The stability of electrode/electrolyte interfaces in Li-ion batteries is crucial to the performance, lifetime and safety of the entire battery system. In this work, interface processes have been studied in LiFePO4/graphite Li-ion battery cells.  The first part has focused on improving photoelectron spectroscopy (PES) methodology for making post-mortem battery analyses. Exposure of cycled electrodes to air was shown to influence the surface chemistry of the graphite. A combination of synchrotron and in-house PES has facilitated non-destructive interface depth profiling from the outermost surfaces into the electrode bulk. A better understanding of the chemistry taking place at the anode and cathode interfaces has been achieved. The solid electrolyte interphase (SEI) on a graphite anode was found to be thicker and more inhomogeneous than films formed on cathodes. Dynamic changes in the SEI on cycling and accumulation of lithium close to the carbon surface have been observed.    Two electrolyte additives have also been studied: a film-forming additive propargyl methanesulfonate (PMS) and a flame retardant triphenyl phosphate (TPP). A detailed study was made at ambient and elevated temperature (21 and 60 °C) of interface aging for anodes and cathodes cycled with and without the PMS additive. PMS improved cell capacity retention at both temperatures. Higher SEI stability, relatively constant thickness and lower loss of cyclable lithium are suggested as the main reasons for better cell performance. PMS was also shown to influence the chemical composition on the cathode surface. The TPP flame retardant was shown to be unsuitable for high power applications. Low TPP concentrations had only a minor impact on electrolyte flammability, while larger amounts led to a significant increase in cell polarization. TPP was also shown to influence the interface chemistry at both electrodes. Although the additives studied here may not be the final solution for improved lifetime and safety of commercial batteries, increased understanding has been achieved of the degradation mechanisms in Li-ion cells. A better understanding of interface processes is of vital importance for the future development of safer and more reliable Li-ion batteries.

Three-dimensional macroporous structures (‘opals’ and ‘inverse opals’) can be produced by colloidal crystal templating, one of the most intensively studied areas in materials science today. There are several potential advantages of lithium-ion battery electrodes based on inverse opal structures. High electrode surface, easier electrolyte access to the bulk of electrode and reduced lithium diffusion lengths allow higher discharge rates. Highly open structures provide for better mechanical stability to volume swings during cycling. Silicon is one of the most promising anode materials for lithium-ion batteries. Its theoretical capacity exceeds capacities of all other materials besides metallic lithium. Silicon is abundant, cheap, and its use would allow for incorporation of microbattery production into the semiconductor manufacturing. Performance of silicon is restricted mainly by large volume changes during cycling. The objective of this work was to investigate how the inverse opal structures influence the performance of silicon electrodes. Several types of silicon-based inverse opal films were synthesised, and their electrochemical performance was studied. Amorphous silicon inverse opals were fabricated via chemical vapour deposition and characterised by various techniques. Galvanostatic cycling of these materials confirmed the feasibility of the approach taken, since the electrodes demonstrated high capacities and decent capacity retentions. The rate performance of amorphous silicon inverse opals was unsatisfactory due to low conductivity of silicon. The conductivity of silicon inverse opals was improved by crystallisation. Nanocrystalline silicon inverse opals demonstrated much better rate capabilities, but the capacities faded to zero after several cycles. Silicon-carbon composite inverse opal materials were synthesised by depositing a thin layer of carbon via pyrolysis of a sucrose-based precursor onto the silicon inverse opals in an attempt to further increase conductivity and achieve mechanical stabilisation of the structures. The amount of carbon deposited proved to be insufficient to stabilise the structures, and silicon-carbon composites demonstrated unsatisfactory electrochemical behaviour. Carbon inverse opals were coated with amorphous silicon producing another type of macroporous composites. These electrodes demonstrated significant improvement both in capacity retentions and in rate capabilities. The inner carbon matrix not only increased the material conductivity, but also resulted in lower silicon pulverisation during cycling.

Li-ion batteries are not only a technology for the future, they are indeed already the technology of choice for today’s mobile phones, laptops and cordless power tools. Their ability to provide high energy densities inexpensively and in a way which conforms to modern environmental standards is constantly opening up new markets for these batteries. To be able to maintain this trend, it is imperative that all issues which relate safety to performance be studied in the greatest detail. The surface chemistry of the electrode-electrolyte interfaces is intrinsically crucial to Li-ion battery performance and safety. Unfortunately, the reactions occurring at these interfaces are still poorly understood. The aim of this thesis is therefore to increase our understanding of the surface chemistries and stability phenomena at the electrode-electrolyte interfaces for three novel Li-ion battery electrode materials. Photoelectron spectroscopy has been used to study the surface chemistry of the anode material AlSb and the cathode materials LiFePO4 and Li2FeSiO4. The cathode materials were both carbon-coated to improve inter-particle contact. The surface chemistry of these electrodes has been investigated in relation to their electrochemical performance and X-ray diffraction obtained structural results. Surface film formation and degradation reactions are also discussed. For AlSb, it has been shown that most of the surface layer deposition occurs between 0.50 and 0.01 V vs. Li°/Li+ and that cycling performance improves when the lower cut-off potential of 0.50 V is used instead of 0.01 V. For both LiFePO4 and Li2FeSiO4, the surface layer has been found to be very thin and does not provide complete surface coverage. Li2CO3 was also found on the surface of Li2FeSiO4 on exposure to air; this was found to disappear from the surface in a PC-based electrolyte. These results combine to give the promise of good long-term cycling with increased performance and safety for all three electrode materials studied.

Thesis (doctoral)--Université de Paris III, 1976. / Includes indexes. "Bibliographie en langues européennes": p. 537-541. "Bibliographie en langue arabe": p. 542-550.

Submitted by Automa??o e Estat?stica (sst@bczm.ufrn.br) on 2016-10-11T21:52:15Z No. of bitstreams: 1 JoaoBoscoFilho_TESE.pdf: 3755720 bytes, checksum: a14fb4a34797cc81557ba59d2f4891cd (MD5) / Approved for entry into archive by Arlan Eloi Leite Silva (eloihistoriador@yahoo.com.br) on 2016-10-17T19:27:15Z (GMT) No. of bitstreams: 1 JoaoBoscoFilho_TESE.pdf: 3755720 bytes, checksum: a14fb4a34797cc81557ba59d2f4891cd (MD5) / Made available in DSpace on 2016-10-17T19:27:15Z (GMT). No. of bitstreams: 1 JoaoBoscoFilho_TESE.pdf: 3755720 bytes, checksum: a14fb4a34797cc81557ba59d2f4891cd (MD5) Previous issue date: 2010-12-13 / As ci?ncias da sa?de, apoiadas nos argumentos das ci?ncias modernas, assumem em grande parte o conhecimento cient?fico em sua linearidade. Como consequ?ncia desse modelo, a condi??o humana ? reduzida ao dom?nio mec?nico e biol?gico. Essa matriz de conhecimento fomenta um processo de forma??o dos profissionais de sa?de que dificulta uma pr?tica integral, capaz de visualizar a sa?de de forma ampliada, conforme preconizam os princ?pios e diretrizes do Sistema ?nico de Sa?de, atual pol?tica p?blica de sa?de do Brasil. Nesse contexto, torna-se urgente a formula??o de estrat?gias reunificadoras, capazes de construir um olhar ampliado para a forma??o em sa?de. Esta tese tem por suporte as ci?ncias da complexidade e reconhece o homem como parte integrante da natureza, da qual ? dependente. Da? porque, talvez, seja urgente reconhecer que a natureza estendida - para al?m do propriamente humano - ? pr?diga em mensagens para as quais os profissionais da sa?de precisam estar atentos. Identificar e ouvir as li??es do vivo podem ajudar a entender o dom?nio da vida e possibilitar interven??es mais sens?veis no cuidar do humano. A proposi??o de uma nova pr?tica em sa?de foi influenciada pelos macroargumentos filos?ficos, antropol?gicos e epistemol?gicos de Claude L?vi-Strauss. De igual forma, as hip?teses do limite difuso entre vivo e n?o-vivo e de uma comunica??o ampliada entre o homem e todas as coisas do mundo redimensionam na tese concep??es levistraussianas. Henri Atlan, Jean-Marie Pelt e Francisco Lucas da Silva s?o aqui operadores cognitivos que d?o atualidade ?s ideias de L?vi-Strauss. S?o sobretudo essas quatro matrizes de pensamento que comp?em, nesta tese, a estrat?gia de operar o pensamento complexo na ?rea das Ci?ncias da Vida. Autorizar as li??es da natureza viva permite refletir sobre a cegueira e a surdez que s?o impressas na forma??o, acionando canais para a escuta de outras linguagens para religar os conhecimentos e operar efetivamente a integralidade na forma??o em sa?de. / Les sciences de la sant?, soutenues par les arguments des sciences modernes prennent en charge grande partie de la connaissance scientifique dans sa lin?arit?. En cons?quence de ce mod?le, la condition humaine est r?duite au domaine m?canique et biologique. Cet ensemble de connaissance favorise un processus de formation des professionnels de la sant? qui emp?che une pratique int?grale, en mesure de consid?rer la sant? comme un concept large, tel que pr?conisent les principes et les recommandations du Syst?me Unique de Sant?, actuelle politique publique de sant? au Br?sil. Dans ce contexte, il est imp?ratif de formuler des strat?gies r?unifi?es, en mesure de construire un regard ?tendu pour la formation dans le domaine de la sant?. Cette th?se a ?t? soutenue par les sciences de la complexit? et reconna?t l?homme comme partie int?grante de la nature dont il est d?pendent. C?est pourquoi, peut-?tre, il est urgent de reconna?tre que la nature au sens large - au del? de l?esph?re strictement humaine ? est abondante en messages auxquels les professionnels doivent ?tre attentifs. Identifier et entendre les le?ons du vivant cela peut aider l?interlocuteur ? comprendre le domaine de la vie et permettre les interventions les plus sensibles aux soins de l??tre humain. La proposition d?une nouvelle pratique en sant? a ?t? influenc?e par des macroarguments philosophiques, anthropologiques et ?pist?mologiques de Claude L?vi-Strauss. De m?me, les hypoth?ses de la fronti?re prolixe entre le vivant et non-vivant et d?une communication ?largie entre l?homme et toutes les choses du monde, redimensionnent des conceptions l?vi-straussiennes dans la th?se. Henri Atlan, Jean-Marie Pelt et Francisco Lucas da Silva y sont pr?sents en tant qu?agents cognitifs pour relancer les id?es de L?vi-Strauss. Ce sont surtout ces quatre matrices de la pens?e qui composent, dans cette th?se, la strat?gie visant exploiter la pens?e complexe dans le domaine des sciences de la vie. Autoriser les le?ons de la nature vivante, permet de r?fl?chir sur la c?cit? et la surdit? qui sont impr?gn?es ? la formation, d?clenchant les voies pour l??coute de ces autres langages afin de relier les connaissances et proc?der effectivement en faveur de l?int?gralit? de la formation dans le secteur de la sant?.

Titanium dioxide, TiO₂, materials have received much attention in recent years due to their potential use as intercalation negative electrodes for rechargeable lithium-ion batteries. The aim of this doctoral work was to synthesise and characterise new titanium dioxide nanomaterials and to investigate their electrochemical behaviour. Three morphologies of TiO₂(B) phase: micro-sized (bulk), nanowires and nanotubes, were synthesised. All three exhibit properties which make them excellent hosts for lithium intercalation. The nanotubes show the best capability of accommodating lithium in the structure, being able to host over one molar equivalent of lithium at low current rates (5 mA g⁻¹). The lithium insertion mechanism in the TiO₂(B) was studied using powder neutron diffraction. In addition, the nature of the irreversible capacity of the nanotubes was studied and ways of reducing it proposed. Nanotubes of another titanium dioxide polymorph, anatase, were synthesised and characterised. Their electrochemical performance was compared with that of commercially available counterparts with different morphologies and particle sizes. The interrelation between particle size/morphology and electrochemical properties has been established. The insertion of lithium which leads to phase variations was studied using in situ Raman microscopy and neutron powder diffraction. It has been demonstrated that doping of the TiO₂(B) nanotubes with vanadium improves their electronic conductivity which is essential for practical applications. Remarkably good electrochemical performance is exhibited by the 6% V-doped TiO₂(B) nanotubes.

The thesis deals with the influence of cold plasma treatment of seeds such as stress factor to the photosynthesis rate, transpiration and stomatal conductance of brassica oilseed rape (Brassica napus L. var. napus). The theoretical part is focused on the cold plasma, its application and effects on plant physiology, photosynthetic process and description of examined oilseed rape crops. The literature review is followed by the experiment which studies the influence of cold plasma on the physiological processes of plants. The seeds of oilseed rape have been treated with cold plasma in various intervals and cultivated plants were subjected to measuring device Licor Li 6400 XT. The results show that cold plasma treatment of brassica oilseed rape influences the physiological processes depending on the length of exposure and the plant age.

Le tungstène est défini comme “ressource minérale critique” par la Commission Européenne. La province de Jiangxi, située au sud-est de la Chine, dans le bloc Cathaysia, représente 90 % des réserves en tungstène chinoises. Ce travail est basé sur l’étude des gisements hydrothermaux à W-Sn de Maoping et Piaotang, tous deux situés dans le district de Dayu (sud de la province de Jiangxi). Cette thèse a permis de (i) développer des traceurs pétrographiques et minéralogiques de processus minéralisateurs à travers des études paragénétiques détaillées et la géochimie des micas lithinifères et donc d’apporter un modèle impliquant des fluides multiples se chevauchant dans le temps et associés à plusieurs épisodes distincts de mise en place de minéralisations en métaux rares, (ii) définir par l’étude d’inclusions fluides deux processus fluides comme seul responsables de la précipitation de la minéralisation dans ces gisements « géants » : la différenciation magmatique de granites peralumineux et des processus de mélange, et (iii) de développer des approches de datation associés à ces systèmes montrant que la minéralisation en tungstène se met en place aux alentours de 160 Ma, antérieurement à la plupart des âges obtenus sur les minéraux de gangue datés dans cette zone et défini alors une remise à zéro majeure des systèmes isotopiques par de multiples circulations fluides entre 150 et 155 Ma. De plus, les stades post-minéralisations ont pu être définis pour la première fois et révèlent l’implication de magmatisme peralcalin impliqué dans la précipitation de minéralisations à Nb-Ta-Y-REE aux alentours de 130 Ma. A la lumière de cette observation, cette thèse s’est aussi tournée vers le développement de méthodes de datation in situ sur columbo-tantalite / Tungsten is defined as a “critical mineral resource” by the European Commission. The Jiangxi province, located in the southeastern part of China, in the Cathaysia block, represents 90% of the Chinese tungsten resources. This work is based on the study of the Maoping and Piaotang W-Sn hydrothermal deposits located in the Dayu district (southern Jiangxi). This thesis managed to (i) develop mineralogical and petrological tracers of ore-forming processes through detailed paragenetic sequences and geochemistry of Li-micas and shows that multiple overlapping fluids associated to several and distinct rare-metal mineralizing stages, (ii) distinguish by fluid inclusions studies that peraluminous magmatic differentiation and mixing processes are the only prequisite for the formation of these giant deposits, and (iii) develop dating approaches associated to these systems to demonstrate that the W mineralization formed at ca. 160 Ma, prior to most ages obtained on gangue minerals in the area, defining a major resetting of isotopic systems due to multiple fluid circulations around 150-155 Ma. Moreover, post-“silicate-oxide” stages have been defined for the first time and reveal the implication of peralkaline new fluid sources involved in the precipitation of Nb-Ta-Y-REE minerals at ca. 130 Ma. In the light of these results, this thesis gives new developments for in situ direct dating of ore-bearing minerals such as columbo-tantalite

L’étain est une alternative privilégiée en remplacement du carbone graphite comme matériau d’électrode négative dans les batteries Li-ion en raison de son importante capacité théorique spécifique massique de 993 mAh.g-1. Toutefois son expansion volumique lors sa lithiation conduit à sa dégradation au cours du cyclage, diminuant la durée de vie du matériau. Pour pallier à sa pulvérisation, l’utilisation de l’espace inter-granulaire via la nanostructuration du matériau est complétée par l’adjonction d’une matrice carbonée ou d’un autre élément inactif vis-à-vis de la lithiation (utilisation d’alliages intermétalliques). L’objectif de ce travail porte sur l’élaboration de nouveaux procédés de synthèse de nanoparticules d’étain et d’alliage étain-cuivre en milieu liquide ionique. Des nanoparticules de Sn de taille variant de 7 à 45 nm, selon la combinaison cation-anion du liquide ionique et à partir de différents sels métalliques, ont été synthétisées, ainsi qu’un nano-alliage, le composé Cu6Sn5. La taille des nanoparticules est liée à la nature de l’anion bien que le cation présente une interaction privilégiée avec la surface métallique des nanoparticules. Isolées du liquide ionique, les nanoparticules de Sn et Cu6Sn5 montrent une architecture de type cœur-coquille avec un cœur cristallin métallique ou intermétallique et une coquille amorphe d’oxydes d’étain. Les nanoparticules de type Sn@SnOx présentent une capacité spécifique élevée supérieure à 950 mAh.g-1, mettant en lumière un mécanisme de conversion réversible du SnOx surfacique, et celle du nano-alliage Sn-Cu@SnOx est proche de la capacité attendue pour un mécanisme d’alliage, à plus de 530 mAh.g-1. / Tin is a promising alternative to replace graphite carbon as a negative electrode material in Li-ion batteries due to its high specific theoretical mass capacity of 993 mAh.g-1. However, change in volume during lithiation leads to its mechanical degradation during the cycling, and consequently very short life of the material. To overcome this issue, the use of the intergranular space via the nanostructuration of the material combined by the addition of a carbon matrix or other inactive element vs. lithium (intermetallic alloys), which buffers drastically the volume expansion during the lithium alloying process, is employed. The aim of this work is to develop new processes for the synthesis of tin nanoparticles and tin-copper alloys in ionic liquid medium. Sn nanoparticles varying in size from 7 to 45 nm were synthesized, according to the cation-anion combination of the ionic liquid and from different metallic salts, as well as a nano-alloy compound, Cu6Sn5. The size of the nanoparticles is directly related to the nature of the anion although the cation has a privileged interaction with the metal surface of the nanoparticles. Once isolated from the ionic liquid, Sn and Cu6Sn5 nanoparticles have a core-shell architecture with a metallic or intermetallic crystalline core and an amorphous shell of tin oxides. A reversible conversion mechanism of the SnOx from the shell is highlighted for Sn@SnOx nanoparticles, with a high specific capacity of approximately 950 mAh.g-1. Sn-Cu@SnOx nano-alloys have a capacity close to the theoretical for an alloy mechanism at more than 530 mAh.g-1.

abstract: The automotive industry is committed to moving towards sustainable modes of transportation through electrified vehicles to improve the fuel economy with a reduced carbon footprint. In this context, battery-operated hybrid, plug-in hybrid and all-electric vehicles (EVs) are becoming commercially viable throughout the world. Lithium-ion (Li-ion) batteries with various active materials, electrolytes, and separators are currently being used for electric vehicle applications. Specifically, lithium-ion batteries with Lithium Iron Phosphate (LiFePO4 - LFP) and Lithium Nickel Manganese Cobalt Oxide (Li(NiMnCo)O2 - NMC) cathodes are being studied mainly due to higher cycle life and higher energy density values, respectively. In the present work, 26650 Li-ion batteries with LFP and NMC cathodes were evaluated for Plug-in Hybrid Electric Vehicle (PHEV) applications, using the Federal Urban Driving Schedule (FUDS) to discharge the batteries with 20 A current in simulated Arizona, USA weather conditions (50 ⁰C & <10% RH). In addition, 18650 lithium-ion batteries (LFP cathode material) were evaluated under PHEV mode with 30 A current to accelerate the ageing process, and to monitor the capacity values and material degradation. To offset the high initial cost of the batteries used in electric vehicles, second-use of these retired batteries is gaining importance, and the possibility of second-life use of these tested batteries was also examined under constant current charge/discharge cycling at 50 ⁰C. The capacity degradation rate under the PHEV test protocol for batteries with NMC-based cathode (16% over 800 cycles) was twice the degradation compared to batteries with LFP-based cathode (8% over 800 cycles), reiterating the fact that batteries with LFP cathodes have a higher cycle life compared to other lithium battery chemistries. Also, the high frequency resistance measured by electrochemical impedance spectroscopy (EIS) was found to increase significantly with cycling, leading to power fading for both the NMC- as well as LFP-based batteries. The active materials analyzed using X-ray diffraction (XRD) showed no significant phase change in the materials after 800 PHEV cycles. For second-life tests, these batteries were subjected to a constant charge-discharge cycling procedure to analyze the capacity degradation and materials characteristics. / Dissertation/Thesis / Masters Thesis Materials Science and Engineering 2017