Stable structure and fast ion diffusion: N-doped VO2 3D porous nanoflowers for applications in ultrafast rechargeable aqueous zinc-ion batteries

Aqueous rechargeable zinc-ion batteries (ARZIBs) are promising candidates for fast-charging energy-storage systems. The issues of stronger interactions between Zn 2+ and the cathode for ultrafast ARZIBs can be partially addressed by enhancing mass transfer and ion diffusion of the cathode. Herein, via thermal oxidation for the first time, N -doped VO 2 porous nanoflowers with short ion diffusion paths and improved electrical conductivity were synthesized as ARZIBs cathode materials . The introduction of nitrogen derived from the vanadium-based-zeolite imidazolyl framework (V-ZIF) contributes to enhanced electrical conductivity and faster ion diffusion, while the thermal oxidation of the VS 2 precursor assists the final product in exhibiting a more stable three-dimensional nanoflower structure. In particular, the N -doped VO 2 cathode shows excellent cycle stability and superior rate capability with the delivered capacities of 165.02 mAh g −1 and 85 mAh g −1 , at 10 A g −1 and 30 A g −1 , and the capacity retention of 91.4% after 2200 cycles and 99% after 9000 cycles, respectively. Remarkably, the battery takes less than 10 s to be fully charged at 30 A g −1 . Hence, this work provides a new avenue for designing unique nanostructured vanadium oxides and developing electrode materials suitable for ultrafast charging.