Unlocking Coupled of Electron/Ion Transport for Superior Electrochemical Performance in Hybrid Phosphate Cathodes of Sodium Ion Batteries
Yuhang Xin, Hexiao Zhang, Yingshuai Wang, Qianchen Wang, Qingbo Zhou, Kunyu Zhao, Feng Wu, Hongcai Gao
Abstract
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.