Abstract: The electrochemical behaviors of ferrocene (Fc)-containing ionic liquid [BMIm]BF4 were investigated in a system, which used ferrocene-containing ionic liquid as electrolyte, porous carbon as electrode materials. The cyclic voltammetry and constant current charge-discharge results indicated that redox reaction of Fc happened in the porous carbon, and which was a diffusion-controlled, highly reversible redox reaction. The average specific capacitance of 0.01 mol·L-1 [BMIm]BF4/Fc at a current density of 1 mA·cm-2 was 163 F·g-1, 63% higher than that of pure [BMIm]BF4. The increase of average specific capacitance indicates that the faradic pseudocapacitance associated with Fc species in the redox reactions has a considerable contribution to the total capacitance of ECs (electrochemical capacitors). At the same time, it shows a power density of 400 W·kg-1 as well as energy density of 37.5 Wh·kg-1 approaching the level of a practical battery.

Key words: Ionic liquid, Electrochemical capacitors, Faradic pseudocapacitance, Redox