Dislocation Effect Boosting the Electrochemical Properties of Prussian Blue Analogues for 2.6 V High-Voltage Aqueous...

Prussian blue analogues (PBAs) have attracted increasing attention in aqueous zinc-based batteries (AZBs) with the advantages of an open framework, adjustable redox potential, and easy synthesis. However, they exhibited a low specific capacity and a poor cycle performance. In this work, crystalline potassium iron hexacyanoferrate (FeHCF) with dislocation was designed and prepared by a poly(vinylpyrrolidone) (PVP) additive. The metastable state provided by PVP would cause an electrostatic interaction between cyanogen and water molecules. The reduced force increases the steric resistance of the water molecules entering the crystal. The low content of crystal water in FeHCF is associated with the formation of dislocation. The dislocation effect effectively improves the electrochemical reactivity and reaction kinetics of FeHCF. Thus, it presents a high reversible capacity of 131 mAh g^-1 with a superior capacity retention of 85% after 550 cycles at 0.5 A g^-1. When used as a cathode, the AZBs display a high voltage of 2.6 V, a fast charging capability (<5 min), and a satisfactory cycle stability with a capacity retention of 82% after 400 cycles at 0.2 A g^-1 in decoupling electrolytes. This work provides an effective strategy for the design of high-performance PBA-based cathodes for 2.6 V AZBs.