Graphitic Mesoporous Carbon/Mn₇C₃ as Polysulfide Host for High Rate Li-S Batteries

Abstract

Li-S batteries are one of the most promising next-generation energy storage systems due to their high theoretical energy density (∼2500 Wh/kg). However, the rate capability of Li-S batteries is still unsatisfactory because of the insulating nature of S and Li2S2/Li2S. Here, we report highly graphitized mesoporous carbon/Mn7C3 (GMC/Mn7C3) nanospheres for high-rate lithium-sulfur batteries. Manganese oxides are first introduced into the mesoporous carbon precursor, which promotes the formation of highly graphitized porous carbon during the following carbonization process. The content of Mn7C3 is optimized, so highly conductive graphitic carbon host and mesoporous morphology are simultaneously achieved and beneficial for high-rate transfers of both electrons and Li ions. The resulting S/GMC/Mn7C3 cathode can be charged/discharged up to 10-C rate, yielding a 50% capacity retention ratio comparing to that at 0.5 C. This work suggests a possible approach for future development of high-rate Li-S batteries.