Influence of Li Concentration-Dependent Diffusion Coefficient and Modulus Hardening on Diffusion-Induced Stresses in Anisotropic Anode Particles

Abstract

Particle cracking caused by diffusion-induced stresses (DISs) is an important reason for lithium-ion battery (LIB) capacity fading. In this study, concentration-dependent material properties are introduced to model the distribution of the concentrations and evolution of DISs in anisotropic active particles. The concentration-dependent diffusion coefficient increases the concentration gradient and thus the DISs, and the concentration-dependent elastic modulus hardening increases the internal DISs and thus the stress-enhanced diffusion of Li ions. Diffusion in the direction of a large diffusion coefficient enhances the diffusion in the direction of a small diffusion coefficient, which leads to an anisotropic concentration, concentration gradient and DISs. The greater the anisotropic difference within the particles is, the more obvious the decrease in the radial stress and hoop stress. The results can be comparable with many published experimental results of graphite and indicate that the role of concentration-dependent material properties and anisotropy in the particles cannot be ignored.