Unlocking Superior Na‐Storage Kinetics and Structural Durability in Na ₂ FePO ₄ F via Local Coordination Engineering

ABSTRACT Fluorophosphate Na ₂ FePO ₄ F (NFPF) is a promising cathode material for sodium‐ion batteries owing to its low cost, environmental friendliness, and abundance of constituent elements. However, its practical applications are hindered by intrinsic challenges such as iron dissolution and sluggish Na ⁺ diffusion kinetics. Herein, we report a rational design local coordination environment engineering(LCE) strategy, in which the strongly covalent Zn─O/F bonds are incorporated into the NFPF, constructing robust ZnO ₄ F ₂ units that act as structural pillars within the crystal framework. This targeted modification effectively tailors the local electronic structure and ion transport pathways, resulting in a reduced bandgap and significantly lowered Na ⁺ migration barrier. Combined theoretical and experimental evidence reveals that the incorporation of ZnO ₄ F ₂ not only mitigates lattice strain during cycling but also suppresses transition metal dissolution by stabilizing the anionic framework. As a result, the optimized Na ₂ Fe _0.94 Zn _0.06 PO ₄ F (NFZPF‐6) cathode delivers a high capacity of 114.9 mAh g ⁻¹ , excellent rate performance (71.2 mAh g ⁻¹ at 20C), and exceptional long‐term cyclability with 85.5% capacity retention after 1000 cycles at 10C. This work provides a new paradigm for enhancing both structural stability and reaction kinetics in polyanionic cathodes through atomic‐level local environment regulation.