Tuning the Band Structure of MoS₂ <i>via</i> Co₉S₈@MoS₂ Core-Shell Structure to Boost Catalytic Activity for Lithium-Sulfur Batteries.

Abstract

The introduction of a dual-functional interlayer into lithium-sulfur batteries (LSBs) provides many opportunities for restraining the "shuttle effect" and enhancing sluggish sulfur conversion kinetics. Tuning the band structure of the metal sulfide provides an opportunity to enhance its catalytic activity, which plays an important role in suppressing the "shuttle effect" of lithium polysulfides (LiPSs) in LSBs. Here were present a Co₉S₈@MoS₂ core-shell heterostructure anchored to a carbon nanofiber (Co₉S₈@MoS₂/CNF), developed as an interlayer for suppressing the shuttle effect of LiPSs. The fabricated composite heterostructure is determined to be an effective alternative material that combines the synergistic relationship between chemisorption and electrochemical catalysis. We find that the band structure of the MoS₂ shell can be effectively tuned by the Co₉S₈ core and that the Co₉S₈@MoS₂/CNF can capture the LiPSs, providing excellent catalytic ability to convert LiPSs into Li₂S₂, with subsequent transformation from Li₂S₂ to Li₂S. Importantly, high capacities of 1002 and 986 mAh g^-1 can be retained after 50 cycles with high-sulfur loadings of 6 and 10 mg cm^-2. Our results highlight the design of an atomic-scale heterostructure as a multifunctional interlayer providing a synergistic relationship between adsorption and catalysis. The net result is an effective retardation of the shuttling of LiPSs and an enhancement of the electrochemical redox reactions of LiPSs. This work shows great promise toward the development of practical applications of LSBs.