STUDIES ON ALL-SOLID-STATE ELECTRIC DOUBLE-LAYER CAPACITORS USING PROTON AND LITHIUM ION CONDUCTING POLYMER ELECTROLYTES

Proton and lithium ion conducting polymer electrolytes, based on poly( vinyl alcohol)-H3PO4 and poly(ethylene oxide)-LiCF3SO3 plasticised wit h poly(ethylene glycol), have been used in the construction of electri c double layer capacitors with both high density graphite sheet and ac tivated carbon fabric electrodes. The polymer electrolytes have room t emperature ionic conductivities (ca. 10(-4)-10(-3) S cm(-1)) that make them suitable for use in thin-film form in devices. The performance c haracteristics of the capacitors have been studied using impedance ana lysis, linear-sweep voltammetry and charge-discharge methods. The supe rcapacitors based on the activated carbon fabric have characteristical ly large values of overall capacitance of 360-470 mF cm(-2) [equivalen t to single electrode capacitance 70-90 F (g carbon)(-1)] with the pro ton conducting electrolyte. Systems based on lithium ion conducting po lymer electrolytes, however, have a much lower capacitance of ca. 20 m F cm(-2) (equivalent to a single electrode capacitance of ca. 4 F g(-1 )).