MoC‐MoSe2 Heterostructures as Multifunctional Catalyst Toward Promoting the Stepwise Polysulfide Conversion for Lithium‐Sulfur Batteries

Abstract Catalyzing polysulfides conversion for lithium‐sulfur batteries is an efficient strategy to overcome the sluggish kinetics of polysulfides conversion as well as its serious shuttling effect. Due to the multistep and complicated phase transformation of sulfur species, the monofunctional catalyst can hardly promote the overall polysulfides redox process. Herein, a molybdenum‐based heterostructure is proposed, that facilitates the entire reduction process by tandemly catalyzing liquid‐liquid conversion and liquid‐solid conversion. It is uncovered that the MoC physiochemically immobilizes the soluble long‐chain polysulfide and accelerates the conversion between S 8 to Li 2 S 4 through adsorbing Li 2 S 8 and extending its S─S bond distance. Then, the kinetics of Li 2 S precipitation is enhanced by facilitating the migration of Li 2 S 4 from MoC to MoSe 2 . This is driven by the internal electric field at the heterogeneous interface and the low diffusion energy barrier on MoSe 2 for Li2S 4 . Moreover, MoC‐MoSe 2 exhibits the smallest degree of Li 2 S 2 disproportionation throughout the reduction process. Consequently, the cell with MoC‐MoSe 2 /C/S cathode delivers an initial discharge‐specific capacity of 841.1 mAh g −1 and long‐term cycling stability with a capacity attenuation rate of 0.08% per cycle at 1.0 C. This work presents a novelty view to design a rational multifunction catalyst for sequentially accelerating the stepwise conversion of polysulfides.