New Electric Double‐Layer Capacitors Using Polymer Solid Electrolytes Containing Tetraalkylammonium Salts

Abstract

Solid electrolytes consisting of complexes of poly(ethylene oxide)-grafted poly(methyl)-methacrylate (PEO-PMMA) and tetraalkylam-monium 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/cm 2 (of each electrode), which was comparable to that of usual liquid-type lectric double-layer capacitors. Polymer solid electrolytes have attracted strong interest in appli-cations for devices such as batteries, because polymeric solid elec-trolytes can lead to high reliability without leakage of the electrolyte, high energy density, and an ultra-thin form. 13 However, the applica-tion of polymer solid electrolytes to electric double-layer capacitors have so far been limited, 4while there have been many reports on such capacitors containing liquid electrolyte systems. 51 ~ The diffi-