Thermoanalytical (TGA-DSC) and high temperature X-ray diffraction (HT-XRD) study of the thermal decomposition processes in Li2CO3-MnO mixtures

The thermal decomposition processes taking place in solid state mixtures Li2CO3-MnO (X-Li = 0.10-0.50, X-Li = lithium cathionic fraction) have been studied (in air) by High Resolution Thermogravimetric Analysis (HRes-TGA), Heat Flux Differential Scanning Calorimetry (Heat Flux-DSC and temperature variable X-ray Powder Diffractometry (HT-XRPD), in order to get a better understanding of the intermediate reaction stages and to assess the equilibrium compounds as well. As concerns the measurements performed on mixtures with X-Li < 0.333, LiMn2O4, and excess Mn2O3 are the obtained equilibrium products. By 0.33 < X-Li < 0.50 a mixture of LiMn2O4, and Li2MnO3 is obtained whose proportions depend on the reaction path followed. A stoichiometric model, where both lithium manganese oxides form simultaneously, holds for X-Li = 0.45 and 0.50 mixtures. A two stage model, where Li2MnO3 forms first, followed by reaction with excess Mn2O3 to yield LiMn2O4, is the reaction path for the X-Li = 0.35 mixture. (C) 2002 Elsevier Science B.V. All rights reserved.