京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20581号 / 工博第4361号 / 新制||工||1678(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24633号 / 工博第5139号 / 新制||工||1982(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 阿部 竜, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

京都大学 / 新制・課程博士 / 博士(エネルギー科学) / 甲第24713号 / エネ博第456号 / 新制||エネ||85(附属図書館) / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 野平 俊之, 教授 萩原 理加, 教授 佐川 尚 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling. Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling. The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied. Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles. Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour. Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.

Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling. Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling. The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied. Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles. Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour. Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.

Dans ce travail nous avons réalisé la synthèse de nitrures structure 2D Li3-2xCoxN et de structure 3D Li7MnN4 par méthode céramique, sous atmosphère contrôlée. Après avoir acquis la maîtrise des paramètres de synthèse, nous réalisons la caractérisation structurale et l'étude des propriétés électrochimiques de chaque matériau (capacité spécifique, rechargeabilité…). Dans le cas des matériaux 2D, des affinements par la méthode de Rietveld nous ont permis de déterminer précisément les formules de ces composés. Une étude par spectroscopie diélectrique met en évidence la présence d'une faible proportion de Co+ parmi les Co2+ à l'origine de propriétés de conduction électronique. Nous montrons pour une étude DRX in-operando que le volume de maille ne varie que de 1,5% lors de d'un cycle expliquant la stabilité des capacités de 180mAh g-1 à 300 mAh g-1 selon les conditions. Dans le cas des matériaux 3D, Li7MnN4 a montré les meilleures performances avec des capacités réversibles jusqu' 300mAh g-1. Une étude DRX in-operando a montré que le mécanisme de désinsertion du lithium se déroulé en deux biphasage et une étape de solution solide. Une optimisation des performances est possible en réduisant la taille des particules par mécanobroyage : des capacités de 250 et 120 mAh g-1 sont obtenus à régime C et 5c. L'ensemble de ces nitrures présentent une forte réactivité avec l'humidité mais leur structure a pu être préservée sous air sec / In this study, we focus on the synthesis of nitrides with 2D structure Li3-2xCoxN and 3D structure Li7MnN4 by solid state route, under controlled atmosphere. Once we master all parameters of the synthesis, we study the structural chracterization and the electrochemical properties of each compound (specific capacity, rechargeability...) In the case of 2D compounds, precises compositions were determined by Rietveld refinement A dielectric spectroscopy study demonstrate the existance of a small populations of Co+ ions among Co2+, which lead to electronic conductivity properties. By in-operando XRD study we show the lattice volume varies by only 1,5% which explains the stabilty of the specific capacity of 180mAh g-1 à 300 mAh g-1 depending on conditions. In the case of 3D compounds, Li7MnN4 showed the best performance with reversible capacities up to 300mAh g-1. A XRD in-operando study showed that the mechanism of lithium desintertion place in two biphasage and a solid solution phase. Performance optimization is possible by reducing the particle size by ball milling: capacities of 250 and 120 mAh g-1 are obtained at C and 5C rates. All these nitrides present a high reactivity with moisture but the structure was preserved in dry air

Ce mémoire est consacré à l'étude théorique des matériaux de cathode pour batteries Li-ion de structure olivine LiMPO4 (M=Mn, Fe, Co, Ni), des phases délithiées MPO4 et des phases mixtes LiFexMn1-xPO4, FexMn1-xPO4 et LiFexCo1-xPO4. La stabilité des phases magnétiques et les paramètres de maille théoriques ont été déterminés par la méthode des pseudopotentiels et comparés aux données expérimentales. Les structures électroniques ont été calculées par une méthode « tout électron » et analysées en termes d'hybridation des orbitales atomiques Ces résultats ont permis d'interpréter les spectres de photoélectrons X et d'absorption des rayons X, en particulier les modifications réversibles associées aux cycles de lithiation/délithiation. Les effets de la polarisation de spin et de la corrélation électronique ont été discutés. Enfin, le calcul des paramètres Mössbauer du 57Fe a montré qu'un accord quantitatif entre les résultats théoriques et les données expérimentales nécessitait la prise en compte de ces deux effets. Ce type de calcul a permis de prédire et d'expliquer que la transformation LiFePO4FePO4 s'accompagnait de la variation du gradient de champ électrique Vzz d'une extrémité à l'autre de l'échelle Mössbauer pour 57Fe. / This thesis is devoted to the theoretical study of the cathode materials for Li-ion batteries with olivine structure LiMPO4 (M=Mn, Fe, Co, Ni), the delithiated phases MPO4 and the mixed phases LiFexMn1-xPO4, FexMn1-xPO4 and LiFexCo1-xPO4. The magnetic phase stability and lattice parameters were theoretically determined from pseudopotential calculations and the results have been compared with experiments. Electronic structures were obtained from all electron calculations and analyzed in terms of orbital hybridization. The results have been used for the interpretation of X-ray photoemission and X-ray absorption spectra, especially changes due to lithiation/delithiation cycles. Effects of spin polarization and electronic correlation on the electronic structures have been also discussed. It has been shown that ab initio calculations of the 57Fe Mössbauer parameters also require these two effects in order to obtain a quantitative agreement with experiments. Finally, it was found that LiFePO4FePO4 transformation involves a dramatic change of the electric field gradient VZZ from one end to the other of the 57Fe Mössbauer scale.

Masters Thesis summarizes the theoretical findings about lithium-ion akumulators. It gives a overview of the basic types of galvanic cells, then deals in detail with the lithium-on cell. It's composition, electrochemical principle of working, thermal dependence, construction and area of application. The thesis describes the basic methods of measuring lithium-on cells, such as cyclic charging and discharging, cyclic voltammetry. The practical part compares selected types of materials for negative elektrodes in different temperatures.

This master´s thesis deals with electrodes for lithium-ions batteries based on LiCoO2. The first part of the project is devoted to the characteristics of Li-ion batteries, electrochemical reactions and characteristics of electrode materials. The next part describes an experiment that deals with the effects of NA doping on performance of layered materials for lithium secondary batteries. The materials were measured by cyclic voltammetry, impedance spectroscopy and galvanostatic cycling.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24108号 / 工博第5030号 / 新制||工||1785(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM