Study on electrochemical performance of activated carbon in aqueous Li2SO4, Na2SO4 and K2SO4 electrolytes

The electrochemical performances of activated carbon (AC) in 0.5 mol/l Li2SO4, Na2SO4 and K2SO4 aqueous electrolytes were investigated. The cyclic voltammetric results at different scan rates show that the rate behaviors of AC in the three electrolytes improve in the order of Li2SO4 < Na2SO4 < K2SO4. This improvement can be mainly ascribed to the following two reasons: (1) the decreasing equivalent series resistance in the order of Li2SO4 > Na2SO4 > K2SO4, which is the main factor influencing the maximum output power, and (2) the increasing migration speed of hydrated ions in the bulk electrolyte and in the inner pores of AC electrode in the order of Li+ < Na+ < K+. Their cycling behaviors do not show any differences in capacitive fading. The above results provide valuable information to explore new hybrid supercapacitors.