Catalytic separators with Co–N–C nanoreactors for high-performance lithium–sulfur batteries

Rechargeable lithium–sulfur (Li–S) batteries are considered as one of the most promising next-generation energy storage devices because of their high theoretical energy density. However, the dissolution of lithium polysulfides (LiPSs) in an ether electrolyte and its sluggish reaction kinetics severely limit their practical performances. Herein, an atomically dispersed supported metal catalyst with a Co–N4 structure on active carbon (Co–N–C/AC) is prepared and introduced to modify the separators of Li–S batteries. The Co–N–C catalyst not only suppresses the shuttle effect of LiPSs through the physical barrier and chemical affinity but also improves the redox kinetics of the sulfur species. The first-principles calculation indicates that LiPSs on Co–N–C possess a high binding energy and low decomposition energy barrier in the electrochemical process, thus effectively accelerating the conversion of LiPSs during the charge/discharge process and improving sulfur utilization in Li–S batteries. Therefore, a Li–S battery based on a Co–N–C/AC modified separator can deliver admirable rate performance and stable cycling life with a reversible discharge capacity of over 865 mA h g−1 and a decay rate of 0.043% per cycle after 500 cycles at 1.0 C. This work provides new insights for developing a functional separator to accelerate the conversion kinetics of LiPSs for achieving high energy density Li–S batteries.