Regulating Oxygen Coordination Environment to Achieve Suppressed Li–Ni Antisite Defect and Enhanced Anion Redox Reversibility in Nickel-Rich Cathodes for High-Energy Li-Ion Batteries

High-voltage nickel-rich cathodes have been extensively studied for their high energy density and economic efficiency. Nevertheless, the severe Li–Ni antisite defects and the accompanying irreversible anion redox reactions (ARRs) have limited their commercial application. In this work, using LiNi_0.8Co_0.1Mn_0.1O₂ (NCM80) as the model reference, a Y-ion doping strategy is introduced to modulate the oxygen coordination environment (due to strong Y–O interactions), effectively addressing both Li–Ni antisite defects and ARR reversibility. As revealed by X-ray diffraction and energy-dispersive X-ray spectroscopy, the strong Y–O bond effectively incorporates Y ions as a pinning effect within the TM layer, which decreases the Li–Ni antisite defect and simultaneously enhances the Li layer spacing, showing significant rate properties. In addition, combined with ex-situ X-ray photoelectron spectroscopy and electron paramagnetic resonance, it is revealed that the optimized electrochemical properties are ascribed to the restrained H2–H3 phase transition, reduced interfacial side reactions, and enhanced ARR electrochemical reversibility due to Y ions changing the coordination environment of oxygen. These findings reveal a promising path for the development of reduced Li–Ni antisite defects and the stabilization of the ARR in high-energy-density layered oxide cathodes.