Stable structure and fast ion diffusion: N-doped VO 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 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 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 precursor assists the final product in exhibiting a more stable three-dimensional nanoflower structure. In particular, the N-doped VO cathode shows excellent cycle stability and superior rate capability with the delivered capacities of 165.02 mAh g and 85 mAh g, at 10 A g and 30 A g, 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. Hence, this work provides a new avenue for designing unique nanostructured vanadium oxides and developing electrode materials suitable for ultrafast charging.