The cathode-active materials LiMn2O4,LiAl0.1Mn1.9O4, and LiAl0.1Mn1.9O3.9F0.1 were synthesized by a microwave-assisted sol-gel method. The influence of different doping elements on the structural and electrochemical properties of the as-prepared samples was investigated by thermogravimetric analysis (TGA), X-ray diffraction (XRD), transmission electron microscopy (TEM), and electrochemical experiments. The results indicated that fluorine plays an important role in controlling the morphology, and the doped aluminum could enhance significantly the stability of spinel-type LiMn2O4. The initial discharge capacity of the Al3+ and F- co-substituted specimen reached 129.8 mA h/g and has a high capacity retention after 40 cycles. The outstanding electrochemical properties of LiAl0.1Mn1.9O3.9F0.1 make it a possible promising cathode material for lithium-ion batteries. (c) 2005 Elsevier Inc. All rights reserved.