Superlattice and defect engineering enabled NC@VS2–x as trifunctional promoter for polysulfides catalytic conversion

Abstract

The shuttling effect and sluggish reaction kinetics of the intermediate lithium polysulfides (LiPSs) are the main barriers limiting the application of Li–S batteries. Herein, superlattice and sulfur-vacancy engineering are concurrently constructed in the N-doped carbon embedded VS2 (NC@VS2–x) for LiPSs catalytic conversion. The superlattice and defect engineering with NC imbedded produce high activity trapping sites, enhance the electronic conductivity, and provide fast Li diffusion channels, achieving the massive precipitation of Li2S, promoting the dissolution of solid sulfur species, and accelerating the Li ions transport. Therefore, the trifunctional LiPSs promoter in Li–S cell yields high rate performance (4.0 C) and a low capacity decay rate of 0.036% at 2.0 C. Impressively, the NC@VS2–x cell delivers a capacity of 5.15 mA h cm−2 with S loading of 6.2 mg cm−2 and lean E/S ratio of 4.0 µL mg−1. When assembled in the pouch cell, the NC@VS2–x electrode can work well over 45 cycles, indicating a potential application in practical Li–S batteries. The proposed dual-engineering strategy to form the trifunctional promoter is anticipated to be applied in other multielectron energy related systems.