K_0.39V₂O₅·0.52H₂O 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 V 2 O 5 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 K 0.39 V 2 O 5 ·0.52H 2 O 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(CF 3 SO 3 ) 2 to ZnSO 4, 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.