The Influence of Crystallographic Orientation on the Chemo-Elastic Response of Reconstructed Li_<i>x</i>CoO₂Cathode Particles

Abstract

This work investigates the inhomogeneous and anisotropic, chemo-elastic response of a particular, but representative, reconstructed 3.6-μm LixCoO2 single-crystal cathode particle from a Li-ion battery. The results are based on a three-dimensional computational model that represents coupled electrochemical and mechanical response throughout the lithiation process (0.50 ⩽ x ⩽ 0.94) associated with a 1C galvanostatic discharge. The study focuses on the roles that phase transformation and crystallographic orientation play in the Li-concentration and stress-strain fields. Results show very high local peaks of diffusion-induced stresses, indicating the significant potential for particle fracture. Anisotropic chemo-elastic fields give rise to local Li-concentration bands, causing chemically induced misfit strains and high stresses, and such occurrences are determined to be irrespective of the particle morphology. The locally high stresses are associated primarily with a crystallographic phase transformation between two hexagonal phases that is prominent at x ≈ 0.75, being closely related to bands of chemical-misfit strains developed in the Li0.75CoO2 material. The chemo-mechanical band structure depends significantly on crystallographic orientation within the electrode particle.