Mo-O-C Between MoS2 and Graphene Toward Accelerated Polysulfide Catalytic Conversion for Advanced Lithium-Sulfur Batteries

MoS2/C composites constructed with van der Waals forces have been extensively applied in lithium-sulfur (Li-S) batteries. However, the catalytic conversion effect on polysulfides is limited because the weak electronic interactions between the composite interfaces cannot fundamentally improve the intrinsic electronic conductivity of MoS2. Herein, density functional theory calculations reveal that the MoS2 and nitrogen-doped carbon composite with an Mo-O-C bond can promote the catalytic conversion of polysulfides with a Gibbs free energy of only 0.19 eV and a low dissociation energy barrier of 0.48 eV, owing to the strong covalent coupling effect on the heterogeneous interface. Guided by theoretical calculations, a robust MoS2 strongly coupled with a 3D carbon matrix composed of nitrogen-doped reduced graphene oxide and carbonized melamine foam is designed and constructed as a multifunctional coating layer for lithium-sulfur batteries. As a result, excellent electrochemical performance is achieved for Li-S batteries, with a capacity of 615 mAh g(-1) at 5 C, an areal capacity of 6.11 mAh cm(-2), and a low self-discharge of only 8.6% by resting for five days at 0.5 C. This study opens a new avenue for designing 2D material composites toward promoted catalytic conversion of polysulfides.