Fluorinated electrolyte composition for an electrochemical cell having a lithium or lithium alloy anode

The invention relates to an electrochemical cell comprising: —at least one anode comprising metallic lithium or a lithium alloy or at least one anode comprising a current collector at least partially covered with metallic lithium deposited after at least one charge of the cell, the cell not containing metallic lithium at the time of its manufacture, —at least one cathode, —a liquid or gelled electrolyte composition comprising: a) a solvent comprising: i) either a mixture of 1,1,1,3,3,3-hexafluoro-2-methoxypropane (HFMP) and/or 1,1,1,3,3,3-hexafluoro-2-(fluoromethoxy)propane (HFMFP), ethylene monofluorocarbonate (F1EC) and 2,2,2-trifluoroethyl methyl carbonate (F3EMC), ii) or a mixture of 1,1,1,3,3,3-hexafluoro-2-methoxypropane (HFMP) and/or 1,1,1,3,3,3-hexafluo-ro-2-(fluoromethoxy)propane (HFMFP), ethylene monofluorocarbonate (F1EC) and 2,2,2-trifluoroethyl acetate (F3EA), b) at least one salt whose cation is the lithium cation, c) lithium difluorophosphate LiPOFin an amount representing from 0.05 to 5% of the mass of the combination made up of the solvent and said at least one dissolved lithium salt.