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Issue 38, 2013
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Structural phase transformation and Fe valence evolution in FeOxF2−x/C nanocomposite electrodes during lithiation and de-lithiation processes

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Abstract

In this study, the structural changes of FeOxF2−x/C during the first discharge and recharge cycles were studied by ex situ electron microscopy techniques including annular dark field scanning transmission electron microscopy (DF-STEM) imaging, selected area electron diffraction (SAED) and electron energy loss spectroscopy (EELS) as well as by in situ X-ray absorption spectroscopy (XAS). The evolution of the valence state of Fe was determined by combined EELS using the Fe-L edge and XAS using the Fe-K edge. The results of this investigation show that the conversion reaction path during 1st lithiation is very different from the re-conversion path during 1st delithiation. During lithiation, intercalation is first observed followed by conversion into a lithiated rocksalt (Li–Fe–O–F) structure, and metallic Fe and LiF phases. During delithiation, the rocksalt phase does not disappear, but co-exists with an amorphous (rutile type) phase formed initially by the reaction of LiF and Fe. However, a de-intercalation stage is still observed at the end of reconversion similar to a single phase process despite the coexistence of these two (rocksalt and amorphous) phases.

Graphical abstract: Structural phase transformation and Fe valence evolution in FeOxF2−x/C nanocomposite electrodes during lithiation and de-lithiation processes

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Publication details

The article was received on 29 May 2013, accepted on 24 Jul 2013 and first published on 15 Aug 2013


Article type: Paper
DOI: 10.1039/C3TA12109G
Citation: J. Mater. Chem. A, 2013,1, 11629-11640
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    Structural phase transformation and Fe valence evolution in FeOxF2−x/C nanocomposite electrodes during lithiation and de-lithiation processes

    M. Sina, K.-W. Nam, D. Su, N. Pereira, X.-Q. Yang, G. G. Amatucci and F. Cosandey, J. Mater. Chem. A, 2013, 1, 11629
    DOI: 10.1039/C3TA12109G

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