Defect-Engineered VS2 Electrocatalysts for Lithium-Sulfur Batteries

Defective two-dimensional transition metal dichalcogenidescanbe effective electrocatalysts for Li-S batteries, but the relationshipbetween defect types and battery performance is unclear. In this work,we designed S vacancy-type S-V-VS2 and V self-intercalated-typeV(I)-VS2 and measured their catalytic activitiesin Li-S batteries. Compared with self-intercalating V atoms,S vacancies accelerated Li+ diffusion and S-V-VS2 as a Li+ "reservoir" promotedthe sulfur conversion kinetics significantly. In addition, the presenceof sulfur vacancies promoted the lithiation behavior of S-V-VS2 during discharge, leading to an enhancement of thecatalytic ability of S-V-VS2. However, this lithiationphenomenon weakened the catalytic activity of V-I-VS2. Overall, S-V-VS2 had better adsorptionand catalytic activity. Li-S batteries with S-V-VS2-coated separators delivered high rate performance and excellentcycling stability, with a capacity decay rate of 0.043% over 880 cyclesat 1.0 C. This work provides an effective strategy for designing efficientLi-S battery electrocatalysts using defect engineering.