Synergistic inhibitory effect of ultralight CNTs-COOH@Fe3O4 modified separator on polysulfides shuttling for high-performance lithium-sulfur batteries

Lithium-sulfur (Li-S) battery has attracted widespread research interest owing to its broad application prospects in high-density energy storage. However, the notorious "shuttle effect" is still the biggest obstacle to its practical application. In this work, the synergistic inhibitory effect on polysulfides shuttling has proposed by introducing a coating of ultrasmall Fe3O4 nanoparticles modified carboxylated carbon nanotubes (CNTs-COOH@Fe3O4) on a commercial separator. The carboxylated carbon nanotube networks can act as both physical barrier and ion shielding layer, preventing the migration of polysulfides. Meanwhile, the ultrasmall Fe3O4 nanoparticles can act as polysulfide-trapping centers to anchor polysulfides via robust chemical adsorption. In addition, the highly conductive CNTs-COOH@Fe3O4 coating can act as "upper current collector", promoting the kinetic conversion reaction of sulfur species and facilitating the reutilization of active materials. The synergistic effect of the ultralight separator coating (areal weight 1.79 g m(-2)) enables the Li-S batteries showing outstanding cycle stability (the capacity decay is as low as 0.032% per cycle at 1 C over 2000 cycles), excellent rate performance and superior anti-self-discharge capability. The proposed combination strategy paves the way to the simple and scalable preparation of advanced separators.