Electronic Orchestration of Iron‐Based Sulfate Cathodes Toward Exceptional Sodium‐Storage Longevity Beyond 20000 Cycles

Sodium iron sulfate (Na 2+2x Fe 2‐x (SO 4 ) 3 , NFS) has garnered industrial attention as a cheap and high‐voltage cathode material for sodium‐ion batteries. However, the practical application has been severely hindered by its sluggish reaction kinetics and poor working/air stability. In this study, we demonstrate an electronic orchestration strategy via inner cation doping to construct NFS composites with carbon encapsulation toward boosted sodiation kinetics and durability. Ni 2+ incorporation is theoretically and experimentally revealed to increase the electron conductivity and ion diffusivity of NFS by modulating charge redistribution and promote the formation of a uniform, stable, and NaF‐rich interphase. A hollow carbon scaffold is of dual benefits for expedited electron‐transfer kinetics by building intimate electrical contacts to NFS particles and enhanced electrode robustness by cushioning volume change upon cycling test. These synergistic advantages enable the optimized Ni‐NFS/C cathode to deliver an exceptional capacity of 116.8 mAh g −1 at 0.1 C, a high‐rate retention of 76.6 mAh g −1 at 20 C, and an unprecedented lifetime with 83.1% capacity preserved after 20 000 cycles. The practical viability of the composite is demonstrated by its excellent on‐shelf air stability and superior performance in full cell.