XAFS study of LiCo1-xFexO2 cathode for rechargeable lithium battery by laboratory XAFS spectrometer

The change of local structure in layered-rock-salt-type iron doped lithium cobaltate LiCo1-xFexO2 under electrochemical Li deintercalation (charge) /r e-intercalation (discharge) was studied by a laboratory type XAFS spectrome ter. In Co K-XANES and Fe K-XANES of LiCo0.85Fe0.15O2 the absorption peak s hifted to higher energy by 1.5-2eV for Co K-edge and by 2-2.5eV for Fe K-ed ge, respectively, after the first charge. The spectra returned close to ini tial position and had almost original shape after the first discharge. In C o K- and Fe K-EXAFS of LiCo0.85Fe0.15O2 during the first charge and dischar ge the reversible change of the local structure was observed mainly around the Co atoms although the partly irreversible change of the local structure was found around the Fe atoms. The variation of local structure occurred i n similar manner for the samples with x=0.05 and 0.25. This indicates that both Co3+/Co4+ and Fe3+/Fe4+ redox reactions occur reversibly during the fi rst charge and discharge.