Effective chemisorption of polysulfides through organic molecules for high-performance lithium–sulfur batteries

Abstract

Lithium–sulfur (Li–S) batteries with high theoretical energy density have been regarded as promising energy storage devices. However, the sluggish redox kinetics and shuttle effect of lithium polysulfides of sulfur cathodes remain obstacles to their development, especially with high sulfur content. Herein, we introduce the organic molecule of 3-amino-1,2,4-triazole (AT) on graphene (G) through π–π interactions as a sulfur host material to address the shuttle effect of lithium polysulfides. The molecular fragment of = N–CN– in AT as the active site can effectively anchor polysulfides existing as neutral molecules and free radicals in the electrolyte via “Li···N” interaction. Combined with the fast electron transport facilitated by the graphene, the redox kinetics of polysulfides is promoted. Thus, the electrochemical performance of Li–S batteries can be remarkably improved. The S/G-AT electrode displays excellent electrochemical performance in terms of a high initial capacity (1411 mAh/g at 0.2C), long-term cycling stability (799 mAh/g after 450 cycles at 1C), and superior rate performance (817 mAh/g at 10C). This study helps to utilize functional organic molecules for fabricating high-performance cathode materials for Li–S batteries.