In situ Fe K-edge X-ray absorption spectroscopy study during cycling of Li sub(2)FeSiO sub(4) and Li sub(2.2)Fe sub(0.9)SiO sub(4) Li ion battery materials

In situ X-ray Absorption Spectroscopy (XAS) results are presented for Li sub(2)FeSiO sub(4) and Li sub(2.2)Fe sub(0.9)SiO sub(4), promising cathode materials for lithium-ion batteries. The aims are to establish the valence and local structure of Fe during charge and discharge to understand if the Fe...

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Published in:Journal of materials chemistry. A, Materials for energy and sustainability Materials for energy and sustainability, 2015-03, Vol.3 (14), p.7314-7322
Main Authors: Brownrigg, Alexander W, Mountjoy, Gavin, Chadwick, Alan V, Alfredsson, Maria, Bras, Wim, Billaud, Juliette, Armstrong, ARobert, Bruce, Peter G, Dominko, Robert, Kelder, Erik M
Format: Article
Language:English
Subjects:
Absorption spectroscopy
Bonding
Cathodes
Constants
Cycles
Electrolytes
Iron
Lithium-ion batteries
Sustainability
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Summary:In situ X-ray Absorption Spectroscopy (XAS) results are presented for Li sub(2)FeSiO sub(4) and Li sub(2.2)Fe sub(0.9)SiO sub(4), promising cathode materials for lithium-ion batteries. The aims are to establish the valence and local structure of Fe during charge and discharge to understand if the Fe super(3+)/Fe super(4+) redox pair can be reached in the current battery design. It is found that the valence state changes between Fe super(2+) and Fe super(3+), with no evidence of Fe super(4+) before the onset of electrolyte degradation. There is a reversible contraction and extension of the Fe-O bond lengths during cycling while the Fe-Si distance remains constant, which underlines the stability of the Li sub(2)FeSiO sub(4) material. The same observations apply to Li sub(2.2)Fe sub(0.9)SiO sub(4) cathode material indicating that changing the stoichiometry does not provide any additional structural stability.
ISSN:2050-7488
2050-7496
DOI:10.1039/c4ta06305h