Decoupling the Capacity Fading in Ni‐Rich Layered Materials during High‐Temperature Cycling in the Full‐Cell System

Abstract

Abstract The performance of commercial lithium‐ion batteries (LIBs) tends to degrade over time owing to the deterioration of key components, including cathode, anode, and electrolyte. To enhance performance, it is crucial to gain insights into the actual deterioration state of each element. Here, the high‐temperature deterioration of a Ni‐rich layered cathode is investigated, which is widely used in electric vehicles. In the refresh process after a prolonged cycle, a significant recovery of the lattice structure predominantly occurs in the discharge region. This pseudo‐deterioration of the Ni‐rich cathode within the full‐cell system is mainly due to the consumption of the Li‐ion forming the solid electrolyte interphase layer at the graphite anode during the cycle. Moreover, irreversible deteriorations that are not restored through the refresh process are observed in both charge and discharge regions. Structure analyses reveal that the long‐term cycling at the high temperature leads to a mixed fading of charge and discharge via various deterioration such as the formation of NiO‐like rock salt phase on the cathode surface and increased cation disorder in the bulk. These findings deepen the understanding of the deterioration behavior of Ni‐rich cathodes in full‐cell systems, providing insights for enhancing the performance of high‐temperature cycling.