Non-aqueous polymeric gel complexes composed of poly(ethylene oxide)-modified polymethacrylate (PEO-PMA) dissolving anhydrous H3PO4 have been examined as solid electrolytes of electrochemical capacitors. High ionic conductivity of 10(-3) S cm(-1) (at 70degreesC) was obtained for non-aqueous gel systems based on PEO-PMA with proper amounts of organic plasticizers. The ionic conductivity depended on the composition of the gel, especially on the content of the dopant H3PO4. A test cell of the electric double layer capacitor (EDLC) was assembled using the present gel electrolyte with activated carbon fiber (ACF) cloth electrodes. It gave as high capacity as that obtained for the capacitor using an aqueous liquid electrolyte. High rate capability was obtained for the cell operating at 90degreesC. (C) 2004 Elsevier Ltd. All rights reserved.