An electrolyte, N,N'-1,4-diethyl, triethylene, and diamine tetrafluoroborate dissolved in glutaronitrile, was developed and investigated in a symmetrical supercapacitor using activated carbon as electrodes (active carbon vertical bar active carbon). The electrochemical performance of the simulated supercapacitor was examined using ac impedance, cyclic voltammetry, and constant current charging/discharging tests. According to the results, the electrochemical window of the supercapacitor could reach 4.2 V, and its single-anode specific capacitance could reach 245.3 F g(-1). The supercapacitor also has better capacitance characteristics, reversibility, and cyclic characteristics. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3477934] All rights reserved.