Abstract
Solid electrolytes consisting of complexes of poly(ethylene oxide)‐grafted poly(methyl)‐methacrylate (PEO‐PMMA) and tetraalkylammonium salts (tetrabutylammonium perchlorate, tetraethylammonium perchlorate, and tetraethylammonium tetrafluoroborate) have been investigated for electric double‐layer capacitors. The composites obtained showed high ionic conductivity (about 10−4 S cm−1 at 298 K). When the PEO‐PMMA‐tetraethylammonium tetrafluoroborate composites were used in solid‐state electric double‐layer capacitors with activated carbon‐fiber cloths as polarizable electrodes, the capacitors showed charge/discharge behavior with large values of capacitance. The maximum capacitance was ca. 0.57 F/cm2 (of each electrode), which was comparable to that of usual liquid‐type electric double‐layer capacitors.