DEVELOPMENT OF ELECTROCHEMICAL CAPACITORS INCORPORATING PROCESSABLE POLYMER GEL ELECTROLYTES

The behavioural characteristics of two classes of electrochemical supe rcapacitors, based respectively on porous (ie activated) carbon electr odes and polypyrrole-coated carbon electrodes, have been compared by c yclic voltammetry in order to identify the electrode/electrolyte combi nations suitable for high power density applications. It is shown that the large specific capacitances of activated carbon electrodes (in Fg (-1)) are not accessible during high rates of charge/discharge because ions from the electrolyte are slow to reach the internal surfaces of the carbon electrodes. Much larger charge/discharge rates (and hence p ower densities) are achievable with polypyrrole-coated carbon electrod e/polymer electrolyte combinations. These concepts are now being incor porated into working prototypes for ultimate scaleup to meet the needs of electric vehicle applications. (C) 1998 Published by Elsevier Scie nce Ltd. All rights reserved.