In-situ study of lithium insertion on the electrochemical-mechanical coupling behavior of graphite composite electrodes

Graphite has long served as one of the most commonly used anode materials in lithium-ion batteries, where its electrochemical-mechanical coupling performance is critical for maintaining structural stability and extending cycle life. This study investigates the evolution of the electrochemical-mechanical coupling characteristics of graphite electrodes during electrochemical cycling. Experiments were performed using in situ curvature testing, combined with in situ X-ray Diffraction (XRD) analysis. A physical model was created to analyze the variations in curvature, Young's modulus, strain, and partial molar volume of the graphite composite electrodes. The results indicate that the modulus of elasticity augments with the concentration of lithium ions during lithiation. Additionally, the partial molar volume undergoes periodic changes with the state of charge (SOC). In-situ XRD experiments revealed the lithiation phase transformation process in graphite. The interlayer spacing was calculated by tracking the evolution of the (001) and (002) diffraction peaks, which verified the accuracy of the partial molar volume during the electrochemical cycle. This further elucidates the phase transformation mechanisms of lithium intercalation and the volumetric changes of the active material within the graphite anode.