Enhancing polysulfide confinement and conversion in meso-/microporous core-shelled MoC/NC microspheres for lithium-sulfur batteries

Porous carbon-based materials are employed as sulfur hosts to overcome the problems of insulating nature and volume expansion during lithiation of sulfur cathodes in lithium-sulfur (Li-S) batteries to some degree. However, the shuttle effect and sluggish redox reaction kinetics of sulfur species result in unsatisfactory cycle life and sulfur utilization, hampering the practical application of Li-S batteries. In this work, meso-/microporous core-shelled MoC nanocrystal-embedded N-doped carbon microspheres (MoC/NC CSMSs) were prepared and further used as sulfur hosts. The tailored mesoporous core and microporous-thin shell cooperate to guarantee a high sulfur loading, good electrolyte penetration, improved structural stability, and relieved shuttle effect. Besides, the uniformly distributed MoC nanocrystals enhance the affinity to lithium polysulfides (LiPSs) via the formation of the Mo-S bond and accelerate the conversion kinetics of LiPSs by catalyzing the formation and decomposition of Li2S clusters. After sulfur loading, the MoC/NC/S CSMS electrode exhibits remarkable lithium storage properties with a high reversible capacity of 1370.3 mA h g(-1) at 0.1C, outstanding rate performance, and ultra-long cycle life with a low capacity decay rate of 0.034% per cycle for 500 cycles at 1C.