Theoretical Prediction on the Catalytic Effect of Selenium-deficient WSe2 in Lithium-sulfur Batteries

Due to the excellent electrical conductivity, high specific surface area and large interlayer spacing, WSe2 has been used as catalytic material to effectively improve the electrochemical performance of lithium sulfur batteries. However, the active sites are concentrated at the few edges, which hinders the further improvement of catalytic activity. Manufacturing surface defects can expose more surface active sites and improve catalytic activity. Herein, theoretical study was carried out on the polysulfide adsorption, lithium ion migration and polysulfide conversion of selenium-deficient WSe2 with different vacancy concentrations(3.125%, 6.25%, 9.375% and 12.5%), to explore the application potential of Se-deficient WSe2 in Li-S batteries. It is revealed that medium vacancy concentration WSe2 (6.25%) has moderate polysulfide adsorption capacity, rapid lithium ion migration and synchronous promotion to charge and discharge process, which is the most advantageous surface. In comparison, the low vacancy(3.125%) defect surface is unfavorable to polysulfide adsorption, lithium ion migration and charge-discharge process. For the high vacancy defect surface(9.375% and 12.5%), although it is conducive to the lithium migration, it has too strong short chain polysulfides adsorption and unfavorable discharge process. The results provide theoretical guidance for the application of defective tungsten selenide in lithium sulfur battery.