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

Abstract

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.