Defect-Engineered VS2 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-VS₂ and V self-intercalated-type V_I-VS₂ and measured their catalytic activities in Li-S batteries. Compared with self-intercalating V atoms, S vacancies accelerated Li⁺ diffusion and S_V-VS₂ as a Li⁺ "reservoir" promoted the sulfur conversion kinetics significantly. In addition, the presence of sulfur vacancies promoted the lithiation behavior of S_V-VS₂ during discharge, leading to an enhancement of the catalytic ability of S_V-VS₂. However, this lithiation phenomenon weakened the catalytic activity of V_I-VS₂. Overall, S_V-VS₂ had better adsorption and catalytic activity. Li-S batteries with S_V-VS₂-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.