Improvement of the performance for quasi-solid-state supercapacitor by using PVA–KOH–KI polymer gel electrolyte

A quasi-solid-state supercapacitor was assembled by using alkaline polyvinyl alcohol and potassium iodide (PVA–KOH–KI) as gel electrolyte and activated carbons electrodes. The electrocapacitive properties of the supercapacitor were evaluated by cyclic voltammetry, galvanostatic charge–discharge, and electrochemical impedance spectroscopy techniques. The introduction of KI increases the ionic conductivity of electrolyte, and improves the pseudocapacitance of the electrode. The specific capacitances of the supercapacitor is 236.90 F g⁻¹, increasing by 74.28% compared to the PVA–KOH system at the same current density. The energy density and power density of the supercapacitor reach 7.80 Wh kg⁻¹ and 15.34 kW kg⁻¹, respectively. In addition, the supercapacitor exhibits excellent cycle-life stability.