摘要
Li-rich cation-disordered rocksalt (DRX) oxides are promising Co/Ni-free cathodes, yet their practical application is heavily bottlenecked by limited anionic redox reversibility, voltage hysteresis, and structural degradation. Herein, we introduce a Fe-substituted strategy in Li1.2Mn0.4−xFexTi0.4O2 (0 ≤ x ≤ 0.1) to simultaneously enhance reversible oxygen redox and reduce short-range order in the material. Operando X-ray spectroscopies reveal that the highly oxidized Fe4+ state triggers spontaneous ligand-to-metal charge transfer, lowering the activation barrier for anionic redox and enhancing its reversibility. Density functional theory calculations demonstrate that this originates from Fe-induced band structure modifications, which shifts the dominant redox center to the anionic network. Concurrently, operando X-ray diffraction, transmission electron microscopy, and machine learning-driven Monte Carlo simulations demonstrate that Fe substitution disrupts MnMn clustering. This atomic-level homogenization acts as a structural buffer against cooperative Jahn-Teller distortions, suppressing reaction heterogeneity to enable a continuous solid-solution pathway. Consequently, the optimal Fe-substituted cathode delivers an enhanced initial discharge capacity of 247 mAh g−1 and a superior initial Coulombic efficiency of 90.4%, compared to 228 mAh g−1 and 87.9% for the pristine sample, respectively. This work details how transition-metal substitution modulates electronic charge transfer and local structural stability, guiding the design of high-energy DRX cathodes.
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•Fe substitution lowers the activation barrier for oxygen redox in DRX.•Fe tunes band structure to activate ligand-to-metal charge transfer.•ML-driven simulations show Fe disrupts Mn clustering to buffer distortion.•Optimized cathode delivers 247 mAh g−1 with 90.4% initial efficiency.