Single phase LiCo1-xMxO2 (M = Al and Mg) cathode materials for Li-ion batteries are synthesized by microwave dielectric heating with a reaction time less than 20 min. Aluminium forms solid solutions up to a composition of x = 0.5 and magnesium up to x = 0.2. Lattice constants are found to vary with the composition. The compounds are electrochemically active with good discharge capacity. (C) 2003 Elsevier B.V. All rights reserved.