Structural and electrochemical properties of LiAlyCo1-yO2 cathode for Li rechargeable batteries

LiAlyCo1-yO2 powders were synthesized at 800 degrees C using acrylic acid as a chelating agent. The comparison between local structure refinements of LiCoO2 and LiAl0.25Co0.75O2 during the charging and cycling process was carried out by Co K-edge X-ray absorption spectroscopy (XAS). Al addition was found to cause a larger local structure distortion during Li deintercalation compared to that of LiCoO2. Extended X-ray absorption fine structure refinements during Li deintercalation showed that the degree of structural disorder around Co atoms in LiAl0.25Co0.75O2 becomes higher than that of LiCoO2. XAS analysis for LiCoO2 and LiAl0.25Co0.75O2 during cycling revealed that the large capacity fading of the LiAl0.25Co0.75O2 electrode could be explained by the remaining Co4+ ions and local structure distortion. (C) 2000 The Electrochemical Society. S0013-4651(99)10-104-6. All rights reserved.