Thermal stability of Li2MnO3: from localized defects to the spinel phase

Abstract

The thermal stability of Li₂MnO₃ has been investigated by the means of coupled differential thermal analysis and thermogravimetric analysis associated with powder X ray diffraction. Various experiments performed in air and in argon allowed us to propose a mechanism of spinel-type defects formation in intergrowth with Li₂MnO₃ when treated in air above 900 °C. The fidelity of the DIFFaX simulations performed led to the understanding of the influence of the existence of spinel type defects intergrowth on X ray and electron diffraction patterns. The formation of these defects occurs during cooling and is preceded by the formation of LiMnO₂ defects in heating. With sufficiently long thermal treatments, defects expand such that a spinel type phase can be observed after cooling.