Quantitative investigation of polysulfide adsorption capability of candidate materials for Li-S batteries

Lithium-sulfur batteries have a high theoretical energy density of 2500 Wh/kg and are promising candidates for meeting future energy storage demands. However, dissolution of the intermediate polysulfide species into the electrolyte remains as a major challenge, causing fast capacity degradation in Li-S batteries. Many recent studies have reported various materials such as metal oxides and sulfides that interact strongly with polysulfide species and can alleviate the dissolution problem, though little work has focused on quantitative comparison of different materials under equivalent conditions. Here, we establish a standard procedure to quantitatively compare the polysulfide adsorption capability of candidate materials. We found that an order of magnitude of difference is evident between poor adsorption materials such as carbon black and strong adsorption materials such as V₂O₅ and MnO₂. We elucidate different adsorption mechanisms may be present and probe possible adsorption species. We expect our work will provide a useful strategy to screen for suitable candidate materials and valuable information for rational design of long cycle life Li-S batteries.