High-voltage cathode material, LiMn1.5Ni0.5O4, was successfully prepared by two-step process: LiMn1.6Ni0.4O4 particles were obtained by the solid state reaction of oxalate precursors at high temperature such as 900°C and then the LiMn1.6Ni0.4O4 particles with Li-acetate di-hydrate and Ni-acetate tetra-hydrate were annealed at low temperature. Both spinel phases are ferromagnetic compounds: LiMn1.5Ni0.5O4 has higher Neel temperature (127K) and larger magnetization (97emu/g at 4.2K) than LiMn1.6Ni0.4O4 does (103K and 79emu/g). The obtained LiMn1.5Ni0.5O4 particles had low specific surface area, which may reduce the side reaction with the organic electrolyte, and exhibited electrochemical capacity only at high voltage 4.7V region. In addition, high reversible capacity as well as good cycle performance was attained.