Microstructural analysis and mathematical modeling of electric double-layer supercapacitors

For hybrid-electric vehicle applications, supercapacitors show promise for providing low cost per unit power, high-efficiency energy storage, substantially temperature-invariant operation, and high cycle life (potentially equating to one supercapacitor pack per vehicle lifetime). Here we provide a microstructural and mathematical analysis for the characterization of a relatively high specific energy supercapacitor. The governing equations and the boundary conditions are generalized so that the cell can be modeled using a current, potential, or power excitation source. An Appendix clarifies the role of binary-electrolyte diffusion. The overall analysis allows one to determine the optimal target operating voltage for hybrid vehicle operation, calculate the available energy vs. available power for the system, and clarify the electrode utilization through the examination of the stored charge as a function of position. (c) 2005 The Electrochemical Society.