Chemo-Mechanical Behavior of Highly Anisotropic and Isotropic Polycrystalline Graphite Particles During Lithium Intercalation

Abstract

This paper develops a continuum model that predicts mechanical response of polycrystalline graphite anode particles during charging of a Li-ion battery. The computational study is particularly concerned with the extreme anisotropy associated with the graphite crystal structure. Polycrystalline particles can be synthesized to have either crystallites that are randomly oriented or have nearly parallel basal planes. The anisotropic Li diffusion coefficients and mechanical properties are derived from published density-functional theory models. The multiphysics model fully couples the Li diffusion and the mechanical response, including the effects of local hydrostatic stress gradients on Li diffusion flux. The study considers a range of charging rates. The predicted stresses are generally below fracture criteria. However, the significant particle deformations could potentially influence solid-electrolyte interface (SEI) stability.