Defect engineering and in-situ electrochemical oxidation promote lattice reconstruction of VO2 for boosting the energy storage of aqueous zinc-ion batteries

Abstract

Finding a cathode with high capacity and rate performance is very important for the large-scale application of low-cost and safe aqueous zinc-ion batteries (AZIBs). In this work, VO2 containing oxygen rich vacancies (VO) was designed through fine regulation of the hydrothermal reaction, which was mainly due to the escape of crystalline water in the material. The rich oxygen vacancies in VO will adsorb water molecules in electrolyte and have redox reaction with water molecules, thus promoting the in-situ lattice reconstruction process. On the first charge of in-situ electrochemical oxidation process, VO undergoes a complete phase transition to an oxygen-deficient V2O5/V2O5·nH2O (O-VO), allowing subsequent (de)intercalation of zinc cations on the basis of the latter structure. The electrode thus has significant rate performance (376 mAh/g at 20 A/g). The energy density/power density at 20 A/g is 274 Wh kg−1/14550 W kg−1. This work provides fundamental insights into the formation of oxygen vacancies in materials, and for the first time combines defect engineering with in-situ electrochemical oxidation strategies, providing an innovative design strategy for constructing cathodes with high-rate capacity and high energy storage.