To obtain a superior withstanding voltage and a long type reliability by specifying the glycol content in an electrochemical capacitor electrolyte soln.
A mixture of coconut husk type activated carbon powder obtained by activating a carbonaceous substance with steam, acetylene black, and polytetrafluoroethylene is kneaded, pressure formed into a disc compact to be a polarizable electrode 2. This forming step is repeated to obtain another polarizable electrode identical in compsn. and shape, the obtained two compacts are dried and left cold and impregnated with an electrolyte soln. A separator 3 is sandwiched between the two polarizable electrodes 2 impregnated with the electrolyte soln., and all are caulked and sealed through a gasket in a case to obtain an electrochemical capacitor. The propylene glycol content of the electrolyte soln. contg. trimethyl-ethyl ammonium tetrafluoroborate dissolved in a propylene carbonate solvent is 100 ppm or less.
TAKEUCHI SACHIE
OURA YASUSHI
TAKEHARA MASAHIRO
CHOKAI AKIKO
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