An all-solid supercapacitor has been fabricated using polyaniline (Pani) and sulfonated poly(ether ether ketone) (SPEEK). A composite electrode is made from chemically-synthesized Pani, SPEEK, electronically conducting carbon black and polytetrafluoroethylene (PTFE). SPEEK acts as both separator and electrolyte. The unit cell consists of two electrodes made from a p dopable Pani composite electrode separated by a SPEEK membrane with a thickness of 50 mum. As the electrodes of the capacitor are made from same p dopable Pani material, the cell is a type I (p-p) capacitor. The cell characteristics are studied using cyclic voltammetry, charging-discharging, and impedance analysis. The unit cell capacitance is 0.6 F, which corresponds to 27 F per g of the active polymer material. (C) 2003 Elsevier B.V. All rights reserved.