A strategy to control crystal water content in hydrated vanadium oxide cathode for promoting aqueous rechargeable zinc-ion batteries

A simple hydrothermal route is used to prepare 3D porous hydrated vanadium oxide porous microspheres with different crystal water content. It is the first report that too much water molecule can lead to poor Zn storage performance and optimal structural water content is needed to improve electrochemical performance. By tuning the ratio of Zn to V during the synthesized process, Zn0.146V2O5∙0.579 H2O porous microspheres with optimal structural water content exhibit superior electrochemical performance for a promising aqueous rechargeable Zn-ion batteries. At the current density of 0.1 A g−1, it can register a high reversible discharge capacity of 416 mAh g−1. An initial discharge capacity can reach 192 mAh g−1 at the current density of 10.0 A g−1, the specific capacity remains at 202 mAh g−1 and the capacity retention is 105% after 10,000 cycles. Optimal structural water content as well as synergistic effect of pre-intercalated Zn2+ ions should be responsible for excellent electrochemical performance of cathode materials.