Electrochemically induced phase transition in a nanoflower vanadium tetrasulfide cathode for high-performance zinc-ion batteries

Aqueous zinc-ion batteries (AZIBs) are promising contenders for large-scale energy storage with the merits of their low cost, high safety, environmental friendliness, and competitive gravimetric energy density. Nevertheless, suitable cathode materials with long cycle life and adequate capacity are still rare. Herein, we report a nanoflower vanadium tetrasulfide/carbon nanotubes (VS4/CNTs) cathode with high Zn-storage performance. We propose a phase transition reaction mechanism from VS4 to zinc pyrovanadate in the initial cycles and a reversible intercalation mechanism for Zn2+ in zinc pyrovanadate during subsequent cycles. As a result, the cathode delivers a high discharge capacity of 265 mAh g−1 at 0.25 A g−1 and 182 mAh g−1 at 7 A g−1. In addition, the cathode exhibits a long-term cyclability with 93% capacity retention over 1200 cycles at 5 A g−1. VS4/CNTs with superior electrochemical performance is a hopeful cathode material in AZIBs.