NOVEL SYNTHESIS PROCESS AND STRUCTURAL CHARACTERIZATION OF LI-MN-O SPINELS

A new process for the synthesis of well-crystallized lithium manganese spinels with a homogenous composition Li1+xMn2-xO4 (0 less than or eq ual to x less than or equal to 0.333) has been developed using the sto ichiometry mixture of lithium acetate LiOAc and manganese nitrate Mn(N O3)(2) as starting materials, The decomposition of the raw materials a nd the stoichiometry mixture was studied using TG-DTA; the formation o f lithium manganospinels occurs below 400 degrees C. The crystallites appear to he single crystals in SEM micrographs. The size of the cryst allites was in the range of 0.1 to 2.0 mu m and depended on the synthe sis conditions. The crystal structure of these compounds was studied u sing X-ray powder diffraction and Rietveld refinement. The lattice par ameter and manganese occupancy at 16d sites in the space group Fd (3) over bar m are sensitive to both the synthesis temperature and the com position of the spinels (Li/Mn ratio) as a result of the variation in manganese valency. Synthesis temperature, atmosphere, and the Li/Mn ra tio in the starting materials are the key issues for control of the ma nganese valency in spinel Li1+xMn2-xO4 (0 less than or equal to x less than or equal to 0.333) for use in rechargeable lithium batteries. (C ) 1998 Academic Press.