In this work, a flame retardant co-solvent tris(2,2,2-trifluoroethyl) phosphite (TTFP) is applied to improve the flame retardancy of the battery, meanwhile it is able to improve the battery’s discharging capacities at both 4.2 V and high cut-off voltage (4.5 V). Specifically, at common voltage of 4.2 V, the cells’ 100th discharge capacity without TTFP is 130 mAh/g by 0.2 C with capacity retention (CR) 69%; in comparison at the same condition, the capacity of the 10 TTFP-contained cell is 162.3 mAh/g with CR 73.9%, which is clearly an increase in the electrochemical properties of the cell due to the addition of TTFP; When charging and discharging at 2.75-4.5 V, the capacity of battery with STD after 100 cycles at 0.2 C is 118.7 mAh/g, and the corresponding CR is 60.93%, while the discharged capacity of the battery containing 10TTFP is 150.0 mAh/g, whose corresponding CR was 65.39%. Besides, through the combustion test with and without TTFP electrolyte, it can be concluded that the TTFP-contained electrolyte is difficult to be ignited, and this result indicates that TTFP can enhance the safety performance of the battery efficiently. Conclusively, the incorporation of TTFP can be beneficial to improve the flame retardancy of the electrolyte, meanwhile, not to affect or even enhance the batteries’ electrochemical stability. Therein, the present work may provide a good direction for the next generation of high performance and high safety Lithium-ion batteries.