O presente trabalho utilizou a técnica de automontagem camada-por-camada para produzir eletrodos híbridos de poli(o-metoxianilina) e nanopartículas de pentóxido de vanádio. Foram obtidos filmes acusticamente rígidos, homogêneos com relação à massa depositada e com crescimento linear com o número de bicamadas depositadas. A caracterização eletroquímica foi realizada por voltametria cíclica, onde esse filme apresentou alta capacidade de intercalação/desintercalação de íons lítio e de forma reversível. A capacidade eletroquímica desse filme foi então comparada com filmes automontados de poli(dialildimetilamônio)/V2O5 e polialilamina/V2O5. O filme de Poli(dialildimetilamônio) apresentou um crescimento irregular com dissolução das nanopartículas, o que resultou em uma capacidade eletroquímica extremamente inferior ao filme de poli(o-metoxianilina). O filme de polialilamina apresentou uma deposição mais eficiente de V2O5 que o filme de poli(o-metoxianilina), entretanto essa maior quantidade de pentóxido de vanádio não refletiu em um aumento da capacidade do eletrodo. Os resultados de espectroscopia de impedância eletroquímica mostram que o filme de polialilamina é significativamente mais resistivo que o filme de poli(o-metoxianilina). Essa diminuição da condutividade, associada ao fato de que a poli(o-metoxianilina) também participa do processo de eletrointercalação, explicam seu melhor desempenho frente a intercalação de lítio. A difusão iônica do lítio nos filmes automontados foi estudada por varredura linear a diferentes velocidades, foi observado que o coeficiente de difusão no filme com polialilamina é uma ordem de grandeza menor que no filme de poli(o-metoxianilina). Por fim, o desempenho eletroquímico do filme de poli(o-metoxianilina)/V2O5 foi comparado no eletrólito composto por um líquido iônico hidrofóbico [bis(trifluorometanosulfonil)imideto de 1-butil-2,3-dimetil-imidazólio] com um solvente orgânico convencional (carbonato de propileno). O eletrodo se mostrou estável no líquido iônico, com maior capacidade específica e menor perda de capacidade. O desempenho superior ao eletrólito convencional está relacionado com a natureza iônica do líquido iônico e com a dissolução do filme em carbonato de propileno. Esses resultados, associados com o fato de que o líquido iônico estudado é compatível com ânodos de lítio metálico, indicam cátodos de poli(o-metoxianilina)/V2O5 em eletrólitos de (bis(trifluorometanosulfonil)imideto de 1-butil-2,3-dimetil-imidazólio podem desenvolver baterias de lítio de alta capacidade, durabilidade e segurança. / The present work used layer-by-layer technique to assemble hybrid electrodes of poly(o-methoxyaniline) and vanadium pentoxide nanoparticles. The film obtained was acoustically rigid, with homogeneous mass deposition and linear growth over the bilayer deposition. The electrochemical characterization was performed by cyclic voltammetry and the film showed high capacity for lithium intercalation and high reversibility in the extraction process. This film\'s capacity was compared with self-assembled poly(diallyldimetylammonium)/V2O5 and polyallylamine/V2O5. In the poly(diallyldimetylammonium) film, dissolution of the nanoparticles was observed, which reflected on a very low electrochemical capacity. The deposition of vanadium pentoxide was more efficient in polyallylamine, but even with a higher amount of V2O5, this electrode presented a smaller electrochemical capacity than poly(o-methoxyaniline)/ V2O5. Electrochemical impedance spectroscopy measurements showed that the film with polyallylamine was much more resistive than the film with poly(o-methoxyaniline). The smaller conductivity and the fact that poly(o-methoxyaniline) also participates in the electroinsertion processes explains the higher performance of poly(o-methoxyaniline)/ V2O5 electrode. Linear sweep experiments with different scan rates were performed to study the chemical diffusion of lithium in the layer-by-layer films. It was observed that the diffusion coefficient in the polyallylamine film is ten times smaller than in the poly(o-methoxyaniline) film. The capacity poly(o-methoxyaniline)/V2O5 electrode was also compared in different electrolytes; a hydrophobic ionic liquid [1-butyl- 2,3-dimethyl-imidazolium bis(trifluoromethanesulfonyl)imide] and an organic solvent (propylene carbonate). In ionic liquid the film was stable, had higher capacity and better cyclability, which is related to the ionic nature of the electrolyte and the fact that in propylene carbonate, dissolution of the film was observed. These results, and the possibility of using metallic lithium as anode in [1-butyl-2,3-dimethyl-imidazolium bis(trifluoromethanesulfonyl)imide], indicates the feasibility of using ionic liquids and poly(o-methoxyaniline)/V2O5 cathodes in safe, durable and high performance lithium batteries.

Layered lithium transition-metal oxides (LMOs) are used as the positive electrode material in rechargeable lithium-ion batteries. Because transition metals undergo redox reactions when lithium ions intercalate in and disintercalate from the lattice, the selection and composition of transition metals largely influence the electrochemical performance of LMOs. Recently, a Ni-rich compound, LiNi0.8Co0.1Mn0.1O2 (NCM811), has drawn much attention. It is expected to replace its state-of-the-art cousins, LiCoO2 (LCO) and LiNi1/3Co1/3Mn1/3O2 (NCM111), because of its higher capacity, lower cost, and reduced toxicity. However, the excess Ni, as a transition-metal element in NCM811, can cause structural and cycling instability. Starting from NCM811, I modified the composition of transition metals by two approaches: 1) introducing cobalt deficiency and 2) substituting Ni, Co, and Mn with Zr. Their influences on the phase, structure, cycling performance, rate capability, and ionic transport were investigated by a variety of characterization techniques. I found that cobalt non-stoichiometry can suppress Ni2+/Li+ cation mixing, but simultaneously promotes the formation of oxygen vacancies, leading to rapid capacity fade and inferior rate capability compared to pristine NCM811. On the other hand, Zr can reside on and expand the lattice of NCM811, and form Li-rich lithium zirconates on their surfaces. In particular, 1% Zr substitution can increase the stability of NCM811 and facilitate Li-ion transport, resulting in enhanced cycling durability and high-rate performance. My studies help improve the understanding of the effects of transition metals on the degradation of the Ni-rich layered positive electrode material and provide modification strategies to enhance its performance and durability for Li-ion battery applications.

Les trois grands domaines d'application de batteries au plomb sont les batteries de démarrage, les batteries de traction et les batteries stationnaires. Les évolutions des marchés, notamment celui de l'énergie, ouvrent de nouvelles applications de stockage par accumulateur au plomb: transports électriques, énergies renouvelables dont éolien et photovoltaïque, stockage réseau, qualité, secours. Dans la plupart des cas, les contraintes de l'application mènent à revoir profondément les algorithmes de charge. Nous avons mené différentes études sur les batteries au plomb dans des conditions extrêmes: charge rapide pour batteries ouvertes, maintien en charge pour batteries stationnaires, décharge profonde avec inversion de polarité. À partir de ces travaux, un nouvel algorithme de charge rapide avec une phase de déstratification précoce a été mis au point. De plus, une nouvelle méthode de maintien en charge par faible courant imposé a été testée sur différentes technologies de batteries au plomb. Elle montre plusieurs avantages en termes de réduction importante de la corrosion, de diminution de la perte d'eau due à la corrosion et de besoin de charges périodiques.

Des matériaux d'électrode positive pour batteries Li-ion de formule Li(Ni,M)O2 (M = Al, Co/Al et Mn) ont été synthétisés par coprécipitation, puis caractérisés par diffraction des rayons X et des neutrons, par des mesures magnétiques et des tests galvanostatiques. La dégradation thermique des phases désintercalées Lix(Ni,M)O2 (M = Al, Co/Al et Mn, x = 0.50 et 0.30) a ensuite été étudiée par analyses thermogravimétriques couplées à la spectrométrie de masse, corrélées à des expériences de diffraction des rayons X in situ, afin d'en déterminer le mécanisme et d'expliquer les différences de stabilité observées suivant la composition des matériaux. Pour tous les composés étudiés, la dégradation se déroule en deux étapes, correspondant à la transition de la phase lamellaire initiale de type α-NaFeO2 en une phase “ LiM2O4 ” de type pseudo-spinelle qui se transforme ensuite, à plus haute température, en une phase dérivant de NiO. L'influence de la nature de l'élément substituant a été discutée.

Ce travail concerne la recherche et le développement de nouveaux matériaux à base d'étain, pour une application comme électrode négative des batteries rechargeables lithium ion. Afin de comprendre la relation Structure-texture-propriétés permettant d'optimiser le matériau, un ensemble de techniques de caractérisation complémentaires (Diffraction des rayons X, Microscopie électronique à balayage, analyse thermiques et gravimétriques ATD-ATG, spectroscopie Mössbauer de 119Sn et absorption X) ont été associées pour caractériser l'ordre global et l'ordre local dans le matériau. Une analyse détaillée du mécanisme de fonctionnement du matériau composite [Sn-BPO4], réalisée en couplant des méthodes électrochimiques et spectroscopiques, a permis de comprendre la réversibilité du système et de mettre en évidence les intermédiaires réactionnels grâce notamment à la spectroscopie Mössbauer in situ de 119Sn. Le matériau composite testé dans des cellules de laboratoire, montre des caractéristiques électrochimiques intéressantes, une capacité massique de 500 mAh/g et une bonne tenue en cyclage. Ces performances sont liées fortement à la meilleure dispersion de l'élément électroactif et à un solide accrochage à la surface de la matrice grâce à une interface amorphe formée entre les deux composants. Le matériau optimisé a été testé dans des conditions industrielle proposées par la société SAFT-Bordeaux, dans le but d'étudier l'effet de la technologie d'électrode sur les performances électrochimiques

Etude des systèmes AgI-Ag₂S-As₂S₃, Ag₂S-AgPO₃ et TlnY-AgPO₃ (Y = I, S). Les propriétés thermiques, chimiques, électriques sont étudiées. Les corrélations entre ces propriétés et la structure déterminée par spectroscopie infrarouge ont été établies. Les potentialités d'applications de ces nouveaux électrolytes ont été étudiés.

<p>The present thesis is concerned to the application of first-principles self-consistent total-energy calculations within the density functional theory on different topics in materials science.</p><p>Crystallographic phase-transitions under high-pressure has been study for TiO2, FeI2, Fe3O4, Ti, the heavy alkali metals Cs and Rb, and C3N4. A new high-pressure polymorph of TiO2 has been discovered, this new polymorph has an orthorhombic OI (Pbca) crystal structure, which is predicted theoretically for the pressure range 50 to 100 GPa. Also, the crystal structures of Cs and Rb metals have been studied under high compressions. Our results confirm the recent high-pressure experimental observations of new complex crystal structures for the Cs-III and Rb-III phases. Thus, it is now certain that the famous isostructural phase transition in Cs is rather a new crystallographic phase transition.</p><p>The elastic properties of the new superconductor MgB2 and Al-doped MgB2 have been investigated. Values of all independent elastic constants (c11, c12, c13, c33, and c55) as well as bulk moduli in the a and c directions (Ba and Bc respectively) are predicted. Our analysis suggests that the high anisotropy of the calculated elastic moduli is a strong indication that MgB2 should be rather brittle. Al doping decreases the elastic anisotropy of MgB2 in the a and c directions, but, it will not change the brittle behaviour of the material considerably.</p><p>The three most relevant battery properties, namely average voltage, energy density and specific energy, as well as the electronic structure of the Li/LixMPO4 systems, where M is either Fe, Mn, or Co have been calculated. The mixing between Fe and Mn in these materials is also examined. Our calculated values for these properties are in good agreement with recent experimental values. Further insight is gained from the electronic density of states of these materials, through which conclusions about the physical properties of the various phases are made.</p><p>The electronic and magnetic properties of the dilute magnetic semiconductor Mn-doped ZnO has been calculated. We have found that for an Mn concentration of 5.6%, the ferromagnetic configuration is energetically stable in comparison to the antiferromgnetic one. A half-metallic electronic structure is calculated by the GGA approximation, where Mn ions are in a divalent state leading to a total magnetic moment of 5 μB per Mn atom.</p>

Many material properties depend on specific details of microstructure and both optimal material performance and material reliability often correlate directly to microstructure. In nano- and micro-systems, the material's microstructure has a characteristic length scale that approaches that of the device in which it is used. Fundamental understanding and prediction of material behavior in nano- and micro-systems depend critically on methods for computing the effect of microstructure. Methods for including the physics and spatial attributes of microstructures are presented for a number of materials applications in devices. The research in our group includes applications of computation of macroscopic response of material microstructures, the development of methods for calculating microstructural evolution, and the morphological stability of structures. In this review, research highlights are presented for particular methods for computing the response in: 1) rechargeable lithium ion battery microstructures, 2) photonic composites with anisotropic particulate morphologies, 3) crack deflection in partially devitrified metallic glasses. / Singapore-MIT Alliance (SMA)

Conventional energy sources are diminishing and non-renewable, take million years to form and cause environmental degradation. In the 21st century, we have to aim at achieving sustainable, environmentally friendly and cheap energy supply by employing renewable energy technologies associated with portable energy storage devices. Lithium-ion batteries can repeatedly generate clean energy from stored materials and convert reversely electric into chemical energy. The performance of lithium-ion batteries depends intimately on the properties of their materials. Presently used battery electrodes are expensive to be produced; they offer limited energy storage possibility and are unsafe to be used in larger dimensions restraining the diversity of application, especially in hybrid electric vehicles (HEVs) and electric vehicles (EVs). This thesis presents a major progress in the development of LiFePO4 as a cathode material for lithium-ion batteries. Using simple procedure, a completely novel morphology has been synthesized (mesocrystals of LiFePO4) and excellent electrochemical behavior was recorded (nanostructured LiFePO4). The newly developed reactions for synthesis of LiFePO4 are single-step processes and are taking place in an autoclave at significantly lower temperature (200 deg. C) compared to the conventional solid-state method (multi-step and up to 800 deg. C). The use of inexpensive environmentally benign precursors offers a green manufacturing approach for a large scale production. These newly developed experimental procedures can also be extended to other phospho-olivine materials, such as LiCoPO4 and LiMnPO4. The material with the best electrochemical behavior (nanostructured LiFePO4 with carbon coating) was able to delive a stable 94% of the theoretically known capacity. / Konventionelle Energiequellen sind weder nachwachsend und daher nachhaltig nutzbar, noch weiterhin langfristig verfügbar. Sie benötigen Millionen von Jahren um gebildet zu werden und verursachen in ihrer Nutzung negative Umwelteinflüsse wie starke Treibhausgasemissionen. Im 21sten Jahrhundert ist es unser Ziel nachhaltige und umweltfreundliche, sowie möglichst preisgünstige Energiequellen zu erschließen und nutzen. Neuartige Technologien assoziiert mit transportablen Energiespeichersystemen spielen dabei in unserer mobilen Welt eine große Rolle. Li-Ionen Batterien sind in der Lage wiederholt Energie aus entsprechenden Prozessen nutzbar zu machen, indem sie reversibel chemische in elektrische Energie umwandeln. Die Leistung von Li-Ionen Batterien hängen sehr stark von den verwendeten Funktionsmaterialien ab. Aktuell verwendete Elektrodenmaterialien haben hohe Produktionskosten, verfügen über limitierte Energiespeichekapazitäten und sind teilweise gefährlich in der Nutzung für größere Bauteile. Dies beschränkt die Anwendungsmöglichkeiten der Technologie insbesondere im Gebiet der hybriden Fahrzeugantriebe. Die vorliegende Dissertation beschreibt bedeutende Fortschritte in der Entwicklung von LiFePO4 als Kathodenmaterial für Li-Ionen Batterien. Mithilfe einfacher Syntheseprozeduren konnten eine vollkommen neue Morphologie (mesokristallines LiFePo4) sowie ein nanostrukturiertes Material mit exzellenten elektrochemischen Eigenschaften hergestellt werden. Die neu entwickelten Verfahren zur Synthese von LiFePo4 sind einschrittig und bei signifikant niedrigeren Temperaturen im Vergleich zu konventionellen Methoden. Die Verwendung von preisgünstigen und umweltfreundlichen Ausgangsstoffen stellt einen grünen Herstellungsweg für die large scale Synthese dar. Mittels des neuen Synthesekonzepts konnte meso- und nanostrukturiertes LiFe PO4 generiert werden. Die Methode ist allerdings auch auf andere phospho-olivin Materialien (LiCoPO4, LiMnPO4) anwendbar. Batterietests der besten Materialien (nanostrukturiertes LiFePO4 mit Kohlenstoffnanobeschichtung) ergeben eine mögliche Energiespeicherung von 94%.

Ein viel diskutiertes Thema unserer Zeit ist die Zukunft der Energiegewinnung und Speicherung. Dabei nimmt die Nanowissenschaft eine bedeutende Rolle ein; sie führt zu einer Effizienzsteigerung bei der Speicherung und Gewinnung durch bereits bekannte Materialien und durch neue Materialien. In diesem Zusammenhang ist die Chemie Wegbereiter für Nanomaterialien. Allerdings führen bisher die meisten bekannten Synthesen von Nanopartikeln zu undefinierten Partikeln. Eine einfache, kostengünstige und sichere Synthese würde die Möglichkeit einer breiten Anwendung und Skalierbarkeit bieten. In dieser Arbeit soll daher die Darstellung der einfachen Synthese von Mangannitrid-, Aluminiumnitrid-, Lithiummangansilicat-, Zirkonium-oxinitrid- und Mangancarbonatnanopartikel betrachtet werden. Dabei werden die sogenannte Harnstoff-Glas-Route als eine Festphasensynthese und die Solvothermalsynthese als typische Flüssigphasensynthese eingesetzt. Beide Synthesewege führen zu definierten Partikelgrößen und interessanten Morphologien und ermöglichen eine Einflussnahme auf die Produkte. Im Falle der Synthese der Mangannitridnanopartikel mithilfe der Harnstoff-Glas-Route führt diese zu Nanopartikeln mit Kern-Hülle-Struktur, deren Einsatz als Konversionsmaterial erstmalig vorgestellt wird. Mit dem Ziel einer leichteren Anwendung von Nanopartikeln wird eine einfache Beschichtung von Oberflächen mit Nanopartikeln mithilfe der Rotationsbeschichtung beschrieben. Es entstand ein Gemisch aus MnN0,43/MnO-Nanopartikeln, eingebettet in einem Kohlenstofffilm, dessen Untersuchung als Konversionsmaterial hohe spezifische Kapazitäten (811 mAh/g) zeigt, die die von dem konventionellen Anodenmaterial Graphit (372 mAh/g) übersteigt. Neben der Synthese des Anodenmaterials wurde ebenfalls die des Kathodenmaterials Li2MnSiO4-Nanopartikeln mithilfe der Harnstoff-Glas-Route vorgestellt. Mithilfe der Synthese von Zirkoniumoxinitridnanopartikeln Zr2ON2 kann eine einfache Einflussnahme auf das gewünschte Produkt durch die Variation derReaktionsbedingungen, wie Harnstoffmenge oder Reaktionstemperatur, bei der Harnstoff-Glas-Route demonstriert werden. Der Zusatz von kleinsten Mengen an Ammoniumchlorid vermeidet, dass sich Kohlenstoff im Endprodukt bildet und führt so zu gelben Zr2ON2-Nanopartikeln mit einer Größe d = 8 nm, die Halbleitereigen-schaften besitzen. Die Synthese von Aluminiumnitridnanopartikeln führt zu kristallinen Nanopartikeln, die in eine amorphe Matrix eingebettet sind. Die Solvothermalsynthese von Mangancarbonatnanopartikel lässt neue Morphologien in Form von Nanostäbchen entstehen, die zu schuppenartigen sphärischen Überstrukturen agglomeriert sind. / The development of new methods toward alternative clean energy production and efficient energy storage is a hot topic nowadays. In this context nanoscience has an important role to find suitable ways of increasing the efficiency of storage and production of energy of already known materials and new materials. However, until now the most well-known syntheses of MnN0,43 and Zr2ON2 nanoparticles lead to undefined particles. A simple, cheap and safe synthesis would offer the possibility of broader applications and scalability. We herein present the so-called urea-glass route which is used as a sol-gel process. This synthetic route leads to well-defined particle sizes, novel particle morphologies and allows the tailoring of the desired products. In the case of the synthesis of manganese nitride nanoparticles (MnN0,43), nanoparticles with a core-shell structure are obtained, their use as conversion materials in batteries is first introduced. On the other hand, the formation of zirconium oxynitride nanoparticles (Zr2ON2) can be easily influenced by varying the reaction conditions such as the amount of urea or the reaction temperature. The addition of small amounts of salt prevents the formation of carbon in the final product, leading to yellow Zr2ON2 nanoparticles with a size of d = 8 nm which show semiconductor behavior.