Selenium Defect Boosted Electrochemical Performance of Binder-Free VSe2 Nanosheets for Aqueous Zinc-Ion Batteries.

As a typical transition-metal dichalcogenides, vanadium diselenide (VSe2) is a promising electrode material for aqueous zinc-ion batteries due to its metallic characteristics and excellent electronic conductivity. In this work, we propose a strategy of hydrothermal reduction synthesis of stainless-steel (SS)-supported VSe2 nanosheets with defect (VSe2-x-SS), thereby further improving the conductivity and activity of VSe2-x-SS. Density functional theory calculations confirmed that Se defect can adjust the adsorption energy of Zn2+ ions. This means that the adsorption/desorption process of Zn2+ ions on VSe2-x-SS is more reversible than that on pure SS-supported VSe2 (VSe2-SS). As a result, the Zn//VSe2-x-SS battery showed more excellent electrochemical performance than Zn//VSe2-SS. The VSe2-x-SS electrode shows a good specific capacity of 265.2 mA h g-1 (0.2 A g-1 after 150 cycles), satisfactory rate performance, and impressive cyclic stability. In addition, we also have explored the energy-storage mechanism of Zn2+ ions in this VSe2-x-SS electrode material. This study provides an effective strategy for the rational design of electrode materials for electrochemical energy-storage devices.