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

Vanadium 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 (O-d-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 O-d-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 O-d-VO2 provides an attractive way for high-performance aqueous ZIB cathodes.

Automated summary

Oxygen-defect VO2 cathode with tunable oxygen vacancy concentration is obtained via a one-step hydrothermal method by adjusting ascorbic acid addition. The oxygen vacancies provide extra active sites for Zn2+ storage and reduce the electrostatic barrier for Zn2+ transportation. The optimum oxygen vacancy concentration of the O-d-VO2 cathode achieves outstanding performance in terms of capacity, cycle stability, and energy density.