Coupled Electrochemical-Mechanical Modeling and Simulation of a Two-Dimensional Fully Heterogeneous Lithium-Ion Battery

In this paper, an electrochemical–mechanical coupling model is established for a two-dimensional, fully heterogeneous lithium-ion battery. The positive and negative active particles in the model follow a particle size distribution, while the binder and electrolyte are regarded as homogeneous phases. The heterogeneous geometrical model is first randomly generated using MATLAB and numerically simulated using COMSOL Multiphysics, and the electrochemical and mechanical properties of the positive and negative electrodes are analyzed. Subsequently, the effects of key parameters in the heterogeneous model on the electrochemical and solid mechanical properties of the battery are explored. Specifically, the effects of particle size, percentage of small particles, and particle variance on the multiplicity performance, mass transfer process, local current density, and stress–strain of the battery are investigated. The results show that the fully heterogeneous model constructed in this study exhibits higher simulation accuracy than the semi-heterogeneous model. Negative electrode particles endure greater mechanical stresses (von Mises stresses), strains, and displacements than positive electrodes due to material and distribution characteristics. Increasing the small-particle proportion (> 40%) significantly enhances rate capability, while reduced particle size variance (\(\sigma^{2} = 0.1\)) simultaneously improves both electrochemical performance and mechanical stability (30.39% lower maximum stress), demonstrating an inverse correlation between variance and overall battery performance. For optimal performance, heterogeneous models should incorporate both a high proportion of small particles and a narrow size distribution. This configuration enhances electrochemical uniformity, improves rate capability, and ensures superior mechanical stability. These findings provide critical guidelines for optimizing heterogeneous electrode design.