THERMAL-STABILITY OF LI4MN5O12 ELECTRODES FOR LITHIUM BATTERIES

The thermal stability of the spinel, Li4Mn5O12, which is of interest a s an insertion electrode for 3 V lithium cells, has been studied by X- ray diffraction, differential thermal analysis, and thermogravimetric analysis at temperatures up to 1020 degrees C. The data show that as t he temperature is raised above 400 degrees C, oxygen and lithia (Li2O) are lost from the structure, which drives the composition of the spin el along the stoichiometric spinel tie-line from Li4Mn5O12 toward Mn3O 4. By products of the reaction are the rock-salt phases Li2MnO3 at mod erate temperature and LiMnO2 at high temperature. The data are consist ent with recent reports of the behavior of other lithium-manganese-oxi de spinels; the data highlight, in particular, the sensitivity of lith ium-rich spinels to temperatures above 400 degrees C. (C) 1996 Academi c Press, Inc.