Diffusion and Induced Stress Tuning Mechanisms: Analytical Modeling of Species Transport in Silicon-Graphene Layered Composite Electrodes for Lithium Batteries

Abstract

Experimental studies have demonstrated that lithium battery electrodes with multi-layer active plates exhibit both high volumetric capacity and rate capability. The overall performance of such electrodes is closely related to the mechanical response, which is impacted by Li-ion transport. Herein, detailed descriptions of diffusion and induced stress in silicon-graphene layered composite electrode were theoretically investigated. First, the natural eigenfunction expansion method was used to obtain the exact analytical solutions of Li-ion concentration field in bi-layer active plates under galvanostatic and potentiostatic charging. Then, the biaxial stress expression of composite electrodes was deduced. Moreover, the diffusion contact resistance was explored to describe the resistance effect of interface between different layers for Li-ion diffusion, which is lacking in previous studies. Our findings suggest that the diffusion contact resistance will increase stress in the electrode, and its influence should be minimized as much as possible. Furthermore, material properties, such as the distribution of active materials, have a significant impact on the performance of composite electrodes. In present work, the mechanism of diffusion-induced stress on electrodes with bi-layer active plates was clarified, and it provide a guidance for electrode design from the perspective of mechanics.