The electrical conductivity of polyaniline films doped with 1 M LiBF4 is similar to0.082 S/cm. The discharge capacity is increased with cycling and then saturates at more than 15 cycles. We obtained a saturated discharge capacity of about similar to 40 mAh/g, which is only about 38% of the theoretical capacity. The solution conductivity is continuously decreased as the Li salt concentration is reduced. The Li salt concentration in the electrolyte and the concentration of Li salt as a doping agent affects the charge/discharge reaction. By the analysis of de conductivity, XPS, and ESR data, the charging mechanism is explained by a charge separation mechanism which depends on the concentration of ionic salt in the electrolyte. (C) 2000 Elsevier Science B.V. All rights reserved.