Analysis of Porous Electrodes with Sparingly Soluble Reactants

Abstract

A model is developed for the operation of a porous electrode in which slightly soluble reactants are present. Numerical techniques are used to predict current distribution and total electrode polarization for the case of a uniform porous structure. This technique is extended to the case where nonuniformities in reactant conversion are produced by a nonuniform current distribution within the electrode. In addition, a simulation of electrode behavior on repeated cycling is obtained. The implications of nonuniform reactant conversion and mass transfer limitations for real battery electrodes are discussed. The results of the numerical calculations indicate that diffusion‐limited currents within the porous electrode are possible for certain input parameters. The high polarization at constant current corresponding to a limiting current may be obtained after some time of discharge, but before all of the theoretically available active material is used. In the cycling simulation, significant changes in the relative distribution of reactants and products were observed as a function of depth in the electrode. These changes caused differences in the total electrode polarization from cycle to cycle.