Unlocking Coupled of Electron/Ion Transport for Superior Electrochemical Performance in Hybrid Phosphate Cathodes of Sodium Ion Batteries

Abstract Multiple performance limitations, including low electron transport capability and sluggish Na ⁺ diffusion kinetics, impede the specific capacity and high‐rate performance of Na ₄ Fe ₃ (PO ₄ ) ₂ P ₂ O ₇ (NFPP) as a cathode material for sodium‐ion batteries. In this work, the electrochemical performance of NFPP is significantly enhanced by decoupling electron/ion transport during charge/discharge processes. Theoretical calculations and advanced characterization techniques confirm that the W 5d empty orbitals provide electron‐hopping sites within the framework, enabling local charge exchange to unlock electron/ion transport coupling. The W‐substituted NFPP cathode delivers a reversible capacity of 120.7 mAh g ⁻¹ (0.1C; 1C = 129 mAh g ⁻¹ ), exceptional rate capability (72 mAh g ⁻¹ at 50C), and a cycling stability exceeding 10 000 cycles. Full cells paired with hard carbon anodes retain 80% capacity after 2C‐rate discharging, while pouch cells achieve a reversible areal capacity of 0.61 mAh cm ⁻² . This work elucidates the critical role of local charge exchange in unlocking electron/ion transport coupling, offering a promising strategy for designing cathodes with high capacity, rapid discharge capability, and ultralong cycle life for practical applications of sodium‐ion batteries.