Aerosol-assisted synthesis of porous and hollow carbon-carbon nanotube composite microspheres as sulfur host materials for high-performance Li-S batteries

Spherical carbon materials with porous and hollow structures have been developed as efficient sulfur host materials for Li-S batteries through various synthetic strategies. However, nanostructured carbon materials, generally synthesized by liquid solution processes, have disadvantages of low electrical conductivity as sulfur host materials. In this study, highly porous hollow carbon-carbon nanotubes (CNTs) composite microspheres, with a high loading rate of ultrafine S and high electrical conductivity, are designed and successfully synthesized by an aerosol-assisted process (ultrasonic spray pyrolysis) as efficient sulfur host materials. The carbon-CNTs composite microspheres, with a high sulfur loading rate of 70 wt%, exhibit superior electrochemical performance as a cathode compared to that of S-loaded CNTs balls for Li-S batteries. The S-loaded carbon-CNTs composite microspheres exhibit a discharge capacity of 697 mA h g(-1 )for the 250th cycle at a current density of 1.0C and show high reversible discharge capacities of 685 mA h g(-1), even at a high current density of 3.0C. The outstanding cycling and rate performance of S-loaded carbon-CNTs composite microspheres are attributed to the structural flexibility of the hollow structure, loading of ultrafine sulfur in micro- and mesopores of dextrin-derived carbon, and good electrical conductivity due to uniformly dispersed CNTs.