ELECTRIC DOUBLE LAYER CAPACITORS BASED ON PHOSPHATE GLASS-DERIVED HYDROGELS PREPARED BY A CHEMICOVECTORIAL METHOD

New types of proton-conducting phosphate hydrogels were prepared utilizing a chemicovectorial effect. Fine-sized magnesium metaphosphate, calcium metaphosphate, or zinc metaphosphate glass powders reacted with distilled water to hydrate immediately, resulting in formation of the hydrogels with high viscosity. 31 P MAS-NMR spectra showed that the hydrogels include orthophosphates and long-chain phosphates coordinated to H+ or M2+ (M=Mg, Ca, Zn) ions; no significant differences in their structures among the hydrogels were shown. Electric double layer capacitors (EDLCs) with electrolytes consisting of the hydrogels showed no oxidation-reduction processes in the range of 0•`1 V and high rate charge-discharge capabilities. The EDLCs showed excellent self-discharge behaviors; they retained high open circuit potentials of the EDLCs after charging. EDLC consisting of zinc phosphate hydrogel showed much higher (3•`6 times higher) specific capacity than those of magnesium phosphate and calcium phosphate hydrogels under the present condition. The possibility as an EDLC electrolyte may be related to polarizability of the hydrogels. (Received June 23, 2004; Accepted Ausust 30, 2004)