Group IV Monochalcogenides MX (M=Ge, Sn; X=S, Se) as Chemical Anchors of Polysulfides for Lithium-Sulfur Batteries.

Abstract

Although rechargeable lithium-sulfur batteries are considered as advanced energy systems, their practical implementation is impeded by many factors, in particular the rapid capacity fade and low Coulomb efficiency caused by the shuttle effect. To overcome this problem for achieving longer cycle life and higher rate performance, anchoring materials for lithium polysulfides are highly desirable. In this work, for the first time, we report phosphorene-like MX (M=Ge, Sn; X=S, Se) monolayers as promising anchoring materials to restrain the lithium polysulfides shuttling. Our study provides fundamental selection criteria for the effective suppression of the polysulfides shuttling. Adsorption calculations reveal that polysulfide capture by the MX is through chemisorption with a suitable range of adsorption energies. Morever, we show that excellent surface diffusion of Li and polysulfides endow a fast charge/discharge rate for lithium-sulfur batteries. Graphene with desirable electronic properties is constructed to improve the electrical conductivity in the new graphene@MX heterostructures. Based on the strong anchoring ability, improved rate capability, and enhanced conductivity, MX-based composites hold great promise as an anchoring material for high-energy lithium-sulfur batteries.