Polar Co9S8 anchored on Pyrrole-Modified graphene with in situ growth of CNTs as multifunctional Self-Supporting medium for efficient Lithium-Sulfur batteries

Lithium-sulfur batteries (LSBs) have stimulated burgeoning interest in both the academic and industrial communities due to their ultrahigh energy density and high cost-effectiveness. However, the real-world application of LSBs has long been plagued by the shuttling effect and sluggish conversion kinetics of soluble lithium polysulfides (LiPSn). Herein, we have designed and synthesized creative metallic and polar Co9S8 nanoparticles with in situ growth of CNTs anchored on pyrrole-modified graphene (Co9S8/CNTs-Gr) via a facile pyrolysis method, which further demonstrates superior electrochemical performance for the fixation of sulfur and effective activation of LiPSn redox conversion. The in situ growth of CNTs and introduction of pyrrole-modified graphene are beneficial for electron migration, thus significantly boost the rate performance of LSBs. Concurrently, the Co9S8 electrocatalyst shows high catalytic activity to reinforce the polysulfide conversion. Benefiting from this exquisite nanoarchitecture design, LSBs with a S@Co9S8/CNTs-Gr cathode exhibit outstanding performance, delivering a high reversible specific capacity of 950 mA h g(-1) at 1C with a decay rate of only 0.01 % per cycle. Moreover, the S@Co9S8/CNTs-Gr electrode still achieves good cycling stability with a high sulfur loading of 7.2 mg cm(-2), and the specific area capacity reaches as high as similar to 6 mA h cm(-2). This work provides a delicate design to construct Co9S8-based media for high-performance LSBs and can also promote one's understanding of the advantages of the process of adsorption and redox conversion of LiPSn.

Automated summary

Lithium-sulfur batteries (LSBs) are attracting significant interest due to their high energy density and cost-effectiveness. However, the practical application of LSBs has been hindered by the presence of soluble lithium polysulfides (LiPSn) and slow conversion kinetics. In this study, Co9S8 nanoparticles with carbon nanotubes (CNTs) and pyrrole-modified graphene (Co9S8/CNTs-Gr) were synthesized, which exhibited superior electrochemical performance for sulfur fixation and LiPSn conversion. The nanoarchitecture design of Co9S8/CNTs-Gr resulted in enhanced rate performance and high catalytic activity for polysulfide conversion. The S@Co9S8/CNTs-Gr cathode showed outstanding performance, with high reversible specific capacity and good cycling stability. This work provides a delicate design for high-performance LSBs and enhances understanding of LiPSn adsorption and redox conversion.