High stability of solid electrolyte interphase in lithium metal batteries enabled by direct fluorination on metal iron powder

[Display omitted] •Fluorinated Fe powders resulted in a significant increase in the wettability of molten Li.•The Fe-F layer was grown on the surface of the Fe powder was lipophilic and showed good wettability.•Fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after a cycle test at 0.1 and 0.2 mA cm−2.•This proposed method will further develop rechargeable lithium-metal battery technology. Multiple studies attempted mixing Li with microparticle metal powders or using it to impregnate a porous media to utilize for thermal batteries. The infusion of Li into porous structures or powders is challenging as most materials used in battery fabrication are lithiophobic to molten Li. Optimizing and improving the wettability of molten Li is one approach to address this. Herein, we propose an efficient and facile direct fluorination method for achieving an ultra-lithiophilic fluoride layer on the surface of a Fe powder. Fluorination of Fe powders resulted in a significant increase in the wettability of molten Li by growing a Fe-F layer on the surface of the Fe powder. This layer was lithiophilic and showed good wettability. An anode prepared using fluorinated Fe-Li metal showed no evidence of short circuits or dendrite formation after a cycle test at 0.2 mA cm−2. Both a pure Li anode and pristine Fe powder showed unstable charge–discharge characteristics when used as an anode in cycle tests. This proposed method will further develop rechargeable lithium-metal battery technology.