An ultrasmall structure-optimized vanadium oxides integrated into nitrogen-doped bead-chain-like hollow carbon nanofibers for advanced flexible cathode of zinc ion batteries.

With the rapid advancement of science and technology, rechargeable aqueous zinc ion batteries (AZIBs) has garnered increasing attention in consideration of security, chemical stability and cost-effectiveness. Vanadium-based oxides have emerged as a promising high-performance electrode materials for AZIBs, owing to their high energy density, rich crystal configurations, and simple preparation process. However, the practical application of vanadium oxides is hindered by their low ion/electron transfer rate and significant capacity fading during electrochemical reactions. To address these limitations, an ultrasmall vanadium oxides nanoparticles in-situ integrated into nitrogen-doped bead-chain-like hollow carbon nanofibers (VO@NHCNFs) are developed through an electrospinning technique combined with a template method. By precisely controlling NHCNFs nanostructures and electrochemical oxidation conditions, favorable structural evolution is achieved after phase transformation due to nanoscale crystalline grain, ultrathin porous carbon layer and introduced structural water for vanadium oxides. The unique NHCNFs structure and favorable phase transformation significantly enhances the zinc storage capacity, rate capability, and cycling stability of the VO@NHCNFs electrode, demonstrating a remarkable reversible capacity of 443.8 mAh·g at 0.5 A·g. Furthermore, the VO@NHCNFs electrode exhibits high initial capacities of 392.1 mAh·g and 212.2 mAh·g at current densities of 2.0 A·g and 20.0 A·g, respectively, retaining 72.6% of its capacity after 500 cycles and 76% of its capacity after 4000 cycles. Notably, this innovative approach can be broadly applied to the design of other oxide materials, offering significant potential for the development of high-performance and self-supporting electrodes in next-generation energy storage devices.