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Synthèse et étude électrochimique de matériaux silicates utilisés en tant qu'électrode positive pour les accumulateurs Li-Ion

Abstract : The society is currently facing challenges such as global warming and rarefaction of resources. These issues have a factor in common, energy and more specifically its storage, for which lithium-ion batteries are today the state-of-the-art technology. Researchers and industries are focusing on the increase of energy density and safety and the reduction of toxic, costly and rare elements. In this study, positive electrodes based on silicate polyanionic materials are considered to fulfill these requirements. Two materials are studied, Li2MnSiO4 that exhibits appealing large capacity (>300mAh.g-1) and an unreported LiMnSiO4 with olivine structure that would have medium capacity (174 mAh.g-1) but associated with a high voltage (>3.7V).In a first part, a nanocomposite material Li2MnSiO4/C is synthesized by sol-gel route. Its electrochemical and structural properties are studied. The different degradation phenomena are discussed thereafter. Al-doped and Mn-rich Li2-xMn1+xAlxSi1-xO4/C is also proposed to lower the structural collapse during cycling. Finally the impact of its storage in air is assessed and a mechanism is proposed to explain the formation of Li2CO3.In a second part, a multistep synthesis is designed starting from olivine MgMnSiO4/C, followed by chemical oxidation and electrochemical lithiation to obtain LiMnSiO4/C. Each step is characterized to assess the structure, oxidation degree and electrochemical behavior of the final material.Finally, the testing of the two materials for space applications (LEO and GEO satellites profiles) confirms the better cyclability of LiMnSiO4/C and its validity as promising alternative to the conventional unstable Li2MnSiO4 compound
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https://tel.archives-ouvertes.fr/tel-01818023
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Submitted on : Thursday, June 21, 2018 - 2:31:58 AM
Last modification on : Monday, May 18, 2020 - 10:23:35 PM
Long-term archiving on: : Wednesday, September 26, 2018 - 6:35:17 PM

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  • HAL Id : tel-01818023, version 2

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Guillaume Lefevre. Synthèse et étude électrochimique de matériaux silicates utilisés en tant qu'électrode positive pour les accumulateurs Li-Ion. Energie électrique. Université Grenoble Alpes, 2018. Français. ⟨NNT : 2018GREAI021⟩. ⟨tel-01818023v2⟩

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