Insights into the Dynamic Catalytic Effect of Metal Sulfides with Prominent Lithiation Process in the Application of Li–S Batteries

A common recognition to upgrade the kinetics of Li-S batteries is the adoption of catalysts. However, most of the popular catalysts possess remarkable lithiation characteristics in a working Li-S system, and the changes of their chemical state during the prominent lithiation process and the induced influence toward the catalytic mechanism are rarely investigated. Herein, VS4 with unique valance state change of element S (S22- ↔ S2-) and V (V4+ ↔ V5+) during the lithiation/delithiation process is selected as the representative catalyst to gain a deep insight into the dynamic catalytic effect in the application of Li-S batteries. The comprehensive analyses and the density functional theory simulation reveal that, compared to the original state of VS4, the lithiation state of VS4 (denoted as LixVS4) is able to impose a stronger affinity toward lithium polysulfide (LiPS), further weaken the S-S bond and lower the activation energy of LiPS conversion, as well as accelerate the conversion kinetics in Li-S chemistry. In this way, induced by the lithiation activity of the catalysts, a perspective for the dynamic catalytic effect is proposed for Li-S chemistry, which can open up a way for the catalytic study of other similar metal compounds. Furthermore, by taking the advantage of the dynamic catalytic mechanism of LixVS4 and the high specific capacity of S, a Li-S configuration is proposed by hybridizing VS4 and S, which can achieve excellent cycling stability and superior rate capability under a challenging 90 wt % dual-active material ratio.