Allyl tris(2,2,2-trifluoroethyl) carbonate (ATFEC) was synthesized as a bi-functional additive of flame retardant and film former in electrolytes for lithium ion batteries (LIBs). The flame retardancy of the additive was characterized with differential scanning calorimetry (DSC) and self-extinguishing time (SET). It is shown that adding 1vol.% ATFEC in 1M LiPF6/propylene carbonate (PC) can effectively enhance the thermal stability of the electrolyte and suppress the co-intercalation of PC into the graphitic anode. Further evaluation indicates that the additive hardly affect the conductivity of electrolyte. These support the feasibility of using ATFEC as an additive on formulating an electrolyte with multiple functions such as film-forming enhancement, high thermal stability and high ionic conductivity.