A First Principles Approach to Develop a Dynamic Model of Electrochemical Capacitors

An alternative approach to develop a large-signal time-dependent model of a simple electrochemical capacitor is proposed. A simple planar electrochemical cell consisting of two metal electrodes separated by a sulfuric acid electrolyte layer is modeled from first principles. The model is a large-signal time-dependent model and is valid under constant temperature conditions. The model is based on the Poisson-Nernst-Planck electrodiffusion theory and physical attributes such as the impact of nonlinear polarization, the bulk electrolyte reactions, and changes to the transport coefficients are investigated. The system of partial differential equations has been solved using a finite element software package. The simulation results are compared with experimental results and discrepancies are discussed. The results indicate that the existing theory is not adequate in explaining the physics in the immediate vicinity of the electrode/electrolyte interface even though the general experimental and simulation results are in qualitative agreement with each other.