Defect-Engineered VS 2 Electrocatalysts for Lithium-Sulfur Batteries.

Defective two-dimensional transition metal dichalcogenides can be effective electrocatalysts for Li-S batteries, but the relationship between defect types and battery performance is unclear. In this work, we designed S vacancy-type S V -VS 2 and V self-intercalated-type V I -VS 2 and measured their catalytic activities in Li-S batteries. Compared with self-intercalating V atoms, S vacancies accelerated Li + diffusion and S V -VS 2 as a Li + "reservoir" promoted the sulfur conversion kinetics significantly. In addition, the presence of sulfur vacancies promoted the lithiation behavior of S V -VS 2 during discharge, leading to an enhancement of the catalytic ability of S V -VS 2 . However, this lithiation phenomenon weakened the catalytic activity of V I -VS 2 . Overall, S V -VS 2 had better adsorption and catalytic activity. Li-S batteries with S V -VS 2 -coated separators delivered high rate performance and excellent cycling stability, with a capacity decay rate of 0.043% over 880 cycles at 1.0 C. This work provides an effective strategy for designing efficient Li-S battery electrocatalysts using defect engineering.