Maximum Effective Capacity in an Ohmically Limited Porous Electrode

Abstract

For large reaction rate constants and negligible change in solution composition, the performance of a porous electrode with solid reactants is governed by the ohmic potential drop within the matrix and solution phases. The cell potential changes with time, at constant current, as the reactants are consumed. Equations are developed which describe this time dependence as a function of electrode porosity and thickness, the electrolyte and solid phase conductivities, specific ampere‐hour capacity, separator conductivity and thickness, and current density. These then yield the values of electrode porosity and electrode thickness so as to maximize the capacity for discharge to a given cutoff potential. Treatment of the porous electrode is presented as an example.