A chemo-mechanical grain boundary model and its application to understand the damage of Li-ion battery materials

Authors: Yang Bai, Kejie Zhao, Yao Liu, Peter Stein, and Bai-Xiang Xu

Although the unique mechanical and transport features of grain boundaries (GBs) in polycrystalline ion conductors have been recognized, the understanding of the chemo-mechanical interplay and its impact is insufficient. We present a coupled GB model which includes both the damage-dependent across-grain transport and a mechanical cohesive zone law. 3D simulations on LiNixMnyCozO2 demonstrate that the chemical process and the mechanical degradation go hand-in-hand: the enhanced intergranular chemical inhomogeneity challenges the GB mechanical strength, while the GB damage influences or even blocks the across-grain transport. Results explain well the experimentally observed features including chemical hot spots and surface layer delamination.

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