VNxOy@C Nanowires: A High-Performance Cathode Material for Aqueous Zinc-ion Batteries with Dual-Redox Reaction Mechanisms

Vanadium nitride (VN), with appealing advantages of large specific capacity, metalloid high conductivity, is attracting intensive interest in the field of aqueous zinc-ion batteries (ZIBs), whereas faces challenges such as inferior structure stability and sluggish kinetics. In this work, VNxOy@C hybrid nanowires (VNO@C) with abundant oxygen-defects and carbon coating were designed and prepared via integrating the modification strategies of microstructure design, energy storage mechanism optimization, and carbon coating. The combined structural characteristics including carbon-coated conductive network, abundant oxygen defects and the nanofiber structure can effectively facilitate the internal electron and ion transport, greatly augmenting the electrochemical reaction kinetics of the electrode. Meanwhile, ex-situ XPS characterization reveals an optimized energy storage mechanism of VNO@C, that is, a dual redox reaction involving both anions and cations (V3+↔V2+/N3−↔N2−), which further accelerate the electrochemical reaction process and enhance the specific capacity. Benefiting from these advantages, the obtained VNO@C cathode can deliver 433.2 mAh g-1 (at 0.1 A g-1) and maintain a capacity retention rate of 83.1% after 1000 cycles (at 5 A g-1). This research shed new perspective on the design of novel structured VN-based materials for superior ZIBs.