Correlative X-ray microscopy and electrochemical aging for non-destructive elucidation of degradation mechanisms in commercial Li-ion batteries under high-rate cycling

Commercial Li-ion batteries are widely used in energy storage applications, yet their performance under severe, non-standard operating conditions is not well understood. In the present work, 18650 Li-ion cylindrical cells were subjected to repeated charge/discharge cycles beyond the manufacturer's recommended limits. The cells were periodically analyzed every 1000 cycles using X-ray microscopy (XRM), complemented by X-ray diffraction (XRD), RAMAN and scanning electron microscopy (SEM) analyses of the fresh and post-cycling electrodes. Even within the first 100 cycles, substantial, irreversible capacity loss was observed. After 4000 cycles, structural collapse begins in the central region and spreads outward, resulting from degradation mechanisms in both anode and cathode materials that compromise the cell's structural integrity. These results provide important insight into the practical operational limits of Li-ion batteries, raising the question of whether strict adherence to manufacturing specifications is necessary or whether these systems exhibit greater resilience under off-design conditions than currently assumed.