Spinel compound LiNi0.5Mn1.5O4 was synthesized by a chemical wet method. Mn(NO3)(2), Ni(NO3)(2.6)H2O, NH4HCO3 and LiOH-H2O were used as the starting materials. At first, Mn(NO3)(2) and Ni(NO3)(2.6)H2O reacted with NH4HCO3 to produce a precursor, then the precursor reacted with (LiOHH2O)-H-. 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 4.6-4.8 V in the charge/discharge process. The LiNi0.5Mn1.5O4 had a discharge specific capacity of 118 mAh/g at about 4.6 V and 126 mAh/g in total in the first cycle at a discharge current density of 2 mA/cm(2). After 50 cycles, the total discharge capacity was above 118 mAh/g. (C) 2004 Elsevier Ltd. All rights reserved.