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Document Version Version Comment Date Status
192691.0 [No comment] 16.10.2006 15:58 Released

ID: 192691.0, MPI für Festkörperforschung / FKF Publikationen 2004
Effect of iron on delithiation in LixCo1-yFeyO2. Part 2: in-situ XANES and EXAFS upon electrochemical cycling
Authors:Holzapfel, M.; Proux, O.; Strobel, P.; Darie, C.; Borowski, M.; Morcrette, M.
Date of Publication (YYYY-MM-DD):2004
Title of Journal:Journal of Materials Chemistry
Issue / Number:1
Start Page:102
End Page:110
Review Status:not specified
Audience:Not Specified
Abstract / Description:LixCo1-yFeyO2 solid solutions were examined in an in-situ
electrochemical X-ray absorption spectroscopy study using a plastic
battery configuration. XANES and EXAFS were applied to elucidate the
evolution of local symmetry and oxidation states of iron and cobalt
upon electrochemical cycling of three particular stoichiometries:
LixCo0.9Fe0.1O2, LixCo0.8Fe0.2O2 and LixCo0.6Fe0.4O2. While the cobalt
environment shows little variation, a distortion of the FeO6 octahedra
occurs quite rapidly for all three samples with a decrease in the next
neighbour numbers from six to four. This is ascribed to the Jahn-Teller
effect which affects Fe4+ (a d(4) system), that is formed upon
delithiation. No distortion is observed for cobalt. Along the
delithiation process a simultaneous increase in the edge energy occurs
for cobalt and iron in the case of y=0.1 and to a lesser extent for
iron than for cobalt for y=0.4. This means that the oxidation of Fe3+
occurs together with the oxidation of the cobalt matrix in the
cobalt-rich samples but becomes more difficult for iron-rich samples.
In the case of the cobalt-rich samples, the edge-energy for both
elements shifts back down at the end of charge, in spite of the
continuing oxidation of the cations. This effect is probably related to
the appearance of a new lithium-poor phase, that is not formed for
y=0.4, and confirms the in-situ X-ray diffraction results published in
the first part of this series.
External Publication Status:published
Document Type:Article
Communicated by:Michaela Asen-Palmer
Affiliations:MPI für Festkörperforschung
External Affiliations:UJF, INPG, CNRS, Lab Electrochim & Physicochim Mat & Interfaces, F-38402 St Martin Dheres, France.
; CNRS, Lab Champs Magnet Intenses, F-38042 Grenoble 9, France.
; Max Planck Inst Festkorperforsch, F-38042 Grenoble 9, France.
; UJF, Lab Geophys Interne & Tectonophys, CNRS, UMR, F-38400 St Martin Dheres, France.
; CNRS, Cristallog Lab, F-38042 Grenoble 9, France.
; European Synchrotron Radiat Facil, F-38043 Grenoble, France.
; UPJV, CNRS, Lab React & Chim Solides, F-80039 Amiens, France.
Identifiers:ISI:000187533200016 [ID No:1]
ISSN:0959-9428 [ID No:2]