Tailoring molecular structures for enhanced anchoring of polysulfides in lithium–sulfur batteries.

The functional 2-fluorobenzamide is introduced onto carboxylic multiwalled carbon nanotubes to craft sulfur hosting materials with precisely tailored functional interfaces for Li–S batteries. The semi-ionic C–F bonds and carbonyl functional groups present a synergistic strategy via Li···O and Li···F bonds for anchoring LiPSs, resulting in outstanding electrochemical performance of the sulfur cathode. [Display omitted] • The feasibility of cooperative trapping of lithium polysulfides is demonstrated by strategically designed organic molecules using density functional theory. • Based on theoretical guidance, a series of benzamide-based organic molecules with semi-ionic C-F bonds and carbonyl functional groups were grafted onto carbon nanotubes as sulfur host materials for Li–S batteries. • The semi-ionic C-F bonds and carbonyl functional groups in organic molecules present a synergistic strategy to anchor lithium polysulfides through Li···O and Li···F bonds, resulting in enhanced electrochemical performance. Lithium–sulfur (Li–S) batteries, with promising potential for high energy density, remain compelling candidates for next-generation energy storage systems. However, they still suffer from huge challenges such as severe shuttle effects and sluggish redox kinetics. A strategic approach involves the meticulous design of host materials at the molecular level, emphasizing the construction of efficient sulfiphilic organic molecules as anchoring sites for lithium polysulfides (LiPS). In this study, a series of benzamides (benzamide, 2-fluorobenzamide, and 2,6-difluorobenzamide) are introduced onto carboxylic multiwalled carbon nanotubes (C-CNT) to graft sulfur hosting materials with tailored functional interfaces for Li–S batteries. Through a comparative study, we identify the semi-ionic C−F bond and carbonyl functional group as active centers, presenting a synergistic strategy via Li···O and Li···F bonds for anchoring LiPS. The optimized cathode material of sulfur-based carbon nanotubes grafted with 2-fluorobenzamide exhibits outstanding electrochemical activity, achieving a high reversible capacity of 944.8 mAh/g under a high sulfur loading (5.5 mg cm−2) and low electrolyte usage (8 µL mg−1). Our study underscores the potential of tailoring the molecular structure of host materials to effectively immobilize LiPS for high-performance Li–S batteries. [ABSTRACT FROM AUTHOR]