Coupled Electrochemical-Thermal-Mechanical Modeling and Simulation of Multi-Scale Heterogeneous Lithium-Ion Batteries

In this study, a multi-scale heterogeneous electrochemical-thermo-mechanical coupling model (MHETM) is proposed. A two-dimensional heterogeneous gradient porosity electrode model (U1, G2, and G3) and a 3D macroscopic cell model are combined to realize a multi-scale coupled multi-physics field simulation of lithium iron phosphate (LFP) battery from microscopic particles to macroscopic cells. The MHETM model has higher accuracy and can more accurately describe the lithium ion transport process inside the active particles. The results show that the gradient porosity design optimizes the lithium ion diffusion path and improves the diffusion rate and end-of-discharge concentration. Meanwhile, the maximum stress and displacement of the G3 model are significantly lower than those of the U1 model, respectively. In addition, the thermal-mechanical coupling analysis revealed the negative correlation between thermal stress and thermal expansion. The introduction of the macro-thermal model further facilitates the lithium ion transport, resulting in an increase in the concentration maxima of both the U1 and G3 models, with a more significant increase in the G3 model. The MHETM model provides an effective tool for an in-depth understanding of the complex multi-physical field coupling mechanism inside the lithium-ion batteries.