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Lithium-sulfur batteries are very promising next-generation energy storage batteries due to their high theoretical specific capacity. However, the shuttle effect of lithium-sulfur batteries is one of the important bottlenecks that limits its rapid development. Herein, physical and chemical dual adsorption of lithium polysulfides are achieved by designing a novel framework structure consisting of MnO2, reduced graphene oxide (rGO), and carbon nanotubes (CNTs). The framework-structure composite of MnO2/rGO/CNTs is prepared by a simple hydrothermal method. The framework exhibits a uniform and abundant mesoporous structure (concentrating in ~12 nm). MnO2 is an α phase structure and the α-MnO2 also has a significant effect on the adsorption of lithium polysulfides. The rGO and CNTs provide a good physical adsorption interaction and good electronic conductivity for the dissolved polysulfides. As a result, the MnO2/rGO/CNTs/S cathode delivered a high initial capacity of 1201 mAh g−1 at 0.2 C. The average capacities were 916 mAh g−1, 736 mAh g−1, and 547 mAh g−1 at the current densities of 0.5 C, 1 C, and 2 C, respectively. In addition, when tested at 0.5 C, the MnO2/rGO/CNTs/S exhibited a high initial capacity of 1010 mAh g−1 and achieved 780 mAh g−1 after 200 cycles, with a low capacity decay rate of 0.11% per cycle. This framework-structure composite provides a simple way to improve the electrochemical performance of Li-S batteries.

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Lithium-sulfur (Li-S) batteries have attracted increasing attention due to their high theoretical capacity, being a promising candidate for portable electronics, electric vehicles and large-scale energy storage. The interactions of bilayer structured graphitic CN (bi-CN) with S, lithium polysulfides (LiPSs), 1,3-dioxolane, 1,2-dimethoxyethane and tetrahydrofuran ether-based solvents have been studied using first-principles calculations. It has been found that the (micropore-scale) interlayer of bi-CN shows intimate contact and strong binding with S and LiPSs due to the formation of chemical Li-N bonds. The incorporation of soluble LiPSs by the wrinkled layers of bi-CN with 5.5-7.2 Å interlayer pores can suppress the shuttling effect. The interlayer ultramicropores with interlayer distances of <4 Å can accommodate the small LiS and LiS molecules, and impede the irreversible reaction between the solvents and the LiPSs. The calculated energy gap of bi-CN decreases to be narrow during lithiation. Our results can provide a guideline for promoting the electrochemical performance of microporous g-CN/sulfur composites for Li-S batteries.