Absorbing electromagnetic energies and transferring to heat energies solid-state chemical reaction in microwave field and millimeter-wave field would happen. In present paper, the reactions for synthesis of LiMn2O4 compound as a cathode electrode material for Li-ion batteries in electromagnetic field were studied. The reaction finished in a shorter time comparing with conventional method. The microstructure of reaction product including phase of reaction products, solid-state reaction course in electromagnetic fields, and conventional solid-state syntheses were analyzed by using X-ray diffraction (XRD) and scanning electron microscope (SEM). The results show the chemical reactions in electromagnetic fields were influenced by several factors including soaking time, pre-heating and coupled agent, and it has a simpler route to obtain LiMn2O4 compounds due to the different reaction mechanism comparing with the conventional reaction method. (C) 2004 Elsevier B.V. All rights reserved.