Boosting Sulfur Catalytic Kinetics by Defect Engineering of Vanadium Disulfide for High-Performance Lithium-Sulfur Batteries

• Defective VS 2 nanosheets are successfully synthesized by solvothermal method. • Sulfur vacancies in defective VS 2 offer abundant coordination unsaturation sites. • Coordination unsaturation sites enhance the capture and catalysis of polysulfides. • Electrochemical investigation and DFT calculation reveal the catalytic mechanism. • Assembled Li-S batteries realize outstanding cyclic lifespan and rate performance. The incomplete sulfur conversion and serious shuttle effect caused by sluggish sulfur reduction reaction (SRR) kinetics of lithium polysulfides (LiPSs) have hindered the practical applications of lithium-sulfur (Li-S) batteries for many years. Developing efficient catalysts and fundamentally understanding the catalytic mechanism can largely promote the application of Li-S batteries. In this work, the metallic sulfur-defect vanadium disulfide (D-VS 2 ) nanosheets with large specific areas have been synthesized by a one-pot solvothermal method, and introduced as a modified layer on a polypropylene (PP) separator. Density functional theory (DFT) calculation and electrochemical investigations have revealed the essential catalytic mechanism from atomic level to macro-scale. The introduced sulfur vacancies in D-VS 2 can increase the coordination unsaturation sites, lead to the charge re-distribution on VS 2 nanosheets, and remarkably promote the chemical anchoring and catalytic kinetics of LiPSs in Li-S batteries. As a result, the D-VS 2 modified Li-S battery achieves a high initial discharge specific capacity of 1492.2 mAh g −1 at 0.1C and excellent cycling stability with a decay rate of 0.07% over 1000 cycles at 1.0C. Even under a high sulfur loading of 8.26 mg cm −2 , the battery can still obtain a superb areal capacity up to 6.2 mAh cm −2 after 60 cycles at 0.1C. These results suggest that the proposed defect engineering strategy is promising for advanced Li-S batteries.