京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第25385号 / 人博第1127号 / 新制||人||262(附属図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 田部 勢津久, 教授 藤原 直樹, 教授 雨澤 浩史 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

<p>There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O₂-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO₄. A second and in some ways even more attractive material - Li₂FeSiO₄ - has emerged during the course of this work.</p><p>An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li₂FeSiO₄. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li₂FeSiO₄ and LiFeSiO₄, but with the structure of the original Li₂FeSiO₄ transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li₂FeSiO₄ and the delithiated on LiFeSiO₄ structure provide an interesting insight into the experimental result.</p><p>Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO₄ and Li₂FeSiO₄ after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling.</p><p>LiFePO₄ and Li₂FeSiO₄ should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.</p>

There are today clear indications that the Li-ion battery of the type currently used worldwide in mobile-phones and lap-tops is also destined to soon become the battery of choice in more energy-demanding concepts such as electric and electric hybrid vehicles (EVs and EHVs). Since the currently used cathode materials (typically of the Li(Ni,Co)O2-type) are too expensive in large-scale applications, these new batteries will have to exploit some much cheaper transition-metal. Ideally, this should be the very cheapest - iron(Fe) - in combination with a graphite(C)-based anode. In this context, the obvious Fe-based active cathode of choice appears to be LiFePO4. A second and in some ways even more attractive material - Li2FeSiO4 - has emerged during the course of this work. An effort has here been made to understand the Li extraction/insertion mechanism on electrochemical cycling of Li2FeSiO4. A fascinating picture has emerged (following a complex combination of Mössbauer, X-ray diffraction and electrochemical studies) in which the material is seen to cycle between Li2FeSiO4 and LiFeSiO4, but with the structure of the original Li2FeSiO4 transforming from a metastable short-range ordered solid-solution into a more stable long-range ordered structure during the first cycle. Density Functional Theory calculations on Li2FeSiO4 and the delithiated on LiFeSiO4 structure provide an interesting insight into the experimental result. Photoelectron spectroscopy was used to study the surface chemistry of both carbon-treated LiFePO4 and Li2FeSiO4 after electrochemical cycling. The surface-layer on both materials was concluded to be very thin and with incomplete coverage, giving the promise of good long-term cycling. LiFePO4 and Li2FeSiO4 should both be seen as highly promising candidates as positive-electrode materials for large-scale Li-ion battery applications.

Les batteries lithium ions sont la technologie de référence pour le stockage électrochimique de l’énergie. Cependant, les matériaux cathodiques de ces batteries comme LiCoO2, LiMn2O4 ou LiFePO4 présentent une capacité spécifique limitée (<160 mAh/g). De nombreux composés sont à l’étude pour améliorer cette performance dont le fluorure de fer (III) en raison de sa capacité théorique de 711 mAh.g-1. Ce travail présentera la synthèse de FeF3 par différentes méthodes de fluoration. Les matériaux obtenus seront comparés en termes de structures et de liaison (DRX, Mössbauer, spectroscopies IR et Raman) mais aussi de texture (isothermes d’adsorption à l’azote à 77K). Les propriétés électrochimiques des matériaux obtenus seront également comparées et testées. Enfin, l’étude du mécanisme électrochimique de cette famille de composés sera menée via une méthode de caractérisation « in operando » : la spectroscopie d’absorption des rayons X (XAS). / The lithium-ion batteries are the current solution for electrochemical energy storage. However, their performances are limited by the cathode materials, such as LiCoO2, LiMn2O4 or LiFePO4 of specific capacity lower than 160 mAh/g. Many materials are good candidates to improve this capacity such as iron trifluoride of theoretical capacity of 711 mAh.g-1. This work will present the synthesis of FeF3 through different fluorination ways. The resulting materials will be characterized owing to their structure by XRD, Mössbauer, Raman and IR spectroscopies and their texture by nitrogen adsorption isotherms at 77K and SEM. After that, the electrochemical properties will be evaluated and compared. Finally, the study of the electrochemical mechanism of this family of compounds will be led with a method of characterization “in operando” : the X-rays absorption spectroscopy (XAS).

This master's thesis deals with a topic of determination of the most suitable ratio of cathode materials for the lithium-sulfur systems. The first two chapters provide a general introduction to the topic of electrochemical energy sources and present the commonly used primary and secondary battery systems with emphasis on their characteristics and applications. The core of the theoretical part is dedicated to lithium-ion and lithium-sulfur batteries, their working principles along with the benefits or drawbacks related to the particular systems, and widely used materials. The experimental part briefly comments on determining the suitable electrode paste preparation method, the subsequent main part is focused on evaluation of electrochemical performance of cells using different ratios of cathode materials. Five samples of cathode materials were prepared, where the sulfur ratio is in range from 64 to 88 wt. %. Finally, the comparison of all prepared ratios in terms of their electrochemical properties is provided.

Die wachsende Weltbevölkerung und die stetigen Entwicklungen in der Industrie benötigen einerseits immer größere Mengen an Grundchemikalien und führen andererseits zu einem ständig steigenden Energiebedarf. Die Dissertation behandelt daher die Themen Zeolithe und Kathodenmaterialien, welche zwei aktuelle Forschungsschwerpunkte der chemischen Industrie darstellen. Der Fokus der Arbeit lag in der Steuerung der Partikelgröße durch die hydrothermale und mikrowellenunterstützte Kristallisation.

<p>Energy storage devices have become an integral part of the digital infrastructure of the 21st century. Li-ion batteries are a widely used chemical form of energy storage devices comprising components with varied chemical, mechanical and electrochemical properties. Over long-term usage, the anode and cathode experience spatially heterogeneous Li reaction, mechanical degradation, and reversible capacity loss. The small particle size and environmental sensitivity of materials used in Li-ion battery materials make investigating electrodes' electrochemical and mechanical properties an arduous task. Nevertheless, understanding the effect of electrochemical fatigue load (during the battery's charging and discharging process) on composite electrodes' mechanical stability is imperative to design and manufacture long-lasting energy storage devices.</p><p>Due to the low-symmetry lattice, Lithium Nickel Manganese Cobalt Oxide (NMC) cathode materials exhibit direction-dependent (anisotropic) mechanical properties. In this Dissertation, we first measure the anisotropic elastic stiffness of NMC cathode material using nano-indentation. We also determine the effect of Ni stoichiometry on the indentation modulus, hardness, and fracture toughness of NMC materials. The complete information on the mechanical properties of cathode materials will enable accurate computational results and the design of robust cathodes.</p><p>Further, using operando optical experiments, we report that NMC porous composite cathode experiences asynchronous reactions only during the 1st charging process. Non-uniform carbon binder network coverage across the cathode and Li concentration-dependent material properties of NMC results in the initial asynchronous phenomenon. The information on the degree of electrochemical conditioning of Li-ion battery cathode obtained from optical microscopy can test the consistency of product quality in the industrial manufacturing process. We also investigate the effects of non-uniform reactions on active material’s local morphology change and study the evolution of particle network over long-term cycling. Reported data from experiments depicts that in the early cycles, individual particles’ characteristics significantly influence the degree of damage across the cathode.</p><p>However, the interaction with neighboring particles becomes more influential in later cycles. Computational modeling uses a multiphysics-based theoretical framework to explain the interplay between electrochemical activity and mechanical damage. The methodology, theoretical framework, and experimental procedure detailed here will enable the design of efficient composite electrodes for long-lasting batteries.</p>

Объектами исследования настоящей работы являются катодные материалы на основе сложного оксида Сa3Co4O9+δ. Цель работы – апробация материалов на основе Сa3Co4O9+δ, которые могут быть использованы в качестве катодов для среднетемпературных твердооксидных топливных элементов с протон-проводящими электролитами BaCe0.5Zr0.3Y0.1Yb0.1O3- и BaCe0.7Zr0.1Y0.1Yb0.1O3-. Методом пиролиза цитрат-солевых композиций проведен синтез сложных оксидов Сa3Co4O9+δ, Ca3Co4-xCuxO9 (х = 0.05; 0.1; 0.15; 0.2), BaCe0.5Zr0.3Y0.1Yb0.1O3-δ и BaCe0.7Zr0.1Y0.1Yb0.1O3-. При помощи комплекса современных методов исследования выполнена фазовая, структурная и микроструктурная аттестация оксидов Сa3Co4O9+δ, Ca3Co4 xCuxO9 (х = 0.05; 0.1; 0.15; 0.2), BaCe0.5Zr0.3Y0.1Yb0.1O3-δ и BaCe0.7Zr0.1Y0.1Yb0.1O3-. Термогравиметрическим методом исследована термическая устойчивость Сa3Co4O9+δ на воздухе и в атмосфере аргона. Термическое расширение оксидов Сa3Co4O9+δ и BaCe0.5Zr0.3Y0.1Yb0.1O3-δ изучено методом дилатометрии, доказана их термическая совместимость. Изучена химическая совместимость оксида Сa3Co4O9+δ с электролитными материалами Ba2In1.8W0.2O5.15, 0.7Ba2In2O5·0.3Ba2InNbO6, Ba3Ca1.18Nb1.82O9 δ, BaCe0.5Zr0.3Y0.1Yb0.1O3 δ, а также материалами коллекторных слоев La0.6Sr0.4MnO3-δ и LaNi0.6Fe0.4О3 δ, установлена оптимальная температура припекания катодного материала Сa3Co4O9+δ к электролиту BaCe0.5Zr0.3Y0.1Yb0.1O3-δ. Исследованы температурные зависимости электропроводности Сa3Co4O9+δ и BaCe0.5Zr0.3Y0.1Yb0.1O3-δ на воздухе. Сформированы электроды на основе композитов с различным массовым содержанием Сa3Co4O9+δ и BaCe0.5Zr0.3Y0.1Yb0.1O3-δ на подложках из BaCe0.5Zr0.3Y0.1Yb0.1O3-δ, а также электроды на основе Ca3Co4-xCuxO9 (х = 0; 0.05; 0.1; 0.15) на подложках из BaCe0.7Zr0.1Y0.1Yb0.1O3-δ. Методом импедансной спектроскопии на симметричных ячейках измерены поляризационные характеристики полученных электродов, а также электродов с оксидным коллектором состава La0.6Sr0.4MnO3-δ+2 масс.% CuO. / The object of study in this work is a cathode material based on the Сa3Co4O9+δ. The aim of the work is to study the electrochemical behavior of electrodes based on the Сa3Co4O9+δ with the electrolyte materials BaCe0.5Zr0.3Y0.1Yb0.1O3- and BaCe0.7Zr0.1Y0.1Yb0.1O3-. The synthesis of the Сa3Co4O9+δ, Ca3Co4-xCuxO9 (х = 0.05; 0.1; 0.15; 0.2), BaCe0.5Zr0.3Y0.1Yb0.1O3-δ and BaCe0.7Zr0.1Y0.1Yb0.1O3- complex oxides was carried out by pyrolysis of citrate-salt compositions. Using a complex of modern research methods, phase, structural and microstructural attestation of the Сa3Co4O9+δ, Ca3Co4-xCuxO9 (х = 0.05; 0.1; 0.15; 0.2), BaCe0.5Zr0.3Y0.1Yb0.1O3-δ and BaCe0.7Zr0.1Y0.1Yb0.1O3- oxides were carried out. The thermal stability of the Сa3Co4O9+δ in air and in the argon atmosphere was studied by the thermo gravimetrical method. The thermal expansion of the Сa3Co4O9+δ and BaCe0.5Zr0.3Y0.1Yb0.1O3-δ oxides was studied by dilatometry, and their thermal compatibility was proved. The chemical compatibility of the Сa3Co4O9+δ oxide with the electrolyte materials Ba2In1.8W0.2O5.15, 0.7Ba2In2O5·0.3Ba2InNbO6, Ba3Ca1.18Nb1.82O9 δ, BaCe0.5Zr0.3Y0.1Yb0.1O3-δ, Lа0.6Sr0.4MnO3-δ and LaNi0.6Fe0.4О3-δ collector materials was studied, the optimal temperature of the cathode material Сa3Co4O9+δ annealing to the BaCe0.5Zr0.3Y0.1Yb0.1O3-δ electrolyte was established. The temperature dependences of the electrical conductivity of the Сa3Co4O9+δ and BaCe0.5Zr0.3Y0.1Yb0.1O3-δ in air were investigated. Electrodes based on composites with different mass contents of Сa3Co4O9+δ and BaCe0.5Zr0.3Y0.1Yb0.1O3-δ on substrates of BaCe0.5Zr0.3Y0.1Yb0.1O3-δ, as well as electrodes based on Ca3Co4-xCuxO9 (х = 0; 0.05; 0.1; 0.15) on substrates of BaCe0.7Zr0.1Y0.1Yb0.1O3  were formed. The polarization characteristics of the obtained electrodes, including those with an La0.6Sr0.4MnO3-δ+2 wt.% CuO oxide collector, were studied by the method of impedance spectroscopy on the symmetric cells.

Nous avons mis au point une approche novatrice pour la synthèse d’un matériau de cathode pour les piles lithium-ion basée sur la décomposition thermique de l’urée. Les hydroxydes de métal mixte (NixMnxCo(1-2x)(OH)2) ont été préparés (x = 0.00 à 0.50) et subséquemment utilisés comme précurseurs à la préparation de l’oxyde de métal mixte (LiNixMnxCo(1-2x)O2). Ces matériaux, ainsi que le phosphate de fer lithié (LiFePO4), sont pressentis comme matériaux de cathode commerciaux pour la prochaine génération de piles lithium-ion. Nous avons également développé un nouveau traitement post-synthèse afin d’améliorer la morphologie des hydroxydes. L’originalité de l’approche basée sur la décomposition thermique de l’urée réside dans l’utilisation inédite des hydroxydes comme précurseurs à la préparation d’oxydes de lithium mixtes par l’intermédiaire d’une technique de précipitation uniforme. De plus, nous proposons de nouvelles techniques de traitement s’adressant aux méthodes de synthèses traditionnelles. Les résultats obtenus par ces deux méthodes sont résumés dans deux articles soumis à des revues scientifiques. Tous les matériaux produits lors de cette recherche ont été analysés par diffraction des rayons X (DRX), microscope électronique à balayage (MEB), analyse thermique gravimétrique (ATG) et ont été caractérisés électrochimiquement. La performance électrochimique (nombre de cycles vs capacité) des matériaux de cathode a été conduite en mode galvanostatique. / We have developed a novel approach to the synthesis of cathode materials for lithium-ion batteries, based on the thermal decomposition of urea. Mixed metal hydroxides (NixMnxCo(1-2x)(OH)2), x = 0.00 to 0.50, were prepared and subsequently used as precursor for lithiated mixed metal oxide (LiNixMnxCo(1-2x)O2). These materials along with lithium iron phosphate (LiFePO4) are being considered as cathode materials for the next generation of lithium-ion batteries. We have also developed new post-synthetic treatments on the hydroxides in order to enhance the morphology, which would result in improved electrode properties. The novelty of this thesis is that for the first time mixed metal hydroxides for use as precursors for lithium mixed oxides have been prepared via a uniform precipitation technique from solution. In addition, we have proposed new treatments techniques towards the more traditional synthesis method for mixed metal hydroxides. The results obtained from these two methods are summarized within two articles that were recently submitted to peer-reviewed journals. Within this thesis, all materials were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and electrochemical measurements. The electrochemical performance (capacity vs cycle number) of the cathode materials were tested galvanostatically.

Nous avons mis au point une approche novatrice pour la synthèse d’un matériau de cathode pour les piles lithium-ion basée sur la décomposition thermique de l’urée. Les hydroxydes de métal mixte (NixMnxCo(1-2x)(OH)2) ont été préparés (x = 0.00 à 0.50) et subséquemment utilisés comme précurseurs à la préparation de l’oxyde de métal mixte (LiNixMnxCo(1-2x)O2). Ces matériaux, ainsi que le phosphate de fer lithié (LiFePO4), sont pressentis comme matériaux de cathode commerciaux pour la prochaine génération de piles lithium-ion. Nous avons également développé un nouveau traitement post-synthèse afin d’améliorer la morphologie des hydroxydes. L’originalité de l’approche basée sur la décomposition thermique de l’urée réside dans l’utilisation inédite des hydroxydes comme précurseurs à la préparation d’oxydes de lithium mixtes par l’intermédiaire d’une technique de précipitation uniforme. De plus, nous proposons de nouvelles techniques de traitement s’adressant aux méthodes de synthèses traditionnelles. Les résultats obtenus par ces deux méthodes sont résumés dans deux articles soumis à des revues scientifiques. Tous les matériaux produits lors de cette recherche ont été analysés par diffraction des rayons X (DRX), microscope électronique à balayage (MEB), analyse thermique gravimétrique (ATG) et ont été caractérisés électrochimiquement. La performance électrochimique (nombre de cycles vs capacité) des matériaux de cathode a été conduite en mode galvanostatique. / We have developed a novel approach to the synthesis of cathode materials for lithium-ion batteries, based on the thermal decomposition of urea. Mixed metal hydroxides (NixMnxCo(1-2x)(OH)2), x = 0.00 to 0.50, were prepared and subsequently used as precursor for lithiated mixed metal oxide (LiNixMnxCo(1-2x)O2). These materials along with lithium iron phosphate (LiFePO4) are being considered as cathode materials for the next generation of lithium-ion batteries. We have also developed new post-synthetic treatments on the hydroxides in order to enhance the morphology, which would result in improved electrode properties. The novelty of this thesis is that for the first time mixed metal hydroxides for use as precursors for lithium mixed oxides have been prepared via a uniform precipitation technique from solution. In addition, we have proposed new treatments techniques towards the more traditional synthesis method for mixed metal hydroxides. The results obtained from these two methods are summarized within two articles that were recently submitted to peer-reviewed journals. Within this thesis, all materials were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and electrochemical measurements. The electrochemical performance (capacity vs cycle number) of the cathode materials were tested galvanostatically.