Relaxation structure analysis of Li inserted γ-Fe2O3

gamma-Fe2O3 has a spinel structure with cation vacancy and is expected to perform as a favorable electrode material for secondary lithium-ion battery. When lithium is inserted electrochemically into gamma-Fe2O3, prolonged potential change is observed after the insertion. In this study, we inserted various amount of Li into gamma-Fe2O3 (x = 0.66, 1.1, 1.5 in terms of LixFe2O3), then made the circuit open, measured X-ray diffraction (XRD) patterns at various elapsed time, and analyzed the crystal structure change of gamma-Fe2O3 with time by the Rietveld method. The X-ray Rietveld analysis revealed that the iron occupancy of 8a site decreased and that of 16c site increased with lithium insertion process and after lithium insertion, the iron occupancy of 8a site increased and that of 16c site decreased gradually with relaxation time. It is indicated that lithium prefer 8a site to occupy kinetically, on the other hand, prefer 16c site thermodynamically. (C) 2011 Elsevier B.V. All rights reserved.