Unraveling the nonlinear capacity fading mechanisms of Ni-rich layered oxide cathode

In order to improve the electrochemical performance and security of lithium-ion batteries, it is crucial to understand the structure and interface evolution behavior during charge-discharge cycling. Here, we investigate the dominant mechanism of nonlinear capacity fading of Ni-rich electrode materials under different charge-discharge rates. Despite the high initial discharge capacity of low-rate charge-discharge, the cumulative release of stress at the end of the cycle may rapidly reduce its capacity. During the high-rate cycling, the rapid decay of initial capacity is mainly caused by the thickening of CEI and the interfacial side reactions on account of electrolyte decomposition. Pulverization caused by microcrack expansion and intensified side reactions between the exposed new interface and the electrolyte, is the main contributor to the end-of-cycle capacity decay. One of the key causes of nonlinear capacity fading is the change of dominant mechanism. The proposed work provides new insight into the capacity decay and diving of lithium-ion batteries during cycling.