Layered LiCo1/3Ni1/3Mn1/3O2 was prepared by a solid state reaction at 1000 degreesC in air and examined in nonaqueous lithium cells. LiCo1/3Ni1/3Mn1/3O2 showed a rechargeable capacity of 150 mAh g(-1) in 3.5-4.2 V or 200 mAh g(-1) in 3.5-5.0 V. Operating voltage of Li / LiCo1/3Ni1/3Mn1/3O2 was by 0.2-0.25 V lower than that of a cell with LiCoO2 or LiMn2O4 and by 0.15-0.3 V higher than that with LiNiO2 or LiCo1/2Ni1/2O2 due to a complex solid solution mechanism.