A Class of Catalysts of BiOX (X = Cl, Br, I) for Anchoring Polysulfides and Accelerating Redox Reaction in Lithium Sulfur Batteries.

Abstract

The lithium-sulfur battery system contains a complex reaction process of sulfur involving multielectron reactions and phase conversions. Moreover, the diffusion of intermediate polysulfides during reduction and sluggish kinetic conversion of polysulfides into insoluble Li2S still plague the use of Li-S batteries. Herein, BiOX was employed as sulfur host material in Li-S batteries, which could integrate suppression of the shuttle effect and promote kinetics redox reactions of lithium polysulfides. The polar BiOX displays a robust chemical adsorption ability with polysulfides, and the electrocatalytic activity of BiOX would accelerate the fragmentation of polysulfides into shorter chains. The results indicate that the good polysulfide reactivity not only ensures the effective reduction of polarization but also performs high discharge capacity and stable cycle performance. The battery with a BiOCl/G-S cathode reveals a high capacity of 1414 mA h/g at a current of 0.1 C and a low capacity decay rate of 0.007% during 2000 cycles at a current of 2 C. This work proposes the prospect of application of the BiOX materials in lithium sulfur batteries.