Atomic Layer-Deposited ZnO Layer on Hydrated Vanadium Dioxide Cathodes against Vanadium Dissolution for Stable Zinc Ion Batteries

Vanadium oxides are considered one of the most promising cathode materials for aqueous zinc ion batteries. However, vanadium dissolution caused by undesirable side reactions greatly decreases the structure stability and capacity retention. In this work, an atomic layer-deposited ZnO layer is uniformly coated on a hydrated vanadium dioxide nanosheet array cathode, which effectively suppresses the vanadium dissolution and side reactions. The resultant cathode displays improved capacity retentions from 74 to 89% after 100 cycles at 0.5 A g–1 and from 29 to 71% after 990 cycles at 5 A g–1. Moreover, the structural evolution after electrochemical cycling of the cathode is thoroughly investigated to reveal the protection mechanism. The atomic layer deposition strategy may also be extended to the protection of other cathodes that suffer from the dissolution issue with wide choices of the protection layer materials.