Abstract
Changes in the crystal structure and transition metal valency in 
positive electrodes during the charge‐discharge of 
cells were examined using ex situ X‐ray diffraction measurements, Fe and Co K‐X‐ray absorption near edge spectroscopy (XANES) and 
Mössbauer spectroscopy. An iron‐doped host material with rhombohedral symmetry was obtained up to 25% Fe per formula unit in 
by hydrothermal reaction below 300°C from a mixture of 
coprecipitate (iron‐doped CoOOH) and LiOH. No symmetry changes were observed during electrochemical charge‐discharge tests up to the tenth cycle. The structures of Li‐extracted and reinserted samples were determined by a model similar to 
prepared at low temperature in which Li ions are located at the interstitial 6c and octahedral 3a sites. 
Mössbauer and Fe and Co K‐XANES spectra at 293 K indicated the presence of tetravalent Fe ions upon oxidation up to 4.3 V. © 2000 The Electrochemical Society. All rights reserved.