, Hyun-Kyung; Xi, Kai; Kumar, R Vasant; Jung, Dae Soo; Kim, Kwang-Bum; Roh, Kwang Chul

2018-02-21

Although many existing hybrid energy storage systems demonstrate promising electrochemical performances, imbalances between the energies and kinetics of the two electrodes must be resolved to allow their widespread commercialization. As such, the development of a new class of energy storage systems is a particular challenge, since future systems will require a single device to provide both a high gravimetric energy and a high power density. In this context, we herein report the design of novel lithium-sulfur capacitors. The resulting asymmetric systems exhibited energy densities of 23.9-236.4 Wh kg -1 and power densities of 72.2-4097.3 W kg -1 , which are the highest reported values for an asymmetric system to date. This approach involved the use of a prelithiated anode and a hybrid cathode material exhibiting anion adsorption-desorption in addition to the electrochemical reduction and oxidation of sulfur at almost identical rates. This novel strategy yielded both high energy and power densities, and therefore establishes a new benchmark for hybrid systems.

Probing the mechanism of high capacitance in two-dimensional titanium carbide using in-situ X-Ray absorption spectroscopy

DOE PAGES

Lukatskaya, Maria R.; Bak, Seong -Min; Yu, Xiqian; ...

2015-05-28

The field of supercapacitors (electrochemical capacitors) is constantly evolving. The global motivation is to create devices that possess a significant energy density without compromising the power density. To achieve this goal, new materials must be discovered and complex electrode architectures developed.

Colonisation of fish and crabs of wave energy foundations and the effects of manufactured holes - a field experiment.

PubMed

Langhamer, Olivia; Wilhelmsson, Dan

2009-10-01

Several Western European countries are planning for a significant development of offshore renewable energy along the European Atlantic Ocean coast, including many thousands of wave energy devices and wind turbines. There is an increasing interest in articulating the added values of the creation of artificial hard bottom habitats through the construction of offshore renewable energy devices, for the benefit of fisheries management and conservation. The Lysekil Project is a test park for wave power located about 100 km north of Gothenburg at the Swedish west coast. A wave energy device consists of a linear wave power generator attached to a foundation on the seabed, and connected by a wire to a buoy at the surface. Our field experiment examined the function of wave energy foundations as artificial reefs. In addition, potentials for enhancing the abundance of associated fish and crustaceans through manufactured holes of the foundations were also investigated. Assemblages of mobile organisms were examined by visual censuses in July and August 2007, 3 months after deployment of the foundations. Results generally show low densities of mobile organisms, but a significantly higher abundance of fish and crabs on the foundations compared to surrounding soft bottoms. Further, while fish numbers were not influenced by increased habitat complexity (holes), it had a significantly positive effect on quantities of edible crab (Cancer pagurus), on average leading to an almost five-fold increase in densities of this species. Densities of spiny starfish (Marthasterias glacialis) were negatively affected by the presence of holes, potentially due to increased predator abundance (e.g. C. pagurus). These results suggest a species-specific response to enhanced habitat complexity.

A high-rate long-life Li4Ti5O12/Li[Ni0.45Co0.1Mn1.45]O4 lithium-ion battery.

PubMed

Jung, Hun-Gi; Jang, Min Woo; Hassoun, Jusef; Sun, Yang-Kook; Scrosati, Bruno

2011-11-01

Lithium batteries are receiving considerable attention as storage devices in the renewable energy and sustainable road transport fields. However, low-cost, long-life lithium batteries with higher energy densities are required to facilitate practical application. Here we report a lithium-ion battery that can be cycled at rates as high as 10 C has a life exceeding 500 cycles and an operating temperature range extending from -20 to 55 °C. The estimated energy density is 260 W h kg(-1), which is considerably higher than densities delivered by the presently available Li-ion batteries.

Device and method for relativistic electron beam heating of a high-density plasma to drive fast liners

DOEpatents

Thode, Lester E.

1981-01-01

A device and method for relativistic electron beam heating of a high-density plasma in a small localized region. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target gas is ionized prior to application of the electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy and momentum into a small localized region of the high-density plasma target. Fast liners disposed in the high-density target plasma are explosively or ablatively driven to implosion by a heated annular plasma surrounding the fast liner which is generated by an annular relativistic electron beam. An azimuthal magnetic field produced by axial current flow in the annular plasma, causes the energy in the heated annular plasma to converge on the fast liner.

High Discharge Energy Density at Low Electric Field Using an Aligned Titanium Dioxide/Lead Zirconate Titanate Nanowire Array

PubMed Central

Zhang, Dou; Liu, Weiwei; Guo, Ru; Zhou, Kechao

2017-01-01

Abstract Polymer‐based capacitors with high energy density have attracted significant attention in recent years due to their wide range of potential applications in electronic devices. However, the obtained high energy density is predominantly dependent on high applied electric field, e.g., 400–600 kV mm−1, which may bring more challenges relating to the failure probability. Here, a simple two‐step method for synthesizing titanium dioxide/lead zirconate titanate nanowire arrays is exploited and a demonstration of their ability to achieve high discharge energy density capacitors for low operating voltage applications is provided. A high discharge energy density of 6.9 J cm−3 is achieved at low electric fields, i.e., 143 kV mm−1, which is attributed to the high relative permittivity of 218.9 at 1 kHz and high polarization of 23.35 µC cm−2 at this electric field. The discharge energy density obtained in this work is the highest known for a ceramic/polymer nanocomposite at such a low electric field. The novel nanowire arrays used in this work are applicable to a wide range of fields, such as energy harvesting, energy storage, and photocatalysis. PMID:29610724

Flat panel ferroelectric electron emission display system

DOEpatents

Sampayan, S.E.; Orvis, W.J.; Caporaso, G.J.; Wieskamp, T.F.

1996-04-16

A device is disclosed which can produce a bright, raster scanned or non-raster scanned image from a flat panel. Unlike many flat panel technologies, this device does not require ambient light or auxiliary illumination for viewing the image. Rather, this device relies on electrons emitted from a ferroelectric emitter impinging on a phosphor. This device takes advantage of a new electron emitter technology which emits electrons with significant kinetic energy and beam current density. 6 figs.

Theoretical Limits of Energy Density in Silicon-Carbon Composite Anode Based Lithium Ion Batteries.

PubMed

Dash, Ranjan; Pannala, Sreekanth

2016-06-17

Silicon (Si) is under consideration as a potential next-generation anode material for the lithium ion battery (LIB). Experimental reports of up to 40% increase in energy density of Si anode based LIBs (Si-LIBs) have been reported in literature. However, this increase in energy density is achieved when the Si-LIB is allowed to swell (volumetrically expand) more than graphite based LIB (graphite-LIB) and beyond practical limits. The volume expansion of LIB electrodes should be negligible for applications such as automotive or mobile devices. We determine the theoretical bounds of Si composition in a Si-carbon composite (SCC) based anode to maximize the volumetric energy density of a LIB by constraining the external dimensions of the anode during charging. The porosity of the SCC anode is adjusted to accommodate the volume expansion during lithiation. The calculated threshold value of Si was then used to determine the possible volumetric energy densities of LIBs with SCC anode (SCC-LIBs) and the potential improvement over graphite-LIBs. The level of improvement in volumetric and gravimetric energy density of SCC-LIBs with constrained volume is predicted to be less than 10% to ensure the battery has similar power characteristics of graphite-LIBs.

Aquagel electrode separator for use in batteries and supercapacitors

DOEpatents

Mayer, Steven T.; Kaschmitter, James L.; Pekala, Richard W.

1995-01-01

An electrode separator for electrochemical energy storage devices, such as a high energy density capacitor incorporating a variety of carbon foam electrodes. The separator is derived from an aquagel of resorcinol-formaldehyde and related polymers and containing ionically conducting electrolyte in the pores thereof.

Nanoarchitectured graphene-based supercapacitors for next-generation energy-storage applications.

PubMed

Salunkhe, Rahul R; Lee, Ying-Hui; Chang, Kuo-Hsin; Li, Jing-Mei; Simon, Patrice; Tang, Jing; Torad, Nagy L; Hu, Chi-Chang; Yamauchi, Yusuke

2014-10-20

Tremendous development in the field of portable electronics and hybrid electric vehicles has led to urgent and increasing demand in the field of high-energy storage devices. In recent years, many research efforts have been made for the development of more efficient energy-storage devices such as supercapacitors, batteries, and fuel cells. In particular, supercapacitors have great potential to meet the demands of both high energy density and power density in many advanced technologies. For the last half decade, graphene has attracted intense research interest for electrical double-layer capacitor (EDLC) applications. The unique electronic, thermal, mechanical, and chemical characteristics of graphene, along with the intrinsic benefits of a carbon material, make it a promising candidate for supercapacitor applications. This Review focuses on recent research developments in graphene-based supercapacitors, including doped graphene, activated graphene, graphene/metal oxide composites, graphene/polymer composites, and graphene-based asymmetric supercapacitors. The challenges and prospects of graphene-based supercapacitors are also discussed. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Self-Assembled Array of Tethered Manganese Oxide Nanoparticles for the Next Generation of Energy Storage

DOE PAGES

Stevens, Tyler E.; Pearce, Charles J.; Whitten, Caleah N.; ...

2017-03-13

There are many challenges to overcome in order to create reliable electrochemical energy storage devices with not only high energy but also high power densities. Gaps exist in both battery and supercapacitor technologies, with neither one satisfying the need for both large power and energy densities in a single device. We report a process to create a self-assembled array of electrochemically active nanoparticles bound directly to a current collector using extremely short (2 nm or less) conductive tethers, in order to begin addressing these challenges (and others). The tethered array of nanoparticles, MnO in this case, bound directly to amore » gold current collector via short conducting linkages eliminates the need for fillers, resulting in a material which achieves 99.9% active material by mass (excluding the current collector). Our strategy is expected to be both scalable as well as effective for alternative tethers and metal oxide nanoparticles.« less

Integrated Power Adapter: Isolated Converter with Integrated Passives and Low Material Stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

None

2010-09-01

ADEPT Project: CPES at Virginia Tech is developing an extremely efficient power converter that could be used in power adapters for small, lightweight laptops and other types of mobile electronic devices. Power adapters convert electrical energy into useable power for an electronic device, and they currently waste a lot of energy when they are plugged into an outlet to power up. CPES at Virginia Tech is integrating high-density capacitors, new magnetic materials, high-frequency integrated circuits, and a constant-flux transformer to create its efficient power converter. The high-density capacitors enable the power adapter to store more energy. The new magnetic materialsmore » also increase energy storage, and they can be precisely dispensed using a low-cost ink-jet printer which keeps costs down. The high-frequency integrated circuits can handle more power, and they can handle it more efficiently. And, the constant-flux transformer processes a consistent flow of electrical current, which makes the converter more efficient.« less

AlGaN UV LED and Photodiodes Radiation Hardness and Space Qualifications and Their Applications in Space Science and High Energy Density Physics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sun, K. X.

2011-05-31

This presentation provides an overview of robust, radiation hard AlGaN optoelectronic devices and their applications in space exploration & high energy density physics. Particularly, deep UV LED and deep UV photodiodes are discussed with regard to their applications, radiation hardness and space qualification. AC charge management of UV LED satellite payload instruments, which were to be launched in late 2012, is covered.

An LDPC Decoder Architecture for Wireless Sensor Network Applications

PubMed Central

Giancarlo Biroli, Andrea Dario; Martina, Maurizio; Masera, Guido

2012-01-01

The pervasive use of wireless sensors in a growing spectrum of human activities reinforces the need for devices with low energy dissipation. In this work, coded communication between a couple of wireless sensor devices is considered as a method to reduce the dissipated energy per transmitted bit with respect to uncoded communication. Different Low Density Parity Check (LDPC) codes are considered to this purpose and post layout results are shown for a low-area low-energy decoder, which offers percentage energy savings with respect to the uncoded solution in the range of 40%–80%, depending on considered environment, distance and bit error rate. PMID:22438724

An LDPC decoder architecture for wireless sensor network applications.

PubMed

Biroli, Andrea Dario Giancarlo; Martina, Maurizio; Masera, Guido

2012-01-01

The pervasive use of wireless sensors in a growing spectrum of human activities reinforces the need for devices with low energy dissipation. In this work, coded communication between a couple of wireless sensor devices is considered as a method to reduce the dissipated energy per transmitted bit with respect to uncoded communication. Different Low Density Parity Check (LDPC) codes are considered to this purpose and post layout results are shown for a low-area low-energy decoder, which offers percentage energy savings with respect to the uncoded solution in the range of 40%-80%, depending on considered environment, distance and bit error rate.

Scalable 2D Hierarchical Porous Carbon Nanosheets for Flexible Supercapacitors with Ultrahigh Energy Density.

PubMed

Yao, Lei; Wu, Qin; Zhang, Peixin; Zhang, Junmin; Wang, Dongrui; Li, Yongliang; Ren, Xiangzhong; Mi, Hongwei; Deng, Libo; Zheng, Zijian

2018-03-01

2D carbon nanomaterials such as graphene and its derivatives, have gained tremendous research interests in energy storage because of their high capacitance and chemical stability. However, scalable synthesis of ultrathin carbon nanosheets with well-defined pore architectures remains a great challenge. Herein, the first synthesis of 2D hierarchical porous carbon nanosheets (2D-HPCs) with rich nitrogen dopants is reported, which is prepared with high scalability through a rapid polymerization of a nitrogen-containing thermoset and a subsequent one-step pyrolysis and activation into 2D porous nanosheets. 2D-HPCs, which are typically 1.5 nm thick and 1-3 µm wide, show a high surface area (2406 m 2 g -1 ) and with hierarchical micro-, meso-, and macropores. This 2D and hierarchical porous structure leads to robust flexibility and good energy-storage capability, being 139 Wh kg -1 for a symmetric supercapacitor. Flexible supercapacitor devices fabricated by these 2D-HPCs also present an ultrahigh volumetric energy density of 8.4 mWh cm -3 at a power density of 24.9 mW cm -3 , which is retained at 80% even when the power density is increased by 20-fold. The devices show very high electrochemical life (96% retention after 10000 charge/discharge cycles) and excellent mechanical flexibility. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Direct growth of vanadium nitride nanosheets on carbon nanotube fibers as novel negative electrodes for high-energy-density wearable fiber-shaped asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Guo, Jiabin; Zhang, Qichong; Sun, Juan; Li, Chaowei; Zhao, Jingxin; Zhou, Zhenyu; He, Bing; Wang, Xiaona; Man, Ping; Li, Qiulong; Zhang, Jun; Xie, Liyan; Li, Mingxing; Yao, Yagang

2018-04-01

Significant efforts have been recently devoted to constructing high-performance fiber-shaped asymmetric supercapacitors. However, it is still a paramount challenge to develop high-energy-density fiber-shaped asymmetric supercapacitors for practical applications in portable and wearable electronics. This work reports a simple and efficient method to directly grow vanadium nitride nanosheets on carbon nanotube fibers as advanced negative electrodes with a high specific capacitance of 188 F/cm3 (564 mF/cm2). Taking advantage of their attractive structure, we successfully fabricated a fiber-shaped asymmetric supercapacitor device with a maximum operating voltage of 1.6 V by assembling the vanadium nitride/carbon nanotube fiber negative electrode with the Zinc-Nickel-Cobalt ternary oxides nanowire arrays positive electrode. Due to the excellent synergistic effects between positive and negative electrodes, a remarkable specific capacitance of 50 F/cm3 (150 mF/cm2) and an outstanding energy density of 17.78 mWh/cm3 (53.33 μWh/cm2) for our fiber-shaped asymmetric supercapacitor can be achieved. Furthermore, the as-assembled fiber-shaped asymmetric supercapacitor device has excellent mechanical flexibility in that 91% of the capacitance retained after bending 90° for 3000 times. Thus, this work exploits a pathway to construct high-energy-density fiber-shaped asymmetric supercapacitor for next-generation portable and wearable electronics.

Layered-MnO₂ Nanosheet Grown on Nitrogen-Doped Graphene Template as a Composite Cathode for Flexible Solid-State Asymmetric Supercapacitor.

PubMed

Liu, Yongchuan; Miao, Xiaofei; Fang, Jianhui; Zhang, Xiangxin; Chen, Sujing; Li, Wei; Feng, Wendou; Chen, Yuanqiang; Wang, Wei; Zhang, Yining

2016-03-02

Flexible solid-state supercapacitors provide a promising energy-storage alternative for the rapidly growing flexible and wearable electronic industry. Further improving device energy density and developing a cheap flexible current collector are two major challenges in pushing the technology forward. In this work, we synthesize a nitrogen-doped graphene/MnO2 nanosheet (NGMn) composite by a simple hydrothermal method. Nitrogen-doped graphene acts as a template to induce the growth of layered δ-MnO2 and improves the electronic conductivity of the composite. The NGMn composite exhibits a large specific capacitance of about 305 F g(-1) at a scan rate of 5 mV s(-1). We also create a cheap and highly conductive flexible current collector using Scotch tape. Flexible solid-state asymmetric supercapacitors are fabricated with NGMn cathode, activated carbon anode, and PVA-LiCl gel electrolyte. The device can achieve a high operation voltage of 1.8 V and exhibits a maximum energy density of 3.5 mWh cm(-3) at a power density of 0.019 W cm(-3). Moreover, it retains >90% of its initial capacitance after 1500 cycles. Because of its flexibility, high energy density, and good cycle life, NGMn-based flexible solid state asymmetric supercapacitors have great potential for application in next-generation portable and wearable electronics.

Microwave produced plasma in a Toroidal Device

NASA Astrophysics Data System (ADS)

Singh, A. K.; Edwards, W. F.; Held, E. D.

2010-11-01

A currentless toroidal plasma device exhibits a large range of interesting basic plasma physics phenomena. Such a device is not in equilibrium in a strict magneto hydrodynamic sense. There are many sources of free energy in the form of gradients in plasma density, temperature, the background magnetic field and the curvature of the magnetic field. These free energy sources excite waves and instabilities which have been the focus of studies in several devices in last two decades. A full understanding of these simple plasmas is far from complete. At Utah State University we have recently designed and installed a microwave plasma generation system on a small tokamak borrowed from the University of Saskatchewan, Saskatoon, Canada. Microwaves are generated at 2.45 GHz in a pulsed dc mode using a magnetron from a commercial kitchen microwave oven. The device is equipped with horizontal and vertical magnetic fields and a transformer to impose a toroidal electric field for current drive. Plasmas can be obtained over a wide range of pressure with and without magnetic fields. We present some preliminary measurements of plasma density and potential profiles. Measurements of plasma temperature at different operating conditions are also presented.

Redox Species of Redox Flow Batteries: A Review.

PubMed

Pan, Feng; Wang, Qing

2015-11-18

Due to the capricious nature of renewable energy resources, such as wind and solar, large-scale energy storage devices are increasingly required to make the best use of the renewable power. The redox flow battery is considered suitable for large-scale applications due to its modular design, good scalability and flexible operation. The biggest challenge of the redox flow battery is the low energy density. The redox active species is the most important component in redox flow batteries, and the redox potential and solubility of redox species dictate the system energy density. This review is focused on the recent development of redox species. Different categories of redox species, including simple inorganic ions, metal complexes, metal-free organic compounds, polysulfide/sulfur and lithium storage active materials, are reviewed. The future development of redox species towards higher energy density is also suggested.

Market Impact | Transportation Research | NREL

Science.gov Websites

, airplanes, and astronauts' spacesuits rely on lithium-ion (Li-ion) batteries for high energy density in a Battery Internal Short-Circuit Device is helping industry partners improve the safety of Li-ion batteries Partners Use Breakthrough Device to Improve Battery Safety Electric vehicles, consumer electronics

Electroactive and High Dielectric Folic Acid/PVDF Composite Film Rooted Simplistic Organic Photovoltaic Self-Charging Energy Storage Cell with Superior Energy Density and Storage Capability.

PubMed

Roy, Swagata; Thakur, Pradip; Hoque, Nur Amin; Bagchi, Biswajoy; Sepay, Nayim; Khatun, Farha; Kool, Arpan; Das, Sukhen

2017-07-19

Herein we report a simplistic prototype approach to develop an organic photovoltaic self-charging energy storage cell (OPSESC) rooted with biopolymer folic acid (FA) modified high dielectric and electroactive β crystal enriched poly(vinylidene fluoride) (PVDF) composite (PFA) thin film. Comprehensive and exhaustive characterizations of the synthesized PFA composite films validate the proper formation of β-polymorphs in PVDF. Significant improvements of both β-phase crystallization (F(β) ≈ 71.4%) and dielectric constant (ε ≈ 218 at 20 Hz for PFA of 7.5 mass %) are the twosome realizations of our current study. Enhancement of β-phase nucleation in the composites can be thought as a contribution of the strong interaction of the FA particles with the PVDF chains. Maxwell-Wagner-Sillars (MWS) interfacial polarization approves the establishment of thermally stable high dielectric values measured over a wide temperature spectrum. The optimized high dielectric and electroactive films are further employed as an active energy storage material in designing our device named as OPSESC. Self-charging under visible light irradiation without an external biasing electrical field and simultaneous remarkable self-storage of photogenerated electrical energy are the two foremost aptitudes and the spotlight of our present investigation. Our as fabricated device delivers an impressively high energy density of 7.84 mWh/g and an excellent specific capacitance of 61 F/g which is superior relative to the other photon induced two electrode organic self-charging energy storage devices reported so far. Our device also proves the realistic utility with good recycling capability by facilitating commercially available light emitting diode.

Ab initio modeling of steady-state and time-dependent charge transport in hole-only α-NPD devices

NASA Astrophysics Data System (ADS)

Liu, Feilong; Massé, Andrea; Friederich, Pascal; Symalla, Franz; Nitsche, Robert; Wenzel, Wolfgang; Coehoorn, Reinder; Bobbert, Peter A.

2016-12-01

We present an ab initio modeling study of steady-state and time-dependent charge transport in hole-only devices of the amorphous molecular semiconductor α-NPD [N ,N'-Di(1 -naphthyl)-N ,N'-diphenyl-(1 ,1'-biphenyl)-4 ,4'-diamine] . The study is based on the microscopic information obtained from atomistic simulations of the morphology and density functional theory calculations of the molecular hole energies, reorganization energies, and transfer integrals. Using stochastic approaches, the microscopic information obtained in simulation boxes at a length scale of ˜10 nm is expanded and employed in one-dimensional (1D) and three-dimensional (3D) master-equation modeling of the charge transport at the device scale of ˜100 nm. Without any fit parameter, predicted current density-voltage and impedance spectroscopy data obtained with the 3D modeling are in very good agreement with measured data on devices with different α-NPD layer thicknesses in a wide range of temperatures, bias voltages, and frequencies. Similarly good results are obtained with the computationally much more efficient 1D modeling after optimizing a hopping prefactor.

Phase transformations, anisotropic pyroelectric energy harvesting and electrocaloric properties of (Pb,La)(Zr,Sn,Ti)O3 single crystals.

PubMed

Zhuo, Fangping; Li, Qiang; Gao, Jinghan; Yan, Qingfeng; Zhang, Yiling; Xi, Xiaoqing; Chu, Xiangcheng

2017-05-31

(Pb,La)(Zr,Sn,Ti)O 3 (PLZST) single crystals with their chemical composition located at the tetragonal antiferroelectric region are grown via the flux method in a PbO-PbF 2 -B 2 O 3 mixture. Segregation of the Ti 4+ component in the as-grown crystals is observed due to the strong affinity between the oxygen anion and Ti 4+ ions. The critical electric field of the antiferroelectric to ferroelectric phase transition is determined to be about 0.5 kV mm -1 . The electric field induced ferroelectric phase transforms back into the antiferroelectric phase at a depolarization temperature of 125 °C. Anisotropy of the harvested energy density and electrocaloric behaviors are achieved for the [100], [110] and [111]-oriented PLZST crystals. Based on the thermodynamic theory approach, all the abovementioned behaviors originate from the anisotropic total entropy change. Enhanced electrocaloric strength (0.3 K mm kV -1 ) and the harvested energy density of 0.62 J cm -3 are obtained in the [111]-oriented PLZST crystals. Our results demonstrate the competence of PLZST single crystals for cooling devices and pyroelectric energy harvesting and provide new opportunities to improve energy harvesting density and electrocaloric properties via the anisotropic structural layout, which make the PLZST crystals attractive for solid state cooling devices and energy conversion technologies.

Enhanced discharge energy density of rGO/PVDF nanocomposites: The role of the heterointerface

NASA Astrophysics Data System (ADS)

Zhang, Ye; Wang, Yaqiong; Qi, Shaojun; Dunn, Steve; Dong, Hanshan; Button, Tim

2018-05-01

Recent reports of conductive-filler/polymer composites with large dielectric permittivity (K) make them potential candidates for flexible capacitors. Hence, an interesting question is how these high K composites behave under a strong electric field strength. In this letter, we use in-situ-reduced graphite oxide (rGO)/poly(vinylidene fluoride) (PVDF) nanocomposites as an example to study the energy storage behaviour of high K materials. We show the dielectric behaviour contrasts between weak and strong fields. High K materials inevitably become more lossy with increasing field strength. Simultaneously, we reveal that the in-situ reduction temperature can affect the energy storage performance. Improved energy storage performance is achieved for a nanocomposite reduced at a moderate temperature. When reduced at 160 °C, a device with an rGO volume fraction of 1.5 vol. % displayed a discharge energy density of 0.67 J/cm3 at 50 MV/m. This was 2.9 times greater than pure PVDF. We develop a model to explain this behaviour that proposes a reduced electrical contrast of the rGO/PVDF heterointerface minimising the recombination of localized charge carriers. Our results indicate, simultaneously, the potential and limitation of high K nanocomposites and shed light on the optimisation of the design and fabrication of high discharge energy density flexible capacitors for microelectronic devices.

Nanostructured Electrode Materials Derived from Metal-Organic Framework Xerogels for High-Energy-Density Asymmetric Supercapacitor.

PubMed

Mahmood, Asif; Zou, Ruqiang; Wang, Qingfei; Xia, Wei; Tabassum, Hassina; Qiu, Bin; Zhao, Ruo

2016-01-27

This work successfully demonstrates metal-organic framework (MOF) derived strategy to prepare nanoporous carbon (NPC) with or without Fe3O4/Fe nanoparticles by the optimization of calcination temperature as highly active electrode materials for asymmetric supercapacitors (ASC). The nanostructured Fe3O4/Fe/C hybrid shows high specific capacitance of 600 F/g at a current density of 1 A/g and excellent capacitance retention up to 500 F/g at 8 A/g. Furthermore, hierarchically NPC with high surface area also obtained from MOF gels displays excellent electrochemical performance of 272 F/g at 2 mV/s. Considering practical applications, aqueous ASC (aASC) was also assembled, which shows high energy density of 17.496 Wh/kg at the power density of 388.8 W/kg. The high energy density and excellent capacity retention of the developed materials show great promise for the practical utilization of these energy storage devices.

Thermal management in MoS2 based integrated device using near-field radiation

NASA Astrophysics Data System (ADS)

Peng, Jiebin; Zhang, Gang; Li, Baowen

2015-09-01

Recently, wafer-scale growth of monolayer MoS2 films with spatial homogeneity is realized on SiO2 substrate. Together with the latest reported high mobility, MoS2 based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS2, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS2 to graphene. We demonstrate that in resonance, the maximum heat transfer via near-field radiation between MoS2 and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS2 sheet. Therefore, an efficient thermal management strategy for MoS2 integrated device is proposed: Graphene sheet is brought into close proximity, 10-20 nm from MoS2 device; heat energy transfer from MoS2 to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.

Design of Alpha Voltaic Power Source Using Americium 241 (241Am) and Diamond with a Power Density of 10 mW/cm3

DTIC Science & Technology

2017-10-19

GaN) was calculated and compared . Alpha-voltaic energy converters were designed in diamond and GaN based on the energy deposition calculations...Example Power Source Two example device designs are calculated and compared . A diamond device containing 2 charge collection regions (Schottky and p...ARL-TR-8189 ● OCT 2017 US Army Research Laboratory Design of Alpha-Voltaic Power Source Using Americium-241 (241Am) and Diamond

Electrochemically Synthesis of Nickel Cobalt Sulfide for High‐Performance Flexible Asymmetric Supercapacitors

PubMed Central

Zhang, Chunyan; Cai, Xiaoyi; Qian, Yao; Jiang, Haifeng; Zhou, Lijun; Li, Baosheng; Shen, Zexiang; Huang, Wei

2017-01-01

Abstract A lightweight, flexible, and highly efficient energy management strategy is highly desirable for flexible electronic devices to meet a rapidly growing demand. Herein, Ni–Co–S nanosheet array is successfully deposited on graphene foam (Ni–Co–S/GF) by a one‐step electrochemical method. The Ni–Co–S/GF composed of Ni–Co–S nanosheet array which is vertically aligned to GF and provides a large interfacial area for redox reactions with optimum interstitials facilitates the ions diffusion. The Ni–Co–S/GF electrodes have high specific capacitance values of 2918 and 2364 F g−1 at current densities of 1 and 20 A g−1, respectively. Using such hierarchical Ni–Co–S/GF as the cathode, a flexible asymmetric supercapacitor (ASC) is further fabricated with polypyrrple(PPy)/GF as the anode. The flexible asymmetric supercapacitors have maximum operation potential window of 1.65 V, and energy densities of 79.3 and 37.7 Wh kg−1 when the power densities are 825.0 and 16100 W kg−1, respectively. It's worth nothing that the ASC cells have robust flexibility with performance well maintained when the devices were bent to different angles from 180° to 15° at a duration of 5 min. The efficient electrochemical deposition method of Ni–Co–S with a preferred orientation of nanosheet arrays is applicable for the flexible energy storage devices. PMID:29610721

Electrochemically Synthesis of Nickel Cobalt Sulfide for High-Performance Flexible Asymmetric Supercapacitors.

PubMed

Zhang, Chunyan; Cai, Xiaoyi; Qian, Yao; Jiang, Haifeng; Zhou, Lijun; Li, Baosheng; Lai, Linfei; Shen, Zexiang; Huang, Wei

2018-02-01

A lightweight, flexible, and highly efficient energy management strategy is highly desirable for flexible electronic devices to meet a rapidly growing demand. Herein, Ni-Co-S nanosheet array is successfully deposited on graphene foam (Ni-Co-S/GF) by a one-step electrochemical method. The Ni-Co-S/GF composed of Ni-Co-S nanosheet array which is vertically aligned to GF and provides a large interfacial area for redox reactions with optimum interstitials facilitates the ions diffusion. The Ni-Co-S/GF electrodes have high specific capacitance values of 2918 and 2364 F g -1 at current densities of 1 and 20 A g -1 , respectively. Using such hierarchical Ni-Co-S/GF as the cathode, a flexible asymmetric supercapacitor (ASC) is further fabricated with polypyrrple(PPy)/GF as the anode. The flexible asymmetric supercapacitors have maximum operation potential window of 1.65 V, and energy densities of 79.3 and 37.7 Wh kg -1 when the power densities are 825.0 and 16100 W kg -1 , respectively. It's worth nothing that the ASC cells have robust flexibility with performance well maintained when the devices were bent to different angles from 180° to 15° at a duration of 5 min. The efficient electrochemical deposition method of Ni-Co-S with a preferred orientation of nanosheet arrays is applicable for the flexible energy storage devices.

Production of 35S for a Liquid Semiconductor Betavoltaic

DOE Office of Scientific and Technical Information (OSTI.GOV)

Meier, David E.; Garnov, A. Y.; Robertson, J. D.

2009-10-01

The specific energy density from radioactive decay is five to six orders of magnitude greater than the specific energy density in conventional chemical battery and fuel cell technologies. We are currently investigating the use of liquid semiconductor based betavoltaics as a way to directly convert the energy of radioactive decay into electrical power and potentially avoid the radiation damage that occurs in solid state semiconductor devices due to non-ionizing energy loss. Sulfur-35 was selected as the isotope for the liquid semiconductor demonstrations because it can be produced in high specific activity and it is chemically compatible with known liquid semiconductormore » media.« less

Demonstration of ultra-high recyclable energy densities in domain-engineered ferroelectric films.

PubMed

Cheng, Hongbo; Ouyang, Jun; Zhang, Yun-Xiang; Ascienzo, David; Li, Yao; Zhao, Yu-Yao; Ren, Yuhang

2017-12-08

Dielectric capacitors have the highest charge/discharge speed among all electrical energy devices, but lag behind in energy density. Here we report dielectric ultracapacitors based on ferroelectric films of Ba(Zr 0.2 ,Ti 0.8 )O 3 which display high-energy densities (up to 166 J cm -3 ) and efficiencies (up to 96%). Different from a typical ferroelectric whose electric polarization is easily saturated, these Ba(Zr 0.2 ,Ti 0.8 )O 3 films display a much delayed saturation of the electric polarization, which increases continuously from nearly zero at remnant in a multipolar state, to a large value under the maximum electric field, leading to drastically improved recyclable energy densities. This is achieved by the creation of an adaptive nano-domain structure in these perovskite films via phase engineering and strain tuning. The lead-free Ba(Zr 0.2 ,Ti 0.8 )O 3 films also show excellent dielectric and energy storage performance over a broad frequency and temperature range. These findings may enable broader applications of dielectric capacitors in energy storage, conditioning, and conversion.

High energy density rechargeable magnesium battery using earth-abundant and non-toxic elements

PubMed Central

Orikasa, Yuki; Masese, Titus; Koyama, Yukinori; Mori, Takuya; Hattori, Masashi; Yamamoto, Kentaro; Okado, Tetsuya; Huang, Zhen-Dong; Minato, Taketoshi; Tassel, Cédric; Kim, Jungeun; Kobayashi, Yoji; Abe, Takeshi; Kageyama, Hiroshi; Uchimoto, Yoshiharu

2014-01-01

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 mAh·g−1 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl)imide–triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems. PMID:25011939

High energy density rechargeable magnesium battery using earth-abundant and non-toxic elements

NASA Astrophysics Data System (ADS)

Orikasa, Yuki; Masese, Titus; Koyama, Yukinori; Mori, Takuya; Hattori, Masashi; Yamamoto, Kentaro; Okado, Tetsuya; Huang, Zhen-Dong; Minato, Taketoshi; Tassel, Cédric; Kim, Jungeun; Kobayashi, Yoji; Abe, Takeshi; Kageyama, Hiroshi; Uchimoto, Yoshiharu

2014-07-01

Rechargeable magnesium batteries are poised to be viable candidates for large-scale energy storage devices in smart grid communities and electric vehicles. However, the energy density of previously proposed rechargeable magnesium batteries is low, limited mainly by the cathode materials. Here, we present new design approaches for the cathode in order to realize a high-energy-density rechargeable magnesium battery system. Ion-exchanged MgFeSiO4 demonstrates a high reversible capacity exceeding 300 mAh.g-1 at a voltage of approximately 2.4 V vs. Mg. Further, the electronic and crystal structure of ion-exchanged MgFeSiO4 changes during the charging and discharging processes, which demonstrates the (de)insertion of magnesium in the host structure. The combination of ion-exchanged MgFeSiO4 with a magnesium bis(trifluoromethylsulfonyl)imide-triglyme electrolyte system proposed in this work provides a low-cost and practical rechargeable magnesium battery with high energy density, free from corrosion and safety problems.

High performance, flexible, poly(3,4-ethylenedioxythiophene) supercapacitors achieved by doping redox mediators in organogel electrolytes

NASA Astrophysics Data System (ADS)

Zhang, Huanhuan; Li, Jinyu; Gu, Cheng; Yao, Mingming; Yang, Bing; Lu, Ping; Ma, Yuguang

2016-11-01

The relatively low energy density is now a central issue hindering the development of supercapacitors as energy storage devices. Various approaches are thus developed to enhance the energy density, mainly centering on the fabrication of electrode materials or optimization of cell configurations. Compared with these approaches, modifications in electrolytes are much simple and versatile. Herein, we integrate the wide voltages endowed by organic electrolytes and the additional capacitances brought by redox mediators, to fabricate high energy density supercapacitors. On the basis of this idea, supercapacitors with poly(3,4-ethylenedioxythiophene) (PEDOT) as electrode material exhibit extended operating voltage of 1.5 V, extraordinary capacitance of 363 F g-1 and high energy density of 27.4 Wh kg-1. The redox mediators reported here, ferrocene and 4-oxo-2,2,6,6-tetramethylpiperidinooxy, are the first time being applied in supercapacitors, especially in the gel state. While providing additional faradaic capacitances, they also exhibit synergistic interaction with PEDOT and improve the cycling stability of supercapacitors.

Size-Dependent Surface Energy Density of Spherical Face-Centered-Cubic Metallic Nanoparticles.

PubMed

Wei, Yaochi; Chen, Shaohua

2015-12-01

The surface energy density of nano-sized elements exhibits a significantly size-dependent behavior. Spherical nanoparticle, as an important element in nano-devices and nano-composites, has attracted many interesting studies on size effect, most of which are molecular dynamics (MD) simulations. However, the existing MD calculations yield two opposite size-dependent trends of surface energy density of nanoparticles. In order to clarify such a real underlying problem, atomistic calculations are carried out in the present paper for various spherical face-centered-cubic (fcc) metallic nanoparticles. Both the embedded atom method (EAM) potential and the modified embedded atom method (MEAM) one are adopted. It is found that the size-dependent trend of surface energy density of nanoparticles is not governed by the chosen potential function or variation trend of surface energy, but by the defined radius of spherical nanoparticles in MD models. The finding in the present paper should be helpful for further theoretical studies on surface/interface effect of nanoparticles and nanoparticle-reinforced composites.

Ultrathin Graphene Membranes as Flexible Electrodes for Electrochemical Double Layer Capacitors

NASA Astrophysics Data System (ADS)

Talapatra, Saikat; Kar, Swastik; Shah, Rakesh; Ghosh, Sujoy; An, Xiaohong; Simmons, Trevor; Washington, Morris; Nayak, Saroj

2010-03-01

We will present the results of our investigations of electrochemical double layer capacitors (EDLCs) or supercapacitors (SC) fabricated using graphene based ultra thin membranes. These EDLC's show far superior performance compared to other carbon nanomaterials based EDLC's devices. We found that the graphene based devices possess specific capacitance values as high as 120 F/g, with impressive power densities (˜105 kW/kg) and energy densities (˜9.2 Wh/kg). Further, these devices indicated rapid charge transfer response even without the use of any binders or specially prepared current collectors. Our ultracapacitors reflect a significant improvement over previously reported graphene-based ultracapacitors and are substantially better than those obtained with carbon nanotubes.

A molecular shift register based on electron transfer

NASA Technical Reports Server (NTRS)

Hopfield, J. J.; Onuchic, Josenelson; Beratan, David N.

1988-01-01

An electronic shift-register memory at the molecular level is described. The memory elements are based on a chain of electron-transfer molecules and the information is shifted by photoinduced electron-transfer reactions. This device integrates designed electronic molecules onto a very large scale integrated (silicon microelectronic) substrate, providing an example of a 'molecular electronic device' that could actually be made. The design requirements for such a device and possible synthetic strategies are discussed. Devices along these lines should have lower energy usage and enhanced storage density.

Modelling of cantilever based on piezoelectric energy harvester

NASA Astrophysics Data System (ADS)

Rahim, N. F.; Ong, N. R.; Aziz, M. H. A.; Alcain, J. B.; Haimi, W. M. W. N.; Sauli, Z.

2017-09-01

Recent technology allows devices to become smaller and with more functions. However, the battery size remained the same and for some devices, the battery must be larger in order to accommodate the greater power demands by the portable device. Piezoelectric energy harvester has been suggested as a substitute for the batteries in coming future. In this paper, a cantilever based piezoelectric energy harvester was modelled and simulated using COMSOL software. The analysis focused on the mechanical part of the harvesting system such as output power, output voltage and vibration frequency. Results of the simulations proved that flexible piezoelectric energy harvesters using nano-materials had remarkable strength under the large strain. However, although the large strain was induced on the flexible energy harvesters, the output power was still lower than the bulk and MEMS piezoelectric energy harvesters that operated at the resonance frequency. The off-resonance operation and very lower packing density of the active piezoelectric materials of the flexible energy harvesters resulted in a low output power.

Inkjet-Printed Electrodes on A4 Paper Substrates for Low-Cost, Disposable, and Flexible Asymmetric Supercapacitors.

PubMed

Sundriyal, Poonam; Bhattacharya, Shantanu

2017-11-08

Printed electronics is widely gaining much attention for compact and high-performance energy-storage devices because of the advancement of flexible electronics. The development of a low-cost current collector, selection, and utilization of the proper material deposition tool and improvement of the device energy density are major challenges for the existing flexible supercapacitors. In this paper, we have reported an inkjet-printed solid-state asymmetric supercapacitor on commercial A4 paper using a low-cost desktop printer (EPSON L130). The physical properties of all inks have been carefully optimized so that the developed inks are within the printable range, i.e., Fromm number of 4 < Z < 14 for all inks. The paper substrate is made conducting (sheet resistance ∼ 1.6 Ω/sq) by printing 40 layers of conducting graphene oxide (GO) ink on its surface. The developed conducting patterns on paper are further printed with a GO-MnO 2 nanocomposite ink to make a positive electrode, and another such structure is printed with activated carbon ink to form a negative electrode. A combination of both of these electrodes is outlaid by fabricating an asymmetric supercapacitor. The assembled asymmetric supercapacitor with poly(vinyl alcohol) (PVA)-LiCl gel electrolyte shows a stable potential window of 0-2.0 V and exhibits outstanding flexibility, good cyclic stability, high rate capability, and high energy density. The fabricated paper-substrate-based flexible asymmetric supercapacitor also displays an excellent electrochemical performances, e.g., a maximum areal capacitance of 1.586 F/cm 2 (1023 F/g) at a current density of 4 mA/cm 2 , highest energy density of 22 mWh/cm 3 at a power density of 0.099 W/cm 3 , a capacity retention of 89.6% even after 9000 charge-discharge cycles, and a low charge-transfer resistance of 2.3 Ω. So, utilization of inkjet printing for the development of paper-based flexible electronics has a strong potential for embedding into the next generation low-cost, compact, and wearable energy-storage devices and other printed electronic applications.

Device and method for imploding a microsphere with a fast liner

DOEpatents

Thode, Lester E.

1981-01-01

A device and method for relativistic electron beam heating of a high-density plasma in a small localized region. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises DT, DD, hydrogen boron or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target gas is ionized prior to application of the electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy and momentum into a small localized region of the high-density plasma target. Fast liners disposed in the high-density target plasma are explosively or ablatively driven to implosion by a heated annular plasma surrounding the fast liner generated by an annular relativistic electron beam. An azimuthal magnetic field produced by axial current flow in the annular plasma, causes the energy in the heated annular plasma to converge on the fast liner to drive the fast liner to implode a microsphere.

Hydrothermally formed three-dimensional nanoporous Ni(OH)2 thin-film supercapacitors.

PubMed

Yang, Yang; Li, Lei; Ruan, Gedeng; Fei, Huilong; Xiang, Changsheng; Fan, Xiujun; Tour, James M

2014-09-23

A three-dimensional nanoporous Ni(OH)2 thin-film was hydrothermally converted from an anodically formed porous layer of nickel fluoride/oxide. The nanoporous Ni(OH)2 thin-films can be used as additive-free electrodes for energy storage. The nanoporous layer delivers a high capacitance of 1765 F g(-1) under three electrode testing. After assembly with porous activated carbon in asymmetric supercapacitor configurations, the devices deliver superior supercapacitive performances with capacitance of 192 F g(-1), energy density of 68 Wh kg(-1), and power density of 44 kW kg(-1). The wide working potential window (up to 1.6 V in 6 M aq KOH) and stable cyclability (∼90% capacitance retention over 10,000 cycles) make the thin-film ideal for practical supercapacitor devices.

Bacterial-cellulose-derived carbon nanofiber@MnO₂ and nitrogen-doped carbon nanofiber electrode materials: an asymmetric supercapacitor with high energy and power density.

PubMed

Chen, Li-Feng; Huang, Zhi-Hong; Liang, Hai-Wei; Guan, Qing-Fang; Yu, Shu-Hong

2013-09-14

A new kind of high-performance asymmetric supercapacitor is designed with pyrolyzed bacterial cellulose (p-BC)-coated MnO₂ as a positive electrode material and nitrogen-doped p-BC as a negative electrode material via an easy, efficient, large-scale, and green fabrication approach. The optimal asymmetric device possesses an excellent supercapacitive behavior with quite high energy and power density. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Characterization of Anodized Titanium Based Novel Paradigm Supercapacitors: Impact of Salt Identity and Frequency on Dielectric Values, Power, and Energy Densities

DTIC Science & Technology

2017-03-01

fire the weapon is 31 m3. Ultimately, the ideal capacitors would match the energy density of the best batteries . At this time, Lithium Ion batteries ...Discharge) .....119 Figure 115. Ragone Plot of Supercapacitors vs. Batteries with NH4Cl 30 wt% and KOH 30 wt%. Adapted from [18...charge/discharge frequency. Batteries , capacitors, and fly-wheels are all under consideration at this time; each device has its advantages and

Laser-machined piezoelectric cantilevers for mechanical energy harvesting.

PubMed

Kim, HyunUk; Bedekar, Vishwas; Islam, Rashed Adnan; Lee, Woo-Ho; Leo, Don; Priya, Shashank

2008-09-01

In this study, we report results on a piezoelectric- material-based mechanical energy-harvesting device that was fabricated by combining laser machining with microelectronics packaging technology. It was found that the laser-machining process did not have significant effect on the electrical properties of piezoelectric material. The fabricated device was tested in the low-frequency regime of 50 to 1000 Hz at constant force of 8 g (where g = 9.8 m/s(2)). The device was found to generate continuous power of 1.13 microW at 870 Hz across a 288.5 kOmega load with a power density of 301.3 microW/cm(3).

Phosphorene quantum dot-fullerene nanocomposites for solar energy conversion: An unexplored inorganic-organic nanohybrid with novel photovoltaic properties

NASA Astrophysics Data System (ADS)

Rajbanshi, Biplab; Kar, Moumita; Sarkar, Pallavi; Sarkar, Pranab

2017-10-01

Using the self-consistent charge density-functional based tight-binding (SCC-DFTB) method, coupled with time-dependent density functional theory (TDDFT) calculations, for the first time we explore the possibility of use of phosphorene quantum dots in solar energy harvesting devices. The phosphorene quantum dots-fullerene (PQDs-PCBA) nanocomposites show type-II band alignment indicating spatial separation of charge carriers. The TDDFT calculations also show that the PQD-fullerene nanocomposites seem to be exciting material for future generation solar energy harvester, with extremely fast charge transfer and very poor recombination rate.

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for High Energy Density plasmas at energies below 10 keV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Valdivia, M. P.; Stutman, D.; Finkenthal, M.

2014-07-15

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities.more » We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.« less

Moiré deflectometry using the Talbot-Lau interferometer as refraction diagnostic for high energy density plasmas at energies below 10 keV.

PubMed

Valdivia, M P; Stutman, D; Finkenthal, M

2014-07-01

The highly localized density gradients expected in High Energy Density (HED) plasma experiments can be characterized by x-ray phase-contrast imaging in addition to conventional attenuation radiography. Moiré deflectometry using the Talbot-Lau grating interferometer setup is an attractive HED diagnostic due to its high sensitivity to refraction induced phase shifts. We report on the adaptation of such a system for operation in the sub-10 keV range by using a combination of free standing and ultrathin Talbot gratings. This new x-ray energy explored matches well the current x-ray backlighters used for HED experiments, while also enhancing phase effects at lower electron densities. We studied the performance of the high magnification, low energy Talbot-Lau interferometer, for single image phase retrieval using Moiré fringe deflectometry. Our laboratory and simulation studies indicate that such a device is able to retrieve object electron densities from phase shift measurements. Using laboratory x-ray sources from 7 to 15 μm size we obtained accurate simultaneous measurements of refraction and attenuation for both sharp and mild electron density gradients.

[Research on electron density in DC needle-plate corona discharge at atmospheric pressure].

PubMed

Liu, Zhi-Qiang; Guo, Wei; Liu, Tao-Tao; Wu, Wen-Shuo; Liu, Shu-Min

2013-11-01

Using needle-plate discharge device, corona discharge experiment was done in the atmosphere. Through photo of spot size of light-emitting area, the relationship between the voltage and thickness of corona layer was discussed. When the distance between tip and plate is fixed, the thickness of corona layer increases with the increase in voltage; when the voltage is fixed, the thickness of corona layer decreases with the increase in the distance between tip and plate. As spectral intensity of N2 (C3pi(u)) (337.1 nm)reflects high energy electron density, it was measured with emission spectrometry. The results show that high energy electron density is the biggest near the needle tip and the relationship between high energy electron density and voltage is basically linear increasing. Fixing voltage, high energy electron density decreases with the increase in the distance between tip and plate. When the voltage and the distance between tip and plate are fixed, the high energy electron density increases with the decrease in the curvature radius of needle tip. These results are of great importance for the study of plasma parameters of corona discharge.

High-Performance Supercapacitor Electrode Materials from Cellulose-Derived Carbon Nanofibers.

PubMed

Cai, Jie; Niu, Haitao; Li, Zhenyu; Du, Yong; Cizek, Pavel; Xie, Zongli; Xiong, Hanguo; Lin, Tong

2015-07-15

Nitrogen-functionalized carbon nanofibers (N-CNFs) were prepared by carbonizing polypyrrole (PPy)-coated cellulose NFs, which were obtained by electrospinning, deacetylation of electrospun cellulose acetate NFs, and PPy polymerization. Supercapacitor electrodes prepared from N-CNFs and a mixture of N-CNFs and Ni(OH)2 showed specific capacitances of ∼236 and ∼1045 F g(-1), respectively. An asymmetric supercapacitor was further fabricated using N-CNFs/Ni(OH)2 and N-CNFs as positive and negative electrodes. The supercapacitor device had a working voltage of 1.6 V in aqueous KOH solution (6.0 M) with an energy density as high as ∼51 (W h) kg(-1) and a maximum power density of ∼117 kW kg(-1). The device had excellent cycle lifetime, which retained ∼84% specific capacitance after 5000 cycles of cyclic voltammetry scans. N-CNFs derived from electrospun cellulose may be useful as an electrode material for development of high-performance supercapacitors and other energy storage devices.

Fuel cells for low power applications

NASA Astrophysics Data System (ADS)

Heinzel, A.; Hebling, C.; Müller, M.; Zedda, M.; Müller, C.

Electronic devices show an ever-increasing power demand and thus, require innovative concepts for power supply. For a wide range of power and energy capacity, membrane fuel cells are an attractive alternative to conventional batteries. The main advantages are the flexibility with respect to power and capacity achievable with different devices for energy conversion and energy storage, the long lifetime and long service life, the good ecological balance, very low self-discharge. Therefore, the development of fuel cell systems for portable electronic devices is an attractive, although also a challenging, goal. The fuel for a membrane fuel cell might be hydrogen from a hydride storage system or methanol/water as a liquid alternative. The main differences between the two systems are the much higher power density for hydrogen fuel cells, the higher energy density per weight for the liquid fuel, safety aspects and infrastructure for fuel supply for hydride materials. For different applications, different system designs are required. High power cells are required for portable computers, low power methanol fuel cells required for mobile phones in hybrid systems with batteries and micro-fuel cells are required, e.g. for hand held PCs in the sub-Watt range. All these technologies are currently under development. Performance data and results of simulations and experimental investigations will be presented.

Vortex energy landscape from real space imaging analysis of YBa2Cu3O7 with different defect structures

NASA Astrophysics Data System (ADS)

Luccas, R. F.; Granados, X.; Obradors, X.; Puig, T.

2014-10-01

A methodology based on real space vortex image analysis is presented able to estimate semi-quantitatively the relevant energy densities of an arbitrary array of vortices, map the interaction energy distributions and evaluate the pinning energy associated to particular defects. The combined study using nanostructuration tools, a vortex visualization technique and the energy method is seen as an opportunity to estimate vortex pinning potentials strengths. Particularly, spatial distributions of vortex energy densities induced by surface nanoindented scratches are evaluated and compared to those of twin boundaries. This comparative study underlines the remarkable role of surface nanoscratches in pinning vortices and its potentiality in the design of novel devices for pinning and guiding vortex motion.

Aquagel electrode separator for use in batteries and supercapacitors

DOEpatents

Mayer, S.T.; Kaschmitter, J.L.; Pekala, R.W.

1995-03-28

An electrode separator is described for electrochemical energy storage devices, such as a high energy density capacitor incorporating a variety of carbon foam electrodes. The separator is derived from an aquagel of resorcinol-formaldehyde and related polymers and containing ionically conducting electrolyte in the pores thereof. 9 figures.

Ag incorporated Mn3O4/AC nanocomposite based supercapacitor devices with high energy density and power density.

PubMed

Nagamuthu, S; Vijayakumar, S; Muralidharan, G

2014-12-14

Silver incorporated Mn3O4/amorphous carbon (AC) nanocomposites are synthesized by a green chemistry method. X-ray diffraction studies revealed the structural changes in Mn3O4/AC nanocomposites attributable to the addition of silver. Cyclic voltammetry, charge-discharge and ac-impedance studies indicated that the Ag-Mn3O4/AC-5 electrode was the most suitable candidate for supercapacitor applications. From the galvanostatic charge-discharge studies, a higher specific capacitance of 981 F g(-1) at a specific current of 1 A g(-1) was obtained. An Ag-Mn3O4/AC-symmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as an anode as well as a cathode, and an asymmetric supercapacitor consisting of an Ag-incorporated Mn3O4/AC composite as a cathode and an activated carbon as an anode have been fabricated. The symmetric device exhibits a specific cell capacitance of 72 F g(-1) at a specific current of 1 A g(-1) whereas the asymmetric device delivers a specific cell capacitance of 180 F g(-1) at a high current rate of 10 A g(-1). The asymmetric supercapacitor device yields a high energy density of 81 W h kg(-1). This is higher than that of lead acid batteries and comparable with that of nickel hydride batteries.

Evaluation of a Silicon 90Sr Betavoltaic Power Source.

PubMed

Dixon, Jefferson; Rajan, Aravindh; Bohlemann, Steven; Coso, Dusan; Upadhyaya, Ajay D; Rohatgi, Ajeet; Chu, Steven; Majumdar, Arun; Yee, Shannon

2016-12-01

Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from 90 Sr as a power source is investigated. We propose a design for a >10% efficient betavoltaic device, which generates 1 W of power. A Varian Clinac iX is used to simulate the high-energy electrons emitted from 90 Sr, and a high efficiency c-Si photovoltaic cell is used as the converter. The measured conversion efficiency is 16%. This relatively high value is attributed to proper length scale matching and the generation of secondary electrons in c-Si by the primary β-particles.

Evaluation of a Silicon 90Sr Betavoltaic Power Source

PubMed Central

Dixon, Jefferson; Rajan, Aravindh; Bohlemann, Steven; Coso, Dusan; Upadhyaya, Ajay D.; Rohatgi, Ajeet; Chu, Steven; Majumdar, Arun; Yee, Shannon

2016-01-01

Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from 90Sr as a power source is investigated. We propose a design for a >10% efficient betavoltaic device, which generates 1 W of power. A Varian Clinac iX is used to simulate the high-energy electrons emitted from 90Sr, and a high efficiency c-Si photovoltaic cell is used as the converter. The measured conversion efficiency is 16%. This relatively high value is attributed to proper length scale matching and the generation of secondary electrons in c-Si by the primary β-particles. PMID:27905521

Evaluation of a Silicon 90Sr Betavoltaic Power Source

NASA Astrophysics Data System (ADS)

Dixon, Jefferson; Rajan, Aravindh; Bohlemann, Steven; Coso, Dusan; Upadhyaya, Ajay D.; Rohatgi, Ajeet; Chu, Steven; Majumdar, Arun; Yee, Shannon

2016-12-01

Betavoltaic energy converters (i.e., β-batteries) are attractive power sources because of their potential for high energy densities (>200 MWh/kg) and long duration continuous discharge (>1 year). However, conversion efficiencies have been historically low (<3%). High efficiency devices can be achieved by matching β-radiation transport length scales with the device physics length scales. In this work, the efficiency of c-Si devices using high-energy (>1 MeV) electrons emitted from 90Sr as a power source is investigated. We propose a design for a >10% efficient betavoltaic device, which generates 1 W of power. A Varian Clinac iX is used to simulate the high-energy electrons emitted from 90Sr, and a high efficiency c-Si photovoltaic cell is used as the converter. The measured conversion efficiency is 16%. This relatively high value is attributed to proper length scale matching and the generation of secondary electrons in c-Si by the primary β-particles.

An optimal design of magnetostrictive material (MsM) based energy harvester

NASA Astrophysics Data System (ADS)

Hu, Jingzhen; Yuan, Fuh-Gwo; Xu, Fujun; Huang, Alex Q.

2010-04-01

In this study, an optimal vibration-based energy harvesting system using magnetostrictive material (MsM) has been designed to power the Wireless Intelligent Sensor Platform (WISP), developed at North Carolina State University. A linear MsM energy harvesting device has been modeled and optimized to maximize the power output. The effects of number of MsM layers and glue layers, and load matching on the output power of the MsM energy harvester have been analyzed. From the measurement, the open circuit voltage can reach 1.5 V when the MsM cantilever beam operates at the 2nd natural frequency 324 Hz. The AC output power is 0.97 mW, giving power density 279 μW/cm3. Since the MsM device has low open circuit output voltage characteristics, a full-wave quadrupler has been designed to boost the rectified output voltage. To deliver the maximum output power to the load, a complex conjugate impedance matching between the load and the MsM device has been implemented using a discontinuous conduction mode (DCM) buck-boost converter. The maximum output power after the voltage quadrupler is now 705 μW and power density reduces to 202.4 μW/cm3, which is comparable to the piezoelectric energy harvesters given in the literature. The output power delivered to a lithium rechargeable battery is around 630 μW, independent of the load resistance.

Thermal Peak Management Using Organic Phase Change Materials for Latent Heat Storage in Electronic Applications

PubMed Central

Maxa, Jacob; Novikov, Andrej; Nowottnick, Mathias

2017-01-01

Modern high power electronics devices consists of a large amount of integrated circuits for switching and supply applications. Beside the benefits, the technology exhibits the problem of an ever increasing power density. Nowadays, heat sinks that are directly mounted on a device, are used to reduce the on-chip temperature and dissipate the thermal energy to the environment. This paper presents a concept of a composite coating for electronic components on printed circuit boards or electronic assemblies that is able to buffer a certain amount of thermal energy, dissipated from a device. The idea is to suppress temperature peaks in electronic components during load peaks or electronic shorts, which otherwise could damage or destroy the device, by using a phase change material to buffer the thermal energy. The phase change material coating could be directly applied on the chip package or the PCB using different mechanical retaining jigs.

Full synergistic effect of hydrothermal NiCo2O4 nanosheets/CuCo2O4 nanocones supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Bai, Hongye; Shao, Rong; Xu, Wei; Shi, Weidong

2018-06-01

In this work, a series of NiCo2O4/CuCo2O4 composites were prepared by a two-step hydrothermal method. The optimized NiCo2O4/CuCo2O4 electrode shows more than 5 times area capacitance (4.97 F cm-2) than pure NiCo2O4 at the current density of 1 mA cm-2. The best performance of sample assembled an asymmetric supercapacitor could reach up to 42 F g-1 at the current density of 1 A g-1. In addition, the maximum energy density of 15 W h kg-1 was achieved with the power density of 814 W kg-1. The as-prepared active electrode material also reveals excellent cycling stability with 90.6% capacitance retention after 5000 cycles. These results indicate potential application in developing energy storage devices with high energy density power density.

Spray-painted binder-free SnSe electrodes for high-performance energy-storage devices.

PubMed

Wang, Xianfu; Liu, Bin; Xiang, Qingyi; Wang, Qiufan; Hou, Xiaojuan; Chen, Di; Shen, Guozhen

2014-01-01

SnSe nanocrystal electrodes on three-dimensional (3D) carbon fabric and Au-coated polyethylene terephthalate (PET) wafer have been prepared by a simple spray-painting process and were further investigated as binder-free active-electrodes for Lithium-ion batteries (LIBs) and flexible stacked all-solid-state supercapacitors. The as-painted SnSe nanocrystals/carbon fabric electrodes exhibit an outstanding capacity of 676 mAh g(-1) after 80 cycles at a current density of 200 mA g(-1) and a considerable high-rate capability in lithium storage because of the excellent ion transport from the electrolyte to the active materials and the efficient charge transport between current collector and electrode materials. The binder-free electrodes also provide a larger electrochemical active surface compared with electrodes containing binders, which leads to the enhanced capacities of energy-storage devices. A flexible stacked all-solid-state supercapacitor based on the SnSe nanocrystals on Au-coated PET wafers shows high capacitance reversibility with little performance degradation at different current densities after 2200 charge-discharge cycles and even when bent. This allows for many potential applications in facile, cost-effective, spray-paintable, and flexible energy-storage devices. The results indicate that the fabrication of binder-free electrodes by a spray painting process is an interesting direction for the preparation of high-performance energy-storage devices. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Symmetric supercapacitor: Sulphurized graphene and ionic liquid.

PubMed

Shaikh, Jasmin S; Shaikh, Navajsharif S; Kharade, Rohini; Beknalkar, Sonali A; Patil, Jyoti V; Suryawanshi, Mahesh P; Kanjanaboos, Pongsakorn; Hong, Chang Kook; Kim, Jin Hyeok; Patil, Pramod S

2018-10-01

Symmetric supercapacitor is advanced over simple supercapacitor device due to their stability over a large potential window and high energy density. Graphene is a desired candidate for supercapacitor application since it has a high surface area, good electronic conductivity and high electro chemical stability. There is a pragmatic use of ionic liquid electrolyte for supercapacitor due to its stability over a large potential window, good ionic conductivity and eco-friendly nature. For high performance supercapacitor, the interaction between ionic liquid electrolyte and graphene are crucial for better charge transportation. In respect of this, a three-dimensional (3D) nanoporous honeycomb shaped sulfur embedded graphene (S-graphene) has been synthesized by simple chemical method. Here, the fabrication of high performance symmetric supercapacitor is done by using S-graphene as an electrode and [BMIM-PF 6 ] as an electrolyte. The particular architecture of S-graphene benefited to reduce the ion diffusion resistance, providing the large surface area for charge transportation and efficient charge storage. The S-graphene and ionic liquid-based symmetric supercapacitor device showed the large potential window of 3.2 V with high energy density 124 Wh kg -1 at 0.2 A g -1 constant applied current density. Furthermore, this device shows good cycling performance (stability) with a capacitive retention of 95% over 20,000 cycles at a higher current density of 2 A g -1 . Copyright © 2018 Elsevier Inc. All rights reserved.

BiFeO3-doped (K0.5,Na0.5)(Mn0.005,Nb0.995)O3 ferroelectric thin film capacitors for high energy density storage applications

NASA Astrophysics Data System (ADS)

Won, Sung Sik; Kawahara, Masami; Kuhn, Lindsay; Venugopal, Vineeth; Kwak, Jiyeon; Kim, Ill Won; Kingon, Angus I.; Kim, Seung-Hyun

2017-04-01

Environmentally benign lead-free ferroelectric (K0.5,Na0.5)(Mn0.005,Nb0.995)O3 (KNMN) thin film capacitors with a small concentration of a BiFeO3 (BF) dopant were prepared by a cost effective chemical solution deposition method for high energy density storage device applications. 6 mol. % BF-doped KNMN thin films showed very slim hysteresis loops with high maximum and near-zero remanent polarization values due to a phase transition from the orthorhombic structure to the pseudo-cubic structure. Increasing the electric field up to 2 MV/cm, the total energy storage density (Jtotal), the effective recoverable energy density (Jeff), and the energy conversion efficiency (η) of lead-free KNMN-BF thin film capacitors were 31.0 J/cm3, 28.0 J/cm3, and 90.3%, respectively. In addition, these thin film capacitors exhibited a fast discharge time of a few μs and a high temperature stability up to 200 °C, proving their strong potential for high energy density storage and conversion applications.

High-Performance Biomass-Based Flexible Solid-State Supercapacitor Constructed of Pressure-Sensitive Lignin-Based and Cellulose Hydrogels.

PubMed

Peng, Zhiyuan; Zou, Yubo; Xu, Shiqi; Zhong, Wenbin; Yang, Wantai

2018-06-19

Employing renewable, earth-abundant, environmentally friendly, low-cost natural materials to design flexible supercapacitors (FSCs) as energy storage devices in wearable/portable electronics represents the global perspective to build sustainable and green society. Chemically stable and flexible cellulose and electroactive lignin have been employed to construct a biomass-based FSC for the first time. The FSC was assembled using lignosulfonate/single-walled carbon nanotube HNO 3 (Lig/SWCNT HNO 3 ) pressure-sensitive hydrogels as electrodes and cellulose hydrogels as an electrolyte separator. The assembled biomass-based FSC shows high specific capacitance (292 F g -1 at a current density of 0.5 A g -1 ), excellent rate capability, and an outstanding energy density of 17.1 W h kg -1 at a power density of 324 W kg -1 . Remarkably, the FSC presents outstanding electrochemical stability even suffering 1000 bending cycles. Such excellent flexibility, stability, and electrochemical performance enable the designed biomass-based FSCs as prominent candidates in applications of wearable electronic devices.

Hydrodynamic electronic fluid instability in GaAs MESFETs at terahertz frequencies

NASA Astrophysics Data System (ADS)

Li, Kang; Hao, Yue; Jin, Xiaoqi; Lu, Wu

2018-01-01

III-V compound semiconductor field effect transistors (FETs) are potential candidates as solid state THz emitters and detectors due to plasma wave instability in these devices. Using a 2D hydrodynamic model, here we present the numerical studies of electron fluid instability in a FET structure. The model is implemented in a GaAs MESFET structure with a gate length of 0.2 µm as a testbed by taking into account the non-equilibrium transport and multi-valley non-parabolicity energy bands. The results show that the electronic density instability in the channel can produce stable periodic oscillations at THz frequencies. Along with stable oscillations, negative differential resistance in output characteristics is observed. The THz emission energy density increases monotonically with the drain bias. The emission frequency of electron density oscillations can be tuned by both gate and drain biases. The results suggest that III-V FETs can be a kind of versatile THz devices with good tunability on both radiative power and emission frequency.

Transparent lithium-ion batteries

PubMed Central

Yang, Yuan; Jeong, Sangmoo; Hu, Liangbing; Wu, Hui; Lee, Seok Woo; Cui, Yi

2011-01-01

Transparent devices have recently attracted substantial attention. Various applications have been demonstrated, including displays, touch screens, and solar cells; however, transparent batteries, a key component in fully integrated transparent devices, have not yet been reported. As battery electrode materials are not transparent and have to be thick enough to store energy, the traditional approach of using thin films for transparent devices is not suitable. Here we demonstrate a grid-structured electrode to solve this dilemma, which is fabricated by a microfluidics-assisted method. The feature dimension in the electrode is below the resolution limit of human eyes, and, thus, the electrode appears transparent. Moreover, by aligning multiple electrodes together, the amount of energy stored increases readily without sacrificing the transparency. This results in a battery with energy density of 10 Wh/L at a transparency of 60%. The device is also flexible, further broadening their potential applications. The transparent device configuration also allows in situ Raman study of fundamental electrochemical reactions in batteries. PMID:21788483

Ultralow-frequency PiezoMEMS energy harvester using thin-film silicon and parylene substrates

NASA Astrophysics Data System (ADS)

Jackson, Nathan; Olszewski, Oskar Z.; O'Murchu, Cian; Mathewson, Alan

2018-01-01

Developing a self-sustained leadless pacemaker requires the development of an ultralow-frequency energy harvesting system that can fit within the required dimensions. This paper reports on the design and development of two types of PiezoMEMS energy harvesters that fit within the capsule dimensions and have a low resonant frequency between 20 to 30 Hz, which is required for the application. A bullet-shaped mass was designed to maximize the displacement and enhance power density of the devices. In addition, two types of devices were fabricated and compared (i) a silicon-based cantilever and (ii) a parylene-C-based cantilever with a thin aluminum nitride layer. The silicon device demonstrated higher peak power of 29.8 μW compared with the 6.4 μW for the parylene device. However, due to the low duty cycle of the heart rate and the damping factors of the two materials the average power was significantly higher for the parylene device (2.71 μW) compared with the silicon device (1.22 μW) per cantilever. The results demonstrate that a polymer-based energy harvester can increase the average power due to low damping for an impulse-based vibration application.

Flexible asymmetric supercapacitors with high energy and high power density in aqueous electrolytes.

PubMed

Cheng, Yingwen; Zhang, Hongbo; Lu, Songtao; Varanasi, Chakrapani V; Liu, Jie

2013-02-07

Supercapacitors with both high energy and high power densities are critical for many practical applications. In this paper, we discuss the design and demonstrate the fabrication of flexible asymmetric supercapacitors based on nanocomposite electrodes of MnO(2), activated carbon, carbon nanotubes and graphene. The combined unique properties of each of these components enable highly flexible and mechanically strong films that can serve as electrodes directly without using any current collectors or binders. Using these flexible electrodes and a roll-up approach, asymmetric supercapacitors with 2 V working voltage were successfully fabricated. The fabricated device showed excellent rate capability, with 78% of the original capacitance retained when the scan rate was increased from 2 mV s(-1) to 500 mV s(-1). Owing to the unique composite structure, these supercapacitors were able to deliver high energy density (24 W h kg(-1)) under high power density (7.8 kW kg(-1)) conditions. These features could enable supercapacitor based energy storage systems to be very attractive for a variety of critical applications, such as the power sources in hybrid electric vehicles and the back-up powers for wind and solar energy, where both high energy density and high power density are required.

Theoretical Limits of Energy Density in Silicon-Carbon Composite Anode Based Lithium Ion Batteries

PubMed Central

Dash, Ranjan; Pannala, Sreekanth

2016-01-01

Silicon (Si) is under consideration as a potential next-generation anode material for the lithium ion battery (LIB). Experimental reports of up to 40% increase in energy density of Si anode based LIBs (Si-LIBs) have been reported in literature. However, this increase in energy density is achieved when the Si-LIB is allowed to swell (volumetrically expand) more than graphite based LIB (graphite-LIB) and beyond practical limits. The volume expansion of LIB electrodes should be negligible for applications such as automotive or mobile devices. We determine the theoretical bounds of Si composition in a Si–carbon composite (SCC) based anode to maximize the volumetric energy density of a LIB by constraining the external dimensions of the anode during charging. The porosity of the SCC anode is adjusted to accommodate the volume expansion during lithiation. The calculated threshold value of Si was then used to determine the possible volumetric energy densities of LIBs with SCC anode (SCC-LIBs) and the potential improvement over graphite-LIBs. The level of improvement in volumetric and gravimetric energy density of SCC-LIBs with constrained volume is predicted to be less than 10% to ensure the battery has similar power characteristics of graphite-LIBs. PMID:27311811

Edge-enriched, porous carbon-based, high energy density supercapacitors for hybrid electric vehicles.

PubMed

Kim, Yong Jung; Yang, Cheol-Min; Park, Ki Chul; Kaneko, Katsumi; Kim, Yoong Ahm; Noguchi, Minoru; Fujino, Takeshi; Oyama, Shigeki; Endo, Morinobu

2012-03-12

Supercapacitors can store and deliver energy by a simple charge separation, and thus they could be an attractive option to meet transient high energy density in operating fuel cells and in electric and hybrid electric vehicles. To achieve such requirements, intensive studies have been carried out to improve the volumetric capacitance in supercapacitors using various types and forms of carbons including carbon nanotubes and graphenes. However, conventional porous carbons are not suitable for use as electrode material in supercapacitors for such high energy density applications. Here, we show that edge-enriched porous carbons are the best electrode material for high energy density supercapacitors to be used in vehicles as an auxiliary powertrain. Molten potassium hydroxide penetrates well-aligned graphene layers vertically and consequently generates both suitable pores that are easily accessible to the electrolyte and a large fraction of electrochemically active edge sites. We expect that our findings will motivate further research related to energy storage devices and also environmentally friendly electric vehicles. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

RFEA measurements of high-energy electrons in a helicon plasma device with expanding magnetic field

NASA Astrophysics Data System (ADS)

Gulbrandsen, Njål; Fredriksen, Åshild

2017-01-01

In the inductively coupled plasma of the Njord helicon device we have, for the same parameters as for which an ion beam exists, measured a downstream population of high-energy electrons emerging from the source. Separated measurements of energetic tail electrons was carried out by Retarding Field Energy Analyzer (RFEA) with a grounded entrance grid, operated in an electron collection mode. In a radial scan with the RFEA pointed toward the source, we found a significant population of high-energy electrons just inside the magnetic field line mapping to the edge of the source. A second peak in high-energy electrons density was observed in a radial position corresponding to the radius of the source. Also, throughout the main column a small contribution of high-energy electrons was observed. In a radial scan with a RFEA biased to collect ions a localized increase in the plasma ion density near the magnetic field line emerging from the plasma near the wall of the source was observed. This is interpreted as a signature of high-energy electrons ionizing the neutral gas. Also, a dip in the floating potential of a Langmuir probe is evident in this region where high-energy electrons is observed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chiang, Yet-Ming; Carter, Craig W.; Ho, Bryan Y.

Redox flow devices are described in which at least one of the positive electrode or negative electrode-active materials is a semi-solid or is a condensed ion-storing electroactive material, and in which at least one of the electrode-active materials is transported to and from an assembly at which the electrochemical reaction occurs, producing electrical energy. The electronic conductivity of the semi-solid is increased by the addition of conductive particles to suspensions and/or via the surface modification of the solid in semi-solids (e.g., by coating the solid with a more electron conductive coating material to increase the power of the device). Highmore » energy density and high power redox flow devices are disclosed. The redox flow devices described herein can also include one or more inventive design features. In addition, inventive chemistries for use in redox flow devices are also described.« less

Quantitative analysis of intermolecular interactions in orthorhombic rubrene

DOE PAGES

Hathwar, Venkatesha R.; Sist, Mattia; Jørgensen, Mads R. V.; ...

2015-08-14

Rubrene is one of the most studied organic semiconductors to date due to its high charge carrier mobility which makes it a potentially applicable compound in modern electronic devices. Previous electronic device characterizations and first principles theoretical calculations assigned the semiconducting properties of rubrene to the presence of a large overlap of the extended π-conjugated core between molecules. We present here the electron density distribution in rubrene at 20 K and at 100 K obtained using a combination of high-resolution X-ray and neutron diffraction data. The topology of the electron density and energies of intermolecular interactions are studied quantitatively. Specifically,more » the presence of C π...C πinteractions between neighbouring tetracene backbones of the rubrene molecules is experimentally confirmed from a topological analysis of the electron density, Non-Covalent Interaction (NCI) analysis and the calculated interaction energy of molecular dimers. A significant contribution to the lattice energy of the crystal is provided by H—H interactions. The electron density features of H—H bonding, and the interaction energy of molecular dimers connected by H—H interaction clearly demonstrate an importance of these weak interactions in the stabilization of the crystal structure. Finally, the quantitative nature of the intermolecular interactions is virtually unchanged between 20 K and 100 K suggesting that any changes in carrier transport at these low temperatures would have a different origin. The obtained experimental results are further supported by theoretical calculations.« less

Pyrolytic-carbon coating in carbon nanotube foams for better performance in supercapacitors

NASA Astrophysics Data System (ADS)

He, Nanfei; Yildiz, Ozkan; Pan, Qin; Zhu, Jiadeng; Zhang, Xiangwu; Bradford, Philip D.; Gao, Wei

2017-03-01

Nowadays, the wide-spread adoption of supercapacitors has been hindered by their inferior energy density to that of batteries. Here we report the use of our pyrolytic-carbon-coated carbon nanotube foams as lightweight, compressible, porous, and highly conductive current collectors in supercapacitors, which are infiltrated with chemically-reduced graphene oxide and later compressed via mechanical and capillary forces to generate the active electrodes. The pyrolytic carbon coatings, introduced by chemical vapor infiltration, wrap around the CNT junctions and increase the surface roughness. When active materials are infiltrated, the pyrolytic-carbon coatings help prevent the π-stacking, enlarge the accessible surface area, and increase the electrical conductivity of the scaffold. Our best-performing device offers 48% and 57% higher gravimetric energy and power density, 14% and 23% higher volumetric energy and power density, respectively, and two times higher knee frequency, than the device with commercial current collectors, while the "true-performance metrics" are strictly followed in our measurements. We have further clarified the solution resistance, charge transfer resistance/capacitance, double-layer capacitance, and Warburg resistance in our system via comprehensive impedance analysis, which will shed light on the design and optimization of similar systems.

Microbial fuel cells as pollutant treatment units: Research updates.

PubMed

Zhang, Quanguo; Hu, Jianjun; Lee, Duu-Jong

2016-10-01

Microbial fuel cells (MFC) are a device that can convert chemical energy in influent substances to electricity via biological pathways. Based on the consent that MFC technology should be applied as a waste/wastewater treatment unit rather than a renewable energy source, this mini-review discussed recent R&D efforts on MFC technologies for pollutant treatments and highlighted the challenges and research and development needs. Owing to the low power density levels achievable by larger-scale MFC, the MFC should be used as a device other than energy source such as being a pollutant treatment unit. Copyright © 2016 Elsevier Ltd. All rights reserved.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries

NASA Astrophysics Data System (ADS)

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-06-01

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg-1total electrode while also retaining a high energy density of 225 Wh kg-1total electrode, which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries.

PubMed

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-06-13

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg(-1)(total electrode) while also retaining a high energy density of 225 Wh kg(-1)(total electrode), which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices.

All-graphene-battery: bridging the gap between supercapacitors and lithium ion batteries

PubMed Central

Kim, Haegyeom; Park, Kyu-Young; Hong, Jihyun; Kang, Kisuk

2014-01-01

Herein, we propose an advanced energy-storage system: all-graphene-battery. It operates based on fast surface-reactions in both electrodes, thus delivering a remarkably high power density of 6,450 W kg−1total electrode while also retaining a high energy density of 225 Wh kg−1total electrode, which is comparable to that of conventional lithium ion battery. The performance and operating mechanism of all-graphene-battery resemble those of both supercapacitors and batteries, thereby blurring the conventional distinction between supercapacitors and batteries. This work demonstrates that the energy storage system made with carbonaceous materials in both the anode and cathode are promising alternative energy-storage devices. PMID:24923290

A lithium ion battery using an aqueous electrolyte solution

PubMed Central

Chang, Zheng; Li, Chunyang; Wang, Yanfang; Chen, Bingwei; Fu, Lijun; Zhu, Yusong; Zhang, Lixin; Wu, Yuping; Huang, Wei

2016-01-01

Energy and environmental pollution have become the two major problems in today’s society. The development of green energy storage devices with good safety, high reliability, high energy density and low cost are urgently demanded. Here we report on a lithium ion battery using an aqueous electrolyte solution. It is built up by using graphite coated with gel polymer membrane and LISICON as the negative electrode, and LiFePO4 in aqueous solution as the positive electrode. Its average discharge voltage is up to 3.1 V and energy density based on the two electrode materials is 258 Wh kg−1. It will be a promising energy storage system with good safety and efficient cooling effects. PMID:27328707

Exciton shelves for charge and energy transport in third-generation quantum-dot devices

NASA Astrophysics Data System (ADS)

Goodman, Samuel; Singh, Vivek; Noh, Hyunwoo; Casamada, Josep; Chatterjee, Anushree; Cha, Jennifer; Nagpal, Prashant

2014-03-01

Quantum dots are semiconductor nanocrystallites with size-dependent quantum-confined energy levels. While they have been intensively investigated to utilize hot-carriers for photovoltaic applications, to bridge the mismatch between incident solar photons and finite bandgap of semiconductor photocells, efficient charge or exciton transport in quantum-dot films has proven challenging. Here we show development of new coupled conjugated molecular wires with ``exciton shelves'', or different energy levels, matched with the multiple energy levels of quantum dots. Using single nanoparticle and ensemble device measurements we show successful extraction and transport of both bandedge and high-energy charge carriers, and energy transport of excitons. We demonstrate using measurements of electronic density of states, that careful matching of energy states of quantum-dot with molecular wires is important, and any mismatch can generate midgap states leading to charge recombination and reduced efficiency. Therefore, these exciton-shelves and quantum dots can lead to development of next-generation photovoltaic and photodetection devices using simultaneous transport of bandedge and hot-carriers or energy transport of excitons in these nanostructured solution-processed films.

Negative hydrogen ions in a linear helicon plasma device

NASA Astrophysics Data System (ADS)

Corr, Cormac; Santoso, Jesse; Samuell, Cameron; Willett, Hannah; Manoharan, Rounak; O'Byrne, Sean

2015-09-01

Low-pressure negative ion sources are of crucial importance to the development of high-energy (>1 MeV) neutral beam injection systems for the ITER experimental tokamak device. Due to their high power coupling efficiency and high plasma densities, helicon devices may be able to reduce power requirements and potentially remove the need for caesium. In helicon sources, the RF power can be coupled efficiently into the plasma and it has been previously observed that the application of a small magnetic field can lead to a significant increase in the plasma density. In this work, we investigate negative ion dynamics in a high-power (20 kW) helicon plasma source. The negative ion fraction is measured by probe-based laser photodetachment, electron density and temperature are determined by a Langmuir probe and tuneable diode laser absorption spectroscopy is used to determine the density of the H(n = 2) excited atomic state and the gas temperature. The negative ion density and excited atomic hydrogen density display a maximum at a low applied magnetic field of 3 mT, while the electron temperature displays a minimum. The negative ion density can be increased by a factor of 8 with the application of the magnetic field. Spatial and temporal measurements will also be presented. The Australian Research Grants Council is acknowledged for funding.

High Energy Density All Solid State Asymmetric Pseudocapacitors Based on Free Standing Reduced Graphene Oxide-Co3O4 Composite Aerogel Electrodes.

PubMed

Ghosh, Debasis; Lim, Joonwon; Narayan, Rekha; Kim, Sang Ouk

2016-08-31

Modern flexible consumer electronics require efficient energy storage devices with flexible free-standing electrodes. We report a simple and cost-effective route to a graphene-based composite aerogel encapsulating metal oxide nanoparticles for high energy density, free-standing, binder-free flexible pseudocapacitive electrodes. Hydrothermally synthesized Co3O4 nanoparticles are successfully housed inside the microporous graphene aerogel network during the room temperature interfacial gelation at the Zn surface. The resultant three-dimensional (3D) rGO-Co3O4 composite aerogel shows mesoporous quasiparallel layer stack morphology with a high loading of Co3O4, which offers numerous channels for ion transport and a 3D interconnected network for high electrical conductivity. All solid state asymmetric pseudocapacitors employing the composite aerogel electrodes have demonstrated high areal energy density of 35.92 μWh/cm(2) and power density of 17.79 mW/cm(2) accompanied by excellent cycle life.

An energy balance model for forest canopies: a case study

Treesearch

S. M. Goltz; James A. Smith

1996-01-01

The use of thermal scanning devices to map underlying terrain surface temperatures has been recognized as a potential tool for estimating evapotranspiration and latent heat flux densities in forest canopies.

The impact of hot charge carrier mobility on photocurrent losses in polymer-based solar cells

PubMed Central

Philippa, Bronson; Stolterfoht, Martin; Burn, Paul L.; Juška, Gytis; Meredith, Paul; White, Ronald D.; Pivrikas, Almantas

2014-01-01

A typical signature of charge extraction in disordered organic systems is dispersive transport, which implies a distribution of charge carrier mobilities that negatively impact on device performance. Dispersive transport has been commonly understood to originate from a time-dependent mobility of hot charge carriers that reduces as excess energy is lost during relaxation in the density of states. In contrast, we show via photon energy, electric field and film thickness independence of carrier mobilities that the dispersive photocurrent in organic solar cells originates not from the loss of excess energy during hot carrier thermalization, but rather from the loss of carrier density to trap states during transport. Our results emphasize that further efforts should be directed to minimizing the density of trap states, rather than controlling energetic relaxation of hot carriers within the density of states. PMID:25047086

Hierarchical chestnut-like MnCo2O4 nanoneedles grown on nickel foam as binder-free electrode for high energy density asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Hui, Kwun Nam; Hui, Kwan San; Tang, Zikang; Jadhav, V. V.; Xia, Qi Xun

2016-10-01

Hierarchical chestnut-like manganese cobalt oxide (MnCo2O4) nanoneedles (NNs) are successfully grown on nickel foam using a facile and cost-effective hydrothermal method. High resolution TEM image further verifies that the chestnut-like MnCo2O4 structure is assembled by numerous 1D MnCo2O4 nanoneedles, which are formed by numerous interconnected MnCo2O4 nanoparticles with grain diameter of ∼10 nm. The MnCo2O4 electrode exhibits high specific capacitance of 1535 F g-1 at 1 A g-1 and good rate capability (950 F g-1 at 10 A g-1) in a 6 M KOH electrolyte. An asymmetric supercapacitor is fabricated using MnCo2O4 NNs on Ni foam (MnCo2O4 NNs/NF) as the positive electrode and graphene/NF as the negative electrode. The device shows an operation voltage of 1.5 V and delivers a high energy density of ∼60.4 Wh kg-1 at a power density of ∼375 W kg-1. Moreover, the device exhibits an excellent cycling stability of 94.3% capacitance retention after 12000 cycles at 30 A g-1. This work demonstrates that hierarchical chestnut-like MnCo2O4 NNs could be a promising electrode for the high performance energy storage devices.

A three-dimensional reticulate CNT-aerogel for a high mechanical flexibility fiber supercapacitor.

PubMed

Li, Yong; Kang, Zhuo; Yan, Xiaoqin; Cao, Shiyao; Li, Minghua; Guo, Yan; Huan, Yahuan; Wen, Xiaosong; Zhang, Yue

2018-05-17

In recent years, the rapid development of portable and wearable electronic products has promoted the prosperity of fiber supercapacitors (FSCs), which serve as flexible and lightweight energy supply devices. However, research on FSCs is still in its infancy and the energy density of FSCs is far below the level of lithium-ion batteries. Here, we report a facile method to prepare a novel fibrous CNT-aerogel by electrochemical activation and freeze-drying. The fibrous CNT-aerogel electrode possesses a large specific surface area, high mechanical strength, excellent electrical conductivity, as well as a high specific capacitance of 160.8 F g-1 at 0.5 mA and long cycling stability. Then we assembled a non-faradaic FSC based on a fibrous CNT-aerogel as the electrode and a P(VDF-HFP)/EMIMBF4 ionogel as the electrolyte. The introduction of the ionogel electrolyte increases the operating voltage of the FSC to 3 V, and makes the device combine the intrinsic high power density (27.3 kW kg-1) of non-faradaic SCs with an ultrahigh energy density of 29.6 W h kg-1. More importantly, the assembled FSCs show excellent flexibility and bending-stability, and can still operate normally within a wide working temperature window (0-80 °C). The outstanding electrochemical performance and the mechanical/thermal stability indicate that the assembled FSC device is a promising power source for flexible electronics.

Formation of Triboelectric Series via Atomic-Level Surface Functionalization for Triboelectric Energy Harvesting.

PubMed

Shin, Sung-Ho; Bae, Young Eun; Moon, Hyun Kyung; Kim, Jungkil; Choi, Suk-Ho; Kim, Yongho; Yoon, Hyo Jae; Lee, Min Hyung; Nah, Junghyo

2017-06-27

Triboelectric charging involves frictional contact of two different materials, and their contact electrification usually relies on polarity difference in the triboelectric series. This limits the choices of materials for triboelectric contact pairs, hindering research and development of energy harvest devices utilizing triboelectric effect. A progressive approach to resolve this issue involves modification of chemical structures of materials for effectively engineering their triboelectric properties. Here, we describe a facile method to change triboelectric property of a polymeric surface via atomic-level chemical functionalizations using a series of halogens and amines, which allows a wide spectrum of triboelectric series over single material. Using this method, tunable triboelectric output power density is demonstrated in triboelectric generators. Furthermore, molecular-scale calculation using density functional theory unveils that electrons transferred through electrification are occupying the PET group rather than the surface functional group. The work introduced here would open the ability to tune triboelectric property of materials by chemical modification of surface and facilitate the development of energy harvesting devices and sensors exploiting triboelectric effect.

Self consistent solution of Schrödinger Poisson equations and some electronic properties of ZnMgO/ZnO hetero structures

NASA Astrophysics Data System (ADS)

Uslu, Salih; Yarar, Zeki

2017-02-01

The epitaxial growth of quantum wells composed of high quality allows the production and application to their device of new structures in low dimensions. The potential profile at the junction is determined by free carriers and by the level of doping. Therefore, the shape of potential is obtained by the electron density. Energy level determines the number of electrons that can be occupied at every level. Energy levels and electron density values of each level must be calculated self consistently. Starting with V(z) test potential, wave functions and electron densities for each energy levels can be calculated to solve Schrödinger equation. If Poisson's equation is solved with the calculated electron density, the electrostatic potential can be obtained. The new V(z) potential can be calculated with using electrostatic potential found beforehand. Thus, the obtained values are calculated self consistently to a certain error criterion. In this study, the energy levels formed in the interfacial potential, electron density in each level and the wave function dependence of material parameters were investigated self consistently.

Influence of temperature and electrolyte on the performance of activated-carbon supercapacitors

NASA Astrophysics Data System (ADS)

Liu, Ping; Verbrugge, Mark; Soukiazian, Souren

For hybrid electric vehicle traction applications, energy storage devices with high power density and energy efficiency are required. A primary attribute of supercapacitors is that they retain their high power density and energy efficiency even at -30 °C, the lowest temperature at which unassisted starting must be provided to customers. More abuse-tolerant electrolytes are preferred to the high-conductivity acetonitrile-based systems commonly employed. Propylene carbonate based electrolytes are a promising alternative. In this work, we compare the electrochemical performance of two high-power density electrical double layer supercapacitors employing acetonitrile and propylene carbonate as solvents. From this study, we are able to elucidate phenomena that control the resistance of supercapacitor at lower temperatures, and quantify the difference in performance associated with the two electrolytes.

Prediction of Excitation Energies for Conjugated Oligomers and Polymers from Time-Dependent Density Functional Theory

PubMed Central

Tao, Jianmin; Tretiak, Sergei; Zhu, Jian-Xin

2010-01-01

With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial role in the understanding of their optical properties and device design. In this review article, we discuss the calculation of excitation energies with time-dependent density functional theory, which is one of the most successful methods in the investigation of the dynamical response of molecular systems to external perturbation, owing to its high computational efficiency.

High power densities from high-temperature material interactions. [in thermionic energy conversion and metallic fluid heat pipes

NASA Technical Reports Server (NTRS)

Morris, J. F.

1981-01-01

Thermionic energy conversion (TEC) and metallic-fluid heat pipes (MFHPs), offering unique advantages in terrestrial and space energy processing by virtue of operating on working-fluid vaporization/condensation cycles that accept great thermal power densities at high temperatures, share complex materials problems. Simplified equations are presented that verify and solve such problems, suggesting the possibility of cost-effective applications in the near term for TEC and MFHP devices. Among the problems discussed are: the limitation of alkali-metal corrosion, protection against hot external gases, external and internal vaporization, interfacial reactions and diffusion, expansion coefficient matching, and creep deformation.

Inter-machine validation study of neoclassical transport modelling in medium- to high-density stellarator-heliotron plasmas

NASA Astrophysics Data System (ADS)

Dinklage, A.; Yokoyama, M.; Tanaka, K.; Velasco, J. L.; López-Bruna, D.; Beidler, C. D.; Satake, S.; Ascasíbar, E.; Arévalo, J.; Baldzuhn, J.; Feng, Y.; Gates, D.; Geiger, J.; Ida, K.; Isaev, M.; Jakubowski, M.; López-Fraguas, A.; Maaßberg, H.; Miyazawa, J.; Morisaki, T.; Murakami, S.; Pablant, N.; Kobayashi, S.; Seki, R.; Suzuki, C.; Suzuki, Y.; Turkin, Yu.; Wakasa, A.; Wolf, R.; Yamada, H.; Yoshinuma, M.; LHD Exp. Group; TJ-II Team; W7-AS Team

2013-06-01

A comparative study of energy transport for medium- to high-density discharges in the stellarator-heliotrons TJ-II, W7-AS and LHD is carried out. The specific discharge parameters are chosen to apply a recently concluded benchmarking study of neoclassical (NC) transport coefficients (Beidler et al 2011 Nucl. Fusion 51 076001) to perform this validation study. In contrast to previous experiments at low densities for which electron transport was predominant (Yokoyama et al 2007 Nucl. Fusion 47 1213), the current discharges also exhibit significant ion energy transport. As it affects the energy transport in 3D devices, the ambipolar radial electric field is addressed as well. For the discharges described, ion-root conditions, i.e. a small negative radial electric field were found. The energy transport in the peripheral region cannot be explained by NC theory. Within a ‘core region’(r/a < 1/2 ˜ 2/3), the predicted NC energy fluxes comply with experimental findings for W7-AS. For TJ-II, compliance in the core region is found for the particle transport and the electron energy transport. For the specific LHD discharges, the core energy transport complied with NC theory except for the electron energy transport in the inward-shifted magnetic configuration. The NC radial electric field tends to agree with experimental results for all devices but is measured to be more negative in the core of both LHD and TJ-II. As a general observation, the energy confinement time approaches the gyro-Bohm-type confinement scaling ISS04 (Yamada et al 2005 Nucl. Fusion 45 1684). This work is carried out within the International Stellarator-Heliotron Profile Database (www.ipp.mpg.de/ISS and http://ishpdb.nifs.ac.jp/index.html).

Si photonics technology for future optical interconnection

NASA Astrophysics Data System (ADS)

Zheng, Xuezhe; Krishnamoorthy, Ashok V.

2011-12-01

Scaling of computing systems require ultra-efficient interconnects with large bandwidth density. Silicon photonics offers a disruptive solution with advantages in reach, energy efficiency and bandwidth density. We review our progress in developing building blocks for ultra-efficient WDM silicon photonic links. Employing microsolder based hybrid integration with low parasitics and high density, we optimize photonic devices on SOI platforms and VLSI circuits on more advanced bulk CMOS technology nodes independently. Progressively, we successfully demonstrated single channel hybrid silicon photonic transceivers at 5 Gbps and 10 Gbps, and 80 Gbps arrayed WDM silicon photonic transceiver using reverse biased depletion ring modulators and Ge waveguide photo detectors. Record-high energy efficiency of less than 100fJ/bit and 385 fJ/bit were achieved for the hybrid integrated transmitter and receiver, respectively. Waveguide grating based optical proximity couplers were developed with low loss and large optical bandwidth to enable multi-layer intra/inter-chip optical interconnects. Thermal engineering of WDM devices by selective substrate removal, together with WDM link using synthetic wavelength comb, we significantly improved the device tuning efficiency and reduced the tuning range. Using these innovative techniques, two orders of magnitude tuning power reduction was achieved. And tuning cost of only a few 10s of fJ/bit is expected for high data rate WDM silicon photonic links.

Improvement of vibration energy harvesters mechanical Q-factor through high density proof mass integration

NASA Astrophysics Data System (ADS)

Dompierre, A.; Fréchette, L. G.

2016-11-01

This paper reports on improvement of the mechanical Q-factor of resonant energy harvesters at ambient pressure via the use of tungsten proof masses by evaluating the impact of the mass size and density on the squeeze film damping. To this end, a simplified model is first proposed to evaluate cantilever beams deflection and the resulting fluid pressure build up between the mass and a near surface. The model, which accounts for simultaneous transverse and rotational motion of very long tip masses as well as for 2D fluid flow in the gap, is used to extract a scaling law for the device fluidic Q-factor Qf. This law states that Qf can be improved by either increasing the linear mass density of the tip mass or by reducing the side lengths compared to the gap height. The first approach is validated experimentally by adding a tungsten proof mass on a silicon based device and observing an improvement of the Q-factor by 103%, going from 430 to 871, while the resonance frequency drops from 457 to 127 Hz. In terms of fluidic Q-factor, this represents an increase from 562 to 1673. These results successfully demonstrate the benefits of integrating a tungsten mass to reduce the fluid losses while potentially reducing the device footprint.

Determination of P3HT Trap Site Energies by Thermally Stimulated Current

NASA Astrophysics Data System (ADS)

Souza, J. F. P.; Serbena, J. P. M.; Kowalski, E. L.; Akcelrud, L. C.

2018-02-01

The thermal, electrical and morphological characterization of poly(3-hexylthiophene-2,5diyl) (P3HT) is presented and discussed. Thermal analyses revealed high glass transition, melting and degradation temperatures, indicating high stability of the polymer to annealings in the range 25-200°C. Electrical measurements were performed in spin-coated devices constructed using indium tin oxide (ITO) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) in the sandwich structure ITO/PEDOT:PSS/P3HT/Al. The devices were thermally treated at 25°C, 100°C, 150°C, and 200°C prior to the measurements. Characteristic curves of current density versus voltage showed that the injection of charge carriers is governed by tunneling at high electric fields. Hole mobility was estimated by impedance spectroscopy, showing a maximum value of 8.6 × 10-5 cm2/Vs for annealed films at 150°C. A thermally stimulated current technique was used to analyze the trap density in the P3HT and its respective energies for all devices, presenting the lowest trap density for annealed films at 150°C. Morphological features observed by atomic force microscopy showed that the 150°C thermally treated film presents the best interface condition of the four investigated annealing temperatures.

Facile and controllable synthesis of N/P co-doped graphene for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Xia, Kaisheng; Huang, Zhiyuan; Zheng, Lin; Han, Bo; Gao, Qiang; Zhou, Chenggang; Wang, Hongquan; Wu, Jinping

2017-10-01

Improving the energy density of carbon-based supercapacitors is one of the most urgent demands for developing high-power energy supplies, which in general requires delicate engineering of the carbon composition and textures. By pre-functionalization of graphene nanosheets and successive one-step (NH4)3PO4 activation, we prepared a type of nitrogen and phosphorus co-doped graphene (NPG) with high specific surface areas, hierarchical pore structures as well as tunable N and P contents. The as-obtained NPG shows high specific capacitances of 219 F g-1 (123 F cm-3) at 0.25 A g-1 and 175 F g-1 (98 F cm-3) at 10 A g-1, respectively. Accordingly, the NPG-based symmetrical supercapacitor device, working at a potential window of 1.3 V, could deliver an enhanced energy density of 8.2 Wh kg-1 (4.6 Wh L-1) at a power density of 162 W kg-1 (91 W L-1), which still retains 6.7 Wh kg-1 at 6.5 kW kg-1. In particular, under a current density of 5 A g-1, the device endows an 86% capacitance retention of initial after 20,000 cycles, displaying superior cycle stability. Our results imply the feasibility of NPG as a promising candidate for high-performance supercapacitors.

Development of Advanced Li Rich xLi2MO3 (1-x)LiMO2 Composite Cathode for High Capacity Li Ion Batteries

DTIC Science & Technology

2016-12-22

importance. Among advanced energy storage devices, lithium - ion batteries are remarkable systems due to their high energy density, high power density...and well cycled performance with considerable reliability. Lithium - ion batteries have been playing an important role in various application fields...Li0.24Mn0.55Co0.14Ni0.07]O2 cathode material for lithium ion batteries . Solid State Ionics, 2013. 233: p. 12-19. DISTRIBUTION A. Approved for public release

Cyanate ester-nanoparticle composites as multifunctional structural capacitors

NASA Astrophysics Data System (ADS)

De Leon, J. Eliseo

An important goal of engineering is to increase the energy density of electrical energy storage devices used to deliver power onboard mobile platforms. Equally important is the goal to reduce the overall mass of the vehicles transporting these devices to achieve increased fuel and cost efficiency. One approach to meeting both these objectives is to develop multifunctional systems that serve as both energy storage and load bearing structural devices. Multifunctional devices consist of constituents that individually perform a subset of the overall desired functions. However, the synergy achieved by the combination of each constituent's characteristics allows for system-level benefits that cannot be achieved by simply optimizing the separate subsystems. We investigated multifunctional systems consisting of light weight polymer matrix and high dielectric constant fillers to achieve these objectives. The monomer of bisphenol E cyanate ester exhibited excellent processing ability because of its low room temperature viscosity. Additionally, the fully cured thermoset demonstrated excellent thermal stability, specific strength and stiffness. Fillers, including multi-walled carbon nanotubes, nanometer scale barium titanate and nanometer scale calcium copper titanate, offer high dielectric constants that raised the effective dielectric constant of the polymer matrix composite. The combination of high epsilon'and high dielectric strength produce high energy density components exhibiting increased electrical energy storage. Mechanical (load bearing) improvements of the PMCs were attributed to covalently bonded nanometer and micrometer sized filler particles, as well as the continuous glass fiber, integrated into the resin systems which increased the structural characteristics of the cured composites. Breakdown voltage tests and dynamic mechanical analysis were employed to demonstrate that precise combinations of these constituents, under the proper processing conditions, can satisfy the needs presented by the aerospace industry and military forces.

Measurement of Electron Density Using the Multipole Resonance Probe, Langmuir Probe and Optical Emission Spectroscopy in Low Pressure Plasmas with Different Electron Energy Distribution Functions

NASA Astrophysics Data System (ADS)

Oberberg, Moritz; Bibinov, Nikita; Ries, Stefan; Awakowicz, Peter; Institute of Electrical Engineering; Plasma Technology Team

2016-09-01

In recently publication, the young diagnostic tool Multipole Resonance Probe (MRP) for electron density measurements was introduced. It is based on active plasma resonance spectroscopy (APRS). The probe was simulated und evaluated for different devices. The geometrical and electrical symmetry simplifies the APRS model, so that the electron density can be easily calculated from the measured resonance. In this work, low pressure nitrogen mixture plasmas with different electron energy distribution functions (EEDF) are investigated. The results of the MRP measurement are compared with measurements of a Langmuir Probe (LP) and Optical Emission Spectroscopy (OES). Probes and OES measure in different regimes of kinetic electron energy. Both probes measure electrons with low kinetic energy (<10 eV), whereas the OES is influenced by electrons with high kinetic energy which are needed for transitions of molecule bands. By the determination of the absolute intensity of N2(C-B) and N2+(B-X)electron temperature and density can be calculated. In a non-maxwellian plasma, all plasma diagnostics need to be combined.

Energy challenges in optical access and aggregation networks.

PubMed

Kilper, Daniel C; Rastegarfar, Houman

2016-03-06

Scalability is a critical issue for access and aggregation networks as they must support the growth in both the size of data capacity demands and the multiplicity of access points. The number of connected devices, the Internet of Things, is growing to the tens of billions. Prevailing communication paradigms are reaching physical limitations that make continued growth problematic. Challenges are emerging in electronic and optical systems and energy increasingly plays a central role. With the spectral efficiency of optical systems approaching the Shannon limit, increasing parallelism is required to support higher capacities. For electronic systems, as the density and speed increases, the total system energy, thermal density and energy per bit are moving into regimes that become impractical to support-for example requiring single-chip processor powers above the 100 W limit common today. We examine communication network scaling and energy use from the Internet core down to the computer processor core and consider implications for optical networks. Optical switching in data centres is identified as a potential model from which scalable access and aggregation networks for the future Internet, with the application of integrated photonic devices and intelligent hybrid networking, will emerge. © 2016 The Author(s).

Air bio-battery with a gas/liquid porous diaphragm cell for medical and health care devices.

PubMed

Arakawa, Takahiro; Xie, Rui; Seshima, Fumiya; Toma, Koji; Mitsubayashi, Kohji

2018-04-30

Powering future generations of medical and health care devices mandates the transcutaneous transfer of energy or harvesting energy from the human body fluid. Glucose-driven bio fuel cells (bio-batteries) demonstrate promise as they produce electrical energy from glucose, which is a substrate presents in physiological fluids. Enzymatic biofuel cells can convert chemical energy into electrical energy using enzymes as catalysts. In this study, an air bio-battery was developed for healthcare and medical applications, consisting of a glucose-driven enzymatic biofuel cell using a direct gas-permeable membrane or a gas/liquid porous diaphragm. The power generation characteristics included a maximum current density of 285μA/cm 2 and maximum power density of 70.7μW/cm 2 in the presence of 5mmol/L of glucose in solution. In addition, high-performance, long-term-stabilized power generation was achieved using the gas/liquid porous diaphragm for the reactions between oxygen and enzyme. This system can be powered using 5mmol/L of glucose, the value of which is similar to that of the blood sugar range in humans. Copyright © 2017 Elsevier B.V. All rights reserved.

Zinc oxide nanoring embedded lacey graphene nanoribbons in symmetric/asymmetric electrochemical capacitive energy storage

NASA Astrophysics Data System (ADS)

Sahu, Vikrant; Goel, Shubhra; Sharma, Raj Kishore; Singh, Gurmeet

2015-12-01

This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg-1 (ZnO/GNR symmetric) to 9.4 Wh kg-1 (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm-2, paves the way to a high performance aqueous electrochemical supercapacitive energy storage.This article describes the synthesis and characterization of ZnO nanoring embedded graphene nanoribbons. Patterned holes (mesopore dia.) in graphene nanoribbons are chemically generated, leading to a high density of the edge planes. These planes carry negatively charged surface groups (like -COOH and -OH) and therefore anchor the metal ions in a cordial fashion forming a string of metal ions along the edge planes. These strings of imbibed metal ions precipitate as tiny ZnO nanorings over lacey graphene nanoribbons. The thus obtained graphene nanoribbon (GNR) based hierarchical ZnO mesoporous structures are three dimensionally accessible to the electrolyte and demonstrate high performance in capacitive energy storage. The ZnO/GNR nanocomposite electrode in an asymmetric supercapacitor device with lacey reduced graphene oxide nanoribbons (LRGONRs) as a negative electrode exhibits a 2.0 V potential window in the aqueous electrolyte and an ultra-short time constant (0.08 s). The wide potential window consequently increased the energy density from 6.8 Wh kg-1 (ZnO/GNR symmetric) to 9.4 Wh kg-1 (ZnO/GNR||LRGONR asymmetric). The relaxation time constant obtained for the asymmetric supercapacitor device was three orders of magnitude less compared to the ZnO (symmetric, 33 s) supercapacitor device. The high cycling stability of ZnO/GNR||LRGONR up to 96.7% capacitance retention, after 5000 GCD cycles at 2 mA cm-2, paves the way to a high performance aqueous electrochemical supercapacitive energy storage. Electronic supplementary information (ESI) available. See DOI: 10.1039/c5nr06083d

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes

NASA Astrophysics Data System (ADS)

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-01

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ˜75 F g-1, ˜987 kW kg-1 and ˜27 W h kg-1, respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (˜158 F g-1) and energy density (˜53 W h kg-1). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices.

High-performance supercapacitors based on vertically aligned carbon nanotubes and nonaqueous electrolytes.

PubMed

Kim, Byungwoo; Chung, Haegeun; Kim, Woong

2012-04-20

We demonstrate the high performance of supercapacitors fabricated with vertically aligned carbon nanotubes and nonaqueous electrolytes such as ionic liquids and conventional organic electrolytes. Specific capacitance, maximum power and energy density of the supercapacitor measured in ionic liquid were ~75 F g(-1), ~987 kW kg(-1) and ~27 W h kg(-1), respectively. The high power performance was consistently indicated by a fast relaxation time constant of 0.2 s. In addition, electrochemical oxidation of the carbon nanotubes improved the specific capacitance (~158 F g(-1)) and energy density (~53 W h kg(-1)). Both high power and energy density could be attributed to the fast ion transport realized by the alignment of carbon nanotubes and the wide operational voltage defined by the ionic liquid. The demonstrated carbon-nanotube- and nonaqueous-electrolyte-based supercapacitors show great potential for the development of high-performance energy storage devices. © 2012 IOP Publishing Ltd

1D Ni-Co oxide and sulfide nanoarray/carbon aerogel hybrid nanostructures for asymmetric supercapacitors with high energy density and excellent cycling stability.

PubMed

Hao, Pin; Tian, Jian; Sang, Yuanhua; Tuan, Chia-Chi; Cui, Guanwei; Shi, Xifeng; Wong, C P; Tang, Bo; Liu, Hong

2016-09-15

The fabrication of supercapacitor electrodes with high energy density and excellent cycling stability is still a great challenge. A carbon aerogel, possessing a hierarchical porous structure, high specific surface area and electrical conductivity, is an ideal backbone to support transition metal oxides and bring hope to prepare electrodes with high energy density and excellent cycling stability. Therefore, NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid supercapacitor electrode materials were synthesized by assembling Ni-Co precursor needle arrays on the surface of the channel walls of hierarchical porous carbon aerogels derived from chitosan in this study. The 1D nanostructures grow on the channel surface of the carbon aerogel vertically and tightly, contributing to the enhanced electrochemical performance with ultrahigh energy density. The energy density of NiCo 2 S 4 nanotube array/carbon aerogel and NiCo 2 O 4 nanoneedle array/carbon aerogel hybrid asymmetric supercapacitors can reach up to 55.3 Wh kg -1 and 47.5 Wh kg -1 at a power density of 400 W kg -1 , respectively. These asymmetric devices also displayed excellent cycling stability with a capacitance retention of about 96.6% and 92% over 5000 cycles.

Weavable, Conductive Yarn-Based NiCo//Zn Textile Battery with High Energy Density and Rate Capability.

PubMed

Huang, Yan; Ip, Wing Shan; Lau, Yuen Ying; Sun, Jinfeng; Zeng, Jie; Yeung, Nga Sze Sea; Ng, Wing Sum; Li, Hongfei; Pei, Zengxia; Xue, Qi; Wang, Yukun; Yu, Jie; Hu, Hong; Zhi, Chunyi

2017-09-26

With intrinsic safety and much higher energy densities than supercapacitors, rechargeable nickel/cobalt-zinc-based textile batteries are promising power sources for next generation personalized wearable electronics. However, high-performance wearable nickel/cobalt-zinc-based batteries are rarely reported because there is a lack of industrially weavable and knittable highly conductive yarns. Here, we use scalably produced highly conductive yarns uniformly covered with zinc (as anode) and nickel cobalt hydroxide nanosheets (as cathode) to fabricate rechargeable yarn batteries. They possess a battery level capacity and energy density, as well as a supercapacitor level power density. They deliver high specific capacity of 5 mAh cm -3 and energy densities of 0.12 mWh cm -2 and 8 mWh cm -3 (based on the whole solid battery). They exhibit ultrahigh rate capabilities of 232 C (liquid electrolyte) and 116 C (solid electrolyte), which endows the batteries excellent power densities of 32.8 mW cm -2 and 2.2 W cm -3 (based on the whole solid battery). These are among the highest values reported so far. A wrist band battery is further constructed by using a large conductive cloth woven from the conductive yarns by a commercial weaving machine. It powers various electronic devices successfully, enabling dual functions of wearability and energy storage.

High-Performance Microsupercapacitors Based on Bioinspired Graphene Microfibers.

PubMed

Pan, Hui; Wang, Dawei; Peng, Qingfa; Ma, Jun; Meng, Xin; Zhang, Yaopeng; Ma, Yuning; Zhu, Shenmin; Zhang, Di

2018-03-28

The miniaturization of portable electronic devices has fueled the development of microsupercapacitors that hold great potential to complement or even replace microbatteries and electrolytic capacitors. In spite of recent developments taking advantage of printing and lithography, it remains a great challenge to attain a high energy density without sacrificing the power density. Herein, a new protocol mimicking the spider's spinning process is developed to create highly oriented microfibers from graphene-based composites via a purpose-designed microfluidic chip. The orientation provides the microfibers with an electrical conductivity of ∼3 × 10 4 S m -1 , which leads to a high power density; the energy density is sustained by nanocarbons and high-purity metallic molybdenum disulfide. The microfibers are patterned in-plane to fabricate asymmetric microsupercapacitors for flexible and on-chip energy storage. The on-chip microsupercapacitor with a high pattern resolution of 100 μm delivers energy density up to the order of 10 -2 W h cm -3 and retains an ultrahigh power density exceeding 100 W cm -3 in an aqueous electrolyte. This work provides new design of flexible and on-chip asymmetric microsupercapacitors based on microfibers. The unique biomimetic microfluidic fabrication of graphene microfibers for energy storage may also stimulate thinking of the bionic design in many other fields.

Free-Standing Conducting Polymer Films for High-Performance Energy Devices.

PubMed

Li, Zaifang; Ma, Guoqiang; Ge, Ru; Qin, Fei; Dong, Xinyun; Meng, Wei; Liu, Tiefeng; Tong, Jinhui; Jiang, Fangyuan; Zhou, Yifeng; Li, Ke; Min, Xue; Huo, Kaifu; Zhou, Yinhua

2016-01-18

Thick, uniform, easily processed, highly conductive polymer films are desirable as electrodes for solar cells as well as polymer capacitors. Here, a novel scalable strategy is developed to prepare highly conductive thick poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (HCT-PEDOT:PSS) films with layered structure that display a conductivity of 1400 S cm(-1) and a low sheet resistance of 0.59 ohm sq(-1). Organic solar cells with laminated HCT-PEDOT:PSS exhibit a performance comparable to the reference devices with vacuum-deposited Ag top electrodes. More importantly, the HCT-PEDOT:PSS film delivers a specific capacitance of 120 F g(-1) at a current density of 0.4 A g(-1). All-solid-state flexible symmetric supercapacitors with the HCT-PEDOT:PSS films display a high volumetric energy density of 6.80 mWh cm(-3) at a power density of 100 mW cm(-3) and 3.15 mWh cm(-3) at a very high power density of 16160 mW cm(-3) that outperforms previous reported solid-state supercapacitors based on PEDOT materials. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors.

PubMed

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-23

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm(-2) at 1 mA cm(-2), good flexibility with a higher value (204.6 mF cm(-2)) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg(-1) (with a power density of 3.2 kW kg(-1)) and a maximum power density of 4.2 kW kg(-1) (with an energy density of 3.1 Wh kg(-1)). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

Vapor-phase polymerization of poly(3, 4-ethylenedioxythiophene) nanofibers on carbon cloth as electrodes for flexible supercapacitors

NASA Astrophysics Data System (ADS)

Zhao, Xin; Dong, Mengyang; Zhang, Junxian; Li, Yingzhi; Zhang, Qinghua

2016-09-01

In this study, an evaporative vapor-phase polymerization approach was employed to fabricate vertically aligned poly(3, 4-ethylenedioxythiophene) (PEDOT) nanofibers on the surface of carbon cloth (CC). Optimized reaction conditions can obtain well distributed and uniform layers of high-aspect-ratio PEDOT nanofibers on CC. The hierarchical PEDOT/CC structure as a freestanding electrode exhibits good electrochemical properties. As a flexible symmetric supercapacitor, the PEDOT/CC hybrid electrode displays a specific areal capacitance of 201.4 mF cm-2 at 1 mA cm-2, good flexibility with a higher value (204.6 mF cm-2) in the bending state, and a good cycling stability of 92.4% after 1000 cycles. Moreover, the device shows a maximum energy density of 4.0 Wh kg-1 (with a power density of 3.2 kW kg-1) and a maximum power density of 4.2 kW kg-1 (with an energy density of 3.1 Wh kg-1). The results demonstrate that PEDOT may be a promising material for storage devices through a simple and efficient vapor-phase polymerization process with precisely controlled reaction conditions.

Hybrid thermionic-photovoltaic converter

DOE Office of Scientific and Technical Information (OSTI.GOV)

Datas, A.

2016-04-04

A conceptual device for the direct conversion of heat into electricity is presented. This concept hybridizes thermionic (TI) and thermophotovoltaic (TPV) energy conversion in a single thermionic-photovoltaic (TIPV) solid-state device. This device transforms into electricity both the electron and photon fluxes emitted by an incandescent surface. This letter presents an idealized analysis of this device in order to determine its theoretical potential. According to this analysis, the key advantage of this converter, with respect to either TPV or TI, is the higher power density in an extended temperature range. For low temperatures, TIPV performs like TPV due to the negligiblemore » electron flux. On the contrary, for high temperatures, TIPV performs like TI due to the great enhancement of the electron flux, which overshadows the photon flux contribution. At the intermediate temperatures, ∼1650 K in the case of this particular study, I show that the power density potential of TIPV converter is twice as great as that of TPV and TI. The greatest impact concerns applications in which the temperature varies in a relatively wide range, for which averaged power density enhancement above 500% is attainable.« less

Low-energy plasma focus device as an electron beam source.

PubMed

Khan, Muhammad Zubair; Ling, Yap Seong; Yaqoob, Ibrar; Kumar, Nitturi Naresh; Kuang, Lim Lian; San, Wong Chiow

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 10(16)/m(3), respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences.

Decoupling energy and power

NASA Astrophysics Data System (ADS)

Grattieri, Matteo; Minteer, Shelley D.

2018-01-01

Biological photovoltaic devices (BPVs) use photosynthetic microorganisms to produce electricity, but low photocurrent generation impedes their application. Now, a micro-scale flow-based BPV system is reported with power density outputs similar to that of large-scale biofuels.

Few-layered Ni(OH)2 nanosheets for high-performance supercapacitors

NASA Astrophysics Data System (ADS)

Sun, Wenping; Rui, Xianhong; Ulaganathan, Mani; Madhavi, Srinivasan; Yan, Qingyu

2015-11-01

Few-layered Ni(OH)2 nanosheets (4-5 nm in thickness) are synthesized towards high-performance supercapacitors. The ultrathin Ni(OH)2 nanosheets show high specific capacitance and good rate capability in both three-electrode and asymmetric devices. In the three-electrode device, the Ni(OH)2 nanosheets deliver a high capacitance of 2064 F g-1 at 2 A g-1, and the capacitance still has a retention of 1837 F g-1 at a high current density of 20 A g-1. Such excellent performance is by far one of the best for Ni(OH)2 electrodes. In the two-electrode asymmetric device, the specific capacitance is 248 F g-1 at 1 A g-1, and reaches 113 F g-1 at 20 A g-1. The capacitance of the asymmetric device maintains to be 166 F g-1 during the 4000th cycle at 2 A g-1, suggesting good cycling stability of the device. Besides, the asymmetric device exhibits gravimetric energy density of 22 Wh kg-1 at a power density of 0.8 kW kg-1. The present results demonstrate that the ultrathin Ni(OH)2 nanosheets are highly attractive electrode materials for achieving fast charging/discharging and high-capacity supercapacitors.

Flexible Black-Phosphorus Nanoflake/Carbon Nanotube Composite Paper for High-Performance All-Solid-State Supercapacitors.

PubMed

Yang, Bingchao; Hao, Chunxue; Wen, Fusheng; Wang, Bochong; Mu, Congpu; Xiang, Jianyong; Li, Lei; Xu, Bo; Zhao, Zhisheng; Liu, Zhongyuan; Tian, Yongjun

2017-12-27

We proposed a simple route for fabrication of the flexible BP nanoflake/carbon nanotube (CNT) composite paper as flexible electrodes in all-solid-state supercapacitors. The highly conductive CNTs not only play a role as active materials but also increase conductivity of the hybrid electrode, enhance electrolyte shuttling and prevent the restacking between BP nanoflakes. The fabricated flexible all-solid-state supercapacitor (ASSP) device at the mass proportion of BP/CNTs 1:4 was found to deliver the highest volumetric capacitance of up to 41.1 F/cm 3 at 0.005 V/s, superior to the ASSP based on the bare graphene or BP. The BP/CNTs (1:4) device delivers a rapid charging/discharging up to 500 V/s, which exhibits the characteristic of a high power density of 821.62 W/cm 3 , while having outstanding mechanical flexibility and high cycling stability over 10 000 cycles (91.5% capacitance retained). Moreover the BP/CNTs (1:4) ASSP device still retains large volumetric capacitance (35.7 F/cm 3 at the scan rate of 0.005 V/s) even after 11 months. In addition, the ASSP of BP/CNTs (1:4) exhibits high energy density of 5.71 mWh/cm 3 and high power density of 821.62 W/cm 3 . As indicated in our work, the strategy of assembling stacked-layer composites films will open up novel possibility for realizing BP and CNTs in new-concept thin-film energy storage devices.

Near-Field Thermal Radiation for Solar Thermophotovoltaics and High Temperature Thermal Logic and Memory Applications

NASA Astrophysics Data System (ADS)

Elzouka, Mahmoud

This dissertation investigates Near-Field Thermal Radiation (NFTR) applied to MEMS-based concentrated solar thermophotovoltaics (STPV) energy conversion and thermal memory and logics. NFTR is the exchange of thermal radiation energy at nano/microscale; when separation between the hot and cold objects is less than dominant radiation wavelength (˜1 mum). NFTR is particularly of interest to the above applications due to its high rate of energy transfer, exceeding the blackbody limit by orders of magnitude, and its strong dependence on separation gap size, surface nano/microstructure and material properties. Concentrated STPV system converts solar radiation to electricity using heat as an intermediary through a thermally coupled absorber/emitter, which causes STPV to have one of the highest solar-to-electricity conversion efficiency limits (85.4%). Modeling of a near-field concentrated STPV microsystem is carried out to investigate the use of STPV based solid-state energy conversion as high power density MEMS power generator. Numerical results for In 0.18Ga0.82Sb PV cell illuminated with tungsten emitter showed significant enhancement in energy transfer, resulting in output power densities as high as 60 W/cm2; 30 times higher than the equivalent far-field power density. On thermal computing, this dissertation demonstrates near-field heat transfer enabled high temperature NanoThermoMechanical memory and logics. Unlike electronics, NanoThermoMechanical memory and logic devices use heat instead of electricity to record and process data; hence they can operate in harsh environments where electronics typically fail. NanoThermoMechanical devices achieve memory and thermal rectification functions through the coupling of near-field thermal radiation and thermal expansion in microstructures, resulting in nonlinear heat transfer between two temperature terminals. Numerical modeling of a conceptual NanoThermoMechanical is carried out; results include the dynamic response under write/read cycles for a practical silicon-based device. NanoThermoMechanical rectification is achieved experimentally--for the first time--with measurements at a high temperature of 600 K, demonstrating the feasibility of NanoThermoMechanical to operate in harsh environments. The proof-of-concept device has shown a maximum rectification of 10.9%. This dissertation proposes using meshed photonic crystal structures to enhance NFTR between surfaces. Numerical results show thermal rectification as high as 2500%. Incorporating these structures in thermal memory and rectification devices will significantly enhance their functionality and performance.

Thickness-dependent surface energies of few-layered arsenene and antimonene films in α and β phases

NASA Astrophysics Data System (ADS)

Zhao, N.; Zhu, Y. F.; Jiang, Q.

2018-07-01

Group V elemental few-layered materials with semiconducting electronic properties are emerging as promising 2D layered materials. Since the layered configurations need substrate for device fabrications, their surface energy values could decide their properties. Here, we have performed a systematic density functional theory (DFT) investigation on the surface energies of arsenene and antimonene films as the function of thickness. The results show that the surface energy of β phase increases with increased layered numbers and converges to a constant value at about five layers, while the surface energy of α phase is size-independent. Since the surface energies of both α and β phase are similar, there is the existence possibility of α phase. Those could give references for future manufacture of arsenene and antimonene nano-devices.

Development of High Power Density Micro-Thermoelectric Generators

NASA Astrophysics Data System (ADS)

Zhang, Wenhua

Thermoelectric generators (TEGs) are promising for the waste heat recovery in virtue of the ability to directly convert heat to electricity. Despite of their relatively low energy conversion efficiency, TEGs have many advantages including high reliability, long lifetime, and environmental friendliness. Especially, compared to conventional heat engines, TEGs are compact, scalable, and can be easily driven by small temperature differences. Potential applications of TEGs include thermal sensing, thermal management, and thermal energy harvesting to power wireless sensors and microelectronic devices such as wearable medical sensors and wristwatches. This dissertation presents my work on development of high power density non-flexible and flexible micro-TEGs for thermal energy harvesting in the ambient environment. Micro- TEGs are developed by a bottom-up approach combing electroplating and microfabrication processes. Pulsed electroplating is mainly adopted to deposit thermoelectric materials in the device fabrication. First, I collaborated with Dr. Zhou in our lab and systematically studied the effect of deposition parameters on composition, microstructure, and thermoelectric properties of the electroplated Bi2Te3 and Sb2 Te3 thin films. We demonstrated that thermoelectric properties of both Bi2Te3 and Sb2Te3 films can be enhanced by tuning the pulse off-to-on ratio. After the fundamental study on the deposition conditions, morphology, and thermoelectric properties of the electroplated materials, we fabricated a high power density cross-plane micro-TEG on the SiO2/Si substrate by integrating the pulsed electroplating with microfabrication processes. The TEG consists of a total of 127 pairs of n-type Bi2Te3 and ptype Sb2Te3 thermoelectric pillars embedded in a SU-8 matrix to enhance the overall mechanical strength of the device. Both bottom and top electrical connections are formed by electroplating, which is advantageous because of facile and low cost fabrication and low parasitic electrical resistances. The device demonstrates a maximum power of 2990 muW at a temperature difference of 52.5 K, corresponding to a power density as high as 9.2 mW cm-2. The power density of our device is more than two times the highest value reported for the electroplated micro-TEGs in the literature, which can be attributed to the low internal resistance and high packing density of thermoelectric pillars. Based on my work on non-flexible micro-TEGs, I further modified the device fabrication process and developed an ultra-light high power density flexible micro-TEG. The flexible TEG demonstrates excellent flexibility. No obvious electrical resistance change was observed after bending to a curvature as small as 5 mm for 600 times. The flexible micro-TEG we developed demonstrates a maximum power of 1.5 mW at a temperature difference of 50.7 K, corresponding to a power density of 4.5 mW cm-2. More importantly, the flexible TEG is ultra-light and an unprecedentedly high power per unit mass of 60 mW g-1 is achieved, which might be beneficial for wearable technology.

A Method to Improve Electron Density Measurement of Cone-Beam CT Using Dual Energy Technique

PubMed Central

Men, Kuo; Dai, Jian-Rong; Li, Ming-Hui; Chen, Xin-Yuan; Zhang, Ke; Tian, Yuan; Huang, Peng; Xu, Ying-Jie

2015-01-01

Purpose. To develop a dual energy imaging method to improve the accuracy of electron density measurement with a cone-beam CT (CBCT) device. Materials and Methods. The imaging system is the XVI CBCT system on Elekta Synergy linac. Projection data were acquired with the high and low energy X-ray, respectively, to set up a basis material decomposition model. Virtual phantom simulation and phantoms experiments were carried out for quantitative evaluation of the method. Phantoms were also scanned twice with the high and low energy X-ray, respectively. The data were decomposed into projections of the two basis material coefficients according to the model set up earlier. The two sets of decomposed projections were used to reconstruct CBCT images of the basis material coefficients. Then, the images of electron densities were calculated with these CBCT images. Results. The difference between the calculated and theoretical values was within 2% and the correlation coefficient of them was about 1.0. The dual energy imaging method obtained more accurate electron density values and reduced the beam hardening artifacts obviously. Conclusion. A novel dual energy CBCT imaging method to calculate the electron densities was developed. It can acquire more accurate values and provide a platform potentially for dose calculation. PMID:26346510

Optimization of power and energy densities in supercapacitors

NASA Astrophysics Data System (ADS)

Robinson, David B.

Supercapacitors use nanoporous electrodes to store large amounts of charge on their high surface areas, and use the ions in electrolytes to carry charge into the pores. Their high power density makes them a potentially useful complement to batteries. However, ion transport through long, narrow channels still limits power and efficiency in these devices. Proper design can mitigate this. Current collector geometry must also be considered once this is done. Here, De Levie's model for porous electrodes is applied to quantitatively predict device performance and to propose optimal device designs for given specifications. Effects unique to nanoscale pores are considered, including that pores may not have enough salt to fully charge. Supercapacitors are of value for electric vehicles, portable electronics, and power conditioning in electrical grids with distributed renewable sources, and that value will increase as new device fabrication methods are developed and proper design accommodates those improvements. Example design outlines for vehicle applications are proposed and compared.

Ternary Au/ZnO/rGO nanocomposites electrodes for high performance electrochemical storage devices

NASA Astrophysics Data System (ADS)

Chaudhary, Manchal; Doong, Ruey-an; Kumar, Nagesh; Tseng, Tseung Yuen

2017-10-01

The combination of metal and metal oxide nanoparticles with reduced graphene oxides (rGO) is an active electrode material for electrochemical storage devices. Herein, we have, for the first time, reported the fabrication of ternary Au/ZnO/rGO nanocomposites by using a rapid and environmentally friendly microwave-assisted hydrothermal method for high performance supercapacitor applications. The ZnO/rGO provides excellent electrical conductivity and good macro/mesopore structures, which can facilitate the rapid electrons and ions transport. The Au nanoparticles with particle sizes of 7-12 nm are homogeneously distributed onto the ZnO/rGO surface to enhance the electrochemical performance by retaining the capacitance at high current density. The Au/ZnO/rGO nanocomposites, prepared with the optimized rGO amount of 100 mg exhibit a high specific capacitance of 875 and 424 F g-1 at current densities of 1 and 20 A g-1, respectively, in 2 M KOH. In addition, the energy and power densities of ternary Au/ZnO/rGO can be up to 17.6-36.5 Wh kg-1 and 0.27-5.42 kW kg-1, respectively. Results obtained in this study clearly demonstrate the excellence of ternary Au/ZnO/rGO nanocomposites as the active electrode materials for electrochemical pseudocapacitor performance and can open an avenue to fabricate metal/metal oxide/rGO nanocomposites for electrochemical storage devices with both high energy and power densities.

Reviving lithium cobalt oxide-based lithium secondary batteries-toward a higher energy density.

PubMed

Wang, Longlong; Chen, Bingbing; Ma, Jun; Cui, Guanglei; Chen, Liquan

2018-06-29

By breaking through the energy density limits step-by-step, the use of lithium cobalt oxide-based Li-ion batteries (LCO-based LIBs) has led to the unprecedented success of consumer electronics over the past 27 years. Recently, strong demands for the quick renewal of the properties of electronic products every so often have resulted in smarter, larger screened, more lightweight devices with longer standby times that have pushed the energy density of LCO-based LIBs nearly to their limit. As a result, with the aim of achieving a higher energy density and lifting the upper cut-off voltage of LCO above 4.45 V (vs. Li/Li+), the development of LCO-based all-solid-state lithium batteries (ASSLBs) with a Li metal anode and LCO-based full cells with high-performance anodes have become urgent scientific and technological requirements. This review summarizes the key challenges of synthesizing LCO-based LBs with a higher energy density from the perspectives of structure and interface stability, and gives an account of effective modification strategies in view of the electrodes, liquid electrolytes, binders, separators, solid electrolytes and LCO-based full cells. The improvement mechanisms of these modification strategies and the controversy over them are also analyzed critically. Moreover, some perspectives regarding the remaining challenges for LCO-based LBs towards a higher energy density and possible future research focuses are also presented.

Determination of bulk and interface density of states in metal oxide semiconductor thin-film transistors by using capacitance-voltage characteristics

NASA Astrophysics Data System (ADS)

Wei, Xixiong; Deng, Wanling; Fang, Jielin; Ma, Xiaoyu; Huang, Junkai

2017-10-01

A physical-based straightforward extraction technique for interface and bulk density of states in metal oxide semiconductor thin film transistors (TFTs) is proposed by using the capacitance-voltage (C-V) characteristics. The interface trap density distribution with energy has been extracted from the analysis of capacitance-voltage characteristics. Using the obtained interface state distribution, the bulk trap density has been determined. With this method, for the interface trap density, it is found that deep state density nearing the mid-gap is approximately constant and tail states density increases exponentially with energy; for the bulk trap density, it is a superposition of exponential deep states and exponential tail states. The validity of the extraction is verified by comparisons with the measured current-voltage (I-V) characteristics and the simulation results by the technology computer-aided design (TCAD) model. This extraction method uses non-numerical iteration which is simple, fast and accurate. Therefore, it is very useful for TFT device characterization.

Powering a leadless pacemaker using a PiezoMEMS energy harvester

NASA Astrophysics Data System (ADS)

Jackson, Nathan; Olszewski, Oskar; O'Murchu, Cian; Mathewson, Alan

2017-06-01

MEMS based vibrational energy harvesting devices have been a highly researched topic over the past decade. The application targeted in this paper focuses on a leadless pacemaker that will be implanted in the right ventricle of the heart. A leadless pacemaker requires the same functionality as a normal pacemaker, but with significantly reduced volume. The reduced volume limits the space for a battery; therefore an energy harvesting device is required. This paper compares varying the dimensions of a linear MEMS based piezoelectric energy harvester that can harvest energy from the mechanical vibrations of the heart due to shock induced vibration. Typical MEMS linear energy harvesting devices operate at high frequency (<50 Hz) with low acceleration (< 1g). The force generated from the heart acts as a series of impulses as opposed to traditional sinusoidal vibration force with high acceleration (1-4 g). Therefore the design of a MEMS harvester that is based on shock-induced vibration is necessary. PiezoMEMS energy harvesting devices consisting of a silicon substrate and mass with aluminium nitride piezoelectric material were developed and characterized using acceleration forces that mimic the heartbeat. Peak powers of up to 25μW were obtained at 1 g acceleration with a powder density of approximately 1.5 mW cm-3.

Radial Shock Wave Devices Generate Cavitation

PubMed Central

Császár, Nikolaus B. M.; Angstman, Nicholas B.; Milz, Stefan; Sprecher, Christoph M.; Kobel, Philippe; Farhat, Mohamed; Furia, John P.; Schmitz, Christoph

2015-01-01

Background Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT) devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues. Methods and Findings We used laser fiber optic probe hydrophone (FOPH) measurements, high-speed imaging and x-ray film analysis to compare fundamental elements of the energy signatures of two rESWT devices (Swiss DolorClast; Electro Medical Systems, Nyon, Switzerland; D-Actor 200; Storz Medical, Tägerwillen, Switzerland) and a vibrating massage device (Vibracare; G5/General Physiotherapy, Inc., Earth City, MO, USA). To assert potential bioeffects of these treatment modalities we investigated the influence of rESWT and vibrating massage devices on locomotion ability of Caenorhabditis elegans (C. elegans) worms. Results FOPH measurements demonstrated that both rESWT devices generated acoustic waves with comparable pressure and energy flux density. Furthermore, both rESWT devices generated cavitation as evidenced by high-speed imaging and caused mechanical damage on the surface of x-ray film. The vibrating massage device did not show any of these characteristics. Moreover, locomotion ability of C. elegans was statistically significantly impaired after exposure to radial extracorporeal shock waves but was unaffected after exposure of worms to the vibrating massage device. Conclusions The results of the present study indicate that both energy signature and bioeffects of rESWT devices are fundamentally different from those of vibrating massage devices. Clinical Relevance Prior ESWT studies have shown that tissues treated with sufficient quantities of acoustic sound waves undergo cavitation build-up, mechanotransduction, and ultimately, a biological alteration that “kick-starts” the healing response. Due to their different treatment indications and contra-indications rESWT devices cannot be equated to vibrating massage devices and should be used with due caution in clinical practice. PMID:26509573

Radial Shock Wave Devices Generate Cavitation.

PubMed

Császár, Nikolaus B M; Angstman, Nicholas B; Milz, Stefan; Sprecher, Christoph M; Kobel, Philippe; Farhat, Mohamed; Furia, John P; Schmitz, Christoph

2015-01-01

Conflicting reports in the literature have raised the question whether radial extracorporeal shock wave therapy (rESWT) devices and vibrating massage devices have similar energy signatures and, hence, cause similar bioeffects in treated tissues. We used laser fiber optic probe hydrophone (FOPH) measurements, high-speed imaging and x-ray film analysis to compare fundamental elements of the energy signatures of two rESWT devices (Swiss DolorClast; Electro Medical Systems, Nyon, Switzerland; D-Actor 200; Storz Medical, Tägerwillen, Switzerland) and a vibrating massage device (Vibracare; G5/General Physiotherapy, Inc., Earth City, MO, USA). To assert potential bioeffects of these treatment modalities we investigated the influence of rESWT and vibrating massage devices on locomotion ability of Caenorhabditis elegans (C. elegans) worms. FOPH measurements demonstrated that both rESWT devices generated acoustic waves with comparable pressure and energy flux density. Furthermore, both rESWT devices generated cavitation as evidenced by high-speed imaging and caused mechanical damage on the surface of x-ray film. The vibrating massage device did not show any of these characteristics. Moreover, locomotion ability of C. elegans was statistically significantly impaired after exposure to radial extracorporeal shock waves but was unaffected after exposure of worms to the vibrating massage device. The results of the present study indicate that both energy signature and bioeffects of rESWT devices are fundamentally different from those of vibrating massage devices. Prior ESWT studies have shown that tissues treated with sufficient quantities of acoustic sound waves undergo cavitation build-up, mechanotransduction, and ultimately, a biological alteration that "kick-starts" the healing response. Due to their different treatment indications and contra-indications rESWT devices cannot be equated to vibrating massage devices and should be used with due caution in clinical practice.

High Performance Lithium-Ion Hybrid Capacitors Employing Fe3O4-Graphene Composite Anode and Activated Carbon Cathode.

PubMed

Zhang, Shijia; Li, Chen; Zhang, Xiong; Sun, Xianzhong; Wang, Kai; Ma, Yanwei

2017-05-24

Lithium-ion capacitors (LICs) are considered as promising energy storage devices to realize excellent electrochemical performance, with high energy-power output. In this work, we employed a simple method to synthesize a composite electrode material consisting of Fe 3 O 4 nanocrystallites mechanically anchored among the layers of three-dimensional arrays of graphene (Fe 3 O 4 -G), which exhibits several advantages compared with other traditional electrode materials, such as high Li storage capacity (820 mAh g -1 at 0.1 A g -1 ), high electrical conductivity, and improved electrochemical stability. Furthermore, on the basis of the appropriated charge balance between cathode and anode, we successfully fabricated Fe 3 O 4 -G//activated carbon (AC) soft-packaging LICs with a high energy density of 120.0 Wh kg -1 , an outstanding power density of 45.4 kW kg -1 (achieved at 60.5 Wh kg -1 ), and an excellent capacity retention of up to 94.1% after 1000 cycles and 81.4% after 10 000 cycles. The energy density of the Fe 3 O 4 -G//AC hybrid device is comparable with Ni-metal hydride batteries, and its capacitive power capability and cycle life is on par with supercapacitors (SCs). Therefore, this lithium-ion hybrid capacitor is expected to bridge the gap between Li-ion battery and SCs and gain bright prospects in next-generation energy storage fields.

Nanowire modified carbon fibers for enhanced electrical energy storage

NASA Astrophysics Data System (ADS)

Shuvo, Mohammad Arif Ishtiaque; (Bill) Tseng, Tzu-Liang; Ashiqur Rahaman Khan, Md.; Karim, Hasanul; Morton, Philip; Delfin, Diego; Lin, Yirong

2013-09-01

The study of electrochemical super-capacitors has become one of the most attractive topics in both academia and industry as energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles, and portable electronics. These multifunctional structural super-capacitors provide structures combining energy storage and load bearing functionalities, leading to material systems with reduced volume and/or weight. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires, which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area thus fast ion diffusion rates. Scanning Electron Microscopy and X-Ray Diffraction measurements are used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing is performed using a potentio-galvanostat. The results show that gold sputtered nanowire carbon fiber hybrid provides 65.9% higher energy density than bare carbon fiber cloth as super-capacitor.

Retrieving acoustic energy densities and local pressure amplitudes in microfluidics by holographic time-lapse imaging.

PubMed

Cacace, Teresa; Bianco, Vittorio; Paturzo, Melania; Memmolo, Pasquale; Vassalli, Massimo; Fraldi, Massimiliano; Mensitieri, Giuseppe; Ferraro, Pietro

2018-06-26

The development of techniques able to characterize and map the pressure field is crucial for the widespread use of acoustofluidic devices in biotechnology and lab-on-a-chip platforms. In fact, acoustofluidic devices are powerful tools for driving precise manipulation of microparticles and cells in microfluidics in non-contact modality. Here, we report a full and accurate characterization of the movement of particles subjected to acoustophoresis in a microfluidic environment by holographic imaging. The particle displacement along the direction of the ultrasound wave propagation, coinciding with the optical axis, is observed and investigated. Two resonance frequencies are explored, varying for each the amplitude of the applied signal. The trajectories of individual tracers, accomplished by holographic measurements, are fitted with the theoretical model thus allowing the retrieval of the acoustic energy densities and pressure amplitudes through full holographic analysis. The absence of prior calibration, being independent of the object shape and the possibility of implementing automatic analysis make the use of holography very appealing for applications in devices for biotechnologies.

High-density magnetoresistive random access memory operating at ultralow voltage at room temperature.

PubMed

Hu, Jia-Mian; Li, Zheng; Chen, Long-Qing; Nan, Ce-Wen

2011-11-22

The main bottlenecks limiting the practical applications of current magnetoresistive random access memory (MRAM) technology are its low storage density and high writing energy consumption. Although a number of proposals have been reported for voltage-controlled memory device in recent years, none of them simultaneously satisfy the important device attributes: high storage capacity, low power consumption and room temperature operation. Here we present, using phase-field simulations, a simple and new pathway towards high-performance MRAMs that display significant improvements over existing MRAM technologies or proposed concepts. The proposed nanoscale MRAM device simultaneously exhibits ultrahigh storage capacity of up to 88 Gb inch(-2), ultralow power dissipation as low as 0.16 fJ per bit and room temperature high-speed operation below 10 ns.

High-density magnetoresistive random access memory operating at ultralow voltage at room temperature

PubMed Central

Hu, Jia-Mian; Li, Zheng; Chen, Long-Qing; Nan, Ce-Wen

2011-01-01

The main bottlenecks limiting the practical applications of current magnetoresistive random access memory (MRAM) technology are its low storage density and high writing energy consumption. Although a number of proposals have been reported for voltage-controlled memory device in recent years, none of them simultaneously satisfy the important device attributes: high storage capacity, low power consumption and room temperature operation. Here we present, using phase-field simulations, a simple and new pathway towards high-performance MRAMs that display significant improvements over existing MRAM technologies or proposed concepts. The proposed nanoscale MRAM device simultaneously exhibits ultrahigh storage capacity of up to 88 Gb inch−2, ultralow power dissipation as low as 0.16 fJ per bit and room temperature high-speed operation below 10 ns. PMID:22109527

Giant energy density and high efficiency achieved in bismuth ferrite-based film capacitors via domain engineering.

PubMed

Pan, Hao; Ma, Jing; Ma, Ji; Zhang, Qinghua; Liu, Xiaozhi; Guan, Bo; Gu, Lin; Zhang, Xin; Zhang, Yu-Jun; Li, Liangliang; Shen, Yang; Lin, Yuan-Hua; Nan, Ce-Wen

2018-05-08

Developing high-performance film dielectrics for capacitive energy storage has been a great challenge for modern electrical devices. Despite good results obtained in lead titanate-based dielectrics, lead-free alternatives are strongly desirable due to environmental concerns. Here we demonstrate that giant energy densities of ~70 J cm -3 , together with high efficiency as well as excellent cycling and thermal stability, can be achieved in lead-free bismuth ferrite-strontium titanate solid-solution films through domain engineering. It is revealed that the incorporation of strontium titanate transforms the ferroelectric micro-domains of bismuth ferrite into highly-dynamic polar nano-regions, resulting in a ferroelectric to relaxor-ferroelectric transition with concurrently improved energy density and efficiency. Additionally, the introduction of strontium titanate greatly improves the electrical insulation and breakdown strength of the films by suppressing the formation of oxygen vacancies. This work opens up a feasible and propagable route, i.e., domain engineering, to systematically develop new lead-free dielectrics for energy storage.

Optimization principles and the figure of merit for triboelectric generators.

PubMed

Peng, Jun; Kang, Stephen Dongmin; Snyder, G Jeffrey

2017-12-01

Energy harvesting with triboelectric nanogenerators is a burgeoning field, with a growing portfolio of creative application schemes attracting much interest. Although power generation capabilities and its optimization are one of the most important subjects, a satisfactory elemental model that illustrates the basic principles and sets the optimization guideline remains elusive. We use a simple model to clarify how the energy generation mechanism is electrostatic induction but with a time-varying character that makes the optimal matching for power generation more restrictive. By combining multiple parameters into dimensionless variables, we pinpoint the optimum condition with only two independent parameters, leading to predictions of the maximum limit of power density, which allows us to derive the triboelectric material and device figure of merit. We reveal the importance of optimizing device capacitance, not only load resistance, and minimizing the impact of parasitic capacitance. Optimized capacitances can lead to an overall increase in power density of more than 10 times.

On the design of random metasurface based devices.

PubMed

Dupré, Matthieu; Hsu, Liyi; Kanté, Boubacar

2018-05-08

Metasurfaces are generally designed by placing scatterers in periodic or pseudo-periodic grids. We propose and discuss design rules for functional metasurfaces with randomly placed anisotropic elements that randomly sample a well-defined phase function. By analyzing the focusing performance of random metasurface lenses as a function of their density and the density of the phase-maps used to design them, we find that the performance of 1D metasurfaces is mostly governed by their density while 2D metasurfaces strongly depend on both the density and the near-field coupling configuration of the surface. The proposed approach is used to design all-polarization random metalenses at near infrared frequencies. Challenges, as well as opportunities of random metasurfaces compared to periodic ones are discussed. Our results pave the way to new approaches in the design of nanophotonic structures and devices from lenses to solar energy concentrators.

Scaling the Shear-flow Stabilized Z-pinch to Reactor Conditions

NASA Astrophysics Data System (ADS)

McLean, H. S.; Schmidt, A.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Cleveau, E.

2015-11-01

We present a conceptual design along with scaling calculations for a pulsed fusion reactor based on the shear-flow-stabilized Z-pinch device. Experiments performed on the ZaP device, at the University of Washington, have demonstrated stable operation for durations of 20 usec at ~100kA discharge current for pinches that are ~1 cm in diameter and 100 cm long. The inverse of the pinch diameter and plasma energy density scale strongly with pinch current and calculations show that maintaining stabilization durations of ~7 usec for increased discharge current (~15x) in a shortened pinch (10 cm) results in a pinch diameter of ~200 um and plasma conditions that approach those needed to support significant fusion burn and energy gain (Ti ~ 30keV, density ~ 3e26/m3, ntau ~1.4e20 sec/m3). Compelling features of the concept include operation at modest discharge current (1.5 MA) and voltage (40kV) along with direct adoption of liquid metals for at least one electrode--technological capabilities that have been proven in existing, commercial, pulse power devices such as large ignitrons. LLNL-ABS-674920. This work performed under the auspices of the U.S. Department of Energy ARPAe ALPHA Program by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.

Nanostructured CuS networks composed of interconnected nanoparticles for asymmetric supercapacitors.

PubMed

Fu, Wenbin; Han, Weihua; Zha, Heming; Mei, Junfeng; Li, Yunxia; Zhang, Zemin; Xie, Erqing

2016-09-21

Nanostructured metal sulfides with excellent electrochemical activity and electrical conductivity are particularly promising for applications in high-performance energy storage devices. Here, we report on the facile synthesis of nanostructured CuS networks composed of interconnected nanoparticles as novel battery-type materials for asymmetric supercapacitors. We find that the CuS networks exhibit a high specific capacity of 49.8 mA g(-1) at a current density of 1 A g(-1), good rate capability and cycle stability. The superior performance could be attributed to the interconnected nanoparticles of CuS networks, which can facilitate electrolyte diffusion and provide fast electron pathways. Furthermore, an aqueous asymmetric supercapacitor has been assembled by using the CuS networks as the positive electrode and activated carbon as the negative electrode. The assembled device can work at a high operating voltage of 1.6 V and show a maximum energy density of 17.7 W h kg(-1) at a power density of 504 W kg(-1). This study indicates that the CuS networks have great potential for supercapacitor applications.

Synthesis and Characterisation of Reduced Graphene Oxide/Bismuth Composite for Electrodes in Electrochemical Energy Storage Devices.

PubMed

Wang, Jiabin; Zhang, Han; Hunt, Michael R C; Charles, Alasdair; Tang, Jie; Bretcanu, Oana; Walker, David; Hassan, Khalil T; Sun, Yige; Šiller, Lidija

2017-01-20

A reduced graphene oxide/bismuth (rGO/Bi) composite was synthesized for the first time using a polyol process at a low reaction temperature and with a short reaction time (60 °C and 3 hours, respectively). The as-prepared sample is structured with 20-50 nm diameter bismuth particles distributed on the rGO sheets. The rGO/Bi composite displays a combination of capacitive and battery-like charge storage, achieving a specific capacity value of 773 C g -1 at a current density of 0.2 A g -1 when charged to 1 V. The material not only has good power density but also shows moderate stability in cycling tests with current densities as high as 5 A g -1 . The relatively high abundance and low price of bismuth make this rGO/Bi material a promising candidate for use in electrode materials in future energy storage devices. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Coated Porous Si for High Performance On-Chip Supercapacitors

NASA Astrophysics Data System (ADS)

Grigoras, K.; Keskinen, J.; Grönberg, L.; Ahopelto, J.; Prunnila, M.

2014-11-01

High performance porous Si based supercapacitor electrodes are demonstrated. High power density and stability is provided by ultra-thin TiN coating of the porous Si matrix. The TiN layer is deposited by atomic layer deposition (ALD), which provides sufficient conformality to reach the bottom of the high aspect ratio pores. Our porous Si supercapacitor devices exhibit almost ideal double layer capacitor characteristic with electrode volumetric capacitance of 7.3 F/cm3. Several orders of magnitude increase in power and energy density is obtained comparing to uncoated porous silicon electrodes. Good stability of devices is confirmed performing several thousands of charge/discharge cycles.

A Novel High Energy Density Rechargeable Hybrid Sodium-Air Cell with Acidic Electrolyte.

PubMed

Kang, Yao; Su, Fengmei; Zhang, Qingkai; Liang, Feng; Adair, Keegan R; Chen, Kunfeng; Xue, Dongfeng; Hayashi, Katsuro; Cao, Shan Cecilia; Yadegari, Hossein; Sun, Xueliang

2018-06-22

Low cost, high energy density and highly efficient devices for energy storage have long been desired in our society. Herein, a novel high energy density hybrid sodium-air cell was fabricated successfully based on acidic catholytes. Such a hybrid sodium-air cell possess a high theoretical voltage of 3.94 V, capacity of 1121 mAh g-1, and energy density of 4418 Wh kg-1. Firstly, the buffering effect of an acidic solution was demonstrated, which provides relatively long and stable cell discharge behaviours. Secondly, the catholyte of hybrid sodium-air cells were optimized systematically from the solutions of 0.1 M H3PO4 + 0.1 M Na2SO4 to 0.1 M HAc + 0.1 M NaAc, and it was found that the cells with 0.1 M H3PO4 + 0.1 M Na2SO4 displayed maximum power density of 34.9 mW cm-2. The cell with 0.1 M H3PO4 + 0.1 M Na2SO4 displayed higher discharge capacity of 896 mAh g-1. Moreover, the fabricated acidic hybrid sodium-air cells exhibited stable cycling performance in ambient air, and they delivered a low voltage gap around 0.3 V when the current density is 0.13 mA cm-2, leading to a high energy efficiency up to 90%. Therefore, the present study provides new opportunities to develop highly cost-effective energy storage technologies.

Evaluation strategy of regenerative braking energy for supercapacitor vehicle.

PubMed

Zou, Zhongyue; Cao, Junyi; Cao, Binggang; Chen, Wen

2015-03-01

In order to improve the efficiency of energy conversion and increase the driving range of electric vehicles, the regenerative energy captured during braking process is stored in the energy storage devices and then will be re-used. Due to the high power density of supercapacitors, they are employed to withstand high current in the short time and essentially capture more regenerative energy. The measuring methods for regenerative energy should be investigated to estimate the energy conversion efficiency and performance of electric vehicles. Based on the analysis of the regenerative braking energy system of a supercapacitor vehicle, an evaluation system for energy recovery in the braking process is established using USB portable data-acquisition devices. Experiments under various braking conditions are carried out. The results verify the higher efficiency of energy regeneration system using supercapacitors and the effectiveness of the proposed measurement method. It is also demonstrated that the maximum regenerative energy conversion efficiency can reach to 88%. Copyright © 2014 ISA. Published by Elsevier Ltd. All rights reserved.

High-Energy-Density Metal-Oxygen Batteries: Lithium-Oxygen Batteries vs Sodium-Oxygen Batteries.

PubMed

Song, Kyeongse; Agyeman, Daniel Adjei; Park, Mihui; Yang, Junghoon; Kang, Yong-Mook

2017-12-01

The development of next-generation energy-storage devices with high power, high energy density, and safety is critical for the success of large-scale energy-storage systems (ESSs), such as electric vehicles. Rechargeable sodium-oxygen (Na-O 2 ) batteries offer a new and promising opportunity for low-cost, high-energy-density, and relatively efficient electrochemical systems. Although the specific energy density of the Na-O 2 battery is lower than that of the lithium-oxygen (Li-O 2 ) battery, the abundance and low cost of sodium resources offer major advantages for its practical application in the near future. However, little has so far been reported regarding the cell chemistry, to explain the rate-limiting parameters and the corresponding low round-trip efficiency and cycle degradation. Consequently, an elucidation of the reaction mechanism is needed for both lithium-oxygen and sodium-oxygen cells. An in-depth understanding of the differences and similarities between Li-O 2 and Na-O 2 battery systems, in terms of thermodynamics and a structural viewpoint, will be meaningful to promote the development of advanced metal-oxygen batteries. State-of-the-art battery design principles for high-energy-density lithium-oxygen and sodium-oxygen batteries are thus reviewed in depth here. Major drawbacks, reaction mechanisms, and recent strategies to improve performance are also summarized. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Controlled synthesis of nanostructured molybdenum oxide electrodes for high performance supercapacitor devices

NASA Astrophysics Data System (ADS)

Maheswari, Nallappan; Muralidharan, Gopalan

2017-09-01

Well defined crystallographic and one dimensional morphological structure of molybdenum oxide were successfully synthesized by adjusting the duration of hydrothermal treatment. The prepared molybdenum oxide was examined through XRD, SEM, FTIR, TEM, BET and electrochemical studies. The XRD patterns illustrate that MoOx prepared by variying the hydrothermal reaction time are in different crystallographic structure of MoyOx (Mo8O23 and MoO3). SEM studies reveal the different morphological structures ranging from flake like morphology to nanorods. TEM images confirm the excellent nanorod structure. The nanorod structure ensures good cyclic behaviour with maximum capacitance of 1080 F g-1 at a current density of 2 A g-1. This large capacity of the MoO3 nanostructures enabled fabrication of symmetric and asymmertic supercapacitor devices. The asymmertic device exhibits a maximum specific capacitance of 145 F g-1 at 2 mV s-1 with highest energy density of 38.6 W h kg-1 at 374.7 W kg-1 power density.

Optoelectronically probing the density of nanowire surface trap states to the single state limit

NASA Astrophysics Data System (ADS)

Dan, Yaping

2015-02-01

Surface trap states play a dominant role in the optoelectronic properties of nanoscale devices. Understanding the surface trap states allows us to properly engineer the device surfaces for better performance. But characterization of surface trap states at nanoscale has been a formidable challenge using the traditional capacitive techniques. Here, we demonstrate a simple but powerful optoelectronic method to probe the density of nanowire surface trap states to the single state limit. In this method, we choose to tune the quasi-Fermi level across the bandgap of a silicon nanowire photoconductor, allowing for capture and emission of photogenerated charge carriers by surface trap states. The experimental data show that the energy density of nanowire surface trap states is in a range from 109 cm-2/eV at deep levels to 1012 cm-2/eV near the conduction band edge. This optoelectronic method allows us to conveniently probe trap states of ultra-scaled nano/quantum devices at extremely high precision.

Study on the photoresponse of amorphous In-Ga-Zn-O and zinc oxynitride semiconductor devices by the extraction of sub-gap-state distribution and device simulation.

PubMed

Jang, Jun Tae; Park, Jozeph; Ahn, Byung Du; Kim, Dong Myong; Choi, Sung-Jin; Kim, Hyun-Suk; Kim, Dae Hwan

2015-07-22

Persistent photoconduction (PPC) is a phenomenon that limits the application of oxide semiconductor thin-film transistors (TFTs) in optical sensor-embedded displays. In the present work, a study on zinc oxynitride (ZnON) semiconductor TFTs based on the combination of experimental results and device simulation is presented. Devices incorporating ZnON semiconductors exhibit negligible PPC effects compared with amorphous In-Ga-Zn-O (a-IGZO) TFTs, and the difference between the two types of materials are examined by monochromatic photonic C-V spectroscopy (MPCVS). The latter method allows the estimation of the density of subgap states in the semiconductor, which may account for the different behavior of ZnON and IGZO materials with respect to illumination and the associated PPC. In the case of a-IGZO TFTs, the oxygen flow rate during the sputter deposition of a-IGZO is found to influence the amount of PPC. Small oxygen flow rates result in pronounced PPC, and large densities of valence band tail (VBT) states are observed in the corresponding devices. This implies a dependence of PPC on the amount of oxygen vacancies (VO). On the other hand, ZnON has a smaller bandgap than a-IGZO and contains a smaller density of VBT states over the entire range of its bandgap energy. Here, the concept of activation energy window (AEW) is introduced to explain the occurrence of PPC effects by photoinduced electron doping, which is likely to be associated with the formation of peroxides in the semiconductor. The analytical methodology presented in this report accounts well for the reduction of PPC in ZnON TFTs, and provides a quantitative tool for the systematic development of phototransistors for optical sensor-embedded interactive displays.

Charge Trapping in Interface Doped MNOS Structures.

DTIC Science & Technology

1981-07-01

Current density 55 0 JN Current density in nitride at gate 55 k Boltzmann’s constant: 1.38 x 10-23 joule /0K 85 m Effective mass of carrier 89 xi MIS...Trap Barrier Lowering by Applied Field: Poole-Frenkel Effect 90 vi Figure 3- 2: Thermally Stimulated Current System 92 Figure 3- 3: TSC Curves from a...Tungsten Atomic Concentration vs Effective Thickness 175 ix List of Tables Table 1-1: Trap Energy Levels and Spatial Densities 31 Table 2-1: Device

Proposal and Evaluation of BLE Discovery Process Based on New Features of Bluetooth 5.0.

PubMed

Hernández-Solana, Ángela; Perez-Diaz-de-Cerio, David; Valdovinos, Antonio; Valenzuela, Jose Luis

2017-08-30

The device discovery process is one of the most crucial aspects in real deployments of sensor networks. Recently, several works have analyzed the topic of Bluetooth Low Energy (BLE) device discovery through analytical or simulation models limited to version 4.x. Non-connectable and non-scannable undirected advertising has been shown to be a reliable alternative for discovering a high number of devices in a relatively short time period. However, new features of Bluetooth 5.0 allow us to define a variant on the device discovery process, based on BLE scannable undirected advertising events, which results in higher discovering capacities and also lower power consumption. In order to characterize this new device discovery process, we experimentally model the real device behavior of BLE scannable undirected advertising events. Non-detection packet probability, discovery probability, and discovery latency for a varying number of devices and parameters are compared by simulations and experimental measurements. We demonstrate that our proposal outperforms previous works, diminishing the discovery time and increasing the potential user device density. A mathematical model is also developed in order to easily obtain a measure of the potential capacity in high density scenarios.

Proposal and Evaluation of BLE Discovery Process Based on New Features of Bluetooth 5.0

PubMed Central

2017-01-01

The device discovery process is one of the most crucial aspects in real deployments of sensor networks. Recently, several works have analyzed the topic of Bluetooth Low Energy (BLE) device discovery through analytical or simulation models limited to version 4.x. Non-connectable and non-scannable undirected advertising has been shown to be a reliable alternative for discovering a high number of devices in a relatively short time period. However, new features of Bluetooth 5.0 allow us to define a variant on the device discovery process, based on BLE scannable undirected advertising events, which results in higher discovering capacities and also lower power consumption. In order to characterize this new device discovery process, we experimentally model the real device behavior of BLE scannable undirected advertising events. Non-detection packet probability, discovery probability, and discovery latency for a varying number of devices and parameters are compared by simulations and experimental measurements. We demonstrate that our proposal outperforms previous works, diminishing the discovery time and increasing the potential user device density. A mathematical model is also developed in order to easily obtain a measure of the potential capacity in high density scenarios. PMID:28867786

All-Solid-State High-Energy Asymmetric Supercapacitors Enabled by Three-Dimensional Mixed-Valent MnOx Nanospike and Graphene Electrodes.

PubMed

Yang, Jie; Li, Guizhu; Pan, Zhenghui; Liu, Meinan; Hou, Yuan; Xu, Yijun; Deng, Hong; Sheng, Leimei; Zhao, Xinluo; Qiu, Yongcai; Zhang, Yuegang

2015-10-14

Three-dimensional (3D) nanostructures enable high-energy storage devices. Here we report a 3D manganese oxide nanospike (NSP) array electrode fabricated by anodization and subsequent electrodeposition. All-solid-state asymmetric supercapacitors were assembled with the 3D Al@Ni@MnOx NSP as the positive electrode, chemically converted graphene (CCG) as the negative electrode, and Na2SO4/poly(vinyl alcohol) (PVA) as the polymer gel electrolyte. Taking advantage of the different potential windows of Al@Ni@MnOx NSP and CCG electrodes, the asymmetric supercapacitor showed an ideal capacitive behavior with a cell voltage up to 1.8 V, capable of lighting up a red LED indicator (nominal voltage of 1.8 V). The device could deliver an energy density of 23.02 W h kg(-1) at a current density of 1 A g(-1). It could also preserve 96.3% of its initial capacitance at a current density of 2 A g(-1) after 10000 charging/discharging cycles. The remarkable performance is attributed to the unique 3D NSP array structure that could play an important role in increasing the effective electrode surface area, facilitating electrolyte permeation, and shortening the electron pathway in the active materials.

Flexible, transparent and exceptionally high power output nanogenerators based on ultrathin ZnO nanoflakes

NASA Astrophysics Data System (ADS)

van Ngoc, Huynh; Kang, Dae Joon

2016-02-01

Novel nanogenerator structures composed of ZnO nanoflakes of less than 10 nm thickness were fabricated using a novel method involving a facile synthetic route and a rational design. The fabricated nanogenerators exhibited a short-circuit current density of 67 μA cm-2, a peak-to-peak open-circuit voltage of 110 V, and an overall output power density exceeding 1.2 mW cm-2, and to the best of our knowledge, these are the best values that have been reported so far in the literature on ZnO-based nanogenerators. We demonstrated that our nanogenerator design could instantaneously power 20 commercial green light-emitting diodes without any additional energy storage processes. Both the facile synthetic route for the ZnO nanoflakes and the straightforward device fabrication process present great scaling potential in order to power mobile and personal electronics that can be used in smart wearable systems, transparent and flexible devices, implantable telemetric energy receivers, electronic emergency equipment, and other self-powered nano/micro devices.Novel nanogenerator structures composed of ZnO nanoflakes of less than 10 nm thickness were fabricated using a novel method involving a facile synthetic route and a rational design. The fabricated nanogenerators exhibited a short-circuit current density of 67 μA cm-2, a peak-to-peak open-circuit voltage of 110 V, and an overall output power density exceeding 1.2 mW cm-2, and to the best of our knowledge, these are the best values that have been reported so far in the literature on ZnO-based nanogenerators. We demonstrated that our nanogenerator design could instantaneously power 20 commercial green light-emitting diodes without any additional energy storage processes. Both the facile synthetic route for the ZnO nanoflakes and the straightforward device fabrication process present great scaling potential in order to power mobile and personal electronics that can be used in smart wearable systems, transparent and flexible devices, implantable telemetric energy receivers, electronic emergency equipment, and other self-powered nano/micro devices. Electronic supplementary information (ESI) available: FE-SEM images of ZnO NFs grown on textile and FTO/glass substrates, XRD patterns of synthesized ZnO NFs, nitrogen adsorption isotherms for ZnO NWs and ZnO NFs, effect of different coating layers on ZnO NFNGs, P(VDF-TrFE) coating on ZnO NFs, output open-circuit voltages of a textile electrostatic NG based on P(VDF-TrFE) coated on ZnO NFs and a textile ZnO NFNG without an insulating layer generated by a sonic wave, NG-based triboelectric effects and PDMS-coated ZnO NF-based NGs grown on an ITO/PET substrate. See DOI: 10.1039/c5nr08324a

Thermal management in MoS{sub 2} based integrated device using near-field radiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Peng, Jiebin; Zhang, Gang, E-mail: zhangg@ihpc.a-star.edu.sg; Li, Baowen

2015-09-28

Recently, wafer-scale growth of monolayer MoS{sub 2} films with spatial homogeneity is realized on SiO{sub 2} substrate. Together with the latest reported high mobility, MoS{sub 2} based integrated electronic devices are expected to be fabricated in the near future. Owing to the low lattice thermal conductivity in monolayer MoS{sub 2}, and the increased transistor density accompanied with the increased power density, heat dissipation will become a crucial issue for these integrated devices. In this letter, using the formalism of fluctuation electrodynamics, we explored the near-field radiative heat transfer from a monolayer MoS{sub 2} to graphene. We demonstrate that in resonance,more » the maximum heat transfer via near-field radiation between MoS{sub 2} and graphene can be ten times higher than the in-plane lattice thermal conduction for MoS{sub 2} sheet. Therefore, an efficient thermal management strategy for MoS{sub 2} integrated device is proposed: Graphene sheet is brought into close proximity, 10–20 nm from MoS{sub 2} device; heat energy transfer from MoS{sub 2} to graphene via near-field radiation; this amount of heat energy then be conducted to contact due to ultra-high lattice thermal conductivity of graphene. Our work sheds light for developing cooling strategy for nano devices constructing with low thermal conductivity materials.« less

Interface trap of p-type gate integrated AlGaN/GaN heterostructure field effect transistors

NASA Astrophysics Data System (ADS)

Kim, Kyu Sang

2017-09-01

In this work, the impact of trap states at the p-(Al)GaN/AlGaN interface has been investigated for the normally-off mode p-(Al)GaN/AlGaN/GaN heterostructure field-effect transistors (HFETs) by means of frequency dependent conductance. From the current-voltage (I-V) measurement, it was found that the p-AlGaN gate integrated device has higher drain current and lower gate leakage current compared to the p-GaN gate integrated device. We obtained the interface trap density and the characteristic time constant for the p-type gate integrated HFETs under the forward gate voltage of up to 6 V. As a result, the interface trap density (characteristic time constant) of the p-GaN gate device was lower (longer) than that of the p-AlGaN. Furthermore, it was analyzed that the trap state energy level of the p-GaN gate device was located at the shallow level relative to the p-AlGaN gate device, which accounts for different gate leakage current of each devices.

History and modern applications of nano-composite materials carrying GA/cm2 current density due to a Bose-Einstein Condensate at room temperature produced by Focused Electron Beam Induced Processing for many extraordinary novel technical applications

NASA Astrophysics Data System (ADS)

Koops, Hans W. P.

2015-12-01

The discovery of Focused Electron Beam Induced Processing and early applications of this technology led to the possible use of a novel nanogranular material “Koops-GranMat®” using Pt/C and Au/C material. which carries at room temperature a current density > 50 times the current density which high TC superconductors can carry. The explanation for the characteristics of this novel material is given. This fact allows producing novel products for many applications using Dual Beam system having a gas supply and X.Y.T stream data programming and not using GDSII layout pattern control software. Novel products are possible for energy transportation. -distribution.-switching, photon-detection above 65 meV energy for very efficient energy harvesting, for bright field emission electron sources used for vacuum electronic devices like amplifiers for HF electronics, micro-tubes, 30 GHz to 6 THz switching amplifiers with signal to noise ratio >10(!), THz power sources up to 1 Watt, in combination with miniaturized vacuum pumps, vacuum gauges, IR to THz detectors, EUV- and X-Ray sources. Since focusing electron beam induced deposition works also at low energy, selfcloning multibeam-production machines for field emitter lamps, displays, multi-beam - lithography, - imaging, and - inspection, energy harvesting, and power distribution with switches controlling field-emitter arrays for KA of currents but with < 100 V switching voltage are possible. Finally the replacement of HTC superconductors and its applications by the Koops-GranMat® having Koops-Pairs at room temperature will allow the investigation devices similar to Josephson Junctions and its applications now called QUIDART (Quantum interference devices at Room Temperature). All these possibilities will support a revolution in the optical, electric, power, and electronic technology.

Multielectron-Transfer-based Rechargeable Energy Storage of Two-Dimensional Coordination Frameworks with Non-Innocent Ligands.

PubMed

Wada, Keisuke; Sakaushi, Ken; Sasaki, Sono; Nishihara, Hiroshi

2018-04-19

The metallically conductive bis(diimino)nickel framework (NiDI), an emerging class of metal-organic framework (MOF) analogues consisting of two-dimensional (2D) coordination networks, was found to have an energy storage principle that uses both cation and anion insertion. This principle gives high energy led by a multielectron transfer reaction: Its specific capacity is one of the highest among MOF-based cathode materials in rechargeable energy storage devices, with stable cycling performance up to 300 cycles. This mechanism was studied by a wide spectrum of electrochemical techniques combined with density-functional calculations. This work shows that a rationally designed material system of conductive 2D coordination networks can be promising electrode materials for many types of energy devices. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

Role of salt concentration in blend polymer for energy storage conversion devices

DOE Office of Scientific and Technical Information (OSTI.GOV)

Arya, Anil; Sharma, A. L., E-mail: alsharmaiitkgp@gmail.com; Sadiq, M.

2016-05-06

Solid Polymer Electrolytes (SPE) are materials of considerable interest worldwide, which serves dual purpose of electrolyte and separator between electrode compartments in renewable energy conversion/storage devices such as; high energy density batteries, electrochromic display devices, and supercapacitors. Polymer blend electrolytes are prepared for various concentration of salt (Ö/Li) with the constant ratio (0.5 gm) of each PEO and PAN polymers (blend polymer) using solution casting technique. Solid polymeric ionic conductor as a separator is the ultimate substitute to eliminate the drawback related to liquid and gel polymer ionic conductors. In the present work, solid polymer electrolyte film consisting of PEO,more » PAN and LiPF{sub 6} are examined for various concentration of lithium salt by keeping PEO/PAN blend ratio as a constant with a view to optimize the dominant salt concentration which could give the maximum conductivity at ambient temperature.« less

Photo-generated carriers lose energy during extraction from polymer-fullerene solar cells

PubMed Central

Melianas, Armantas; Etzold, Fabian; Savenije, Tom J.; Laquai, Frédéric; Inganäs, Olle; Kemerink, Martijn

2015-01-01

In photovoltaic devices, the photo-generated charge carriers are typically assumed to be in thermal equilibrium with the lattice. In conventional materials, this assumption is experimentally justified as carrier thermalization completes before any significant carrier transport has occurred. Here, we demonstrate by unifying time-resolved optical and electrical experiments and Monte Carlo simulations over an exceptionally wide dynamic range that in the case of organic photovoltaic devices, this assumption is invalid. As the photo-generated carriers are transported to the electrodes, a substantial amount of their energy is lost by continuous thermalization in the disorder broadened density of states. Since thermalization occurs downward in energy, carrier motion is boosted by this process, leading to a time-dependent carrier mobility as confirmed by direct experiments. We identify the time and distance scales relevant for carrier extraction and show that the photo-generated carriers are extracted from the operating device before reaching thermal equilibrium. PMID:26537357

Three-Dimensional Hetero-Integration of Faceted GaN on Si Pillars for Efficient Light Energy Conversion Devices.

PubMed

Kim, Dong Rip; Lee, Chi Hwan; Cho, In Sun; Jang, Hanmin; Jeon, Min Soo; Zheng, Xiaolin

2017-07-25

An important pathway for cost-effective light energy conversion devices, such as solar cells and light emitting diodes, is to integrate III-V (e.g., GaN) materials on Si substrates. Such integration first necessitates growth of high crystalline III-V materials on Si, which has been the focus of many studies. However, the integration also requires that the final III-V/Si structure has a high light energy conversion efficiency. To accomplish these twin goals, we use single-crystalline microsized Si pillars as a seed layer to first grow faceted Si structures, which are then used for the heteroepitaxial growth of faceted GaN films. These faceted GaN films on Si have high crystallinity, and their threading dislocation density is similar to that of GaN grown on sapphire. In addition, the final faceted GaN/Si structure has great light absorption and extraction characteristics, leading to improved performance for GaN-on-Si light energy conversion devices.

Power SEMICONDUCTORS—STATE of Art and Future Trends

NASA Astrophysics Data System (ADS)

Benda, Vitezslav

2011-06-01

The importance of effective energy conversion control, including power generation from renewable and environmentally clean energy sources, increases due to rising energy demand. Power electronic systems for controlling and converting electrical energy have become the workhorse of modern society in many applications, both in industry and at home. Power electronics plays a very important role in traction and can be considered as brawns of robotics and automated manufacturing systems. Power semiconductor devices are the key electronic components used in power electronic systems. Advances in power semiconductor technology have improved the efficiency, size, weight and cost of power electronic systems. At present, IGCTs, IGBTs, and MOSFETs represent modern switching devices. Power integrated circuits (PIC) have been developed for the use of power converters for portable, automotive and aerospace applications. For advanced applications, new materials (SiC and GaN) have been introduced. This paper reviews the state of these devices and elaborates on their potentials in terms of higher voltages, higher power density, and better switching performance.

Low-Energy Plasma Focus Device as an Electron Beam Source

PubMed Central

Seong Ling, Yap; Naresh Kumar, Nitturi; Lian Kuang, Lim; Chiow San, Wong

2014-01-01

A low-energy plasma focus device was used as an electron beam source. A technique was developed to simultaneously measure the electron beam intensity and energy. The system was operated in Argon filling at an optimum pressure of 1.7 mbar. A Faraday cup was used together with an array of filtered PIN diodes. The beam-target X-rays were registered through X-ray spectrometry. Copper and lead line radiations were registered upon usage as targets. The maximum electron beam charge and density were estimated to be 0.31 μC and 13.5 × 1016/m3, respectively. The average energy of the electron beam was 500 keV. The high flux of the electron beam can be potentially applicable in material sciences. PMID:25544952

A systematic quality assurance study in bone densitometry devices

NASA Astrophysics Data System (ADS)

Tuncman, Duygu; Kovan, Hatice; Kovan, Bilal; Demir, Bayram; Turkmen, Cuneyt

2015-07-01

Osteoporosis is the most common metabolic bone disease and can result in devastating physical, psychosocial, and economic consequences. It occurs in women after menopause and affects most elderly. Dual-energy x-ray absorptiometry (DXA) is currently the most widely used method for the measurement of areal Bone Mineral Density (BMD) (g/cm2) .DXA is based on the variable absorption of X-ray by the different body components and uses high and low energy X-ray photons. There are two important values in the assessment of the DXA. These values are T-score and Z-score. The T-score is calculated by taking the difference between a patient's measured BMD with the mean BMD of the young normal population, matched for gender and ethnicity, and then by dividing the difference with the standard deviation (SD) of the BMD of the young normal population. T-score and also Z-score are directly depends on the Bone Mineral Density (BMD). BMD measurements should be made periodically in a patient life. But mostly, it is not possible with the same device. Therefore, in this study, for the quality assurance of bone densitometry devices, we evaluated the BMD results measured in the different Bone Densitometry (DXA) devices using a spine phantom.

Electrochemical characterization of nanodimensional metal oxide materials

NASA Astrophysics Data System (ADS)

Tang, Paul Enle

Energy storage devices have become a bottleneck in performance improvements for portable electronics. This research seeks to answer basic science questions that may lead to the necessary improvements. First, this work demonstrates that insertion of multivalent ions into vanadium oxide greatly exceeds the storage capacity of materials presently used. Second, this work demonstrates that potassium ferrate exhibits a uniquely large pseudocapacitive effect. This effect can be used to great advantage when high power density and high energy density are required. Lastly, this work proposes a model of pseudocapacitance that has a greater descriptive power than that of previous models.

High performance asymmetric supercapacitor based on polypyrrole/graphene composite and its derived nitrogen-doped carbon nano-sheets

NASA Astrophysics Data System (ADS)

Zhu, Jianbo; Feng, Tianyu; Du, Xianfeng; Wang, Jingping; Hu, Jun; Wei, LiPing

2017-04-01

Neutral aqueous medium is a promising electrolyte for supercapacitors because it is low-cost, environmental-friendly and can achieve rapid charging/discharging with high power density. However, the energy density of such supercapacitor is significantly limited by its narrow operational voltage window. Herein, we demonstrated an effective approach to broaden the operational voltage window by fabricating an asymmetric supercapacitor (ASC) with polypyrrole/reduced graphene oxide (PPy/rGO) composite and its derived Nitrogen-doped carbon nano-sheets (NCs) as positive and negative electrode material, respectively. The homogeneous nano-sheet and mesoporous structure of PPy/rGO and NCs can facilitate rapid charge/ion migration and provide more active sites for ions adsorption/exchange to improve their electrochemical performance. Benefiting from high capacitance and good rate performance of PPy/rGO and NCs electrodes, the as-fabricated ASCs devices in a polyvinyl alcohol/LiCl gel electrolyte can realize a wide operational voltage of 1.6 V and deliver high energy density of 15.8 wh kg-1 (1.01 mWh cm-3) at 0.14 kW kg-1 (19.3 mW cm-3), which still remains 9.5 wh kg-1as power density increases to 6.56 kW kg-1, as well as excellent long-term cycling stability with about 88.7% capacitance retention after 10000 cycles. The remarkable performances suggest that the ASCs devices are promising for future energy storage applications.

Improving energy conversion efficiency for triboelectric nanogenerator with capacitor structure by maximizing surface charge density.

PubMed

He, Xianming; Guo, Hengyu; Yue, Xule; Gao, Jun; Xi, Yi; Hu, Chenguo

2015-02-07

Nanogenerators with capacitor structures based on piezoelectricity, pyroelectricity, triboelectricity and electrostatic induction have been extensively investigated. Although the electron flow on electrodes is well understood, the maximum efficiency-dependent structure design is not clearly known. In this paper, a clear understanding of triboelectric generators with capacitor structures is presented by the investigation of polydimethylsiloxane-based composite film nanogenerators, indicating that the generator, in fact, acts as both an energy storage and output device. Maximum energy storage and output depend on the maximum charge density on the dielectric polymer surface, which is determined by the capacitance of the device. The effective thickness of polydimethylsiloxane can be greatly reduced by mixing a suitable amount of conductive nanoparticles into the polymer, through which the charge density on the polymer surface can be greatly increased. This finding can be applied to all the triboelectric nanogenerators with capacitor structures, and it provides an important guide to the structural design for nanogenerators. It is demonstrated that graphite particles with sizes of 20-40 nm and 3.0% mass mixed into the polydimethylsiloxane can reduce 34.68% of the effective thickness of the dielectric film and increase the surface charges by 111.27% on the dielectric film. The output power density of the triboelectric nanogenerator with the composite polydimethylsiloxane film is 3.7 W m(-2), which is 2.6 times as much as that of the pure polydimethylsiloxane film.

Enhanced energy harvesting by concentration gradient-driven ion transport in SBA-15 mesoporous silica thin films.

PubMed

Hwang, Junho; Kataoka, Sho; Endo, Akira; Daiguji, Hirofumi

2016-09-21

Nanofluidic energy harvesting systems have attracted interest in the field of battery application, particularly for miniaturized electrical devices, because they possess excellent energy conversion capability for their size. In this study, a mesoporous silica (MPS)-based nanofluidic energy harvesting system was fabricated and selective ion transport in mesopores as a function of the salt gradient was investigated. Aqueous solutions with three different kinds of monovalent electrolytes-KCl, NaCl, and LiCl-with different diffusion coefficients (D + ) were considered. The highest power density was 3.90 W m -2 for KCl, followed by 2.39 W m -2 for NaCl and 1.29 W m -2 for LiCl. Furthermore, the dependency of power density on the type of cation employed indicates that the harvested energy increases as the cation mobility increases, particularly at high concentrations. This cation-specific dependency suggests that the maximum power density increases by increasing the diffusion coefficient ratio of cations to anions, making this ratio a critical parameter in enhancing the performance of nanofluidic energy harvesting systems with extremely small pores ranging from 2 to 3 nm.

Plasma wake field XUV radiation source

DOEpatents

Prono, Daniel S.; Jones, Michael E.

1997-01-01

A XUV radiation source uses an interaction of electron beam pulses with a gas to create a plasma radiator. A flowing gas system (10) defines a circulation loop (12) with a device (14), such as a high pressure pump or the like, for circulating the gas. A nozzle or jet (16) produces a sonic atmospheric pressure flow and increases the density of the gas for interacting with an electron beam. An electron beam is formed by a conventional radio frequency (rf) accelerator (26) and electron pulses are conventionally formed by a beam buncher (28). The rf energy is thus converted to electron beam energy, the beam energy is used to create and then thermalize an atmospheric density flowing gas to a fully ionized plasma by interaction of beam pulses with the plasma wake field, and the energetic plasma then loses energy by line radiation at XUV wavelengths Collection and focusing optics (18) are used to collect XUV radiation emitted as line radiation when the high energy density plasma loses energy that was transferred from the electron beam pulses to the plasma.

Aqueous Rechargeable Alkaline CoxNi2-xS2/TiO2 Battery.

PubMed

Liu, Jilei; Wang, Jin; Ku, Zhiliang; Wang, Huanhuan; Chen, Shi; Zhang, Lili; Lin, Jianyi; Shen, Ze Xiang

2016-01-26

An electrochemical energy storage system with high energy density, stringent safety, and reliability is highly desirable for next-generation energy storage devices. Here an aqueous rechargeable alkaline CoxNi2-xS2 // TiO2 battery system is designed by integrating two reversible electrode processes associated with OH(-) insertion/extraction in the cathode part and Li ion insertion/extraction in the anode part, respectively. The prototype CoxNi2-xS2 // TiO2 battery is able to deliver high energy/power densities of 83.7 Wh/kg at 609 W/kg (based on the total mass of active materials) and good cycling stabilities (capacity retention 75.2% after 1000 charge/discharge cycles). A maximum volumetric energy density of 21 Wh/l (based on the whole packaged cell) has been achieved, which is comparable to that of a thin-film battery and better than that of typical commercial supercapacitors, benefiting from the unique battery and hierarchical electrode design. This hybrid system would enrich the existing aqueous rechargeable LIB chemistry and be a promising battery technology for large-scale energy storage.

Dependence of Mobility on Density of Gap States in Organics by GAMEaS - Gate Modulated Activation Energy Spectroscopy

NASA Astrophysics Data System (ADS)

So, Woo-Young; Lang, David; Ramirez, Arthur

2008-03-01

We develop a spectroscopic method for determining the density of states (DOS) in the energy gap - GAte Modulated activation Energy Spectroscopy (GAMEaS), We also report the relationship of these gap states to the mobility of organic field-effect-transistors (FETs). We find that the field-effect mobility is parameterized by two factors: (1) the free-carrier mobility and (2) the ratio of the free carrier density to the total carrier density induced by the gate bias. We show that the highest mobility FETs have shallow exponential band tails of localized states with characteristic slope of 1/kT at 300K. Most remarkably, state-of-the-art crystalline FETs fabricated from rubrene, pentacene, and tetracene all have a very high free-carrier mobility, up to 200cm2/Vsec at 300K, with the somewhat lower effective mobilities dominated by localized gap states. This strongly suggests that further improvements in device performance could be possible with enhanced material quality.

Porous Ni-Co-Mn oxides prisms for high performance electrochemical energy storage

NASA Astrophysics Data System (ADS)

Zhao, Jianbo; Li, Man; Li, Junru; Wei, Chengzhen; He, Yuyue; Huang, Yixuan; Li, Qiaoling

2017-12-01

Porous Ni-Co-Mn oxides prisms have been successfully synthesized via a facile route. The process involves the preparation of nickel-cobalt-manganese acetate hydroxide by a simple co-precipitation method and subsequently the thermal treatment. The as-synthesized Ni-Co-Mn oxides prisms had a large surface area (96.53 m2 g-1) and porous structure. As electrode materials for supercapacitors, porous Ni-Co-Mn oxides prisms showed a high specific capacitance of 1623.5 F g-1 at 1.0 A g-1. Moreover, the porous Ni-Co-Mn oxides prisms were also employed as positive electrode materials to assemble flexible solid-state asymmetric supercapacitors. The resulting flexible device had a maximum volumetric energy density (0.885 mW h cm-3) and power density (48.9 mW cm-3). Encouragingly, the flexible device exhibited good cycling stability with only about 2.2% loss after 5000 charge-discharge cycles and excellent mechanical stability. These results indicate that porous Ni-Co-Mn oxides prisms have the promising application in high performance electrochemical energy storage.

Polaron Stabilization by Cooperative Lattice Distortion and Cation Rotations in Hybrid Perovskite Materials

DOE PAGES

Neukirch, Amanda J.; Nie, Wanyi; Blancon, Jean-Christophe; ...

2016-05-25

Solution-processed organometallic perovskites have rapidly developed into a top candidate for the active layer of photovoltaic devices. In spite of the remarkable progress associated with perovskite materials, many questions about the fundamental photophysical processes taking place in these devices, remain open. High on the list of unexplained phenomena are very modest mobilities despite low charge carrier effective masses. Moreover, experiments elucidate unique degradation of photocurrent affecting stable operation of perovskite solar cells. These puzzles suggest that, while ionic hybrid perovskite devices may have efficiencies on par with conventional Si and GaAs devices, they exhibit more complicated charge transport phenomena. Wemore » report the results from an in-depth computational study of small polaron formation, electronic structure, charge density, and reorganization energies using both periodic boundary conditions and isolated structures. Using the hybrid density functional theory, we found that volumetric strain in a CsPbI 3 cluster creates a polaron with binding energy of around 300 and 900 meV for holes and electrons, respectively. In the MAPbI 3 (MA = CH 3NH 3) cluster, both volumetric strain and MA reorientation effects lead to larger binding energies at around 600 and 1300 meV for holes and electrons, respectively. Such large reorganization energies suggest appearance of small polarons in organometallic perovskite materials. Furthermore, the fact that both volumetric lattice strain and MA molecular rotational degrees of freedom can cooperate to create and stabilize polarons indicates that in order to mitigate this problem, formamidinium (FA = HC(NH 2) 2) and cesium (Cs) based crystals and alloys, are potentially better materials for solar cell and other optoelectronic applications.« less

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices.

PubMed

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J; Grant, Patrick S

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

The role of nanomaterials in redox-based supercapacitors for next generation energy storage devices

NASA Astrophysics Data System (ADS)

Zhao, Xin; Sánchez, Beatriz Mendoza; Dobson, Peter J.; Grant, Patrick S.

2011-03-01

The development of more efficient electrical storage is a pressing requirement to meet future societal and environmental needs. This demand for more sustainable, efficient energy storage has provoked a renewed scientific and commercial interest in advanced capacitor designs in which the suite of experimental techniques and ideas that comprise nanotechnology are playing a critical role. Capacitors can be charged and discharged quickly and are one of the primary building blocks of many types of electrical circuit, from microprocessors to large-sale power supplies, but usually have relatively low energy storage capability when compared with batteries. The application of nanostructured materials with bespoke morphologies and properties to electrochemical supercapacitors is being intensively studied in order to provide enhanced energy density without comprising their inherent high power density and excellent cyclability. In particular, electrode materials that exploit physical adsorption or redox reactions of electrolyte ions are foreseen to bridge the performance disparity between batteries with high energy density and capacitors with high power density. In this review, we present some of the novel nanomaterial systems applied for electrochemical supercapacitors and show how material morphology, chemistry and physical properties are being tailored to provide enhanced electrochemical supercapacitor performance.

Design, fabrication and calibration of alpha particle densitometers for measuring planetary atmospheric density

NASA Technical Reports Server (NTRS)

Sellers, B.; Hunerwadel, J. L.; Hanser, F. A.

1972-01-01

An alpha particle densitometer was developed for possible application to measurement of the atmospheric density-altitude profile on Martian entry. The device uses an Am-241 radioactive-foil source, which emits a distributed energy spectrum, located about 25 to 75 cm from a semiconductor detector. System response - defined as the number of alphas per second reaching the detector with energy above a fixed threshold - is given for Ar and CO2. The altitude profile of density measurement accuracy is given for a pure CO2 atmosphere with 5 mb surface pressure. The entire unit, including dc-dc converters, requires less than 350 milliwatts of power from +28 volts, weighs about 0.85 lb and occupies less than 15 cubic inches volume.

Wearable Solid-State Supercapacitors Operating at High Working Voltage with a Flexible Nanocomposite Electrode.

PubMed

Li, Xiaoyan; Wang, Jun; Zhao, Yaping; Ge, Fengyan; Komarneni, Sridhar; Cai, Zaisheng

2016-10-05

The proposed approach for fabricating ultralight self-sustained electrodes facilitates the structural integration of highly flexible carbon nanofibers, amino-modified multiwalled carbon nanotubes (AM-MWNT), and MnO 2 nanoflakes for potential use in wearable supercapacitors. Because of the higher orientation of AM-MWNT and the sublimation of terephthalic acid (PTA) in the carbonization process, freestanding electrodes could be realized with high porosity and flexibility and could possess remarkable electrochemical properties without using polymer substrates. Wearable symmetric solid-state supercapacitors were further assembled using a LiCl/PVA gel electrolyte, which exhibit a maximum energy density of 44.57 Wh/kg (at a power density of 337.1 W/kg) and a power density of 13330 W/kg (at an energy density of 19.64 Wh/kg) with a working voltage as high as 1.8 V. Due to the combination of several favorable traits such as flexibility, high energy density, and excellent electrochemical cyclability, the presently developed wearable supercapacitors with wide potential windows are expected to be useful for new kinds of portable electric devices.

A high-performance supercapacitor electrode based on N-doped porous graphene

NASA Astrophysics Data System (ADS)

Dai, Shuge; Liu, Zhen; Zhao, Bote; Zeng, Jianhuang; Hu, Hao; Zhang, Qiaobao; Chen, Dongchang; Qu, Chong; Dang, Dai; Liu, Meilin

2018-05-01

The development of high-performance supercapacitors (SCs) often faces some contradictory and competing requirements such as excellent rate capability, long cycling life, and high energy density. One effective strategy is to explore electrode materials of high capacitance, electrode architectures of fast charge and mass transfer, and electrolytes of wide voltage window. Here we report a facile and readily scalable strategy to produce high-performance N-doped graphene with a high specific capacitance (∼390 F g-1). A symmetric SC device with a wide voltage window of 3.5 V is also successfully fabricated based on the N-doped graphene electrode. More importantly, the as-assembled symmetric SC delivers a high energy density of 55 Wh kg-1 at a power density of 1800 W kg-1 while maintaining superior cycling life (retaining 96.6% of the initial capacitance after 20,000 cycles). Even at a power density as high as 8800 W kg-1, it still retains an energy density of 29 Wh kg-1, higher than those of previously reported graphene-based symmetric SCs.

Hierarchical MoS2 nanowires/NiCo2O4 nanosheets supported on Ni foam for high-performance asymmetric supercapacitors

NASA Astrophysics Data System (ADS)

Wen, Shiyang; Liu, Yu; Zhu, Fangfang; Shao, Rong; Xu, Wei

2018-01-01

The hierarchical MoS2 nanowires/NiCo2O4 nanosheets (MS/NCO) supercapacitor electrode materials supported on Ni foam were synthesized by a two-step hydrothermal method. The capacitance was investigated by using various electrochemical methods including cyclic voltammetry, constant-current galvanostatic charge/discharge curves and electrochemical impedance spectroscopy. The MS/NCO networks show 7 times more capacitance (7.1 F cm-2) than pure NiCo2O4 nanosheets by CV at a scan rate of 2 mV s-1. The specific capacitance of the assembled MS/NCO//active carbon (AC) asymmetric supercapacitor could reach up to 51.7 F g-1 at a current density of 1.5 A g-1. Also, the maximum energy density of 18.4 W h kg-1 at a power density of 1200.2 W kg-1 was achieved, with 98.2% specific capacitance retention after 8000 cycles. These exciting results exhibit potential application in developing energy storage devices with high energy density and high power density.

A flexible electrostatic kinetic energy harvester based on electret films of electrospun nanofibers

NASA Astrophysics Data System (ADS)

Lu, Y.; Capo-Chichi, M.; Leprince-Wang, Y.; Basset, P.

2018-01-01

This paper reports a paper-based electrostatic kinetic energy harvester (e-KEH) implementing multilayered electret films based on electrospun nanofibrous material. It is the first time that a fully flexible electret-based e-KEH is reported. The proposed electret, PVDF-PTFD nanofibrous covered by Parylene C, has a faster stabilization of surface potential than a planar thin film of Parylene C, and a higher stability of charge storage. With a maximum force of 0.5 N and a 3-layer electret, the device capacitance increases from 25 to 100 pF during a pressing operation. Working with the optimal resistive load of 16 MΩ, the device pressed manually delivers a peak instantaneous power up to 45.6 μW and an average energy of 54 nJ/stroke, corresponding to a peak instantaneous power density of 7.3 μW cm-2 and an average energy density of 8.6 nJ cm-2/stroke. Within 450 manual strokes, a 10 nF capacitor is charged up to 8.5 V by the prototype through a full-wave diode bridge. On a 1 μF capacitor, the energy delivery of 9.9 nJ/stroke has been obtained with a 10 Hz pressing movement excited by a vibrator with a maximum force of 0.5 N.

A low-power reversible alkali atom source

NASA Astrophysics Data System (ADS)

Kang, Songbai; Mott, Russell P.; Gilmore, Kevin A.; Sorenson, Logan D.; Rakher, Matthew T.; Donley, Elizabeth A.; Kitching, John; Roper, Christopher S.

2017-06-01

An electrically controllable, solid-state, reversible device for sourcing and sinking alkali vapor is presented. When placed inside an alkali vapor cell, both an increase and decrease in the rubidium vapor density by a factor of two are demonstrated through laser absorption spectroscopy on 10-15 s time scales. The device requires low voltage (5 V), low power (<3.4 mW peak power), and low energy (<10.7 mJ per 10 s pulse). The absence of oxygen emission during operation is shown through residual gas analysis, indicating that Rb is not lost through chemical reaction but rather by ion transport through the designed channel. This device is of interest for atomic physics experiments and, in particular, for portable cold-atom systems where dynamic control of alkali vapor density can enable advances in science and technology.

Exact Thermal Transport Properties of Gray-Arsenic using Electon-Phonon Coupling

NASA Astrophysics Data System (ADS)

Kang, Seoung-Hun; Kwon, Young-Kyun

Using various theoretical methods, we investigate the thermoelectric property of gray arsenic. Thermoelectric devices that utilize the Seebeck effect convert heat flow into electrical energy. The conversion efficiency of such a device is determined by its figure of merit or ZT value, which is related to various transport coefficients, such as Seebeck coefficient and the ratio of its electrical conductivity to its thermal counterpart for given temperature. To calculate various transport coefficients and thus the ZT values of gray arsenic, we apply the Boltzmann transport theory to its electronic and phononic structures obtained by density functional theory and density functional perturbation theory together with maximally locallized Wannier functions. During this procedure, we evaluate its relaxation time accurately by explicitly considering electron-phonon coupling. Our result reveals that gray arsenic may be used for a good p-type thermoelectric devices.

Quasi-Isentropic Compressibility of Deuterium at a Pressure of 12 TPa

NASA Astrophysics Data System (ADS)

Mochalov, M. A.; Il'kaev, R. I.; Fortov, V. E.; Mikhailov, A. L.; Arinin, V. A.; Blikov, A. O.; Komrakov, V. A.; Maksimkin, I. P.; Ogorodnikov, V. A.; Ryzhkov, A. V.

2018-04-01

An experimental result for the quasi-isentropic compressibility of a strongly nonideal deuterium plasma compressed in a spherical device by the pressure P = 11400 GPa (114 Mbar) to the density ρ ≈ 10g/cm3 has been reported. The characteristics of the experimental device, diagnostic methods, and experimental results have been described. The trajectory of motion of metallic shells compressing a deuterium plasma has been recorded using intense pulsed sources of X rays with the boundary energy of electrons up to 60 MeV. The deuterium plasma density ρ ≈ 10g/cm3 has been determined from the measured radius of the shell at the time of its "stop." The pressure of the compressed plasma has been determined from gas-dynamic calculations taking into account the real characteristics of the experimental device.

Photoresponsive Smart Coloration Electrochromic Supercapacitor.

PubMed

Yun, Tae Gwang; Kim, Donghyuk; Kim, Yong Ho; Park, Minkyu; Hyun, Seungmin; Han, Seung Min

2017-08-01

Electrochromic devices have been widely adopted in energy saving applications by taking advantage of the electrode coloration, but it is critical to develop a new electrochromic device that can undergo smart coloration and can have a wide spectrum in transmittance in response to input light intensity while also functioning as a rechargeable energy storage system. In this study, a photoresponsive electrochromic supercapacitor based on cellulose-nanofiber/Ag-nanowire/reduced-graphene-oxide/WO 3 -composite electrode that is capable of undergoing "smart" reversible coloration while simultaneously functioning as a reliable energy-storage device is developed. The fabricated device exhibits a high coloration efficiency of 64.8 cm 2 C -1 and electrochemical performance with specific capacitance of 406.0 F g -1 , energy/power densities of 40.6-47.8 Wh kg -1 and 6.8-16.9 kW kg -1 . The electrochromic supercapacitor exhibits excellent cycle reliability, where 75.0% and 94.1% of its coloration efficiency and electrochemical performance is retained, respectively, beyond 10 000 charge-discharge cycles. Cyclic fatigue tests show that the developed device is mechanically durable and suitable for wearable electronics applications. The smart electrochromic supercapacitor system is then integrated with a solar sensor to enable photoresponsive coloration where the transmittance changes in response to varying light intensity. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

A reconfigurable waveguide for energy-efficient transmission and local manipulation of information in a nanomagnetic device

NASA Astrophysics Data System (ADS)

Haldar, Arabinda; Kumar, Dheeraj; Adeyeye, Adekunle Olusola

2016-05-01

Spin-wave-based devices promise to usher in an era of low-power computing where information is carried by the precession of the electrons' spin instead of dissipative translation of their charge. This potential is, however, undermined by the need for a bias magnetic field, which must remain powered on to maintain an anisotropic device characteristic. Here, we propose a reconfigurable waveguide design that can transmit and locally manipulate spin waves without the need for any external bias field once initialized. We experimentally demonstrate the transmission of spin waves in straight as well as curved waveguides without a bias field, which has been elusive so far. Furthermore, we experimentally show a binary gating of the spin-wave signal by controlled switching of the magnetization, locally, in the waveguide. The results have potential implications in high-density integration and energy-efficient operation of nanomagnetic devices at room temperature.

Rapid laser fabrication of microlens array using colorless liquid photopolymer for AMOLED devices

NASA Astrophysics Data System (ADS)

Kim, Kwang-Ryul; Jeong, Han-Wook; Lee, Kong-Soo; Yi, Junsin; Yoo, Jae-Chern; Cho, Myung-Woo; Cho, Sung-Hak; Choi, Byoungdeog

2011-01-01

Microlens array (MLA) is microfabricated using Ultra Violet (UV) laser for display device applications. A colorless liquid photopolymer, Norland Optical Adhesive (NOA) 60, is spin-coated and pre-cured via UV light for completing the laser process. The laser energy controlled by a galvano scanner is radiated on the surface of the NOA 60. A rapid thermal volume expansion inside the material creates microlens array when the Gaussian laser energy is absorbed. The fabrication process conditions for various shapes and densities of MLA using a non-contact surface profiler are investigated. Furthermore, we analyze the optical and display characteristics for the Organic Light Emitting Diode (OLED) devices. Optimized condition furnishes the OLED with the enhancement of light emission by 15%. We show that UV laser technique, which is installed with NOA 60 MLA layer, is eligible for improving the performance of the next generation display devices.

InGaAs/InP Monolithic Interconnected Modules (MIM) for Thermophotovoltaic Applications

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Scheiman, David A.; Murray, Christopher S.; Riley, David R.

2004-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between systems efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) devices series -connected on a single semi-insulating indium phosphide (InP) substrate. The MIMs are exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight series interconnected cells. MIM devices, produced from 0,74 eV InGAAs, have demonstrated V(sub infinity) = 3.23 volts, J(sub sc) = 70 mA/sq cm and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurement (less than 2 microns) of these devices indicate a reflectivity of less than 82%. MIM devices produced from 0.55 eV InGaAs have also been den=monstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM1) have been demonstrated.

Few layered MoO3 nano sheets-SWCNT composite thin film as supercapacitor electrode

NASA Astrophysics Data System (ADS)

Dutta, Shibsankar; Akther, Jasim; De, Sukanta

2017-05-01

The increasing demands for clean and renewable energy, the advantages of high power density, long lasting and high efficiency have made Supercapacitor as one of the major emerging energy storage device.The 2D layered metal oxide nanocomposite with SWCNT is the promising candidate for energy storage and conversion. In this work we exfoliate the crystalline bulk MoO3 by simple liquid phase exfoliation to give multi-layer MoO3 dispersed in a suitable solvent. As the electrical conductivity of MoO3 is very low so, the dispersion was used to make hybrid material with SWCNT dispersion by vacuum filtration. The SWCNT-MoO3 composite showed an areal capacitance value of 1290 µF/cm2 at 10 mV/s in PVA-H2 SO4 solid gel electrolyte. This composite based electrode provides an energy density of 0.092 µWh/cm2 and a power density of 9.54 µW/cm2 at 0.01 mA/cm2

One-step electroplating porous graphene oxide electrodes of supercapacitors for ultrahigh capacitance and energy density.

PubMed

Wang, Yongjie; Zhu, Jiaqi

2015-02-06

An electroplating method was used for the first time to synthesize 3D porous graphene oxide (PGO) architectures, exhibiting ultrahigh capacitance and energy density as electrodes of supercapacitors. Scanning electron microscopy illustrated the porous structures which promoted the stability and alleviated the stacking of the graphene oxide layers. As investigated in a three-electrode supercapacitor cell, PGO electrodes exhibited the maximum capacitance and energy of 973 F · g(-1) and 98.4 Wh · Kg(-1), which are better than current reports and comparable to batteries. At 4 A · g(-1) for high-power applications, PGO electrodes reached a capacitance, energy, and power density of 493 F · g(-1), 49.9 Wh · Kg(-1), and 1700 W · Kg(-1), and they retained ∼97.83% of capacitance after 10 000 charge/discharge processes. Furthermore, when the PGO was bent exaggeratedly, it still displayed identical properties, which is of important significance for supporting wearable devices.

High-energy asymmetric supercapacitors based on free-standing hierarchical Co-Mo-S nanosheets with enhanced cycling stability.

PubMed

Balamurugan, Jayaraman; Li, Chao; Peera, Shaik Gouse; Kim, Nam Hoon; Lee, Joong Hee

2017-09-21

Layered transition metal sulfides (TMS) are emerging as advanced materials for energy storage and conversion applications. In this work, we report a facile and cost-effective anion exchange technique to fabricate a layered, multifaceted, free standing, ultra-thin ternary cobalt molybdenum sulfide nanosheet (Co-Mo-S NS) architecture grown on a 3D porous Ni foam substrate. The unique Co-Mo layered double hydroxides are first synthesized as precursors and consequently transformed into ultra-thin Co-Mo-S NS. When employed as an electrode for supercapacitors, the Co-Mo-S NS delivered an ultra-high specific capacitance of 2343 F g -1 at a current density of 1 mA cm -2 with tremendous rate capability and extraordinary cycling performance (96.6% capacitance retention after 20 000 cycles). Furthermore, assembled Co-Mo-S/nitrogen doped graphene nanosheets (NGNS) in an asymmetric supercapacitor (ASC) device delivered an excellent energy density of 89.6 Wh kg -1 , an amazing power density of 20.07 kW kg -1 , and superior cycling performance (86.8% capacitance retention after 50 000 cycles). Such exceptional electrochemical performance of Co-Mo-S NS is ascribed to the good electrical contact with the 3D Ni foam, ultra-high contact area with the electrolyte, and enhanced architectural softening during the charging/discharging process. It is expected that the fabricated, unique, ultra-thin Co-Mo-S NS have great potential for future energy storage devices.

Research Tool to Evaluate the Safety Response of Lithium Batteries to an Internal Short Circuit

DOE Office of Scientific and Technical Information (OSTI.GOV)

Keyser, Matthew; Darcy, Eric; Pesaran, Ahmad

Li-ion cells provide the highest specific energy and energy density rechargeable battery with the longest life. Many safety incidents that take place in the field originate due to an internal short that was not detectable or predictable at the point of manufacture. NREL's internal short circuit (ISC) device is capable of simulating shorts and produces consistent and reproducible results. The cell behaves normally until the ISC device is activated wherein a latent defect (i.e., built into the cell during manufacturing) gradually moves into position to create an internal short while the battery is in use, providing relevant data to verifymore » abuse models. The ISC device is an effective tool for studying the safety features of parts of Li-ion batteries.« less

Additive Manufacturing of a Microbial Fuel Cell—A detailed study

PubMed Central

Calignano, Flaviana; Tommasi, Tonia; Manfredi, Diego; Chiolerio, Alessandro

2015-01-01

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m−3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments. PMID:26611142

Energy correlations of photon pairs generated by a silicon microring resonator probed by Stimulated Four Wave Mixing.

PubMed

Grassani, Davide; Simbula, Angelica; Pirotta, Stefano; Galli, Matteo; Menotti, Matteo; Harris, Nicholas C; Baehr-Jones, Tom; Hochberg, Michael; Galland, Christophe; Liscidini, Marco; Bajoni, Daniele

2016-04-01

Compact silicon integrated devices, such as micro-ring resonators, have recently been demonstrated as efficient sources of quantum correlated photon pairs. The mass production of integrated devices demands the implementation of fast and reliable techniques to monitor the device performances. In the case of time-energy correlations, this is particularly challenging, as it requires high spectral resolution that is not currently achievable in coincidence measurements. Here we reconstruct the joint spectral density of photons pairs generated by spontaneous four-wave mixing in a silicon ring resonator by studying the corresponding stimulated process, namely stimulated four wave mixing. We show that this approach, featuring high spectral resolution and short measurement times, allows one to discriminate between nearly-uncorrelated and highly-correlated photon pairs.

Additive Manufacturing of a Microbial Fuel Cell—A detailed study

NASA Astrophysics Data System (ADS)

Calignano, Flaviana; Tommasi, Tonia; Manfredi, Diego; Chiolerio, Alessandro

2015-11-01

In contemporary society we observe an everlasting permeation of electron devices, smartphones, portable computing tools. The tiniest living organisms on Earth could become the key to address this challenge: energy generation by bacterial processes from renewable stocks/waste through devices such as microbial fuel cells (MFCs). However, the application of this solution was limited by a moderately low efficiency. We explored the limits, if any, of additive manufacturing (AM) technology to fabricate a fully AM-based powering device, exploiting low density, open porosities able to host the microbes, systems easy to fuel continuously and to run safely. We obtained an optimal energy recovery close to 3 kWh m-3 per day that can power sensors and low-power appliances, allowing data processing and transmission from remote/harsh environments.

Design and analysis of a MEMS-based bifurcate-shape piezoelectric energy harvester

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Yuan; Gan, Ruyi, E-mail: 2471390146@qq.com; Wan, Shalang

This paper presents a novel piezoelectric energy harvester, which is a MEMS-based device. This piezoelectric energy harvester uses a bifurcate-shape. The derivation of the mathematical modeling is based on the Euler-Bernoulli beam theory, and the main mechanical and electrical parameters of this energy harvester are analyzed and simulated. The experiment result shows that the maximum output voltage can achieve 3.3 V under an acceleration of 1 g at 292.11 Hz of frequency, and the output power can be up to 0.155 mW under the load of 0.4 MΩ. The power density is calculated as 496.79 μWmm{sup −3}. Besides that, itmore » is demonstrated efficiently at output power and voltage and adaptively in practical vibration circumstance. This energy harvester could be used for low-power electronic devices.« less

Boosting the Recoverable Energy Density of Lead-Free Ferroelectric Ceramic Thick Films through Artificially Induced Quasi-Relaxor Behavior.

PubMed

Peddigari, Mahesh; Palneedi, Haribabu; Hwang, Geon-Tae; Lim, Kyung Won; Kim, Ga-Yeon; Jeong, Dae-Yong; Ryu, Jungho

2018-06-20

Dielectric ceramic film capacitors, which store energy in the form of electric polarization, are promising for miniature pulsed power electronic device applications. For a superior energy storage performance of the capacitors, large recoverable energy density, along with high efficiency, high power density, fast charge/discharge rate, and good thermal/fatigue stability, is desired. Herein, we present highly dense lead-free 0.942[Na 0.535 K 0.480 NbO 3 ]-0.058LiNbO 3 (KNNLN) ferroelectric ceramic thick films (∼5 μm) demonstrating remarkable energy storage performance. The nanocrystalline KNNLN thick film fabricated by aerosol deposition (AD) process and annealed at 600 °C displayed a quasi-relaxor ferroelectric behavior, which is in contrast to the typical ferroelectric nature of the KNNLN ceramic in its bulk form. The AD film exhibited a large recoverable energy density of 23.4 J/cm 3 , with an efficiency of over 70% under the electric field of 1400 kV/cm. Besides, an ultrahigh power density of 38.8 MW/cm 3 together with a fast discharge speed of 0.45 μs, good fatigue endurance (up to 10 6 cycles), and thermal stability in a wide temperature range of 20-160 °C was also observed. Using the AD process, we could make a highly dense microstructure of the film containing nano-sized grains, which gave rise to the quasi-relaxor ferroelectric characteristics and the remarkable energy storage properties.

Bio-Nanobattery Development and Characterization

NASA Technical Reports Server (NTRS)

King, Glen C.; Choi, Sang H.; Chu, Sang-Hyon; Kim, Jae-Woo; Watt, Gerald D.; Lillehei, Peter T.; Park, Yeonjoon; Elliott, James R.

2005-01-01

A bio-nanobattery is an electrical energy storage device that utilizes organic materials and processes on an atomic, or nanometer-scale. The bio-nanobattery under development at NASA s Langley Research Center provides new capabilities for electrical power generation, storage, and distribution as compared to conventional power storage systems. Most currently available electronic systems and devices rely on a single, centralized power source to supply electrical power to a specified location in the circuit. As electronic devices and associated components continue to shrink in size towards the nanometer-scale, a single centralized power source becomes impractical. Small systems, such as these, will require distributed power elements to reduce Joule heating, to minimize wiring quantities, and to allow autonomous operation of the various functions performed by the circuit. Our research involves the development and characterization of a bio-nanobattery using ferritins reconstituted with both an iron core (Fe-ferritin) and a cobalt core (Co-ferritin). Synthesis and characterization of the Co-ferritin and Fe-ferritin electrodes were performed, including reducing capability and the half-cell electrical potentials. Electrical output of nearly 0.5 V for the battery cell was measured. Ferritin utilizing other metallic cores were also considered to increase the overall electrical output. Two dimensional ferritin arrays were produced on various substrates to demonstrate the feasibility of a thin-film nano-scaled power storage system for distributed power storage applications. The bio-nanobattery will be ideal for nanometerscaled electronic applications, due to the small size, high energy density, and flexible thin-film structure. A five-cell demonstration article was produced for concept verification and bio-nanobattery characterization. Challenges to be addressed include the development of a multi-layered thin-film, increasing the energy density, dry-cell bionanobattery development, and selection of ferritin core materials to allow the broadest range of applications. The potential applications for the distributed power system include autonomously-operating intelligent chips, flexible thin-film electronic circuits, nanoelectromechanical systems (NEMS), ultra-high density data storage devices, nanoelectromagnetics, quantum electronic devices, biochips, nanorobots for medical applications and mechanical nano-fabrication, etc.

Universal Open Power, Communications, and Control for Assistive Devices

DTIC Science & Technology

2017-10-01

The views, opinions and/or findings contained in this report are those of the author(s) and should not be construed as an official Department of the...SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION / AVAILABILITY STATEMENT Approved for Public Release; Distribution Unlimited 13. SUPPLEMENTARY NOTES...flexible energy configuration, advanced high bandwidth sensing, and high energy density actuation technology. This project will advance the state-of

Structures and electronic states of halogen-terminated graphene nano-flakes

NASA Astrophysics Data System (ADS)

Tachikawa, Hiroto; Iyama, Tetsuji

2015-12-01

Halogen-functionalized graphenes are utilized as electronic devices and energy materials. In the present paper, the effects of halogen-termination of graphene edge on the structures and electronic states of graphene flakes have been investigated by means of density functional theory (DFT) method. It was found that the ionization potential (Ip) and electron affinity of graphene (EA) are blue-shifted by the halogen termination, while the excitation energy is red-shifted. The drastic change showed a possibility as electronic devices such as field-effect transistors. The change of electronic states caused by the halogen termination of graphene edge was discussed on the basis of the theoretical results.

Batteries used to Power Implantable Biomedical Devices

PubMed Central

Bock, David C.; Marschilok, Amy C.; Takeuchi, Kenneth J.; Takeuchi, Esther S.

2012-01-01

Battery systems have been developed that provide years of service for implantable medical devices. The primary systems utilize lithium metal anodes with cathode systems including iodine, manganese oxide, carbon monofluoride, silver vanadium oxide and hybrid cathodes. Secondary lithium ion batteries have also been developed for medical applications where the batteries are charged while remaining implanted. While the specific performance requirements of the devices vary, some general requirements are common. These include high safety, reliability and volumetric energy density, long service life, and state of discharge indication. Successful development and implementation of these battery types has helped enable implanted biomedical devices and their treatment of human disease. PMID:24179249

Batteries used to Power Implantable Biomedical Devices.

PubMed

Bock, David C; Marschilok, Amy C; Takeuchi, Kenneth J; Takeuchi, Esther S

2012-12-01

Battery systems have been developed that provide years of service for implantable medical devices. The primary systems utilize lithium metal anodes with cathode systems including iodine, manganese oxide, carbon monofluoride, silver vanadium oxide and hybrid cathodes. Secondary lithium ion batteries have also been developed for medical applications where the batteries are charged while remaining implanted. While the specific performance requirements of the devices vary, some general requirements are common. These include high safety, reliability and volumetric energy density, long service life, and state of discharge indication. Successful development and implementation of these battery types has helped enable implanted biomedical devices and their treatment of human disease.

Materials Design and System Construction for Conventional and New‐Concept Supercapacitors

PubMed Central

Wu, Zhong; Li, Lin

2017-01-01

With the development of renewable energy and electrified transportation, electrochemical energy storage will be more urgent in the future. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge rates, and long‐term cycling stability. During past five years, supercapacitors have been boomed benefited from the development of nanostructured materials synthesis and the promoted innovation of devices construction. In this review, we have summarized the current state‐of‐the‐art development on the fabrication of high‐performance supercapacitors. From the electrode material perspective, a variety of materials have been explored for advanced electrode materials with smart material‐design strategies such as carbonaceous materials, metal compounds and conducting polymers. Proper nanostructures are engineered to provide sufficient electroactive sites and enhance the kinetics of ion and electron transport. Besides, new‐concept supercapacitors have been developed for practical application. Microsupercapacitors and fiber supercapacitors have been explored for portable and compact electronic devices. Subsequently, we have introduced Li‐/Na‐ion supercapacitors composed of battery‐type electrodes and capacitor‐type electrode. Integrated energy devices are also explored by incorporating supercapacitors with energy conversion systems for sustainable energy storage. In brief, this review provides a comprehensive summary of recent progress on electrode materials design and burgeoning devices constructions for high‐performance supercapacitors. PMID:28638780

Materials Design and System Construction for Conventional and New-Concept Supercapacitors.

PubMed

Wu, Zhong; Li, Lin; Yan, Jun-Min; Zhang, Xin-Bo

2017-06-01

With the development of renewable energy and electrified transportation, electrochemical energy storage will be more urgent in the future. Supercapacitors have received extensive attention due to their high power density, fast charge and discharge rates, and long-term cycling stability. During past five years, supercapacitors have been boomed benefited from the development of nanostructured materials synthesis and the promoted innovation of devices construction. In this review, we have summarized the current state-of-the-art development on the fabrication of high-performance supercapacitors. From the electrode material perspective, a variety of materials have been explored for advanced electrode materials with smart material-design strategies such as carbonaceous materials, metal compounds and conducting polymers. Proper nanostructures are engineered to provide sufficient electroactive sites and enhance the kinetics of ion and electron transport. Besides, new-concept supercapacitors have been developed for practical application. Microsupercapacitors and fiber supercapacitors have been explored for portable and compact electronic devices. Subsequently, we have introduced Li-/Na-ion supercapacitors composed of battery-type electrodes and capacitor-type electrode. Integrated energy devices are also explored by incorporating supercapacitors with energy conversion systems for sustainable energy storage. In brief, this review provides a comprehensive summary of recent progress on electrode materials design and burgeoning devices constructions for high-performance supercapacitors.

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals.

PubMed

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J; Zhang, Yanliang

2016-09-12

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm(2) with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Varghese, Tony; Hollar, Courtney; Richardson, Joseph

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

DOE PAGES

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; ...

2016-09-12

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

PubMed Central

Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J.; Zhang, Yanliang

2016-01-01

Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm2 with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications. PMID:27615036

Scoping study for compact high-field superconducting net energy tokamaks

NASA Astrophysics Data System (ADS)

Mumgaard, R. T.; Greenwald, M.; Freidberg, J. P.; Wolfe, S. M.; Hartwig, Z. S.; Brunner, D.; Sorbom, B. N.; Whyte, D. G.

2016-10-01

The continued development and commercialization of high temperature superconductors (HTS) may enable the construction of compact, net-energy tokamaks. HTS, in contrast to present generation low temperature superconductors, offers improved performance in high magnetic fields, higher current density, stronger materials, higher temperature operation, and simplified assembly. Using HTS along with community-consensus confinement physics (H98 =1) may make it possible to achieve net-energy (Q>1) or burning plasma conditions (Q>5) in DIII-D or ASDEX-U sized, conventional aspect ratio tokamaks. It is shown that, by operating at high plasma current and density enabled by the high magnetic field (B>10T), the required triple products may be achieved at plasma volumes under 20m3, major radii under 2m, with external heating powers under 40MW. This is at the scale of existing devices operated by laboratories, universities and companies. The trade-offs in the core heating, divertor heat exhaust, sustainment, stability, and proximity to known plasma physics limits are discussed in the context of the present tokamak experience base and the requirements for future devices. The resulting HTS-based design space is compared and contrasted to previous studies on high-field copper experiments with similar missions. The physics exploration conducted with such HTS devices could decrease the real and perceived risks of ITER exploitation, and aid in quickly developing commercially-applicable tokamak pilot plants and reactors.

Multifunctional Woven Structure Operating as Triboelectric Energy Harvester, Capacitive Tactile Sensor Array, and Piezoresistive Strain Sensor Array

PubMed Central

Kim, Kihong; Song, Giyoung; Park, Cheolmin; Yun, Kwang-Seok

2017-01-01

This paper presents a power-generating sensor array in a flexible and stretchable form. The proposed device is composed of resistive strain sensors, capacitive tactile sensors, and a triboelectric energy harvester in a single platform. The device is implemented in a woven textile structure by using proposed functional threads. A single functional thread is composed of a flexible hollow tube coated with silver nanowires on the outer surface and a conductive silver thread inside the tube. The total size of the device is 60 × 60 mm2 having a 5 × 5 array of sensor cell. The touch force in the vertical direction can be sensed by measuring the capacitance between the warp and weft functional threads. In addition, because silver nanowire layers provide piezoresistivity, the strain applied in the lateral direction can be detected by measuring the resistance of each thread. Last, with regard to the energy harvester, the maximum power and power density were measured as 201 μW and 0.48 W/m2, respectively, when the device was pushed in the vertical direction. PMID:29120363

Elastic Fiber Supercapacitors for Wearable Energy Storage.

PubMed

Qin, Si; Seyedin, Shayan; Zhang, Jizhen; Wang, Zhiyu; Yang, Fangli; Liu, Yuqing; Chen, Jun; Razal, Joselito M

2018-05-17

The development of wearable devices such as smart watches, intelligent garments, and wearable health-monitoring devices calls for suitable energy storage devices which have matching mechanical properties and can provide sufficient power for a reasonable duration. Stretchable fiber-based supercapacitors are emerging as a promising candidates for this purpose because they are lightweight, flexible, have high energy and power density, and the potential for easy integration into traditional textile processes. An important characteristic that is oftentimes ignored is stretchability-fiber supercapacitors should be able to accommodate large elongation during use, endure a range of bending motions, and then revert to its original form without compromising electrical and electrochemical performance. This article summarizes the current research progress on stretchable fiber-based supercapacitors and discusses the existing challenges on material preparation and fiber-based device fabrication. This article aims to help researchers in the field to better understand the challenges related to material design and fabrication approaches of fiber-based supercapacitors, and to provide insights and guidelines toward their wearability. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Energy dynamics in a simulation of LAPD turbulence

NASA Astrophysics Data System (ADS)

Friedman, B.; Carter, T. A.; Umansky, M. V.; Schaffner, D.; Dudson, B.

2012-10-01

Energy dynamics calculations in a 3D fluid simulation of drift wave turbulence in the linear Large Plasma Device [W. Gekelman et al., Rev. Sci. Instrum. 62, 2875 (1991)] illuminate processes that drive and dissipate the turbulence. These calculations reveal that a nonlinear instability dominates the injection of energy into the turbulence by overtaking the linear drift wave instability that dominates when fluctuations about the equilibrium are small. The nonlinear instability drives flute-like (k∥=0) density fluctuations using free energy from the background density gradient. Through nonlinear axial wavenumber transfer to k∥≠0 fluctuations, the nonlinear instability accesses the adiabatic response, which provides the requisite energy transfer channel from density to potential fluctuations as well as the phase shift that causes instability. The turbulence characteristics in the simulations agree remarkably well with experiment. When the nonlinear instability is artificially removed from the system through suppressing k∥=0 modes, the turbulence develops a coherent frequency spectrum which is inconsistent with experimental data. This indicates the importance of the nonlinear instability in producing experimentally consistent turbulence.

Current-induced changes of migration energy barriers in graphene and carbon nanotubes

NASA Astrophysics Data System (ADS)

Obodo, J. T.; Rungger, I.; Sanvito, S.; Schwingenschlögl, U.

2016-05-01

An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative.An electron current can move atoms in a nanoscale device with important consequences for the device operation and breakdown. We perform first principles calculations aimed at evaluating the possibility of changing the energy barriers for atom migration in carbon-based systems. In particular, we consider the migration of adatoms and defects in graphene and carbon nanotubes. Although the current-induced forces are large for both the systems, in graphene the force component along the migration path is small and therefore the barrier height is little affected by the current flow. In contrast, the same barrier is significantly reduced in carbon nanotubes as the current increases. Our work also provides a real-system numerical demonstration that current-induced forces within density functional theory are non-conservative. Electronic supplementary information (ESI) available. See DOI: 10.1039/C6NR00534A

A Novel Type of Battery-Supercapacitor Hybrid Device with Highly Switchable Dual Performances Based on a Carbon Skeleton/Mg2Ni Free-Standing Hydrogen Storage Electrode.

PubMed

Li, Na; Du, Yi; Feng, Qing-Ping; Huang, Gui-Wen; Xiao, Hong-Mei; Fu, Shao-Yun

2017-12-27

The sharp proliferation of high power electronics and electrical vehicles has promoted growing demands for power sources with both high energy and power densities. Under these circumstances, battery-supercapacitor hybrid devices are attracting considerable attention as they combine the advantages of both batteries and supercapacitors. Here, a novel type of hybrid device based on a carbon skeleton/Mg 2 Ni free-standing electrode without the traditional nickel foam current collector is reported, which has been designed and fabricated through a dispersing-freeze-drying method by employing reduced graphene oxide (rGO) and multiwalled carbon nanotubes (MWCNTs) as a hybrid skeleton. As a result, the Mg 2 Ni alloy is able to deliver a high discharge capacity of 644 mAh g -1 and, more importantly, a high cycling stability with a retention of over 78% after 50 charge/discharge cycles have been achieved, which exceeds almost all the results ever reported on the Mg 2 Ni alloy. Simultaneously, the electrode could also exhibit excellent supercapacitor performances including high specific capacities (296 F g -1 ) and outstanding cycling stability (100% retention after 100 cycles). Moreover, the hybrid device can switch between battery and supercapacitor modes immediately as needed during application. These features make the C skeleton/alloy electrode a highly promising candidate for battery-supercapacitor hybrid devices with high power/energy density and favorable cycling stability.

Electrochemical supercapacitors from conducting polyaniline-graphene platforms.

PubMed

Ashok Kumar, Nanjundan; Baek, Jong-Beom

2014-06-18

Energy storage devices such as electrochemical supercapacitors, with high power and energy densities are required to address the colossal energy requirements against the backdrop of global warming and the looming energy crisis. Nanocarbon, particularly two-dimensional graphene and graphene-based conducting polymer composites are promising electrode materials for such energy storage devices. Owing to their environmental stability, the low cost of polymers with high electroactivity and pseudocapacitance, such composite hybrids are expected to have wide implications in next generation clean and efficient energy systems. In this feature article, an overview of current research and important advances over the past four years on the development of conducting polyaniline (PANI)-graphene based composite electrodes for electrochemical supercapacitors are highlighted. Particular emphasis is made on the design, fabrication and assembly of nanostructured electrode architectures comprising PANI and graphene along with metal oxides/hydroxides and carbon nanotubes. Comments on the challenges and perspectives towards rational design and synthesis of graphene-based conducting polymer composites for energy storage are discussed.

Quantum Mechanical Calculations of Free Energy and Open-Circuit Voltage in Lattice Modeled Organic Photovoltaic Devices

NASA Astrophysics Data System (ADS)

Lankevich, Vladimir; Bittner, Eric

In organic photovoltaic devices (OPVs), initially bound electron and hole can take many different paths to dissociate and become free charge carriers. This leads to the increase in their density of states and therefore increase in the entropy of the system. Accurate description of the energy barriers that charges have to overcome, therefore requires calculation of the free energy. Free energy of an OPV is directly related to its open-circuit voltage and depends only on few important parameters such as average life-time of a charge-transfer state, average energy of the charge-transfer state and energetic disorder in the system. We extend these ideas to the quantum mechanical simulations of the dissociation in the lattice modeled bulk-heterojunction system. We observe average excitonic and free energies that agree with theoretical predictions and the number of experimental results from previous studies. We study effects of the energy disorder and importance of the dimensionality and morphology in materials such as polymer-fullerene blends.

Rapid Assemblers for Voxel-Based VLSI Robotics

DTIC Science & Technology

2014-02-12

relied on coin- cell batteries with high energy density, but low power density. Each of the actuators presented requires relatively high power...The device consists of a low power DC- DC low to high voltage converter operated by 4A cell batteries and an assembler, which is a grid of electrodes...design, simulate and fabricate complex 3D machines, as well as to repair, adapt and recycle existing machines, and to perform rigorous design

SC-CO2-assisted process for a high energy density aerogel supercapacitor: the effect of GO loading

NASA Astrophysics Data System (ADS)

Sarno, Maria; Baldino, Lucia; Scudieri, Carmela; Cardea, Stefano; Ciambelli, Paolo; Reverchon, Ernesto

2017-05-01

Energy density, safety, and simple and environmentally friendly preparation methods are very significant aspects in the realization of a compact supercapacitor. Herein we report the use of a supercritical CO2-assisted gel drying process (SC-CO2) for the preparation of porous electrodes containing dispersed graphene in a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder membrane to sandwich in a new portable supercapacitor based on graphene oxide (GO). A GO loading of 60 wt.% was found to give the best combination of factors (porosity, wettability, mechanical and electrochemical properties). Cycling voltammetry and charge/discharge studies showed an excellent capacitance behaviour and stability in an ionic liquid electrolyte, suggesting SC-CO2 processing as a promising platform to produce highly bulky and porous films for supercapacitors. The supercapacitor device delivers a very high energy density of 79.2 Wh kg-1 at a power density of 0.23 KW kg-1 (current density 0.5 A g-1, specific capacitance 36.2 F g-1) while that of steel remains at 50.3 Wh kg-1 at a power density of 2.8 KW kg-1 (current density 6 A g-1, specific capacitance 23.5 F g-1).

SC-CO2-assisted process for a high energy density aerogel supercapacitor: the effect of GO loading.

PubMed

Sarno, Maria; Baldino, Lucia; Scudieri, Carmela; Cardea, Stefano; Ciambelli, Paolo; Reverchon, Ernesto

2017-05-19

Energy density, safety, and simple and environmentally friendly preparation methods are very significant aspects in the realization of a compact supercapacitor. Herein we report the use of a supercritical CO 2 -assisted gel drying process (SC-CO 2 ) for the preparation of porous electrodes containing dispersed graphene in a poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP) binder membrane to sandwich in a new portable supercapacitor based on graphene oxide (GO). A GO loading of 60 wt.% was found to give the best combination of factors (porosity, wettability, mechanical and electrochemical properties). Cycling voltammetry and charge/discharge studies showed an excellent capacitance behaviour and stability in an ionic liquid electrolyte, suggesting SC-CO 2 processing as a promising platform to produce highly bulky and porous films for supercapacitors. The supercapacitor device delivers a very high energy density of 79.2 Wh kg -1 at a power density of 0.23 KW kg -1 (current density 0.5 A g -1 , specific capacitance 36.2 F g -1 ) while that of steel remains at 50.3 Wh kg -1 at a power density of 2.8 KW kg -1 (current density 6 A g -1 , specific capacitance 23.5 F g -1 ).

Novel Potassium-Ion Hybrid Capacitor Based on an Anode of K2Ti6O13 Microscaffolds.

PubMed

Dong, Shengyang; Li, Zhifei; Xing, Zhenyu; Wu, Xianyong; Ji, Xiulei; Zhang, Xiaogang

2018-05-09

To fill the gap between batteries and supercapacitors requires integration of the following features in a single system: energy density well above that of supercapacitors, cycle life much longer than Li-ion batteries, and low cost. Along this line, we report a novel nonaqueous potassium-ion hybrid capacitor (KIC) that employs an anode of K 2 Ti 6 O 13 (KTO) microscaffolds constructed by nanorods and a cathode of N-doped nanoporous graphenic carbon (NGC). K 2 Ti 6 O 13 microscaffolds are studied for potential applications as the anode material in potassium-ion storage for the first time. This material exhibits an excellent capacity retention of 85% after 1000 cycles. In addition, the NGC//KTO KIC delivers a high energy density of 58.2 Wh kg -1 based on the active mass in both electrodes, high power density of 7200 W kg -1 , and outstanding cycling stability over 5000 cycles. The usage of K ions as the anode charge carrier instead of Li ions and the amenable performance of this device suggest that hybrid capacitor devices may welcome a new era of beyond lithium.

Design and construction of three-dimensional CuO/polyaniline/rGO ternary hierarchical architectures for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Zhu, Sheng; Wu, Mi; Ge, Mei-Hong; Zhang, Hui; Li, Shi-Kuo; Li, Chuan-Hao

2016-02-01

Rational design in terms of component and microstructure and fabrication of electrochemical electrodes are crucially important towards superior energy storage device. Herein, we report a novel CuO-PANI-rGO ternary hybrid electrode self-assembled by an in situ polymerization method combined with hydrothermal route for electrochemical capacitor. Well-defined CuO hierarchical architecture is synthesized by the spontaneous oxidization of Cu nanowire. PANI acts as not only binder for anchoring CuO architecture on rGO surface, but also charge transport channels, and high specific capacitance donor to the whole electrode matrix. The typical CuO-PANI-rGO ternary hybrid electrode can be reversibly cycled in a high voltage region up to 1.2 V. And it displays a maximum specific capacitance of 634.4 F g-1 and a high energy density of 126.8 Wh kg-1 with a power density of 114.2 kW kg-1 at a current density of 1.0 A g-1. Furthermore, the ternary hybrid electrode exhibits great cycle life with 97.4% specific capacitance retention after 10000 cycles. Those excellent performances are proposed to derive from the well-defined nanostructure, conductive porous microstructure and homogenously contact. This study might be important for designing the unique structure and component electrode for achieving high performance energy storage device.

Spectroscopic determination of the composition of a 50 kV hydrogen diagnostic neutral beam

DOE Office of Scientific and Technical Information (OSTI.GOV)

Feng, X.; Nornberg, M. D., E-mail: mdnornberg@wisc.edu; Den Hartog, D. J.

2016-11-15

A grating spectrometer with an electron multiplying charge-coupled device camera is used to diagnose a 50 kV, 5 A, 20 ms hydrogen diagnostic neutral beam. The ion source density is determined from Stark broadened H{sub β} emission and the spectrum of Doppler-shifted H{sub α} emission is used to quantify the fraction of ions at full, half, and one-third beam energy under a variety of operating conditions including fueling gas pressure and arc discharge current. Beam current is optimized at low-density conditions in the ion source while the energy fractions are found to be steady over most operating conditions.

Development of a hybrid battery system for an implantable biomedical device, especially a defibrillator/cardioverter (ICD)

NASA Astrophysics Data System (ADS)

Drews, Jürgen; Wolf, R.; Fehrmann, G.; Staub, R.

An implantable defibrillator battery has to provide pulse power capabilities as well as high energy density. Low self-discharge rates are mandatory and a way to check the remaining available capacity is necessary. These requirements are accomplished by a system consisting of a lithium/manganese dioxide 6 V battery, plus a lithium/iodine-cell. The use of a high rate 6 V double-cell design in combination with a high energy density cell reduces the total volume required by the power source within an implantable defibrillator. The design features and performance data of the hybrid system are described.

Charged Particle Detection: Potential of Love Wave Acoustic Devices

NASA Astrophysics Data System (ADS)

Pedrick, Michael; Tittmann, Bernhard

2006-03-01

An investigation of the dependence of film density on group and phase velocities in a Love Wave Device shows potential for acoustic-based charged particle detection (CPD). Exposure of an ion sensitive photoresist to charged particles causes localized changes in density through either scission or cross-linking. A theoretical model was developed to study ion fluence effects on Love Wave sensitivity based on: ion energy, effective density changes, layer thickness and mode selection. The model is based on a Poly(Methyl Methacralate) (PMMA) film deposited on a Quartz substrate. The effect of Helium ion fluence on the properties of PMMA has previously been studied. These guidelines were used as an initial basis for the prediction of helium ion detection in a PMMA layer. Procedures for experimental characterization of ion effects on the material properties of PMMA are reviewed. Techniques for experimental validation of the predicted velocity shifts are discussed. A Love Wave Device for CPD could potentially provide a cost-effective alternative to semiconductor or photo-based counterparts. The potential for monitoring ion implantation effects on material properties is also discussed.

Three-dimensional bicontinuous nanoporous Au/polyaniline hybrid films for high-performance electrochemical supercapacitors

NASA Astrophysics Data System (ADS)

Lang, Xingyou; Zhang, Ling; Fujita, Takeshi; Ding, Yi; Chen, Mingwei

2012-01-01

We report three-dimensional bicontinuous nanoporous Au/polyaniline (PANI) composite films made by one-step electrochemical polymerization of PANI shell onto dealloyed nanoporous gold (NPG) skeletons for the applications in electrochemical supercapacitors. The NPG/PANI based supercapacitors exhibit ultrahigh volumetric capacitance (∼1500 F cm-3) and energy density (∼0.078 Wh cm-3), which are seven and four orders of magnitude higher than these of electrolytic capacitors, with the same power density up to ∼190 W cm-3. The outstanding capacitive performances result from a novel nanoarchitecture in which pseudocapacitive PANI shells are incorporated into pore channels of highly conductive NPG, making them promising candidates as electrode materials in supercapacitor devices combing high-energy storage densities with high-power delivery.

An Introduction to System-Level, Steady-State and Transient Modeling and Optimization of High-Power-Density Thermoelectric Generator Devices Made of Segmented Thermoelectric Elements

NASA Astrophysics Data System (ADS)

Crane, D. T.

2011-05-01

High-power-density, segmented, thermoelectric (TE) elements have been intimately integrated into heat exchangers, eliminating many of the loss mechanisms of conventional TE assemblies, including the ceramic electrical isolation layer. Numerical models comprising simultaneously solved, nonlinear, energy balance equations have been created to simulate these novel architectures. Both steady-state and transient models have been created in a MATLAB/Simulink environment. The models predict data from experiments in various configurations and applications over a broad range of temperature, flow, and current conditions for power produced, efficiency, and a variety of other important outputs. Using the validated models, devices and systems are optimized using advanced multiparameter optimization techniques. Devices optimized for particular steady-state operating conditions can then be dynamically simulated in a transient operating model. The transient model can simulate a variety of operating conditions including automotive and truck drive cycles.

Performance of Liquid Phase Exfoliated Graphene As Electrochemical Double Layer Capacitors Electrodes

NASA Astrophysics Data System (ADS)

Huffstutler, Jacob; Wasala, Milinda; Richie, Julianna; Winchester, Andrew; Ghosh, Sujoy; Kar, Swastik; Talapatra, Saikat

2014-03-01

We will present the results of our investigations of electrochemical double layer capacitors (EDLCs) or supercapacitors (SC) fabricated using liquid-phase exfoliated graphene. Several electrolytes, such as aqueous potassium hydroxide KOH (6M), ionic 1-Butyl-3-methylimidazolium hexafluorophosphate [BMIM][PF6], and ionic 1-butyl-1-methylpyrrolidinium tris(pentafluoroethyl)trifluorophosphate[BMP][FAP] were used. These EDLC's show good performance compared to other carbon nanomaterials based EDLC's devices. We found that the liquid phase exfoliated graphene based devices possess specific capacitance values as high as 262 F/g, when used with ionic liquid electrolyte[BMP][FAP], with power densities (~ 454 W/kg) and energy densities (~ 0.38Wh/kg). Further, these devices indicated rapid charge transfer response even without the use of any binders or specially prepared current collectors. A detailed electrochemical impedance spectroscopy analysis in order to understand the phenomenon of charge storage in these materials will be presented.

More Reliable Lithium-Sulfur Batteries: Status, Solutions and Prospects.

PubMed

Fang, Ruopian; Zhao, Shiyong; Sun, Zhenhua; Wang, Da-Wei; Cheng, Hui-Ming; Li, Feng

2017-12-01

Lithium-sulfur (Li-S) batteries have attracted tremendous interest because of their high theoretical energy density and cost effectiveness. The target of Li-S battery research is to produce batteries with a high useful energy density that at least outperforms state-of-the-art lithium-ion batteries. However, due to an intrinsic gap between fundamental research and practical applications, the outstanding electrochemical results obtained in most Li-S battery studies indeed correspond to low useful energy densities and are not really suitable for practical requirements. The Li-S battery is a complex device and its useful energy density is determined by a number of design parameters, most of which are often ignored, leading to the failure to meet commercial requirements. The purpose of this review is to discuss how to pave the way for reliable Li-S batteries. First, the current research status of Li-S batteries is briefly reviewed based on statistical information obtained from literature. This includes an analysis of how the various parameters influence the useful energy density and a summary of existing problems in the current Li-S battery research. Possible solutions and some concerns regarding the construction of reliable Li-S batteries are comprehensively discussed. Finally, insights are offered on the future directions and prospects in Li-S battery field. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

PubMed Central

Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; zhao, Ruo; Zou, Ruqiang

2017-01-01

To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g−1 at a current density of 1A g−1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg−1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg−1 at power density of 9331 Wkg−1 coupled long termed stability up to 6000 cycles. PMID:28240224

Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors.

PubMed

Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; Zhao, Ruo; Zou, Ruqiang

2017-02-27

To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH) 2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH) 2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g -1 at a current density of 1A g -1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH) 2 @CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg -1 . This device also exhibits excellent rate capability with energy density of 15.55 Whkg -1 at power density of 9331 Wkg -1 coupled long termed stability up to 6000 cycles.

Parameter scaling toward high-energy density in a quasi-steady flow Z-pinch

NASA Astrophysics Data System (ADS)

Hughes, M. C.; Shumlak, U.; Nelson, B. A.; Golingo, R. P.; Claveau, E. L.; Doty, S. A.; Forbes, E. G.; Kim, B.; Ross, M. P.

2016-10-01

Sheared axial flows are utilized by the ZaP Flow Z-Pinch Experiment to stabilize MHD instabilities. The pinches formed are 50 cm long with radii ranging from 0.3 to 1.0 cm. The plasma is generated in a coaxial acceleration region, similar to a Marshall gun, which provides a steady supply of plasma for approximately 100 us. The power to the plasma is partially decoupled between the acceleration and pinch assembly regions through the use of separate power supplies. Adiabatic scaling of the Bennett relation gives targets for future devices to reach high-energy density conditions or fusion reactors. The applicability of an adiabatic assumption is explored and work is done experimentally to clarify the plasma compression process, which may be more generally polytropic. The device is capable of a much larger parameter space than previous machine iterations, allowing flexibility in the initial conditions of the compression process to preserve stability. This work is supported by DoE FES and NNSA.

Baseline Testing of Ultracapacitors for the Next Generation Launch Technology (NGLT) Project. Revised

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2005-01-01

The NASA John H. Glenn Research Center initiated baseline testing of ultracapacitors for the Next Generation Launch Transportation (NGLT) project to obtain empirical data for determining the feasibility of using ultracapacitors for the project. There are large transient loads associated with NGLT that require either a very large primary energy source or an energy storage system. The primary power source used for these tests is a proton exchange membrane (PEM) fuel cell. The energy storage system can consist of devices such as batteries, flywheels, or ultracapacitors. Ultracapacitors were used for these tests. Ultracapacitors are ideal for applications such as NGLT where long life, maintenance-free operation, and excellent low-temperature performance is essential. State-of-the-art symmetric ultracapacitors were used for these tests. The ultracapacitors were interconnected in an innovative configuration to minimize interconnection impedance. PEM fuel cells provide excellent energy density, but not good power density. Ultracapacitors provide excellent power density, but not good energy density. The combination of PEM fuel cells and ultracapacitors provides a power source with excellent energy density and power density. The life of PEM fuel cells is shortened significantly by large transient loads. Ultracapacitors used in conjunction with PEM fuel cells reduce the transient loads applied to the fuel cell, and thus appreciably improves its life. PEM fuel cells were tested with and without ultracapacitors, to determine the benefits of ultracapacitors. The report concludes that the implementation of symmetric ultracapacitors in the NGLT power system can provide significant improvements in power system performance and reliability.

Baseline Testing of Ultracapacitors for the Next Generation Launch Technology (NGLT) Project

NASA Technical Reports Server (NTRS)

Eichenberg, Dennis J.

2004-01-01

The NASA John H. Glenn Research Center initiated baseline testing of ultracapacitors for the Next Generation Launch Transportation (NGLT) project to obtain empirical data for determining the feasibility of using ultracapacitors for the project. There are large transient loads associated with NGLT that require either a very large primary energy source or an energy storage system. The primary power source used for these tests is a proton exchange membrane (PEM) fuel cell. The energy storage system can consist of devices such as batteries, flywheels, or ultracapacitors. Ultracapacitors were used for these tests. Ultracapacitors are ideal for applications such as NGLT where long life, maintenance-free operation, and excellent low-temperature performance is essential. State-of-the-art symmetric ultracapacitors were used for these tests. The ultracapacitors were interconnected in an innovative configuration to minimize interconnection impedance. PEM fuel cells provide excellent energy density, but not good power density. Ultracapacitors provide excellent power density, but not good energy density. The combination of PEM fuel cells and ultracapacitors provides a power source with excellent energy density and power density. The life of PEM fuel cells is shortened significantly by large transient loads. Ultracapacitors used in conjunction with PEM fuel cells reduce the transient loads applied to the fuel cell, and thus appreciably improves its life. PEM fuel cells were tested with and without ultracapacitors, to determine the benefits of ultracapacitors. The report concludes that the implementation of symmetric ultracapacitors in the NGLT power system can provide significant improvements in power system performance and reliability.

All-solid state symmetric supercapacitors based on compressible and flexible free-standing 3D carbon nanotubes (CNTs)/poly(3,4-ethylenedioxythiophene) (PEDOT) sponge electrodes

NASA Astrophysics Data System (ADS)

He, Xin; Yang, Wenyao; Mao, Xiling; Xu, Lu; Zhou, Yujiu; Chen, Yan; Zhao, Yuetao; Yang, Yajie; Xu, Jianhua

2018-02-01

Flexible supercapacitors that maintain electrochemical performance under deformation have attracted much attention for the potential application in the flexible electronics market. A compressible and flexible free-standing electrodes sponge and all-solid-state symmetric supercapacitors based on as-prepared electrodes are presented. The carbon nanotubes (CNTs) framework is synthesized by chemical vapor deposition (CVD) method, and then composited with poly (3,4-ethylenedioxythiophene) PEDOT by the electrodeposition. This CNTs/PEDOT sponge electrode shows highest mass-specific capacitance of 147 Fg-1 at 0.5 A g-1, tuned by the PEDOT mass loading, and exhibits good cyclic stability with the evidence that more than 95% of capacitance is remained after 3000 cycles. Furthermore, the symmetric supercapacitor shows the highest energy density of 12.6 Wh kg-1 under the power density of 1 kW kg-1 and highest power density of 10.2 kW kg-1 with energy density of 8 Wh kg-1, which exhibits both high energy density and power density. The electrochemical performance of composite electrode also indicates that the operate voltage of device could be extend to 1.4 V by the n-doping and p-doping process in different potential of PEDOT component. This flexible supercapacitor maintains stable electrochemical performance working on different bending condition, which shows promising prospect for wearable energy storage applications.

Electrical and Optical Performance Characteristics of 0.74-eV p/n InGaAs Monolithic Interconnected Modules

NASA Technical Reports Server (NTRS)

Wilt, David M.; Fatemi, Navid S.; Jenkins, Phillip P.; Weizer, Victor G.; Hoffman, Richard W., Jr.; Jain, Raj K.; Murray, Christopher S.; Riley, David R.

1997-01-01

There has been a traditional trade-off in thermophotovoltaic (TPV) energy conversion development between system efficiency and power density. This trade-off originates from the use of front surface spectral controls such as selective emitters and various types of filters. A monolithic interconnected module (MIM) structure has been developed which allows for both high power densities and high system efficiencies. The MIM device consists of many individual indium gallium arsenide (InGaAs) cells series-connected on a single semi-insulating indium phosphide (InP) substrate. The MIM is exposed to the entire emitter output, thereby maximizing output power density. An infrared (IR) reflector placed on the rear surface of the substrate returns the unused portion of the emitter output spectrum back to the emitter for recycling, thereby providing for high system efficiencies. Initial MIM development has focused on a 1 sq cm device consisting of eight (8) series interconnected cells. MIM devices, produced from 0.74-eV InGaAs, have demonstrated V(sub oc) = 3.2 volts, J(sub sc) = 70 mA/sq cm, and a fill factor of 66% under flashlamp testing. Infrared (IR) reflectance measurements (greater than 2 micron) of these devices indicate a reflectivity of greater than 82%. MIM devices produced from 0.55-eV InGaAs have also been demonstrated. In addition, conventional p/n InGaAs devices with record efficiencies (11.7% AM0) have been demonstrated.

Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting

PubMed Central

Hsu, Tsung-Hsing; Manakasettharn, Supone; Taylor, J. Ashley; Krupenkin, Tom

2015-01-01

We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10−6 W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible. PMID:26567850

Bubbler: A Novel Ultra-High Power Density Energy Harvesting Method Based on Reverse Electrowetting.

PubMed

Hsu, Tsung-Hsing; Manakasettharn, Supone; Taylor, J Ashley; Krupenkin, Tom

2015-11-16

We have proposed and successfully demonstrated a novel approach to direct conversion of mechanical energy into electrical energy using microfluidics. The method combines previously demonstrated reverse electrowetting on dielectric (REWOD) phenomenon with the fast self-oscillating process of bubble growth and collapse. Fast bubble dynamics, used in conjunction with REWOD, provides a possibility to increase the generated power density by over an order of magnitude, as compared to the REWOD alone. This energy conversion approach is particularly well suited for energy harvesting applications and can enable effective coupling to a broad array of mechanical systems including such ubiquitous but difficult to utilize low-frequency energy sources as human and machine motion. The method can be scaled from a single micro cell with 10(-6) W output to power cell arrays with a total power output in excess of 10 W. This makes the fabrication of small light-weight energy harvesting devices capable of producing a wide range of power outputs feasible.

3D macroporous graphene frameworks for supercapacitors with high energy and power densities.

PubMed

Choi, Bong Gill; Yang, Minho; Hong, Won Hi; Choi, Jang Wook; Huh, Yun Suk

2012-05-22

In order to develop energy storage devices with high power and energy densities, electrodes should hold well-defined pathways for efficient ionic and electronic transport. Herein, we demonstrate high-performance supercapacitors by building a three-dimensional (3D) macroporous structure that consists of chemically modified graphene (CMG). These 3D macroporous electrodes, namely, embossed-CMG (e-CMG) films, were fabricated by using polystyrene colloidal particles as a sacrificial template. Furthermore, for further capacitance boost, a thin layer of MnO(2) was additionally deposited onto e-CMG. The porous graphene structure with a large surface area facilitates fast ionic transport within the electrode while preserving decent electronic conductivity and thus endows MnO(2)/e-CMG composite electrodes with excellent electrochemical properties such as a specific capacitance of 389 F/g at 1 A/g and 97.7% capacitance retention upon a current increase to 35 A/g. Moreover, when the MnO(2)/e-CMG composite electrode was asymmetrically assembled with an e-CMG electrode, the assembled full cell shows remarkable cell performance: energy density of 44 Wh/kg, power density of 25 kW/kg, and excellent cycle life.

Fabrication and characterization of high current-density, submicron, NbN/MgO/NbN tunnel junctions

NASA Technical Reports Server (NTRS)

Stern, J. A.; Leduc, Henry G.; Judas, A. J.

1992-01-01

At near-millimeter wavelengths, heterodyne receivers based on SIS tunnel junctions are the most sensitive available. However, in order to scale these results to submillimeter wavelengths, certain device properties should be scaled. The tunnel-junction's current density should be increased to reduce the RC product. The device's area should be reduced to efficiently couple power from the antenna to the mixer. Finally, the superconductor used should have a large energy gap to minimize RF losses. Most SIS mixers use Nb or Pb-alloy tunnel junctions; the gap frequency for these materials is approximately 725 GHz. Above the gap frequency, these materials exhibit losses similar to those in a normal metal. The gap frequency in NbN films is as-large-as 1440 GHz. Therefore, we have developed a process to fabricate small area (down to 0.13 sq microns), high current density, NbN/MgO/NbN tunnel junctions.

Shear-horizontal surface acoustic wave phononic device with high density filling material for ultra-low power sensing applications

NASA Astrophysics Data System (ADS)

Richardson, M.; Sankaranarayanan, S. K. R. S.; Bhethanabotla, V. R.

2014-06-01

Finite element simulations of a phononic shear-horizontal surface acoustic wave (SAW) sensor based on ST 90°-X Quartz reveal a dramatic reduction in power consumption. The phononic sensor is realized by artificially structuring the delay path to form an acoustic meta-material comprised of a periodic microcavity array incorporating high-density materials such as tantalum or tungsten. Constructive interference of the scattered and secondary reflected waves at every microcavity interface leads to acoustic energy confinement in the high-density regions translating into reduced power loss. Tantalum filled cavities show the best performance while tungsten inclusions create a phononic bandgap. Based on our simulation results, SAW devices with tantalum filled microcavities were fabricated and shown to significantly decrease insertion loss. Our findings offer encouraging prospects for designing low power, highly sensitive portable biosensors.

Modeling and design of Galfenol unimorph energy harvesters

NASA Astrophysics Data System (ADS)

Deng, Zhangxian; Dapino, Marcelo J.

2015-12-01

This article investigates the modeling and design of vibration energy harvesters that utilize iron-gallium (Galfenol) as a magnetoelastic transducer. Galfenol unimorphs are of particular interest; however, advanced models and design tools are lacking for these devices. Experimental measurements are presented for various unimorph beam geometries. A maximum average power density of 24.4 {mW} {{cm}}-3 and peak power density of 63.6 {mW} {{cm}}-3 are observed. A modeling framework with fully coupled magnetoelastic dynamics, formulated as a 2D finite element model, and lumped-parameter electrical dynamics is presented and validated. A comprehensive parametric study considering pickup coil dimensions, beam thickness ratio, tip mass, bias magnet location, and remanent flux density (supplied by bias magnets) is developed for a 200 Hz, 9.8 {{m}} {{{s}}}-2 amplitude harmonic base excitation. For the set of optimal parameters, the maximum average power density and peak power density computed by the model are 28.1 and 97.6 {mW} {{cm}}-3, respectively.

All-solid state, flexible, high-energy integrated hybrid micro-supercapacitors based on 3D LSG/CoNi2S4 nanosheets.

PubMed

Moosavifard, Seyyed Ebrahim; Shamsi, Javad; Altafi, Mohammad Kazem; Moosavifard, Zeinab Sadat

2016-11-18

3D LSG/CoNi 2 S 4 //LSG interdigitated microelectrodes have been firstly developed by a facile, scalable and low cost process for all-solid-state, flexible integrated asymmetric micro-supercapacitors. These devices can achieve energy densities of up to 49 W h l -1 which is comparable to those of lead acid batteries.

Popcorn-Derived Porous Carbon Flakes with an Ultrahigh Specific Surface Area for Superior Performance Supercapacitors.

PubMed

Hou, Jianhua; Jiang, Kun; Wei, Rui; Tahir, Muhammad; Wu, Xiaoge; Shen, Ming; Wang, Xiaozhi; Cao, Chuanbao

2017-09-13

Popcorn-derived porous carbon flakes have been successfully fabricated from the biomass of maize. Utilizing the "puffing effect", the nubby maize grain turned into materials with an interconnected honeycomb-like porous structure composed of carbon flakes. The following chemical activation method enabled the as-prepared products to possess optimized porous structures for electrochemical energy-storage devices, such as multilayer flake-like structures, ultrahigh specific surface area (S BET : 3301 m 2 g -1 ), and a high content of micropores (microporous surface area of 95%, especially the optimized sub-nanopores with the size of 0.69 nm) that can increase the specific capacitance. The as-obtained sample displayed excellent specific capacitance of 286 F g -1 at 90 A g -1 for supercapacitors. Moreover, the unique porous structure demonstrated an ideal way to improve the volumetric energy density performance. A high energy density of 103 Wh kg -1 or 53 Wh L -1 has been obtained in the case of ionic liquid electrolyte, which is the highest among reported biomass-derived carbon materials and will satisfy the urgent requirements of a primary power source for electric vehicles. This work may prove to be a fast, green, and large-scale synthesis route by using the large nubby granular materials to synthesize applicable porous carbons in energy-storage devices.

Design of Amorphous Manganese Oxide@Multiwalled Carbon Nanotube Fiber for Robust Solid-State Supercapacitor.

PubMed

Shi, Peipei; Li, Li; Hua, Li; Qian, Qianqian; Wang, Pengfei; Zhou, Jinyuan; Sun, Gengzhi; Huang, Wei

2017-01-24

Solid-state fiber-based supercapacitors have been considered promising energy storage devices for wearable electronics due to their lightweight and amenability to be woven into textiles. Efforts have been made to fabricate a high performance fiber electrode by depositing pseudocapacitive materials on the outer surface of carbonaceous fiber, for example, crystalline manganese oxide/multiwalled carbon nanotubes (MnO 2 /MWCNTs). However, a key challenge remaining is to achieve high specific capacitance and energy density without compromising the high rate capability and cycling stability. In addition, amorphous MnO 2 is actually preferred due to its disordered structure and has been proven to exhibit superior electrochemical performance over the crystalline one. Herein, by incorporating amorphous MnO 2 onto a well-aligned MWCNT sheet followed by twisting, we design an amorphous MnO 2 @MWCNT fiber, in which amorphous MnO 2 nanoparticles are distributed in MWCNT fiber uniformly. The proposed structure gives the amorphous MnO 2 @MWCNT fiber good mechanical reliability, high electrical conductivity, and fast ion-diffusion. Solid-state supercapacitor based on amorphous MnO 2 @MWCNT fibers exhibits improved energy density, superior rate capability, exceptional cycling stability, and excellent flexibility. This study provides a strategy to design a high performance fiber electrode with microstructure control for wearable energy storage devices.

Temperature effect on betavoltaic microbatteries based on Si and GaAs under 63Ni and 147Pm irradiation

NASA Astrophysics Data System (ADS)

Wang, Hao; Tang, Xiao-bin; Liu, Yun-Peng; Xu, Zhi-Heng; Liu, Min; Chen, Da

2015-09-01

The effect of temperature on the output performance of four different types of betavoltaic microbatteries was investigated experimental and theoretical. Si and GaAs were selected as the energy conversion devices in four types of betavoltaic microbatteries, and 63Ni and 147Pm were used as beta sources. Current density-voltage curves were determined at a temperature range of 213.15-333.15 K. A simplified method was used to calculate the theoretical parameters of the betavoltaic microbatteries considering the energy loss of beta particles for self-absorption of radioactive source, the electron backscatter effect of different types of semiconductor materials, and the absorption of dead layer. Both the experimental and theoretical results show that the short-circuit current density increases slightly and the open-circuit voltage (VOC) decreases evidently with the increase in temperature. Different combinations of energy conversion devices and beta sources cause different effects of temperature on the microbatteries. In the approximately linear range, the VOC sensitivities caused by temperature for 63Ni-Si, 63Ni-GaAs, 147Pm-Si, and 147Pm-GaAs betavoltaic microbatteries were -2.57, -5.30, -2.53, and -4.90 mV/K respectively. Both theoretical and experimental energy conversion efficiency decreased evidently with the increase in temperature.

High Output Piezo/Triboelectric Hybrid Generator

PubMed Central

Jung, Woo-Suk; Kang, Min-Gyu; Moon, Hi Gyu; Baek, Seung-Hyub; Yoon, Seok-Jin; Wang, Zhong-Lin; Kim, Sang-Woo; Kang, Chong-Yun

2015-01-01

Recently, piezoelectric and triboelectric energy harvesting devices have been developed to convert mechanical energy into electrical energy. Especially, it is well known that triboelectric nanogenerators have a simple structure and a high output voltage. However, whereas nanostructures improve the output of triboelectric generators, its fabrication process is still complicated and unfavorable in term of the large scale and long-time durability of the device. Here, we demonstrate a hybrid generator which does not use nanostructure but generates much higher output power by a small mechanical force and integrates piezoelectric generator into triboelectric generator, derived from the simultaneous use of piezoelectric and triboelectric mechanisms in one press-and-release cycle. This hybrid generator combines high piezoelectric output current and triboelectric output voltage, which produces peak output voltage of ~370 V, current density of ~12 μA·cm−2, and average power density of ~4.44 mW·cm−2. The output power successfully lit up 600 LED bulbs by the application of a 0.2 N mechanical force and it charged a 10 μF capacitor to 10 V in 25 s. Beyond energy harvesting, this work will provide new opportunities for developing a small, built-in power source in self-powered electronics such as mobile electronics. PMID:25791299

Frontiers of controlling energy levels at interfaces

NASA Astrophysics Data System (ADS)

Koch, Norbert

The alignment of electron energy levels at interfaces between semiconductors, dielectrics, and electrodes determines the function and efficiency of all electronic and optoelectronic devices. Reliable guidelines for predicting the level alignment for a given material combination and methods to adjust the intrinsic energy landscape are needed to enable efficient engineering approaches. These are sufficiently understood for established electronic materials, e.g., Si, but for the increasing number of emerging materials, e.g., organic and 2D semiconductors, perovskites, this is work in progress. The intrinsic level alignment and the underlying mechanisms at interfaces between organic and inorganic semiconductors are discussed first. Next, methods to alter the level alignment are introduced, which all base on proper charge density rearrangement at a heterojunction. As interface modification agents we use molecular electron acceptors and donors, as well as molecular photochromic switches that add a dynamic aspect and allow device multifunctionality. For 2D semiconductors surface transfer doping with molecular acceptors/donors transpires as viable method to locally tune the Fermi-level position in the energy gap. The fundamental electronic properties of a prototypical 1D interface between intrinsic and p-doped 2D semiconductor regions are derived from local (scanning probe) and area-averaged (photoemission) spectroscopy experiments. Future research opportunities for attaining unsurpassed interface control through charge density management are discussed.

Negative hydrogen ion production in a helicon plasma source

NASA Astrophysics Data System (ADS)

Santoso, J.; Manoharan, R.; O'Byrne, S.; Corr, C. S.

2015-09-01

In order to develop very high energy (>1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here, we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ˜3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 1014 m-3 to 7 × 1015 m-3 is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.

Kolmogorov-Kraichnan Scaling in the Inverse Energy Cascade of Two-Dimensional Plasma Turbulence

NASA Astrophysics Data System (ADS)

Antar, G. Y.

2003-08-01

Turbulence in plasmas that are magnetically confined, such as tokamaks or linear devices, is two dimensional or at least quasi two dimensional due to the strong magnetic field, which leads to extreme elongation of the fluctuations, if any, in the direction parallel to the magnetic field. These plasmas are also compressible fluid flows obeying the compressible Navier-Stokes equations. This Letter presents the first comprehensive scaling of the structure functions of the density and velocity fields up to 10th order in the PISCES linear plasma device and up to 6th order in the Mega-Ampère Spherical Tokamak (MAST). In the two devices, it is found that the scaling of the turbulent fields is in good agreement with the prediction of the Kolmogorov-Kraichnan theory for two-dimensional turbulence in the energy cascade subrange.

Multimaterial 3D Printing of Graphene-Based Electrodes for Electrochemical Energy Storage Using Thermoresponsive Inks.

PubMed

Rocha, Victoria G; García-Tuñón, Esther; Botas, Cristina; Markoulidis, Foivos; Feilden, Ezra; D'Elia, Eleonora; Ni, Na; Shaffer, Milo; Saiz, Eduardo

2017-10-25

The current lifestyles, increasing population, and limited resources result in energy research being at the forefront of worldwide grand challenges, increasing the demand for sustainable and more efficient energy devices. In this context, additive manufacturing brings the possibility of making electrodes and electrical energy storage devices in any desired three-dimensional (3D) shape and dimensions, while preserving the multifunctional properties of the active materials in terms of surface area and conductivity. This paves the way to optimized and more efficient designs for energy devices. Here, we describe how three-dimensional (3D) printing will allow the fabrication of bespoke devices, with complex geometries, tailored to fit specific requirements and applications, by designing water-based thermoresponsive inks to 3D-print different materials in one step, for example, printing the active material precursor (reduced chemically modified graphene (rCMG)) and the current collector (copper) for supercapacitors or anodes for lithium-ion batteries. The formulation of thermoresponsive inks using Pluronic F127 provides an aqueous-based, robust, flexible, and easily upscalable approach. The devices are designed to provide low resistance interface, enhanced electrical properties, mechanical performance, packing of rCMG, and low active material density while facilitating the postprocessing of the multicomponent 3D-printed structures. The electrode materials are selected to match postprocessing conditions. The reduction of the active material (rCMG) and sintering of the current collector (Cu) take place simultaneously. The electrochemical performance of the rCMG-based self-standing binder-free electrode and the two materials coupled rCMG/Cu printed electrode prove the potential of multimaterial printing in energy applications.

Fabrication and modeling of electrochemical double-layer capacitors using carbon nano-onion electrode structures

NASA Astrophysics Data System (ADS)

Parigi, Fabio

Electrochemical capacitors or ultracapacitors (UCs) that are commercially available today overcome battery limitations in terms of charging time (from tens of minutes to seconds) and limited lifetime (from a few thousand cycles up to more than one million) but still lack specific energy and energy density (2-5% of a lithium ion battery). The latest innovations in carbon nanomaterials, such as carbon nanotubes as an active electrode material for UCs, can provide up to five times as much energy and deliver up to seven times more power than today's activated carbon electrodes. Further improvements in UC power density have been achieved by using state-of-the-art carbon nano-onions (CNOs) for ultracapacitor electrodes. CNO UCs could exhibit up to five times the power density of single-wall CNT UCs and could substantially contribute to reducing the size of an energy storage system as well as the volume and weight, thus improving device performance. This dissertation describes the fabrication of CNO electrodes as part of an UC device, the measurement and analysis of the new electrode's performance as an energy storage component, and development of a new circuit model that accurately describes the CNO UC electrical behavior. The novel model is based on the impedance spectra of CNO UCs and cyclic voltammetry measurements. Further, the model was validated using experimental data and simulation. My original contributions are the fabrication process for reliable and repeatable electrode fabrication and the modeling of a carbon nano-onion ultracapacitor. The carbon nano-onion ultracapacitor model, composed of a resistor, an inductor, a capacitor (RLC), and a constant phase element (CPE), was developed along with a parameter extraction procedure for the benefit of other users. The new model developed, proved to be more accurate than previously reported UC models.

Design of Contact Electrodes for Semiconductor Nanowire Solar Energy Harvesting Devices.

PubMed

Lin, Tzuging; Ramadurgam, Sarath; Yang, Chen

2017-04-12

Transparent, low-resistive contacts are critical for efficient solar energy harvesting devices. It is important to reconsider the material choices and electrode design as devices move from 2D films to 1D nanostructures. In this paper, we study the effectiveness of indium tin oxide (ITO) and metals, such as Ag and Cu, as contacts in 2D and 1D systems. Although ITO has been studied extensively and developed into an effective transparent contact for 2D devices, our results show that effectiveness does not translate to 1D systems. Particularly with consideration of resistance requirement, nanowires with metal shells as contacts enable better absorption within the semiconductor as compared to ITO. Furthermore, there is a strong dependence of contact performance on the semiconductor band gap and diameter of nanowires. We found that metal contacts outperform ITO for nanowire devices, regardless of the sheet resistance constraint, in the regime of diameters less than 100 nm and band-gaps greater than 1 eV. These metal shells optimized for best absorption are significantly thinner than ITO, which enables for the design of devices with high nanowire number density and consequently higher device efficiencies.

Diagnostics of Plasma Propulsion Devices

NASA Astrophysics Data System (ADS)

Cappelli, Mark A.

1998-11-01

Plasma rockets are rapidly emerging as critical technologies in future space flight. These devices take on various forms, ranging from electro-thermal to electromagnetic accelerators, generally categorized by the method in which electrical energy is converted to thrust. As is the case in many plasma devices, non-intrusive optical (emission, or laser-based) diagnostics is an essential element in the characterization of these plasma sources, as access to the discharges in these plasma engines is often limited. Furthermore, laser-based diagnostics offer additional benefits, including improved spatial resolution, and can provide state-specific measurements of species densities, velocities and energy distributions. In recent years, we have developed and applied a variety of emission and laser-based diagnostics strategies to the characterization of arcjet plasma and closed-drift xenon Hall plasma accelerators. Both of these types of plasma propulsion devices are of immediate interest to the space propulsion community, and are under varying stages of development. Arcjet thrusters have unique properties, with strong plasma density, temperature and velocity gradients, which enhance the coupling between the gasdynamic and plasma physics. Closed-drift Hall plasma thrusters are low density electrostatic devices that are inherently turbulent, and exhibit varying degrees of anomalous cross-field electron transport. Our most extensive, collective effort has been to apply laser-induced fluorescence, Doppler-free laser absorption, and Raman scattering to the characterization of hydrogen and helium arcjet flows. Detailed measurements of velocity, temperatures, and electron densities are compared to the results of magneto-hydrodynamic flowfield simulations. The results show that while the simulations capture many aspects of the flow, there are still some unresolved discrepancies. The database established for Hall thrusters is less extensive, as the laser absorption spectroscopy of xenon is somewhat more complicated due to the hyperfine and isotopic structure of electronic transitions. With an understanding of the spectroscopic absorption lineshape for two select transitions in neutral and ionized xenon, we have successfully mapped out the neutral and singly ionized xenon velocities in the acceleration zone of Hall thrusters. These results indicate that the acceleration zone in a short-channel thruster is outside of the device, consistent with the measurements of plasma potential using more conventional Langmuir electrostatic probes. The spectroscopic data has also been used to identify limitations in ground-test facilities.

Oxidation state and interfacial effects on oxygen vacancies in tantalum pentoxide

DOE PAGES

Bondi, Robert J.; Marinella, Matthew J.

2015-02-28

First-principles density-functional theory (DFT) calculations are used to study the atomistic structure, structural energetics, and electron density near the O monovacancy (V O n; n=0,1+,2+) in both bulk, amorphous tantalum pentoxide (a-Ta 2O 5) and also at vacuum and metallic Ta interfaces. We calculate multivariate vacancy formation energies to evaluate stability as a function of oxidation state, distance from interface plane, and Fermi energy. V O n of all oxidation states preferentially segregate at both Ta and vacuum interfaces, where the metallic interface exhibits global formation energy minima. In a-Ta 2O 5, V O 0 are characterized by structural contractionmore » and electron density localization, while V O 2+ promote structural expansion and are depleted of electron density. In contrast, interfacial V O 0 and V O 2+ show nearly indistinguishable ionic and electronic signatures indicative of a reduced V O center. Interfacial V O 2+ extract electron density from metallic Ta indicating V O 2+ is spontaneously reduced at the expense of the metal. This oxidation/reduction behavior suggests careful selection and processing of both oxide layer and metal electrodes for engineering memristor device operation.« less

Band Gap Engineering of Boron Nitride by Graphene and Its Application as Positive Electrode Material in Asymmetric Supercapacitor Device.

PubMed

Saha, Sanjit; Jana, Milan; Khanra, Partha; Samanta, Pranab; Koo, Hyeyoung; Murmu, Naresh Chandra; Kuila, Tapas

2015-07-08

Nanostructured hexagonal boron nitride (h-BN)/reduced graphene oxide (RGO) composite is prepared by insertion of h-BN into the graphene oxide through hydrothermal reaction. Formation of the super lattice is confirmed by the existence of two separate UV-visible absorption edges corresponding to two different band gaps. The composite materials show enhanced electrical conductivity as compared to the bulk h-BN. A high specific capacitance of ∼824 F g(-1) is achieved at a current density of 4 A g(-1) for the composite in three-electrode electrochemical measurement. The potential window of the composite electrode lies in the range from -0.1 to 0.5 V in 6 M aqueous KOH electrolyte. The operating voltage is increased to 1.4 V in asymmetric supercapacitor (ASC) device where the thermally reduced graphene oxide is used as the negative electrode and the h-BN/RGO composite as the positive electrode. The ASC exhibits a specific capacitance of 145.7 F g(-1) at a current density of 6 A g(-1) and high energy density of 39.6 W h kg(-1) corresponding to a large power density of ∼4200 W kg(-1). Therefore, a facile hydrothermal route is demonstrated for the first time to utilize h-BN-based composite materials as energy storage electrode materials for supercapacitor applications.

Stable operating regime for traveling wave devices

DOEpatents

Carlsten, Bruce E.

2000-01-01

Autophase stability is provided for a traveling wave device (TWD) electron beam for amplifying an RF electromagnetic wave in walls defining a waveguide for said electromagnetic wave. An off-axis electron beam is generated at a selected energy and has an energy noise inherently arising from electron gun. The off-axis electron beam is introduced into the waveguide. The off-axis electron beam is introduced into the waveguide at a second radius. The waveguide structure is designed to obtain a selected detuning of the electron beam. The off-axis electron beam has a velocity and the second radius to place the electron beam at a selected distance from the walls defining the waveguide, wherein changes in a density of the electron beam due to the RF electromagnetic wave are independent of the energy of the electron beam to provide a concomitant stable operating regime relative to the energy noise.

The need for control of magnetic parameters for energy efficient performance of magnetic tunnel junctions

NASA Astrophysics Data System (ADS)

Farhat, I. A. H.; Gale, E.; Alpha, C.; Isakovic, A. F.

2017-07-01

Optimizing energy performance of Magnetic Tunnel Junctions (MTJs) is the key for embedding Spin Transfer Torque-Random Access Memory (STT-RAM) in low power circuits. Due to the complex interdependencies of the parameters and variables of the device operating energy, it is important to analyse parameters with most effective control of MTJ power. The impact of threshold current density, Jco , on the energy and the impact of HK on Jco are studied analytically, following the expressions that stem from Landau-Lifshitz-Gilbert-Slonczewski (LLGS-STT) model. In addition, the impact of other magnetic material parameters, such as Ms , and geometric parameters such as tfree and λ is discussed. Device modelling study was conducted to analyse the impact at the circuit level. Nano-magnetism simulation based on NMAGTM package was conducted to analyse the impact of controlling HK on the switching dynamics of the film.

Noncovalent Pi-Pi Stacking at the Carbon-Electrolyte Interface: Controlling the Voltage Window of Electrochemical Supercapacitors.

PubMed

Li, Mengya; Westover, Andrew S; Carter, Rachel; Oakes, Landon; Muralidharan, Nitin; Boire, Timothy C; Sung, Hak-Joon; Pint, Cary L

2016-08-03

A key parameter in the operation of an electrochemical double-layer capacitor is the voltage window, which dictates the device energy density and power density. Here we demonstrate experimental evidence that π-π stacking at a carbon-ionic liquid interface can modify the operation voltage of a supercapacitor device by up to 30%, and this can be recovered by steric hindrance at the electrode-electrolyte interface introduced by poly(ethylene oxide) polymer electrolyte additives. This observation is supported by Raman spectroscopy, electrochemical impedance spectroscopy, and differential scanning calorimetry that each independently elucidates the signature of π-π stacking between imidazole groups in the ionic liquid and the carbon surface and the role this plays to lower the energy barrier for charge transfer at the electrode-electrolyte interface. This effect is further observed universally across two separate ionic liquid electrolyte systems and is validated by control experiments showing an invariant electrochemical window in the absence of a carbon-ionic liquid electrode-electrolyte interface. As interfacial or noncovalent interactions are usually neglected in the mechanistic picture of double-layer capacitors, this work highlights the importance of understanding chemical properties at supercapacitor interfaces to engineer voltage and energy capability.

Colloidal Engineering for Infrared-Bandgap Solution-Processed Quantum Dot Solar Cells

NASA Astrophysics Data System (ADS)

Kiani, Amirreza

Ever-increasing global energy demand and a diminishing fossil fuel supply have prompted the development of technologies for sustainable energy production. Solar photovoltaic (PV) devices have huge potential for energy harvesting and production since the sun delivers more energy to the earth in one hour than the global population consumes in one year. The solar cell industry is now dominated by silicon PV devices. The cost of silicon modules has decreased substantially over the past two decades and the number of installed silicon PV devices has increased dramatically. There remains a need for emerging solar technologies that can harvest the untapped portion of the solar spectrum and can be integrated on flexible and curved surfaces. This thesis focuses on colloidal quantum dot (CQD) PV devices. CQDs are nanoparticles fabricated using a low-temperature and cost-effective solution technique. These materials suffer from a high density of surface traps derived from the large surface-to-volume ratio of CQD nanoparticles, combined with limited carrier mobility. These result in a short carrier diffusion length, a main limiting factor in CQD solar cell performance. This thesis seeks to address the poor diffusion length in lead sulfide (PbS) CQD films and pave the way for new applications for CQD PV devices in infrared solar harvesting and waste heat recovery. A two-fold reduction in surface trap density is demonstrated using molecular halide treatment. Iodine molecules introduced prior to the film formation replace the otherwise unpassivated surface sulfur atoms. This results in a 35% increase in the diffusion length and enables charge extraction over thicker active layer leading to the world's most efficient CQD PV devices from June 2015 to July 2016 with the certified power conversion efficiency of 9.9%. This represents a 30% increase over the best-certified PCE (7.5%) prior to this thesis. The colloidal engineering highlighted herein enables infrared (IR) solar harvesting for the first time. Addition of short bromothiol ligands during the synthesis significantly reduces the agglomeration of 1 eV bandgap CQDs and maintains efficient charge extraction into the selective electrodes. The devices can augment the performance of the best silicon cells by 7 power points where 0.8 additive power points are demonstrated experimentally. A tailored solution exchanged process developed for 1 eV bandgap CQDs results in air-stable IR PV devices with improved manufacturability. The process utilizes a tailored combination of lead iodide (PbI2) and ammonium acetate for the solution exchange and hexylamine + MEK as the final solvent to yield solar thick films with the filtered (1100 nm and beyond) performance of 0.4%. This thesis pushes the limit of CQD device applications to waste heat recovery. I demonstrate successful harvesting of low energy photons emitted from a hot object by designing and developing the first solution-processed thermophotovoltaic devices. These devices are comprised of 0.7 eV bandgap CQDs that successfully harvest photons emitted from an 800°C heat source.

Scalable synthesis of hierarchically structured carbon nanotube-graphene fibres for capacitive energy storage

NASA Astrophysics Data System (ADS)

Yu, Dingshan; Goh, Kunli; Wang, Hong; Wei, Li; Jiang, Wenchao; Zhang, Qiang; Dai, Liming; Chen, Yuan

2014-07-01

Micro-supercapacitors are promising energy storage devices that can complement or even replace batteries in miniaturized portable electronics and microelectromechanical systems. Their main limitation, however, is the low volumetric energy density when compared with batteries. Here, we describe a hierarchically structured carbon microfibre made of an interconnected network of aligned single-walled carbon nanotubes with interposed nitrogen-doped reduced graphene oxide sheets. The nanomaterials form mesoporous structures of large specific surface area (396 m2 g-1) and high electrical conductivity (102 S cm-1). We develop a scalable method to continuously produce the fibres using a silica capillary column functioning as a hydrothermal microreactor. The resultant fibres show a specific volumetric capacity as high as 305 F cm-3 in sulphuric acid (measured at 73.5 mA cm-3 in a three-electrode cell) or 300 F cm-3 in polyvinyl alcohol (PVA)/H3PO4 electrolyte (measured at 26.7 mA cm-3 in a two-electrode cell). A full micro-supercapacitor with PVA/H3PO4 gel electrolyte, free from binder, current collector and separator, has a volumetric energy density of ~6.3 mWh cm-3 (a value comparable to that of 4 V-500 µAh thin-film lithium batteries) while maintaining a power density more than two orders of magnitude higher than that of batteries, as well as a long cycle life. To demonstrate that our fibre-based, all-solid-state micro-supercapacitors can be easily integrated into miniaturized flexible devices, we use them to power an ultraviolet photodetector and a light-emitting diode.

Thermoelectric energy conversion with solid electrolytes

NASA Astrophysics Data System (ADS)

Cole, T.

1983-09-01

The alkali metal thermoelectric converter (AMTEC) is a device for the direct conversion of heat to electrical energy. The sodium ion conductor beta-double prime-alumina is used to form a high-temperature regenerative concentration cell for elemental sodium. An AMTEC of mature design should have an efficiency of 20 to 40 percent, a power density of 0.5 kilowatt per kilogram or more, no moving parts, low maintenance requirements, high durability, and efficiency independent of size. It should be usable with high-temperature combustion, nuclear, or solar heat sources. Experiments have demonstrated the feasibility of the AMTEC and confirmed the theoretical analysis of the device. A wide range of applications from aerospace power to utility power plants appears possible.

Thermoelectric energy conversion with solid electrolytes.

PubMed

Cole, T

1983-09-02

The alkali metal thermoelectric converter (AMTEC) is a device for the direct conversion of heat to electrical energy. The sodium ion conductor beta"- alumina is used to form a high-temperature regenerative concentration cell for elemental sodium. An AMTEC of mature design should have an efficiency of 20 to 40 percent, a power density of 0.5 kilowatt per kilogram or more, no moving parts, low maintenance requirements, high durability, and efficiency independent of size. It should be usable with high-temperature combustion, nuclear, or solar heat sources. Experiments have demonstrated the feasibility of the AMTEC and confirmed the theoretical analysis of the device. A wide range of applications from aerospace power to utility power plants appears possible.

Directly Grown Nanostructured Electrodes for High Volumetric Energy Density Binder-Free Hybrid Supercapacitors: A Case Study of CNTs//Li4Ti5O12

NASA Astrophysics Data System (ADS)

Zuo, Wenhua; Wang, Chong; Li, Yuanyuan; Liu, Jinping

2015-01-01

Hybrid supercapacitor (HSC), which typically consists of a Li-ion battery electrode and an electric double-layer supercapacitor electrode, has been extensively investigated for large-scale applications such as hybrid electric vehicles, etc. Its application potential for thin-film downsized energy storage systems that always prefer high volumetric energy/power densities, however, has not yet been explored. Herein, as a case study, we develop an entirely binder-free HSC by using multiwalled carbon nanotube (MWCNT) network film as the cathode and Li4Ti5O12 (LTO) nanowire array as the anode and study the volumetric energy storage capability. Both the electrode materials are grown directly on carbon cloth current collector, ensuring robust mechanical/electrical contacts and flexibility. Our 3 V HSC device exhibits maximum volumetric energy density of ~4.38 mWh cm-3, much superior to those of previous supercapacitors based on thin-film electrodes fabricated directly on carbon cloth and even comparable to the commercial thin-film lithium battery. It also has volumetric power densities comparable to that of the commercial 5.5 V/100 mF supercapacitor (can be operated within 3 s) and has excellent cycling stability (~92% retention after 3000 cycles). The concept of utilizing binder-free electrodes to construct HSC for thin-film energy storage may be readily extended to other HSC electrode systems.

Space Environment Effects on Flexible, Low-Voltage Organic Thin-Film Transistors.

PubMed

Basiricò, Laura; Basile, Alberto Francesco; Cosseddu, Piero; Gerardin, Simone; Cramer, Tobias; Bagatin, Marta; Ciavatti, Andrea; Paccagnella, Alessandro; Bonfiglio, Annalisa; Fraboni, Beatrice

2017-10-11

Organic electronic devices fabricated on flexible substrates are promising candidates for applications in environments where flexible, lightweight, and radiation hard materials are required. In this work, device parameters such as threshold voltage, charge mobility, and trap density of 13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene)-based organic thin-film transistors (OTFTs) have been monitored for performing electrical measurements before and after irradiation by high-energy protons. The observed reduction of charge carrier mobility following irradiation can be only partially ascribed to the increased trap density. Indeed, we used other techniques to identify additional effects induced by proton irradiation in such devices. Atomic force microscopy reveals morphological defects occurring in the organic dielectric layer induced by the impinging protons, which, in turn, induce a strain on the TIPS-pentacene crystallites lying above. The effects of this strain are investigated by density functional theory simulations of two model structures, which describe the TIPS-pentacene crystalline films at equilibrium and under strain. The two different density of states distributions in the valence band have been correlated with the photocurrent spectra acquired before and after proton irradiation. We conclude that the degradation of the dielectric layer and the organic semiconductor sensitivity to strain are the two main phenomena responsible for the reduction of OTFT mobility after proton irradiation.

Radiation source

DOEpatents

Thode, Lester E.

1981-01-01

A device and method for relativistic electron beam heating of a high-density plasma in a small localized region. A relativistic electron beam generator or accelerator produces a high-voltage electron beam which propagates along a vacuum drift tube and is modulated to initiate electron bunching within the beam. The beam is then directed through a low-density gas chamber which provides isolation between the vacuum modulator and the relativistic electron beam target. The relativistic beam is then applied to a high-density target plasma which typically comprises DT, DD, or similar thermonuclear gas at a density of 10.sup.17 to 10.sup.20 electrons per cubic centimeter. The target gas is ionized prior to application of the relativistic electron beam by means of a laser or other preionization source to form a plasma. Utilizing a relativistic electron beam with an individual particle energy exceeding 3 MeV, classical scattering by relativistic electrons passing through isolation foils is negligible. As a result, relativistic streaming instabilities are initiated within the high-density target plasma causing the relativistic electron beam to efficiently deposit its energy into a small localized region of the high-density plasma target.

High-energy side-peak emission of exciton-polariton condensates in high density regime

PubMed Central

Horikiri, Tomoyuki; Yamaguchi, Makoto; Kamide, Kenji; Matsuo, Yasuhiro; Byrnes, Tim; Ishida, Natsuko; Löffler, Andreas; Höfling, Sven; Shikano, Yutaka; Ogawa, Tetsuo; Forchel, Alfred; Yamamoto, Yoshihisa

2016-01-01

In a standard semiconductor laser, electrons and holes recombine via stimulated emission to emit coherent light, in a process that is far from thermal equilibrium. Exciton-polariton condensates–sharing the same basic device structure as a semiconductor laser, consisting of quantum wells coupled to a microcavity–have been investigated primarily at densities far below the Mott density for signatures of Bose-Einstein condensation. At high densities approaching the Mott density, exciton-polariton condensates are generally thought to revert to a standard semiconductor laser, with the loss of strong coupling. Here, we report the observation of a photoluminescence sideband at high densities that cannot be accounted for by conventional semiconductor lasing. This also differs from an upper-polariton peak by the observation of the excitation power dependence in the peak-energy separation. Our interpretation as a persistent coherent electron-hole-photon coupling captures several features of this sideband, although a complete understanding of the experimental data is lacking. A full understanding of the observations should lead to a development in non-equilibrium many-body physics. PMID:27193700

An oxygen-independent and membrane-less glucose biobattery/supercapacitor hybrid device.

PubMed

Xiao, Xinxin; Conghaile, Peter Ó; Leech, Dónal; Ludwig, Roland; Magner, Edmond

2017-12-15

Enzymatic biofuel cells can generate electricity directly from the chemical energy of biofuels in physiological fluids, but their power density is significantly limited by the performance of the cathode which is based on oxygen reduction for in vivo applications. An oxygen-independent and membrane-less glucose biobattery was prepared that consists of a dealloyed nanoporous gold (NPG) supported glucose dehydrogenase (GDH) bioanode, immobilised with the assistance of conductive polymer/Os redox polymer composites, and a solid-state NPG/MnO 2 cathode. In a solution containing 10mM glucose, a maximum power density of 2.3µWcm -2 at 0.21V and an open circuit voltage (OCV) of 0.49V were registered as a biobattery. The potential of the discharged MnO 2 could be recovered, enabling a proof-of-concept biobattery/supercapacitor hybrid device. The resulting device exhibited a stable performance for 50 cycles of self-recovery and galvanostatic discharge as a supercapacitor at 0.1mAcm -2 over a period of 25h. The device could be discharged at current densities up to 2mAcm -2 supplying a maximum instantaneous power density of 676 μW cm -2 , which is 294 times higher than that from the biobattery alone. A mechanism for the recovery of the potential of the cathode, analogous to that of RuO 2 (Electrochim. Acta 42(23), 3541-3552) is described. Copyright © 2017 Elsevier B.V. All rights reserved.

Tailorable and Wearable Textile Devices for Solar Energy Harvesting and Simultaneous Storage.

PubMed

Chai, Zhisheng; Zhang, Nannan; Sun, Peng; Huang, Yi; Zhao, Chuanxi; Fan, Hong Jin; Fan, Xing; Mai, Wenjie

2016-10-05

The pursuit of harmonic combination of technology and fashion intrinsically points to the development of smart garments. Herein, we present an all-solid tailorable energy textile possessing integrated function of simultaneous solar energy harvesting and storage, and we call it tailorable textile device. Our technique makes it possible to tailor the multifunctional textile into any designed shape without impairing its performance and produce stylish smart energy garments for wearable self-powering system with enhanced user experience and more room for fashion design. The "threads" (fiber electrodes) featuring tailorability and knittability can be large-scale fabricated and then woven into energy textiles. The fiber supercapacitor with merits of tailorability, ultrafast charging capability, and ultrahigh bending-resistance is used as the energy storage module, while an all-solid dye-sensitized solar cell textile is used as the solar energy harvesting module. Our textile sample can be fully charged to 1.2 V in 17 s by self-harvesting solar energy and fully discharged in 78 s at a discharge current density of 0.1 mA.

Scalable fabrication of high-power graphene micro-supercapacitors for flexible and on-chip energy storage

NASA Astrophysics Data System (ADS)

El-Kady, Maher F.; Kaner, Richard B.

2013-02-01

The rapid development of miniaturized electronic devices has increased the demand for compact on-chip energy storage. Microscale supercapacitors have great potential to complement or replace batteries and electrolytic capacitors in a variety of applications. However, conventional micro-fabrication techniques have proven to be cumbersome in building cost-effective micro-devices, thus limiting their widespread application. Here we demonstrate a scalable fabrication of graphene micro-supercapacitors over large areas by direct laser writing on graphite oxide films using a standard LightScribe DVD burner. More than 100 micro-supercapacitors can be produced on a single disc in 30 min or less. The devices are built on flexible substrates for flexible electronics and on-chip uses that can be integrated with MEMS or CMOS in a single chip. Remarkably, miniaturizing the devices to the microscale results in enhanced charge-storage capacity and rate capability. These micro-supercapacitors demonstrate a power density of ~200 W cm-3, which is among the highest values achieved for any supercapacitor.

A Foldable Lithium-Sulfur Battery.

PubMed

Li, Lu; Wu, Zi Ping; Sun, Hao; Chen, Deming; Gao, Jian; Suresh, Shravan; Chow, Philippe; Singh, Chandra Veer; Koratkar, Nikhil

2015-11-24

The next generation of deformable and shape-conformable electronics devices will need to be powered by batteries that are not only flexible but also foldable. Here we report a foldable lithium-sulfur (Li-S) rechargeable battery, with the highest areal capacity (∼3 mAh cm(-2)) reported to date among all types of foldable energy-storage devices. The key to this result lies in the use of fully foldable and superelastic carbon nanotube current-collector films and impregnation of the active materials (S and Li) into the current-collectors in a checkerboard pattern, enabling the battery to be folded along two mutually orthogonal directions. The carbon nanotube films also serve as the sulfur entrapment layer in the Li-S battery. The foldable battery showed <12% loss in specific capacity over 100 continuous folding and unfolding cycles. Such shape-conformable Li-S batteries with significantly greater energy density than traditional lithium-ion batteries could power the flexible and foldable devices of the future including laptops, cell phones, tablet computers, surgical tools, and implantable biomedical devices.

Ultrathin Coaxial Fiber Supercapacitors Achieving High Energy and Power Densities.

PubMed

Shen, Caiwei; Xie, Yingxi; Sanghadasa, Mohan; Tang, Yong; Lu, Longsheng; Lin, Liwei

2017-11-15

Fiber-based supercapacitors have attracted significant interests because of their potential applications in wearable electronics. Although much progress has been made in recent years, the energy and power densities, mechanical strength, and flexibility of such devices are still in need of improvement for practical applications. Here, we demonstrate an ultrathin microcoaxial fiber supercapacitor (μCFSC) with high energy and power densities (2.7 mW h/cm 3 and 13 W/cm 3 ), as well as excellent mechanical properties. The prototype with the smallest reported overall diameter (∼13 μm) is fabricated by successive coating of functional layers onto a single micro-carbon-fiber via a scalable process. Combining the simulation results via the electrochemical model, we attribute the high performance to the well-controlled thin coatings that make full use of the electrode materials and minimize the ion transport path between electrodes. Moreover, the μCFSC features high bending flexibility and large tensile strength (more than 1 GPa), which make it promising as a building block for various flexible energy storage applications.

Physical-Mechanisms Based Reliability Analysis For Emerging Technologies

DTIC Science & Technology

2017-05-05

irradiation is great- ly enhanced by biasing the...devices during irradiation and/or applying high field stress be- fore irradiation . The resulting defect energy distributions were evaluated after... irradiation and/or high field stress via low-frequency noise measurements. Significant increases were observed in acceptor densities for defects with

Heating Efficiency of Beat Wave Excitation in a Density Gradient,

DTIC Science & Technology

1988-02-01

and Technology, January 1988. PPG-1124 񓟣 Research Highlights in The Pisces Program," R.V. Conn, et al, January 1988. PPG-1125 "Magnetic Fusion ... Energy , vol. 5. Technical Assessement of Critical Issues in the Steady State Operation of Fusion Confinement Devices," D. M. Goebel, Assessment Chairman

Design of State-of-the-art Flow Cells for Energy Applications

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yang, Ping

The worldwide energy demand is increasing every day and it necessitates rational and efficient usage of renewable energy. Undoubtedly, utilization of renewable energy can address various environmental challenges. However, all current renewable energy resources (wind, solar, and hydroelectric power) are intermittent and fluctuating in their nature that raises an important question of introducing effective energy storage solutions. Utilization of redox flow cells (RFCs) has recently been recognized as a viable technology for large-scale energy storage and, hence, is well suited for integrating renewable energy and balancing electricity grids. In brief, RFC is an electrochemical storage device where energy is storedmore » in chemical bonds, similar to a battery, but with reactants external to the cell. The state-of-the-art in flow cell technology uses an aqueous acidic electrolyte and simple metal redox couples. Thus, there is an urgent call to develop efficient (high-energy density) and low-cost RFCs to meet the efflorescent energy storage demands. To address the first challenge of achieving high-energy density, we plan to design and further modify complexes composed of bifunctional multidentate ligands and specific metal centers, capable of storing as many electrons as possible. In order to address the second challenge of reducing cost of the RFCs, we plan to use iron (Fe) metal as it regularly occupies multiple oxidation states and is the second most abundant metal in the earth’s crust that makes it an ideal metal for improved energy densities, higher potentials, and numbers of electrons per molecule while maintaining potential cost competitiveness. Density functional theory calculations considering solvation effects will be performed to yield accurate predictions of redox potentials.« less

Limiting factors for carbon based chemical double layer capacitors

NASA Technical Reports Server (NTRS)

Rose, M. Frank; Johnson, C.; Owens, T.; Stevens, B.

1993-01-01

The Chemical Double Layer (CDL) capacitor improves energy storage density dramatically when compared with conventional electrolytic capacitors. When compared to batteries, the CDL Capacitor is much less energy dense; however, the power density is orders of magnitude better. As a result, CDL-battery combinations present an interesting pulse power system with many potential applications. Due to the nature of the CDL it is inherently a low voltage device. The applications of the CDL can be tailored to auxiliary energy and burst mode storages which require fast charge/discharge cycles. Typical of the applications envisioned are power system backup, directed energy weapons concepts, electric automobiles, and electric actuators. In this paper, we will discuss some of the general characteristics of carbon-based CDL technology describing the structure, performance parameters, and methods of construction. Further, analytical and experimental results which define the state of the art are presented and described in terms of impact on applications.

Mechanical Computing Redux: Limitations at the Nanoscale

NASA Astrophysics Data System (ADS)

Liu, Tsu-Jae King

2014-03-01

Technology solutions for overcoming the energy efficiency limits of nanoscale complementary metal oxide semiconductor (CMOS) technology ultimately will be needed in order to address the growing issue of integrated-circuit chip power density. Off-state leakage current sets a fundamental lower limit in energy per operation for any voltage-level-based digital logic implemented with transistors (CMOS and beyond), which leads to practical limits for device density (i.e. cost) and operating frequency (i.e. system performance). Mechanical switches have zero off-state leakag and hence can overcome this fundamental limit. Contact adhesive force sets a lower limit for the switching energy of a mechanical switch, however, and also directly impacts its performance. This paper will review recent progress toward the development of nano-electro-mechanical relay technology and discuss remaining challenges for realizing the promise of mechanical computing for ultra-low-power computing. Supported by the Center for Energy Efficient Electronics Science (NSF Award 0939514).

Hot-electron transfer in quantum-dot heterojunction films.

PubMed

Grimaldi, Gianluca; Crisp, Ryan W; Ten Brinck, Stephanie; Zapata, Felipe; van Ouwendorp, Michiko; Renaud, Nicolas; Kirkwood, Nicholas; Evers, Wiel H; Kinge, Sachin; Infante, Ivan; Siebbeles, Laurens D A; Houtepen, Arjan J

2018-06-13

Thermalization losses limit the photon-to-power conversion of solar cells at the high-energy side of the solar spectrum, as electrons quickly lose their energy relaxing to the band edge. Hot-electron transfer could reduce these losses. Here, we demonstrate fast and efficient hot-electron transfer between lead selenide and cadmium selenide quantum dots assembled in a quantum-dot heterojunction solid. In this system, the energy structure of the absorber material and of the electron extracting material can be easily tuned via a variation of quantum-dot size, allowing us to tailor the energetics of the transfer process for device applications. The efficiency of the transfer process increases with excitation energy as a result of the more favorable competition between hot-electron transfer and electron cooling. The experimental picture is supported by time-domain density functional theory calculations, showing that electron density is transferred from lead selenide to cadmium selenide quantum dots on the sub-picosecond timescale.

Understanding Fundamentals and Reaction Mechanisms of Electrode Materials for Na-Ion Batteries.

PubMed

Yu, Linghui; Wang, Luyuan Paul; Liao, Hanbin; Wang, Jingxian; Feng, Zhenxing; Lev, Ovadia; Loo, Joachim S C; Sougrati, Moulay Tahar; Xu, Zhichuan J

2018-04-01

Development of efficient, affordable, and sustainable energy storage technologies has become an area of interest due to the worsening environmental issues and rising technological dependence on Li-ion batteries. Na-ion batteries (NIBs) have been receiving intensive research efforts during the last few years. Owing to their potentially low cost and relatively high energy density, NIBs are promising energy storage devices, especially for stationary applications. A fundamental understanding of electrode properties during electrochemical reactions is important for the development of low cost, high-energy density, and long shelf life NIBs. This Review aims to summarize and discuss reaction mechanisms of the major types of NIB electrode materials reported. By appreciating how the material works and the fundamental flaws it possesses, it is hoped that this Review will assist readers in coming up with innovative solutions for designing better materials for NIBs. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Organic semiconductor density of states controls the energy level alignment at electrode interfaces

PubMed Central

Oehzelt, Martin; Koch, Norbert; Heimel, Georg

2014-01-01

Minimizing charge carrier injection barriers and extraction losses at interfaces between organic semiconductors and metallic electrodes is critical for optimizing the performance of organic (opto-) electronic devices. Here, we implement a detailed electrostatic model, capable of reproducing the alignment between the electrode Fermi energy and the transport states in the organic semiconductor both qualitatively and quantitatively. Covering the full phenomenological range of interfacial energy level alignment regimes within a single, consistent framework and continuously connecting the limiting cases described by previously proposed models allows us to resolve conflicting views in the literature. Our results highlight the density of states in the organic semiconductor as a key factor. Its shape and, in particular, the energy distribution of electronic states tailing into the fundamental gap is found to determine both the minimum value of practically achievable injection barriers as well as their spatial profile, ranging from abrupt interface dipoles to extended band-bending regions. PMID:24938867

A Bamboo-Inspired Nanostructure Design for Flexible, Foldable, and Twistable Energy Storage Devices.

PubMed

Sun, Yongming; Sills, Ryan B; Hu, Xianluo; Seh, Zhi Wei; Xiao, Xu; Xu, Henghui; Luo, Wei; Jin, Huanyu; Xin, Ying; Li, Tianqi; Zhang, Zhaoliang; Zhou, Jun; Cai, Wei; Huang, Yunhui; Cui, Yi

2015-06-10

Flexible energy storage devices are critical components for emerging flexible electronics. Electrode design is key in the development of all-solid-state supercapacitors with superior electrochemical performances and mechanical durability. Herein, we propose a bamboo-like graphitic carbon nanofiber with a well-balanced macro-, meso-, and microporosity, enabling excellent mechanical flexibility, foldability, and electrochemical performances. Our design is inspired by the structure of bamboos, where a periodic distribution of interior holes along the length and graded pore structure at the cross section not only enhance their stability under different mechanical deformation conditions but also provide a high surface area accessible to the electrolyte and low ion-transport resistance. The prepared nanofiber network electrode recovers its initial state easily after 3-folded manipulation. The mechanically robust membrane is explored as a free-standing electrode for a flexible all-solid-state supercapacitor. Without the need for extra support, the volumetric energy and power densities based on the whole device are greatly improved compared to the state-of-the-art devices. Even under continuous dynamic operations of forceful bending (90°) and twisting (180°), the as-designed device still exhibits stable electrochemical performances with 100% capacitance retention. Such a unique supercapacitor holds great promise for high-performance flexible electronics.

A bamboo-inspired nanostructure design for flexible foldable and twistable energy storage devices

DOE PAGES

Sun, Yongming; Sills, Ryan B; Hu, Xianluo; ...

2015-05-26

Flexible energy storage devices are critical components for emerging flexible electronics. Electrode design is key in the development of all-solid-state supercapacitors with superior electrochemical performances and mechanical durability. We propose a bamboo-like graphitic carbon nanofiber with a well-balanced macro-, meso-, and microporosity, enabling excellent mechanical flexibility, foldability, and electrochemical performances. Our design is inspired by the structure of bamboos, where a periodic distribution of interior holes along the length and graded pore structure at the cross section not only enhance their stability under different mechanical deformation conditions but also provide a high surface area accessible to the electrolyte and lowmore » ion-transport resistance. The prepared nanofiber network electrode recovers its initial state easily after 3-folded manipulation. The mechanically robust membrane is explored as a free-standing electrode for a flexible all-solid-state supercapacitor. Without the need for extra support, the volumetric energy and power densities based on the whole device are greatly improved compared to the state-of-the-art devices. Furthermore, even under continuous dynamic operations of forceful bending (90°) and twisting (180°), the as-designed device still exhibits stable electrochemical performances with 100% capacitance retention. As a result, such a unique supercapacitor holds great promise for high-performance flexible electronics.« less

Density-functional study on the dopant-segregation mechanism: Chemical potential dependence of dopant-defect complex at Si/SiO2 interface

NASA Astrophysics Data System (ADS)

Kawai, Hiroki; Nakasaki, Yasushi; Kanemura, Takahisa; Ishihara, Takamitsu

2018-04-01

Dopant segregation at Si/SiO2 interface has been a serious problem in silicon device technology. This paper reports a comprehensive density-functional study on the segregation mechanisms of boron, phosphorous, and arsenic at the Si/SiO2 interface. We found that three kinds of interfacial defects, namely, interstitial oxygen, oxygen vacancy, and silicon vacancy with two oxygen atoms, are stable in the possible chemical potential range. Thus, we consider these defects as trap sites for the dopants. For these defects, the dopant segregation energies, the electrical activities of the trapped dopants, and the kinetic energy barriers of the trapping/detrapping processes are calculated. As a result, trapping at the interstitial oxygen site is indicated to be the most plausible mechanism of the dopant segregation. The interstitial oxygen works as a major trap site since it has a high areal density at the Si/SiO2 interface due to the low formation energy.

Fabrication of Nb/Pb structures through ultrashort pulsed laser deposition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gontad, Francisco; Lorusso, Antonella, E-mail: antonella.lorusso@le.infn.it; Perrone, Alessio

This work reports the fabrication of Nb/Pb structures with an application as photocathode devices. The use of relatively low energy densities for the ablation of Nb with ultrashort pulses favors the reduction of droplets during the growth of the film. However, the use of laser fluences in this ablation regime results in a consequent reduction in the average deposition rate. On the other hand, despite the low deposition rate, the films present a superior adherence to the substrate and an excellent coverage of the irregular substrate surface, avoiding the appearance of voids or discontinuities on the film surface. Moreover, themore » low energy densities used for the ablation favor the growth of nanocrystalline films with a similar crystalline structure to the bulk material. Therefore, the use of low ablation energy densities with ultrashort pulses for the deposition of the Nb thin films allows the growth of very adherent and nanocrystalline films with adequate properties for the fabrication of Nb/Pb structures to be included in superconducting radiofrequency cavities.« less

Coupled modeling of the competitive gettering of transition metals and impact on performance of lifetime sensitive devices

NASA Astrophysics Data System (ADS)

Yazdani, Armin; Chen, Renyu; Dunham, Scott T.

2017-03-01

This work models competitive gettering of metals (Cu, Ni, Fe, Mo, and W) by boron, phosphorus, and dislocation loops, and connects those results directly to device performance. Density functional theory calculations were first performed to determine the binding energies of metals to the gettering sites, and based on that, continuum models were developed to model the redistribution and trapping of the metals. Our models found that Fe is most strongly trapped by the dislocation loops while Cu and Ni are most strongly trapped by the P4V clusters formed in high phosphorus concentrations. In addition, it is found that none of the mentioned gettering sites are effective in gettering Mo and W. The calculated metal redistribution along with the associated capture cross sections and trap energy levels are passed to device simulation via the recombination models to calculate carrier lifetime and the resulting device performance. Thereby, a comprehensive and predictive TCAD framework is developed to optimize the processing conditions to maximize performance of lifetime sensitive devices.

Applied magnetism: A supply-driven materials challenge

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rios, Orlando; McCall, Scott K.

Permanent magnets are important in many green energy technologies including wind turbine generators and hybrid-electric vehicle motors. For these applications, volume and weight are important factors driving the overall design, and therefore a high energy density, or energy product, is an important figure of merit. This quantity defines the magnetic energy contained in a given volume of material, and so higher energy density magnets enable smaller, lighter applications. Currently, the most powerful magnets suitable for commercial purposes contain rare earth elements (REE), usually neodymium and dysprosium in the neodymium-iron-boride class of magnets. However, for select applications, often requiring high temperatures,more » samarium cobalt is the alloy of choice. These magnets have energy densities several times greater than their nearest non-REE-based competitor, which for some applications is the defining factor in creating a viable device. The global supply of these REE is overwhelmingly produced in China, which in 2015 mined more than ten times as much as the next largest producer (Australia). Such market domination effectively creates a single source of supply, leaving industries which rely on REE consumption susceptible to price shocks and supply disruptions of these critical materials. Furthermore, this supply sensitivity may act as a drag on the adaptation rate of green energy technologies, particularly for large-scale users.« less

Applied magnetism: A supply-driven materials challenge

DOE PAGES

Rios, Orlando; McCall, Scott K.

2016-05-27

Permanent magnets are important in many green energy technologies including wind turbine generators and hybrid-electric vehicle motors. For these applications, volume and weight are important factors driving the overall design, and therefore a high energy density, or energy product, is an important figure of merit. This quantity defines the magnetic energy contained in a given volume of material, and so higher energy density magnets enable smaller, lighter applications. Currently, the most powerful magnets suitable for commercial purposes contain rare earth elements (REE), usually neodymium and dysprosium in the neodymium-iron-boride class of magnets. However, for select applications, often requiring high temperatures,more » samarium cobalt is the alloy of choice. These magnets have energy densities several times greater than their nearest non-REE-based competitor, which for some applications is the defining factor in creating a viable device. The global supply of these REE is overwhelmingly produced in China, which in 2015 mined more than ten times as much as the next largest producer (Australia). Such market domination effectively creates a single source of supply, leaving industries which rely on REE consumption susceptible to price shocks and supply disruptions of these critical materials. Furthermore, this supply sensitivity may act as a drag on the adaptation rate of green energy technologies, particularly for large-scale users.« less

Electrochromic Asymmetric Supercapacitor Windows Enable Direct Determination of Energy Status by the Naked Eye.

PubMed

Zhong, Ying; Chai, Zhisheng; Liang, Zhimin; Sun, Peng; Xie, Weiguang; Zhao, Chuanxi; Mai, Wenjie

2017-10-04

Because of the popularity of smart electronics, multifunctional energy storage devices, especially electrochromic supercapacitors (SCs), have attracted tremendous research interest. Herein, a solid-state electrochromic asymmetric SC (ASC) window is designed and fabricated by introducing WO 3 and polyaniline as the negative and positive electrodes, respectively. The two complementary materials contribute to the outstanding electrochemical and electrochromic performances of the fabricated device. With an operating voltage window of 1.4 V and an areal capacitance of 28.3 mF cm -2 , the electrochromic devices show a high energy density of 7.7 × 10 -3 mW h cm -2 . Meanwhile, they exhibit an obvious and reversible color transition between light green (uncharged state) and dark blue (charged state), with an optical transmittance change between 55 and 12% at a wavelength of 633 nm. Hence, the energy storage level of the ASC is directly related to its color and can be determined by the naked eye, which means it can be incorporated with other energy cells to visual display their energy status. Particularly, a self-powered and color-indicated system is achieved by combining the smart windows with commercial solar cell panels. We believe that the novel electrochromic ASC windows will have great potential application for both smart electronics and smart buildings.

Current status and future prospects of power generators using dielectric elastomers

NASA Astrophysics Data System (ADS)

Chiba, Seiki; Waki, Mikio; Kornbluh, Roy; Pelrine, Ron

2011-12-01

Electroactive polymer artificial muscle (EPAM), known collectively as dielectric elastomers in the literature, has been shown to offer unique capabilities as an actuator and is now being developed for a wide variety of generator applications. EPAM has several characteristics that make it potentially well suited for wave, water current, wind, human motion, and other environmental energy harvesting systems including a high energy density allowing for minimal EPAM material quantities, high energy conversion efficiency independent of frequency of operation and non-toxic and low-cost materials not susceptible to corrosion. Experiments have been performed on push-button and heel-mounted generator devices powered by human motion, ocean wave power harvesters mounted on buoys and water turbines. While the power output levels of such demonstration devices is small, the performance of these devices has supported the potential benefits of EPAM. For example, an electrical energy conversion efficiency of over 70% was achieved with small wave heights. The ability of EPAM to produce hydrogen fuel for energy storage was also demonstrated. Because the energy conversion principle of EPAM is capacitive in nature, the performance is largely independent of size and it should eventually be possible to scale up EPAM generators to the megawatt level to address a variety of electrical power needs.

Efficient Suppression of Defects and Charge Trapping in High Density In-Sn-Zn-O Thin Film Transistor Prepared using Microwave-Assisted Sputter.

PubMed

Goh, Youngin; Ahn, Jaehan; Lee, Jeong Rak; Park, Wan Woo; Ko Park, Sang-Hee; Jeon, Sanghun

2017-10-25

Amorphous oxide semiconductor-based thin film transistors (TFTs) have been considered as excellent switching elements for driving active-matrix organic light-emitting diodes (AMOLED) owing to their high mobility and process compatibility. However, oxide semiconductors have inherent defects, causing fast transient charge trapping and device instability. For the next-generation displays such as flexible, wearable, or transparent displays, an active semiconductor layer with ultrahigh mobility and high reliability at low deposition temperature is required. Therefore, we introduced high density plasma microwave-assisted (MWA) sputtering method as a promising deposition tool for the formation of high density and high-performance oxide semiconductor films. In this paper, we present the effect of the MWA sputtering method on the defects and fast charge trapping in In-Sn-Zn-O (ITZO) TFTs using various AC device characterization methodologies including fast I-V, pulsed I-V, transient current, low frequency noise, and discharge current analysis. Using these methods, we were able to analyze the charge trapping mechanism and intrinsic electrical characteristics, and extract the subgap density of the states of oxide TFTs quantitatively. In comparison to conventional sputtered ITZO, high density plasma MWA-sputtered ITZO exhibits outstanding electrical performance, negligible charge trapping characteristics and low subgap density of states. High-density plasma MWA sputtering method has high deposition rate even at low working pressure and control the ion bombardment energy, resulting in forming low defect generation in ITZO and presenting high performance ITZO TFT. We expect the proposed high density plasma sputtering method to be applicable to a wide range of oxide semiconductor device applications.

All-solid-state flexible supercapacitors based on highly dispersed polypyrrole nanowire and reduced graphene oxide composites.

PubMed

Yu, Chenfei; Ma, Peipei; Zhou, Xi; Wang, Anqi; Qian, Tao; Wu, Shishan; Chen, Qiang

2014-10-22

Highly dispersed polypyrrole nanowires are decorated on reduced graphene oxide sheets using a facile in situ synthesis route. The prepared composites exhibit high dispersibility, large effective surface area, and high electric conductivity. All-solid-state flexible supercapacitors are assembled based on the prepared composites, which show excellent electrochemical performances with a specific capacitance of 434.7 F g(-1) at a current density of 1 A g(-1). The as-fabricated supercapacitor also exhibits excellent cycling stability (88.1% capacitance retention after 5000 cycles) and exceptional mechanical flexibility. In addition, outstanding power and energy densities were obtained, demonstrating the significant potential of prepared material for flexible and portable energy storage devices.

Fast semi-analytical method for precise prediction of ion energy distribution functions and sheath electric field in multi-frequency capacitively coupled plasmas

NASA Astrophysics Data System (ADS)

Chen, Wencong; Zhang, Xi; Diao, Dongfeng

2018-05-01

We propose a fast semi-analytical method to predict ion energy distribution functions and sheath electric field in multi-frequency capacitively coupled plasmas, which are difficult to measure in commercial plasma reactors. In the intermediate frequency regime, the ion density within the sheath is strongly modulated by the low-frequency sheath electric field, making the time-independent ion density assumption employed in conventional models invalid. Our results are in a good agreement with experimental measurements and computer simulations. The application of this method will facilitate the understanding of ion–material interaction mechanisms and development of new-generation plasma etching devices.

Low power energy harvesting and storage techniques from ambient human powered energy sources

NASA Astrophysics Data System (ADS)

Yildiz, Faruk

Conventional electrochemical batteries power most of the portable and wireless electronic devices that are operated by electric power. In the past few years, electrochemical batteries and energy storage devices have improved significantly. However, this progress has not been able to keep up with the development of microprocessors, memory storage, and sensors of electronic applications. Battery weight, lifespan and reliability often limit the abilities and the range of such applications of battery powered devices. These conventional devices were designed to be powered with batteries as required, but did not allow scavenging of ambient energy as a power source. In contrast, development in wireless technology and other electronic components are constantly reducing the power and energy needed by many applications. If energy requirements of electronic components decline reasonably, then ambient energy scavenging and conversion could become a viable source of power for many applications. Ambient energy sources can be then considered and used to replace batteries in some electronic applications, to minimize product maintenance and operating cost. The potential ability to satisfy overall power and energy requirements of an application using ambient energy can eliminate some constraints related to conventional power supplies. Also power scavenging may enable electronic devices to be completely self-sustaining so that battery maintenance can eventually be eliminated. Furthermore, ambient energy scavenging could extend the performance and the lifetime of the MEMS (Micro electromechanical systems) and portable electronic devices. These possibilities show that it is important to examine the effectiveness of ambient energy as a source of power. Until recently, only little use has been made of ambient energy resources, especially for wireless networks and portable power devices. Recently, researchers have performed several studies in alternative energy sources that could provide small amounts of electricity to low-power electronic devices. These studies were focused to investigate and obtain power from different energy sources, such as vibration, light, sound, airflow, heat, waste mechanical energy and temperature variations. This research studied forms of ambient energy sources such as waste mechanical (rotational) energy from hydraulic door closers, and fitness exercise bicycles, and its conversion and storage into usable electrical energy. In both of these examples of applications, hydraulic door closers and fitness exercise bicycles, human presence is required. A person has to open the door in order for the hydraulic door closer mechanism to function. Fitness exercise bicycles need somebody to cycle the pedals to generate electricity (while burning calories.) Also vibrations, body motions, and compressions from human interactions were studied using small piezoelectric fiber composites which are capable of recovering waste mechanical energy and converting it to useful electrical energy. Based on ambient energy sources, electrical energy conversion and storage circuits were designed and tested for low power electronic applications. These sources were characterized according to energy harvesting (scavenging) methods, and power and energy density. At the end of the study, the ambient energy sources were matched with possible electronic applications as a viable energy source.

Fabrication of a 3D Hierarchical Sandwich Co9 S8 /α-MnS@N-C@MoS2 Nanowire Architectures as Advanced Electrode Material for High Performance Hybrid Supercapacitors.

PubMed

Kandula, Syam; Shrestha, Khem Raj; Kim, Nam Hoon; Lee, Joong Hee

2018-06-01

Supercapacitors suffer from lack of energy density and impulse the energy density limit, so a new class of hybrid electrode materials with promising architectures is strongly desirable. Here, the rational design of a 3D hierarchical sandwich Co 9 S 8 /α-MnS@N-C@MoS 2 nanowire architecture is achieved during the hydrothermal sulphurization reaction by the conversion of binary mesoporous metal oxide core to corresponding individual metal sulphides core along with the formation of outer metal sulphide shell at the same time. Benefiting from the 3D hierarchical sandwich architecture, Co 9 S 8 /α-MnS@N-C@MoS 2 electrode exhibits enhanced electrochemical performance with high specific capacity/capacitance of 306 mA h g -1 /1938 F g -1 at 1 A g -1 , and excellent cycling stability with a specific capacity retention of 86.9% after 10 000 cycles at 10 A g -1 . Moreover, the fabricated asymmetric supercapacitor device using Co 9 S 8 /α-MnS@N-C@MoS 2 as the positive electrode and nitrogen doped graphene as the negative electrode demonstrates high energy density of 64.2 Wh kg -1 at 729.2 W kg -1 , and a promising energy density of 23.5 Wh kg -1 is still attained at a high power density of 11 300 W kg -1 . The hybrid electrode with 3D hierarchical sandwich architecture promotes enhanced energy density with excellent cyclic stability for energy storage. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Designing 3D Multihierarchical Heteronanostructures for High-Performance On-Chip Hybrid Supercapacitors: Poly(3,4-(ethylenedioxy)thiophene)-Coated Diamond/Silicon Nanowire Electrodes in an Aprotic Ionic Liquid.

PubMed

Aradilla, David; Gao, Fang; Lewes-Malandrakis, Georgia; Müller-Sebert, Wolfgang; Gentile, Pascal; Boniface, Maxime; Aldakov, Dmitry; Iliev, Boyan; Schubert, Thomas J S; Nebel, Christoph E; Bidan, Gérard

2016-07-20

A versatile and robust hierarchically multifunctionalized nanostructured material made of poly(3,4-(ethylenedioxy)thiophene) (PEDOT)-coated diamond@silicon nanowires has been demonstrated to be an excellent capacitive electrode for supercapacitor devices. Thus, the electrochemical deposition of nanometric PEDOT films on diamond-coated silicon nanowire (SiNW) electrodes using N-methyl-N-propylpyrrolidinium bis((trifluoromethyl)sulfonyl)imide ionic liquid displayed a specific capacitance value of 140 F g(-1) at a scan rate of 1 mV s(-1). The as-grown functionalized electrodes were evaluated in a symmetric planar microsupercapacitor using butyltrimethylammonium bis((trifluoromethyl)sulfonyl)imide aprotic ionic liquid as the electrolyte. The device exhibited extraordinary energy and power density values of 26 mJ cm(-2) and 1.3 mW cm(-2) within a large voltage cell of 2.5 V, respectively. In addition, the system was able to retain 80% of its initial capacitance after 15 000 galvanostatic charge-discharge cycles at a high current density of 1 mA cm(-2) while maintaining a Coulombic efficiency around 100%. Therefore, this multifunctionalized hybrid device represents one of the best electrochemical performances concerning coated SiNW electrodes for a high-energy advanced on-chip supercapacitor.

Silicone-Based Triboelectric Nanogenerator for Water Wave Energy Harvesting.

PubMed

Xiao, Tian Xiao; Jiang, Tao; Zhu, Jian Xiong; Liang, Xi; Xu, Liang; Shao, Jia Jia; Zhang, Chun Lei; Wang, Jie; Wang, Zhong Lin

2018-01-31

Triboelectric nanogenerator (TENG) has been proven to be efficient for harvesting water wave energy, which is one of the most promising renewable energy sources. In this work, a TENG with a silicone rubber/carbon black composite electrode was designed for converting the water wave energy into electricity. The silicone-based electrode with a soft texture provides a better contact with the dielectric film. Furthermore, a spring structure is introduced to transform low-frequency water wave motions into high-frequency vibrations. They together improve the output performance and efficiency of TENG. The output performances of TENGs are further enhanced by optimizing the triboelectric material pair and tribo-surface area. A spring-assisted TENG device with the segmented silicone rubber-based electrode structure was sealed into a waterproof box, which delivers a maximum power density of 2.40 W m -3 , as triggered by the water waves. The present work provides a new strategy for fabricating high-performance TENG devices by coupling flexible electrodes and spring structure for harvesting water wave energy.

Achieving Ultrahigh Energy Density and Long Durability in a Flexible Rechargeable Quasi-Solid-State Zn-MnO2 Battery.

PubMed

Zeng, Yinxiang; Zhang, Xiyue; Meng, Yue; Yu, Minghao; Yi, Jianan; Wu, Yiqiang; Lu, Xihong; Tong, Yexiang

2017-07-01

Advanced flexible batteries with high energy density and long cycle life are an important research target. Herein, the first paradigm of a high-performance and stable flexible rechargeable quasi-solid-state Zn-MnO 2 battery is constructed by engineering MnO 2 electrodes and gel electrolyte. Benefiting from a poly(3,4-ethylenedioxythiophene) (PEDOT) buffer layer and a Mn 2+ -based neutral electrolyte, the fabricated Zn-MnO 2 @PEDOT battery presents a remarkable capacity of 366.6 mA h g -1 and good cycling performance (83.7% after 300 cycles) in aqueous electrolyte. More importantly, when using PVA/ZnCl 2 /MnSO 4 gel as electrolyte, the as-fabricated quasi-solid-state Zn-MnO 2 @PEDOT battery remains highly rechargeable, maintaining more than 77.7% of its initial capacity and nearly 100% Coulombic efficiency after 300 cycles. Moreover, this flexible quasi-solid-state Zn-MnO 2 battery achieves an admirable energy density of 504.9 W h kg -1 (33.95 mW h cm -3 ), together with a peak power density of 8.6 kW kg -1 , substantially higher than most recently reported flexible energy-storage devices. With the merits of impressive energy density and durability, this highly flexible rechargeable Zn-MnO 2 battery opens new opportunities for powering portable and wearable electronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Plasma Properties of an Exploding Semiconductor Igniter

NASA Astrophysics Data System (ADS)

McGuirk, J. S.; Thomas, K. A.; Shaffer, E.; Malone, A. L.; Baginski, T.; Baginski, M. E.

1997-11-01

Requirements by the automotive industry for low-cost, pyrotechnic igniters for automotive airbags have led to the development of several semiconductor devices. The properties of the plasma produced by the vaporization of an exploding semiconductor are necessary in order to minimize the electrical energy requirements. This work considers two silicon-based semiconductor devices: the semiconductor bridge (SCB) and the semiconductor junction igniter both consisting of etched silicon with vapor deposited aluminum structures. Electrical current passing through the device heats a narrow junction region to the point of vaporization creating an aluminum and silicon low-temperature plasma. This work will investigate the electrical characteristics of both devices and infer the plasma properties. Furthermore optical spectral measurements will be taken of the exploding devices to estimate the temperature and density of the plasma.

Theoretical and material studies of thin-film electroluminescent devices

NASA Technical Reports Server (NTRS)

Summers, C. J.

1989-01-01

Thin-film electroluminescent (TFEL) devices are studied for a possible means of achieving a high resolution, light weight, compact video display panel for computer terminals or television screens. The performance of TFEL devices depends upon the probability of an electron impact exciting a luminescent center which in turn depends upon the density of centers present in the semiconductor layer, the possibility of an electron achieving the impact excitation threshold energy, and the collision cross section itself. Efficiency of such a device is presently very poor. It can best be improved by increasing the number of hot electrons capable of impact exciting a center. Hot electron distributions and a method for increasing the efficiency and brightness of TFEL devices (with the additional advantage of low voltage direct current operation) are investigated.

Solution synthesis of metal oxides for electrochemical energy storage applications.

PubMed

Xia, Xinhui; Zhang, Yongqi; Chao, Dongliang; Guan, Cao; Zhang, Yijun; Li, Lu; Ge, Xiang; Bacho, Ignacio Mínguez; Tu, Jiangping; Fan, Hong Jin

2014-05-21

This article provides an overview of solution-based methods for the controllable synthesis of metal oxides and their applications for electrochemical energy storage. Typical solution synthesis strategies are summarized and the detailed chemical reactions are elaborated for several common nanostructured transition metal oxides and their composites. The merits and demerits of these synthesis methods and some important considerations are discussed in association with their electrochemical performance. We also propose the basic guideline for designing advanced nanostructure electrode materials, and the future research trend in the development of high power and energy density electrochemical energy storage devices.

Investigation of Oxygen and Hydrogen Associated Charge Trapping and Electrical Characteristics of Silicon Nitride Films for Mnos Devices.

NASA Astrophysics Data System (ADS)

Xu, Dan

Silicon nitride (Si_3N _4) and silicon oxynitride (SiO _{rm x}N_ {rm y}) films in the form of metal -nitride-oxide-silicon (MNOS) structures were investigated to determine the correlation between their electrical characteristics and the nature of the chemical bonding so as to provide guidelines for the next generation of nonvolatile memory devices. The photoionization cross section of electron traps in the oxynitride films of MNOS devices were also measured as a function photon energy and oxygen concentration of the silicon oxynitride films. An effective photoionization cross section associated with electron traps was determined to be between 4.9 times 10 ^{-19} cm^2 to 10.8 times 10^ {-19} cm^2 over the photon energy of 2.06 eV to 3.1 eV for silicon oxynitride films containing 7 atomic % to 17 atomic % of oxygen. The interface state density of metal-nitride-oxide -silicon (MNOS) devices was investigated as a function of processing conditions. The interface state density around the midgap of the oxide-silicon interface of the MNOS structures for deposition temperature between 650^ circC to 850^circC increased from 1.1 to 8.2 times 10 ^{11} cm^ {-2}eV^{-1}, for as-deposited silicon nitride films; but decreased from 5.0 to 3.5 times 10^ {11} cm^{-2} eV^{-1}, for films annealed in nitrogen at 900^circC for 60 minutes; and further decreased and remained constant at 1.5 times 10^{11 } cm^{-2}eV ^{-1}, for films which were further annealed in hydrogen at 900^ circC for an additional 60 minutes. The interface state density increase was due to an increase in the loss of hydrogen at the interfacial region and also due to an increase in the thermal stress caused by differences in thermal expansion coefficients of silicon nitride and silicon dioxide films at higher deposition temperatures. The interface state density was subject to two opposing influences; an increase by thermal stress, and a reduction by hydrogen compensation of these states. The photocurrent-voltage (photoI-V) technique in combination with internal photo-electric technique were employed to determine the trapped charge density and its centroid as a function of processing conditions. Results showed that the trapped charge density was of the order of 10^{18} cm ^{-3}. However, the charge trapping density increased about 30% as the atomic percentage of hydrogen decreased from 6 to 2 atomic %.

Multifunctional composites for energy storage

NASA Astrophysics Data System (ADS)

Shuvo, Mohammad Arif I.; Karim, Hasanul; Rajib, Md; Delfin, Diego; Lin, Yirong

2014-03-01

Electrochemical super-capacitors have become one of the most important topics in both academia and industry as novel energy storage devices because of their high power density, long life cycles, and high charge/discharge efficiency. Recently, there has been an increasing interest in the development of multifunctional structural energy storage devices such as structural super-capacitors for applications in aerospace, automobiles and portable electronics. These multifunctional structural super-capacitors provide lighter structures combining energy storage and load bearing functionalities. Due to their superior materials properties, carbon fiber composites have been widely used in structural applications for aerospace and automotive industries. Besides, carbon fiber has good electrical conductivity which will provide lower equivalent series resistance; therefore, it can be an excellent candidate for structural energy storage applications. Hence, this paper is focused on performing a pilot study for using nanowire/carbon fiber hybrids as building materials for structural energy storage materials; aiming at enhancing the charge/discharge rate and energy density. This hybrid material combines the high specific surface area of carbon fiber and pseudo-capacitive effect of metal oxide nanowires which were grown hydrothermally in an aligned fashion on carbon fibers. The aligned nanowire array could provide a higher specific surface area that leads to high electrode-electrolyte contact area and fast ion diffusion rates. Scanning Electron Microscopy (SEM) and XRay Diffraction (XRD) measurements were used for the initial characterization of this nanowire/carbon fiber hybrid material system. Electrochemical testing has been performed using a potentio-galvanostat. The results show that gold sputtered nanowire hybrid carbon fiber provides 65.9% better performance than bare carbon fiber cloth as super-capacitor.

Enhancing pseudocapacitive charge storage in polymer templated mesoporous materials.

PubMed

Rauda, Iris E; Augustyn, Veronica; Dunn, Bruce; Tolbert, Sarah H

2013-05-21

Growing global energy demands coupled with environmental concerns have increased the need for renewable energy sources. For intermittent renewable sources like solar and wind to become available on demand will require the use of energy storage devices. Batteries and supercapacitors, also known as electrochemical capacitors (ECs), represent the most widely used energy storage devices. Supercapacitors are frequently overlooked as an energy storage technology, however, despite the fact that these devices provide greater power, much faster response times, and longer cycle life than batteries. Their limitation is that the energy density of ECs is significantly lower than that of batteries, and this has limited their potential applications. This Account reviews our recent work on improving pseudocapacitive energy storage performance by tailoring the electrode architecture. We report our studies of mesoporous transition metal oxide architectures that store charge through surface or near-surface redox reactions, a phenomenon termed pseudocapacitance. The faradaic nature of pseudocapacitance leads to significant increases in energy density and thus represents an exciting future direction for ECs. We show that both the choice of material and electrode architecture is important for producing the ideal pseudocapacitor device. Here we first briefly review the current state of electrode architectures for pseudocapacitors, from slurry electrodes to carbon/metal oxide composites. We then describe the synthesis of mesoporous films made with amphiphilic diblock copolymer templating agents, specifically those optimized for pseudocapacitive charge storage. These include films synthesized from nanoparticle building blocks and films made from traditional battery materials. In the case of more traditional battery materials, we focus on using flexible architectures to minimize the strain associated with lithium intercalation, that is, the accumulation of lithium ions or atoms between the layers of cathode or anode materials that occurs as batteries charge and discharge. Electrochemical analysis of these mesoporous films allows for a detailed understanding of the origin of charge storage by separating capacitive contributions from traditional diffusion-controlled intercalation processes. We also discuss methods to separate the two contributions to capacitance: double-layer capacitance and pseudocapacitance. Understanding these contributions should allow the selection of materials with an optimized architecture that maximize the contribution from pseudocapacitance. From our studies, we show that nanocrystal-based nanoporous materials offer an architecture optimized for high levels of redox or surface pseudocapacitance. Interestingly, in some cases, materials engineered to minimize the strain associated with lithium insertion can also show intercalation pseudocapacitance, which is a process where insertion processes become so kinetically facile that they appear capacitive. Finally, we conclude with a summary of simple design rules that should result in high-power, high-energy-density electrode architectures. These design rules include assembling small, nanosized building blocks to maximize electrode surface area; maintaining an interconnected, open mesoporosity to facilitate solvent diffusion; seeking flexibility in electrode structure to facilitate volume expansion during lithium insertion; optimizing crystalline domain size and orientation; and creating effective electron transport pathways.

Energy harvesting device based on a metallic glass/PVDF magnetoelectric laminated composite

NASA Astrophysics Data System (ADS)

Lasheras, A.; Gutiérrez, J.; Reis, S.; Sousa, D.; Silva, M.; Martins, P.; Lanceros-Mendez, S.; Barandiarán, J. M.; Shishkin, D. A.; Potapov, A. P.

2015-06-01

A flexible, low-cost energy-harvesting device based on the magnetoelectric (ME) effect was designed using Fe64Co17Si7B12 as amorphous magnetostrictive ribbons and polyvinylidene fluoride (PVDF) as the piezoelectric element. A 3 cm-long sandwich-type laminated composite was fabricated by gluing the ribbons to the PVDF with an epoxy resin. A voltage multiplier circuit was designed to produce enough voltage to charge a battery. The power output and power density obtained were 6.4 μW and 1.5 mW cm-3, respectively, at optimum load resistance and measured at the magnetomechanical resonance of the laminate. The effect of the length of the ME laminate on power output was also studied: the power output exhibited decays proportionally with the length of the ME laminate. Nevertheless, good performance was obtained for a 0.5 cm-long device working at 337 KHz within the low radio frequency (LRF) range.

Electromagnetic interference of cardiac rhythmic monitoring devices to radio frequency identification: analytical analysis and mitigation methodology.

PubMed

Ogirala, Ajay; Stachel, Joshua R; Mickle, Marlin H

2011-11-01

Increasing density of wireless communication and development of radio frequency identification (RFID) technology in particular have increased the susceptibility of patients equipped with cardiac rhythmic monitoring devices (CRMD) to environmental electro magnetic interference (EMI). Several organizations reported observing CRMD EMI from different sources. This paper focuses on mathematically analyzing the energy as perceived by the implanted device, i.e., voltage. Radio frequency (RF) energy transmitted by RFID interrogators is considered as an example. A simplified front-end equivalent circuit of a CRMD sensing circuitry is proposed for the analysis following extensive black-box testing of several commercial pacemakers and implantable defibrillators. After careful understanding of the mechanics of the CRMD signal processing in identifying the QRS complex of the heart-beat, a mitigation technique is proposed. The mitigation methodology introduced in this paper is logical in approach, simple to implement and is therefore applicable to all wireless communication protocols.

V2O5 encapsulated MWCNTs in 2D surface architecture: Complete solid-state bendable highly stabilized energy efficient supercapacitor device

NASA Astrophysics Data System (ADS)

Pandit, Bidhan; Dubal, Deepak P.; Gómez-Romero, Pedro; Kale, Bharat B.; Sankapal, Babasaheb R.

2017-03-01

A simple and scalable approach has been reported for V2O5 encapsulation over interconnected multi-walled carbon nanotubes (MWCNTs) network using chemical bath deposition method. Chemically synthesized V2O5/MWCNTs electrode exhibited excellent charge-discharge capability with extraordinary cycling retention of 93% over 4000 cycles in liquid-electrolyte. Electrochemical investigations have been performed to evaluate the origin of capacitive behavior from dual contribution of surface-controlled and diffusion-controlled charge components. Furthermore, a complete flexible solid-state, flexible symmetric supercapacitor (FSS-SSC) device was assembled with V2O5/MWCNTs electrodes which yield remarkable values of specific power and energy densities along with enhanced cyclic stability over liquid configuration. As a practical demonstration, the constructed device was used to lit the ‘VNIT’ acronym assembled using 21 LED’s.

Mixtures of glyme and aprotic-protic ionic liquids as electrolytes for energy storage devices

NASA Astrophysics Data System (ADS)

Stettner, T.; Huang, P.; Goktas, M.; Adelhelm, P.; Balducci, A.

2018-05-01

Ionic liquids (ILs) have been proven to be promising electrolytes for electrochemical energy storage devices such as supercapacitors and lithium ion batteries. In the last years, due to deficiency in storage of lithium on earth, innovative systems, such as sodium-based devices, attracted considerable attention. IL-based electrolytes have been proposed also as electrolytes for these devices. Nevertheless, in the case of these systems, the advantages and limits of IL-based electrolytes need to be further investigated. In this work we report an investigation about the chemical-physical properties of mixtures containing bis(2-methoxyethyl)ether diglyme (2G), which is presently considered as one of the most interesting solvents for sodium-based devices, and the ionic liquids 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide (Pyr14TFSI) and 1-butylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PyrH4TFSI). The conductivities, viscosities, and densities of several mixtures of 2G and these ILs have been investigated. Furthermore, their impact on the electrochemical behaviour of activated carbon composite electrodes has been considered. The results of this investigation indicate that these mixtures are promising electrolytes for the realization of advanced sodium-based devices.

Flexible patch composed of PZT thin-film on stainless steel foil for energy harvesting from low-frequency human motions

NASA Astrophysics Data System (ADS)

Wang, Yin Jie; Chen, Chao Ting; Chen, Jiun Jung; Yeh, Sou Peng; Wu, Wen Jong

2015-03-01

To harvest energy from human motion and generate power for the emerging wearable devices, energy harvesters are required to work at very low frequency. There are several studies based on energy harvesting through human gait, which can generate significant power. However, when wearing these kind of devices, additional effort may be required and the user may feel uncomfortable when moving. The energy harvester developed here is composed of a 10 μm PZT thin-film deposited on 50 μm thick stainless steel foil by the aerosol deposition method. The PZT layer and the stainless steel foil are both very thin, thus the patch is highly flexible. The patch can be attached on the skin to harvester power through human motions such as the expansion of the chest region while breathing. The energy harvester will first be tested with a moving stage for power output measurements. The energy density can be determined for different deformation ranges and frequencies. The fabrication processes and testing results will all be detailed in this paper.

Engineering the Pores of Biomass-Derived Carbon: Insights for Achieving Ultrahigh Stability at High Power in High-Energy Supercapacitors.

PubMed

Thangavel, Ranjith; Kaliyappan, Karthikeyan; Ramasamy, Hari Vignesh; Sun, Xueliang; Lee, Yun-Sung

2017-07-10

Electrochemical supercapacitors with high energy density are promising devices due to their simple construction and long-term cycling performance. The development of a supercapacitor based on electrical double-layer charge storage with high energy density that can preserve its cyclability at higher power presents an ongoing challenge. Herein, we provide insights to achieve a high energy density at high power with an ultrahigh stability in an electrical double-layer capacitor (EDLC) system by using carbon from a biomass precursor (cinnamon sticks) in a sodium ion-based organic electrolyte. Herein, we investigated the dependence of EDLC performance on structural, textural, and functional properties of porous carbon engineered by using various activation agents. The results demonstrate that the performance of EDLCs is not only dependent on their textural properties but also on their structural features and surface functionalities, as is evident from the electrochemical studies. The electrochemical results are highly promising and revealed that the porous carbon with poor textural properties has great potential to deliver high capacitance and outstanding stability over 300 000 cycles compared with porous carbon with good textural properties. A very low capacitance degradation of around 0.066 % per 1000 cycles, along with high energy density (≈71 Wh kg -1 ) and high power density, have been achieved. These results offer a new platform for the application of low-surface-area biomass-derived carbons in the design of highly stable high-energy supercapacitors. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

High-Performance Flexible All-Solid-State Asymmetric Supercapacitors Based on Vertically Aligned CuSe@Co(OH) 2 Nanosheet Arrays

DOE PAGES

Gong, Jiangfeng; Tian, Yazhou; Yang, Ziyuan; ...

2018-01-04

The developments of electrode active materials provide the opportunities for next-generation energy storage devices. The arrangement of electrode materials on the substrate has recently emerged as a promising strategy for preparing high-performance supercapacitors. In this paper, we demonstrate a novel vertically aligned CuSe@Co(OH) 2 nanosheet arrays electrode for supercapacitor application. The materials are thoroughly characterized by structural and spectroscopic techniques. Electrochemical performance of CuSe@Co(OH) 2 nanosheet arrays are investigated in detail, which exhibit a specific capacitance as much as 1180 F g -1 at a current density of 1 A g -1. A flexible asymmetric all-solid-state supercapacitor is fabricated usingmore » CuSe@Co(OH) 2 nanosheet arrays as the positive electrode and activated carbon as the negative electrode. The device delivers a volumetric capacitance of 441.4 mF cm -3 with maximum energy density and maximum power density is 0.17 and 62.1 mW cm -3, as well as robust cycling stability (~80.4% capacitance retention after 10 000 cycles), excellent flexibility, and mechanical stability. Finally, the excellent electrochemical performance can be attributed to its unique vertically aligned configuration.« less

High Concentrating GaAs Cell Operation Using Optical Waveguide Solar Energy System

NASA Technical Reports Server (NTRS)

Nakamura, T.; Case, J. A.; Timmons, M. L.

2004-01-01

This paper discusses the result of the concentrating photovoltaic (CPV) cell experiments conducted with the Optical Waveguide (OW) Solar Energy System. The high concentration GaAs cells developed by Research Triangle Institute (RTI) were combined with the OW system in a "fiber-on-cell" configuration. The sell performance was tested up to the solar concentration of 327. Detailed V-I characteristics, power density and efficiency data were collected. It was shown that the CPV cells combined with the OW solar energy system will be an effective electric power generation device.

Dye-sensitized solar cell with energy storage function through PVDF/ZnO nanocomposite counter electrode.

PubMed

Zhang, Xi; Huang, Xuezhen; Li, Chensha; Jiang, Hongrui

2013-08-14

Dye-sensitized solar cells with an energy storage function are demonstrated by modifying its counter electrode with a poly (vinylidene fluoride)/ZnO nanowire array composite. This simplex device could still function as an ordinary solar cell with a steady photocurrent output even after being fully charged. An energy storage density of 2.14 C g(-1) is achieved, while simultaneously a 3.70% photo-to-electric conversion efficiency is maintained. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Negative hydrogen ion production in a helicon plasma source

DOE Office of Scientific and Technical Information (OSTI.GOV)

Santoso, J., E-mail: Jesse.Santoso@anu.edu.au; Corr, C. S.; Manoharan, R.

2015-09-15

In order to develop very high energy (>1 MeV) neutral beam injection systems for applications, such as plasma heating in fusion devices, it is necessary first to develop high throughput negative ion sources. For the ITER reference source, this will be realised using caesiated inductively coupled plasma devices, containing either hydrogen or deuterium discharges, operated with high rf input powers (up to 90 kW per driver). It has been suggested that due to their high power coupling efficiency, helicon devices may be able to reduce power requirements and potentially obviate the need for caesiation due to the high plasma densities achievable. Here,more » we present measurements of negative ion densities in a hydrogen discharge produced by a helicon device, with externally applied DC magnetic fields ranging from 0 to 8.5 mT at 5 and 10 mTorr fill pressures. These measurements were taken in the magnetised plasma interaction experiment at the Australian National University and were performed using the probe-based laser photodetachment technique, modified for the use in the afterglow of the plasma discharge. A peak in the electron density is observed at ∼3 mT and is correlated with changes in the rf power transfer efficiency. With increasing magnetic field, an increase in the negative ion fraction from 0.04 to 0.10 and negative ion densities from 8 × 10{sup 14 }m{sup −3} to 7 × 10{sup 15 }m{sup −3} is observed. It is also shown that the negative ion densities can be increased by a factor of 8 with the application of an external DC magnetic field.« less

DNA-based nanobiostructured devices: The role of quasiperiodicity and correlation effects

NASA Astrophysics Data System (ADS)

Albuquerque, E. L.; Fulco, U. L.; Freire, V. N.; Caetano, E. W. S.; Lyra, M. L.; de Moura, F. A. B. F.

2014-02-01

The purpose of this review is to present a comprehensive and up-to-date account of the main physical properties of DNA-based nanobiostructured devices, stressing the role played by their quasi-periodicity arrangement and correlation effects. Although the DNA-like molecule is usually described as a short-ranged correlated random ladder, artificial segments can be grown following quasiperiodic sequences as, for instance, the Fibonacci and Rudin-Shapiro ones. They have interesting properties like a complex fractal spectra of energy, which can be considered as their indelible mark, and collective properties that are not shared by their constituents. These collective properties are due to the presence of long-range correlations, which are expected to be reflected somehow in their various spectra (electronic transmission, density of states, etc.) defining another description of disorder. Although long-range correlations are responsible for the effective electronic transport at specific resonant energies of finite DNA segments, much of the anomalous spread of an initially localized electron wave-packet can be accounted by short-range pair correlations, suggesting that an approach based on the inclusion of further short-range correlations on the nucleotide distribution leads to an adequate description of the electronic properties of DNA segments. The introduction of defects may generate states within the gap, and substantially improves the conductance, specially of finite branches. They usually become exponentially localized for any amount of disorder, and have the property to tailor the electronic transport properties of DNA-based nanoelectronic devices. In particular, symmetric and antisymmetric correlations have quite distinct influence on the nature of the electronic states, and a diluted distribution of defects lead to an anomalous diffusion of the electronic wave-packet. Nonlinear contributions, arising from the coupling between electrons and the molecular vibrations, promote an electronic self-trapping, thus opening up the possibility of controlling the spreading of the electronic density by an external field. The main features of DNA-based nanobiostructured devices presented in this review will include their electronic density of states, energy profiles, thermodynamic properties, localization, correlation effects, scale laws, fractal and multifractal analysis, and anhydrous crystals of their bases, among others. New features, like other nanobiostructured devices, as well as the future directions in this field are also presented and discussed.

Limiting factors to advancing thermal battery technology for naval applications

NASA Astrophysics Data System (ADS)

Davis, Patrick B.; Winchester, Clinton S.

1991-10-01

Thermal batteries are primary reserve electrochemical power sources using molten salt electrolyte which experience little effective aging while in storage or dormant deployment. Thermal batteries are primarily used in military applications, and are currently used in a wide variety of Navy devices such as missiles, torpedoes, decays, and training targets, usually as power supplies in guidance, propulsion, and Safe/Arm applications. Technology developments have increased the available energy and power density ratings by an order of magnitude in the last ten years. Present thermal batteries, using lithium anodes and metal sulfide cathodes, are capable of performing applications where only less rugged and more expensive silver oxide/zinc or silver/magnesium chloride seawater batteries could serve previously. Additionally, these batteries are capable of supplanting lithium/thionyl chloride reserve batteries in a variety of specifically optimized designs. Increases in thermal battery energy and power density capabilities are not projected to continue with the current available technology. Several battery designs are now at the edge of feasibility and safety. Since future naval systems are likely to require continued growth of battery energy and power densities, there must be significant advances in battery technology. Specifically, anode alloy composition and new cathode materials must be investigated to allow for safe development and deployment of these high power, higher energy density batteries.

Note: Experimental platform for magnetized high-energy-density plasma studies at the omega laser facility

NASA Astrophysics Data System (ADS)

Fiksel, G.; Agliata, A.; Barnak, D.; Brent, G.; Chang, P.-Y.; Folnsbee, L.; Gates, G.; Hasset, D.; Lonobile, D.; Magoon, J.; Mastrosimone, D.; Shoup, M. J.; Betti, R.

2015-01-01

An upgrade of the pulsed magnetic field generator magneto-inertial fusion electrical discharge system [O. Gotchev et al., Rev. Sci. Instrum. 80, 043504 (2009)] is described. The device is used to study magnetized high-energy-density plasma and is capable of producing a pulsed magnetic field of tens of tesla in a volume of a few cubic centimeters. The magnetic field is created by discharging a high-voltage capacitor through a small wire-wound coil. The coil current pulse has a duration of about 1 μs and a peak value of 40 kA. Compared to the original, the updated version has a larger energy storage and improved switching system. In addition, magnetic coils are fabricated using 3-D printing technology which allows for a greater variety of the magnetic field topology.