K0.39V2O5·0.52H2O Nanostructures with Oxygen Vacancies as Cathodes for Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are considered a promising option for large-scale energy storage because of their low cost and high safety. However, the lack of suitable cathode materials has limited their development. Vanadium-based oxides have been widely studied due to their layered crystal structures and high theoretical specific capacities. Nevertheless, they are prone to vanadium dissolution and have a limited cycle life during cycling. Pre-embedding of K+ in V2O5 by the hydrothermal method increases the layer spacing and stabilizes the crystal structure. Oxygen vacancies are introduced to provide more sites for Zn storage. The results show that the K0.39V2O5·0.52H2O nanostructures exhibit stable cycling performance. The capacity is 552 mAh g–1 at 0.1 A g–1, and the capacity retention is 90% for 11,000 cycles at 10 A g–1. When the electrolyte is changed from Zn(CF3SO3)2 to ZnSO4, the capacity retention rate is 98% after 200 cycles at 1 A g–1 and nearly 100% after 2400 cycles at 10 A g–1. This study highlights the potential of ion doping and oxygen defects in modifying cathode electrodes and provides a guide for exploring the working mechanisms of aqueous zinc-ion batteries.