Evaluating the Effects of Grain Anisotropy on the Effective Chemo-Mechanical Properties of Secondary Particles in Lithium-Ion Batteries

The microstructure of positive electrode polycrystalline particles (secondary particles) directly affects their diffusion and mechanical properties. In this study, a quantitative evaluation of the effects of grain anisotropy on the overall diffusion and mechanical properties of secondary particles is conducted, which is based on a simplified 2D polycrystalline model with hexagonal anisotropic grains (primary particles) with different distributed orientations. The research results indicate that consistent grain orientation can promote the uniform distribution of lithium ions, while lower diffusion anisotropy can promote the diffusion of lithium ions along shorter paths, thereby improving the diffusion properties of secondary particles. Lower elastic anisotropy of grains and a grain orientation distribution with a 60° angle favor maintaining the macroscopic elastic isotropy of secondary particles. The study also found that when the number of grains is large enough and the orientation distribution is sufficiently random, secondary particles exhibit macroscopic diffusion isotropy and elastic isotropy.