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. (C) 2011 Elsevier Ltd. All rights reserved.