Evolution of electrochemically induced stress and its effect on the lithium-storage performance of graphite electrode

The electrochemically induced stress is a key factor that affects the lithium-storage performance of electrode materials.In this study,the origin and evolution of the electrochemically induced stress of the graphite electrode were investigated by in situ experiments and simulations.An in situ optical experiment was performed to observe the electrode color to analyze the concentration and diffusion process of lithium ions inside the graphite electrode.An electrochemical-mechanical coupling model under the same experimental conditions was developed and verified by the experimental lithium concentration,and characterization of the spatiotemporal evolution of the potential,lithium concentration,and stress during the diffusion process was realized.The results showed that lithium intercalation leads to compressive stress,which presents a gradient distribution along the Li+diffusion path,and it exhibits a“piecewise”nonlinear growth trend with increasing lithiation time.In addition,as the potential decreases,the stress increases from slow to fast relative to the lithium-concentration increase,showing the characteristic of stages.The influence of stress on the lithium-storage performance is discussed using the local lithium-intercalation rate and phase-interface migration speed as the key parameters.The lithiation mechanism was analyzed from the perspective of the energy,and it was found that the two factors cause the slow diffusion in the late stage of lithiation,thus affecting the actual lithium-storage performance.This study will enhance the understanding of the electro-chemo-mechanical coupling mechanism and provide guidance for enhancing stress-regulated battery performance.