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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 Li 2 CO 3 underneath and organic –(CH 2 –CH 2 O) 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. VEC-based electrolyte enables Li-metal batteries more reliable than state-of-the-art approaches in terms of safety, cyclic stability and rate capacity. Image 1 • Highly safe and cyclabe Li-metal batteries are accomplished with a novel LiPF 6 /VEC electrolyte. • VEC is highly flame-retardant due to its strong combination of VEC with H⋅ and OH⋅ radicals, ensuring the highly safe batteries. • A unique interphase of underneath inorganic Li 2 CO 3 and top organic –(CH 2 –CH 2 O) 2 - species is established by VEC reduction. • High cyclability of the batteries is ensured with then unique interphase chemistry and the easy desolvation of Li ions in VEC. [ABSTRACT FROM AUTHOR]