Abstract:

Graphite is currently one of the most widely used anode materials in lithium batteries, and its electrochemical-mechanical coupling performance is crucial for the structural stability and cycling lifespan of lithium batteries. This study employed in situ measurements to investigate the evolution of the electromechanical coupling performance of composite graphite electrodes during electrochemical cycling. A physical model was also developed to analyze the evolution of the curvature, Young's modulus, strain, and partial molar volume of the composite graphite electrodes. The results show that, the elastic modulus of the graphite electrode increases progressively with the progression of lithiation, indicating a hardening behavior, while the partial molar volume undergoes phase changes that correspond to the charge state. Current collectors of different thicknesses significantly affect the stress and strain within the electrode. A thicker current collector provides more pronounced mitigation of the strain in the active layer. The peak stress and strain in the active layer of the electrode reach their maxima during the third electrochemical cycle, and the evolutionary trends of each cycle tend to converge. This work reveals the systematic mechanical-response characteristics and the evolution of the mechanical properties of graphite electrodes during the electrochemical reaction process, providing significant theoretical support for a deeper understanding of the mechanical behavior of lithium-ion battery electrodes.

Key words: graphite composite electrode, modulus, partial molar volume, lithium-ion battery