Rational Design of Dual-Functional Mo-Doped Co ₉ S ₈ Superstructures for Synergistic Sulfur Electrochemistry and Lithium Stabilization in Advanced Li–S Batteries

Lithium-sulfur (Li-S) batteries face significant challenges including polysulfide shuttling, sluggish redox kinetics, and Li dendrite growth. This work introduces molybdenum (Mo)-doped Co₉S₈ superstructures as a dual-function separator modifier to synergistically address these challenges. Atomic Mo doping, achieved through solvothermal synthesis, induces charge redistribution via Mo/Co₉S₈ electronic coupling, optimizing the d-band center to both enhance polysulfide adsorption and catalyze their conversion. The Li-S battery equipped with a Mo/Co₉S₈-modified polypropylene (PP) separator delivers a high reversible capacity of 1663.5 mA h g^-1 at 0.1 C, an exceptional rate capability of 593.4 mA h g^-1 at 5 C, and demonstrates long-term stability with 56.1% capacity retention after 1000 cycles at 1 C. Additionally, the Mo/Co₉S₈ modification layer helps reduce the inhomogeneity of Li⁺ flux distribution and enhance the stability of the metallic Li anode. Under strict operating conditions (0.5 mA cm^-2/1.0 mA h cm^-2), the Li-S battery equipped with a Mo/Co₉S₈-modified PP separator can stably operate for 400 h during the Li plating and stripping processes. This work is expected to provide new insights and approaches for designing separators that synergistically optimize the anodes and cathodes in Li-S batteries.