Longitudinal opening and Fe3C modifying of carbon nanotubes applied for high-performance lithium-sulfur batteries

Abstract

Carbon nanotubes (CNTs) have shown great potential as host materials for sulfur in lithium‑sulfur batteries. However, during the melting-diffusion process, liquid sulfur faces difficulties in penetrating deeply into the inner cavities of CNTs, particularly those with a large length-diameter ratio, which results in a limited number of attachment sites for sulfur. Additionally, the weak physical adsorption nature of carbon and the shuttling effect of soluble lithium polysulfides have been intractable issues. In this paper, we report the use of the high-frequency induction method to longitudinally open multiwalled CNTs derived from polypyrrole nanotubes, resulting in single-edge slotted carbon nanotubes (SCNT). These SCNTs significantly enhance the filling ratio of molten sulfur within the CNTs. Furthermore, Fe3C nanoparticles are introduced to enhance the chemisorption capacity of SCNT, thus alleviating the shuttle effect and improving the cycling stability of lithium‑sulfur batteries. As a result, the SCNT@Fe3C-S electrodes exhibit an initial capacity of 968 mAh g−1 and a stable cycling performance with a negligible capacity fading of 0.043 % per cycle over 1000 cycles at 1.0C with a sulfur loading of 3.0 mg cm−2. Overall, this work offers a new strategy for synthesizing high-performance sulfur hosts based on CNTs by cutting and modifying them.