Impact of mechanical stiffening and softening on the spatial distribution of lithium ions in spherical electrode particle under galvanostatic charging

Abstract

This article investigates the lithiation of low-expansion electrode particles with concentration-dependent properties. The conventional electrochemical coupled stress equations do not take into account concentration dependency, especially for particles with a low volume of expansion, as they are assumed to have no impact on the lithium-ion (Li-ion) migration. However, considerable changes are observed in the present study when this factor is included. The Li-ion concentration gradient is observed to decrease with stiffening and increase with softening in an electrode particle. The stresses at the center of the particle increase with stiffening and reduce with the softening. It is observed that the effect of concentration-dependent elastic modulus on the concentration gradient of lithium ions at the surface of the particle is more prominent at higher charging rates. The stresses in the electrode particle are observed to increase in proportion to an increase in the charging rate up to a critical limit beyond which its magnitude reduces.