To combat climate change, governments have pledged to become more dependent on renewable electricity production. However, the intermittency of renewable power generation requires modern grid-scale energy storage systems, which are currently being explored with lithium-ion batteries (LIBs). However, this technology faces significant safety, social, and financial concerns. As an alternative chemistry, aqueous zinc-ion batteries (ZIBs) show much promise for grid-scale energy storage with their safe, inexpensive design. Major bottlenecks of ZIB performance include their limited practical specific capacity, and low capacity retention. Organic cathodes, specifically the use of redox-active quinone molecules, are an upcoming contender for customizable and simple ZIB cathode design that can be optimized for good performance. However, these cathodes are often plagued by capacity fade caused by quinone dissolution and inactivation. Grafting these quinone molecules to the supporting conductive carbon substrate via covalent bonding had been previously explored in LIB and supercapacitor electrode design as an effective way to mitigate capacity fade. In this work, the development of aqueous ZIB cathodes with 9,10-phenanthrenequinone (PQ) molecules grafted to carbon black substrates was done via a facile in-situ generated diazonium salt reaction synthesis technique. Electrochemical and material analysis confirmed the presence of covalent grafting. This grafting modification was compared to the standard cathode design of adsorbing the quinones on carbon substrates like Ketjenblack (KB) and Vulcan Black (VB). Battery cycling tests were performed and the grafted PQ-KB cells achieved a discharge capacity of 99 mAh g-1 after 1000 charge-discharge cycles with accelerated testing at a charge/discharge rate of 200 mA g-1 and 10 mA g-1. These cells maintained 67% of their initial capacity compared to the 55% for the adsorbed PQ on KB cells. This approach highlights the promise of grafting organic material as a technique to support organic cathodes for next-generation ZIB design. / Thesis / Master of Applied Science (MASc) / Renewable electricity production is necessary to mitigate climate change but the production of electricity through many renewables like wind and solar can vary significantly on any given day. Lithium-ion batteries are being explored for storing electricity for use on the grid, but they have many downsides including being flammable and expensive. Zinc-ion batteries are non-flammable and cost-effective alternatives to lithium-ion batteries. They are currently not as widely used as lithium-ion batteries because of their poorer performance. However, for storing electricity for power grids, with the correct selection of materials to make the battery, zinc-ion batteries can perform well enough to compete with lithium-ion batteries. This work investigates a modification of a material used in zinc-ion batteries, that allows the battery to maintain a higher capacity after many charge and discharge cycles.

This dissertation examined the relationships between color contrast and legibility for digital raster video imagery. CIE colorimetric components were combined into three-dimensional color coordinate systems whose coordinates map one-to-one with the physical energy parameters of all colors. The distance between any two colors' coordinates in these 3-spaces is termed Color-Difference (ΔE). ΔE was hypothesized as a metric of the speed (RS) with which observers possessing normal vision could accurately read random numeral strings of one color displayed against backgrounds of another color. Two studies totaling 32064 practice and experimental trials were conducted. The first study determined that the CIE Uniform Color Spaces are inappropriate for the modeling of RS. Subsequently, a different 3-space geometry and colorimetric component scaling were empirically derived from the Study 1 data to produce a one-dimensional ΔE scale which ” approximates an interval scale of RS. This ΔE scale and others were then applied to the different stimulus conditions in Study 2 to determine the generalizability of such ΔE metrics. The pair of studies is conclusive: several ΔE scales exist which serve equally well to describe or prescribe RS with multicolor CRT raster imagery for a range of character luminances in both positive and negative presentation polarities. These are the Y,u',v', logY,u',v', L*,u',v', and L*,u*,v* rescaled color spaces. Because of its predictive accuracy and simplicity, a luminance—generalized, ΔE—standardized Y,u',v' metric, accounting for 71% and 75% of the RS variability in Studies 1 and 2, respectively, is recommended as the most appropriate metric of emissive display legibility to be tested in these studies. / Ph. D.

This thesis investigates the lithium-ion dynamics and structural changes in the novel cathode material LiFeV2O7 by solid-state NMR spectroscopy and density functional theory (DFT). With the escalating demand for high-performance lithium-ion batteries (LIBs), exploring cathode materials that can offer superior energy density, cycle stability, and safety is crucial. LiFeV2O7 presents a fascinating structure because it incorporates two transition metals capable of undergoing redox processes, a feature highly beneficial for lithium-ion batteries. The research employs advanced DFT calculations to predict the electronic structure and 7Li NMR shifts. These theoretical insights are essential for understanding how structural disorder influences NMR results and how the oxidation state of transition metal impacts the Fermi contact shift. Experimental techniques, including solid-state NMR spectroscopy and diffraction methods, are applied to study the lithium-ion exchange process and structural evolution during electrochemical cycling. Selective inversion NMR experiments were used to quantify the exchange rates relative to lithiation levels, and in combination with diffraction methods and DFT calculations, enabled the development of a structure model that elucidates the corresponding phase changes in the material. Moreover, the thesis discusses the impact of structural modifications on the lithium-ion dynamics within Li1.71FeV2O7, revealing a direct link between specific crystallographic changes and enhanced lithium mobility. The integration of DFT calculations with experimental observations provides a comprehensive understanding of the material's behavior, paving the way for improvements in cathode design. Overall, this research contributes significantly to the field of LIBs, offering novel insights into the complex interplay between structure, dynamics, and electrochemical performance in cathode materials. / Thesis / Doctor of Science (PhD) / This thesis explores the lithium-ion dynamics and structural changes in the new cathode material LiFeV2O7 using solid-state NMR spectroscopy and density functional theory (DFT). As the demand for high-performance lithium-ion batteries (LIBs) grows, discovering cathode materials with better energy density, stability, and safety becomes crucial. LiFeV2O7 is particularly interesting due to its structure, which includes two transition metals that undergo redox processes. This study combines advanced DFT calculations with experimental techniques to understand how structural disorder and the oxidation state of transition metals affect NMR results. Solid-state NMR spectroscopy and diffraction methods are used to examine lithium-ion exchange and structural changes during battery cycling. The research identifies how specific crystallographic changes enhance lithium mobility, providing insights that can improve cathode design. This comprehensive study contributes to the development of more efficient and stable LIBs by revealing the complex interplay between structure, dynamics, and electrochemical performance.

Lithium-ion batteries have become a vital part of our modern life and play an essential role in electric vehicle development. One of the most feasible strategies to enhance the energy density of Li-ion batteries is to use layered, Ni-rich cathode materials. However, higher nickel content causes several problems and therefore, several methods, including doping and coating, have been utilized to stabilize their structure and boost their performance. This thesis aims to understand the microstructure of such engineered complex cathodes and provide valuable contributions by comprehensively understanding and establishing a link between the composition, structure, performance, and properties of these complex materials. In this regard, the most advanced electron- and photon-based techniques have been used to uncover the fundamental underlying reasons for the enhanced performance or degradation in these complex cathode structures. This study shows that introducing W cation inside the LiNiO2 results in new W-variants with a heterogeneous concentration on the top surface and through grain boundaries of the host secondary particles. These W-rich regions play a reinforcing role in grain boundaries and protect the outer surface of LiNiO2 particles. However, synthesis defects, such as porosities, could reduce these benefits by increasing the electrolyte infiltration inside the cathode particles. It is also demonstrated that the degradation process can be studied through the changes in electron energy loss near-edge structure spectra. The investigation of a coating approach on LiNi0.8Co0.15Al0.05O2 materials through the mechanofusion process illustrates more microscopic-scale details regarding the thickness unevenness of the coating and some degree of physical intermixing between the core (LiNi0.8Co0.15Al0.05O2) and coating (LiFePO4 and alumina) precursors. In addition to good physical contact between the core and coating materials, further analysis at higher resolution reveals some nanoscale grains and defective areas near the top surface of the secondary particles following the mechanofusion coating process. / Thesis / Doctor of Philosophy (PhD)

The effects of physical image quality on reading and on perceived image quality from CRT and hard copy were studied in this experiment. The results showed that as the image quality of a display increased, indicated by an increase in the value of the MTFA, the reading speed increased and subjective image quality V; ratings increased. This change in reading speed and perceived image quality occurred in the hard copy as well as in the soft copy condition. Image quality, therefore, is concluded to be the major determinant of subjects' performance with respect to displayed information. This implies that if the image quality the displayed text ls the same on the display techniques used, subjects will read from CRT displays as fast as from hard copy displays. / Master of Science

<p dir="ltr">Lithium-ion batteries (LIBs) are integral to modern energy storage, with graphite serving as the preferred anode material due to its high conductivity, stability, and affordability. However, challenges related to irreversible initial lithium loss, electrolyte compatibility, and lithium-ion transport kinetics limit the performance and efficiency of graphite anodes. This dissertation addresses these critical issues by exploring novel approaches to enhance the functionality of graphite anodes. The first part of the research investigates the loss of lithium during the formation of the solid electrolyte interphase (SEI) on the graphite anode during the initial charge process. To counter this loss, a new method of graphite pre-SEI is introduced. By preforming SEI layers electrochemically on graphite powders, this technique improves the initial Coulombic efficiency of full cells without sacrificing active cathode material, providing a practical solution for offsetting lithium loss. The second part focuses on overcoming the limitations of traditional electrolyte systems. Graphite's tendency to exfoliate in the presence of organic solvents restricts electrolyte choices, particularly those beyond ethylene carbonate (EC)-based solvents. This chapter presents a new electrolyte design featuring nanoscale anion networks formed by concentrated lithium salts. These networks stabilize graphite by preventing solvent co-intercalation, offering new opportunities for LIBs to operate with a broader range of electrolytes while maintaining electrode integrity. The final chapter of this dissertation re-examines the conventional understanding of lithium-ion transport through the SEI. By constructing SEI-rich structures on a niobium oxide (Nb₂O₅) anode, a new mechanism of lithium transport is proposed. Contrary to the widely accepted two-step diffusion model, findings indicate that lithium transport can occur via a one-step pore diffusion process, eliminating the kinetic limitations previously associated with the SEI and enhancing fast-charging capabilities. In the fourth chapter, a surface modification on graphite surface with a electrochemically active layer is demonstrated to improve the surface diffusion of lithium and thus enhance the low-temperature performance of graphite anodes. The next chapter the high energy density V₂O₅ cathode is revisited with multi-nonmetal doping with improved cycling stability. Overall, this dissertation advances the understanding of graphite anodes in lithium-ion batteries by providing innovative solutions to SEI formation, electrolyte design, and lithium-ion transport, paving the way for more efficient and high-performance energy storage systems.</p>

Dans cette thèse nous démontrons le travail fait sur deux matériaux de cathodes pour les piles lithium-ion. Dans la première partie, nous avons préparé du phosphate de fer lithié (LiFePO4) par deux méthodes de lithiation présentées dans la littérature qui utilisent du phosphate de fer (FePO4) amorphe comme précurseur. Pour les deux méthodes, le produit obtenu à chaque étape de la synthèse a été analysé par la spectroscopie Mössbauer ainsi que par diffraction des rayons X (DRX) pour mieux comprendre le mécanisme de la réaction. Les résultats de ces analyses ont été publiés dans Journal of Power Sources. Le deuxième matériau de cathode qui a été étudié est le silicate de fer lithié (Li2FeSiO4). Une nouvelle méthode de synthèse a été développée pour obtenir le silicate de fer lithié en utilisant des produits chimiques peu couteux ainsi que de l’équipement de laboratoire de base. Le matériau a été obtenu par une synthèse à l’état solide. Les performances électrochimiques ont été obtenues après une étape de broyage et un dépôt d’une couche de carbone. Un essai a été fait pour synthétiser une version substituée du silicate de fer lithié dans le but d’augmenter les performances électrochimiques de ce matériau. / In this thesis, we demonstrate work on two different cathode materials for lithium-ion batteries. First, the synthesis of lithium iron phosphate (LiFePO4) is reproduced from literature using two lithiation methods starting with amorphous iron phosphate (FePO4). For both reactions, the product at each step of the synthesis was analyzed using Mössbauer Spectroscopy and X-ray diffraction in order to gain further insight of the reaction mechanism. The results of this work were published in Journal of Power Sources. The second cathode material of interest was lithium iron silicate (Li2FeSiO4). A novel synthetic method was developed to produce lithium iron silicate cost effectively starting with low cost precursors and basic laboratory equipment. The material was synthesized using a solid- state synthesis after milling and carbon coating, electrochemical performance was evaluated. An attempt was made to synthesize off-stoichiometric lithium iron silicate in order to increase the electrochemical performance of the material.

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.

High-power microwave, HPM, systems can be used as non-lethal weapons with the ability to destroy or disturb electronics, by damaging internal circuits and inducing high currents. Today microwave sources are being developed with peak powers exceeding 1 GW, one of these devices is the vircator, a narrowband source which is unique to the HPM community. In order to understand and develop microwave sources like the vircator it is necessary to have computer models, as simulations gives an invaluable understanding of the mechanisms involved during operation, saving time and development costs.                                                                  This thesis presents the results from a theoretical analysis and a simulation study using a well known electromagnetic particle-in-cell code, Computer Simulation Technology Particle Studio. The results are then compared to measured data from a HPM system, the Bofors HPM Blackout. The results show that CST PS can be used to design and study the coaxial vircator with good results.

Os filmes cerâmicos de manganito de lantânio dopado com estrôncio (LSM) e de manganito de lantânio dopado com estrôncio/zircônia estabilizada com ítria (LSM/YSZ) são utilizados como catodos das células a combustível de óxido sólido de temperatura alta (CaCOSTA). Estes filmes cerâmicos porosos foram depositados sobre o substrato cerâmico denso de YSZ, utilizado como eletrólito, componente estrutural do módulo, assim conferindo uma configuração de meia-célula denominada auto-suporte. O estudo da meia-célula é fundamental, pois na interface catodo/eletrólito ocorre a reação de redução do oxigênio, conseqüentemente influenciando no desempenho da CaCOSTA. Neste sentido, o presente trabalho contribui para a síntese de pós de LSM e LSM/YSZ e para o processamento de filmes finos, utilizando a técnica de pulverização de pó úmido, adotada para a conformação dos filmes cerâmicos por permitir a obtenção de camadas porosas com espessuras variadas na ordem de micrômetros. Os pós de LSM foram sintetizados pela técnica de citratos e os pós de LSM/YSZ pela técnica de mistura de sólidos. Na etapa de conformação foram preparadas suspensões orgânicas de LSM e LSM/YSZ alimentada por gravidade em um aerógrafo manual. Para a conformação do substrato de YSZ utilizou-se uma prensa uniaxial hidráulica. Foram possíveis a obtenção das meia-células de óxido sólido catodo/eletrólito de estruturas cristalinas hexagonal para a fase LSM e cúbica para a fase YSZ. E as micrografias das meia-células mostram que o substrato YSZ é denso, suficiente para ser utilizado como eletrólito sólido, e os filmes de LSM e LSM/YSZ apresentam-se porosos com espessura de aproximadamente 30 &mu;m e com boa aderência entre os catodos e o eletrólito. A presença do catodo compósito entre o catodo LSM e o substrato YSZ, possibilitou um aumento no desempenho eletroquímico na reação de redução do oxigênio. / The ceramic films of strontium-doped lanthanum manganite (LSM) and strontiumdoped lanthanum manganite/yttria-stabilized zirconia (LSM/YSZ) are used as cathodes of the high temperature solid oxide fuel cells (HTSOFC). These porous ceramic films had been deposited on the YSZ dense ceramic substrate, used as electrolyte, structural component of the module, thus conferring a configuration of half-cell called auto-support. The study of the half-cell it is basic, therefore in the interface cathode/electrolyte occurs the oxygen reduction reaction, consequently influencing in the performance of the HTSOFC. In this direction, the present work contributes for the processing of thin films, using the wet powder spraying technique, adopted for the conformation of the ceramic films for allowing the attainment of porous layers with thicknesses varied in the order of micrometers. The LSM powders were synthesized by the citrate technique and the LSM/YSZ powders synthesized by the solid mixture technique. In the stage of formation were prepared organic suspensions of LSM and LSM/YSZ fed by gravity in a manual aerograph. For the formation of the YSZ substrate was used a hydraulical uniaxial press. The attainment of solid oxide half-cells cathode/electrolyte was possible of crystalline structures hexagonal for phase LSM and cubic for phase YSZ. The half-cells micrographs show that the YSZ substrate is dense, enough to be used as solid electrolyte, and the LSM and LSM/YSZ films are presented porous with approximately 30 &mu;m of thickness and good adherence between the cathodes and the electrolyte. The presence of composite cathode between the LSM cathode and YSZ substrate, presented an increase in the electrochemical performance in the oxygen reduction reaction.