The safety issue challenges the application of lithium ion batteries. To solve this problem, organophosphous additives are applied to construct a non-inflammable electrolyte. Herein an enhanced performance is obtained with tris(2,2,2-trifluoroethyl)phosphite (TFFP) additive for pouch lithium ion batteries. With comparable electrochemical performance, cells with optimized electrolyte come to thermal runaway at higher temperature, which indicates more stable thermal stability. On the other hand, cells with optimized electrolyte exhibit low self-discharge performance. XPS results confirm a better SEI layer, which contributes to the enhancements of the thermal stability and self-discharge. All these results show that TTFP will bring better safety performance and will be a strong candidate for applicable electrolyte.