A statistical RVE model for effective mechanical properties and contact forces in lithium-ion porous electrodes

Abstract

A statistical representative volume element for a cathodic NMC active porous materials is developed as a periodic face-centered-cubic structure. Finite element analyses (FEA) are conducted to calculate effective elastic properties and contact force distributions for various numbers of particle–particle and binder-particle contacts. The statistics for the RVE is attained through simulations of stochastic distributions of contact conditions. The variations of effective properties with changing particle–particle and binder-particle contacts are compared to experimental results in the literature. The stiffening behavior at compressive loading is correlated with increasing interparticle connections in the RVE. The average values and the statistical distribution of particle–particle and binder-particle contact forces that result from particle swelling are as well investigated. The significance of contact force distributions, for both particle–particle and binder-particle contacts, on potential particle cracking and binder debonding is addressed. It is noted that particle–particle contact forces appear that are 4–5 times larger than their corresponding average values. Conclusions drawn from differences in average contact forces between particle–particle and particle-binder contacts as well as normalized standard deviations of contact forces are utilized to improve a previously developed analytical model for effective stiffness properties and contact forces. Excellent agreements are found in comparisons to the numerical simulations.