The high rate discharge behavior of a lithium-ion secondary battery (LIB) in which each LiCoO2 and Li metal corresponds to the cathode and the anode is investigated with the introduction of functional additives. Representative additives such as vinylene carbonate, tris(pentafluorophenyl)borane (TPFPB), and biphenyl are generally chosen for anode stabilization, anion reception, and cathode protection, respectively. Even if there is no result showing the correlation between high rate performance and electrolyte, TPFPB apparently improves the high rate performance of LIB. This impressive result may provide the possibility that the introduction of a functional additive can be another way to attain a high power density of LIB for application in hybrid electric vehicles or electric vehicles.