Chemo-Mechanical Study Of Dislocation Mediated Ion Diffusion In Lithium-Ion Battery Materials

A mechanically coupled diffusion model combined with finite element formulation is developed to study the influence of dislocations on ion diffusion in lithium-ion batteries. The dislocation is modeled by the regularized eigenstrain based on a non-singular continuum dislocation theory. The model is validated with the analytical solution of the stress field of edge dislocations and the solution for the stress-dependent equilibrium concentration around the dislocation. Simulation results on LiMn2O4 demonstrate strong ion enrichment and depletion on the tensile and compressive sides of an edge dislocation, respectively. A stronger influence of the edge dislocation on diffusion is found at a lower state-of-charge, which verifies the experimental observation reported in the literature. The diffusion-induced stress compensates partially the stress field of the edge dislocation and is ascertained to have a state-of-charge dependency. The existence of dislocation does not introduce obvious mobility anisotropy in the bulk material but it results in local mobility heterogeneity around the dislocation. A three-dimensional simulation of the diffusion along the edge dislocation line reveals that the pipe diffusion can be initiated or accelerated on the tensile side of the edge dislocation. Published under an exclusive license by AIP Publishing.