Pre‐Deoxidation of Layered Ni‐Rich Cathodes to Construct a Stable Interface with Electrolyte for Long Cycling Life

Abstract Ni‐rich layered oxides as the cathode materials of high‐energy‐density lithium‐ion batteries (LIBs) suffer from capacity decay and structural instability owing to oxygen loss during cycling. It is a huge challenge to prevent the oxygen loss of Ni‐rich cathode materials during long cycling. Here, a pre‐deoxidation of LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) single crystal materials is achieved by heat treatment at elevated temperatures in argon condition to form a stable surface with rock salt structure. The stable surface structure with oxygen vacancy defects successfully suppresses the harmful phase transitions of NCM811 and effectively improves the stability of the NCM811/electrolyte interface during cycling at a high cut‐off voltage. In addition, the intragranular structural evolution and cation mixing degree is inhibited to effectively suppress the intergranular cracking and particle pulverization of cathode during long cycling. The pre‐deoxidation of NCM811 exhibits 70.6% capacity retention after 1000 cycles at the current density of 0.5 C between 2.8 and 4.3 V, which is much larger than that of pristine NCM811 capacity retention of 27.3%. The strategy of pre‐deoxidation of Ni‐rich layered structure cathode to regulate the defect chemistry and surface structure provides a facile and effective way to achieve long cycling life high‐energy density LIBs.