Effective Trapping of Polysulfides Using Functionalized Thin-Walled Porous Carbon Nanotubes as Sulfur Hosts for Lithium-Sulfur Batteries.

Abstract

Owing to their high aspect ratios and structures of high-mechanical-strength conductive scaffolds, carbon nanotubes (CNTs) are considered to be one of the most promising hosts for sulfur in lithium-sulfur batteries (LSBs). However, traditional CNTs with impermeable walls are not conducive to the penetration of sulfur, resulting in a large number of sulfur exposures to the electrolyte. Therefore, it is difficult to effectively limit the shuttle effect of polysulfides. Here, a kind of thin-walled porous amorphous carbon nanotube (HCNT) is adopted as the host for sulfur in LSBs. To further alleviate the shuttle effect, oxygen-containing functional groups (OCFGs) are introduced to modify HCNTs to form HOCNTs. The S/HOCNT composite with the embedded structure is successfully constructed. The S/HOCNT cathode demonstrates glorious cycling and rate performance (798.5 mAh g-1 at 0.2 C after 100 cycles and 511.6 mAh g-1 at 1 C after 500 cycles). The excellent electrochemical performance of S/HOCNT can be attributed to the embedded structure of sulfur in HOCNTs, which avoids direct contact with the electrolytes and strong bonding action of OCFGs and polysulfides, effectively limiting the shuttle effect of polysulfides.