Engineering sulphur vacancy in VS2 as high performing zinc-ion batteries with high cyclic stability

Abstract

Metal dichalcogenides have been widely investigated in various energy storage devices in the past decades due to their large interlayer spacing formed by the weak van der Waals force between the layers. Among the various metal dichalcogenides, vanadium disulphide (VS₂) has recently been demonstrated as a potential cathode in zinc-ion batteries (ZIBs) exhibiting encouraging electrochemical performance and excellent reversible Zn²⁺ storage. However, the main challenge for VS₂ is its less-than-satisfactory capacity of ca. 150–160 mA h g⁻¹. As such, this work proposes the use of the sulphur vacancy defect engineering strategy to further enhance the electrochemical performance of VS₂. The as-assembled Zn//sulphur deficient VS₂ cell (denoted as D-VS₂) is able to deliver a high specific capacity of 262 mA h g⁻¹ at a current density of 0.1 A g⁻¹, which is ca. 1.75 times higher as compared to pristine VS₂, i.e., 150 mA h g⁻¹ at 1 A g⁻¹. Furthermore, the cyclic stability of Zn//D-VS₂ is also superior as compared to its counterpart with pristine VS₂ as the cathode (Zn//P-VS₂). Zn//D-VS₂ can achieve a capacity retention of 94% after 524 hours of continuous deep cycling, while Zn//P-VS₂ can achieve only 81% retention after about 270 hours of deep cycling. Hence, based on this work, it is expected that sulphur vacancy defect engineering could be a viable strategy to enhance the electrochemical performance of not only VS₂, but also of various metal dichalcogenides.