Insight into the Anchoring and Catalytic Effects of VO₂ and VS₂ Nanosheets as Sulfur Cathode Hosts for Li–S Batteries

Abstract

Transition metal oxides and sulfides have been intensively investigated as host materials for the S cathode in lithium-sulfur (Li-S) batteries; however, the distinctions between them in battery operation have remained unclear. In this study, VO₂ and VS₂ nanosheets were systematically studied as host materials for Li-S batteries through theoretical calculations and experimental testing. First-principles calculations demonstrated that VS₂ showed more favorable properties, including the inherent semi-metallic conductivity of VS₂ , moderate adsorption strength for Li₂ S_n , fast Li⁺ transport with a low diffusion barrier, and accelerated surface redox reactions with a low Li₂ S decomposition barrier. In comparison, the low electronic conductivity and strong adsorption strength of VO₂ increased Li⁺ diffusion as well as Li₂ S decomposition barriers of the electrode, resulting in relatively poor rate capability and cycle stability. In experiments, the VS₂ @S electrode exhibited superior electrochemical performance compared with VO₂ @S, giving a large capacity of 713 mAh g^-1 at 5 C and a low capacity fading rate of 0.13 % per cycle over 200 cycles at 1 C. The constructed relationships between S cathode and host materials could guide the future design of high-performance S cathodes for Li-S batteries.