Spinel compound LiNi0.5Mn1.5O4 was synthesized by a chemical wet method. Mn(NO3)2, Ni(NO3)2·6H2O, NH4HCO3 and LiOH·H2O were used as the starting materials. At first, Mn(NO3)2 and Ni(NO3)2·6H2O reacted with NH4HCO3 to produce a precursor, then the precursor reacted with LiOH·H2O to synthesize product LiNi0.5Mn1.5O4. The product showed a single spinel phase under appropriate calcination conditions, and exhibited a high voltage plateau at about 4.6–4.8V in the charge/discharge process. The LiNi0.5Mn1.5O4 had a discharge specific capacity of 118mAh/g at about 4.6V and 126mAh/g in total in the first cycle at a discharge current density of 2mA/cm2. After 50 cycles, the total discharge capacity was above 118mAh/g.