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Dérivés fluorés des différentes variétés allotropiques du carbone – Synthèse, caractérisation et application aux matériaux d'électrode

Abstract : Transition metals fluorides (NbF5, MoF6 and WF6) and oxyflyorides (VOF3 and CrO2F2) are intercalated into graphite under oxidizing fluorine atmosphere. These compounds are used in so far as precursor with an aim of realize a fluorine-oxygen exchange via an oxygenated compound silicium based: hexamehyldisiloxane. These new materials exhibit partial reversibility with electrochemical lithium intercalation. In the same way, reactivity of inorganics fluorides (BF3, TiF4, NbF5, MoF6 and WF6) with multiwall carbon nanotubes (MWNT), produced by catalytic way , is studies under fluorine atmosphere. The following process of purification: thermal treatment and acid washing, is used. Partial intercalation of nanotubes is observed by X-ray diffraction. With RPE studies, modification of electronic properties of MWNT is observated. Fluorination of [70] fullerene at a temperature of 320 °C, makes it possible to obtain a compound with a weak dispersion in composition. The C-F bond is ionocavalent type with a length of 0.149 nm. It's crystalline structure is cubic centred faces (cfc, a = 1.7949 nm). Electrochemical tests shows, in addition to defluorination of C70 molecule, a reversible intercalation of lithium; these two phenomenon being in competition. The graphite fluoride reduction (covalent or ionic) by different way (thermal, chemical or electrochemical) led to the obtention of disordered carbons. The electrochemical lithium storage is carried out by the intermediate of two phenomenon at E < 0.2 V and E > 0.8 V. The first one is attributed to lithium adsorption into the pore obtain by the process of reduction. At highest potential the dissociation of Li-X bond at edge of plans led to a supplementary capacity.
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Contributor : Jerome Giraudet <>
Submitted on : Monday, April 5, 2004 - 11:32:58 PM
Last modification on : Monday, February 22, 2021 - 2:30:04 PM
Long-term archiving on: : Wednesday, September 12, 2012 - 3:20:35 PM

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  • HAL Id : tel-00005785, version 1

Citation

Jérôme Giraudet. Dérivés fluorés des différentes variétés allotropiques du carbone – Synthèse, caractérisation et application aux matériaux d'électrode. Matériaux. Université Blaise Pascal - Clermont-Ferrand II, 2002. Français. ⟨tel-00005785⟩

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