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Développement et compréhension des mécanismes électrochimiques des accumulateurs Lithium-ion/Soufre

Abstract : Using Li2S instead of S8 as active material allows metallic lithium free batteries, also called Lithium-ion/Sulfur batteries, to be developed and safer systems with high energy density to be designed. The main difference between S8 and Li2S-based systems lies in the first charge. Indeed, during this first charge, a high polarization occurs with lack of reproducibility. Then, the main goal of this work is to focus on the analysis and understanding of the Li2S particle size impact on the electrochemical mechanism during the first charge of a Li-ion/Sulfur battery. Three Li2S types have been studied in this work: two nanometric Li2S and a micrometric one. Firstly, classical PVdF (polyvinylidenefluoride) binder was demonstrated to be highly reactive with nanometric Li2S leading to a new formulation based on PEO (polyethylene oxide) to be developed. Electrochemical investigations confirmed that starting with Li2S nanoparticles can effectively suppress the overall charge polarization. To go deeper, operando characterizations such as X-Ray Diffraction (XRD) and Resonant Inelastic X-ray Scattering (RIXS) have been carried out in order to correlate the particle size and the BET surface area effects. XRD results show that Li2S and β-sulfur phases coexist almost all along the first charge when starting with micrometric Li2S, while no polysulfides are detected by RIXS analysis. Therefore, a solid/solid (micrometric Li2S-->S8) reaction is suggested when using micrometric Li2S. On the opposite, when starting with nanometric Li2S particles, a very classical behavior (Li2S-->Polysulfides in solution-->S8) is obtained with the successive existence of the two solid phases with polysulfides in solution.
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https://tel.archives-ouvertes.fr/tel-01897431
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Submitted on : Thursday, November 15, 2018 - 11:07:18 AM
Last modification on : Tuesday, October 6, 2020 - 4:18:02 PM
Long-term archiving on: : Saturday, February 16, 2019 - 12:11:16 PM

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  • HAL Id : tel-01897431, version 1

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Alice Robba. Développement et compréhension des mécanismes électrochimiques des accumulateurs Lithium-ion/Soufre. Energie électrique. Université Grenoble Alpes, 2018. Français. ⟨NNT : 2018GREAI049⟩. ⟨tel-01897431⟩

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