Boosting the Rate Capability of Aqueous Zinc-Ion Batteries Using VN_xO_y/C Spheres Derived from a Self-Assembled V-polydopamine Complex

While vanadium oxides have garnered interest due to their high capacity and abundant valence states in aqueous zinc-ion batteries (AZIBs), there are many challenges to achieving long cycling stability and excellent rate capability resulting from poor electronic conductivity and sluggish reaction dynamics. Herein, we design a cathode material VNxOy/C derived from a self-assembled V-polydopamine complex via a one-step organic-inorganic hybrid reaction. Benefiting from a well-organized structure and nanosized particle embedding, the asprepared VNxOy phase could favor zinc-ion insertion/extraction due to the strong affinity of N element with Zn2+. Systematic investigations show that the controllable strategy yields positive effects on the electrochemical performances including enhanced rate capability and cycling stability, which are superior to those of the V2O3/C cathode. As a result, we have achieved fast charging/discharging capability at 10 A g(-1) and stability exceeding 700 cycles at 3 A g(-1) with nearly 100% Coulombic efficiency. Interestingly, the pouch-cell-like devices with similar to 24 mAh could light an LED effectively. This work may pave the way to obtaining highly active V-containing compounds with structure design to improve electrochemical performances of AZIBs.