This master´s thesis deals with electrodes for lithium-ions batteries based on LiCoO2. The first part of the project is devoted to the characteristics of Li-ion batteries, electrochemical reactions and characteristics of electrode materials. The next part describes an experiment that deals with the effects of NA doping on performance of layered materials for lithium secondary batteries. The materials were measured by cyclic voltammetry, impedance spectroscopy and galvanostatic cycling.

This diploma thesis deals with materials used by production ofcathodes of Lithium-ion batteries. Primary this thesis deals with LiCoO2material and its subsidizing of alkali metals. The first part deals with the charakteristic of Lithium-ion batteries, used materials, possibilities of doping and charging. The practical part concentrates on production of active substance of cathode and doping this substance by sodium and potassium. The methods of evaluation were used galvanostaticcycling and x-ray analysis (XRD).

In order to combat the greenhouse gas emissions from the transportation sector, battery-powered electric vehicles have risen as an alternative that offers a cleaner and more sustainable mode of transportation that reduces reliance on fossil fuels and decreases carbon footprints. The climate scenario goals set by the International Energy Agency - the Net Zero Emissions, Announced Pledges, and Stated Policies Scenarios - revolve around an increased and expeditious demand for electric vehicles, machines that are intrinsically intertwined with battery production. This study focused on the sustainability of the battery's positive electrode (cathode), a critical, material-intensive component. The three different types of cathodes – Layered, Spinel, and Polyanionic – were studied to determine the basics behind their performances. It then became evident that the key ingredients of a battery cathode are lithium, manganese, nickel, iron, and aluminium. These materials were quantified in terms of their production, reserves, and resource numbers. An analysis on the electric vehicle market as a function of the type of battery chemistries was performed to determine how much the best sold and produced EV models consumed in terms of the different materials and how material intensive they were. The future production demand of the ingredients was studied. For lithium, this involved running two polynomial regressions with a demand and production peak in 2050. For manganese and nickel, the compositions of a hypothetical cathode were iterated to match the climate scenario targets, and thus, determine which compositions would meet them. Throughout the investigation, several aspects were uncovered: the current dominant battery chemistry in the EV market is the iron-rich, polyanionic type. However, to compensate for the lower performance of LFP batteries, manufacturers increased cathode size, nullifying the lithium savings. Regarding lithium production, a polynomial growth with a linear decline post the 2050 peak would seamlessly meet the climate scenario goals without exhausting the planetary resources. Manganese proved more sustainable than nickel, although nickel-rich cathodes remain the preferred choice. Manganese-rich cathodes showed the best material efficiency. Significant challenges remain in achieving sustainable EV batteries. The supply chain is highly centralized, and there are limited alternatives to lithium-reliant chemistries. Bereft from economically feasible lithium production methods, the industry is struggling to diversify its technology whilst treading lightly on fragile supply chains. There is comfort in the fact that the availability of these materials is still profuse - but this prosperity may not last if the projected demand is not congruent with the current state of nickel reserves, and if policy and car manufacturers continue to ignore the inherent chemical and physical limitations of the cathode types they prefer. In conclusion, while progress has been made, ensuring the sustainability of EV batteries requires continued innovation and strategic resource management.

Ce travail présente les études électrochimiques et structurales menées sur deux systèmes : P2/O3-NaxMn1-yFeyO2 et O’3-NaxNiO2 utilisés en tant que matériaux d’électrode positive pour batteries Na-ion.Concernant le système P2/O3-NaxMn1-yFeyO2, l’étude par diffraction des rayons X menée in situ pendantla charge de batteries a montré de nombreuses transitions structurales. Que leur structure soit de type P2ou O3, les matériaux présentent une phase distordue pour les taux d’intercalation (x) les plus élevés etune phase très peu ordonnée pour les taux d’intercalation les moins élevés. Entre ces deux étatsd’intercalation, les phases de type P2 présentent moins de transitions que les phases de type O3. Celaentraine de meilleures propriétés électrochimiques pour les phases de type P2 (meilleure capacité endécharge, meilleure rétention de capacité…). Les spectroscopies d’absorption des rayons X et Mössbauerdu 57Fe ont montré que les couples redox Mn4+/Mn3+ et Fe4+/Fe3+ sont impliqués lors du cyclage, à bas ethaut potentiel, respectivement.Concernant O’3-NaNiO2, la diffraction des rayons-X menée in situ pendant la charge de batteriesO’3-NaNiO2//Na a montré de nombreuses transitions structurales O’3 ↔ P’3 résultant du glissement desfeuillets MO2. Ces transitions s’accompagnent de mises en ordre Na+ - lacunes dans le matériau. La tailledes grains a montré avoir un intérêt majeur puisqu’elle influe sur le nombre de phases présentessimultanément dans le matériau. Lorsque la batterie est déchargée, la phase limitante Na≈0.8NiO2 estobservée et empêche le retour à O’3-NaNiO2 / This work concerns the electrochemical and structural studies carried out on two systems used aspositive electrode materials for Na-ion batteries: P2/O3-NaxMn1-yFeyO2 and O’3-NaxNiO2. Concerning theP2/O3-NaxMn1-yFeyO2 systems, in situ X-ray diffraction carried out during the charge of the batteriesshowed that both materials undergo several structural transitions. Both the P2 and O3 phases show adistorted phase for the higher intercalation rates (x) and a poorly ordered phase for the lower ones.Between these two states, P2-based materials exhibit less structural transitions than the O3-based ones.This is correlated to the better electrochemical properties the P2-based materials exhibit (better dischargecapacity, better capacity retention…). X-ray absorption and 57Fe Mössbauer spectroscopies showed thatthe Mn4+/Mn3+ and Fe4+/Fe3+ redox couples are active upon cycling, respectively at low and high voltage.Concerning O’3-NaNiO2, in situ X-ray diffraction carried out during the charge of O’3-NaNiO2//Nabatteries showed several structural transition between O’3 and P’3 structures, resulting from slab glidings.These transitions are accompanied by Na+ - vacancies ordering within the “NaO6” slabs. Upon discharge,the material does not come back to its initial state and, instead, the Na≈0.8NiO2 phase represents themaximum intercalated state. The occurrence of this limiting phase prevents O’3-NaNiO2 to be consideredas an interesting material for real Na-ion applications.

L’utilisation des batteries lithium-ion est dorénavant une technologie de choix pour le secteur automobile notamment pour son utilisation dans les véhicules hybrides et électriques, du fait d’une importante densité d’énergie disponible ainsi que d’une forte densité de puissance nécessaire à la traction d’un véhicule. Cependant, à cause de l’importante énergie embarquée, la sécurité de tels dispositifs doit être renforcée. Il a été rapporté qu’en conditions abusives de température, l’effet cumulé de la dégradation d’un électrolyte utilisant le sel LiPF6 et l’effet catalytique de matériaux d’électrode positive mène à la formation d’espèces organo-fluorées telles que le 2-fluoroéthanol. Ce projet de thèse vise alors à approfondir la compréhension du rôle des matériaux d’électrode positive vis-à-vis de la dégradation d’électrolyte à base de LiPF6, notamment en étudiant la nature des gaz produits en conditions abusives de température. Pour mener à bien ce projet, un dispositif permettant une analyse in situ des gaz formés a été développé. Le rôle de l’eau sur la formation des espèces organo-fluorées fait également l’objet d’une attention toute particulière. L’influence de plusieurs matériaux d’électrode positive sur la nature des produits de dégradation de l’électrolyte a pu être mise en évidence. Ce travail a ainsi permis d’évaluer l’influence de différents paramètres sur la dégradation thermique de l’électrolyte en vue de prédire le choix des différents constituants d’une batterie lithium-ion / The use of lithium-ion batteries is now a technology of choice for the automotive sector especially for its use in hybrid and electric vehicles, due to a high density of energy available as well as a high power density necessary to the traction of a vehicle. However, due to the high on-board energy, the safety of such devices must be enhanced. It has been reported that under abusive thermal conditions the cumulative effect of degradation of a LiPF6-based electrolyte and the catalytic effect of positive electrode materials leads to the formation of fluoro-organic species such as 2-fluoroethanol. This thesis aims to deepen the understanding of the role of positive electrode materials towards the degradation of LiPF6-based electrolyte, in particular by studying the nature of the gases produced under abusive thermal conditions. To carry out this project, a device allowing an in situ analysis of the formed gases has been developed. The role of water on the formation of fluoro-organic species is also the subject of a particular attention. The influence of several positive electrode materials on the nature of the degradation products of the electrolyte has been demonstrated. This work allowed to evaluate the influence of different parameters on the thermal degradation of the electrolyte in order to predict the choice of the various constituents of a lithium-ion battery

This diploma thesis is focused on in-situ analysis of the composition of the negative electrodes of second secondary cells with using X-ray radiation. The first part is dedicated to the theory of lead accumulators, including charging, discharging, battery components and individual degradation mechanisms. The main part of the thesis includes the preparation of electrochemical in situ XRD cells and following measurement of the growth of lead sulphate crystals on the OCV potential. Furthermore, the lead cell was subjected to the measurement of the cyclic voltammetry around the working point of the negative electrodes. From these measurements was evident gradual increase of the lead sulfate crystals. The analysis was supplemented with electron microscopy images. In addition, were evaluated the in-situ particle analysis of the LTO Sigma sample.

This work deals with problems of lithium-ion batteries. In the theoretical part are described electrochemical sources in general and their division. The main representatives of individual types of electrochemical sources are described in more detail. In the next part the thesis focuses specifically on lithium-ion accumulators, their history, electrochemical reactions taking place inside and materials of individual parts of which the accumulator consists. Next part focuses on electron microscopy and its division into scanning and transmission. Basic parts and the principle of operation are described. The practical part is focused on creating a small cell for examination under an electron microscope.

This thesis deals with the development and current issues of Li-ion and Li-S accumulators, especially the separators. In the theoretical part is described history of Li-ion batteries, their properties and materials for the positive electrode. Li-S batteries and their problems are also described in this diploma thesis. In the practical part, electrochemical methods were described, and several separator samples with various modifications were created. These samples were then photographed using an SEM electron microscope and evaluated using electrochemical methods.

The present work deals with the use of manganese oxide as a catalyst for positive electrode of fuel cells. The theoretical part is to analyze the problem of fuel cells, focusing on lowtemperature fuel cells. Are discussed and the methods of measurement and evaluation of properties of manganese oxide layer. The practical part deals with doping electrolytic manganese dioxide salts of divalent metals and monitoring their behavior in the cyclic voltammetry by the EQCM method.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第18607号 / エネ博第303号 / 新制||エネ||62(附属図書館) / 31507 / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 萩原 理加, 教授 佐川 尚, 教授 平藤 哲司 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM