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 chargedischarge 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.

Automated summary

To enhance the electrochemical performance and safety of lithium-ion batteries, it is essential to understand the evolution of structure and interface during charge-discharge cycling. This study investigates the dominant mechanism behind the nonlinear capacity fading of Ni-rich electrode materials at different charge-discharge rates. Low-rate charge-discharge exhibits high initial discharge capacity, but cumulative stress release during the cycle quickly reduces its capacity. High-rate cycling, on the other hand, shows rapid decay of initial capacity due to CEI thickening and electrolyte decomposition caused interfacial side reactions. Pulverization from microcrack expansion and intensified side reactions between the new exposed interface and electrolyte contribute significantly to the end-of-cycle capacity decay. The change in dominant mechanism is one of the key factors causing the nonlinear capacity fading. This work provides new insights into the capacity decay and failure of lithium-ion batteries during cycling.