Unveiling the Role of Hydroxyl Architecture on Polysulfide Trapping for High-Performance Lithium–Sulfur Batteries

The rapid loss of active sulfur, because of a notorious effect of polysulfide shuttle, leads to a severe capacity fading in lithium–sulfur (Li–S) batteries. Although oxygen doping in cathodic materials is a promising strategy to enhance bonding interactions with lithium polysulfides, the origin of strong interactions remains to be poorly understood, because of a lack of consideration for the spatial arrangement of oxygen atoms affecting the overall performances. Here, we unveil the role of hydroxyl architecture on polysulfide trapping by systematically studying a series of cyclodextrin molecules that serve as a model platform, because of their well-defined structural uniqueness featuring abundant hydroxyl binding sites. We compare their trapping behaviors toward lithium polysulfides and thus correlate performance variations with their structural differences. Experimental findings coupled with computational modeling suggest that the asymmetrical arrangement of primary hydroxyl groups in β-CD determines the highest binding energies, relevant to the optimal capability in constraining polysulfide shuttle, and, in turn, contributes to remarkable improvements in the rate capacity and cycling performance. The identification of the role of hydroxyl architecture provides an atomic-scale explanation for the interaction between OH-group ordered interface and lithium polysulfides, and a new insight for the future design and engineering of interfaces in Li–S batteries.