Highly safe and cyclable Li-metal batteries with vinylethylene carbonate electrolyte

Safety concerns impede the deployment of Li-metal batteries, while the highly flammable electrolytes make main contribution to the hazard caused by the reactive Li with electrolytes. Fire-extinguishing electrolytes do exist, but their introductions into the batteries have generally resulted in cycle performance trade-offs. In this work, we report a new electrolyte that consists of 1 M lithium hexafluorophosphate dissolved in a single solvent of vinylethylene carbonate (VEC), enabling Li-metal batteries with the most reliability in terms of high safety, long cycle life and practical scale-up among the up-to-date strategies. Combining theoretical calculations with physical and electrochemical characterizations, we demonstrate that this new electrolyte is highly flameretardant, thanks to the strong combination of VEC with hydrogen and hydroxide radicals, and provides Li-metal anode with excellent cycle stability, attributed to easy desolvation of Li ions in VEC and unique interphase chemistry that consists of inorganic Li2CO3 underneath and organic -(CH2-CH2O)(2)- species on the top, originated from VEC reduction. Considering the low cost of VEC, this VEC-based electrolyte makes it possible for Li-metal batteries to be applied practically in large scale.