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 VS nanosheets (VS) as catalysts for Li-S batteries and further study the catalytic mechanism of VS via ex situ X-ray diffraction and in situ UV-vis spectroscopy. A multifunctional S cathode was also obtained by assembling VS on a C cloth to achieve high S loading for Li-S batteries. It was found that VS catalysts undergo a lithiation process in the work voltage of Li-S batteries, and the triggered LiVS intermediates reciprocate VS with a high catalytic activity so as to enhance the performance of Li-S batteries by promoting the dissociation process of S to S. Consequently, Li-S batteries with a C/VS/S cathode deliver a high reversible capacity (1471 mAh g at 0.1 C) and good cycling performance (low fading rate of 0.064% per cycle after 400 cycles). Meanwhile, the CC@VS/S cathode with a high S areal loading of 5.6 mg cm can render a satisfactory areal capacity of 4.22 mAh cm at 0.2 C and a cycle stability of over 100 cycles. Therefore, the study on the catalysis of LiVS 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.