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.
Keywords: Capacity; Mechanism; Prussian blue analogues; Silver hexacyanoferrate; Zinc-ion Battery.
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