Competing polysulfides conversion between edge-N and embedded CoS2 within multichannel carbon nanofibers

The practical application of lithium-sulfur batteries (LSBs) is hindered by a range of challenges, including slow conversion kinetics and inevitable shuttle effect of lithium polysulfide (LiPSs) intermediates, low electrical conductivity and rigorous volume expansion of sulfur. To address these challenges, we initiatively propose a competing catalytic mechanism dominated by two functional components, which aims to accelerate the liquid–liquid–solid conversion for the sulfur reduction reaction (SRR). To achieve this goal, we construct multichannel carbon fibers decorated with edge nitrogen and CoS2 nanoparticles (CoS2/NMCNF) as the cathode host for LSBs. The internal channels provide spatial constraints towards alleviating volume expansion and accelerating electron/ion transmission. Moreover, based on theoretical calculations and experiments, there is a competition between edge nitrogen and embedded CoS2 for catalytic conversion of LiPSs, of which CoS2 plays a major role in the liquid–liquid conversion (Li2S6–Li2S4), while edge-N accelerates the liquid–solid conversion (Li2S4–Li2S2). Consequently, the prepared CoS2/NMCNF electrode has an excellent performance with high initial specific capacity (1,437.9 mAh/g at 0.2C), excellent cycling stability at 3.0C (only about 0.032% capacity decay per cycle after 650cycles), and maintaining good cycling stability even when the sulfur loading increases to 4.10 mg cm−2. This work demonstrates a unique competing catalytic mechanism for the liquid–liquid–solid conversion process of LSBs.