Vanadium Monoxide-Based Free-Standing Nanofiber Hosts for High-Loading Lithium-Sulfur Batteries

We report the fabrication of free-standing vanadium monoxide-based carbon nanofiber/sulfur (VO-CNFs/S) cathodes via electrospinning and in situ carbothermal reduction reaction followed by sulfur impregnation using an ultrarapid (<90 s) hybrid solution/melt deposition technique. The assembled Li-S batteries using VO-CNFs/S cathodes delivered a stable capacity of 950 mAh.g(-1) with 97% retention after 200 cycles at a 0.5 C rate with a moderate electrolyte/sulfur ratio of 20 mL.g(-1) of sulfur. Additionally, we develop cathodes with a high sulfur loading of 8.32 mg.cm(-2) that exhibits a stable capacity of 900 mAh.g(-1) after a few cycles with near 100% retention over 100 cycles. These cells correspond to a stable aerial capacity of 7.5 mAh.cm(-2). We integrate our fabrication and electrochemical performance study with fundamental investigations of Li+ diffusion kinetics, in situ visual monitoring of polysulfides, and ex situ post-mortem X-ray photoelectron spectroscopy study to elucidate polysulfide shuttling and polysulfide-host interactions. The unique integration of oxide and nitride groups in this work results in a synergistic effect of strong Lewis acid-base interactions originating from the vacant d-orbitals of the vanadium monoxide phase and improved conductivity originating from the nitrogen doping in CNFs from a polymeric precursor, thus offering active sites for strong polysulfide binding as well as faster reaction kinetics.

Automated summary

This study reports the fabrication of free-standing vanadium monoxide-based carbon nanofiber/sulfur (VO-CNFs/S) cathodes using electrospinning and in situ carbothermal reduction reaction followed by sulfur impregnation. The Li-S batteries assembled with these cathodes showed stable capacity retention over multiple cycles at different sulfur loadings, with enhanced conductivity and polysulfide binding sites resulting from the unique integration of oxide and nitride groups.