Supramolecules Applied to Energy Storage Devices: Study on the Mechanism of Cucurbituril Inhibition of the Polysulfide Shuttle Effect

Abstract

Lithium-sulfur (Li-S) batteries are considered promising candidates for next-generation high-energy-density storage devices; however, their commercialization remains hindered by several challenges. Supramolecular macrocyclic compounds, owing to their unique structures and properties, hold significant potential for improving Li-S battery performance. In this study, the inclusion mechanism of lithium polysulfides (LiPSs) by cucurbiturils (CB[n], n = 6,7) was systematically investigated. Density functional theory (DFT) calculations were employed to analyze the recognition capabilities of CB[6] and CB[7] for polysulfides. The results indicate that both CB[6] and CB[7] effectively encapsulate polysulfides through non-covalent interactions. Specifically, CB[6] exhibits a stronger affinity for medium-chain sulfur species, with the most pronounced encapsulation observed for Li₂S₄. In contrast, CB[7] demonstrates superior encapsulation efficiency for longer-chain sulfur species, with the most stable inclusion occurring for Li₂S₆. Furthermore, molecular dynamics (MD) simulations based on DFT calculations revealed that Li₂S₄@CB[6] and Li₂S₆@CB[7] exhibit high stability in battery electrolytes. These findings suggest that CB[6] and CB[7], as supramolecular materials, can effectively inhibit the dissolution and migration of polysulfides in Li-S batteries, mitigating the “shuttle effect” and significantly enhancing battery cycle life and charge-discharge efficiency. This research provides valuable insights into the optimization of materials for Li-S battery applications.