LiNi0.5Mn1.5O4 spinel has been prepared by an emulsion drying method which can intermix cations very homogeneously at the atomic scale. When the emulsion-dried precursor was fired at 750°C for 24 h, the observed particle of the LiNi0.5Mn1.5O4 was nano-crystallite, being about 50 nm in diameter. The Rietveld refinement result clearly exhibited that the cubic spinel phase was successfully formed without any secondary phases, indicating that Li and transition metal cations occupied the 8a and 16d sites of the Fd3m structure, respectively. Li deintercalation from the spinel framework brings about a shift in the XRD peak toward higher angles and a peak splitting in the composition range δ=0–0.2 in Li δ Ni0.5Mn1.5O4, implying that the host structure is progressively oxidized from Ni2+ to Ni4+ and accompanied by a two phase reaction. The sample calcined at 750°C for 24 h showed the best cyclability upon cycling due probably to better crystallinity and a smaller particle size. We suggest that this material can be used as a 4.5 V cathode material for Li-ion battery.