Effect of Irreversible Electrochemical Reaction on Diffusion and Diffusion-Induced Stresses in Spherical Composition–Gradient Electrodes

Abstract

Abstract Composition–gradient electrodes have been proved to have excellent electrochemical performances. The effect of irreversible electrochemical reaction on diffusion and diffusion-induced stresses in such electrodes is investigated. The diffusion equation and mechanical equation considering the electrochemical reaction and the heterogeneous factors are derived, and the distributions of lithium (Li) concentration and stresses in a spherical electrode are obtained under potentiostatic charging. The results indicate that the electrochemical reaction will slow down the diffusion process and enhance the stresses of the electrode. However, the heterogeneous factors of the electrochemical reaction could provide a positive effect on the stresses, which means that the heterogeneous factor is conducive to avoid capacity fading of the battery. The results suggest that the composition–gradient electrodes could be designed to have a decreasing transition form of forward reaction rate and an increasing transition form of the difference of atomic volume between reactants and the reaction product.