Non-flammable, Low-cost and Fluorine-free Solvent for Liquid Electrolyte of Rechargeable Lithium Metal Batteries

Rechargeable metallic lithium batteries are considered as promising candidates for next-generation energy storage due to their high energy densities. However, safety concerns associated with electrolyte flammability and dendrite growth hinder their practical applications. Non-flammable liquid electrolytes have attracted significant attention recently, but they are mainly based on expensive ionic liquids, fluorinated solvents or with highly concentrated salt. Here we design a novel tri-salt electrolyte composed of lithium bis(trifluoromethanesulfonyl)imide (LiTFSI)-Lithium bis(oxalato)borate (LiBOB)-LiPF6 in EC/PC solvent, which is not flammable even in contact with fire. Moreover, it creates unique protection of solid electrolyte interphase (SEI) film on lithium metal anode that allows 400 cycles of Li/Li(NiMnCo)1/3O2 cells with a capacity retention of 97.0 % at 0.83 mA cm-2. This work illustrates that low-cost fluorine-free carbonate solvents can also realize non-flammable electrolyte with high performan...