Orbital Stabilization of Anionic Redox via Surface Restructuration for Li-Rich Mn-Based Layered Oxides

Lithium-rich layered oxides are renowned for their high capacity, originating from both cationic and anionic redox reactions. However, the anionic redox process often induces the formation of O-O dimers, triggering oxygen release and transition metal migration that typically initiate at the particle surface and lead to progressive structural degradation and performance decay. In this study, we report a lithium-rich manganese-based layered oxide cathode featuring a surface reconstruction layer in which nickel ions occupy the 4 h Wyckoff sites within the Li₂MnO₃ phase. This surface-site-specific nickel occupation induces parallel alignment of electron-depleted O 2p orbitals, effectively suppressing the formation of unstable O-O dimers and inhibiting oxygen release. The engineered cathode delivers a remarkable reversible capacity of 325 mAh g^{- 1} at 0.1C (20 mA g^{- 1}), along with an outstanding rate capability of 272.8 mAh g^{- 1} at 1C (200 mA g^{- 1}) and 90% capacity retention after 300 cycles. This surface engineering strategy establishes a novel structural response mechanism for oxygen redox reactions, enabling the simultaneous achievement of high capacity and long-term cycling stability. The findings provide critical insights for the development of advanced high-energy-density cathode materials.