Polyaniline doped with HCl (Pani-HCI) and LiPF6 (Pani-LiPF6) are prepared and used as the active electrode material of symmetric redox supercapacitors. The system using Et4NBF4 as an electrolyte solution has lower internal resistance and larger specific discharge capacitance, and thus, it is suitable for use in a polyaniline redox supercapacitor. The capacitance of Pani-HCl decreases during similar to400 cycles and then becomes constant at similar to40 F g(-1). On the other hand, the polyaniline electrode doped with lithium salt like LiPF6 shows a specific discharge capacitance of similar to107 F g(-1) initially and similar to84 F g(-1) at 9000 cycles.