A highly stable aqueous Zn/VS2 battery based on an intercalation reaction

Abstract The complicated battery reaction mechanism and the limited reversibility of the aqueous zinc ion batteries (ZIBs) significantly hindered their practical application. Herein, we prepared a common VS2 nanosheets, which was further employed as cathode for ZIBs to clarify its Zn2+ storage mechanism. The Zn/VS2 battery electrochemical reaction mechanism was experimentally demonstrated, by using XPS, ex- and in-situ Raman, as an intercalation/conversion combination reaction. Of which, the intercalation reaction in 0.4–1.0 V is reversible, while the conversion reaction in 0.8–1.0 V is irreversible. The battery cycled in 0.4–1.0 V shows a limited cyclability and energy efficiency. By controlling the recharge depth to 0.8 V, the irreversible conversion in 0.8–1.0 V can thus be blocked. The battery operated in the optimized voltage window shows a high capacity of ~118.3 mAh g−1 over 200 cycles. Moreover, a high energy efficiency of ~83.6% can be retained after 350 cycles, which could be attributed to the lower charge/discharge voltage gap and the suppression of the irreversible reactions. We believe that this work could further enhance the fundamental understanding of the Zn2+ ions’ storage mechanism of the layered-type transition metal dichalcogenides and serves as a new guideline for their future optimization.