Residual Strain Analysis of Graphite Electrode During Galvanostatic Charge–Discharge at Different Current Densities

The intercalation and deintercalation of lithium ions cause periodic volume expansion/contraction and lattice variation in anode materials, which strongly influence the cycling life of lithium-ion batteries (LIBs). Accurate characterization of these changes is essential for a deeper understanding of cycling stability, particularly under different charging/discharging rates. Herein, in situ X-ray diffraction (XRD) and digital image correlation (DIC) were combined to investigate the chemical strain of graphite anodes at different current densities. In situ XRD results reveal the phase-transition-induced volume changes of active graphite particles, allowing the determination of the partial molar volume of lithium ions in active material. These results were further incorporated into the overall strain analysis of composite graphite anode measured by DIC, enabling the quantification of the strain contributions from inactive components, as well as the corresponding partial molar volume of lithium ions. The results show that the overall strain decreases as the current density increases from 0.1 to 0.2 C. The residual strain contribution from inactive materials is significantly greater than that from active materials at both current densities, and the strain associated with inactive components is much higher at 0.1 C than at 0.2 C. This work may support future studies on mechanical degradation mechanisms of LIBs.