Vanadium nitride/carbon fiber engineered with oxygen defects and vertically aligned nanosheets for high-rate flexible aqueous zinc-ion batteries

Flexible aqueous zinc-ion batteries (AZIBs) are promising candidates for wearable devices owing to their high safety and low cost. However, their progress is plagued by sluggish ion-transport kinetics, which lead to inferior rate capability. Herein, oxygen defects and vertically aligned porous nanosheet architecture were engineered in VN/carbon fiber (VN/CF) cathode to overcome these issues. This structure was realized via the initial growth of vertically aligned V₂O₅ nanosheet templates on gas-spun carbon fibers, followed by high-temperature NH₃ treatment. The oxygen defects accelerate bulk diffusion kinetics within VN. Meanwhile, the vertically aligned VN nanosheet array possess lower charge-transfer resistances, enhancing surface diffusion kinetics. These features synergistically improve overall Zn²⁺ transport and thereby endow high-rate performance. Consequently, the free-standing VN/CF cathode exhibits exceptional rate performance, delivering a capacity of 263.4 mAh g^-1 even at a high current density of 10 A g^-1. When assembled into flexible AZIBs, the device exhibits a high-rate capability of 249.7 mAh g^-1 at 10 A g^-1 and stable performance even under various bending deformations, demonstrating significant potential for next-generation wearable devices.