Electrospun carbon nanofibers loaded with sulfur vacancy CoS as separator coating to accelerate sulfur conversion in Lithium-Sulfur batteries.

Lithium-sulfur batteries (LSBs) have been sought after by researchers owing to their high energy density; however, the inevitable capacity decay and slow reaction kinetics have hindered their advancement. Here, we prepare a Prussian blue analog, Co[Co(CN)] and synthesize carbon nanofibers/S vacancy CoS (CNFs/CoS) as electrocatalysts for separator coating via electrospinning, carbonization, sulfurization, and hydrogen reduction. CNFs/CoS exhibits excellent electrocatalytic activity, wherein S vacancies induce the partial oxidation of Co to Co in CoS and CNFs provide long-range electron transport pathways. Various electrochemical tests, such as Tafel, ion diffusion coefficient, LiS precipitation, and LiS symmetric cells, further confirm the enhanced electrocatalytic activity. The LSBs with CNFs/CoS modified separator delivers an initial discharge capacity of 1056.7 mAh g at 0.2C, maintaining 840.8 mAh g after 100 cycles at 0.2C. When S loading is increased to 4.42 mg cm, the battery retains a discharge capacity of 687.9 mAh g (3.04 mAh cm) after 70 cycles at 0.1C. Our work can provide a reference for synthesizing anion-vacancy materials and designing anion-vacancy electrocatalytic composites for LSBs.