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

AbstractCatalyzing 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 S8 to Li2S4 through adsorbing Li2S8 and extending its S─S bond distance. Then, the kinetics of Li2S precipitation is enhanced by facilitating the migration of Li2S4 from MoC to MoSe2. This is driven by the internal electric field at the heterogeneous interface and the low diffusion energy barrier on MoSe2 for Li2S4. Moreover, MoC‐MoSe2 exhibits the smallest degree of Li2S2 disproportionation throughout the reduction process. Consequently, the cell with MoC‐MoSe2/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.