In order to control the grain size of LiMn2O4 cathode material, microwave synthesis technique has been applied to two kinds of starting mixtures. One of the starting mixtures is composed of UOH.H2O and Mn2O3, and the other is a precursor obtained by drying an aqueous solution of LiNO3 and Mn(NO3)(2).4H(2)O. The grain size of samples was measured by a particle size analyzer and scanning electron microscopy. Microwave technique found the grain size of both samples to be fine (similar to 0.2-0.5 gm) compared with conventional solid-state reaction. In addition, samples obtained by microwave technique show good electrochemical Li charge-discharge cycle performance. (C) 2003 Elsevier B.V. All rights reserved.