Thermal decomposition of LixCoO2 monitored by electron energy loss spectroscopy and magnetic susceptibility measurements
Abstract While it is commonly known that layered Li x CoO 2 transforms to a mixture of stoichiometric LiCoO 2 and Co 3 O 4 at elevated temperature, little experimental detail exists on the role time and temperature play in the transformation process or on the occurrence of possible intermediate phases. In this article we follow the thermal decomposition of Li x CoO 2 by characterizing its decomposition products after short and long-term isothermal annealing at 350 °C. X-ray diffraction and transition electron microscopy observations are complemented by electron energy loss spectroscopy and magnetic susceptibility measurements thus allowing the combination of structural and electronic information. Our results indicate that the charge balance upon Li extraction from LiCoO 2 is in parts accomplished by oxidation of Co 3+ to Co 4+ . In the annealed powder we observe an intermediate Li–Co–O phase of cubic spinel structure before the end products Co 3 O 4 and CoO are formed.