A Mathematical Model of an Electrochemical Capacitor with Double‐Layer and Faradaic Processes

A mathematical model of an electrochemical capacitor with hydrous ruthenium oxide (RuO 2 ·xH 2 O) electrodes including both double-layer and surface faradaic processes is developed to predict the behavior of the capacitor under conditions of galvanostatic charge and discharge. The effect of RuO 2 ·xH 2 O particle size is studied and shows that the smaller the particles the better the performance because of the increased surface area per unit volume or mass. The model also predicts that the faradaic process increases significantly the energy per unit volume of the capacitor for power densities of 100 kW/L or less.