Rapid internal conversion harvested in Co/Mo dichalcogenides hollow nanocages of polysulfides for stable Lithium-Sulfur batteries

The sluggish conversion kinetics of the lithium polysulfide (LiPS) intermediates are hindering the practical application of lithium sulfur batteries (LSB) by their low efficiency and low cycle stability. To tackle these challenges, a rapid internal conversion (RIC) mechanism is proposed for the first time to accelerate the liquid-solid conversion in the sulfur reduction reaction (SRR) kinetics. It is reaveled that the reaction energy barrier in the SRR lies in the liquid-solid conversion, from Li2S4 to LiS2* to Li2S2. To accelerate the liquid-solid conversion, the CoS2@MoS2 hollow nanocage, a novel sulfur cathode, with the rational synergistic active site configuration is specifically designed toward a well-managed reaction path and sulfurphilic structure to regulate and modulate Li (LiPS)-S(sulfide) and S(LiPS)-M(sulfide) bonds prominently, affecting on activating reactants and stablizing transition states. Based on the RIC mechanism in the SRR, the stronger S-Co bonds between CoS2 and LiPS traps Li2S4 and catalytically facilitates S-S bond scission while the MoS2 is conducive to the migration of Li2S4 by weaker Li-S bonds. The unique synergetic conversion and catalytic functions is confirmed by density functional theory (DFT) calculations. The RIC mechanism could provide a new idea for exploring the conversion-catalysis material of Li-S batteries in the specific material design.