Study of C-coated LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} as positive electrode material for Li-ion batteries
- Institut Charles Gerhardt Montpellier, UMR 5253 CNRS-UM2-ENSCM-UM1 Agregats, Interfaces et Materiaux pour l'Energie CC 1502, Place Eugene Bataillon, 34095 Montpellier, Cedex 5 (France)
- IPREM-ECP, Universite de Pau, Helioparc, 2 av. Pierre Angot, 64053 Pau, Cedex 9 (France)
- Sued-Chemie AG, Ostenriederstr. 15, D-85368 Moosburg (Germany)
- SAFT, 111-113 bd. Alfred Daney, 33074 Bordeaux, Cedex (France)
Commercial C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} positive electrode material has been investigated by {sup 57}Fe Moessbauer Spectroscopy (MS), X-ray Photoelectron Spectroscopy (XPS) and X-ray Absorption Spectroscopy (XAS). The combined use of these experimental techniques provides a better understanding of the electrochemical reaction involved during cycling. {sup 57}Fe MS is very efficient to directly follow oxidation state of Fe in the electrode, and gives surprisingly indirect information on the oxidation state of Mn as observed by XAS and XPS. The electrochemical mechanism is proposed based from in situ and operando investigations using both MS and XAS, and is consistent with XPS surface studies. XPS analysis of the electrodes at the end of charge (4.4 V) reveals enhanced electrode/electrolyte interface reactivity at this high potential. Aging of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4}/Li cells after 50 cycles at 60 Degree-Sign C indicates a rather good electrochemical behavior (low capacity fading) of the electrode material. Both {sup 57}Fe MS and XPS (Mn 2p and Fe 2p) clearly show no modification on Fe and Mn oxidation state compared to fresh electrode confirming the good electrochemical performances. - Graphical abstrct: Quantitative evaluation of the Fe{sup 3+} and Mn{sup 3+} content during the first charge/discharge cycle obtained from K-edge XANES spectra of C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} recorded upon cell operation at RT with C/10 rate. During the charge co-existence of Fe and Mn oxidation is observed between points 2 and 4 of the potential curve. At the end of the charge the cut-off voltage limits the oxidation at about 93%. Highlights: Black-Right-Pointing-Pointer C-LiFe{sub 0.33}Mn{sub 0.67}PO{sub 4} electrode material upon cycling vs. metallic lithium. Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy is a (in)direct probe for Fe(Mn) oxidation state. Black-Right-Pointing-Pointer Both K-Fe and K-Mn edges XAS show a simultaneous oxidation of Fe{sup 2+} and Mn{sup 2+} in a small range of compositions. Black-Right-Pointing-Pointer Surface analysis from XPS allows reveals slight differences at the surface of the electrode with respect to the bulk.
- OSTI ID:
- 22131123
- Journal Information:
- Journal of Solid State Chemistry, Vol. 192; Other Information: Copyright (c) 2012 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA); ISSN 0022-4596
- Country of Publication:
- United States
- Language:
- English
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