Co-Impregnated N-Doped Carbon Nanotube/SiO₂-Modified Separators as Efficient Polysulfide Barriers for Lithium–Sulfur Batteries

Abstract

The shuttling effect of polysulfide and its sluggish reaction kinetics are the primary issues with lithium–sulfur (Li–S) batteries. In this work, an improved coimpregnation technique was used to add cobalt atoms to nitrogen-doped carbon nanotubes (Co-NCNTs) and compound them onto mesoporous silicon (SiO2). Co-NCNTs/SiO2 composites were then used as modification materials for Li–S battery separators, which were capable of physical and chemical adsorption of lithium polysulfide (LiPSs). Between silica and LiPSs, there is chemical as well as physical adsorption in the mesoporous structure of the mesoporous silica. Cobalt has a significant capacity for adsorbing LiPSs, and the cobalt site possesses catalytic activity that can promote the redox kinetics of LiPSs. NCNTs have better electrical conductivity and a dense network structure, which facilitates electrolyte penetration and Li+ transfer. As a result, Li–S batteries built with a modified separator made of Co-NCNTs/SiO2 exhibit good capacity, cycle performance, and multiplier performance, with a 1314 mA h g–1 initial capacity at 0.2 C. After 200 cycles at 1 C, the capacity is 448 mA h g–1. This work proved that Co-NCNTs/SiO2 can efficiently adsorb LiPSs and accelerate their transformation, which slows down polysulfides' shuttle effect and speeds up their slow kinetics.