A flame retardant separator modified by MOFs-derived hybrid for safe and efficient Li-S batteries

Abstract In this work, we have successfully prepared a novel separator modified with N, S co-doped carbon framework (named NSPCF) with confined CoS2 nanoparticles and rooted carbon nanotubes material (named NSPCF@CoS2) to apply for high-performance Lithium-Sulfur batteries (Li-S batteries). Robust carbon structure with large specific surface can act as a physical barrier and possess physical adsorption effect on lithium polysulfides (LiPSs). In addition, highly-conductive carbon can improve integral conductivity, leading to the fast charge transport and reaction kinetics. Also, doping heteroatoms could form more active sites to adsorb LiPSs strongly so that modified separator could inhibit the shuttle effect effectively. Moreover, the presence of CoS2 further enhances the ability of modified separator to trap LiPSs owing to the Lewis acid-base action. As a result, the NSPCF@CoS2@C-150 battery can deliver initial discharge capacities of 863.0, 776.2, 649.1 and 489.4 mAh g-1 at 0.1, 0.5, 1 and 2 C with a high sulfur loading of 2.04 mg cm-2, respectively. Notably, when turning the current density back to 0.1 C, its discharge capacity can recover to 1008.7 mAh g-1. In addition, the modified separators exhibit outstanding capacities to restrain the growth of lithium dendrites. It is noteworthy that the flame retardant performances of Li-S batteries are improved dramatically owing to the novel structures of modified separators. This rationally designed separator endows Li-S batteries with higher safety and excellent electrochemical performances, providing a feasible strategy for practical application of Li-S batteries.