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Synthèse et caractérisation de nanomatériaux et de nanocomposites, étude de leurs propriétés électrochimique vis à vis de l'insertion du lithium

Abstract : Nanoscale materials offer the obvious advantage of combining structural effects (inside grain structure) with surface effects or grain-boundary effects. Therefore, the electrochemistry of this type of materials is very different from that of traditional microcrystalline ones mainly due to the contribution of the nano scale and of the ‘surface defects'. This work is focus on the electrochemical insertion of lithium ions and has been illustrated by the study of iron oxide nanoparticles (γ-Fe2O3, maghémite), core-shell nanohybdrids made of γ-Fe2O3 nanoparticles and conducting polymers and finally by nanocomposites made of TiO2 nanoparticules inserted inside lamellar MoO3. First are presented some generalities about the conducting polymers used, an overview of core shell nanohybrids comprising conducting polymers and finally and an overview on nanomaterials for lithium insertion. In a second part, the synthesis and the study of maghemite nanoparticules by electrochemical impedance spectroscopy (IES) that up to 1,3 Li by Fe2O3 (230 mAh/g) can be reversibly inserted as opposed to the microcrystalline analouges. The IES show the presence of a two step insertion process implying first a surface insertion followed by a core insertion moreover results show that the insertion mechanism occurs in an aggregate of nanoparticules. In a third part, the core shell nanohybrids (γ-Fe2O3/conducting polymers) are presented. To achieve a well define core shell structure, we have to pass through surface modification in the aim to promote the polymerisation of monomers adsorption on the iron oxide nanoparticle surface. Improved electrochemical properties, up to 450 mAh/g, have been observed and are due to a better separation of nanoparticles and to the presence of conducting material on the surface of iron oxide.In the last part the synthesis of TiO2/MoO3 nanocomposite take place in a two step reaction implying first the exfoliation of MoO3 and restacking of the material with TiO2 nanoparticles between the layered oxides. The characterization show a well ordered phase with Improved electrochemical properties, 400 mAh/g as compared to the starting materials with 350 mAh/g of MoO3 and 180 mAh/g of TiO2, due to an opened structure witch improved the lithium insertion.
Results obtained with these materials give a positive indication to the use of electrodes for small power Li-ion battery.
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  • HAL Id : tel-00136201, version 1



Mathieu Quintin. Synthèse et caractérisation de nanomatériaux et de nanocomposites, étude de leurs propriétés électrochimique vis à vis de l'insertion du lithium. Matériaux. Université Sciences et Technologies - Bordeaux I, 2006. Français. ⟨tel-00136201⟩



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