Co-Impregnated N‑Doped\nCarbon Nanotube/SiO₂‑Modified Separators as Efficient\nPolysulfide Barriers\nfor Lithium–Sulfur Batteries

Abstract

The shuttling effect of polysulfide and its sluggish\nreaction kinetics\nare the primary issues with lithium–sulfur (Li–S) batteries.\nIn this work, an improved coimpregnation technique was used to add\ncobalt atoms to nitrogen-doped carbon nanotubes (Co-NCNTs) and compound\nthem onto mesoporous silicon (SiO₂). Co-NCNTs/SiO₂ composites were then used as modification materials for Li–S\nbattery separators, which were capable of physical and chemical adsorption\nof lithium polysulfide (LiPSs). Between silica and LiPSs, there is\nchemical as well as physical adsorption in the mesoporous structure\nof the mesoporous silica. Cobalt has a significant capacity for adsorbing\nLiPSs, and the cobalt site possesses catalytic activity that can promote\nthe redox kinetics of LiPSs. NCNTs have better electrical conductivity\nand a dense network structure, which facilitates electrolyte penetration\nand Li⁺ transfer. As a result, Li–S batteries built\nwith a modified separator made of Co-NCNTs/SiO₂ exhibit\ngood capacity, cycle performance, and multiplier performance, with\na 1314 mA h g^–1 initial capacity at 0.2 C. After\n200 cycles at 1 C, the capacity is 448 mA h g^–1.\nThis work proved that Co-NCNTs/SiO₂ can efficiently adsorb\nLiPSs and accelerate their transformation, which slows down polysulfides’\nshuttle effect and speeds up their slow kinetics.