Encapsulating Co9S8 nanocrystals into CNT-reinforced N-doped carbon nanofibers as a chainmail-like electrocatalyst for advanced Li-S batteries with high sulfur loading

Li-S batteries have been regarded as one promising candidate for next-generation energy storage systems, however, their practical implementations are severely hindered by the intractable polysulfides shuttle (PSS) effect and retarded conversion kinetics. Herein, a flexible electrode consisting of Co9S8 nanocrystals and CNTs encapsulated inside porous N-doped carbon nanofibers (NCF) (CNT@NC/Co9S8) was developed by electrospinning followed by in-situ sulfurization. The carbon nanofibers and embedded CNTs build a highly conductive network, while the Co9S8 and N dopant provide more polar sites for LiPSs confinement. This self-supported flexible electrode with a sulfur loading of 12.5 mg cm(-2) exhibits a high initial discharge capacity (1207.7 mAh g(-1) at 0.1C), excellent rate capability (831.2 mAh g(-1) at 4.0C) and cycling stability (765.5 mAh g(-1) with a capacity retention of 78.1% after 1000 cycles at 2.0C). Moreover, when the sulfur loading increases to 20 and 30 mg cm(-2), high capacities of 869.2 and 706.6 mAh g(-1) can still be obtained at 0.1C after 100 cycles, respectively. Theoretical analysis suggests that the sulfur cathode built on CNT@NC/Co9S8 is electrocatalytically active towards LiPSs redox with enhanced conversion dynamics, thus mitigating the detrimental PSS effect.

Automated summary

A new flexible electrode for Li-S batteries has been developed in this study, which can enhance the conversion efficiency of the sulfur electrochemical reaction and alleviate the polysulfides shuttle effect. The experimental results demonstrate that this electrode exhibits high initial discharge capacity, excellent rate capability, and good cycling stability.