Synergizing Covalent‐Ionic Tri‐Site Coordination in P2‐type Na _0.67 Fe _0.33 Mn _0.67 O ₂ Induces Suppressed Layer‐Slipping and Stablized Lattice Oxygen for Sodium‐Ion Batteries at Wide Potential

ABSTRACT Improving the stability of the oxygen framework and suppressing irreversible interlayer slip remain long‐standing challenges for Fe/Mn‐based layered oxide cathodes. Herein, a trans‐sublattice three‐site co‐substitution strategy is proposed and implemented in Na _0.67 Fe _0.08 Cu _0.25 Mn _0.62 Mg _0.05 O _1.95 F _0.05 (NFCMMOF) to precisely regulate the covalent‐ionic bonding balance within both cationic and anionic sublattices. This rational lattice design simultaneously mitigates the detrimental P2‐O2 phase transition and Jahn‐Teller distortion, constructs highly robust TM‐O/F bonds, markedly reinforces the overall oxygen framework, and establishes a highly reversible Fe ³⁺ /Fe ⁴⁺ ‐dominated charge compensation mechanism. In situ XRD, in situ EIS‐DRT, and comprehensive DFT calculations collectively reveal that the synergistic three‐site regulation significantly enhances layered structural stability, expands the O‐Na‐O slab spacing, lowers Na ⁺ migration barriers, and enables the concurrent optimization of charge transport and ion diffusion kinetics. Consequently, NFCMMOF delivers a high reversible capacity of 162.9 mAh·g ⁻¹ at 0.1 C and retains 85.1% of its capacity after 1000 cycles at 10 C, together with outstanding moisture tolerance. Moreover, the assembled full cell achieves high energy densities of 281.5 and 160.8 Wh·kg ⁻¹ at power densities of 70.4 and 2260.7 W·kg ⁻¹ , respectively, demonstrating a broadly applicable lattice‐engineering paradigm for fast, stable, and practical Na ⁺ storage.