Alkali-metal-depleted vanadium Prussian blue analogue enabling high-rate aqueous Zn-ion batteries

Abstract

Vanadium-based Prussian blue analogues (VFe) have potential in aqueous zinc-ion batteries (AZIBs) due to their high operating voltage and good stability. However, their practical application is hindered by relatively low specific capacity and inadequate rate capability. To address these limitations, an alkali-metal-depleted vanadium-based Prussian blue analogue (K0.0068V1.64O2Fe(CN)6·4.2H2O) was prepared and exploited as a cathode material for aqueous zinc-ion batteries. Extensive removal of potassium ions creates additional vacant sites for Zn2+ storage and reduces steric hindrance, thereby enhancing ion transport kinetics. The multielectron redox reactions enabled by multivalent vanadium centers, the shortened ion diffusion pathways and increased electrode/electrolyte contact area conferred by a nanostructured morphology, and a robust framework, brought about a considerable capacity, favorable rate performance, and respectable cycling durability. The VFe cathode achieved a high specific capacity of 227 mAh g-1 at 300 mA g-1 and maintained 154 mAh g-1 at a high current density of 15 A g-1. This work offers a promising pathway toward the rational design of high-performance cathode materials for advanced aqueous zinc-ion batteries.