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≤x≤0.333) has been developed using the stoichiometry mixture of lithium acetate LiOAc and manganese nitrate Mn(NO3)2as starting materials. The decomposition of the raw materials and the stoichiometry mixture was studied using TG–DTA; the formation of lithium manganospinels occurs below 400°C. The crystallites appear to be single crystals in SEM micrographs. The size of the crystallites was in the range of 0.1 to 2.0 μm and depended on the synthesis conditions. The crystal structure of these compounds was studied using X-ray powder diffraction and Rietveld refinement. The lattice parameter and manganese occupancy at 16dsites in the space groupFd3mare sensitive to both the synthesis temperature and the composition of the spinels (Li/Mn ratio) as a result of the variation in manganese valency. Synthesis temperature, atmosphere, and the Li/Mn ratio in the starting materials are the key issues for control of the manganese valency in spinel Li1+xMn2−xO4(0≤x≤0.333) for use in rechargeable lithium batteries.