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Allen, Tristan. "Susceptibility of rehabilitated mine batter surface to mass movement." Thesis, Federation University Australia, 2018. http://researchonline.federation.edu.au/vital/access/HandleResolver/1959.17/168528.
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The goal of the research is to quantify coal properties that may affect the processes and controls governing rehabilitated brown coal mine surface mass movements. The research investigates weathering of coal and assesses the difference in strength characteristics between fresh and weathered coal. In addition to quantifying the mechanical properties of coal surfaces in a rehabilitated slope, permeability changes due to weathering of coal are also investigated. Changes in coal strength influence sliding resistance. Changes in coal permeability impact pore pressures above the coal surface, which may also affect sliding resistance on the coal – cover interface. To assess these issues, direct and residual shear tests were used to investigate the changes in shear strength due to weathering at low normal stresses applicable to shallow cover materials. Testing was undertaken with abrasive surfaces to simulate sliding on the contact coal surface beneath cover materials assuming that the cover material is stronger than the coal. The roughness of the abrasive surface proved to be unimportant for large strain shear strength. The shear strength for coal with different weathering and normal effective stresses was examined. Coal cohesion was found to be low, but some rebinding of coal would occur with time. A coal residual friction angle of 39.1 and 37.0 degrees was found for the unsaturated and saturated tested coal respectively. Permeability tests using oxygenated water were undertaken to investigate changes to brown coal permeability as a result of weathering. Even with low levels of oxidation achievable with the permeability test apparatus, coal permeability dropped over time. While the magnitude of the reduction was not large for low oxidation magnitudes, the impact on permeability was demonstrated. A weathering index was developed as part of the study to provide a quantitative basis for assessing the weathered state of coal samples. The index employed changes to Fourier Transform Infrared Spectroscopy (FTIR) spectra to define the state of weathering. To assess the rate and magnitude of weathering of coal through oxidation an autoclave was used to artificially weather brown coal. Fourier Transform Infrared Spectroscopy and Gas Chromatography used to analyse the results. As for the permeability testing the autoclave experiments could not be run for sufficient time to progress to complete weathering by oxidation. Nevertheless the principles of the test and the equipment specifications were developed so that they could be used in future to complete the determination of weathering rates. The research has demonstrated the importance of understanding coal weathering at the upper boundary of a rehabilitated coal surface to the potential for cover mass movements due to sliding at the coal cover interface.Masters by Research
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Davidson, Charles Nelson. "Surface action group defense model." Master's thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-05042010-020023/.
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Arbeltier, Steven. "Optimisation de dépôts de LIPON par pulvérisation magnétron RadioFréquence pour la fabrication de micro-batteries. Modélisation de l'interaction plasma-surface." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS170/document.
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La miniaturisation des batteries est devenue un défi technologique pour certaines industries. Ces micro-batteries, d’une dizaine de micromètres d’épaisseur, ont pour objectif d’alimenter des systèmes de taille réduite. Le LIPON est un des électrolytes envisagés pour leur fabrication. Il est déposé en couche-mince par pulvérisation magnétron radiofréquence de Li₃PO₄ sous plasma d’azote. Cette thèse étudie le comportement des particules au sein du plasma et formant le dépôt. Des mesures expérimentales d’émission optique et de densité électronique ont été mises en place, afin de fournir des données d’entrée et de validation pour différents modèles numériques. Le premier modèle décrit la cinétique réactionnelle au coeur du plasma, en 0D, afin d’identifier les espèces chimiques majoritaires et les réactions dominantes. Ceci a permis de concevoir une cinétique simplifiée pour le second modèle, 2D, traitant le déplacement des espèces chargées dans le plasma et permettant de caractériser la pulvérisation de la cible par les ions, tant au niveau des zones de pulvérisation de leur énergie et angle d’incidence. Les résultats obtenus ont été employés dans un modèle 3D simulant les trajectoires des atomes pulvérisés, afin d’étudier la répartition atomique sur le substrat et de déduire la composition de la couche mince déposée. Des caractéristiques propres à la cible lors de la pulvérisation ont été mises en évidence et confirmées par la comparaison entre les résultats numériques et expérimentauxThe scale reduction of batteries is a real technological challenge for the near future. These micro-batteries, about ten micrometers thick, are used to supply the power for small sized systems. LIPON is one of the most suitable electrolytes considered for industrial scale production. It is deposited in thin-film by radiofrequency magnetron sputtering of Li₃PO₄ in nitrogen plasma. This thesis is focused on particles behavior in plasma and during deposition. Optical emission spectroscopy and electron density measurements have been performed, to provide data used as input or validation for several numerical models. The first model describes plasma kinetics in the magnetron reactor, as 0D global model, and helps to identify the main chemical species and important reactions. This information has been useful to define a simplified kinetics for the second model, 2D, dealing with the charged species behavior in the plasma and describing target sputtering by ion bombardment. It provides the sputtered areas, ion energy and impinging angle onto the target. These obtained results have been employed in a 3D model that simulates sputtered atoms transport from the target to the substrate and predicting the thin-film features. Some characteristics of the target during sputtering have been highlighted and confirmed by the direct comparison between numerical and experimental results
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Charles-Blin, Youn. "Technologie de protection active des électrodes par fluoration de surface." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS068.
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Un changement de cap vers les technologies vertes est impulsé par les instances dirigeantes Européennes, désormais d’importants efforts sont engagés pour réduire notre empreinte carbone d’au moins 40% d’ici à 2030. Le développement de batteries sûres, présentant de meilleures densités d’énergie s’inscrit dans cette démarche. Ces technologies sont incontournables pour la croissance du secteur des transports électriques et des réseaux électriques intelligents. Pour répondre à la demande, de nouveaux matériaux doivent être développés et les matériaux existants doivent être améliorés pour atteindre de meilleures capacités de stockage et de plus hauts potentiels de travail. La recherche prospecte de nouveaux matériaux d’électrodes, de nouveaux électrolytes, mais aussi de nouvelles stratégies pour protéger les interfaces électrodes/électrolyte au cœur des batteries. En effet, dans les batteries secondaires, les interfaces électrodes/électrolyte jouent un rôle déterminant dans les performances électrochimiques et les durées de vie. Les électrolytes liquides organiques subissent des dégradations dans les fenêtres de potentiels appliqués conduisant à la formation d’une couche à la surface des électrodes négatives appelée « Solid Electrolyte Interphase » (SEI). La formation de cette interface amène une problématique à double tranchant : la SEI diminue l’efficacité coulombique et provoque des pertes de capacité irréversibles, mais elle permet également la passivation de l’électrode et prévient les mécanismes de vieillissements. Sachant cela, toute modification de la SEI se révèle délicate puisque l’équilibre entre les aspects positifs et négatifs peut être perdu. Par la chimisorption d’une fine couche fluorée à la surface des matériaux d’anode, nous sommes parvenus à améliorer le pouvoir passivant de la SEI à la surface de matériaux TiO2 et Li4Ti5O12 (LTO), conduisant à l’amélioration des comportements électrochimiques. Nous avons déterminé que de faibles quantités de fluor à la surface des matériaux actifs peuvent suffire à apporter de nombreuses améliorations. De plus, nous avons démontré que la fluoration est également bénéfique pour les matériaux d’électrodes positives tels que LiNi0.8Co0.15Al0.05O2 (NCA). En effet, le matériau NCA souffre d’instabilités structurales en surface qui entrainent des dégradations des capacités. Des comportements électrochimiques améliorés ont été observés pour des électrodes NCA fluorées, la fluoration permettant une stabilisation de la structure de surface du NCA.Nous avons prospecté l’influence de la fluoration de surface des matériaux actifs aux interfaces avec l’électrolyte, au moyen d’une approche multiéchelle. La nature chimique de la couche fluorée en surface des matériaux d’électrodes positives et négatives a été décrite par XPS, tout comme la distribution spatiale 2D du fluor par les techniques AES et SAM. Les propriétés du cœur et de la sous-surface des LTO-F ont été caractérisées par le couplage de la DRX, du Raman et de la RMN 19F du solide, aucune modification structurelle induite par la fluoration n’a été observée. L’influence de la fluoration de surface sur les performances électrochimiques a été évaluée par le couplage de cyclages galvanostatiques et d’analyses XPS et AES effectuées sur des électrodes ayant cyclées. Les LTO-F montrent une nouvelle réactivité vis-à-vis de l’électrolyte, conduisant à la formation d’une SEI plus fine et plus stable. Enfin, la génération des gaz par les électrodes LTO fluorés a été caractérisée par la GC-MS. Nous avons démontré que la formation de CO2 est réduite par la fluoration de surface. Dans l’ensemble, la stratégie déployée dans cette étude, allant de la synthèse à une caractérisation multiéchelle rigoureuse, propose de nouvelles solutions pour améliorer à la fois la stabilité de la SEI en surface d’électrodes négatives et la stabilité structurale de surface de matériaux d’électrodes positives, pour des batteries Li-ion de plus haute performanceA shift toward greener technologies has been impulsed by the European authorities and tremendous efforts are now engaged to drastically reduce our carbon footprint, by at least for 40 percent by 2030. The development of safe batteries with higher energy density is part of this shift, since this technology is critical for the commercialization and for the rise of electrical mobility and smart energy grid deployment. To do so, new materials need to be developed or existing materials need to be improved to reach higher specific capacities and working electrochemical potentials. The research prospects new electrode materials, new electrolytes and new ways to protect the electrode/electrolyte interphase within the batteries. Indeed, in secondary batteries, the anode/electrolyte interphase plays a key role in the electrochemical performances and life span. Since the classically used liquid organic electrolytes are not stable in the totality of the working potential window of Li-ion batteries, they undergo degradation on cycling of the battery, hence a Solid Electrolyte Interphase (SEI) is formed. This interphase passivates the negative electrodes from the electrolyte and prevents further aging processes, however as this passivation continues in cycling, it also lowers the coulombic efficiency and causes irreversible capacity loss. Knowing this, any modification of the SEI should be performed with parsimony as it could break the balance between the positive and negative aspect for the SEI. By synthetizing a chemisorbed thin fluorinated layer upon anode material, we managed to improve the passivating power of the SEI on TiO2 and Li4Ti5O12 (LTO) anodes, leading to enhanced electrochemical performance. We also determine that very low quantities of fluorine on the active electrode material surface leads to several beneficial effects. We demonstrated that the fluorination brings as well enhancement for positive electrode materials, such as LiNi0.8Co0.15Al0.05O2 (NCA). Indeed, NCA and NMC suffer structural surface instability, leading to self-heating and loss of performance. Improved cyclability is observed for fluorinated NCA electrodes as the fluorination stabilizes the surface structure.Surface fluorination was carried by a process using XeF2, for the first time applied to electrode materials. We aimed to prospect the influence of the surface fluorination on different aspect of a Li-ion battery, from the active material to the electrolyte interphase, thanks to a multi-scale probing approach. The chemical nature of the surface layer on negative and positive electrode materials was described by the mean of the XPS, as well as the fluorine distribution on the surface with both AES and SAM. The bulk and sub-surface properties of fluorinated LTO (LTO-F) were also investigated by coupling XRD, Raman Spectroscopy and NMR 19F, showing no modifications of the crystallographic structure. The influence of the surface fluorination on the electrochemical performance was investigated by galvanostatic cycling and by coupling XPS and SAM on cycled electrodes. We paid a specific attention to the impact of the fluorination on the SEI thickness and stability in charge and discharge. Indeed, LTO-F exhibits a new reactivity toward the electrolyte, leading to a thinner and stabilized SEI. Finally, the gas generation of the LTO-F electrodes has been investigated by Gas Chromatography – Mass Spectrometry (GC-MS), as gassing is known to be a roadblock to the commercialization of LTO. We demonstrated that the CO2 outgassing is reduced by the surface fluorination. Overall, the strategy implemented in this work, from synthesis to thorough characterization, offer new solutions to improve both SEI formed on negative electrode material as well as surface structural stability of positive electrode material, leading to improved Li-ion batteries
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Roland, Aude. "Nanostructuration et contrôle de l'interface électrode/électrolyte appliqués à des électrodes de silicium pour batteries Li-ion." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS128.
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Le silicium est l’un des matériaux les plus prometteurs comme matériau actif d’électrode négative pour la prochaine génération de batteries lithium-ions (LiB). En effet, il possède une capacité spécifique 10 fois supérieure à celle du graphite actuellement commercialisé dans les batteries. Son bas potentiel de travail permet d’atteindre une forte densité d’énergie tout en limitant le risque de croissance dendritique responsable des emballements thermiques. Malgré ses avantages, ses limites intrinsèques telles que sa faible conductivité électronique et ionique et l’expansion volumique importante induite par la formation d’alliages lithiés repoussent toujours son incorporation dans les batteries commerciales. En effet, cette expansion volumique du matériau, entraîne la pulvérisation de l’électrode, isolant électriquement la matière active qui est à l’origine d’une faible rétention de capacité en cyclage. La pulvérisation du matériau actif induit également la formation de nouvelles interfaces avec l’électrolyte induisant une formation accrue de SEI, très pénalisante pour les performances. Dans ces travaux, la nanostructuration du silicium est proposée pour limiter la pulvérisation. Différentes nanostructures ont été étudiées telles que les nanoplots, les nanoparticules et les matériaux nanoporeux de silicium. Les nanoplots ont été étudiés sous forme d‘électrodes sur puce, l’optimisation de leur synthèse ainsi que les premiers tests électrochimiques en batterie ont été réalisés. Les électrodes de silicium poreux ont été préparées par gravure électrochimique d’un wafer de Si, puis étudiées sous forme d’électrodes composites en batterie. L’étude des nanoparticules a permis d’optimiser la formulation d’électrode et les conditions générales de test. Ces paramètres ont été appliqués aux électrodes à base de Si poreux pour étudier l’impact des propriétés morphologiques (modifiables par traitement thermique) sur les performances du Si en batterie Li-ion. L’étude s’est ensuite tournée vers l’interface électrode/électrolyte. Pour ce faire, la surface du Si a été modifiée par différents enrobages de carbone (carbone amorphe, graphene-like, Pitch). Après la comparaison des tests électrochimiques de l’ensemble de ces électrodes, l’étude s’est portée sur la nature et l’évolution en cyclage de la composition de la SEI de ces électrodes composites à base de Si modifié en surface. De la même manière une étude complète de l’impact du pH de formulation sur les performances a été réaliséeSilicon is one of the most promising active material for the next generation lithium-ion batteries (LiB) negative electrode. Indeed, it exhibits a 10 times higher specific capacity than graphite currently commercialized in batteries. Its low working potential achieves high energy density while limiting the dendrite growth responsible for thermal runaway. Despite its advantages, its intrinsic limits such as low electronic and ionic conductivities and the large volume expansion induced by the formation of the lithiated phases still avoid its incorporation into commercial batteries. Indeed, this active material expansion causes the electrode pulverization, leading to active material electrical isolation and so a low capacity retention in cycling. The active material spraying also induces new interfaces formation in contact with the electrolyte, which induces SEI formation and limited performance. In these work, silicon nanostructuring is proposed to limit active material spraying. Different nanostructures have been studied such as nanowires, nanoparticles and nanoporous silicon materials. On-chip nanowires have been studied, their elaboration method was optimized and their battery performance were tested. Porous silicon electrodes were prepared by electrochemical etching of a Si wafer and studied in composite electrodes. The nanoparticles study, were used to optimize the electrode formulation and the general testing conditions. These parameters were then applied to study the morphological properties (modulated by heat treatment) impact on porous Si-based electrodes performance in Li-ion battery. Afterward, the study focused on the electrode / electrolyte interface, the Si surface was modified by different carbon coatings (amorphous carbon, graphene-like, pitch). The electrochemical performance of these electrodes were compared. The SEI composition and its evolution in cycling was followed. Additionally, a complete study of the pH of the aqueous formulated electrode on the performance of that one was carried out
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Nordh, Tim. "Lithium titanate as anode material in lithium-ion batteries : -A surface study." Licentiate thesis, Uppsala universitet, Strukturkemi, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-267567.
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The ever increasing awareness of the environment and sustainability drives research to find new solutions in every part of society. In the transport sector, this has led to a goal of replacing the internal combustion engine (ICE) with an electrical engine that can be powered by renewable electricity. As a battery for vehicles, the Li-ion chemistries have become dominant due to their superior volumetric and gravimetric energy densities. While promising, electric vehicles require further improvements in terms of capacity and power output before they can truly replace their ICE counterparts. Another aspect is the CO2 emissions over lifetime, since the electric vehicle itself presently outlives its battery, making battery replacement necessary. If the lifetime of the battery could be increased, the life-cycle emissions would be significantly lowered, making the electric vehicle an even more suitable candidate for a sustainable society. In this context, lithium titanium oxide (LTO) has been suggested as a new anode material in heavy electric vehicles applications due to intrinsic properties regarding safety, lifetime and availability. The LTO battery chemistry is, however, not fully understood and fundamental research is necessary for future improvements. The scope of this project is to investigate degradation mechanisms in LTO-based batteries to be able to mitigate these and prolong the device lifetime so that, in the end, a suitable chemistry for large scale applications can be suggested. The work presented in this licentiate thesis is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) was applied to determine whether the usage of LTO would prevent anode-side electrolyte decomposition, as suggested from the intercalation potential being inside the electrochemical stability window of common electrolytes. It has been found that electrolyte decomposition indeed occurs, with mostly hydrocarbons of ethers, carboxylates, and some inorganic lithium fluoride as decomposition products, and that this decomposition to some extent ensued irrespective of electrochemical battery operation activity. Second, an investigation into how crossover of manganese ions from Mn-based cathodes influences this interfacial layer has been conducted. It was found, using a combination of high-energy x-ray photoelectron spectroscopy (HAXPES) and near-edge x-ray absorption fine structure (NEXAFS) that although manganese is present on the LTO anode surface when paired with a common manganese oxide spinel cathode, the manganese does little to alter the surface chemistry of the LTO electrode.
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Younesi, Reza. "Characterization of Reaction Products in the Li-O2 Battery Using Photoelectron Spectroscopy." Doctoral thesis, Uppsala universitet, Institutionen för kemi - Ångström, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-183887.
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The rechargeable Li-O2 battery has attracted interest due to its high theoretical energy density (about 10 times better than today’s Li-ion batteries). In this PhD thesis the cycling instability of the Li-O2 battery has been studied. Degradation of the battery has been followed by studying the interface between the electrodes and electrolyte and determining the chemical composition and quantity of degradation products formed after varied cycling conditions. For this in-house and synchrotron based Photoelectron Spectroscopy (PES) were used as a powerful surface sensitive technique. Using these methods quantitative and qualitative information was obtained of both amorphous and crystalline compounds. To make the most realistic studies the carbon cathode pore structure was optimised by varying the binder to carbon ratio. This was shown to have an effect on improving the discharge capacity. For Li-O2 batteries electrolyte decomposition is a major challenge. The stability of different electrolyte solvents and salts were investigated. Aprotic carbonate and ether based solvents such as PC, EC/DEC, TEGDME, and PEGDME were found to decompose during electrochemical cycling of the cells. The carbonate based electrolytes decompose to form a 5-10 nm thick surface layer on the carbon cathode during discharge which was then removed during battery charging. The degradation products of the ether based electrolytes consisted mainly of ether and carbonate based surface species. It is also shown that Li2O2 as the final discharge product of the cell is chemically reactive and decomposes carbonate and ether based solvents. The stability of lithium electrolyte salts (such as LiPF6, LiBF4, LiB(CN)4, LiBOB, and LiClO4) was also studied. The PES results revealed that all salts are unstable during the cell cycling and in contact with Li2O2. Decomposition layers thinner than 5 nm were observed on Li2O2. Furthermore, it is shown that the stability of the interface on the lithium anode is a chief issue. When compared to Li batteries (where oxygen levels are below 10 ppm) working in the presence of excess oxygen leads to the decomposition of carbonate based electrolytes to a larger degree.
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Azmi, Raheleh [Verfasser], and M. J. [Akademischer Betreuer] Hoffmann. "Oberflächenanalytische Ansätze zur zuverlässigen Charakterisierung von Lithium-Ionen-Batterie-Elektroden = Surface Analytical Approaches to Reliably Characterize Lithium-Ion Battery Electrodes / Raheleh Azmi ; Betreuer: M. J. Hoffmann." Karlsruhe : KIT-Bibliothek, 2018. http://d-nb.info/1170230563/34.
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Nordh, Tim. "A Quest for the Unseen : Surface Layer Formation on Li4Ti5O12 Li-Ion Battery Anodes." Doctoral thesis, Uppsala universitet, Strukturkemi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-331349.
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The electric vehicle itself today outlives its battery, necessitating battery replacement. Lithium titanium oxide (LTO) has, in this context, been suggested as a new anode material in heavy electric vehicle applications due to intrinsic properties regarding safety, lifetime and availability. The work presented here is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) has been applied to determine how and if the usage of LTO could prevent extensive anode-side electrolyte decomposition and build-up of a surface layer. The presence of a solid electrolyte interphase (SEI) comprising LiF, carbonates and ether compounds was found in half-cells utilizing a standard ethylene:diethylcarbonate electrolyte with 1 M LiPF6. Via testing of symmetrical LTO-LTO cells, the stability of the formed SEI was put in to question. Moreover, the traditional polyvinylidene difluoride (PVdF) binder was replaced by more environmentally benign carboxylmethyl cellulose (CMC) and polyacrilic acid (PAA) binders in LTO electrodes, and it was found that CMC helped to form a more stable surface-layer that proved beneficial for long term cycling. Following the half-cell studies, full-cells were investigated to observe how different cathodes influence the SEI of LTO. The SEI in full-cells displayed characteristics similar to the half-cells, however, when utilizing a high voltage LiNi0.5Mn1.5O4 cathode, more electrolyte decomposition could be observed. Increasing the operational temperature of this battery cell generated even more degradation products on the LTO electrodes. Mn was also found on the anode when using Mn-based cathodes, however, it was found in its ionic state and did not significantly affect the composition or behavior of the observed SEI layer. Furthermore, by exchanging the electrolyte solvent for propylene carbonate, the thickness of the SEI increased, and by replacing the LiPF6 salt for LiBF4 the stability of the SEI improved. Thus is it demonstrated that such a passivation can be beneficial for the long-term surface stability of the electrode. These findings can therefore help prolong the lifetime of LTO-based battery chemistries.
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Dalverny, Anne-Laure. "Étude théorique des phénomènes électrochimiques de surfaces et d'interfaces dans les matériaux d'électrodes pour batterie Li-ion." Thesis, Montpellier 2, 2011. http://www.theses.fr/2011MON20100/document.
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Les nombreuses problématiques soulevées par la nanostructuration des électrodes pour batteries Li-Ion nécessitent de nouveaux développements théoriques. Ce travail propose une nouvelle méthodologie basée sur des calculs de type premiers principes (DFT) et prenant en compte explicitement les phénomènes électrochimiques à l'échelle du matériau massif, de ses surfaces et de ses interfaces. Développée dans le cadre des réactions de conversion, en particulier celle de l'oxyde de cobalt CoO + 2 Li → Co + Li2O, cette méthodologie, simple et généralisable à tout type de réaction polyphasée, permet de dégager les facteurs mécaniques, chimiques et électriques responsables des phénomènes électrochimiques aux interfaces et d'interpréter les mécanismes réactionnels observés expérimentalementThe numerous questions arising from the nanostructuration of Li-ion batteries require new developments in theoretical methods. This work proposes a new methodology based on first principles calculations (DFT) andallows explicit treatment of the electrochemical phenomena at the bulk compound level, and also at the surface and interface level.Developed in the context of the conversion reactions, in particular the conversion of the cobalt oxide CoO + 2 Li → Co + Li2O, this simple methodology can be extended to any polyphasic reaction. It sheds light on the mechanical, chemical and electrical factors responsible for the electrochemical phenomena at the interfaces and allows the interpretation of the mechanisms that are experimentally observed
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Eriksson, Tom. "LiMn2O4 as a Li-ion Battery Cathode. From Bulk to Electrolyte Interface." Doctoral thesis, Uppsala universitet, Institutionen för materialkemi, 2001. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-1397.
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LiMn2O4 is ideal as a high-capacity Li-ion battery cathode material by virtue of its low toxicity, low cost, and the high natural abundance of Mn. Surface related reactions and bulk kinetics have been the major focus of this work. The main techniques exploited have been: electrochemical cycling, X-ray diffraction, X-ray photoelectron spectroscopy, infrared spectroscopy and thermal analysis. Interface formation between the LiMn2O4 cathode and carbonate-based electrolytes has been followed under different pre-treatment conditions. The variables have been: number of charge/discharge cycles, storage time, potential, electrolyte salt and temperature. The formation of the surface layer was found not to be governed by electrochemical cycling. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, LixPFy (or LixBFy, depending on the electrolyte salt used), LixPOyFz (or LixBOyFz) and poly(oxyethylene). Additional compounds were found at elevated temperatures: phosphorous oxides (or boron oxides) and polycarbonates. A model has been presented for the formation of these surface species at elevated temperatures. The cathode surface structure was found to change towards a lithium-rich and Mn3+-rich compound under self-discharge. The reduction of LiMn2O4, in addition to the high operating potential, induces oxidation of the electrolyte at the cathode surface. A novel in situ electrochemical/structural set-up has facilitated a study of the kinetics in the LiMn2O4 electrode. The results eliminate solid-phase diffusion as the rate-limiting factor in electrochemical cycling. The electrode preparation method used results in good utilisation of the electrode, even at high discharge rates.
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Lacson, Ernani Morena Morgan Harold R. "Total Quality Leadership as it applies to the Surface Navy." Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA243195.
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Thesis (M.S. in Management)--Naval Postgraduate School, December 1990.Thesis Advisor(s): Crawford, Alice ; Roberts, Benjamin. "December 1990." Description based on title screen as viewed on March 31, 2010. DTIC Identifier(s): Leadership Training, Management Planning And Control, Officer Personnel, Naval Personnel, Naval Warfare, Quality Control, TQM (Total Quality Management), Quality Management, TQM, Total Quality Management, Theses. Author(s) subject terms: Total Quality Leadership, Leadership, Management and Education Training, Command Excellence Program. Includes bibliographical references (p. 91-95). Also available in print.
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Macaraig, Lea Cristina De Jesus. "Studies on Surface Modified Metal Oxides Nanofibers and Thin Films for Solar Energy Conversion and Storage." Kyoto University, 2013. http://hdl.handle.net/2433/180445.
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Ma, Wen. "Studies on Surface Modified Non-graphitizable Carbon Negative Electrodes in Lithium-ion Batteries." Kyoto University, 2017. http://hdl.handle.net/2433/227632.
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Musella, Elisa. "Surface dynamic of copper nitroprusside as a cathode material: observation by XPS and SEM." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2017. http://amslaurea.unibo.it/14456/.
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Nowadays, rechargeable Li-ion batteries play an important role in portable consumer devices. The formation of surface films on electrodes in contact with non-aqueous electrolytes in lithium-ion batteries has a deep impact on battery performance. A basic understanding of such films is necessary for the improvement of power sources.
The surface chemistry and morphology of a cathode material, copper nitroprusside, have here been evaluated by X-ray Photoelectron Spectroscopy (XPS) and Scanning Electron Microscopy (SEM), and placed in relation to the performance of the electrodes. Interface formation between the cathode and carbonate-based electrolytes has been followed and characterised. The variables have been: number of charge/discharge cycles and air contact. The species precipitating on the surface of the cathodes at ambient temperature have been determined to comprise a mixture of organic and inorganic compounds: LiF, LixPFy, LixPOyFz, inorganic and organic carbonates. Moreover a problematic due to UHV and X-ray exposure has been followed.
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Inamoto, Jun-ichi, and Junichi Inamoto. "Electrochemical Characterization of Surface-State of Positive Thin-Film Electrodes in Lithium-Ion Batteries." Kyoto University, 2017. http://hdl.handle.net/2433/226784.
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Young, M. Bridget. "Comparison of combat system architectures for future surface combatants." Master's thesis, This resource online, 1992. http://scholar.lib.vt.edu/theses/available/etd-12232009-020158/.
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Reddi, Rahul. "In-situ characterization of Li-ion battery electrodes using atomic force microscopy." The Ohio State University, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=osu1524215477787917.
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Andersson, Edvin. "Spectroelectrochemical analysis of the Li-ion battery solid electrolyte interphase using simulated Raman spectra." Thesis, Uppsala universitet, Fasta tillståndets fysik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-413474.
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Lithium Ion Batteries (LIBs) are important in today's society, powering cars and mobile devices. LIBs consist of a negative anode commonly made of graphite, and a positive cathode commonly made from transition metal oxides. Between these electrodes are separators and organic solvent based electrolyte. Due to the high potential of LIBs the electrolyte is reduced at the anode. The electrolyte reduction results in the formation of a layer called the Solid Electrolyte Interphase (SEI), which prohibits the further breakdown of the electrolyte. Despite being researched for over50 years, the composition formation of the SEI is still poorly understood. The aim of this project is to develop strategies for efficient identification and classification of various active and intermediate components in the SEI, to, in turn, gain an understanding of the reactions taking place, which will help find routes to stabilize and tailor the composition of the SEI layer for long-term stability and optimal battery performance. For a model gold/li-ion battery electrolyte system, Raman spectra will be obtained using Surface Enhanced Raman Spectroscopy (SERS) in a spectroelectrochemical application where the voltage of the working gold electrode is swept from high to low potentials. Spectra of common components of the SEI as well as similar compounds will be simulated using Density Functional Theory (DFT). The DFT data is also used to calculate the spontaneity of reactions speculated to form the SEI. The simulated data will be validated by comparing it to experimental spectra from pure substances. The spectroelectrochemical SERS results show a clear formation of Li-carbonate at the SERS substrate, as well as the decomposition of the electrolyte into other species, according to the simulated data. It is however shown that there are several issues when modelling spectra, that makes it harder to correlate the simulated spectra with the spectroelectrochemical spectra. These issues include limited knowledge of the structure of the compounds thought to form on the anode surface, and incorrect choices in simulational parameters. To solve these issues, more work is needed in these areas, and the spectroelectrochemical methods used in this thesis needs to be combined with other experimental methods to narrow down the amount of compounds to be modelled. More work is also needed to avoid impurities in the electrolyte. Impurities leads to a thick inorganic layer which prohibits the observation of species in the organic layer.
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Avital, Ittai. "Two-period, stochastic, supply-chain models with recourse for Naval surface warfare /." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2004. http://library.nps.navy.mil/uhtbin/hyperion/04Mar%5FAvital.pdf.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, March 2004.Thesis advisor(s): R. Kevin Wood, Moshe Kress, Gerald G. Brown. Includes bibliographical references (p. 47-48). Also available online.
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Eriksson, Tom. "LiMn2O4 as a Li-ion Battery Cathode. From Bulk to Electrolyte Interface." Doctoral thesis, Uppsala : Acta Universitatis Upsaliensis : Univ.-bibl. [distributör], 2001. http://publications.uu.se/theses/91-554-5100-4/.
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Richter, Matthew P. "Analysis of operational manning requirements and deployment procedures for unmanned surface vehicles aboard U.S. Navy ships." Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 2006. http://library.nps.navy.mil/uhtbin/hyperion/06Sep%5FRichter.pdf.
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Hatzopoulos, Epaminondas A. "A modern naval combat model." Thesis, Monterey, California : Naval Postgraduate School, 1990. http://handle.dtic.mil/100.2/ADA238163.
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Thesis (M.S. in Operations Research)--Naval Postgraduate School, September 1990.Thesis Advisor(s): Weir, Maurice D. ; Hughes, Wayne P. Second Reader: Lind, Judith. "September 1990." Description based on title screen as viewed on December 29, 2009. DTIC Identifier(s): Naval warfare, mathematical models, lessons learned. Author(s) subject terms: Naval combat models, combat theory, salvo warfare, human factors in combat models. Includes bibliographical references (p. 98). Also available in print.
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Alves, Dalla Corte Daniel. "Effects of surface chemical treatment on silicon negative electrodes for lithium-ion batteries: an in situ infrared spectroscopic study." Palaiseau, Ecole polytechnique, 2013. http://pastel.archives-ouvertes.fr/docs/00/87/75/45/PDF/Daniel_PhD_X.pdf.
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L'utilisation d'électrodes négatives en silicium est susceptible d'apporter un gain notable en densité de stockage énergétique dans les batteries Li-ion. Toutefois, la réversibilité du cyclage et la stabilité à long terme des électrodes de silicium sont toutes deux dépendantes de l'efficacité de la passivation par la couche interfaciale d'électrolyte solide (SEI) qui se forme à la surface de l'électrode. La spectroscopie infrarouge in situ a été utilisée pour étudier les phénomènes de surface et le volume qui interviennent au cours du cyclage électrochimique du silicium amorphe. Les électrodes ont été préparées par dépôt de couches minces de silicium amorphe hydrogéné sur des prismes utilisés en géométrie de réflexion totale atténuée (ATR), ce qui autorise de suivre l'évolution de l'électrode dans son environnement (électro)chimique. On voit ainsi qu'une couche de passivation de surface se forme très rapidement lors de la première lithiation, se dissous partiellement pendant la délithiation et croit progressivement pendant les cycles successifs. La composition de l'électrolyte joue un rôle majeur sur la composition chimique de la couche SEI. Par ailleurs, les électrodes ont été préalablement soumises à différents traitements chimiques ou électrochimiques permettant le greffage de différentes couches moléculaires à la surface de silicium. Les résultats montrent que les performances électrochimiques du silicium ainsi prétraité sont fortement influencées par la nature chimique, la taille et le taux de recouvrement des espèces greffées. Les monocouches constituées de groupements carboxy-alkyles représentent une solution attractive pour la fonctionnalisation des électrodes de silicium, probablement en raison de leur structure dense, de leur ancrage covalent sur la matière active et leur similarité chimique avec des produits typiques de la couche SEI. Un tel traitement de surface offre à la couche SEI la possibilité de s'ancrer solidement à l'électrode, augmente sa stabilité et améliore ainsi les performances électrochimiques du silicium. D'autre part, le procédé de dépôt chimique en phase vapeur assisté par plasma, utilisé pour obtenir les électrodes en silicium amorphe, permet d'ajouter à la matière active du carbone sous forme de groupes méthyles (CH3). Ceci conduit à une augmentation de la cyclabilité de l'électrode. Le silicium ainsi méthylé présente une amélioration de ses performances électrochimiques en même temps que se développe à sa surface une couche SEI épaisseSilicon represents an expressive gain in energy density for negative electrodes in Li-ion batteries. Reversible cycling and long term stability of silicon electrodes are both dependent of the passivation efficiency of the solid electrolyte interface (SEI) layer formed at the electrode surface. Surface and bulk phenomena of amorphous silicon were studied by in-situ FTIR spectroscopy during electrochemical cycling. Electrodes were prepared by thin-film deposition of hydrogenated amorphous silicon on ATR crystals, allowing for the measurements of electrode reactions in the original chemical environment. The results reveal a dynamic surface passivation layer which is intensively formed during the first lithiation, partially dissolved during delithiation and that grows continuously along the cycling life. Electrolyte components play a major role on the chemical composition of the SEI layer. Various electrode treatments were obtained by chemical and electrochemical grafting of different molecular layers on silicon surface. The results show that the silicon electrochemical performance is strongly affected by the chemical nature, chain size and covering ratio of the grafted species. Carboxyl-terminated monolayers represent an attractive functionalization for silicon electrodes due to their densely packed structure, strong covalent attachment to the active material and chemical similarity with typical SEI products. Such a surface treatment leads to a good anchoring support for the SEI, increasing its stability and improving silicon electrochemical performance. On the other hand, the use of plasma enhanced chemical vapor deposition technique for preparing the amorphous silicon electrodes allow us to add carbon (as -CH3) to the silicon layer, with verified improvements in cycling performance. This methylated silicon material show improved electrochemical performances at same time as it develops a thicker SEI layer
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Samad-Suhaeb, Mujahid. "Aerodynamics of battle damaged finite aspect ratio wings." Thesis, Loughborough University, 2005. https://dspace.lboro.ac.uk/2134/10736.
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When an aircraft is aerodynamically or structurally damaged in battle, it may not able to complete the mission and the damage may cause its loss. The subject of aircraft battle survivability is one of critical concern to many disciplines, whether military or civil. This thesis considered and focused on Computational Fluid Dynamics [CFD] predictions and experimental investigations into the effects of simulated battle damage on the low-speed aerodynamics of a fmite aspect ratio wing. Results showed that in two-dimensional [2d] and three-dimensional [3D] CFD simulations, Fluent's® models work reasonably well in predicting jets flow structures, pressure distributions, and pressure-coefficient Cp's contours but not for aerodynamic coefficients. The consequences were therefore that CFD prediction was poor on aerodynamic-coefficients increments. The prediction of Cp's achieved good agreement upstream and near the damage hole, but showed poor agreement at downstream of the hole. For the flow structure visualisation, at both weak and strong jet incidences, the solver always predicted pressure-distribution-coefficient lower at upstream and higher at downstream. The results showed relatively good agreement for the case of transitional and strong jet incidences but slightly poor for weak jet incidences. From the experimental results of Finite Wing, the increments for Aspect-ratio, AR6, AR8 and ARIO showed that as damage moves out towards the tip, aerodynamic-coefficients increments i.e. lift-loss and drag-rise decreased, and pitching-moment-coefficient increment indicated a more positive value at all incidence ranges and at all aspect ratios. Increasing the incidence resulted in greater magnitudes of lift-loss and drag-rise for all damage locations and aspect ratios. At the weak jet incidence 4° for AR8 and in all of the three damage locations, the main characteristics of the weak-jet were illustrated clearly. The increments were relatively small. Whilst at 8°, the flow structure was characterised as transitional to stronger-jet. In Finite Wing tests and for all damage locations, there was always a flow structure asymmetry. This was believed to be due to gravity, surface imperfection, and or genuine feature. An 'early strong jet' that indicated in Finite Wing-AR8 at 'transitional' incidence of 8°, also indicated in twodimensional results but at the weak-jet incidence of 4°. For the application of 2d data to AR6, AR8, and ARIO, an assessment of 2d force results led to the analysis that the tests in the AAE's Low Turbulence Tunnel for 2d were under-predicting the damage effects at low incidence, and over-predicting at high incidences. This suggested therefore that Irwin's 2d results could not be used immediately to predict three-dimensional.
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Arlot-Corré, Stéphanie. "Étude et stabilisation des hydrures d'alliages substitués La(1-x)RxNi(5-y)My (R=Ce ou Nd, et M=Al ou Zr) par empoisement des surfaces." Université Joseph Fourier (Grenoble ; 1971-2015), 1999. http://www.theses.fr/1999GRE10086.
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Notre travail a porte sur le developpement et l'optimisation de traitements de surface originaux a base de monoxyde de carbone et de dioxyde de soufre en vue de la stabilisation des hydrures des materiaux substitues la#1##xr#xni#5##yal#y (r = ce ou nd). Dans cette optique, les caracteristiques structurales et microstructurales de ces composes ont ete etudiees rigoureusement, ainsi que leurs proprietes d'hydruration. Le traitement de surface a base de dioxyde de soufre s'est revele particulierement efficace pour la stabilisation des hydrures de lani#5 a l'air, en offrant la possibilite de limiter la cinetique de desorption a 0. 044 h/lani#5 par heure a 25c. L'effet de stabilisation est obtenu par le depot d'une fine couche de soufre, sulphates et sulphures de nickel en surface. L'utilisation des hydrures traites au so#2 pour l'hydrogenation de composes organiques s'est montree inutile, en raison de la suppression du pouvoir catalytique de l'hydrure par le traitement. Le developpement du traitement de surface au monoxyde de carbone a permis egalement de limiter la cinetique de desorption d'hydrogene a 0. 046 h/lani#5 par heure. Nous avons montre que la diminution de temperature de conservation de l'echantillon permet de ralentir davantage la cinetique de desorption. L'utilisation de poudre de faible granulometrie augmente egalement la stabilisation. D'autre part, ce traitement permet la stabilisation d'hydrures a haute pression d'equilibre, comme les hydrures des composes substitues la#1##xr#xni#5 (r = ce ou nd) et leur utilisation comme catalyseurs des reactions d'hydrogenation de composes organiques. Finalement, nous avons montre que l'utilisation du traitement de surface au co rendait possible l'observation de l'hydrure intermediaire lani#5h#3 obtenu par broyage mecanique. Les electrodes metal-hydrogene fabriquees a partir d'une telle poudre montre une tres bonne capacite de decharge electrochimique egale a 307 mah/g, mais une duree de vie relativement courte, due a une corrosion excessive des poudres.
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Zhang, Yin. "Study on electronic structure and rate performance of olivine phosphate cathode materials." Thesis, Queensland University of Technology, 2020. https://eprints.qut.edu.au/201911/1/Yin_Zhang_Thesis.pdf.
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This thesis has investigated a family of olivine phosphate battery materials using various spectroscopic techniques. The research has demonstrated that the surfaces of these materials display nanoscale Lithium depletion. The differentiated surface layers are responsible for many of the measured properties, which have so far been mostly attributed to the bulk of the compounds. In the case of LiFePO4, the surface layers also concentrate the dopants, which have been reported as beneficial for the electrochemical performance. The identified surface differentiation seems present in other families of battery materials. Its identification provides new insights on particle surface design for performance optimization.
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Sun, Xiaolei, Guang-Ping Hao, Xueyi Lu, Lixia Xi, Bo Liu, Wenping Si, Chuansheng Ma, et al. "High-defect hydrophilic carbon cuboids anchored with Co/CoO nanoparticles as highly efficient and ultra-stable lithium-ion battery anodes." Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2017. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-221863.
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We propose an effective strategy to engineer a unique kind of porous carbon cuboid with tightly anchored cobalt/cobalt oxide nanoparticles (PCC–CoOx) that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The host carbon cuboid features an ultra-polar surface reflected by its high hydrophilicity and rich surface defects due to high heteroatom doping (N-/O-doping both higher than 10 atom%) as well as hierarchical pore systems. We loaded the porous carbon cuboid with cobalt/cobalt oxide nanoparticles through an impregnation process followed by calcination treatment. The resulting PCC–CoOx anode exhibits superior rate capability (195 mA h g−1 at 20 A g−1) and excellent cycling stability (580 mA h g−1 after 2000 cycles at 1 A g−1 with only 0.0067% capacity loss per cycle). Impressively, even after an ultra-long cycle life exceeding 10 000 cycles at 5 A g−1, the battery can recover to 1050 mA h g−1 at 0.1 A g−1, perhaps the best performance demonstrated so far for lithium storage in cobalt oxide-based electrodes. This study provides a new perspective to engineer long-life, high-power metal oxide-based electrodes for lithium-ion batteries through controlling the surface chemistry of carbon host materials.
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Cheng, Hsiu-Wei [Verfasser], Martin [Gutachter] Stratmann, and Markus [Gutachter] Valtiner. "Probing the solid/liquid interfacial structure of ionic liquids and battery fluids by surface force measurements / Hsiu-Wei Cheng ; Gutachter: Martin Stratmann, Markus Valtiner." Bochum : Ruhr-Universität Bochum, 2017. http://d-nb.info/1133361757/34.
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Lebègue, Estelle. "Greffage de molécules électroactives sur carbones activés pour le stockage électrochimique de l'énergie." Nantes, 2013. http://archive.bu.univ-nantes.fr/pollux/show.action?id=e099f75a-eafd-4a1c-b0f4-57dd71d75f96.
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L’augmentation rapide de la consommation d’électricité dans les pays émergents oblige à produire cette énergie à partir de ressources polluantes et l’absence de dispositifs de stockage performants oblige à mettre en place des réseaux de distributions complexes. Parmi les principaux systèmes de stockage existants, les batteries se caractérisent par une densité d’énergie élevée et une faible puissance, tandis que les supercondensateurs ont une densité de puissance élevée, mais une faible densité d’énergie. Afin d’améliorer les performances des dispositifs, des efforts récents ont été fait pour concevoir de nouveaux systèmes hybrides combinant les avantages des batteries et des supercondensateurs. Une stratégie prometteuse consiste à introduire des molécules organiques électroactives à la surface des carbones activés couramment utilisés comme matériaux d’électrodes, pour ajouter une contribution faradique au stockage de la charge électrique. L’objectif de ce travail de thèse concerne précisément l’étude de l’impact du greffage de molécules sur les performances des matériaux composites obtenus. Des molécules électroactives en milieux aqueux et organiques ont été sélectionnées et différentes procédures de modification ont été testées afin de maximiser le taux de greffage Des carbones activés microporeux et mésoporeux ont été modifiés afin d’évaluer l’effet de la porosité du carbone sur le stockage électrochimique de l’énergie. Enfin, des poudres de carbones modifiées utilisées comme matériaux d’électrodes positive et négative ont été combinées et les performances du dispositif hybride ainsi obtenu ont été évaluées en termes de densité d’énergie et de puissanceThe rapid increase in electricity consumption in emerging countries obliges to produce this energy from polluting resources and the absence of efficient storage devices obliges to set up complex distribution networks. At present, electric storage devices range from electrochemical capacitors, which can supply high power to batteries, which suffer from low power but can supply high electrical energy density. In retrospect, a promising approach would consist in combining both the advantages of capacitors and batteries to achieve versatile energy storage systems. A promising strategy consists to introduce redox active molecules onto the surface of activated carbon commonly used as electrode materials, for adding a faradaic contribution to the charge storage. The object of this work is to study the impact of the grafting on the performances of the composite materials obtained. Electroactive molecules in aqueous and organic media were selected and different grafting procedures were experimented for maximizing the grafting yield. Here, we propose a promising architecture for the design of organic batteries constructed from generic elements which consist in fast redox-active small molecules combined to a porous carbon network. The energy density and the power of the resulting hybrid system were evaluated
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Sun, Xiaolei, Guang-Ping Hao, Xueyi Lu, Lixia Xi, Bo Liu, Wenping Si, Chuansheng Ma, et al. "High-defect hydrophilic carbon cuboids anchored with Co/CoO nanoparticles as highly efficient and ultra-stable lithium-ion battery anodes." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A30234.
Full textAbstract:
We propose an effective strategy to engineer a unique kind of porous carbon cuboid with tightly anchored cobalt/cobalt oxide nanoparticles (PCC–CoOx) that exhibit outstanding electrochemical performance for many key aspects of lithium-ion battery electrodes. The host carbon cuboid features an ultra-polar surface reflected by its high hydrophilicity and rich surface defects due to high heteroatom doping (N-/O-doping both higher than 10 atom%) as well as hierarchical pore systems. We loaded the porous carbon cuboid with cobalt/cobalt oxide nanoparticles through an impregnation process followed by calcination treatment. The resulting PCC–CoOx anode exhibits superior rate capability (195 mA h g−1 at 20 A g−1) and excellent cycling stability (580 mA h g−1 after 2000 cycles at 1 A g−1 with only 0.0067% capacity loss per cycle). Impressively, even after an ultra-long cycle life exceeding 10 000 cycles at 5 A g−1, the battery can recover to 1050 mA h g−1 at 0.1 A g−1, perhaps the best performance demonstrated so far for lithium storage in cobalt oxide-based electrodes. This study provides a new perspective to engineer long-life, high-power metal oxide-based electrodes for lithium-ion batteries through controlling the surface chemistry of carbon host materials.
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Khawaja, Danial. "Modeling and optimisation of a rotary kiln reactor for the processing of battery materials." Thesis, KTH, Kemiteknik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-302460.
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Roterugnar är cylindriska kärl som används för att höja materials temperaturer i en kontinuerlig process som kallas för kalcinering. Roterugnar kan tillämpas i olika processer såsom reduktion av oxidmalm samt återvinning av farligt avfall. Fördelen med roterugnar ligger i dess förmåga att hantera råmaterial som sträcker sig från slam till granulära material med en mängd olika partikelstorlekar, och därigenom upprätthålla distinkta miljöer såsom en bädd av fasta partiklar som samexisterar med ett oxiderande fribord. Sex olika bäddbeteende har dokumenterats med avseende på fyllningsgrad samt Froude nummer. Syftet med denna studie var att utveckla en tvådimensionell suspensions modell med CFD genom att använda den kommersiella mjukvaran COMSOL 5.5 för att simulera de två faser, gas och fast, som en blandad fas efter verk av Philips et. al., Physics of Fluids A: Fluid Dynamics 4.1 (1992) 30-40 och Acrivos & Zhang., International Journal Multiphase Flow 20.3 (1994) 579-591. Denna modell undersöktes genom att jämföra den med de dokumenterade flödesregimerna samt genom parameter som partikelstorlek, partikeldensitet och viskositeten hos gas i flödesregimen känd som rullande läge. Dessutom undersöktes temperaturprofilen för den roterande ugnen genom att utforska hur blandningsvariationer av den fasta bädden i den roterande ugnen påverkas av värmeöverföringen när värme tillförs från väggen under rullande läge. Resultaten av den tvådimensionella suspension modellen visade att det var bara möjligt att simulera glidläge korrekt; andra lägen kunde inte beskrivas som dokumenterat i litteraturen. Det indikeras att vilovinkeln och viskösa krafter i den roterande ugnen var låga vilket resulterade i att suspensions modellen inte kunde avbilda exakt de återstående flödesregimerna som dokumenterat. Till exempel avbildades rullningsläget mer likt forsandeläge då partiklarna fall fritt efter höjning av bädden. Partikelstorlek och partikeldensitet har visat sig ha en betydande påverkan på suspensions modellen eftersom de viskösa krafterna blir låga för en partikelstorlek och partikeldensitet under 0,4 mm respektive 1500 kg/m3. Angående gasens viskositet visades det sig att ju närmare värdet 2.055e-3 (Pa*s) den blev desto större blev sedimentationsflödet vilket resulterade i att bäddpartiklarna dras ner och förblir där. Suspensions modellen kunde således simulera en fast och flytande fas och inte en gasfas som avsett. Slutligen visade temperaturanalysen att påverkan av den termiska konduktiviteten var mer signifikant än den specifika värmekapaciteten i intervallet 1 - 50 (W/(m*K)) respektive 300 - 800 (J/(kg*K)) på grund av den tid det tog att nå en homogen temperaturprofil.Rotary kilns are cylindrical vessels used to raise materials temperature in a continuous process known as calcination. Rotary kilns find application in various processes such as reduction of oxide ore and hazardous waste reclamation. The advantage of the rotary kiln lies in its ability to handle feedstock ranging from slurries to granular materials with a variety of particle size, thereby maintaining distinct environments such as a bed of solid particles coexisting with an oxidising freeboard. Six different bed behaviours within the kiln have been documented with respect to the filling degree and Froude number. The aim of this study was to develop a two-dimensional suspension model with CFD by using the commercial software COMSOL 5.5 to simulate the two phases, gas and solid, as a mixed phase, following the works of Philips et. al., Physics of Fluids A: Fluid Dynamics 4.1 (1992) 30-40 and Acrivos & Zhang., International Journal Multiphase Flow 20.3 (1994) 579-591. This model was investigated by comparing it against the documented flow regimes as well as through parameters such as particle size, particle density and viscosity of gas in the flow regime known as rolling mode. In addition, the temperature profile of the rotary kiln was investigated by exploring how the mixture variation of the solid bed within the rotary kiln affects the heat transfer when heat is supplied from the wall during a rolling mode. The results of the two-dimensional suspension model showed that it was only possible to simulate the slipping mode accurately; others mode could not be described as documented in literature. It is indicated that the angle of repose and viscous forces within the rotary kiln were low resulting in the suspension model not being able to accurately depict the remaining flow regimes as documented. For instance, the rolling mode was depicted more as a cataracting mode due to the free fall of particles after elevation of the bed. The particle size and the particle density were found to have a significant impact on the suspension model as the viscous forces became low for a particle size and particle density below 0.4 mm and 1500 kg/m3 respectively. As for the viscosity of gas it was found that the closer it got to the value 2.055e-3 (Pa*s) the sedimentation flux became too large resulting in the bed particles being pulled down and remaining there. Thus, the suspension model could simulate a solid and liquid phase and not a gas phase as intended. Lastly, the temperature analysis revealed that the impact of the thermal conductivity was more significant than the specific heat capacity in the range of 1 - 50 (W/(m*K)) and 300 - 800 (J/(kg*K)) respectively, due to the time it took to reach a homogeneous temperature profile.
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Alves, Dalla Corte Daniel. "Effets du traitement chimique de la surface d'une électrode négative en silicium amorphe pour batterie lithium-ion: étude par spectroscopie infrarouge in situ." Phd thesis, Ecole Polytechnique X, 2013. http://pastel.archives-ouvertes.fr/pastel-00877545.
Full textAbstract:
L'utilisation d'électrodes négatives en silicium est susceptible d'apporter un gain notable en densité de stockage énergétique dans les batteries Li-ion. Toutefois, la réversibilité du cyclage et la stabilité à long terme des électrodes de silicium sont toutes deux dépendantes de l'efficacité de la passivation par la couche interfaciale d'électrolyte solide (SEI) qui se forme à la surface de l'électrode. La spectroscopie infrarouge in situ a été utilisée pour étudier les phénomènes de surface et le volume qui interviennent au cours du cyclage électrochimique du silicium amorphe. Les électrodes ont été préparées par dépôt de couches minces de silicium amorphe hydrogéné sur des prismes utilisés en géométrie de réflexion totale atténuée (ATR), ce qui autorise de suivre l'évolution de l'électrode dans son environnement (électro)chimique. On voit ainsi qu'une couche de passivation de surface se forme très rapidement lors de la première lithiation, se dissous partiellement pendant la délithiation et croit progressivement pendant les cycles successifs. La composition de l'électrolyte joue un rôle majeur sur la composition chimique de la couche SEI. Par ailleurs, les électrodes ont été préalablement soumises à différents traitements chimiques ou électrochimiques permettant le greffage de différentes couches moléculaires à la surface de silicium. Les résultats montrent que les performances électrochimiques du silicium ainsi prétraité sont fortement influencées par la nature chimique, la taille et le taux de recouvrement des espèces greffées. Les monocouches constituées de groupements carboxy-alkyles représentent une solution attractive pour la fonctionnalisation des électrodes de silicium, probablement en raison de leur structure dense, de leur ancrage covalent sur la matière active et leur similarité chimique avec des produits typiques de la couche SEI. Un tel traitement de surface offre à la couche SEI la possibilité de s'ancrer solidement à l'électrode, augmente sa stabilité et améliore ainsi les performances électrochimiques du silicium. D'autre part, le procédé de dépôt chimique en phase vapeur assisté par plasma, utilisé pour obtenir les électrodes en silicium amorphe, permet d'ajouter à la matière active du carbone sous forme de groupes méthyles (CH3). Ceci conduit à une augmentation de la cyclabilité de l'électrode. Le silicium ainsi méthylé présente une amélioration de ses performances électrochimiques en même temps que se développe à sa surface une couche SEI épaisse.
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Bodenes, Lucille. "Etude du vieillissement de batteries lithium-ion fonctionnant à haute température par Spectroscopie Photoélectronique à rayonnement X (XPS)." Thesis, Pau, 2012. http://www.theses.fr/2012PAUU3050/document.
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Les accumulateurs lithium-ion occupent aujourd’hui une place prédominante dans le domaine du stockage de l’énergie. Leur fonctionnement et les phénomènes impliqués dans leur vieillissement sont relativement bien connus, aux températures d’utilisation proches de la température ambiante. Cependant, leur utilisation dans le cadre d’applications dites « haute température », telles que le forage pétrolier, la stérilisation « in situ » ou la géolocalisation, nécessite la levée de certains verrous techniques : la stabilité de l’électrolyte et des liants d’électrodes, la compatibilité électrolyte/séparateur, le vieillissement des matériaux et l’évolution des interfaces. Les accumulateurs sélectionnés pour ces travaux de thèse sont constitués d’un matériau lamellaire de type Li(Ni,Mn,Co)O2 pour l’électrode positive, et de graphite pour l’électrode négative. Afin de décrire les phénomènes de vieillissement associés à une telle utilisation, des analyses de surface ont été menées par Spectroscopie Photoélectronique à rayonnement X sur les électrodes issues d’accumulateurs cyclés à haute température. Ces analyses ont permis de mettre en évidence la dégradation du liant de l’électrode positive et l’évolution des interfaces électrodes/électrolyte à 85 et 120°C, et d’améliorer le choix des composants des batteries pour de meilleures performances à haute températureNowadays, lithium-ion batteries occupy a prominent place in the field of energy storage. Phenomena involved in their aging mechanisms are quite well known for operating temperatures close to room temperature. However, their use at high temperatures for applications such as oil drilling, "in situ" sterilization or freight tracking requires some technical issues to be improved: stability of the electrolyte and electrode binders, compatibility electrolyte / separator, aging of active materials and changes of the interfaces. The batteries selected for this thesis consist of a Li(Ni,Mn,Co)O2 lamellar material at the positive electrode and graphite at the negative electrode. To describe aging phenomena related to high temperature, surface analyzes were carried out by X-ray Photoelectron Spectroscopy on the electrodes of batteries cycled at 85 and 120°C. These analyzes reveal the degradation of the positive electrode’s binder, and the changes of electrodes/electrolyte’s interfaces at high temperature compared to ambient temperature
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Cipolla, Alex. "Etude et amélioration d'accumulateurs à anode de lithium métal en couplant modélisation et caractérisation." Thesis, Université Grenoble Alpes, 2022. https://tel.archives-ouvertes.fr/tel-03689299.
Full textAbstract:
Le lithium métal représente le candidat optimal comme électrode négative dans les batteries au lithium, de par sa capacité théorique élevée (3860 mAh.g-1) et son faible potentiel (-3,04 V ESH). En revanche, l'inconvénient majeur de cette technologie est la formation de dendrites qui peut provoquer des emballements thermiques et des courts-circuits internes. Ces dernières sont également responsables de la durée de vie limitée des cellules lithium métal. La maîtrise de l’électrodépôt du lithium est nécessaire pour le développement de cette technologie haute densité d’énergie et demande une compréhension approfondie de ces phénomènes dendritiques.L’objectif de ce travail est de corréler données expérimentales et modèle afin de comprendre la formation et la croissance des dendrites. Le modèle permet de théoriser les conditions dans lesquelles la croissance des dendrites est facilitée ou évitée, et comment les propriétés des composants de la cellule et la nature de la surface d'électrode peuvent l'affecter, pour suggérer des solutions permettant de réduire les dendrites. D'autre part, la partie expérimentale a pour but de définir un cadre de techniques permettant de déterminer des paramètres fiables à utiliser dans le modèle, et de valider ses tendances.Le modèle continu proposé montre que l’interphase électrode/électrolyte (‘SEI’ pour Solid Electrolyte Interphase) est fondamentale pour évaluer la formation de dendrites et leur croissance, tandis que la définition d’une densité de courant limite n'est pas une condition suffisante pour éviter les dendrites. Cette prise en compte de la SEI dans le modèle permet d’étudier l'influence de ses propriétés mécaniques et électrochimiques sur la croissance dendritique. A partir de la géométrie de surface initiale et des propriétés électrochimiques et mécaniques des composants, le modèle est capable de prédire les conditions qui favorisent la croissance dendritique et de distinguer différentes morphologies de surface. Des dendrites arborescentes (tree-like), moussues (mossy-like) et whiskers sont obtenues selon la densité de courant appliquée. De plus, l'ajout de la mécanique de la SEI permet au modèle de faire la distinction entre la croissance induite par la pointe (tip-induced) et celle induite par la racine (root-induced). À partir des résultats du modèle, une SEI avec une faible résistivité, un coefficient de diffusion élevé et une vitesse de réaction rapide réduit la croissance des dendrites, tandis que la résistance mécanique de la SEI est une arme à double tranchant puisqu’une résistance élevée peut à la fois limiter l'expansion incontrôlée de l’électrode de lithium, mais également stimuler la croissance en cas de fractures.Enfin, les propriétés électrochimiques et mécaniques de la SEI formée dans un électrolyte liquide sont déterminées par spectroscopie d'impédance électrochimique (SIE) et microscopie à force atomique (AFM). L’évolution des spectres d'impédance en fonction du temps permet de caractériser l'évolution de la SEI et de déterminer ses propriétés (épaisseur, coefficient de diffusion et résistivité). D'autre part, l’AFM est utilisée dans le mode spectroscopie de force, à partir duquel il est possible de déterminer des valeurs locales du module de Young de la SEI. La spectrométrie photoélectronique X (XPS), capable d'identifier les composants chimiques à la surface des électrodes, permet de valider les résultats de l’AFM. Enfin, les tendances prédites par le modèle sont validées grâce à la mise au point d’une nouvelle configuration de cellule lithium métal, adaptée à une étude operando de l’électrodépôt du lithium métal par microscopie optique.Ce travail représente une étude complète de la formation et croissance des dendrites dans les accumulateurs au lithium métal. Tandis que seuls les électrolytes liquides sont considérés ici, la méthodologie pourrait tout à fait être étendue aux électrolytes solides et aux revêtements artificiels à la suite de ce travailLithium metal represents the optimal candidate for the negative electrode in lithium batteries, due to its high theoretical capacity (3860 mAh.g-1) and low potential (-3.04 V SHE). On the other hand, the major drawback of this technology is the formation of dendrites, which can cause thermal runaway and internal short-circuits, and are responsible for the limited lifetime of the cells. A dendrite-free lithium deposition is needed to improve this high energy density technology, thus, a deeper understanding of the phenomena and parameters that influence dendrite growth and formation is necessary.The goal of this work is the correlation between experiments and modelling, to understand the formation and the growth of dendrites. The output of the model allows one to theorize in which conditions dendrites growth is boosted or avoided, and how the properties of the cell components and the design of the electrode surface can affect it, to suggest solutions to reduce dendrites. On the other hand, the experimental work has the purpose to define a framework of techniques to find reliable parameters to be used in the model, and to validate the trends of the model.The proposed continuum model shows that the Solid Electrolyte Interphase (SEI) is fundamental to assess dendrites formation and growth, while the definition of a limiting current density is not a sufficient condition to avoid dendrites. Thanks to the introduction of the SEI concept and properties, the proposed model studies the influence of its mechanical and electrochemical properties on the dendritic growth. Starting from the initial surface geometry and the electrochemical and mechanical properties of the cell components, the model is able to predict the conditions that favours dendritic growth and to distinguish different surface morphologies. Tree-like, mossy-like and whisker dendrites are obtained, depending on the applied current density. Moreover, the addition of the mechanics of the SEI allows the model to distinguish between tip-induced growth and root-induced growth. From the model results, it can be concluded that a SEI with low resistivity, high diffusion coefficient and fast reaction rate can reduce dendrite growth, while the mechanical resistance of the SEI is a double-edge sword because it can limit the uncontrolled expansion of the lithium electrode but also boost the root-growth in case of fractures.Electrochemical impedance spectroscopy (EIS) and atomic force microscopy (AFM) techniques are used to find electrochemical and mechanical properties of the SEI formed in liquid electrolytes. By following electrochemical impedance response over time, it is possible to observe SEI evolution and determine mean values for its thickness, its diffusion coefficient and its conductivity. On the other hand, the AFM technique is used in the force spectroscopy mode, from which it is possible to determine local values of the SEI Young’s modulus. X-ray photoelectron spectroscopy (XPS) technique, which is able to identify the chemical components on the electrode surface, helps to validate the results of AFM. Finally, the trends predicted by the model are validated with a novel cell configuration suitable for an operando optical microscopy study of lithium metal stripping/plating.This work represents a comprehensive study on dendrites formation and growth in lithium metal batteries. While it considers only liquid electrolytes so far, as a perspective, it could easily be expanded to solid electrolytes and artificial coatings
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Xia, Changlei. "Biomass-Derived Activated Carbon Through Self-Activation Process." Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849716/.
Full textAbstract:
Self-activation is a process that takes advantage of the gases emitted from the pyrolysis process of biomass to activate the converted carbon. The pyrolytic gases from the biomass contain CO2 and H2O, which can be used as activating agents. As two common methods, both of physical activation using CO2 and chemical activation using ZnCl2 introduce additional gas (CO2) or chemical (ZnCl2), in which the CO2 emission from the activation process or the zinc compound removal by acid from the follow-up process will cause environmental concerns. In comparison with these conventional activation processes, the self-activation process could avoid the cost of activating agents and is more environmentally friendly, since the exhaust gases (CO and H2) can be used as fuel or feedstock for the further synthesis in methanol production. In this research, many types of biomass were successfully converted into activated carbon through the self-activation process. An activation model was developed to describe the changes of specific surface area and pore volume during the activation. The relationships between the activating temperature, dwelling time, yield, specific surface area, and specific pore volume were detailed investigated. The highest specific surface area and pore volume of the biomass-derived activated carbon through the self-activation process were up to 2738 m2 g-1 and 2.209 cm3 g-1, respectively. Moreover, the applications of the activated carbons from the self-activation process have been studied, including lithium-ion battery (LIB) manufacturing, water cleaning, oil absorption, and electromagnetic interference (EMI) shielding.
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Pierre, André Albert Bernard. "Etude des mécanismes de vieillissement des interfaces de batteries Lithium-ion appliquées aux énergies renouvelables." Thesis, Pau, 2015. http://www.theses.fr/2015PAUU3001/document.
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Le développement des énergies renouvelables, telles que le solaire photovoltaïque ou l’éolien, est fortement conditionné par la nature intermittente de ces sources d’énergie. Cette intermittence se traduit par un décalage entre pics de production et de consommation. Le stockage de l’énergie électrique revêt donc un caractère primordial dans la gestion de ce décalage. Pour accomplir cette tâche, la technologie lithium-ion est une bonne candidate parmi les technologies de stockage électrochimique de l’énergie. Mais les applications visées exigent des durées de vie bien supérieures à celles requises pour l’électronique portable ou pour les véhicules électriques. En effet les performances des batteries, notamment en termes de capacité, doivent être préservées pendant des durées de 15 à 20 ans. Cette thèse a alors pour but l’étude des mécanismes de vieillissement à long terme d’accumulateurs Li-ion composés d’oxydes lamellaires Li(NixMnyCo1 x y)O2 à l’électrode positive et de graphite à l’électrode négative, en se focalisant sur les interfaces électrode/électrolyte qui sont le lieu privilégié des mécanismes de vieillissement. Ce travail a été réalisé à l'aide de la spectroscopie photoélectronique à rayonnement X (XPS) et de la spectroscopie d’impédance électrochimique (EIS), deux techniques complémentaires particulièrement bien adaptées à l’étude des interfaces, l'une permettant de sonder les environnements chimiques en extrême surface, l'autre donnant la réponse d’un système à une sollicitation électrique sinusoïdale de fréquence variable. La contrainte importante induite par les durées de vie visées (20 ans) ont conduit à simuler le vieillissement à long terme des batteries en leur faisant subir des sollicitations électrochimiques beaucoup plus importantes que lors d’une utilisation normale Les caractérisations par XPS et EIS ont été systématiquement mises en relation avec l’évolution des performances électrochimiques des batteries considérées. Cette étude a permis d'apporter des améliorations aux batteries pour apporter une meilleure réponse à ces phénomènes de vieillissement en termes de maintien des performances: modification de la formulation des électrodes, des électrolytes, de la nature des matériaux actifs, etcDevelopment of renewable energy sources such as photovoltaic or wind energy is limited by the intermittent nature of these energy sources. This intermittent nature results in the mismatch between production and consumption peaks. As a result, the storage of electrical energy plays an essential role to manage this mismatch. To this aim, lithium-ion technology appears as a good candidate among other ways of electrochemical storage of energy. However the targeted applications require much greater life span than those commonly admitted for portable electronics or electric vehicles. Battery performances, e.g. rechargeable capacity, should be preserved over 15 or 20 years. This PhD thesis aims at studying the long-term aging mechanisms of Li-ion batteries made up of lamellar oxides Li(NixMnyCo1 x y)O2 at the positive electrode and graphite at the negative electrode. We focused on the electrode/electrolyte interfaces which are the major place of aging processes. The work has been performed by X-ray photoelectron spectroscopy (XPS) and electrochemical impedance spectroscopy (EIS), two complementary techniques especially adapted to the study of interfaces, the former giving access to the chemical environments of atoms at the surface, the latter giving the answer of a system to a sinusoidal electric current with various frequencies. An important technical constraint was the difference between the targeted life span for the application (20 years) and the duration of the thesis (3 years). In order to simulate long-term aging the batteries were submitted to electrochemical stress in much harder conditions than in normal use. XPS and EIS characterizations were constantly related to evolution of electrochemical performances of batteries. This study allowed us during the duration of the project to bring improvements to batteries in order to obtain a better response to aging mechanisms regarding retention of electrochemical performances: e.g. change of electrodes or electrolyte formulation, change of active materials composition, etc
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Brown, Shelley. "Diagnosis of the Lifetime Performance Degradation of Lithium-Ion Batteries : Focus on Power-Assist Hybrid Electric Vehicle and Low-Earth-Orbit Satellite Applications." Doctoral thesis, KTH, Tillämpad elektrokemi, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-4722.
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Lithium-ion batteries are a possible choice for the energy storage system onboard hybrid electric vehicles and low-earth-orbit satellites, but lifetime performance remains an issue. The challenge is to diagnose the effects of ageing and then investigate the dependence of the magnitude of the deterioration on different accelerating factors (e.g. state-of-charge (SOC), depth-of-discharge (DOD) and temperature). Lifetime studies were undertaken incorporating different accelerating factors for two different applications: (1) coin cells with a LixNi0.8Co0.15Al0.05O2-based positive electrode were studied with a EUCAR power-assist HEV cycle, and (2) laminated commercial cells with a LixMn2O4-based positive electrode were studied with a low-earth-orbit (LEO) satellite cycle. Cells were disassembled and the electrochemical performance of harvested electrodes measured with two- and three-electrode cells. The LixNi0.8Co0.15Al0.05O2-based electrode impedance results were interpreted with a physically-based three-electrode model incorporating justifiable effects of ageing. The performance degradation of the cells with nickelate chemistry was independent of the cycling condition or target SOC, but strongly dependent on the temperature. The positive electrode was identified as the main source of impedance increase, with surface films having a composition that was independent of the target SOC, but with more of the same species present at higher temperatures. Furthermore, impedance results were shown to be highly dependent on both the electrode SOC during the measurement and the pressure applied to the electrode surface. An ageing hypothesis incorporating a resistive layer on the current collector and a local contact resistance (dependent on SOC) between the carbon and active material, both possibly leading to particle isolation, was found to be adequate in fitting the harvested aged electrode impedance data. The performance degradation of the cells with manganese chemistry was accelerated by both higher temperatures and larger DODs. The impedance increase was small, manifested in a SOC-dependent increase of the high-frequency semicircle and a noticeable increase of the high-frequency real axis intercept. The positive electrode had a larger decrease in capacity and increase in the magnitude of the high-frequency semi-circle (particularly at high intercalated lithium-ion concentrations) in comparison with the negative electrode. This SOC-dependent change was associated with cells cycled for either extended periods of time or at higher temperatures with a large DOD. An observed change of the cycling behaviour in the second potential plateau for the LixMn2O4-based electrode provided a possible kinetic-based explanation for the change of the high-frequency semi-circle.Litiumjonbatteriet är en möjlig kandidat för energilagring i hybridfordon och i satelliter i låg omloppsbana, men än så länge är livslängden på batterierna ett problem. Utmaningen ligger i att kunna förstå hur batteriet åldras genom att utforska hur åldringsprocessen accelereras av faktorer som laddningstillstånd, urladdningsdjup och temperatur. Livslängdsstudier för två olika typer av batterier tänkta för olika applikationer utfördes: (1) knappceller med positiva LixNi0,8Co0,15Al0,05O2-baserade elektroder studerades med en effektstödd (power-assist) hybridcykel från EUCAR, och (2) laminerade kommersiella celler med positiva LixMn2O4-baserade elektroder studerades med en satellitcykel, avsedd för en satellit med låg omloppsbana. Cellerna öppnades och de uttagna elektrodernas elektrokemiska egenskaper utvärderades i två- och tre-elektroduppställningar. Resultaten från elektrokemiska impedansmätningar för den positiva LixNi0,8Co0,15Al0,05O2-baserade elektroden tolkades med hjälp av en fysikalisk tre-elektrod modell som tog hänsyn till de i litteraturen främst föreslagna effekterna av åldring. Prestandadegraderingen av celler med nickelkemi var oberoende av cykel och laddningstillståndet där åldringen skedde, men starkt beroende av temperaturen. Den positiva elektroden visade sig vara den största orsaken till impedansökningen i batteriet. Ytfilmerna på den positiva elektroden hade en sammansättning som var oberoende av laddningstillståndet men beroende av temperaturen. Impedansresultaten från de uttagna elektroderna var starkt beroende av både laddningstillstånd och yttre tryck på elektrodytan. Det visade sig att det var tillräckligt att ta hänsyn till ett resistivt skikt på strömtilledaren och en lokal kontaktresistans mellan kolet och det aktiva materialet (som är beroende av laddningstillståndet) för att anpassa modellen till impedansdata mätt på de uttagna elektroderna. Prestandadegraderingen av celler med mangankemi påskyndades av både högre temperaturer och högre urladdningsdjup. Impedansen ökade något, då både högfrekvenshalvcirkeln och högfrekvensintercepten ändrades. Positiva elektroden hade en större degradering i kapaciteten och en större ökning i magnituden av högfrekvenshalvcirkeln (speciellt vid högre litiumjon koncentrationer i elektroden) jämfört med den negativa elektroden. Denna laddningstillståndsberoende impedans-ökning var kopplad till celler som hade cyklats under en längre tid eller vid en högre temperatur och med ett högt urladdningsdjup. Ökningen i magnituden av högfrekvenshalvcirkeln skulle kunna vara relaterad till kinetiska begränsningar eftersom cyklingsbeteendet vid andra spänningsplatån ändrades samtidigt för de LixMn2O4-baserade elektroderna.
QC 20100621
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Benoit, Charlotte. "Étude des propriétés électrochimiques de nouveaux matériaux nanostructurés à base de fer préparés par chimie douce et utilisables comme électrodes positives d'accumulateurs au lithium." Phd thesis, Université Paris Sud - Paris XI, 2007. http://tel.archives-ouvertes.fr/tel-00257269.
Full textAbstract:
Dans la recherche de nouveaux matériaux pour électrode positive de batterie au lithium, les composés à base de fer permettent un faible coût et une moindre toxicité. Dans cette optique, beta-FeOOH, gamma-FeOOH et LiFePO4 ont été étudiés.Pour les oxyhydroxydes, très peu conducteurs, l'ajout direct de noir d'acétylène ou de nanotubes de carbone (pour améliorer la conductivité électronique) a été développé, cet ajout conduit à une répartition non uniforme du carbone et un isolement des grains, défavorable à l'insertion des ions Li+. Une substitution partielle du fer par le cobalt a été réalisée (amélioration de la conduction ionique). Une stabilisation de la quantité de lithium échangeable est obtenue avec un optimum de 3,6% atomique.
Pour LiFePO4, plusieurs modes de synthèse (voie hydrothermale, mécanochimie ou co-précipitation) ont été utilisés pour obtenir différentes tailles de particules. La conductivité électronique est améliorée par la génération d'une couche de carbone autour des grains par dégradation thermique d'un carbohydrate. Il apparaît que plus les particules sont fines, meilleur est l'insertion de lithium. D'autre part, la présence de quelques défauts cristallins (mis en évidence par magnétisme) est favorable. L'effet de l'enrobage a également été étudié avec différentes sources de carbone (amidon, cellulose, nanotubes de carbone, polyacrilonitrile). Un bon compromis est obtenu avec la cellulose: un caractère fortement sp2 (carbone conducteur), couvrant (bonne percolation des électrons) et homogène (surface non accidentée).
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Morizur, Vincent. "Fonctionnalisation de polymères et applications dans les domaines de l’énergie, de la catalyse, de la cosmétique et de la santé." Thesis, Nice, 2014. http://www.theses.fr/2014NICE4102.
Full textAbstract:
Les polymères sont à l’heure actuelle étudiés dans de nombreux domaines comme la chimie, la biochimie, les nanotechnologies, l'électronique, la médecine ou encore les sciences des matériaux et trouvent des applications dans des domaines comme l’industrie automobile, la chimie fine. L’objectif de cette thèse est de réaliser la fonctionnalisation de polymères et de modifier les propriétés de ces matériaux afin d’envisager des nouvelles applications. Nous nous sommes intéressés à des polymères de la famille des poly(aryle éther) et plus particulièrement au poly(éther éther cétone) (PEEK). Ce polymère est connu pour ses propriétés mécaniques, thermiques, électriques ou encore pour sa résistance aux produits chimiques. Dans le premier chapitre, il est question de la fonctionnalisation des différents polymères de départ par des fonctions chlorures de sulfonyle, acides sulfoniques et sulfonamides. Le second chapitre est consacré à la synthèse et à l’étude électrochimique de nouveaux électrolytes polymériques et à de nouvelles membranes pour d’éventuelles applications dans le domaine des batteries au lithium et au sodium, ainsi que dans le domaine des piles à combustible. Dans un troisième chapitre, la préparation de nouveaux catalyseurs métalliques dérivés d’acides sulfoniques polymériques est discutée. Une étude de l’activité catalytique de ces différents catalyseurs a été réalisée sur la réaction d’acylation de Friedel-Crafts. Le quatrième chapitre est consacré à la préparation de nouveaux matériaux ayant des propriétés optiques intéressantes. Enfin dans un cinquième chapitre, la préparation et l’étude de nouveaux matériaux ayant des propriétés antibactériennes sont exposéesPolymers are now being studied in many fields such as chemistry, biochemistry, nanotechnology, electronics, medicine or material science and have applications in areas such as automotive industry, food industry, fine chemistry. The objective of this thesis is to achieve the functionalization of polymers and modify the properties of these materials in order to consider new applications. We were interested in polymers with the poly(aryl ether) motif, more particularly poly(ether ether ketone) (PEEK). This polymer is known for its mechanical, thermal, electrical properties and for its resistance to chemicals. In the first chapter, we present the functionalization of different polymers by sulfonyl chloride, sulfonic acid and sulfonamide functions. The second chapter is devoted to the synthesis and electrochemical study of novel polymeric electrolytes and new membranes for potential applications in the field of lithium and sodium batteries, as well as in the field of fuel cells. In the third chapter, the preparation of new metal catalysts derived from polymeric sulfonic acids is discussed. A study of the catalytic activity of these different polymeric catalysts was carried out on the Friedel-Crafts acylation reaction. The fourth chapter is devoted to the preparation of new materials with interesting optical properties. Finally, in the fifth chapter, the preparation and the study of new materials with antibacterial properties are reported
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聖, 橋上, and Satoshi Hashigami. "Studies on degradation factors and their mitigation methods of cathode materials for advanced lithium-ion batteries." Thesis, https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13106330/?lang=0, 2019. https://doors.doshisha.ac.jp/opac/opac_link/bibid/BB13106330/?lang=0.
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再生可能エネルギーの大量導入に向けて、電力需給の安定化を目的として蓄電池を用いる電力貯蔵技術に注目が集まっている。現状のリチウムイオン電池(LIB)がベースの先進LIBは250Wh/kgの高エネルギー密度を有し、自動車のみならず電力貯蔵用途としても普及が期待されている。本研究では先進LIB正極材料として期待されるリチウム過剰系正極と高ニッケル三元系正極について容量低下などの劣化要因を明確にして、それら課題に対して正極粒子への酸化物修飾による解決を検討した。The development of energy storage technologies using batteries has attracted much attention to introduce the renewable energy. If we can achieve 250 Wh kg-1 with the advanced LIBs based on the principle of LIB, we can lower the cost of the total energy storage systems while ensuring the safety, and hence the advanced LIBs will accelerate the world-wide spread of large-scale power storage systems. In this thesis, the author focused surface modification of lithium-rich layered ternary transition metal oxide and high-nickel layered ternary transition metal oxide cathode particles with oxides as mitigation methods for capacity fading.
博士(工学)
Doctor of Philosophy in Engineering
同志社大学
Doshisha University
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Johansen, Jonathan Frederick. "Mathematical modelling of primary alkaline batteries." Thesis, Queensland University of Technology, 2007. https://eprints.qut.edu.au/16412/1/Jonathan_Johansen_Thesis.pdf.
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Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge.
We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data.
The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term.
The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour.
The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.
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Johansen, Jonathan Frederick. "Mathematical modelling of primary alkaline batteries." Queensland University of Technology, 2007. http://eprints.qut.edu.au/16412/.
Full textAbstract:
Three mathematical models, two of primary alkaline battery cathode discharge, and one of primary alkaline battery discharge, are developed, presented, solved and investigated in this thesis. The primary aim of this work is to improve our understanding of the complex, interrelated and nonlinear processes that occur within primary alkaline batteries during discharge. We use perturbation techniques and Laplace transforms to analyse and simplify an existing model of primary alkaline battery cathode under galvanostatic discharge. The process highlights key phenomena, and removes those phenomena that have very little effect on discharge from the model. We find that electrolyte variation within Electrolytic Manganese Dioxide (EMD) particles is negligible, but proton diffusion within EMD crystals is important. The simplification process results in a significant reduction in the number of model equations, and greatly decreases the computational overhead of the numerical simulation software. In addition, the model results based on this simplified framework compare well with available experimental data. The second model of the primary alkaline battery cathode discharge simulates step potential electrochemical spectroscopy discharges, and is used to improve our understanding of the multi-reaction nature of the reduction of EMD. We find that a single-reaction framework is able to simulate multi-reaction behaviour through the use of a nonlinear ion-ion interaction term. The third model simulates the full primary alkaline battery system, and accounts for the precipitation of zinc oxide within the separator (and other regions), and subsequent internal short circuit through this phase. It was found that an internal short circuit is created at the beginning of discharge, and this self-discharge may be exacerbated by discharging the cell intermittently. We find that using a thicker separator paper is a very effective way of minimising self-discharge behaviour. The equations describing the three models are solved numerically in MATLABR, using three pieces of numerical simulation software. They provide a flexible and powerful set of primary alkaline battery discharge prediction tools, that leverage the simplified model framework, allowing them to be easily run on a desktop PC.
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Lynch, Thomas. "Surface Modification of LiNi0.5Mn0.3Co0.2O2 Cathode for Improved Battery Performance." Thesis, 2012. http://hdl.handle.net/1969.1/ETD-TAMU-2012-08-11836.
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This thesis details electrical and physical measurements of pulsed laser deposition-applied thin film coatings of Alumina, Ceria, and Yttria-stabilized Zirconia (YSZ) on a LiNi0.5Mn0.3Co0.2O2 (NMC) cathode in a Lithium ion battery. Typical NMC cathodes exhibit problems such as decreased rate performance and an opportunity for increased capacity exists by raising operation voltage beyond the electrolyte stability window. Very thin (~10 nm) coatings of stable oxides provide a pathway to solve both problems. As well, the electrochemical impedance spectra of the uncoated and coated cells were measured after different numbers of cycles to reveal the property variation in the cathode. Further understanding of the mechanism of rate performance enhancement and chemical protection by thin oxide coatings will continue to improve battery capability and open up new applications.
Ceria-coated Li-NMC cells show the best capacity and rate performance in battery testing. Through electrochemical impedance spectroscopy (EIS), the surface film resistance was found to remain stable or even drop slightly after repeated cycling at high voltage. CeO2 is proposed as a coating for Lithium ion battery cathodes owing to its high chemical stability and the demonstrated but not yet well understood electrical conductivity. Alumina-coated cathode shows comparable performance as that of the uncoated cell in the early stage of the test, but through the course of testing the rate capability and recoverable capacity is improved. This is possibly due to Al2O3?s well-known abilities as HF scavenger and chemically inert nature. YSZ-coated cathode performs worse than the uncoated ones in terms of capacity, rate capability, and EIS-related figures of merit. The reason for the poor performance is not yet known, and repeatability tests are under way to verify performance. High voltage cycling reveals no obvious difference in irreversible loss between the coated or uncoated cells. The reason for the lack of distinction could be the relatively small percentage of surface coating compared to the thick doctor-blade processed cathode layer.
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Delone, Nicholas Ryan. "Surface enhanced Raman spectroscopy of olivine type battery cathode LiFePO4." Thesis, 2010. http://hdl.handle.net/2152/ETD-UT-2010-08-1987.
Full textAbstract:
This thesis explores the use of Raman Spectroscopy to study the battery cathode material LiFePO4. Surface Enhanced Raman Spectroscopy (SERS) was incorporated into the study due to fluorescence that traditionally plagues Raman. By imaging LiFePO4 nanoparticles, an understanding can be gained of the complex chemistry taking place when the material is lithiated and delithiated at the nanoscale level and the phase changes of the material that occur during this process. The use of bimetallic (Au/Ag) SERS substrates allowed for more stable substrates with longer shelf life compared single metal Ag substrates. Further tuning of these substrates can be applied to the ever evolving science of energy storage material technology as a way to track phase changes in the material.text
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Pan, Wei-Ting, and 潘威廷. "Surface Modifications of Graphite as Anode in Lithium-ion Battery." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/rv566b.
Full textAbstract:
碩士國立臺南大學
材料科學系碩士班
103
Graphite is one of the common anode materials in lithium ion batteries (LIBs). Through several charging and discharging processes, the charging capacity of LIBs will gradually decrease owing to a collapse of the graphite structure. In the propylene carbonate (PC)-based electrolytes which PC is good at low temperature (< -10oC) performance in lithium ion batteries, but it usually cause solvent co-intercalation leading to poor battery performance. Surface modification of graphite is regarded as an effective method to improve the structure stability and electrochemical properties in their further applications in LIBs. Here, we employed a metal-catalyst-free chemical vapor deposition (MFC-CVD) to modify surface structures of a commercial graphite (Super Fine Mesophase Graphite Powder-SMGP) with acetylene as the carbon source. A unique carbon nanobeads (CNBs) are formed and also coated a carbon layer on the surface of SMGP during the ethylene CVD at mild temperatures (700-900oC). In this work, we systematically study the effects of different ratio of acetylene, reaction temperature, gas flow rate, and reaction time for the surface-modified SMGP. The structural morphologies of the pristine and surface-modified were examined by scanning electron microscope (SEM) and transmission electron microscope (TEM), X-ray diffraction and Raman spectroscopy. Specific surface areas of the samples were analyzed by the Brunauer-Emmett-Teller (BET) method using N2 adsorption. The CNBs average particle size can be controlled by adjusting the reaction gas flow, the CNBs average particle size decrease with increasing the reaction gas flow rate which approximately ranged between 450-150 nm. In the lithium ion battery test, the discharge capacity of treated-SMGP has 153.1 mAh/g but the original-SMGP only has 38.7 mAh/g after 30 cycles. The results indicate the treated-SMGP has better cycle performance than original-SMGP in propylene carbonate electrolyte.
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Hong-Wei, Chan. "Surface Modification of LiMn2O4 Cathode Material in Li-ion Secondary Battery." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-1303200709465750.
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Chan, Hong-Wei, and 詹宏偉. "Surface Modification of LiMn2O4 Cathode Material in Li-ion Secondary Battery." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/46774962150453670583.
Full textAbstract:
博士國立清華大學
材料科學工程學系
95
The surface-modified cathode material in Li-ion battery was synthesized to decrease the side reactions at the interface between the cathode electrode and electrolyte. Among all cathode materials, LiMn2O4 exhibits lower cost, acceptable environmental characteristics and better safety property than other cathode materials. The research focus is aimed to reduce the capacity fading and to enhance the electrochemical performance of spinel LiMn2O4, particularly at high C rate. In this study, the microstructure and electrochemical property in the surface-modified LiMn2O4 were examined and probed. The Li2O-2B2O3 (LBO)-coated LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 were synthesized by either solid-state method or chemical solution method. From the cross section view of LiCuxMn2-xO4-coated LiMn2O4 and LBO-coated LiMn2O4 observed with FE-SEM, it was demonstrated that the lager particles consisted of many smaller ones in the sub-micrometer range. It was argued that LiCuxMn2-xO4-coated LiMn2O4 and LBO-coated LiMn2O4 exhibited two distinct types of surface modification on the basis of the detailed analysis of HRTEM. In addition, the location of Cu in spinel LiCuxMn2-xO4-coated LiMn2O4 was at 16d site revealed by HRTEM. In addition, the electrochemical behavior was examined by using two-electrode coin cells. First of all, the capacity fading can be reduced by the technique of surface modification. The 0.4 wt％ LBO-coated km110 powder retained 93％ of its original discharge capacity after 10 cycles. Furthermore, the capacity fading of 0.3 wt％ LBO-coated Li1+xMn2O4 cathode material was 7％ after 20 cycles, showing much better cycleability than the un-coated one of 15％. The resistance of the LBO-coated Li1+xMn2O4 was also smaller than the un-coated one, indicating that the side reaction at the interface between the cathode and electrode could be diminished. Besides, for the LiCuxMn2-xO4-coated LiMn2O4, the fading rate of LiMn2O4 at 0.2 C was reduced 2.25％ after 10 cycles by surface modification. At higher C rate of 0.5 C, the decrease of fading rate was more obvious at 5.16％ after 25 cycles. The phase transformation of both base LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 during charging at 0.1 C, 0.5 C and 1C rate from 3 V to 4.5 V was confirmed by the in situ synchrotron X-ray diffractometer (in situ XRD). The plateau potential difference between the base LiMn2O4 and LiCuxMn2-xO4-coated LiMn2O4 composite was 50 mV. The decrease of the plateau can be related to the fact that the kinetics of the LiCuxMn2-xO4-coated LiMn2O4 composite cathode material was faster than that of the uncoated material. The XANES of Cu and Mn K-edge spectrum for LiCuxMn2-xO4-coated LiMn2O4 showed that the valence of Cu and Mn was close to Cu2+ and Mn4+, respectively. Furthermore, the oxidation state of Mn was reversibly increased and decreased during charge. The EXAFS was further revealed that the trend of the variation for the bonding length of Mn-O and Mn-M (M=Mn or Cu) was in agreement with the oxidation state of Mn, which was decreased with Li deintercalation, while increased with Li intercalation during cycling. On the basis of the in situ XAS data, it was evidenced that Mn transferred toward Mn4+ to minimize the Jahn-Teller distortion by the technique of surface modification, and thus the better electrochemical property was achieved.
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CHIU, YU-HAN, and 邱宇涵. "Glucose and α-D-Cellobioseoctaacetatemodifiedon silicon surface for Li-ion battery." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/49899483606979849673.
Full textAbstract:
碩士國立臺南大學
綠色能源學科技學系碩士在職專班
105
Air pollution is becoming serious, countries around the world have put forward policies to prevent. Especially, the safety is most important to use in the energy storage system. There are high energy density and volume density for lithium-ion battery, high capacity properties for silicon anode which is potential for the application. The problem of volume expansion form charging and discharging will induce the worse cycle life and safety. Glucose and α-D-Cellobiose octaacetate modified on silicon surface for Li-ion battery to obtain better modification and mixing conditions by test process.The electrochemical performance and material analysis were studied by charge/discharge test, EIS,SEM and XRD. Both of glucose and α-D-Cellobiose octaacetate will be modified successfully. Glucose is the better modifier in this study, which is better than unmodified one including internal resistance, crystal structure during discharging, capacity decay lowest during 100 cycles and improves cycle life.
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Chang, Yu-Hsiu, and 張瑜修. "Surface Modification of Lithium-ion Battery Electrode Materials with Polyvinylidene Difluoride." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/2zj4j9.
Full textAbstract:
碩士國立臺灣大學
化學工程學研究所
107
Lithium-ion battery (LIB) with high energy density, excellent cycle life and high safety is one of the most promising materials currently used in energy storage devices for electric vehicles. Conventional graphite anodes have limited rate capabilities and safety issues. Therefore, development of a highly efficient electrode material with long-term cycle stability, excellent charge and discharge performance, and high safety is quite important for a high-power LIB. Spinel Li4Ti5O12 (LTO) is a competitive anode material for high-power LIB due to its high safety, excellent rate performance and extremely long cycle stability. However, severe gas evolution can be observed during charging and discharging and storage. Then it becomes a major obstacle to the large-scale application of LTO to LIB. It is necessary to improve the severe gassing reaction in LTO batteries because it not only seriously deteriorates their cycle stability, but also causes serious safety problems. So far, some research reports have mentioned gassing phenomena and a few improvement methods for LTO electrodes. However, there is no detailed study on the mechanism of LTO gassing reactions. Therefore, this study attempts to construct an artificial solid-electrolyte-interface (SEI) layer with a polymeric material, polyvinylidene fluoride (PVDF), to improve the gassing problem of LTO. Gas chromatography-mass spectrometry (GC-MS) was used to observe the in-situ gassing phenomenon of LTO half-cells during charge and discharge. Electrochemical performance, pressure change, gas composition, and other data was compared to clarify the actual reaction situation inside. First, we want to directly process the already-made LTO electrode. Therefore, after preparing LTO electrode, PVDF was coated on the LTO electrode by blade-coating. However, constructing a protective layer only on the surface of the electrode did not provide good protection. Therefore, we impregnated the LTO electrode in a solution of PVDF, and with the effect of negative pressure, the gas was extracted, which promoted two-phase-only condition, so that the solution can be closely contact with the surface of LTO, while PVDF was coated as much as possible on each LTO particle. Since PVDF has strong hydrophobicity and dipole moment, it can avoid residual moisture from reacting with the LTO surface. Moreover, when lithium-ions enter the LTO through this interface, the surrounding electrolyte molecules will be isolated, and unable to react with LTO surface. In addition to a series of electrochemical measurements, the results of GC-MS and the pressure monitor were used to analyze the exact effect of the artificial solid-electrolyte-interface (ASEI) on gassing reactions. Then, investigate into the mechanism and the sequence of gassing reactions. The operando in-situ GC-MS data provides the performance of various gas components during charging and discharging, as well as the relative proportions of the gaseous components in the battery. After comparing the trends of the gaseous components, it can be judged which component of the electrolyte dominated the gas reaction. In addition, the pressure monitor can show the effect of this surface modification on gassing problems. Based on the above results, we gradually understand the cause and effect of gas production, and compounds produced during gassing. It will be more easily for researchers to apply LTO to a variety of applications in the future. And facilitate the successful commercialization of this material.