Fluorinated carbonate-based electrolyte for high-voltage Li(Ni _0.5Mn _0.3Co _0.2)O ₂/Graphite Lithium-Ion battery

A stable electrolyte system at a charge voltage over 4.5 V is the key to successfully obtaining higher energy density by raising the charging cutoff voltage. We demonstrate a fluorinated electrolyte (1 M LiPF₆ fluoroethylene carbonate (FEC) and methyl (2,2,2-Trifluoroethyl) carbonate (FEMC) (FEC/FEMC = 1/9, v/v)) for a high-voltage LiNi _0.5Mn _0.3Co _0.2O₂/graphite system. The stability of the fluorinated electrolyte for the LiNi _0.5Mn_0.3Co_0.2O ₂(NMC532) cathode was investigated using scanning electron microscopy, X-ray photoelectron spectroscopy, and electrochemical impedance spectroscopy. The charge-discharge performance of the fluorinated electrolyte was superior to the corresponding non-fluorinated electrolyte system at a charging cutoff voltage of 4.7 V.