Regulating Reversibility of Anion Redox and Electronic Structure via Controlled Surface Oxygen Vacancies in Lithium‐Rich Layered Oxides

ABSTRACT Lithium‐rich layered oxides (LRLO) deliver high capacities through lattice oxygen redox, particularly associated with the monoclinic C 2 /m phase. However, their practical application is hindered by severe voltage decay and structural degradation. Here, gas‐solid reaction fluorination strategy is designed, which results controllable oxygen vacancies and in situ LaF 3 ‐coated composite with a gradient F/La distribution. This approach not only regulates the reaction sequence between the C 2 /m and R‐3m phases, but also reinforces interfacial stability. Density functional theory calculations reveal that the engineered electronic structure shifts the O 2p non‐bonding band (+0.367 eV) and the lower Hubbard band (+0.315 eV), enabling a dynamic redox pathway: localized Ni 2+ dominates at low states of charge, while delocalized Ni 3+ / 4+ suppresses O─O dimerization and strengthens TM─O bonding at high voltages. Differential Electrochemical Mass Spectrometry (DEMS) and in situ Fourier Transform Infrared Spectroscopy (FTIR) confirm that oxygen release is greatly suppressed, facilitating the formation of the robust CEI. Benefiting from these synergistic effects, the modified LRLO delivers 91.1% capacity retention vs. 74.3% for the bare sample. These findings clarify structure‐performance relationships in LRLO and highlight surface engineering as key to enhancing reversibility and cycling stability.