The purpose of this study is to research and develop carbon composites for this electric double-layer capacitor (EDLC) film. We investigated cyclic voltammetry, ac impedance response, leakage current and charge/discharge cycling of carbon composite electrodes in polymer electrolyte. The radius of the AC electrode semicircle adding 5 wt.% KS-6 was very Small compared with that of the AC electrode alone. The discharge capacitance of the AC composite with 5 wt.% KS-6 in the 1st and 10th cycles was 100 and 94 mF cm(-2), respectively, at a current density of 0.1 mA cm(-2). At the 1000th cycling, the highest specific capacitance, 4.3 F g(-1), was measured for an activated carbon composite with 5 wt.% KS-6 in PVDF-PC-EC-LiClO4 electrolyte. The carbon composite electrode performed with good cycliability over 1000 cycles and with 100% coulombic efficiency. (C) 2000 Elsevier Science Ltd. All rights reserved.