Measurement and modelling of the high-power performance of carbon-based supercapacitors

Supercapacitors are now being looked at for use in higher power applications such as mobile telecommunications and hybrid electric vehicles. We have examined two different supercapacitors, one is a commercial sample and the other is a supercapacitor of our own design. Four different testing methods including Impedance Spectroscopy, Constant Current Charging, Cyclic Voltammetry and Power Cycling were applied to each supercapacitor and the results are reviewed. Parameter values obtained from Impedance Spectroscopy are excellent for comparing supercapacitors under equilibrium conditions but correlate poorly with data obtained from the more useful Power Cycling Charts (PCC). The choice of the current step size in Constant Current Charging and the scan rate in Cyclic Voltammetry has a large bearing on the results obtained from these techniques. The strong voltage dependence of the parameters for the commercial sample prevented analysis using Cyclic Voltammetry. It was also clearly demonstrated by Power Cycling that the commercial sample had the poorer power performance of the two supercapacitors tested. It is concluded that for high-powered applications such as telecommunications and wireless protocols the most useful comparison of supercapacitor capability is through the PCC. (C) 2000 Elsevier Science S.A. All rights reserved.