LiMn2O4 is used as the cathode material in large lithium ion batteries for industrial and other uses because of its low cost, excellent thermal stability, and other attributes. Nevertheless, LiMn2O4 has weak points including severe capacity, deterioration at high temperatures, and low energy density. To overcome these points we conducted our research and development with a focus on LiCo x Ni y Mn z O2 composite oxides (layered lithium manganese composite oxides). We developed an industrial synthesis technology for layered lithium manganese composite oxides, and employed them as the new cathode material for the EX25A, an industrial lithium ion battery. Compared with the lithium ion batteries that used LiMn2O4 as their cathode material, the EX25A has double cycle life characteristics at high-temperature (according to our standards), and is capable of large 10C discharges.