Advancements in Li-ion batteries are needed especially for the development of electric vehicles and stationary energy storage. Prior research has shown mesoscale variations in electrode electronic conductive properties, which can cause capacity loss and uneven electrochemical behavior of Li-ion batteries. A micro-four-line probe (μ4LP) was used to measure electronic conductivity and contact resistance over mm-length scales in that prior work. This work describes improvements to overcome the challenge of unreliable surface contact between theμ4LP and the sample. Ultimately a second generation flexible probe called the micro-radial-surface probe (μ4LP) was designed and produced. The test fixture was also optimized to obtain consistent contact with the new measurement probe and to perform measurements at a lower force. The μ4LP was then used to study the effect of heterogeneity on calendering, which is the compression of electrode films to obtain a uniform thickness and desired porosity. The thickness, electronic conductivity and contact resistance of two cathodes and one anode were measured before and after calendering. The the spatial standard deviation divided by the mean was used as a measure of heterogeneity. The results show variability in conductive properties increased for two of the three samples after calendering, despite the increased uniformity in thickness of the electrodes. This suggests that additional quality control metrics are needed besides thickness to be able to identify uneven degradation and produce longer lasting batteries.

Advancements in Li-ion batteries are needed especially for the development of electric vehicles and stationary energy storage. Prior research has shown mesoscale variations in electrode electronic conductive properties, which can cause capacity loss and uneven electrochemical behavior of Li-ion batteries. A micro-four-line probe (μ4LP) was used to measure electronic conductivity and contact resistance over mm-length scales in that prior work. This work describes improvements to overcome the challenge of unreliable surface contact between theμ4LP and the sample. Ultimately a second generation flexible probe called the micro-radial-surface probe (μ4LP) was designed and produced. The test fixture was also optimized to obtain consistent contact with the new measurement probe and to perform measurements at a lower force. The μ4LP was then used to study the effect of heterogeneity on calendering, which is the compression of electrode films to obtain a uniform thickness and desired porosity. The thickness, electronic conductivity and contact resistance of two cathodes and one anode were measured before and after calendering. The the spatial standard deviation divided by the mean was used as a measure of heterogeneity. The results show variability in conductive properties increased for two of the three samples after calendering, despite the increased uniformity in thickness of the electrodes. This suggests that additional quality control metrics are needed besides thickness to be able to identify uneven degradation and produce longer lasting batteries.

This thesis describes research to understand the relationships between materials, microstructure, transport processes, and battery performance for primary alkaline battery cathodes. Specifically, the effect of various carbon additives, with different physical properties, on electronic transport or conductivity within battery cathodes was investigated. Generally, the electronic conductivity increases with carbon additives that have higher aspect ratios, smaller particle diameters, higher surface areas, and lower bulk densities. Other favorable carbon aspects include more aggregated and elongated carbon domains which permit good particleto-particle contacts. Of the various carbon additives investigated, graphene nanopowder was the best performer. This graphene nanopowder had the smallest particle diameter, highest surface area, and one of the lowest Scott densities of the carbon additives investigated as well as well-connected, interspersed carbon pathways. Notably, a typical effective ionic conductivity is more than 50 times less than the electronic conductivity (5.7 S/m to 300 S/m, respectively) for a high-performance cathode. Thus, alkaline battery cathodes could be redesigned to improve ionic conductivity for optimal performance. This work expanded on previously published work by relating additional carbon-additive material properties--specifically, particle morphology, surface area and Scott density--and their corresponding cathode microstructure to the fundamental transport processes in alkaline battery cathodes.

Next-generation batteries with improved microstructure and performance are on their way to meet the market demands for high-energy and power storage systems. Among different types of batteries, Li-ion batteries remain the best choice for their high energy density and long lifetime. There is a constant but slow improvement in Li-ion batteries by developing new materials and fabrication techniques. However, further improvements are still needed to meet government and industry goals for cost, cycling performance, and cell lifetime. A fundamental understanding of particle-level interactions can shed light on designing new porous electrodes for high-performance batteries. This is a complex problem because electrodes have a multi-component, multi-phase microstructure made through multiple fabrication processes (i.e., mixing, coating, drying, and calendering). Each of these processes can affect the final microstructure (particle and pore locations) differently. This work seeks to understand the porous microstructure evolution of Li-ion electrodes during the drying and calendering fabrication processes by a combination of modeling and experimental approaches. The goal is to understand the mechanisms by which the electrode components and fabrication processes determine the battery microstructure and subsequent cell performance. A multi-phase smoothed particle (MPSP) model has been developed on a publically available simulation platform known as LAMMPS. This model was used to simulate particle-level interactions and predict the mechanical and transport properties of four fabricated electrodes (i.e. a graphite anode and three traditional metal oxide cathodes). One challenge was to include different electrode components and their interactions and relate them to physical properties like density and viscosity that can be measured experimentally. Another challenge was to generate required electrode property data for model validation, which in general was not found in the literature. Therefore, a series of experiments were conducted to provide that information, namely slurry viscosity, electronic conductivity, porosity, tortuosity, elastic modulus, and electrode crosssections. Understanding these properties has value to the battery community independent of their use in this study. The MPSP model helps us explain observed transport heterogeneity after calendering but brings up new questions about the drying process that have not been addressed in previous works. Therefore, the drying fabrication step was studied experimentally in more detail to fill this knowledge gap and explain our simulation results. The MPSP model can also be used as a predictive tool to explore the design space of Li-ion electrodes where conducting the actual experiments is very challenging. For example, the distinct effect of particle size, shape, orientation, and stiffness on electrode transport and mechanical properties are difficult to determine independently, and therefore this model is an ideal tool to understand the effect of these properties. The final model, which is publically available, could be used with adjustments by future workers to test new materials, fabrication processes, or electrode design (e.g., a multi-layered structure).

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24587号 / 工博第5093号 / 新制||工||1975(附属図書館) / 京都大学大学院工学研究科合成・生物化学専攻 / (主査)教授 古川 修平, 教授 生越 友樹, 准教授 堀毛 悟史, 教授 松田 建児 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The goal of this work is to further understand the relationships between porous electrode microstructure and mass transport properties. This understanding allows us to predict and improve cell performance from fundamental principles. The investigated battery systems are the widely used rechargeable Li-ion battery and the non-rechargeable alkaline battery. This work includes three main contributions in the battery field listed below. Direct Measurement of Effective Electronic Transport in Porous Li-ion Electrodes. An accurate assessment of the electronic conductivity of electrodes is necessary for understanding and optimizing battery performance. The bulk electronic conductivity of porous LiCoO2-based cathodes was measured as a function of porosity, pressure, carbon fraction, and the presence of an electrolyte. The measurements were performed by delamination of thin-film electrodes from their aluminum current collectors and by use of a four-line probe. Imaging and Correlating Microstructure To Conductivity. Transport properties of porous electrodes are strongly related to microstructure. An experimental 3D microstructure is needed not only for computation of direct transport properties, but also for a detailed electrode microstructure characterization. This work utilized X-ray tomography and focused ion beam (FIB)/scanning electron microscopy (SEM) to obtain the 3D structures of alkaline battery cathodes. FIB/SEM has the advantage of detecting carbon additives; thus, it was the main tomography tool employed. Additionally, protocols and techniques for acquiring, processing and segmenting series of FIB/SEM images were developed as part of this work. FIB/SEM images were also used to correlate electrodes' microstructure to their respective conductivities for both Li-ion and alkaline batteries. Electrode Microstructure Metrics and the 3D Stochastic Grid Model. A detailed characterization of microstructure was conducted in this work, including characterization of the volume fraction, nearest neighbor probability, domain size distribution, shape factor, and Fourier transform coefficient. These metrics are compared between 2D FIB/SEM, 3D FIB/SEM and X-ray structures. Among those metrics, the first three metrics are used as a basis for SG model parameterization. The 3D stochastic grid (SG) model is based on Monte Carlo techniques, in which a small set of fundamental inter-domain parameters are used to generate structures. This allows us to predict electrode microstructure and its effects on both electronic and ionic properties.

No description available.

Le domaine émergeant de l’électronique imprimée nécessite de nouveaux matériaux peu coûteux et non toxiques pour réaliser de nombreux systèmes tels que des circuits logiques, des capteurs, des affichages, des thermoélectriques ou même du photovoltaïque sur substrat souple. Il s’agit aussi d’optimiser le fonctionnement de couches granulaires de semiconducteurs de type n et p.BiCuOS a été identifié comme un semiconducteur de type p possédant des propriétés intéressantes. Cependant, sa forte sous stoechiométrie en cuivre induit un dopage de type p trop élevé qui nuit à ses propriétés semiconductrices. De plus, comme la plupart des composés à base de chalcogénures, BiCuOS se décompose lors d’un frittage, et ne peut être densifié thermiquement. Dans le but d’optimiser des couches minces de BiCuOS, des solutions doivent ainsi être trouvées pour i) réduire le taux de dopage ; ii) obtenir de bonnes mobilités dans des couche peu denses. De nombreuses substitutions chimiques ont été essayées telles que celle du soufre par l’iode et celle du cuivre par l’argent. Ces substitutions ont permis de réduire fortement le taux de porteurs de charge. D’autre part, nous avons étudié l’effet du greffage de molécules à la surface des grains de semiconducteurs sur la conduction électronique. Des molécules conjuguées (acides téréphtaliques substitués) et des polymères dérivés des polythiophènes ont été adsorbés à la surface d’un semiconducteur modèle de type n, ZnO. L’amélioration du transfert électronique intergranulaire a été expliquée par le saut des électrons au travers de la LUMO de ces molécules.L’élaboration d’encres de particules semiconductrices stabilisées par de telles molécules a permis la fabrication par voie liquide de jonctions diodes p-n ZnO/BiCuOS avec de bonnes performances malgré l’absence de propriétés photovoltaïques. Plus largement, ce travail est une contribution à la mise en forme de nouveaux systèmes d’électronique hybride par voie de chimie douce, dont le développement permettrait la commercialisation de technologies plus respectueuses de l’environnement. / The emerging domain of printed electronics requires new cheap and non-toxic materials for applications such as logic devices, sensors, displays, thermoelectric and photovoltaic devices. It also requires optimizing the conduction in granular semiconductors. BiCuOS has been identified as a promising p-type semiconductor for such applications. However, its high copper under-stoichiometry, induces an important p-type doping, which is detrimental for its use as a photovoltaic absorber. Moreover, like all chalcogenide based materials, it shows a poor chemical stability during sintering, thermal treatment necessary to enhance transport properties. In order to optimize its properties, solutions must be found i) to control the doping content, ii) to obtain good charge carrier mobilities in thin films. On the one hand, we have explored different kinds of substitutions such as iodine for sulfur or silver for copper, which successfully enabled to strongly reduce the charge carrier density. On the other hand, we have studied the effect of grafting conjugated molecules (terephthalic acid and polythiophene derivatives) onto the surface of a model n-type semiconductor (ZnO) to study their effect on the intergranular transport. Electronic transfer improvement occurs by transfer though a lowered energy barrier formed by the LUMO of the molecules. The formulation of optimized inks using these molecules as additives allowed the thin film deposition of p-n diodes formed with ZnO/BiCuOS. Although no photovoltaic effect has been detected yet, the p-n junctions showed high nonlinear properties and are strongly photosensitive. With this work, we have participated to the elaboration of new sulfides and hybrid interfaces systems for the improvement of semiconductor devices. The development of such hybrid electronic devices through soft chemistry method is a valuable step towards the commercialization of sustainable technologies.

No description available.

Cotutelle entre l'Université de Montréal et l'Université catholique de Louvain / Les batteries aux ions lithium (BIL) sont considérées comme la technologie la plus prometteuse en matière de stockage d’énergie. Elles possèdent les plus hautes densités d’énergie connues, permettant la miniaturisation constante des appareils électroniques commercialisés. La recherche dans le domaine des BIL s’est plus récemment tournée vers leur implémentation dans les véhicules électriques, qui nécessitera de plus hautes densités d’énergie et de puissance . Une manière concrète d’augmenter la densité d’énergie d’une BIL est d’en augmenter le voltage de cellule. Pour se faire, la nouvelle génération de batteries sera composée de matériaux d’électrode positive à haut potentiel (tel que LiMn1.5Ni0.5O4 avec un potentiel de 4.7 V vs. Li+ /Li) et de lithium métallique en électrode négative. Néanmoins, l’introduction de ces matériaux d’électrode positive à haut potentiel est limitée par la stabilité électrochimique de l’électrolyte liquide conventionnel, composé d’un sel de lithium et de solvants organiques (typiquement LiPF6 + EC/DEC), qui s’oxyde autour de 4.2 V vs. Li+/Li , . L’utilisation du lithium métallique comme électrode négative est entravée par la nature liquide de l’électrolyte conventionnel, qui n’offre pas assez de résistance mécanique pour empêcher la formation de dendrites de lithium, causant à terme le court-circuit de la batterie. De tels courts-circuits présentent un risque d’incendie car les électrolytes liquides sont composés de solvants organiques inflammables à basse température, posant un sérieux problème de sécurité. Les électrolytes solides, de type céramique ou polymères, sont développés en alternative aux électrolytes liquides. Ils ne contiennent aucun solvant inflammable et sont stables à haute température. Ils constituent l’élément clé d’une nouvelle génération de batteries au lithium dite batteries au lithium tout-solide. Ces dernières sont développées pour répondre à des attentes élevées en termes de sécurité, de stabilité et de haute densité d’énergie. Les électrolytes solides doivent satisfaire un certain nombre d'exigences avant de pouvoir être commercialisés, notamment posséder une conductivité ionique élevée, une large fenêtre de stabilité électrochimique et une conductivité électronique négligeable. Ces propriétés constituent les critères les plus importants à prendre en compte pour la sélection de matériaux d’électrolytes solides. Cependant, on remarque dans la littérature que la majorité des études se concentre sur la conductivité ionique des électrolytes solides, reléguant au second plan l’exploration de leurs stabilité électrochimique et conductivité électronique. La fenêtre de stabilité électrochimique a longtemps été annoncée comme étant très large chez les électrolytes solides céramiques (au moins de 0 à 5 V vs. Li+/Li). Néanmoins, des études plus récentes tendent à démontrer que la valeur de cette fenêtre dépend grandement de la méthode électrochimique utilisée pour la mesurer, et qu’elle est de surcroit souvent surestimée. Dans ce contexte, le premier objectif de cette thèse a été de développer une méthode pertinente pour déterminer la fenêtre de stabilité des électrolytes solides avec précision. Cette méthode a été optimisée et validée sur des électrolytes solides céramiques phare comme Li1.5Al0.5Ge1.5(PO4)3, Li1.3Al0.3Ti1.7(PO4)3 et Li7La3Zr2O12. Quant à la conductivité électronique, elle est rarement étudiée dans les électrolytes solides, qui sont considérés comme isolants électroniques compte tenu de leur large bande interdite. Cela dit, de récentes études à ce sujet prouvent que malgré leur bande interdite, les électrolytes solides peuvent générer de la conductivité électronique par le biais de défauts, et que celle-ci, même faible, peut éventuellement mettre l’électrolyte en échec. Pour cette raison, le second objectif de ce projet de thèse a été d’explorer la formation de défauts dans les électrolytes solides afin de déterminer leur effet sur la génération de conductivité électronique. Pour avoir une vision d’ensemble, les premiers-principes ont été utilisés pour étudier six électrolytes solides largement utilisés notamment LiGe2(PO4)3, LiTi2(PO4)3, Li7La3Zr2O12, et Li3PS4. / Lithium-ion batteries (LIBs) are considered the most promising energy storage technology. LIBs electrode materials have the highest known energy densities, allowing the constant miniaturization of commercial electronic devices. Research in the field of LIBs has more recently turned to their implementation in electric vehicles, which will require higher energy and power densities . A concrete way to increase the energy density of LIBs is to increase the cell voltage. To do so, the new generation of batteries will be composed of high potential positive electrode materials (such as LiMn1.5Ni0.5O4 with a potential of 4.7 V vs. Li+/Li) and metallic lithium in the negative electrode. Nevertheless, the introduction of these high potential positive electrode materials is limited by the electrochemical stability of conventional liquid electrolytes, composed of a lithium salt and organic solvents (LiPF6 + EC/DEC), which gets oxidized around 4.2 V vs. Li+/Li , . The use of metallic lithium as the negative electrode is also hindered by the liquid nature of the conventional electrolyte, which does not offer enough mechanical resistance to prevent the formation of lithium dendrites, ultimately causing a short-circuit of the battery. Such short-circuits are likely to lead to thermal runaway because liquid electrolytes are composed of organic solvents that are flammable at low temperature, posing a serious safety issue. Solid electrolytes, based on ceramics or polymers, are developed as an alternative to liquid electrolytes. They contain no flammable solvents and are stable at high temperatures. They are the key element of a new generation of lithium batteries called all-solid-state lithium batteries. These are developed to meet high expectations in terms of safety, stability and high energy density. Solid electrolytes must satisfy a number of requirements before they can be commercialized, including possessing a high ionic conductivity, a wide electrochemical stability window and negligible electronic conductivity. These properties are the most important criteria to consider when selecting solid electrolyte materials. However, the majority of studies found in the literature focuses on the ionic conductivity of solid electrolytes, overshadowing the exploration of their electrochemical stability and electronic conductivity. The electrochemical stability window has long been reported to be very wide in ceramic solid electrolytes (at least from 0 to 5 V vs. Li+/Li). Nevertheless, more recent studies tend to show that the value of this window depends greatly on the electrochemical method used to measure it, and that it is often overestimated. In this context, the first objective of this thesis was to develop a relevant method to determine the stability window of solid electrolytes with precision. This method was optimized and validated on flagship ceramic solid electrolytes such as Li1.5Al0.5Ge1.5(PO4)3, Li1.3Al0.3Ti1.7(PO4)3 and Li7La3Zr2O12. As for the electronic conductivity, it is scarcely studied in solid electrolytes, which are considered as electronic insulators given their wide band gaps. That being said, more recent studies on this subject proved that despite their band gap, solid electrolytes can generate electronic conductivity through defects, and that electronic conductivity, even if it is weak, can eventually cause the failure of the electrolyte. For this reason, the second objective of this thesis project was to explore the formation of defects in solid electrolytes in order to determine their effect on the generation of electronic conductivity. To get a better overview, first-principles were used to investigate six widely used ceramic solid electrolytes, including LiGe2(PO4)3, LiTi2(PO4)3, Li7La3Zr2O12, and Li3PS4.