Tungsten-regulated metal-phase vanadium dioxide (M) for high-performance aqueous zinc-iodine batteries

Aqueous zinc-iodine batteries (AZIBs) have broad application prospects in large-scale energy storage due to their intrinsic safety, high energy/power density, and low cost. However, the iodine cathode still faces challenges such as shuttle effect and slow conversion kinetics. Herein, the tungsten-regulated metal-phase vanadium dioxide (W-VO 2 (M)) is proposed to improve the whole performance of AZIBs. First, a heat-treatment method is applied to achieve the phase transition to prepare W-VO 2 (M) from the precursor of the tungsten introduced B-phase vanadium dioxide. Via various characterizations, the successful tungsten introducing is confirmed by occupying the vanadium position and forming the tungsten-oxygen bond in the VO 2 (M) lattice. The obtained W-VO 2 (M) is used as the functional separator modifier of AZIBs, which deliver high capacity, superior rate performance, and long-cycling stability. Specifically, the capacity is 133.8 mAh g −1 after 500 cycles at 1 C. When at 3, 5, 7, 10 C, the corresponding capacities are 127.6, 115.9, 106.5, and 95.5 mAh g −1 , respectively. The battery can stably work 5000 cycles at 10 C. A series of analyses suggest that the W-VO 2 (M) can inhibit shuttle effect and accelerate the iodine conversion kinetics via the adsorbing and anchoring of iodine species. This research provides a new perspective for advanced AZIBs.