Crystal water enlarging the interlayer spacing of ultrathin V2O5·4VO2·2.72H2O nanobelts for high-performance aqueous zinc-ion battery

•The novel ultrathin hydrated V2O5·4VO2·2.72H2O nanobelts was obtained through a hydrothermal method.•The existence of crystal water can effectively improve performance.•V2O5·4VO2·2.72H2O delivers excellent cycling stability and the specific discharge capacity.•The high reversibility of Zn2+ insertion/extraction in V2O5·4VO2·2.72H2O was demonstrated by in-situ XRD. Although rechargeable aqueous zinc-ion batteries (AZIBs) are emerging candidates for high energy density, safety and cost effectiveness large-scale energy storage, they still lack suitable cathodes with high rate capabilities. In the present work, ultrathin V2O5·4VO2·2.72H2O nanobelts were synthesized via a facile hydrothermal method as cathode materials for ZIBs. Benefiting from expanded interlayer spacing that results from crystal water, the V2O5·4VO2·2.72H2O cathode exhibits an improved capacity of 567 mAh·g−1 at 0.1 A·g−1 and superior rate capability of 10.0 A·g−1 with a decent capacity of 215 mAh·g−1. When at 10.0 A g−1, a capacity retention of 94.0% with respect to the initial specific capacity was retained after 1000 cycles, and 85.2% was obtained even after 2000 cycles. Furthermore, in-situ X-ray diffraction and various structural measurements proved the high reversibility of Zn2+ insertion and extraction in V2O5·4VO2·2.72H2O cathode. Further investigations show that ultrathin V2O5·4VO2·2.72H2O nanobelts have become a promising cathode material for the high-potential rechargeable AZIBs, and may clarify effective interlayer engineering strategies triggered by crystal water.