Abstract Developing nonflammable electrolyte with a wide electrochemical window has become an urgent demand for high‐energy‐density and high‐safe lithium‐ion batteries (LIBs). Herein, a fluorinated nonflammable phosphate electrolyte is developed to construct a safe 4.5 V‐class LIB (Si‐SiC‐C/0.35Li2MnO3·0.65LiNi0.5Mn0.5O2). The proposed fluorinated phosphate electrolyte, 0.8 M LiPF6/tris(2,2,2‐trifluoroethyl) phosphate (TFEP) + 5 vol% fluoroethylene carbonate (FEC) + 5 vol% vinylene carbonate (VC), is not only completely nonflammable but also exhibits excellent oxidative/reductive stability on 0.35Li2MnO3·0.65LiNi0.5Mn0.5O2 cathode and Si‐SiC‐C anode. The in situ differential electrochemical mass spectrometry and X‐ray photoelectron spectroscopy proved that TFEP‐based electrolyte does not decompose into gases but forms a high‐quality electrode‐electrolyte interface on cathode surface at high working potential. The 4.5 V‐class LIBs using 0.8 M LiPF6 TFEP‐based nonflammable electrolyte shed some light on potential application for high‐safe and low‐cost larger‐scale energy storage.
