The research, development and application of high energy density lithium ion batteries are strictly restricted by several challenges, particularly the severe capacity degradation of the batteries at high voltage and elevated temperature. In this work, beneficial surface films are simultaneously formed on both electrodes of a 4.5 V graphite│LiNi0.5Mn0.3Co0.2O2 pouch cell via reduction and oxidation polymerizations of a novel multifunctional additive Tripropargyl Phosphate (TPP). The results demonstrate that the addition of 1.0 wt% TPP into the pouch cell not only improves its initial coulombic efficiency by 4.4%, but also remarkably enhances its cycling stability at both 25 °C and 55 °C. The enhanced cycling stability at high temperature can be attributed to the capture of acidic corrosive species in the electrolyte and the construction of robust protective films on the surface of the electrodes. These two effects significantly mitigate the decomposition of Ethyl Methyl Carbonate (EMC), reduce the dissolution of transition metal from cathode, and eliminate the formation of cracks inside the LiNi0.5Mn0.3Co0.2O2 and graphite particles.