Composites of polyaniline and V2O5 were prepared by casting on a Ni electrode substrate an N-methylpyrrolidinone solution containing dissolved polyaniline in its reduced state and dispersed crystalline V2O5 powder. Charge-discharge tests of the as-prepared composites showed that redox reactions of both polyaniline and V2O5 particles took place, and a utilization of V2O5 higher than 0.9 was obtained, indicating that polyaniline worked not only as an active material but also as a conducting matrix for V2O5 particles. The effects of charge-discharge current densities, the amount of V2O5 in the composite films, and the film thickness on the charge-discharge properties were investigated in detail. Elemental analyses of the composite films revealed that Li+ was the primary participant involved in the charge-discharge reactions of the composites, suggesting that V2O5 particles were negatively charged during the course of preparation of the composites and served as charge compensators for positive charges generated on the polyaniline in its oxidized state.