In‐Situ Dynamic Compensation Strategy Enables Jahn‐Teller Effect Suppression in Zn‐Doped Dual‐Active‐Site Copper Hexacyanoferrate Cathodes for High‐Energy and Ultra‐Stable Ammonium‐Ion Storage

Abstract Copper hexacyanoferrate (CuHCF) with 3D channels and high discharge plateau is widely recognized as a highly promising cathode material for ammonium‐ion (NH 4 + ) storage. However, the practical application of CuHCF has faced challenges due to limited capacity and structural instability, primarily arising from single active site and serious Jahn–Teller distortions. Herein, an innovative in‐situ dynamic compensation strategy is reported to prepare Zn‐doping dual‐active‐site CuHCF (ZnCuHCF) as high‐energy and ultrastable cathode materials for NH 4 + storage. Zn doping induces fission of Cu e 2g orbitals, causing lattice to aberrate and reach stable state, while during NH 4 + intercalation process, changes mainly in Fe t 2g electronic orbitals help maintain stability of ZnCuHCF structure. Consequently, ZnCuHCF in 23 m NH 4 OTf + 0.5 m Zn(OTf) 2 aqueous electrolyte exhibits high discharge potential of 0.94 V, high capacity of 121.7 mAh g −1 at 1 A g −1 and impressive capacity retention of 92.1% after 10 000 cycles. To highlight, fiber‐shaped aqueous Zn/NH 4 hybrid batteries based on ZnCuHCF cathode are successfully constructed, achieving admirable energy density of 85.73 mWh g −1 and remarkable capacity retention of 85.2% after 12 500 cycles. This work paves the way for designing CuHCF with high capacity, high voltage and robust cycling stability in NH 4 + storage for applications in wearable aqueous batteries.