Cos-Nc@Cnts Hierarchical Nanostructures for Efficient Polysulfide Regulation in Lithium-Sulfur Batteries

Because of high theoretical energy density, natural abundance of sulfur and low cost, lithium-sulfur (Li-S) batteries have been paid extensive attention in electrochemical energy storage. However, Li-S batteries exhibit rapid capacity decay and lousy rate performance due to polysulfides (LiPSs) shuttle and sluggish redox kinetics. Therefore, it is crucial to take measures to anchor LiPSs and catalyze their conversion in order to improve the performance of Li-S batteries. In this work, ZIF-67-derived carbon polyhedra decorated with ultrafine CoS nanoparticles are interconnected by carbon nanotubes (CNTs). The uniformly distributed CoS nanoparticles can enhance redox kinetics by immobilizing LiPSs and catalyzing their conversion of solid-to-liquid-to-solid reactions. Furthermore, the three-dimensional conductive network consisting of ZIF-67-derived carbon polyhedra and CNTs facilitates fast electron transport and thus leads to excellent rate and cycling performance. The cells assembled with CoS-NC@CNTs-pp show a high initial discharge capacity of 1408.5 mAh g at 0.1 C and 1186.7 mAh g at 1 C with outstanding cycling stability over 500 cycles. Even at the large current density of 5 C, it still can provide a high discharge capacity of 832.6 mAh g. This work provides an efficient route to accelerate redox conversion and suppress the shuttle effect by designing a multifunctional separator.