A series of LiNi0.5 − x Mn0.5 − x Co2x O2 $$ \left( {0 < {2}x \leqslant 0.{33}} \right) $$ compounds were prepared by solid-state reaction from nickel manganese cobalt oxides, and their characteristics were investigated by X-ray diffraction, X-ray photoelectron spectroscopy, and charge–discharge test. LiNi0.5 − x Mn0.5 − x Co2x O2 samples have single phase of layered structure with a space group of $$ {\hbox{R}}\overline 3 {\hbox{m}} $$ for 2x = 0.02, 0.05, 0.10, 0.20, and 0.33. Both the lattice constants of a- and c-axis and Li/Ni mixing degree decreased with the increase in Co contents in samples. The valence states of Ni, Mn, and Co in the samples are predominantly +2, +4, and 3, respectively, with a small amount of Ni3+, Mn3+, and Co2+. LiNi0.475Mn0.475Co0.05O2 gives excellent cycling performance in the voltage range of 2.5–4.4 V at the current rate of 20 and 100 mA g−1 over 50 cycles. High-rate capacity test of LiNi0.34Mn0.33Co0.33O2 shows that even at a current rate of 1,000 mA g−1, stable capacity about 63 mAh g−1 is retained.