A Multi-Functional Interface Derived from Thiol-Modified Mesoporous Carbon in Lithium-Sulfur Batteries
Lithium-sulfur (Li-S) batteries hold great promise as a next-generation energy-storage technology. Their practical application, however, is hindered by the rapid capacity fade associated with the dissolution of lithium polysulfides (LiPSs) into the organic electrolytes. In this work, we successfully impede these losses by anchoring thiol (-SH) functional groups to the nonpolar surface of a mesoporous carbon host. This new strategy increases the surface polarity of the conductive carbons and traps LiPSs inside the cathodes. By utilizing various spectroscopic methods, we investigate the mechanisms of LiPSs trapping, which originate from the electrostatic and covalent interactions of the thiol functional groups with Li+ from the electrolytes and with S from the LiPS chains, respectively. Here, we for the first time identify the multiple interactions that are induced by a small molecular interface upon cycling and correlate them with the electrochemical behavior. The fundamental insight on the thiol functionality suggests a further rational design of multi-functional interfaces to achieve better Li-S performance.