Showing papers on "Supercapacitor published in 1998"

Conducting polymer‐based electrochemical redox supercapacitors using proton and lithium ion conducting polymer electrolytes

Abstract: Polypyrrole-based solid-state redox supercapacitors have been constructed using proton and lithium ion conducting polymer electrolytes: poly(vinyl alcohol) (PVA)–H3PO4, and poly(ethylene oxide) (PEO)–LiCF3SO3 plasticized with poly(ethylene glycol) (PEG). The capacitors have been characterized using a.c. impedance, cyclic linear sweep voltammetry and galvanostatic charge–discharge methods. Redox capacitors based on polypyrrole show large values of capacitance (about 1·5–5·0 mFcm-2) (equivalent to a single electrode capacitance of 40–84 Fg-1 of polypyrrole) for both the electrolytes. The values of capacitance have been found to be stable up to 1000 charge–discharge cycles between 0 and 1·0 V. © 1998 Society of Chemical Industry

Keggin-type heteropolyacids as electrode materials for electrochemical supercapacitors

Abstract: An inexpensive electrochemical capacitor system with an asymmetric configuration is demonstrated. The system includes heteropolyacids and a proton-exchange polymer membrane. Heteropolyacid electrodes show facile redox processes and host large amounts of easily accessible mobile protons required for charge balance. The proton-conducting polymer electrolyte provides chemical stability of the heteropolyacids which would otherwise dissolve into the aqueous liquid electrolyte. In this context, H 3 PMo 12 O 40 .nH 2 O/Nafion 117/H x RuO 2 .nH 2 O is a model system. A very reversible specific capacitance of 112 F/g and an energy density of 36 J/g, based on the active materials only, were measured for the optimized cold-pressed single cell with an operating voltage of 0.8 V. This approach can be extended to other transition-metal oxides chemically unstable in aqueous solution that have mixed-valence redox energies between the highest occupied and lowest unoccupied molecular orbital of the electrolyte. An electronic energy diagram for advanced design considerations is presented.

Supercapacitor having a non-aqueous electrolyte and an active carbon electrode

Abstract: The invention relates to a supercapacitor having a non-aqueous electrolyte and two carbon electrodes each containing a binder and an electrochemically active material constituted by active carbon having a specific surface area greater than about 2000 m 2 /g. The binder has a mixture of carboxymethylcellulose and a copolymer of styrene and butadiene.

Electrolytic or film capacitors

Abstract: Over the last eight years, significant improvements have been made in the field of polypropylene capacitors. Thinner films and more sophisticated metallization techniques have allowed the range of operating voltages to be lowered to some hundreds of volts. The upper voltage area of the electrolytic capacitors is now covered by the polymer film capacitors. This overlapping is examined through a comparison of the main electrical criteria.

Supercapacitors and Batteries

Abstract: Comparisons are made between the material requirements for supercapacitor electrodes and the cathode of a lithium-ion battery. The performances of the battery cathodes Li1+xFe2(SO4)2(PO4) and Li1+5 VMoO6 are compared to those for supercapacitor electrodes operating with 5.3 M H2SO4, Nafion 117, or 2 M KCl aqueous solution at pH 6.7. The use of a KCl aqueous electrolyte at mild pH allows stabilization of amorphous, hydrated electrode materials such as a-MnO2•nH2O that are not stable in 5.3 M H2SO4 or with Nafion 117. However, the larger K+ ion appears to reduce by a factor of three the theoretical capacity attainable with H+ ions.

Plastic power sources

Abstract: Lithium ion polymer batteries and laminated solid-state redox supercapacitors, formed by placing a highly conducting gel-type membrane electrolyte between a graphite film and a composite cathode film and between a poly(pyrrole)–poly(aniline) electrode combination, respectively, have been fabricated and tested The preliminary results are encouraging in suggesting that these plastic power sources may be particularly advantageous for mobile electronic products and for zero emission electric vehicles

Characterization of carbon-based electrochemical capacitor technology from Maxwell Energy Products, Inc.

Abstract: The electrochemical capacitor devices described in this report were deliverables from the US Department of Energy--Idaho Operations Office (DOE-ID) Contract No. DE-AC07-92ID13404 as part of the US Department of Energy`s (DOE) High Power Energy Storage Program. The Idaho national Engineering and Environmental Laboratory (INEEL) has responsibility for technical management, testing, and evaluation of high-power batteries and electrochemical capacitors under this Program. The DOE has developed various electrochemical capacitors as candidate power assist devices for the Partnership for a New Generation of Vehicles (PNGV) fast response engine requirement. This contract with Maxwell Energy Products, Inc. (Maxwell) was intended to develop a high-energy-density, high-power-density ultracapacitor that is capable of load leveling batteries in electric vehicles. The performance criteria for this device are delivery of 5 W {center_dot} h/kg of useful energy that can be used by the vehicle at an average power rating of 600 W/kg. The capacitor must also have an overall charge/discharge efficiency of 90%, and a useful life of more than 100,000 discharge cycles. The deliverables reported on here are those prepared by Maxwell Energy Products, Inc. at various stages of their developmental program. Deliverables were sent to the INEEL`s Energy Storage Technologies (EST) Laboratory for independent testing and evaluation. This report describes performance testing on three sets of capacitors delivered over a two year period. Additional testing has been done on Set {number_sign}2 described herein, as well as on an additional deliverable from Maxwell. These tests results will be documented in a follow-up report.

Comparison of the origin of high capacitance at nickel and/or carbon aqueous electrolyte interfaces and its uses in the development of potassium ion intercalation based super capacitor

Abstract: This paper deals with the origin of high capacitance at nickel/aqueous alkaline carbonate and carbon/aqueous alkaline carbonate electrolyte interfaces and the consequent success achieved in the development of nickel and carbon super capacitors. Aminoguanidine bicarbonate (AGBC) has been used as an addition agent in the electrolyte to enhance the capacity. The basic mechanism of charge storage in these capacitors is the intercalation and deintercalation of K/sup +/ ion at both nickel/nickel oxide and carbon electrodes. The electrolyte being aqueous potassium carbonate solution. Intercalation-deintercalation phenomenon at these electrodes has been confirmed by XRD studies, which proves the decrease in "2/spl theta/" values with an attendant increase in "d" values and also by transmission electron microscopy (TEM). Further the capacity values calculated from cyclic voltammetry (CV) are found to be high, the values ranging from 3400 to 6800 /spl mu/F.cm/sup -2/ for nickel and from 14700 to 32900 /spl mu/F.cm/sup -2/ for carbon. Dissolved oxygen and AGBC content are found to have effect on the capacity values. Individual capacitors and capacitor banks fabricated using the nickel and carbon electrodes, and the aqueous alkaline carbonate solution have been tested for their performance. The most important characteristic of these capacitors is that their voltage windows are greater than 1.2 V. This comparative study confirms that both nickel and carbon are prospective candidates for electrodes in alkaline media. For use in electrical double layer (EDL)/super capacitors in the presence or absence of oxygen and/or AGBC.

Development of carbon metal oxide supercapacitors by electroless deposition

Abstract: It is shown that hybrid metal oxide-carbon supercapacitors possess superior energy and power densities as compared to bare carbon. An electroless deposition process was used to synthesize ruthenium coated activated carbon. The effect of electrochemical oxidation and temperature treatment on the material performance has been studied extensively. Maximum utilization of 900 F/g of Ru was obtained with 0.4 μm thin Ru film coated on activated carbon. Electroless deposition leads to the formation of thin amorphous films, which increase the specific capacitance of Ru dramatically.

Materials for electrochemical energy storage and conversion II--batteries, capacitors, and fuel cells : symposium held December 1-5, 1997, Boston, Massachusetts, U.S.A.

Abstract: Our energy-hungry world increasingly relies on new methods to store and convert energy for portable electronics, as well as environmentally friendly modes of transportation and electrical energy generation. The development of high-performance power sources are intimately linked to the availability of advanced materials. Designing batteries and capacitors with higher specific energy and power, longer cycle life and rapid charge/discharge rates requires a deeper understanding of the relationship between materials properties and performance. Fuel cells, which offer the potential for clean, efficient conversion of chemical energy to electrical energy, are hampered by high cost and performance problems which can be resolved by new materials and processing techniques. Advanced batteries such as lithium-ion and nickel-metal hydride offer the potential for improved performance if low-cost materials can be developed. This book shares research and highlights the importance of materials in energy conversion technologies. Topics include: rechargeable batteries; lithium-ion rechargeable batteries - modelling; fuel cells; lithium-ion rechargeable batteries - cathode materials; battery electrolytes, interfaces and passive films; lithium-ion rechargeable batteries - anode materials and supercapacitors.