Brookite phase vanadium dioxide (B) with nanosheet structure for superior rate capability aqueous Zn-ion batteries

Vanadium dioxide is widely used as a low-cost, high-safety cathode material for aqueous zinc ion batteries because of its tunnel structure that facilitates the intercalates/de-intercalates of Zn2+. However, it has been a challenge to improve the rate performance of vanadium dioxide and its cycling stability at high current densities. Here, we report VO2(B) nanoflakes with petal-shaped folds at the top. Combine with a higher pseudocapacitance contribution and part of diffusion control, the VO2(B) led to higher electrochemical activity, quicker electron transfer kinetics and better electronic conductivity. The VO2(B) discovers a considerable capacity of 301.7 mA h g−1 at 1 A g−1, an impressive rate performance of 248.4 mA h g−1 after 1000 cycles at 5 A g−1,and 89.0 mA h g−1 at the current density of 50 A g−1. More surprisingly, the VO2(B) can keep 201.3 mA h g−1 after 2000 cycles at 10 A g−1, and obtain 101.4% high capacity retention. This method effectively improves the rate performance and long-cycle stability of vanadium dioxide, and also provides ideas for improving the performance of other cathode materials for aqueous zinc ion batteries.