Engineering Oxygen Vacancies on VO2 Multilayered Structures for Efficient Zn2+ Storage

Abstract

AbstractVanadium dioxide (VO2(B)) is a proper cathode for aqueous zinc‐ion batteries (ZIBs) due to its shear structure and high theoretical capacity. However, the sluggish kinetics and structure instability derived from the strong electrostatic interaction between Zn2+ and the VO2 host hinder its further application. Defect engineering is a useful way to circumvent the limitations. Herein, oxygen‐defect VO2 (Od‐VO2) with tunable oxygen vacancy concentration are obtained via a facile one‐step hydrothermal method by adjusting ascorbic acid addition. It is proved that oxygen vacancies can provide extra active sites for Zn2+ storage and reduced electrostatic barrier for Zn2+ transportation, but excessive vacancy content would lead to a reverse effect. The Od‐VO2 cathode with optimum oxygen vacancy concentration achieves an outstanding performance with a high capacity of 380 mAhg−1 at 0.2 A g−1, excellent cycle stability with 92.6 % capacity retention after 2000 cycles at 3 A g−1 and a high energy density of 197 Wh kg−1 at the power density of 0.641 kW kg−1. Therefore, this defect engineering method for Od‐VO2 provides an attractive way for high‐performance aqueous ZIB cathodes.