PREPARATION AND ELECTROCHEMICAL CHARACTERIZATION OF MICRON-SIZED SPINEL LIMN2O4

The preparation and characterization of spinel LiMn2O4 having small av erage particle sizes (<4.0 mu m) and narrow particle size distribution are reported. They were obtained by heating a 1:4 Li2CO3/MnCO3 mixtur e at 650 to 850 degrees C in oxygen. Particle size control of the prod uct was achieved by controlling the particle sizes of the precursor ma terials and the heating conditions. Heating the Li2CO3/4MnCO(3) mixtur e 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 ele ctrolyte/LiMn2O4 cells cycled between 3.0 and 4.3 V. Specific capaciti es between 0.75 and 0.83 Li per LiMn2O4 were obtained for more than fi fty 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 subsequ ent performance in the 4 V region, while for the LiMn2O4 prepared at h igher temperatures, such cycling causes the 4 V capacity to decline.