Cobalt-free layered oxide cathode material (LiMn0.5Ni0.5O2) was obtained via a two-step synthesis method. Firstly, hydrothermal synthesis of α-MnOOH with nanorod morphology was achieved and then a co-precipitation process to obtain the LiMn0.5Ni0.5O2 active layered material with disordered structure was performed. The thermal treatment performed on the active materials resulted in a good-controlled balance between formed monoclinic-rhombohedral phases. It was found that the controlled mixing of structural phases plays an important role in improving the electrochemical performance of the active cathodic layer material, resulting in an adequate balance between high discharge capacity and electrochemical stability during the cycling. The active material thermally treated at 800 °C displayed outstanding discharge capacity of 235.05 mAh g-1 at 20 mA g-1 in CCCV (Current Constant-Constant Voltage) mode. While, in CC (Current Constant) mode showed the highest discharge capacity, of 178.95 mAh g-1 at 20 mA g-1 and good capacity retention (87.2% after 100 cycles).