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Thèse soutenue

FR
Auteur / Autrice : Chunmei Li
Direction : Dominique Larcher, Peter G. Bruce, Jean-Marie Tarascon
Type : Thèse de doctorat
Discipline(s) : Sciences des matériaux
Date : Soutenance en 2014
Etablissement(s) : Amiens
Ecole(s) doctorale(s) : École doctorale Sciences, technologie et santé (Amiens)
Partenaire(s) de recherche : Laboratoire : Laboratoire de réactivité et chimie des solides (Amiens)
Jury : Examinateurs / Examinatrices : Dominique Larcher, Peter G. Bruce, Jean-Marie Tarascon, Philippe Barboux, Frédéric Favier, Philippe Stevens, Alejandro Antonio Franco
Rapporteurs / Rapporteuses : Philippe Barboux, Frédéric Favier

Mots clés

FR

Mots clés contrôlés

Électrolytes
Batteries lithium-ion

Mots clés libres

Solvatation des ions Li
Anodes de silicium

Résumé

FR  |  
EN

Rechargeable aprotic Li-02 batteries have gained significant attention because of their high theoretical specific energy of 3500 Wh kg(-1). However, there are many challenges relevant to the development of a practical réversible aprotic Li-O2 battery. The main challenges can be divided into two parts. Firstly, stability issues from: 1) Li métal négative electrodes reacting with contamination from the air, such as H2O and CO2, and some electrolytes, and Li dendrite formation ; 2) positive O2 electrode reactions with the discharge product Li202, and oxidation reaction on charging > 3. 5 V ; 3) electrolyte stability towards O2 reduction products or intermediates. Secondly, the poor discharge/charge voltaic efficiency and cycle life problems, which originate from: 1) large overpotentials on discharge and charge; 2) decomposition of cell component during ORR and OER. In order to overcome these challenges, fundamental studies are critical. This thesis focuses on these two main challenges. With regards to stability issues, an alternative negative electrode was studied, where LixSi is used in place of metallic Li in Li-02 batteries. The results suggest that a LixSi electrode is not stable towards to O2. In addition, an investigation of a new electrolyte, 1-methylimidazole (Me-Im) was discussed. When studying the discharge and charge products at the end of each cycle while using a Me-Im based electrolyte, the data suggests that the stability of Me-Im is not sufficient for use in a rechargeable aprotic Li-Oj battery. The poor discharge/charge voltaic efficiency and cycle life issues of the Li-02 battery are in part related to the fundamental processes occurring during reduction at the O2 electrode and an understanding of these would facilitate development of an efficient, reversible Li-02 battery. With this in mind, the mechanism of O2 reduction reaction (ORR) in aprotic solvents has been studied, with emphasis on the effect of solvent donor number (DN). This has resulted in the development of a mechanism for Li202 formation in aprotic electrolytes, which will be described within. Understanding the mechanism of O2 reduction has enabled strategies to be proposed that may overcome the limitations at the O2 electrode of Li-Oi batteries. For example, the introduction of complexing-cations as additives during ORR is suggested, where the complexing-cations provide "positive charge pockets" that interact with the O2 reduced species, resulting in improving the solubility of Li202 and O2 reduction kinetics. This approach has been demonstrated and shown to have a significant effect on the ORR in an aprotic electrolyte.