Mechanical interactions regulated kinetics and morphology of composite electrodes in Li-ion batteries

Abstract

Li-ion batteries are a system that features strong coupling between mechanical stresses and electrochemical reactions. Prior studies on stresses in electrodes are focused on single particles or mono-phase materials. The kinetics and morphology of composite electrodes regulated by the mechanical interactions are much less exploited. We integrate a continuum theory of coupled diffusion and large elasto-plastic deformation into a finite element program. Such a computational tool enables us to explore the intimate coupling between the lithiation kinetics and stresses in three-dimensional electrodes that are composed of multiple components. We find that Li profiles and stress states in multiple particles constrained by a matrix are significantly different from that in a free-standing configuration. The mechanical interactions regulate Li chemical potential in Si nanowires and transform the anisotropic deformation to an isotropic behavior and vice versa. The modeling is in good agreement with a recent experimental report.