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.