Abstract
This chapter introduces the role of fluorinated and nonfluorinated additives introduced in Li-ion batteries electrolytes. These additives are mostly designed to create an artificial solid electrolyte interphase (SEI) at the anode material surface during the first charge. The physicochemical properties of the SEI are critical for the performances and cycling abilities of the cell and any break in its surface must be self-repairable. Some examples will be given using graphite and TiSnSb as active materials and vinylene carbonate, fluoroethylene carbonate (FEC), and difluoroethylene carbonate as additives to a mixture of alkyl carbonates containing LiPF6 as the lithium salt. The ionic resistance, the cycling ability, and the composition of the SEI film will be examined as a function of the additives added to the electrolyte solution. From X-ray photoelectron spectroscopy and electrochemical impedance spectroscopy results, the role of fluorinated additives like FEC as effective SEI improvers in alkyl-carbonate-based electrolyte has been enlightened.