Ordered micro-mesoporous carbon spheres embedded with well-dispersed ultrafine Fe3C nanocrystals as cathode material for high-performance lithium-sulfur batteries

For the development of lithium-sulfur (Li-S) batteries, it is important to construct advanced host materials with large conductive, specific surface area and high activity exposed polar sites for adsorption of lithium polysulfides (LiPSs), which could promote uniform nucleation of lithium sulfide (Li2S) and liquid/solid conversion efficiency of sulfur species. Herein, we first reported the synthesis of ordered micro-mesoporous carbon (OMMC) nanospheres embedded with ultrafine iron carbide (Fe3C) nanocrystals by a facile one-step carbonizing process as effective sulfur host materials. As expected, the Fe3C/OMMC nanospheres (Fe3C/OMMC NSs) can realize homogeneous loading of sulfur, strong adsorption and catalysis of LiPSs with high efficiency, and promote uniform nucleation of Li2S through the ordered micro-mesoporous structures and ultrafine (average 5 nm) Fe3C nanocrystals. The Fe3C/OMMC-S NSs cathodes achieved excellent sulfur utilization, outstanding cyclic stability (700 mAh g−1 at 1.0 C after 1000 cycles with an ultralow capacity decay of 0.033% per cycle) and impressive rate performance (656 mAh g−1 at 5.0 C).