Dual Redox Reactions of Silver Hexacyanoferrate Prussian Blue Analogue Enable Superior Electrochemical Performance for Zinc‐ion Storage

Prussian blue analogues (PBAs) have been employed as host materials of aqueous zinc‐ion batteries (ZIBs), however, they suffer from low capacity and poor cycling stability due to limited electron transfer and the presence of interstitial water in PBAs. Herein, a vacancy and water‐free silver hexacyanoferrate K0.95Ag3.05Fe(CN)6 (AgHCF‐3) was synthesized by adjusting the ratio of K and Ag in the framework. It offers nearly four electrons involving two sequential redox reactions, namely, Fe3+/Fe2+ and Ag+/Ag0, to deliver a large capacity of 179.6 mAh g‐1 at 20 mA g‐1 with Coulomb efficiency of ~100%. The Zn//AgHCF‐3 cell delivers an estimated energy density of 200 Wh kg‐1, surpassing reported PBAs‐based ZIBs. The formation of Ag0 in the cycling process merits favorable rate performance of AgHCF‐3 (156.4 mAh g‐1 at 200 mA g‐1 with 80.3% capacity retention after 100 cycles). This investigation paves new pathways for high‐capacity PBA cathodes.