N-doped carbon nanotubes and CoS@NC composites as a multifunctional separator modifier for advanced lithium-sulfur batteries.

Lithium-sulfur batteries (LSBs), with their high theoretical energy density and specific capacity, are considered optimal candidates for next-generation energy storage systems. However, significant challenges remain in their cycle life and efficiency for practical applications, primarily due to the shuttle effect of lithium polysulfides (LiPSs) and the poor electrical conductivity of sulfur materials. The key to addressing these challenges lies in designing materials with excellent dispersion, good electrical conductivity, and high catalytic activity. In this work, we have designed and successfully synthesized a unique structural material consisting of in-situ grown cobalt sulfide nanoparticles embedded in zeolite imidazolate frameworks (ZIFs), which are derived from N-doped carbon wrapped around polypyrrole-derived N-doped carbon nanotubes (CoS@NC/NCNT). This design effectively mitigates the shuttle effect of lithium polysulfides (LiPSs) and enhances the conductivity of the material. As a result, batteries with CoS@NC/NCNT-modified separators achieved a high specific discharge capacity of 1518 mAh g at 0.1 C. This work provides a reliable design strategy for synthesizing N-doped carbon nanotube/high-activity transition metal sulfide composite materials and opens new avenues for enhancing the modification and separation of high-performance lithium-sulfur batteries (LSBs).