Single-Step Fabrication of Iron Single-Walled Carbon Nanotube Film from Ferrocene as a Conductive-Electrocatalyst Interlayer in Lithium–Sulfur Batteries

Floating catalyst chemical vapor deposition (FCCVD) is a continuous and scalable method for manufacturing conductive single-walled carbon nanotube (SWCNT) thin films. Hydrocarbons or hydrocarbon derivatives have been conventionally used as carbon sources and ferrocene as a Fe nanoparticle (NP) precursor in FCCVD for the fabrication of SWCNT thin films. However, carbon, released from ferrocene decomposition, has not been well investigated for the fabrication of SWCNT thin films. Here, we have developed an FCCVD process for the fabrication of SWCNT thin films using ferrocene as a single source for the generation of catalyst NPs and carbon. Moreover, the absence of hydrocarbons and their derivatives makes the process safe, cost-effective, and environmentally friendly. We fabricated freestanding Fe-SWCNT thin films composed of small diameter nanotubes (1.2 nm) and Fe NPs, synthesized at a high yield of 0.46 mg per 30 min. Fe-SWCNT thin films exhibited good conductivity with a sheet resistance of 800 ohm/sq for 80% transmission at 550 nm. Conductive SWCNTs significantly improved sulfur utilization, with an obvious 27% increase in the capacity of lithium–sulfur batteries (LiSBs). A HNO3-treated Fe-SWCNT separator significantly improved the cyclic stability of LiSBs with 18% capacity loss of initial capacity compared to 32% capacity loss for polypropylene separator after 100 cycles.