Clarifying the Role of Ordered Mesoporous Carbon on a Separator for High-Performance Lithium-Sulfur Batteries

Despite the remarkably high theoretical energy density (∼2600 W h kg^-1), lithium-sulfur (Li-S) batteries are still far from commercialization due to the poor intrinsic electrical conductivity of sulfur and the polysulfide shuttle effect. In order to resolve these problems, various sulfur host materials and modified separators have been investigated. Herein, we investigate a dual-functional interlayer by applying ordered mesoporous carbon (OMC) on a commercial separator as (1) OMC provides sufficient capability for adsorbing dissolved polysulfide and (2) the OMC interlayer acts as an additional current collector (reaction site). An innovative investigation of the behaviors of adsorbed sulfur species in the OMC interlayer during cycling is conducted by operando small-angle X-ray scattering and energy-dispersive X-ray spectroscopy analysis. The Li-S cell with a particular configuration, which has only Ketjenblack (KB) without sulfur on the cathode and the OMC interlayer containing 70 wt % of sulfur on the separator, proves that the OMC interlayer provides an additional reaction site. The comprehensive analyses suggest that the dual-functionalized OMC interlayer exhibits great potential for fabricating high-performance Li-S batteries. In addition, the OMC interlayer results in improved electrochemical performances for a high-sulfur-loading cathode (90 wt % S/KB).