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 flame-retardant, 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.