A comparative study of activated carbon-based symmetric supercapacitors in Li2SO4 and KOH aqueous electrolytes

Abstract

In this work, we have prepared activated carbon (AC)-based symmetric supercapacitor (SC) using Li2SO4 aqueous electrolyte instead of H2SO4 and KOH and obtained a device with an improved cell voltage window (CVW) of 0 − 1.6 V from 0 to 1.0 V. The SC using KOH electrolyte is also fabricated for comparison. The electrochemical characteristics of SCs such as cyclic voltammetry (CV), galvanostatic charge–discharge, electrochemical impedance spectroscopy (EIS) and cycle stability are investigated systematically. The possible redox reactions of electrodes that occurred in Li2SO4 and KOH electrolytes that restrict the CVWs are discussed. The results indicate that in the case of Li2SO4, the AC electrode can deliver a specific capacitance of 210 F g−1 at a current density of 0.1 A g−1, and the energy density of capacitor can be as high as 16.9 Wh kg−1 at 200 W kg−1 (based on the total mass of active electrode materials), 80% higher than that in the case of KOH.