Nitrogen-doped Mesoporous carbon promoted chemical adsorption of sulfur and fabrication of high-Areal-capacity sulfur cathode with exceptional cycling stability for lithium-sulfur batteries

As one important component of sulfur cathodes, the carbon host plays a key role in the electrochemical performance of lithium-sulfur (Li-S) batteries. In this paper, a mesoporous nitrogen-doped carbon (MPNC)-sulfur nanocomposite is reported as a novel cathode for advanced Li-S batteries. The nitrogen doping in the MPNC material can effectively promote chemical adsorption between sulfur atoms and oxygen functional groups on the carbon, as verified by X-ray absorption near edge structure spectroscopy, and the mechanism by which nitrogen enables the behavior is further revealed by density functional theory calculations. Based on the advantages of the porous structure and nitrogen doping, the MPNC-sulfur cathodes show excellent cycling stability (95% retention within 100 cycles) at a high current density of 0.7 mAh cm^-2 with a high sulfur loading (4.2 mg S cm^-2) and a sulfur content (70 wt%). A high areal capacity (≈3.3 mAh cm^-2) is demonstrated by using the novel cathode, which is crucial for the practical application of Li-S batteries. It is believed that the important role of nitrogen doping promoted chemical adsorption can be extended for development of other high performance carbon-sulfur composite cathodes for Li-S batteries. The nitrogen-doped mesoporous carbon material is found to chemically adsorb sulfur, and the related mechanism is revealed by experimental survey and density functional theory calculation. Taking full advantages of chemical adsorption of sulfur, MPNC-S cathode delivered an excellent capacity retention (95% within 100 cycles), high Coulombic efficiency (>96%), as well as high areal capacity of above 3 mAh cm^-2.