K<sub>0.39</sub>V<sub>2</sub>O<sub>5</sub>·0.52H<sub>2</sub>O Nanostructures with Oxygen Vacancies as Cathodes for Aqueous\nZinc-Ion Batteries

Aqueous\nzinc-ion batteries (AZIBs) are considered a promising option\nfor large-scale energy storage because of their low cost and high\nsafety. However, the lack of suitable cathode materials has limited\ntheir development. Vanadium-based oxides have been widely studied\ndue to their layered crystal structures and high theoretical specific\ncapacities. Nevertheless, they are prone to vanadium dissolution and\nhave a limited cycle life during cycling. Pre-embedding of K<sup>+</sup> in V<sub>2</sub>O<sub>5</sub> by the hydrothermal method increases\nthe layer spacing and stabilizes the crystal structure. Oxygen vacancies\nare introduced to provide more sites for Zn storage. The results show\nthat the K<sub>0.39</sub>V<sub>2</sub>O<sub>5</sub>·0.52H<sub>2</sub>O nanostructures exhibit stable cycling performance. The capacity\nis 552 mAh g<sup>–1</sup> at 0.1 A g<sup>–1</sup>, and\nthe capacity retention is 90% for 11,000 cycles at 10 A g<sup>–1</sup>. When the electrolyte is changed from Zn(CF<sub>3</sub>SO<sub>3</sub>)<sub>2</sub> to ZnSO<sub>4</sub>, the capacity retention rate is\n98% after 200 cycles at 1 A g<sup>–1</sup> and nearly 100%\nafter 2400 cycles at 10 A g<sup>–1</sup>. This study highlights\nthe potential of ion doping and oxygen defects in modifying cathode\nelectrodes and provides a guide for exploring the working mechanisms\nof aqueous zinc-ion batteries.