NMR and FT-IR investigation of spinel LiMn2O4 cathode prepared by the tartaric acid gel process

The structure of the lithium manganese tartrate precursor and the synthesis mechanism of LiMn2O4 were investigated by FT-IR, NMR, TG/DSC, and XRD in t his study. The results of FT-IR and Li-7 and C-13 NMR measurements revealed that lithium ions bond with carboxylic acid ligands and the O-H stretching modes of tartaric acid. Manganese ion bonds only with carboxylic acid. Lit hium and manganese ions were trapped homogeneously on an atomic scale throu ghout the precursor. Such a structure eliminates the need for long-range di ffusion during the formation of lithium manganese oxides. Therefore, spinel LiMn2O4 was synthesized at temperatures as low as 300 degreesC. In this wo rk, the electrochemical properties of Li/LixMn2O4 were studied. It is clear that the discharge curves exhibit two pseudo plateaus as the LiMn2O4 is fi red to higher temperatures. The discharge capacity of LiMn2O4 increases fro m 84 to 117 mAh/g as the calcination temperature increases from 300 to 500 degreesC. The LiMn2O4 powders calcined at low temperatures with a high spec ific surface area and an average valence of manganese exhibit a better cycl e life. (C) 2001 Academic Press.