Enabling a non-flammable methyl(2,2,2-trifluoroethyl) carbonate electrolyte in NMC622-graphite Li-ion cells by electrode pre-passivation

Novel lithium-ion battery electrolytes often exhibit poor electrochemical stability against typical commercial layered oxide and graphite electrodes. Pre-passivating the electrodes prior to cell assembly with an electrically insulating, ionically conductive solid-electrolyte interphase (SEI) is one innovative strategy for stabilising systems with otherwise unusable electrolytes. Here, methyl(2,2,2-trifluoroethyl) carbonate (FEMC), a promising non-flammable electrolyte solvent that is generally unstable against graphite, is utilised after pre-passivation of electrodes with a state-of-the-art carbonate-based electrolyte. A significant improvement in performance is observed compared with the untreated electrodes. Hard X-ray photoelectron spectroscopy was used to probe the interphase layer composition.