Boosting sulfur catalytic kinetics by defect engineering of vanadium disulfide for high-performance lithium-sulfur batteries

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-VS2) 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-VS2 can increase the coordination unsaturation sites, lead to the charge re-distribution on VS2 nanosheets, and remarkably promote the chemical anchoring and catalytic kinetics of LiPSs in Li-S batteries. As a result, the D-VS2 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.