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Showing papers on "Supercapacitor published in 1997"


Journal ArticleDOI
TL;DR: In this paper, the double-layer capacitance of carbon powder electrodes has been used as a means of storing electrical energy in a supercapacitor or an ultracapacitor, where the pseudocapacitance arises when, for thermodynamic reasons, the charge q required for progression of an electrode process is a continuous function of potential, V ; then the derivative d q /d V corresponds to a capacitance but one of a Faradaic kind.

1,417 citations


Journal ArticleDOI
TL;DR: In this article, several mechanisms of self-discharge are distinguished and the resulting forms of the change of potential on open-circuit with time or log time provide a means of identifying the type of selfdischarge process that occurs.

282 citations


Journal ArticleDOI
TL;DR: In this paper, the self-discharge kinetics of charged RuO 2 electrodes are studied and a remarkable phenomenon of successive potential recovery after sequential discharge transients is reported, in terms of a process of diffusion of oxidation state involving proton and electron hopping.

232 citations


Journal ArticleDOI
TL;DR: In this paper, the preparation and characterization of high surface area ruthenium/carbon aerogel composite electrodes for use in electrochemical capacitors is reported, and the composites have demonstrated specific capacitances in excess of 200 F/g.
Abstract: : The preparation and characterization of high surface area ruthenium/carbon aerogel composite electrodes for use in electrochemical capacitors is reported. These new materials have been prepared by the chemical vapor impregnation of ruthenium into carbon aerogels to produce a uniform distribution of adherent approx. 2 nm nanoparticles on the aerogel surface. The electrochemically oxidized ruthenium particles contribute a pseudocapacitance to the electrode and dramatically improve the energy storage characteristics of the aerogel. These composites have demonstrated specific capacitances in excess of 200 F/g, in comparison to 95 F/g for the untreated aerogel.

226 citations


Journal ArticleDOI
TL;DR: In this article, the conjugated polymer poly(3,4-ethylenedioxythiophene) was used as electrode material in an electrochemical supercapacitor and the energy density was measured to 1 to 4 Wh/kg of active electrode material, depending on the current density used during discharge.
Abstract: We have investigated the conjugated polymer poly(3,4-ethylenedioxythiophene) as electrode material in electrochemical supercapacitor. The conjugated polymer is prepared by chemical polymerization in the form of thin films on nonconducting plastic substrates. One film is electrochemically reduced to the neutral state, while the other is kept in the as-prepared, doped state. The films are thin immersed in a liquid organic electrolyte. In the charged state the supercapacitor cell voltage is 0.8 V and the energy density is measured to 1 to 4 Wh/kg of active electrode material, depending on the current density used during discharge. The power density (delivered energy/discharge time) also depends on the current density and at the highest current densities investigated (1 mA/cm 2 ) it reaches 2.5 kW/kg of active electrode material.

173 citations


Patent
16 Sep 1997
TL;DR: In this paper, a phenolic resin powder, optionally combined with a carbon powder, is formed into a layer less than 001 inches thick; the temperature of the resin is increased at a rate of approximately 1 to 4°C per minute, thereby melting the resin into a porous network; the network is carbonized, hydrogenated in a hydrogen atmosphere and sulfonated
Abstract: A carbon material useful as an electrode in supercapacitors and a method for preparing the same In one method, a phenolic resin powder, optionally combined with a carbon powder, is formed into a layer less than 001 inches thick; the temperature of the resin is increased at a rate of approximately 01 to 4° C per minute, thereby melting the resin into a porous network; the network is carbonized, hydrogenated in a hydrogen atmosphere and sulfonated

149 citations


Journal ArticleDOI
U. Fischer1, R. Saliger1, V. Bock1, R. Petricevic1, Jochen Fricke1 
TL;DR: In this article, it was shown that carbon aerogels derived from these RF-aerogels have a small mesopore surface area, however an especially large micropore area.
Abstract: Due to their large specific surface area and their high electrical conductivity carbon aerogels are promising materials for electrodes in electrochemical double-layer capacitors (“supercapacitor”). The carbon aerogels were made via pyrolysis of resorcinol formaldehyde aerogels. The latter were prepared by supercritical and subcritical drying as well. The important findings of our investigation were, that the highest capacities of 46 F/cm3 were measured for samples with a density of about 800 kg/m3 pyrolyzed at 800°C. Also it was shown that RF-gels with molar resorcinol/catalyst ratios ≥1000 or higher can be dried subcritically without cracking or significant shrinkage. Carbon aerogels derived from these RF-aerogels have a small mesopore surface area, however an especially large micropore area. They provide electrical capacities which are most suitable for their use in supercapacitors.

118 citations


Journal ArticleDOI
TL;DR: In this paper, the performance characteristics of the capacitors have been studied using impedance analysis, linear-sweep voltammetry and charge-discharge methods, and the supercapacitors based on the activated carbon fabric have characteristically large values of overall capacitance of 360 −470 mF cm−2 [equivalent to single electrode capacitance 70 −90 F (g carbon)−1] with the proton conducting electrolyte.
Abstract: Proton and lithium ion conducting polymer electrolytes, based on poly(vinyl alcohol)–H3PO4 and poly(ethylene oxide)–LiCF3SO3 plasticised with poly(ethylene glycol), have been used in the construction of electric double layer capacitors with both high density graphite sheet and activated carbon fabric electrodes. The polymer electrolytes have room temperature ionic conductivities (ca. 10−4–10−3 S cm−1) that make them suitable for use in thin-film form in devices. The performance characteristics of the capacitors have been studied using impedance analysis, linear-sweep voltammetry and charge–discharge methods. The supercapacitors based on the activated carbon fabric have characteristically large values of overall capacitance of 360–470 mF cm−2 [equivalent to single electrode capacitance 70–90 F (g carbon)−1] with the proton conducting electrolyte. Systems based on lithium ion conducting polymer electrolytes, however, have a much lower capacitance of ca. 20 mF cm−2 (equivalent to a single electrode capacitance of ca. 4 F g−1).

70 citations


Patent
18 Nov 1997
TL;DR: In this article, a monolithic activated carbon plate or honeycomb electrodes (4, 6 and 8) made by extrusion, molding, or casting is described, and the carbon monolithic plates or honeycombs are fabricated from synthetic carbon precursor and active ingredient.
Abstract: The fabrication of activated carbon based supercapacitors. In particular, a monolithic activated carbon plate or honeycomb electrodes (4, 6 and 8) made by extrusion, molding, or casting is described. The carbon monolithic plates or honeycombs are fabricated from synthetic carbon precursor and active ingredient leading to superior electrical properties.

51 citations


Journal ArticleDOI
01 May 1997-Ionics
TL;DR: In this paper, the performance of polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF3SO3 plasticised with poly (ethylene glycol), was characterized by a linear sweep voltammetry, galvanostatic charge discharge methods and long term cycling tests.
Abstract: Types I and II solid state redox supercapacitors have been constructed using polypyrrole (pPy) and poly (3-methyl thiophene) (pMeT) conducting polymer electrodes with lithium ion conducting polymer electrolyte poly(ethylene oxide) (PEO)-LiCF3SO3 plasticised with poly (ethylene glycol) (PEG). The performance of the capacitors has been characterised by a.c. impedance, linear sweep voltammetry, galvanostatic charge-discharge methods and long term cycling tests. The asymmetric type II capacitors with p-doped pPy and pMeT electrodes give a capacitance value ∼ 2 mF cm−2 (equivalent to 18 Fg−1 of the total mass of the electrodes) and can be charged up to the voltage of 1.7 V. The symmetric type 1 capacitors of the configuration pPy | polymer electrolyte | pPy and pMeT | polymer electrolyte | pMeT show comparable values of capacitance but they are limited to the working voltage of <1.0 V.

46 citations


Proceedings ArticleDOI
09 Nov 1997
TL;DR: The commercial success of carbon-based ELCCs is due to their low cost, extremely high cycle life, and wide range of operating temperatures as discussed by the authors, where the properties mentioned above give ELCC advantages over rechargeable batteries.
Abstract: Electrochemical liquid double layer capacitors (ELCC) are energy storage devices with properties intermediate between batteries and electrolytic capacitors. The commercial success of carbon based ELCC is due to their low cost, extremely high cycle life, and wide range of operating temperatures. They are used mainly for power backup for electronic circuits where the properties mentioned above give ELCC advantages over rechargeable batteries. ELCC are a promising candidate for load leveling applications in electric vehicles and also pulse power applications. Nonaqueous electrolytes, such as organics, solid polymers, and inorganics offer higher energy densities due to the greater decomposition voltages. Advanced ELCC will likely use metal oxides or conductive polymers to provide higher energy and power densities than carbon based ELCC.

Journal ArticleDOI
TL;DR: In this article, the authors analyzed the performance of a series-connected capacitors and found that the reported data are generally not adequate to allow full capacitance characterization, in part due to the requirements o the derived equations, but often it is due to reported data that do not fully describe the performed experiment.
Abstract: In most electrochemical capacitor applications it is necessary to series a set of capacitors (cells) to obtain a single capacitor capable of operating at a desired voltage. Performance modeling of these devices has proven difficult because of their nonideal behavior and the need to series a large number of equivalent circuits. In this paper open literature data is analyzed using the equations derived herein. The analysis considers two different load situations, constant resistance and constant-power, for an arbitrary number of series-connected cells. Data from a device built by the Evans Electric Company,' and a prototype device are analyzed. In general, excellent agreement is obtained between the model results and the reported data. This agreement allows delineation of capacitor characteristics, at the cell level, that heretofore has not been available. However, it was found that reported data are generally not adequate to allow full capacitor characterization. In part this is due to the requirements o the derived equations, but often it is due to reported data that do not fully describe the performed experiment. In doing this analysis a hierarchy of equivalent circuits was used to provide a good data fit so as to determine capacitor cell parameters. The cell model proposed by Conway 2 and a transmission-line model were used. The dispersion of capacitance values, due to various manufacturing variables, was also modeled using a simple Beta distribution.

Proceedings ArticleDOI
09 Nov 1997
TL;DR: The double layer capacitor is a low voltage device exhibiting an extremely high capacitance value in comparison with other capacitance technologies of a similar physical size as mentioned in this paper, which is a promising device for certain niche applications.
Abstract: As an emerging technology in the area of energy storage, the double layer capacitor is a promising device for certain niche applications. The double layer capacitor is a low voltage device exhibiting an extremely high capacitance value in comparison with other capacitor technologies of a similar physical size. Capacitors with values in excess of 1500 F are now available. The maximum voltage allowable on these devices is 3 V, limited by the dissociation of the organic electrolyte. This high capacitance derives from the high surface of activated carbon electrodes, and the high capacitance per unit area observed at the chemical double layer. This paper serves as a summarization of experiments and the characterization of currently available double layer capacitor technologies. Capacitors from 10 F to 1500 F were examined, both aqueous and organic electrolyte technologies were utilized, and a range of commercially available devices were selected for study.

Journal ArticleDOI
TL;DR: In this article, it was shown that the structure of the current collector acts on the internal resistance of supercapacitors, and that the use of a three-dimensional current collector, such as metallic foam, results in an important decrease of the internal resistivity of the cell.

Proceedings ArticleDOI
09 Nov 1997
TL;DR: A summary of issues impacting the application of double-layer capacitors in various military and commercial industry situations is given in this paper, where the focus is on the performance parameters of the capacitors, which are the equivalent capacitance, the series resistance, and the parallel resistance.
Abstract: A summary of issues impacting the application of double-layer capacitors in various military and commercial industry situations is given in this paper. The focus is on the performance parameters of the capacitors, which are the equivalent capacitance, the series resistance, and the parallel resistance, and how these parameters impact specific applications. Some discussion of the need to form banks of capacitors is also given for the different applications. The use of power conversion systems to satisfy load constraints (e.g. constant voltage) is provided due to the common need for this equipment in many of the applications.

Proceedings ArticleDOI
19 Oct 1997
TL;DR: In this article, the authors define the technology issues for next generation energy storage capacitors, starting from the current state-of-the-art for large (over 5 kg) capacitors recently developed for modern pulsed power conditioning applications.
Abstract: Many different types of capacitors are available today, most being designed for mounting on circuit boards or other electronic equipment Generally these fall into the classes of ceramic, tantalum, electrolytic, or DC film capacitors Larger sizes of capacitors are used in applications such as motor drives and kilowatt to multimegawatt average power, power conditioning equipment These larger capacitors, operating to voltages in excess of 25 kilovolts, have traditionally been manufactured with paper or polypropylene films, or some combination therein, with or without a gas-excluding liquid impregnant This paper is focused on defining the technology issues for next generation energy storage capacitors, starting from the current state-of-the art for large (over 5 kg) capacitors recently developed for modern pulsed power conditioning applications

Proceedings ArticleDOI
24 Nov 1997
TL;DR: In this paper, the theory of aluminium electrolytic capacitors and their manufacturing process are discussed, and the electrical characteristics and their variation are outlined, as well as expected capacitor life.
Abstract: The author discusses the theory of aluminium electrolytic capacitors and their manufacturing process. The raw materials-aluminium, electrolyte, spacers and other materials-are described. The electrical characteristics and their variation are outlined, as is expected capacitor life. (6 pages)

Patent
03 Jun 1997
TL;DR: In this paper, a lead and bismuth/ruthenate and/or iridium system with the formula A2 B2-x Pbx!O7-y, where A=Pb, Bi, and B=Ru, Ir, and O
Abstract: A pseudo-capacitor having a high energy storage capacity develops a double layer capacitance as well as a Faradaic or battery-like redox reaction, also referred to as pseudo-capacitance. The Faradaic reaction gives rise to a capacitance much greater than that of the typical ruthenate oxide ultracapacitor which develops only charge separation-based double layer capacitance. The capacitor employs a lead and/or bismuth/ruthenate and/or iridium system having the formula A2 B2-x Pbx !O7-y, where A=Pb, Bi, and B=Ru, Ir, and O

Proceedings ArticleDOI
23 Feb 1997
TL;DR: In this article, the results of high frequency pulse discharge tests and inductance measurements on a single capacitor, and short circuit testing of an array of three double-layer capacitors during static discharge, single pulse discharge, and 100 Hz pulsed discharge are discussed.
Abstract: Recent developments in double-layer capacitor technology have resulted in devices with capacitance ratings of 470 F, with an equivalent series resistance as low as 4 m/spl Omega/ capable of repeatable current discharges over 570 A. This paper discusses the results of high frequency pulse discharge tests and inductance measurements on a single capacitor, and short circuit testing of an array of three double-layer capacitors during static discharge, single pulse discharge, and 100 Hz pulsed discharge.

Proceedings ArticleDOI
K. Harada, E. Sakai, K. Murata, S. Muta, K. Yamasaki 
24 Apr 1997
TL;DR: In this paper, the characteristics of electric doubie-layer capacitors (EDLCs) controlled by switching converters are analyzed and the maximum operating time, the energy availability versus the average output power of the system are analyzed.
Abstract: The characteristics of electric doubie-layer capacitors (EDLCs) controlled by switching converters are in& clear. The maximum operating time, the energy availability versus the average output power of the system are analyzed. The selection policies of the series and/or parallel combination of EDLCs and the type of switching converter, that is, buck, boost and buck-boost, are discussed. As a result, the inforination to make a practical design easy has been obtained.

Journal ArticleDOI
TL;DR: In this paper, the authors present test data from selected US Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements and discuss testing data obtained from recent prototype capacitors supplied by Maxwell Energy Products, Inc., SAFT America, Inc, Federal Fabrics-Fibers and the University of Wisconsin-Madison.
Abstract: Various electrochemical capacitors (ultracapacitors) are being developed for hybrid vehicles as candidate power assist devices for the fast response engine. The primary functions of the ultracapacitor are to level the dynamic power loads on the primary propulsion device and recover available energy from regenerative breaking during off-peak power periods. Ultracapacitors show promise toward being able to accept high regenerative pulses while exhibiting very high cycle life. This paper will present test data from selected US Department of Energy (DOE) supported ultracapacitor projects designed to meet the fast response engine requirements. Devices containing carbon, conducting polymers, and metal oxide electrode materials in combination with aqueous or organic electrolytes are being supported by the DOE. This paper will present and discuss testing data obtained from recent prototype capacitors supplied by Maxwell Energy Products, Inc., SAFT America, Inc., Federal Fabrics-Fibers and the University of Wisconsin-Madison. Constant-current, constant-power, leakage-current, and self-discharge testing of these various capacitors have been conducted. All devices were cycled between the rated charged voltage and zero volts for the constant-current tests and between the rated charged voltage and half that value for the constant-power tests.

Journal ArticleDOI
TL;DR: In this paper, the authors survey the published data of available electrode materials possessing high specific double-layer or pseudocapacitance and examine their reported performance data in relation to their theoretical expectations.
Abstract: Electrochemical capacitors, also called supercapacitors, are unique devices exhibiting 20 to 200 times greater capacitance than conventional capacitors. The large capacitance exhibited by these systems has been demonstrated to arise from a combination of the double-layer capacitance and pseudocapacitance associated with surface redox-type reactions. The purpose of this review is to survey the published data of available electrode materials possessing high specific double-layer or pseudocapacitance and examine their reported performance data in relation to their theoretical expectations.