Thermal Stability and Structural Changes of Li4Mn5O12under Oxygen and Nitrogen Atmosphere

Abstract

The thermal stability and structural changes of well-crystallized Li4Mn5O12powder with a grain size of 0.1–0.3 μm have been investigated with thermogravimetric analysis (TGA), X-ray diffraction (XRD), and high-temperature X-ray diffraction measurements (HT-XRD). Li4Mn5O12crystallites are stable at temperatures up to 600°C in oxygen or air, but decompose to spinel LiMn2O4and monoclinic Li2MnO3at temperatures between 530 and 680°C, and to LiMnO2and Mn3O4at temperatures above 680°C in nitrogen. No apparent structural change was detected with XRD and HT-XRD when Li4Mn5O12was heated in O2up to 700°C, but a reversible weight loss/gain due to the evolution/uptake of oxygen was observed by TGA between 400–700°C. The deficiency of oxygen in Li4Mn5O12-δis found to be in the region 0 < δ ≤ 0.5.