Pre-potassiated hydrated vanadium oxide as cathode for quasi-solid-state zinc-ion battery

Zinc-ion batteries (ZIBs), in particular quasi-solid-state ZIBs, occupy a crucial position in the field of energy storage devices owing to the superiorities of abundant zinc reserve, low cost, high safety and high theoretical capacity of zinc anode. However, as divalent Zn²⁺ ions experience strong electrostatic interactions when intercalating into the cathode materials, which poses challenges to the structural stability and higher demand in Zn²⁺ ions diffusion kinetics of the cathode materials. Here, a microwave-assisted hydrothermal method is adopted to prepare pre-potassiated hydrated vanadium pentoxide (K_0.52V₂O₅·0.29H₂O, abbreviated as KHVO) cathode material, in which the potassium ions pre-inserted into the interlayers can act as “pillars” to stabilize the lamellar structure, and crystal water can act as “lubricant” to improve the diffusion efficiency of Zn²⁺ ions. Consequently, the KHVO displays high electrochemical properties with high capacity (～ 300 mAh/g), superior rate capability (69 mAh/g at 5 A/g) and ultralong cycling performance (>1500 cycles at 2 A/g) in quasi-solid-state ZIBs. These superior Zn storage properties result from the large diffusion coefficient and highly stable and reversible Zn²⁺ (de)intercalation reaction of KHVO.