锂硫电池中硒缺陷WSe2催化性能的理论研究

二硒化钨具有优异导电性、高比表面积和大间距层状结构等特点,能作为催化材料有效提升锂硫电池的性能;然而少量的边缘活性位点阻碍了其催化活性的进一步提升.通过引入原子空位制造表面缺陷,可使其暴露更多的表面活性位点,提高催化活性.本文通过第一性原理计算考察了不同Se空位缺陷浓度(3.125%,6.25%,9.375%和12.5%)WSe₂表面的多硫化物吸附能力、锂离子迁移能力和多硫化物转化能力,探究了缺陷改性硒化钨在锂硫电池中的应用潜力.结果表明,6.25%中等空位缺陷浓度的WSe₂表面具有适中的多硫化物吸附能力、快速的锂离子迁移和对于充电放电过程的同步促进作用,是最优势的表面;3.125%的低空位缺陷WSe₂表面对于多硫化物吸附、锂离子迁移和充放电过程均不利;9.375%和12.5%的高空位缺陷WSe₂表面虽然有利于锂离子迁移,但是对于短链多硫化物的吸附能力过强，同时不利于放电过程.

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.