Sulfur-functionalized vanadium carbide MXene (V2CS2) as a promising anchoring material for lithium–sulfur batteries

Abstract

The development of lithium–sulfur (Li–S) batteries is hindered by capacity loss due to lithium polysulfide (LIPS) dissolution into electrolyte solutions (known as the “shuttle effect”). MXenes with excellent electrical conductivity, high mechanical strength and multiple possible active two-dimensional surface terminations are attracting much attention as anchoring materials of Li–S batteries. Here, the S-functionalized V₂C (V₂CS₂) is designed and demonstrated to have not only dynamic and thermal stability, but also metallic character. Compared with bare V₂C and V₂CO₂, V₂CS₂ exhibits a moderate adsorption effect to suppress the “shuttle effect” and can preserve the structure of LIPSs without any decomposition. Moreover, the metallic properties of V₂CS₂ are maintained after LIPSs are adsorbed, which can promote the electrochemical activity during the charge and discharge process. The low energy barriers of Li₂S decomposition and Li diffusion on the V₂CS₂ surface promise the phase transformation of LIPSs and assist the electrochemical process. Based on these remarkable results, we can conclude that V₂CS₂ is a promising anchoring material for lithium–sulfur batteries. Our work may also inspire the exploration of other MXenes and new surface functionalization methods to improve the performance of MXenes as host materials for high performance Li–S batteries.