X-ray absorption near-edge structure study on positive electrodes of degraded lithium-ion battery

18650-type cylindrical cells using LiNi 1/3 Mn 1/3 Co 1/3 O 2 (NMC) and hard carbon as positive and negative electrode material, respectively, were fabricated and degraded by cycle tests. The capacity of the cells remained more than 95% and 85% after cycle tests at 25 and 50 °C, respectively. After the cycle tests, Li-deficient cubic phase was observed on the surface of NMC. This phenomenon should be related to the degradation mechanism of this type of cell.