Rational design of well-dispersed ultrafine CoS2 nanocrystals in micro–mesoporous carbon spheres with a synergistic effect for high-performance lithium–sulfur batteries

The physical confinement and chemical catalysis of lithium polysulfides (LiPSs) are effective approaches to improve the performance of lithium–sulfur (Li–S) batteries. How to effectively combine physical confinement and chemical catalysis has become the focus of research. Herein, micro–mesoporous carbon (MMC) embedded with well-dispersed ultrafine CoS2 (uCoS2) nanocrystals as an efficient sulfur host is presented. As expected, the obtained S/uCoS2@MMC cathode can achieve a synergistic effect of physical confinement and chemical catalysis of LiPSs through micro–mesoporous structures and well-dispersed uCoS2 nanocrystals. Furthermore, the MMC with a high conductive specific surface area, uniform pore size and micro–mesoporous structure can realize homogeneous loading of sulfur and physical adsorption of LiPSs. Owing to these excellent qualities, the S/uCoS2@MMC cathode delivers outstanding initial capacities up to 1227 mA h g−1 at 0.1C. More significantly, a capacity of 606 mA h g−1 is maintained after 1000 cycles at 1C (a very low capacity decay rate of only 0.032% per cycle). It can be seen that the MMC embedded with well-dispersed uCoS2 nanocrystals as the sulfur host has great application prospects in Li–S batteries.