Electrochemical Properties of Asymmetric Supercapacitors in Potassium Hydroxide Electrolyte

Abstract

Three kinds of activated carbons were prepared from Taixi anthracite by NaOH activation. As-obtained activated carbons were adopted as electrode materials to construct asymmetric and symmetric supercapacitors. The electrochemical properties of as-constructed supercapacitors in aqueous electrolyte (3.0M KOH) were investigated. Results show that the asymmetric supercapacitor assembled with activated carbon of a higher specific surface area (SBET) as the positive electrode exhibits better ion diffusion behavior and higher cell gravimetric specific capacitance (Cg). This is different from the case in non-aqueous system, mainly because pseudo-capacitance rather than double-layer capacitance has a more important effect on Cg in the aqueous electrolyte. Namely, the wettability and pseudo-capacitance of activated carbons decrease with increasing mass ratio of NaOH to anthracite, which is more prominent for activated carbons used as negative electrode materials.