Hollow C/Co9S8 hybrid polyhedra-modified carbon nanofibers as sulfur hosts for promising Li-S batteries

Lithium-sulfur (Li-S) batteries hold great expectations as next-generation advanced capacity storage devices due to their higher theoretical energy density and low cost. Even so, polysulfide shuttles, insulation, and volume expansion of sulfur impede its commercial progress. To suppress these problems, we used electrospinning and self-templating to construct C/Co9S8 hybrid polyhedra-modified carbon nanofibers (denoted as C/Co9S8-C@S fibers) as sulfur hosts. The quasi-metallic polar Co9S8 strongly bonds and locks polysulfides, and the hollow polyhedra provide sulfur storage space. Moreover, the overall nanofiber forms an interconnected conductive network to assist the transmission of Li+/e- and restrain the escape of the sulfur phase to a certain extent. Compared with C/Co9S8 polyhedra and carbon nanofibers, the C/Co9S8-C@S fiber delivers excellent adsorption characteristics for polysulfides. As a Li-S battery cathode, the C/Co9S8-C@S fiber (sulfur content: 87.20 wt%) exhibits an initial specific capacity of 1013.7 mAh g-1 at 0.1 C, displaying a stable capacity of 694.9 mAh g-1 after 150 cycles. Additionally, it shows a high specific capacity of 894.7 mAh g-1 at 1C with a capacity decay of -0.116% per cycle over 500 cycles.

Automated summary

The use of C/Co9S8-C@S fiber as a sulfur host in Li-S batteries shows excellent adsorption characteristics for polysulfides and stable cycling performance.