Facile Synthesis of a “Two-in-One” Sulfur Host Featuring Metallic-Cobalt-Embedded N-Doped Carbon Nanotubes for Efficient Lithium-Sulfur Batteries

The exploration of efficient host materials of sulfur is significant for the practical lithium-sulfur (Li-S) batteries, and the hosts are expected to be highly conductive for high sulfur utilization and exhibit strong interaction toward polysulfides to suppress the shuttle effect for long-lasting cycle stability. Herein, we propose a simple synthesis of metallic cobalt-embedded N-doping carbon nanotubes (Co@NCNT) as a "two-in-one" host of sulfur for efficient Li-S batteries. In the binary host, the N-doped CNTs, cooperating with metallic Co nanoparticles, can serve as 3D conductive networks for fast electron transportation, while the synergetic effect of metallic Co and doping N heteroatoms helps to chemically confine polysulfides, acting as active sites to accelerate electrochemical kinetics. With these advantages, the S/Co@NCNT composite delivers an excellent cycling stability with a capacity decay of 0.08% per cycle averaged within 500 cycles at a current density of 1 A g-1 and a high rate performance of 530 mA h g-1 at 5 A g-1. Further, the superior electrochemical performance of the S/Co@NCNT electrode can be maintained under a high sulfur loading up to 4 mg cm-2. Our work demonstrates a feasible strategy to design promising host materials simultaneously featuring high conductivity and strong confinement toward polysulfides for high-performance Li-S batteries.