Properties of Electric Double‐Layer Capacitors with Various Polymer Gel Electrolytes

Polyethylene oxide (PEO), polymethyl methacrylate (PMMA), and polyacrylonitrile (PAN) based gel electrolytes with a mixture of ethylene carbonate and propylene carbonate as plasticizer and lithium perchlorate were used to fabricate an electric double‐layer capacitor (EDLC). The performance of EDLCs with these gel electrolyes was investigated by using isotropic high‐density graphite electrodes. The ion conductivities of various gel electrolytes were of the order of 10 −4 to 10 −3 S cm −1 , and they decreased in the order PAN > PEO > PMMA at ambient temperature. Capacitances approaching the value of EDLCs using organic liquid electrolyte, 20 mF cm −2 , with an isotropic high‐density graphite electrode were obtained in PAN and PMMA gel electrolytes. The EDLC with PMMA‐based gel electrolyte showed good charge‐discharge behavior over 10 4 cycles at a charge potential of 3.0 V.