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Nantes, France

Dupre N.,Jean Rouxel Institute | Cuisinier M.,Jean Rouxel Institute | Guyomard D.,IMN
Electrochemical Society Interface | Year: 2011

Li NMR is a powerful tool to study the surface layer on Li-ion battery electrode materials, especially coupled with techniques giving chemical information such as XPS or FTIR. Concerning the organic part of the interphase, the use of 13C NMR has proved also to be of great interest to understand the decomposition or reaction pathway of organic solvents even though the need of isotopic enrichment and the sensitivity of 13C NMR to the presence of paramagnetic centers complicate the detection. In the case of materials containing transition metals with unpaired electrons, in addition to the chemical composition and quantification, it is possible to extract physical or topological information from electron-nucleus dipolar interaction. The detection and observation of electrode/electrolyte interphase using NMR technique is now applied to a wide range of cathode and anode materials for lithium-ion batteries and is becoming an efficient characterization tool in this research area.

Parlebas J.C.,CNRS Institute of Genetics and of Molecular and Cellular Biology | Demangeat C.,University of Strasbourg | Mokrani A.,IMN | Yartsev S.V.,ZAO NPO Spektr | And 2 more authors.
European Physical Journal B | Year: 2011

The spin density wave's onset in Cr based superlattices is considered within proximity of Fe interlayer boundaries and the effect of randomly located vacancies in Cr monolayers is examined. The study is performed for Fe/Cr, Fe/Cr/V superlattices with odd and even number of Cr monolayers. It is shown that the number of Cr monolayer determines the spin density wave's nodes onset in the perfect Fe/Cr super lattices. Pinning of Cr magnetic moments on vacancies destroys this determination and leads to appearance or disappearance of nodes. © 2011 EDP Sciences, SIF, Springer-Verlag Berlin Heidelberg.

Emery N.,CNRS East Paris Institute of Chemistry and Materials Science | Panabiere E.,CNRS East Paris Institute of Chemistry and Materials Science | Crosnier O.,IMN | Crosnier O.,French National Center for Scientific Research | And 6 more authors.
Journal of Power Sources | Year: 2014

The Li7MnN4 structural response upon the first Li extraction-insertion cycle is highlighted using in operando XRD experiments. A 3-phases mechanism involving two biphasic regions for 0.1 ≤ x ≤ 0.8 and 0.8 ≤ x ≤ 1.2 in Li7-xMnN4 and a solid solution behaviour (1.2 ≤ x ≤ 1.5) explains its electrochemical fingerprint. These successive structural transitions do not change the cubic symmetry of the cell and induce a limited cell contraction (∼7%) associated to a reversible mechanical strain. This finding partly explains the excellent cycle life of this promising negative electrode for Li-ion batteries. © 2013 Elsevier B.V. All rights reserved.

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