Crystal Structure Analysis of γ-Fe2O3 in the Process of Chemical Li Insertion

摘要

y-Fe2O3 has a spinel structure containing cation vacancies and is expected to function as cathode material in the secondary Li-ion batteries for lithium insertion/extraction. Lithium was chemically inserted into γ-Fe2O3 using 0.5 M solution of n-butyl lithium hexane and the crystal structure in the process of lithium insertion was examined by means of X-ray diffraction measurement and the Rietveld analysis. It was found that the sample was mixture of two phase both belonging to the space group of Fd3m, one is lithium rich and another is lithium lean. It is considered that the chemical lithium insertion take two phase process, i.e. inserted lithium forms a Li-rich phase in which the Li amount is constant, and the overall Li concentration is controlled by the mol fraction change in Li-rich phase and Li-lean phase.