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

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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.
Funding Information
  • Natural Science Foundation of Chongqing Municipality (2022ZX5100028)
  • National Natural Science Foundation of China (52272188)
  • National Natural Science Foundation of China (U22A20227)
  • Natural Science Foundation of Beijing Municipality (2232025)

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