Supramolecular macrocycle grafted Nb-MXene nanosheets constructing self-supporting framework for high-performance lithium-sulphur batteries

The advancement of lithium-sulphur (Li-S) batteries with high-energy density has been hindered by the high energy conversion barrier of sulphur and the shuttle effect of polysulfides. In this study, we successfully graft monocarboxylic pillar[5]arene (PA5-COOH) onto niobium carbide MXene (NbCT) through an esterification reaction to obtain the PA5-COOH/NbC hybrid multi-functional separator. The incorporation of organic molecules increases the interlayer spacing, creating more active sites for capturing polysulfides. Through a combination of experimental and theoretical calculations, we find that the presence of the organic macromolecular structure can facilitate rapid polysulfide conversion, while NbCT provides support sites for PA5-COOH and its larger specific surface area helps mitigate sulphur volume changes. By equipping Li-S batteries with a PA5-COOH/NbC separator, the Li-S battery supports an impressive reversible specific capacity of 1317mAh g at 0.2C and demonstrates exceptional rate performance (303 mAh g at 10C). The incorporation of the PA5-COOH/NbC hybrid separator expands the application potential of organic macrocyclic molecules and presents a stable self-support structure for developing high-performance lithium-sulphur batteries using macrocycle organic molecules.