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Article Dans Une Revue Nature Materials Année : 2013

P2-NaxVO2 system as electrodes for batteries and electron-correlated materials

Résumé

Layered oxides are the subject of intense studies either for their properties as electrode materials for high-energy batteries or for their original physical properties due to the strong electronic correlations resulting from their unique structure. Here we present the detailed phase diagram of the layered P2-NaxVO2 system determined from electrochemical intercalation/deintercalation in sodium batteries and in situ X-ray diffraction experiments. It shows that four main single-phase domains exist within the 0.5≤x≤0.9 range. During the sodium deintercalation (intercalation), they differ from one another in the sodium/vacancy ordering between the VO2 slabs, which leads to commensurable or incommensurable superstructures. The electrochemical curve reveals that three peculiar compositions exhibit special structures for x = 1/2, 5/8 and 2/3. The detailed structural characterization of the P2-Na1/2VO2 phase shows that the Na+ ions are perfectly ordered to minimize Na+/Na+ electrostatic repulsions. Within the VO2 layers, the vanadium ions form pseudo-trimers with very short V-V distances (two at 2.581 Å and one at 2.687 Å). This original distribution leads to a peculiar magnetic behaviour with a low magnetic susceptibility and an unexpected low Curie constant. This phase also presents a first-order structural transition above room temperature accompanied by magnetic and electronic transitions. This work opens up a new research domain in the field of strongly electron-correlated materials. From the electrochemical point of view this system may be at the origin of an entire material family optimized by cationic substitutions.

Domaines

Matériaux
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Dates et versions

hal-00776452 , version 1 (15-01-2013)

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Citer

Marie Guignard, Christophe Didier, Jacques Darriet, Pierre Bordet, Erik Elkaim, et al.. P2-NaxVO2 system as electrodes for batteries and electron-correlated materials. Nature Materials, 2013, 12 (1), pp.74-80. ⟨10.1038/nmat3478⟩. ⟨hal-00776452⟩
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