Ionic-Liquid-Assisted Synthesis of N, F, and B Co-Doped CoFe2O4-x on Multiwalled Carbon Nanotubes with Enriched Oxygen Vacancies for Li-S Batteries

The "shuttle effect," sluggish redox kinetics, and short life cycle have seriously restricted the practical application of Li-S batteries. Herein, N, F, and B co-doped NFBCoFe2O4-x on multiwalled carbon nanotubes' (MWCNTs) (NFBCoFe2O4-x@MWCNTs) composite material with enriched oxygen vacancies (OVs) introduced by ionic liquids (ILs) does not only exhibit enhanced polysulfides trapping ability but also effectively accelerate the redox kinetics of polysulfides. A commercial Celgard polypropylene (PP) 2400 separator with NFBCoFe2O4-x@MWCNTs coating layer is fabricated as a multifunctional barrier for Li-S batteries. As a result, the battery based on the NFBCoFe2O4-x@MWCNTs separator demonstrates a stable electrochemical performance. Even under a high S loading of 8.0 mg cm(-2), a desirable areal capacity of 4.62 mAh cm(-2) can still be maintained over 200 cycles at a current density of 0.2 C. The prospective strategy of engineering OVs introduced by ILs provides novel insights into the development of Li-S batteries.