Fe3C-inserted “tube plugging into porous network” nanohybrids as advanced sulfur hosts for lithium-sulfur batteries

Abstract

Commercial applications of lithium-sulfur batteries are hindered by the low electrical conductivity of sulfur cathodes, which can be overcome by the application of suitable sulfur host materials. In this work, a novel and effective method is developed to grow bamboo-like N-doped carbon nanotubes (NCNTs) across three-dimensional N-doped porous carbon network (NPCNs) via chemical vapor deposition, thereby successfully preparing the sulfur-loaded composite carbon material inserted into the porous network. In such structure, carbon nanotubes act as electronic conduction paths, carbon networks as mass transfer channels, as well as the inserted Fe3C nanoparticles can increase the polarity of the carbon matrix. The discharge capacity of the S-NCNT/NPCNs cathode, as high as 1125 mAh g−1 at 0.2 C, retains 43.5% of its value when the current is increased 10-fold to 2 C. A specific capacity of 548.1 mAh g−1 at 1 C remains almost unchanged after 300 cycles, demonstrating better charge and discharge performance and excellent cycling ability of these promising candidate materials for Li-S battery applications. More importantly, the synthesis strategy is universal and can be fully extended to prepare other units, even binary NCNT/NPCNs (for example, NCNT/NPCNs-Co, NCNT/NPCNs-Co-Fe, NCNT/NPCNs-Fe-Ni, and NCNT/NPCNs-Co-Ni). The new strategy provided here may open up new ways for the application of hybrid carbon nanostructures in energy storage systems.