Vanadium nitride oxide quantum dots modified nitrogen-doped graphene as cathode for high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are attractive due to their high safety, cost-effectiveness, and environmental friendliness, but face challenges such as cathode dissolution, instability, and limited cycle life. Herein, vanadium nitride oxide (VNO) quantum dots are successfully anchored on the surface of nitrogen-doped graphene (VNO/graphene) using a facile pyrolysis process. The resulting VNO/graphene composite is enriched with active sites and features a short ion diffusion path, which can be partially ascribed to the high conductivity and fast charge transfer pathways of the nitrogen-doped graphene. Furthermore, the weaving of the N-doped graphene in VNO/graphene is effective in preventing the aggregation of VNO and mitigating the capacity degradation to some extent. As a result, the assembled AZIB cell using VNO/graphene as the cathode exhibits outstanding electrochemical performance, with a notable specific capacity of 532 mAh g⁻¹ at 0.2 A g⁻¹, along with remarkable rate performance and satisfactory cycling stability. In addition, the phase transformation of the VNO/graphene during the charging/discharging process is elucidated with the aid of in-situ Raman spectroscopy and ex-situ XRD. This work highlights the potential of the VNO/graphene composite as a cathode material for AZIBs and provides valuable insights for the development of advanced materials for energy storage devices.