Synthesis, structure, and phase relationship in lithium manganese oxide spinel

Phase relationships, structures, magnetic properties, and phase transitions in the lithium manganese oxide spinel were studied based on a wide variety of samples synthesized at temperatures over a range of 750 less than or equal to t less than or equal to 900 degreesC with Li/Mn ratios between 0.5 and 0.55 and various starting materials. The system was divided into three categories: oxygen deficient spinels, LiMn2O4-delta; lithium-substituted spinels, Li1+xMn2-xO4-delta; and the stoichiometric spinel, LiMn2O4. Their structures were discussed based on the structure data determined by TOF neutron and synchrotron X-ray Rietveld analysis. The amount of oxygen vacancy was determined to be delta approximate to 0.14(3) in LiMn2O4-delta, for example, for the spinel synthesized at 900 degreesC, and the nearly stoichiometric composition was obtained at 750 degreesC followed by heating at 470 degreesC for several times from lithium hydroxide and manganese oxides as starting materials. The oxygen vacancy was dependent upon the synthesis conditions and starting materials. It decreased as the Li/Mn ratio varied from 0.5 to 0.55, and as the synthesis temperature decreased from 900 to 750 degreesC. Based on the synthesis and structure results, the phase relationship in the ternary diagram, Li-Mn-O, is discussed.