Unlocking Superior Na-Storage Kinetics and Structural Durability in Na₂FePO₄F via Local Coordination Engineering

Fluorophosphate Na₂FePO₄F (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 ZnO₄F₂ 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 ZnO₄F₂ not only mitigates lattice strain during cycling but also suppresses transition metal dissolution by stabilizing the anionic framework. As a result, the optimized Na₂Fe_0.94Zn_0.06PO₄F (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.