The preparation and characterization of spinel LiMn2O4 having small average particle sizes (<4.0 mu m) and narrow particle size distribution are reported. They were obtained by heating a 1:4 Li2CO3/MnCO3 mixture at 650 to 850 degrees C in oxygen. Particle size control of the product was achieved by controlling the particle sizes of the precursor materials and the heating conditions. Heating the Li2CO3/4MnCO(3) mixture results in the formation of Mn2O3 initially, which then reacts with Li2CO3 to form spinel LiMn2O4 according to : 2Li(2)CO(3) + 4 Mn2O3 + O-2 --> 4LiMn(2)O(4) + 2CO(2). The LiMn2O4 cathodes have shown excellent rechargeability as well as superior rate capability in Li/polymer electrolyte/LiMn2O4 cells cycled between 3.0 and 4.3 V. Specific capacities between 0.75 and 0.83 Li per LiMn2O4 were obtained for more than fifty cycles. The LiMn2O4 cathodes can be reversibly cycled between 2.4 and 3.5 V but with declining capacity. For the LiMn2O4 prepared at 650 degrees C, cycling in the 3 V region has little effect on its subsequent performance in the 4 V region, while for the LiMn2O4 prepared at higher temperatures, such cycling causes the 4 V capacity to decline.