Analytic Solutions and Experimental Data for Cyclic Voltammetry and Constant-Power Operation of Capacitors Consistent with HEV Applications

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Abstract
We derive and implement analytic solutions for the description of cyclic voltammetry (CV) and constant-power operation of high-power-density supercapacitors based on carbon electrodes and nonaqueous solvents. An equivalent circuit, consisting of a resistor in series with a capacitor, is used to capture the supercapacitor behavior. A single dimensionless group governs the performance of the system during cyclic voltammetry; we vary the frequency of the cycle over the range of interest for hybrid-electric vehicle (HEV) applications, which gives rise to current and potential variations commensurate with HEV applications as well. Constant-power operation is of direct interest for vehicle integration: for energy management of HEVs, one wants to know the available energy and the energy efficiency as a function of the demanded power, and our analytic solutions for charge and discharge address this issue directly. For both CV and constant-power operation, closed-form analytic solutions are compared with experimental data.