Layered LiNi1/3Co1/3Mn1/3O2 has been synthesized by heating its precursor of Ni1/3Co1/3Mn1/3(OH)2 and Li2CO3 at the temperature around of 900°C in air, and applied in high-power lithium-ion secondary cells by mixed with LiCoO2 in mass ratios of 1:1 and 1:2. The lithium-ion secondary cells with mixture of LiNi1/3Co1/3Mn1/3O2 and LiCoO2 showed a potential change similar to that of cell with pure LiCoO2 under low-rate discharge condition. The ICR18650 LIB with the mixed positive electrode is capable of discharge at 15C current rate with a better electrochemical performance compared to that of pure LiNi1/3Co1/3Mn1/3O2. Especially, the ICR18650 LIB with the mixed positive electrode exhibits improved safety performance during overcharge period compared to LiCoO2. Therefore, the mixture of LiNi1/3Co1/3Mn1/3O2 and LiCoO2 is a promising alternative material to LiCoO2 for high-power LIB.