Unravel the Catalytic Effect of Two-Dimensional Metal Sulfides on Polysulfide Conversions for Lithium–Sulfur Batteries

Despite extensive studies, the role of polar chemical interfaces on carrier materials anchoring polysulfide species remains an ambiguous but intriguing topic for lithium–sulfur batteries. Herein, to further investigate the effect of metal sulfides in the conversion of polysulfides, three kinds of M_xS_y (M = Cr, Mo, and W) are chosen and prepared in the forms of two-dimensional M_xS_y/C composites via a method using NaCl as a template and a subsequent high-temperature sulfuration process. Compared with a blank sample, the three composites exhibit superior adsorption of soluble polysulfides and faster kinetics of the deposition of Li₂S₂/Li₂S, especially on Cr₃S₄/C and WS₂/C. These differences in performances of the three composites are further evaluated by the values of the Gibbs free energy in each step of polysulfide conversion. In the conversion processes of Li₂S₄ to Li₂S₂ and then to Li₂S, the values are more negative on Cr₃S₄ and WS₂, showing stronger promotion abilities for the formation of Li₂S than MoS₂. This work can effectively deepen the role of metal sulfides in the conversion process of polysulfides and provide valuable insights into the design of superior carriers for lithium–sulfur batteries.