Monodispersed flower-like MXene@VO2 clusters for aqueous zinc ion batteries with superior rate performance

Monoclinic B phase VO2 with a distinctive tunnel structure is regarded as a viable cathode material for use in aqueous zinc ion batteries (AZIBs). However, the low electron conductivity and poor rate performance prevent it from being used further. Herein, we report 3D flower-like MXene nanosheets loaded with the VO2 cluster (MXene@VO2) synthesized via a one-step hydrothermal process, where MXene nanosheets were spontaneously stacked as a skeleton for the growth of VO2 nanobelts. The synergistic effect between MXene nanosheets with high electronic conductivity and VO2 nanobelts with a unique tunnel structure benefitted the electron and Zn2+ transport; the 3D hybrid structure with a high specific surface area provided an increased contact area with the electrolyte and a shortened distance of the Zn2+ transfer path. As a result, this material exhibits a promising Zn2+ storage behavior with a superior rate capability (363.2 mA h g-1 at 0.2C and 169.1 mA h g-1 at 50C) and outstanding long-cycling performance (206.6 mA h g-1 and 76% capacity retention over 5000 cycles at 20C). In addition, a self-charging battery could be prepared by using oxygen in air to oxidize vanadium oxide with lower valence states. Our prepared MXene@VO2 composite with a synergistic effect has been proved to be a promising cathode for AZIBs, offering a progressive paradigm for the development of AZIBs.