Ultrathin VO2(B) nanosheets assembled into 3D micro/nano structured flower-like microspheres for high-performance cathode materials of Li-ion batteries

Vanadium oxides, as a potential cathode material for lithium-ion batteries (LIBs), have received extensive attention from researchers owing to their significant advantages in terms of theoretical specific capacity, energy density, and power density. However, vanadium oxides lead to irreversible decay of specific capacity during cycling for reasons such as poor structural stability and electrical conductivity. In this paper, the flower-like VO2(B) microsphere assembled from ultrathin nanosheets was synthesized successfully by hydrothermal method, and their effects on the morphology as well as the phase of VO2(B) are investigated by varying the hydrothermal reaction time and the concentration of oxalic acid. The results show that the flower-like VO2(B) microsphere electrode material not only provides a larger active area, but also offers a faster lithium ion diffusion rate and a shorter charge transport path, resulting in a high reversible capacity, outstanding rate performance, and excellent long cycle life. The flower-like VO2(B) microsphere electrode exhibited a first discharge specific capacity of 282.9 mAh/g (at a current density of 0.1 A/g) and a capacity retention of 80.7 % after 50 cycles. In addition, the electrode material shows a first discharge specific capacity of 209.6 mAh/g at a high current density (1 A/g) and a capacity retention rate of 83.1 % after 200 cycles. Consequently, the VO2(B) provides great development potential as a cathode material for next-generation LIBs.