MOF-derived nanoporous carbon with embedded cobalt nanoparticles as interlayer for high-performance Li–S batteries

Lithium–sulfur (Li–S) battery is one of the promising energy storage systems due to its high theoretical energy density with low cost. The main challenge at present for its commercialization is the polysulfides shuttling, leading to poor cycling performance. Here, we report a facilely prepared metal-organic framework (MOF)-derived nanoporous carbon with embedded cobalt nanoparticles (NPCo/C) for alleviating the polysulfides shuttling. The NPCo/C with large surface area and abundant Co nanoparticles is simply prepared by direct carbonization of a Co-based MOF material, which is combined with graphene to construct a robust membrane as the interlayer (NPCo/C@G) to modify the pristine separator. The NPCo/C@G-modified separator gives the battery good cycling stability (707 mAh g−1 after 300 cycles at 0.5 C) and rate performance (capacity decay rate of 0.18% in 300 cycles at 2 C). Excellent battery performance (620 mAh g−1 after 100 cycles at 0.5 C) is exhibited even under ultra-low loading of NPCo/C@G (0.08 mg cm−2). The superior electrochemical performance is mainly attributed to abundant exposed Co active sites in NPCo/C to immobilize polysulfides and accelerate sulfur redox kinetics as well as excellent electrical conductivity of NPCo/C@G for improved sulfur utilization. This study provides a guidance for designing functional separators for Li–S battery application in the near future.