Este trabalho apresenta um estudo dos mecanismos de transporte iônico nos vidros fluorsilicatos de cádmio e chumbo de composição 40SiO2 40PbF2 20CdF2, e nos vidros boratos contendo LiF de composição 50B2O3 10PbO 40LiF. Estes materiais são importantes pela sua potencial utilização em dispositivos ópticos e eletrólitos sólidos. No vidro borato 50B2O3 10PbO 40LiF o estudo da forma de linha do 7Li mostrou que esta é influenciada tanto por interações dipolares quanto por quadrupolares. O estudo de RMN revelou que há dois F- presentes neste vidro, um deles em vizinhaças de Pb (F- incorporados à rede vítrea substituindo o oxigênio do grupo PbO), e o outro em vizinhanças de Li. A forma de linha de RMN dependente da temperatura para o lítio e para o flúor, e seus tempos de relaxação, exibem as características qualitativas associadas com a alta mobilidade do 7Li e do 19F neste sistema. Este estudo também mostrou que, neste vidro, tanto o Li+ como o F- contribuem para a condutividade medida, sendo que o 7Li é móvel a temperaturas mais baixas (a partir de 250 K), e o 19F começa a se mover em temperaturas mais altas (a partir de 400 K). No vidro 40SiO2 40PbF2 20CdF2, os resultados de RMN mostraram a alta mobilidade do flúor e evidenciaram duas dinâmicas diferentes dos íons flúor. Os dados da relaxação do flúor revelaram um máximo da taxa de relaxação spin-rede abaixo da temperatura de transição vítrea (Tg), indicando que a mobilidade do flúor, neste vidro, é comparável àquelas encontradas em condutores iônicos rápidos / This work presents a study of the ionic transport mechanisms in lead-cadmium fluorosilicate glasses, of composition 40SiO2 40PbF2 20CdF2, and in borate glasses containing LiF, of composition 50B2O3 10PbO 40LiF. These materiais are important due to theirs high potential applicability in optic devices and in solid electrolytes. In the borate glass 50B2O3 10PbO 40LiF, the line shape study of 7Li shows an influence of the dipolar and quadrupolar interactions. The NMR results showed that there are two kinds of F- ions in this glass, one in the Pb vicinity (F- in the glass lattice, in substitution of the PbO oxygen), and the other in the Li vicinity. The NMR line shape depends on the temperature for the 7Li and 19F atoms, and their relaxation times reflect qualitative features related to the high mobility of there nuclei. Also, this study shows that, in this glass, both, 7Li and 19F, play an important role in the electric conductivity. The 7Li is mobile for low temperatures (from 250 K), while the 19F is mobile for high temperatures (from 400 K). In the 40SiO2 40PbF2 20CdF2 glass, the NMR results showed the high mobility of the fluorine ions, indicating two different dynamics of those nuclei. The relaxation data of the 19F presented a spin-lattice relaxation rate maximum below the glass transition temperature (Tg, indicating that the 19F mobility in this glass is comparable to that of rapid ionic conducting glasses

Este trabalho apresenta um estudo dos mecanismos de transporte iônico nos vidros fluorsilicatos de cádmio e chumbo de composição 40SiO2 40PbF2 20CdF2, e nos vidros boratos contendo LiF de composição 50B2O3 10PbO 40LiF. Estes materiais são importantes pela sua potencial utilização em dispositivos ópticos e eletrólitos sólidos. No vidro borato 50B2O3 10PbO 40LiF o estudo da forma de linha do 7Li mostrou que esta é influenciada tanto por interações dipolares quanto por quadrupolares. O estudo de RMN revelou que há dois F- presentes neste vidro, um deles em vizinhaças de Pb (F- incorporados à rede vítrea substituindo o oxigênio do grupo PbO), e o outro em vizinhanças de Li. A forma de linha de RMN dependente da temperatura para o lítio e para o flúor, e seus tempos de relaxação, exibem as características qualitativas associadas com a alta mobilidade do 7Li e do 19F neste sistema. Este estudo também mostrou que, neste vidro, tanto o Li+ como o F- contribuem para a condutividade medida, sendo que o 7Li é móvel a temperaturas mais baixas (a partir de 250 K), e o 19F começa a se mover em temperaturas mais altas (a partir de 400 K). No vidro 40SiO2 40PbF2 20CdF2, os resultados de RMN mostraram a alta mobilidade do flúor e evidenciaram duas dinâmicas diferentes dos íons flúor. Os dados da relaxação do flúor revelaram um máximo da taxa de relaxação spin-rede abaixo da temperatura de transição vítrea (Tg), indicando que a mobilidade do flúor, neste vidro, é comparável àquelas encontradas em condutores iônicos rápidos / This work presents a study of the ionic transport mechanisms in lead-cadmium fluorosilicate glasses, of composition 40SiO2 40PbF2 20CdF2, and in borate glasses containing LiF, of composition 50B2O3 10PbO 40LiF. These materiais are important due to theirs high potential applicability in optic devices and in solid electrolytes. In the borate glass 50B2O3 10PbO 40LiF, the line shape study of 7Li shows an influence of the dipolar and quadrupolar interactions. The NMR results showed that there are two kinds of F- ions in this glass, one in the Pb vicinity (F- in the glass lattice, in substitution of the PbO oxygen), and the other in the Li vicinity. The NMR line shape depends on the temperature for the 7Li and 19F atoms, and their relaxation times reflect qualitative features related to the high mobility of there nuclei. Also, this study shows that, in this glass, both, 7Li and 19F, play an important role in the electric conductivity. The 7Li is mobile for low temperatures (from 250 K), while the 19F is mobile for high temperatures (from 400 K). In the 40SiO2 40PbF2 20CdF2 glass, the NMR results showed the high mobility of the fluorine ions, indicating two different dynamics of those nuclei. The relaxation data of the 19F presented a spin-lattice relaxation rate maximum below the glass transition temperature (Tg, indicating that the 19F mobility in this glass is comparable to that of rapid ionic conducting glasses

Neste trabalho estudamos vários fatores que tem uma forte influência sobre o comportamento da alumina- &#946 &#34, um condutor iônico para íons de sódio com composição 8,85%Na2O+0,75%Li2O+90,40%Al2O3 (% em peso). O papel das impurezas freqüentemente encontradas na alumina-&#945 obtida pelo processo Bayer, tais como cálcio, silício e ferro, é estudado na alumina -&#946 &#34. Dopagem destas impurezas, separadas e em conjunto, na alumina-&#946 &#34 mostram a forte influência que exercem sobre a conversão de fase alumina - &#946 &#8594 &#946 &#34, condutividade iônica, resistência mecânica e microestrutura da alumina-&#946. Os resultados obtidos indicam claramente que a presença simultânea de cálcio e silício tem forte efeito negativo sobre as propriedades da alumina-&#946 &#34, devido à presença de uma nova fase intergranular. A presença simultânea de ferro, cálcio e silício deprimem a formação dessa fase causando um efeito positivo sobre as propriedades da alumina-&#946 &#34. O uso da técnica de redução carbotérmica do hidróxido de alumínio produz uma alumina-&945 com excelentes características para a preparação de alumina-&#946 &#34, que quando comparada à alumina-&#946 &#34 preparada com a alumina Baikowski, mostrou ser superior. A redução carbotérmica reduz consideravelmente os teores de impurificação da alumina pelo sódio, silício, cálcio e ferro, além de produzir uma alumina livre de aglomerados que conduz a uma melhor conversão de fase alumina -&#946 &#8594 &#946 &#34. A alumina obtida através da redução carbotérmica, além de possuir características desejáveis para a preparação da alumina-&#946 &#34, também é própria para outras aplicações especiais / The ionic conductor for sodium ions known as &#946 &#34 alumina with composition 8,85%Na2O+0,75%Li2O+90,40%Al2O3 (% wt), was studied considering the influence of several variables on its ceramic processing. The effect of impurities frequently found on the raw material used for the preparation of this ionic conductor such as silicon, calcium and iron were studied isolated and mixed together on such properties as phase conversion &#946 &#8594 &#946 &#34 - alumina, ionic conductivity, mechanical properties and microstructure. The results of the experiments clearly indicates that calcium and silicon generates a new phase when present simultaneously in the &#946 &#34 - alumina. This new phase, located at the grain boundary, has a strong negative effect on the ionic conductivity addition of iron destroys this new phase improving the properties of the impure material. The carbothermal reduction of the aluminum hydroxide gives a &#945- alumina that is excelent for &#946 &#34 - alumina preparation when compared with Baikowski alumina. The carbothermal reduction decreases the impurification of &#945-alumina as calcium, iron, silicon and sodium and a fine particle size distribution, without aggregates, that makes the phase conversion &#946 &#8594 &#946 &#34 -alumina very efficient due to a better distribution of the Li+ ion. The &#945 - alumina obtained by carbothermal reduction of the aluminum hydroxide is also adequate for others special applications of &#945 - alumina alone

Neste trabalho estudamos vários fatores que tem uma forte influência sobre o comportamento da alumina- &#946 &#34, um condutor iônico para íons de sódio com composição 8,85%Na2O+0,75%Li2O+90,40%Al2O3 (% em peso). O papel das impurezas freqüentemente encontradas na alumina-&#945 obtida pelo processo Bayer, tais como cálcio, silício e ferro, é estudado na alumina -&#946 &#34. Dopagem destas impurezas, separadas e em conjunto, na alumina-&#946 &#34 mostram a forte influência que exercem sobre a conversão de fase alumina - &#946 &#8594 &#946 &#34, condutividade iônica, resistência mecânica e microestrutura da alumina-&#946. Os resultados obtidos indicam claramente que a presença simultânea de cálcio e silício tem forte efeito negativo sobre as propriedades da alumina-&#946 &#34, devido à presença de uma nova fase intergranular. A presença simultânea de ferro, cálcio e silício deprimem a formação dessa fase causando um efeito positivo sobre as propriedades da alumina-&#946 &#34. O uso da técnica de redução carbotérmica do hidróxido de alumínio produz uma alumina-&945 com excelentes características para a preparação de alumina-&#946 &#34, que quando comparada à alumina-&#946 &#34 preparada com a alumina Baikowski, mostrou ser superior. A redução carbotérmica reduz consideravelmente os teores de impurificação da alumina pelo sódio, silício, cálcio e ferro, além de produzir uma alumina livre de aglomerados que conduz a uma melhor conversão de fase alumina -&#946 &#8594 &#946 &#34. A alumina obtida através da redução carbotérmica, além de possuir características desejáveis para a preparação da alumina-&#946 &#34, também é própria para outras aplicações especiais / The ionic conductor for sodium ions known as &#946 &#34 alumina with composition 8,85%Na2O+0,75%Li2O+90,40%Al2O3 (% wt), was studied considering the influence of several variables on its ceramic processing. The effect of impurities frequently found on the raw material used for the preparation of this ionic conductor such as silicon, calcium and iron were studied isolated and mixed together on such properties as phase conversion &#946 &#8594 &#946 &#34 - alumina, ionic conductivity, mechanical properties and microstructure. The results of the experiments clearly indicates that calcium and silicon generates a new phase when present simultaneously in the &#946 &#34 - alumina. This new phase, located at the grain boundary, has a strong negative effect on the ionic conductivity addition of iron destroys this new phase improving the properties of the impure material. The carbothermal reduction of the aluminum hydroxide gives a &#945- alumina that is excelent for &#946 &#34 - alumina preparation when compared with Baikowski alumina. The carbothermal reduction decreases the impurification of &#945-alumina as calcium, iron, silicon and sodium and a fine particle size distribution, without aggregates, that makes the phase conversion &#946 &#8594 &#946 &#34 -alumina very efficient due to a better distribution of the Li+ ion. The &#945 - alumina obtained by carbothermal reduction of the aluminum hydroxide is also adequate for others special applications of &#945 - alumina alone

La2Mo2O9, premier composé de la famille LAMOX, est intéressant pour des applications comme électrolyte dans des piles à combustible car il présente une conductivité ionique élevée. Il a été découvert durant l'investigation du diagramme de phases de La2O3 -MoO3. Cela montre bien le rôle important de l'étude de diagrammes de phase dans la découverte de nouveaux matériaux qui est devenue un objectif majeur de nombreux chimistes du solide. Selon ce concept, les deux diagrammes de phases ternaires La2O3-Nb2O5-WO3 et La2O3-Nb2O5-MoO3 ont été explorés et analysés pour la première fois en utilisant la synthèse par voie solide. Les structures des échantillons obtenus ont été caractérisées par diffraction des rayons X et des neutrons sur poudre et par microscopie électronique en transmission tandis que leurs propriétés électriques ont été testées par spectroscopie d'impédance complexe sur des pastilles frittées.La majorité des zones mono-, bi- et tri-phasées de ces deux diagrammes ont été définies. Plus particulièrement, les structures de deux nouvelles phases La3NbWO10 et La5NbMo2O16 ont été résolues ab-initio. La connaissance des structures des 2 nouveaux composés a permis une meilleure approche du diagramme de phase ternaire. D'une part, la mailleLa3NbWO10 est une sur structure de la maille fluorine(2aF*2aF*2aF) avec un axe c allongé. En considérant la formulation La18Nb6W62O604 (Z = 6), on constate aisément que la structure présente 2 types de défauts:des lacunes anioniques et cationiques sur les sites des atomes d'oxygène et de lanthane. D'autre part, la phaseLa5NbMo2O16 est un isotype du composé Pr5Mo3O16. Sa maille correspond aussi à une surstructure fluorine. Elle cristallise dans un système cubique (a = 11.22 Å) avec le groupe d'espace rare Pn n. Ce composé est prometteur puisqu'il présente une conductivité par les ions oxyde proche de celle de La2Mo2O9 à basse température. / La2Mo2O9, the first compound in the LAMOX family, is interesting for its applications as electrolytes in fuel cells because it presents a high ionic conductivity. It was discovered during the investigation of La2O3 - MoO3phase diagram. That shows the important role of phase diagram study in the discovery of new materials which has become a major objective of many solid chemists.In this concept, two ternary phase diagrams of La2O3-Nb2O5-WO3 and La2O3-Nb2O5-MoO3 were explored and analyzed for the first time using the solid-state synthesis. The structures of the obtained samples were characterized by the powder X-ray and neutron diffraction and by the transmission electronic microscopy. Besides, their electric properties were tested by the complex impedance spectroscopy onsintered pellets.As results, most of the mono-, bi-, tri-phase zones in the title phase diagrams have been defined. Particularly, during the phase-diagram investigation, the structures of two new phases La3NbWO10 and La5NbMo2O16 were ab-initio resolved. Firstly, the La3NbWO10 cell is asuperstructure of a fluorine (2aF*2aF*2aF) with the lengthened c axis. Considering the La18Nb6W62O604(Z = 6) formulation, we can easily note that the structure presents 2 types of defaults: cationic and anionic vacancies. Secondly, the La5NbMo2O16 phase is isotype of Pr5Mo3O16 compound. Its cell is also a fluorine superstruture. It crystallized in a cubic system (a = 11.22Å) with the space group Pn n. The compound is promising because it presents an oxygen conductivity comparable to that of La2Mo2O9 at low temperature.

Silicon (Si) has been considered as a promising negative electrode material for lithium ion batteries (LIBs) because of its high theoretical capacity, low discharge voltage, and low cost. However, the utilization of Si electrode has been hampered by problems such as slow ionic transport, large stress/strain generation, and unstable solid electrolyte interphase (SEI). These problems severely influence the performance and cycle life of Si electrodes. In general, ionic conduction determines the rate performance of the electrode, while electron leakage through the SEI causes electrolyte decomposition and, thus, causes capacity loss. The goal of this thesis research is to design Si electrodes with high current efficiency and durability through a fundamental understanding of the ionic and electronic conduction in Si and its SEI. Multi-scale physical and chemical processes occur in the electrode during charging and discharging. This thesis, thus, focuses on multi-scale modeling, including developing new methods, to help understand these coupled physical and chemical processes. For example, we developed a new method based on ab initio molecular dynamics to study the effects of stress/strain on Li ion transport in amorphous lithiated Si electrodes. This method not only quantitatively shows the effect of stress on ionic transport in amorphous materials, but also uncovers the underlying atomistic mechanisms. However, the origin of ionic conduction in the inorganic components in SEI is different from that in the amorphous Si electrode. To tackle this problem, we developed a model by separating the problem into two scales: 1) atomistic scale: defect physics and transport in individual SEI components with consideration of the environment, e.g., LiF in equilibrium with Si electrode; 2) mesoscopic scale: defect distribution near the heterogeneous interface based on a space charge model. In addition, to help design better artificial SEI, we further demonstrated a theoretical design of multicomponent SEIs by utilizing the synergetic effect found in the natural SEI. We show that the electrical conduction can be optimized by varying the grain size and volume fraction of two phases in the artificial multicomponent SEI.

No description available.

Le facteur clé limitant le déploiement des accumulateurs au lithium métal est dû à la formation de dendrites de lithium métallique à l'anode au cours de la recharge. Une solution consiste à employer un électrolyte solide polymère. Un copolymère à blocs est composé d'un ou plusieurs blocs conducteurs à base de POE (poly(oxyde d'éthylène)), linéaire ou branchée, dopés en sel de lithium (LiTFSI) et de blocs de renforts mécaniques qui idéalement mitigent la croissance dendritique. Ces matériaux ont la particularité de s'auto-assembler en domaines nanométriques. Les interfaces entre les domaines génèrent de bonnes propriétés mécaniques à l'échelle macroscopique tandis que localement la dynamique des chaînes POE demeure élevée, assurant la conduction ionique.Ce travail de thèse porte sur les caractérisations physico-chimiques d'électrolytes copolymères, selon différentes architectures (diblocs, triblocs et étoilées) et de l'optimisation de leurs compositions. Une étude fondamentale des polymères dopés en sel a mis en évidence les principaux mécanismes de transport ionique, ainsi que l'impact des groupes terminaux à faible masse molaire sur la conductivité et la viscosité. Cette étape a permis de sélectionner les meilleurs candidats. L'étude de la stabilité des électrolytes vis-à-vis du lithium a été menée. Après avoir formulé des cathodes, des batteries plastiques ont été assemblées et testées avec succès par cyclages galvanostatiques, en température [40°C-100°C] et à des régimes élevés. Enfin, un prototype de 6 mAh a réalisé plus de 400 cycles à des régimes C/4 et D/2 à 100°C. / The key limiting factor for the deployment of Lithium metal batteries is the formation of lithium dendrites at the anode during recharge. One solution consists in the use of a solid polymer electrolyte. A bloc copolymer is composed of one or several conductive blocks based on PEO (poly(ethylene oxide)), linear or branched, doped with a lithium salt (LiTFSI) and reinforced blocks that ideally mitigate the dendritic growth. These materials can self-organize in nanometric domains. The interfaces between the domains generate sufficient mechanical properties at the macroscopic level whilst, locally, the PEO chain dynamics remain high, ensuring ionic conduction.This thesis deals with physico-chemical characterizations of these copolymer electrolytes, with different architectures (diblock, triblock and star shaped), and the optimization of their composition. A fundamental study of doped polymers highlighted the main mechanisms of ionic transport and the impact of the end groups at low molar mass on conductivity and viscosity. This step enabled a selection of the best candidates to be made. A study of the electrolyte stability with respect to lithium was carried out. After the formulation of cathodes, plastic batteries were assembled and successfully tested by galvanostatic cycling under temperature [40°C-100°C] and high regime. Finally, a 6 mAh prototype realised more than 400 cycles under the regime C/4 and D/2 at 100°C.

En remplaçant l’électrolyte liquide par un solide, les batteries tout-solide massivessont souvent considérées comme une solution aux problèmes de sécurité desbatteries Li-ion actuelles. La récente découverte du matériau Li10GeP2S12 destructure dite LGPS présentant une conductivité ionique équivalente à celles desélectrolytes liquides a réactivé ce domaine de recherche.Dans cette optique, nous avons étudié les matériaux Li10MP2S12 (M=Sn, Si) destructure LGPS, au moyen de diverses caractérisations structurales (DRX,RMN du 31P, spectroscopie Mössbauer …), de propriétés de mobilité/conductionionique (RMN du 7Li, spectroscopie d’impédance) et de propriétés électrochimiques(voltammétrie cyclique, cyclage galvanostatique).Les échantillons commerciaux de Li10SnP2S12 contiennent des impuretés et uneincertitude subsiste sur la composition de la phase de structure LGPS. Lamodélisation des déplacements de RMN du 31P a notamment permis de mettre enévidence l’influence des lithium en site octaédrique adjacents. Les mesuresd’impédance suggèrent une réactivité avec le Li métallique et la voltammétrieconfirme que cette phase est très instable à bas potentiel, excluant son utilisation entant que simple électrolyte dans une batterie tout-solide. Nous proposons qu’il puisseêtre utilisé à la fois comme électrolyte et comme matériau de négative.L’étude préliminaire des matériaux au silicium souligne la difficulté d’obtention dematériau pur de structure LGPS, et conduit à la mise en cause du modèle structuraldit thio-LiSICON. Par ailleurs, elle montre là encore l’instabilité de ces matériauxface au lithium métal. / By replacing the liquid electrolyte by a solid one, solid state batteries are oftenconsidered as a solution to safety issues in current Li-ion batteries. The recentdiscovery of Li10GeP2S12 with so-called LGPS structure, which exhibits an ionicconductivity equivalent to that of liquid electrolytes, has boosted related researchactivities.In this perspective, we studied the Li10MP2S12 (M=Sn, Si) materials with LGPSstructure, using various methods to characterize the structure (XRD, 31P NMR,Mössbauer spectroscopy …), the ionic mobility/conductivity (7Li NMR, Impedancespectroscopy), and the electrochemical properties (cycling voltammetry,galvanostatic cycling) of the material.Commercially available Li10SnP2S12 batches contain impurities and there remains anambiguity in the actual composition of the LGPS type phase. Modelling of the 31PNMR shifts reveals the effect of lithium in neighboring octahedral sites. Impedencemeasurements suggest reactivity with Li metal, and cyclic voltammetry confirms thatthe material is highly unstable at low potential, which excludes its use as a simpleelectrolyte in solid state batteries. We propose that it might be used both as anelectrolyte and as a negative electrode.The preliminary study on silicon based materials highlights difficulties in obtaining apure LGPS-type compound and questions the real nature of the so-calledthio-LiSICON structural model. Besides, it also shows the instability of thesematerials versus lithium metal.