Insight into the Catalytic Role of Defect-Enriched Vanadium Sulfide for Regulating the Adsorption–Catalytic Conversion Behavior of Polysulfides in Li–S Batteries

The performance promotion of Li–S batteries relies primarily on inhibition of the shuttle effect and improvement of the catalytic-conversion reaction kinetics of polysulfides. Herein, we prepare defect-enriched VS2 nanosheets (VS2–x) as catalysts for Li–S batteries and further study the catalytic mechanism of VS2–x via ex situ X-ray diffraction and in situ UV–vis spectroscopy. A multifunctional S cathode was also obtained by assembling VS2–x on a C cloth to achieve high S loading for Li–S batteries. It was found that VS2–x catalysts undergo a lithiation process in the work voltage of Li–S batteries, and the triggered LiyVS2–x intermediates reciprocate VS2–x with a high catalytic activity so as to enhance the performance of Li–S batteries by promoting the dissociation process of S62– to S3•–. Consequently, Li–S batteries with a C/VS2–x/S cathode deliver a high reversible capacity (1471 mAh g–1 at 0.1 C) and good cycling performance (low fading rate of 0.064% per cycle after 400 cycles). Meanwhile, the CC@VS2–x/S cathode with a high S areal loading of 5.6 mg cm–2 can render a satisfactory areal capacity of 4.22 mAh cm–2 at 0.2 C and a cycle stability of over 100 cycles. Therefore, the study on the catalysis of LiyVS2–x intermediates provides a scientific view for revealing the catalysis mechanism of a sulfide-based electrocatalyst and boosting the development of an electrocatalyst for Li–S batteries.