Inert Gas‐Based Protective Layer Engineering for Stabilizing Nickel‐Rich Cathodes at High Voltages

Ni‐rich layered oxide cathodes, regarded as promising high‐energy‐density cathode materials for lithium‐ion batteries, still suffer from electrochemical performance degradation during cycling, primarily due to structural phase transitions and particle cracking. Although doping and surface coating are widely adopted modification strategies, such treatments are typically performed in air or oxygen‐containing atmospheres, leaving the effects of oxygen‐free environments largely unexplored. In this work, we systematically investigate the relationship between structural evolution and electrochemical performance of Ni‐rich cathodes modified under an oxygen‐free atmosphere. Notably, by precisely controlling the surface oxygen vacancies, an in situ layered‐spinel coherent coating is formed on the particle surface. This hybrid structure effectively increases the energy barrier for further oxygen vacancy formation, suppresses surface Ni─O reactivity, and stabilizes lattice oxygen, thereby significantly enhancing the high‐voltage cycling stability. After calcination at 200°C for 5 h in an argon atmosphere, the modified cathode exhibits a capacity retention of 83.6% after 200 cycles at 4.6 V, markedly improved from 69.1% for the pristine electrode. This study offers an innovative and effective strategy for stabilizing high‐voltage Ni‐rich layered oxide cathodes through atmosphere‐controlled surface engineering.