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.
Keywords: LiyVS2−x intermediates; Li−S batteries; catalytic conversion; lithium polysulfides; sulfur vacancies.