1. The preparation of Al-doped spinel LiMn2O4 cathode materials has been studied detailedly, and we have made some improvement. Pure-phase and well-crystallized Al-doped spinel LiMn2O4 powders as a cathode material for lithium-ion battery were successfully synthesized by a new simple rheological-phase-assisted microwave synthesis method. The results of the experiments indicate that the rheological-phase-assisted microwave synthesis method has the advantages of shorter sintering time and energy-saving. The synthesized powders are pure, spinel-structure particles of regular shapes with uniform distribution. The best condition for synthesizing is sintering at 750℃ for 2h. The structure and surface morphology of the as-synthesized samples compared with the pristine LiMn2O4 and LiAl0.03Mn1.97O4 obtained from the traditional solid-state reaction method have been investigated. The powders were used as positive materials for lithium-ion battery, whose charge/discharge properties and cycle performance have been examined in detail. The results reveal that the powders prepared by the rheological-phase-assisted microwave synthesis method exhibit a higher initial discharge capacity of 115mAh/g, much better reversibility and good cycling stability without discharge capacity fading, retaining 115mAh/g around. 2. In this thesis we also introduce research of spherical cathode material used in lithium-ion battery, elaborating a special emulsion method and its mechanism. The primary LiMn2O4 was synthesized by microwave synthesis method, and the secondary particle was prepared by the special emulsion method. The secondary particle was researched by SEM and XRD. Its tap density and electrochemical performance were tested. It was found that the primary LiMn2O4 grew right along during the second sintering, but the morphology was not ideally spherical. The result was analyzed for the further research.