Chemo-mechanics studies the material behavior and phenomena at the interface of mechanics and chemistry. Material failures due to coupled chemo-mechanical effects are serious roadblocks in the development of renewable energy technologies. Among the sources of renewable energies for the mass market, hydrogen and lithium-ion battery are promising candidates due to their high efficiency and easiness of conversion into other types of energy. However, hydrogen will degrade material mechanical properties and lithium insertion can cause electrode failures in battery owing to their high mobilities and strong chemo-mechanical coupling effects. These problems seriously prevent the large-scale applications of these renewable energy sources. In this thesis, the atomistic and continuum modeling are performed to study the chemical-mechanical failures. The objective is to understand the hydrogen embrittlement of grain boundary engineered metals and the lithium insertion-induced fracture in alloy electrodes for lithium-ion batteries. Hydrogen in metallic containment systems such as high-pressure vessels and pipelines causes the degradation of their mechanical properties that can result in sudden catastrophic fracture. A wide range of hydrogen embrittlement phenomena was attributed to the loss of cohesion of interfaces (between grains, inclusion and matrix, or phases) due to interstitially dissolved hydrogen. Our modeling and simulation of hydrogen embrittlement will address the question of why susceptibility to hydrogen embrittlement in metallic materials can be markedly reduced by grain boundary engineering. Implications of our results for efficient hydrogen storage and transport at high pressures are discussed. Silicon is one of the most promising anode materials for Li-ion batteries (LIB) because of the highest known theoretical charge capacity. However, Si anodes often suffer from pulverization and capacity fading. This is caused by the large volume changes of Si (~300%) upon Li insertion/extraction close to the theoretical charging/discharging limit. In particular, large incompatible deformation between areas of different Li contents tends to initiate fracture, leading to electro-chemical-mechanical failures of Si electrodes. In order to understand the chemo-mechanical mechanisms, we begin with the study of basic fracture modes in pure silicon, and then study the diffusion induced deformation and fracture in lithiated Si. Results have implications for increasing battery capacity and reliability. To improve mechanical stability of LIB anode, failure mechanisms of silicon and coated tin-oxide nanowires have been studied at continuum level. It's shown that anisotropic diffusivity and anisotropic deformation play vital roles in lithiation process. Our predictions of fracture initiation and evolution are verified by in situ experiment observations. Due to the mechanical confinement of the coating layers, our study demonstrates that it is possible to simultaneously control the electrochemical reaction rate and the mechanical strain of the electrode materials through carbon or aluminum coating, which opens new avenues of designing better lithium ion batteries. This thesis addresses the nano-chemo-mechanical failure problems in two green energy-carrier systems toward improving the performance of Li-ion battery anode and hydrogen storage system. It provides an atomistic and continuum modeling framework for the study of chemo-mechanics of advanced materials such as nano-structured metals and alloys. The results help understand the chemical effects of impurities on the mechanical properties of host materials with different metallic and covalent bonding characteristics.

Nous avons mis au point une approche novatrice pour la synthèse d’un matériau de cathode pour les piles lithium-ion basée sur la décomposition thermique de l’urée. Les hydroxydes de métal mixte (NixMnxCo(1-2x)(OH)2) ont été préparés (x = 0.00 à 0.50) et subséquemment utilisés comme précurseurs à la préparation de l’oxyde de métal mixte (LiNixMnxCo(1-2x)O2). Ces matériaux, ainsi que le phosphate de fer lithié (LiFePO4), sont pressentis comme matériaux de cathode commerciaux pour la prochaine génération de piles lithium-ion. Nous avons également développé un nouveau traitement post-synthèse afin d’améliorer la morphologie des hydroxydes. L’originalité de l’approche basée sur la décomposition thermique de l’urée réside dans l’utilisation inédite des hydroxydes comme précurseurs à la préparation d’oxydes de lithium mixtes par l’intermédiaire d’une technique de précipitation uniforme. De plus, nous proposons de nouvelles techniques de traitement s’adressant aux méthodes de synthèses traditionnelles. Les résultats obtenus par ces deux méthodes sont résumés dans deux articles soumis à des revues scientifiques. Tous les matériaux produits lors de cette recherche ont été analysés par diffraction des rayons X (DRX), microscope électronique à balayage (MEB), analyse thermique gravimétrique (ATG) et ont été caractérisés électrochimiquement. La performance électrochimique (nombre de cycles vs capacité) des matériaux de cathode a été conduite en mode galvanostatique. / We have developed a novel approach to the synthesis of cathode materials for lithium-ion batteries, based on the thermal decomposition of urea. Mixed metal hydroxides (NixMnxCo(1-2x)(OH)2), x = 0.00 to 0.50, were prepared and subsequently used as precursor for lithiated mixed metal oxide (LiNixMnxCo(1-2x)O2). These materials along with lithium iron phosphate (LiFePO4) are being considered as cathode materials for the next generation of lithium-ion batteries. We have also developed new post-synthetic treatments on the hydroxides in order to enhance the morphology, which would result in improved electrode properties. The novelty of this thesis is that for the first time mixed metal hydroxides for use as precursors for lithium mixed oxides have been prepared via a uniform precipitation technique from solution. In addition, we have proposed new treatments techniques towards the more traditional synthesis method for mixed metal hydroxides. The results obtained from these two methods are summarized within two articles that were recently submitted to peer-reviewed journals. Within this thesis, all materials were analyzed with X-ray diffraction (XRD), scanning electron microscopy (SEM), thermal gravimetric analysis (TGA) and electrochemical measurements. The electrochemical performance (capacity vs cycle number) of the cathode materials were tested galvanostatically.

The popularity of the internal combustion engine (ICE) vehicles has contributed to global warming problem and degradation of air quality around the world. Furthermore, the vehicles??? massive demand on gas has played a role in the depletion of fossil fuel reserves and the considerable rise in the gas price over the past twenty years. Those existing challenges force the auto-industry to move towards the technology development of vehicle electrification. An electrified vehicle is driven by one or more electric motors. And the electricity comes from the onboard energy storage system (ESS). Currently, no single type of green energy source could meet all the requirements to drive a vehicle. A hybrid energy storage system (HESS), as a combination of battery and ultra-capacitor units, is expected to improve the overall performance of vehicles??? ESS. This thesis focuses on the design of HESS and the development of a HESS prototype for electric vehicles (EVs) and hybrid electric vehicles (HEVs). Battery unit (BU), ultra-capacitor unit (UC) and a DC/DC converter interfacing BU and UC are the three main components of HESS. The research work first reviews literatures regarding characteristics of BU, UC and power electronic converters. HESS design is then conducted based on the considerations of power capability, energy efficiency, size and cost optimization. Besides theoretical analysis, a HESS prototype is developed to prove the principles of operation as well. The results from experiment are compared with those from simulation.

Die vorliegende Arbeit liefert einen Beitrag zum Verständnis der elektrochemischen Prozesse an der Elektrodengrenzfläche und im Festkörper graphitischer Anoden für Lithium-Ionen-Batterien. Der Zusammenhang zwischen den intrinsischen Eigenschaften des Aktivmaterials und den resultierenden Eigenschaften von Kompositelektroden stand dabei im Fokus der Untersuchungen. Die Temperaturabhängigkeit von Materialeigenschaften (Diffusionskoeffizient, Austauschstromdichte) und Elektrodeneigenschaften (Verhalten unter Strombelastung) wurde in einem Bereich von 40 °C bis -10 °C erfasst. Dazu werden elektrochemische Charakterisierungsmethoden aus der Literatur vorgestellt und hinsichtlich ihrer Gültigkeit für die Anwendung an realen Elektroden evaluiert. Die elektrochemisch aktive Oberfläche wurde bestimmt und stellte sich als ausschlaggebender Parameter für die Bewertung der Elektrodenprozesse heraus. Auf Basis korrigierter Elektrodenoberflächen konnten Austauschstromdichten für die konkurrierenden Prozesse Lithium-Interkalation und -Abscheidung ermittelt werden. Zusammen mit Kennwerten zur Keimbildungsüberspannung für Lithium-Abscheidung flossen die ermittelten Kennwerte in eine theoretische Berechnung des Zellstroms ein. Es konnte gezeigt werden, dass die Lithium-Abscheidung kinetisch deutlich gegenüber der Lithium-Interkalation bevorzugt ist, nicht nur bei niedriger Temperatur. Die Übertragbarkeit wissenschaftlicher Grundlagenexperimente auf kommerzielle Systeme war bei allen Versuchen Gegenstand der Untersuchungen. In einem separaten Beispiel einer Oberflächenmodifikation mit Zinn wurde diese Problematik besonders verdeutlicht. Zusätzlich wurde die parasitäre Abscheidung von Lithium auf graphitischen Anoden hinsichtlich der Nachweisbarkeit und Quantifizierung evaluiert. Hierfür wurde eine neue Untersuchungsmethode im Bereich der Lithium-Ionen-Batterie zur besseren Detektion von Lithium-Abscheidung und Grenzflächen-Morphologie mittels Elektronenmikroskopie entwickelt. Die Osmiumtetroxid (OsO4) Färbung ermöglichte eine deutliche Verbesserung des Materialkontrasts und erlaubte somit eine gezielte Untersuchung von graphitischen Anoden nach erfolgter Lithium-Abscheidung. Darüber hinaus konnte die selektive Reaktion des OsO4 für eine genauere Betrachtung der Solid Electrolyte Interphase genutzt werden. Eine Stabilisierung der Proben an Luft und im Elektronenstrahl konnte erreicht werden. / This work sheds light on the electrochemical processes occurring at commercially processed graphitic anodes. It raises the question whether values published in literature for mostly ideal electrode systems can be readily taken for simulation and design of real electrodes in high-energy cells. A multiple step approach is given, evaluating different methods to determine electrode and material properties independently. The electrochemically active surface area was shown to be a crucial parameter for the calculation of electrode kinetics. Using exchange current densities corrected for the electrode surface area, the overall charging current in a cell could be calculated. The resulting part of lithium deposition in the charging process is strikingly high, not only at low temperatures. To further investigate lithium deposition in terms of morphology and quantity, a method was developed for graphitic anodes. Osmium tetroxide (OsO4) staining serves well as a tool to strongly increase material contrast in electron microscopy. Thus lithium dendrites could be made visible in an unprecedented manner. Furthermore, the selective chemical reaction of osmium tetroxide allows for a better investigation of the multi-layer solid electrolyte interphase as was shown in transmission electron microscopy. Using the staining method, a stabilization of the sample under air and in the electron beam could be achieved.

Les estimations précises des états de charge (« State of Charge » - SoC) et de santé (« State of Health » - SoH) des batteries au lithium sont un point crucial lors d’une utilisation industrielle de celles-ci. Ces estimations permettent d’améliorer la fiabilité et la robustesse des équipements embarquant ces batteries. Cette thèse CIFRE est consacrée à la recherche d’algorithmes de détermination de l’état de santé de batteries lithium-ion, en particulier de chimie Lithium Fer Phosphate (LFP) et Lithium Manganèse Oxyde (LMO).Les recherches ont été orientées vers des solutions de détermination du SoH directement embarquables dans les calculateurs des véhicules électriques. Des contraintes fortes de coût et de robustesse constituent ainsi le fil directeur des travaux.Or, si la littérature actuelle propose différentes solutions de détermination du SoH, celles embarquées ou embarquables sont encore peu étudiées. Cette thèse présente donc une importante revue bibliographique des différentes méthodes d’estimation du SoH existantes, qu’elles soient embarquables ou non. Le fonctionnement détaillé ainsi que les mécanismes de vieillissement d’une batterie lithium-ion sont également explicités.Une partie majoritaire des travaux est consacrée à l’utilisation de l’analyse incrémentale de la capacité (« Incremental Capacity Analysis » - ICA) en conditions réelles, c’est-à-dire avec les niveaux de courant présents lors d’un profil de mission classique d’un véhicule électrique, avec les mesures disponibles sur un BMS (« Battery Management System ») industriel et avec les contraintes de robustesses associées, notamment une gamme étendue de température de fonctionnement. L’utilisation de l’ICA pour déterminer la capacité résiduelle de la batterie est mise en œuvre de façon totalement innovante et permet d’obtenir une grande robustesse aux variations des conditions d’utilisation de la batterie.Une seconde méthode est, elle, dédiée à la chimie LMO et exploite le fait que le potentiel aux bornes de la batterie soit représentatif de son état de charge. Un compteur coulométrique partiel est ainsi proposé, intégrant une gestion dynamique des bornes d’intégration en fonction de l’état de la batterie.A l’issue des travaux, une méthode complète et précise de détermination du SoH est disponible pour chacune des chimies LFP et LMO. La détermination de la capacité résiduelle de ces deux familles de batteries est ainsi possible à 4 % près. / Accurate lithium-ion battery State of Charge (SoC) and State of Health (SoH) estimations are nowadays a crucial point, especially when considering an industrial use. These estimations enable to improve robustness and reliability of hardware using such batteries. This thesis focuses on researching lithium-ion batteries state of health estimators, in particular considering Lithium Iron Phosphate (LFP) and Lithium Manganese Oxide (LMO) chemistries.Researches have been targeted towards SoH estimators straight embeddable into electric vehicles (EV) computers. Cost and reliability constraints are thus the main guideline for this work.Although existing literature offers various SoH estimators, those who are embedded or embeddable are still little studied. A complete literature review about SoH estimators, embedded or not, is therefore proposed. Lithium-ion batteries detailed operation and ageing mechanisms are also presented.The main part of this work is dedicated to Incremental Capacity Analysis (ICA) use with electric vehicle constraints, such as current levels available with a typical EV mission profile or existing measurements on the Battery Management System (BMS). Incremental Capacity Analysis is implemented in an innovative way and leads to a remaining capacity estimator with a high robustness to conditions of use variations, including an extended temperature range.A second method, dedicated to LMO chemistry, take advantage of the fact that the battery potential is representative of its state of charge. Partial Coulomb counting is thus performed, with a dynamic management of integration limits, depending on the battery state.Outcomes of this work are two complete and accurate SoH estimators, one for each chemistry, leading to a remaining capacity estimation accurate within 4 %.

Le développement futur des véhicules électriques est lié à l’amélioration des performances des batteries qu’ils contiennent. Parallèlement aux recherches sur les nouveaux matériaux ayant des performances supérieures en termes d'énergie, de puissance, de durabilité et de coût, il est nécessaire développer des outils de modélisation pour : (i) simuler l'intégration de la batterie dans la chaine de traction et (ii) pour le système de gestion de la batterie, afin d'améliorer la sécurité et la durabilité. Soit de façon directe (par exemple, la prévention de surcharge ou de l’emballement thermique) soit de façon indirecte (par exemple, les indicateurs de l’état de charge). Les modèles de batterie pourraient aussi être utilisés pour comprendre les phénomènes physiques et les réactions chimiques afin d'améliorer la conception des batteries en fonction des besoins de l’utilisateur et de réduire la durée des phases de test. Dans ce manuscrit, un des modèles les plus communs décrivant les électrodes poreuses des batteries au lithium-ion est revisité. De nombreuses variantes dans la littérature s’inspirent directement du travail mené par le professeur J. Newman et son équipe de chercheurs à l’UC Berkeley. Pourtant relativement peu d’études analysent en détail les capacités prédictives de ce modèle. Dans ce travail, pour étudier ce modèle, toutes les grandeurs physiques sont définies sous une forme adimensionnelle, comme on l'utilise couramment dans la mécanique des fluides : les paramètres qui agissent de manière identique ou opposée sont regroupés et le nombre total de paramètres du modèle est considérablement réduit. Cette étude contient une description critique de la littérature incluant le référencement des paramètres du modèle développé par le groupe de Newman et les techniques utilisées pour les mesurer, ainsi que l’écriture du modèle dans un format adimensionnel pour réduire le nombre de paramètres. Une partie expérimentale décrit les modifications de protocoles mis en œuvre pour améliorer la reproductibilité des essais. Les études effectuées sur le modèle concernent d’une part l’identification des états de lithiation dans la cellule avec un attention particulière sur la précision obtenue, et enfin une prospection numérique pour examiner l’influence de chaque paramètre sur les réponses de la batterie en décharge galvanostatique puis en mode impulsion et relaxation. / The future development of electric vehicles is mostly dependent of improvements in battery performances. In support of the actual research of new materials having higher performances in terms of energy, power, durability and cost, it is necessary to develop modeling tools. The models are helpful to simulate integration of the battery in the powertrain and crucial for the battery management system, to improve either direct (e.g. preventing overcharges and thermal runaway) and indirect (e.g. state of charge indicators) safety. However, the battery models could be used to understand its physical phenomena and chemical reactions to improve the battery design according with vehicles requirements and reduce the testing phases. One of the most common model describing the porous electrodes of lithium-ion batteries is revisited. Many variants available in the literature are inspired by the works of prof. J Newman and his research group from UC Berkeley. Yet, relatively few works, to the best of our knowledge, analyze in detail its predictive capability. In the present work, to investigate this model, all the physical quantities are set in a dimensionless form, as commonly used in fluid mechanics: the parameters that act in the same or the opposite ways are regrouped and the total number of simulation parameter is greatly reduced. In a second phase, the influence of the parameter is discussed, and interpreted with the support of the limit cases. The analysis of the discharge voltage and concentration gradients is based on galvanostatic and pulse/relaxation current profiles and compared with tested commercial LGC cells. The simulations are performed with the software Comsol® and the post-processing with Matlab®. Moreover, in this research, the parameters from the literatures are discussed to understand how accurate are the techniques used to parametrize and feed the inputs of the model. Then, our work shows that the electrode isotherms shapes have a significant influence on the accuracy of the evaluation of the states of charges in a complete cell. Finally, the protocols to characterizes the performance of commercial cells at different C-rates are improved to guarantee the reproducibility.

The present thesis demonstrates and discusses polymeric ion and mixed ion-electron conductors for rechargeable batteries based on lithium viz. lithium-ion and lithium-sulphur batteries. The proposed polymer ion conductors in the thesis are discussed primarily as potential alternatives to conventional liquid and solid-crystalline electrolytes in lithium-ion batteries. These discussions are part of Chapters 2-4. On the other hand, the polymer based mixed ion-electron conductor is demonstrated as a novel electrode for lithium-Sulphur battery in Chapter 5. Possibility of application of polymer ion conductors is discussed in the context of Li-S battery in Chapter 6. A distinct correlation between the physical properties and electrochemical performance of the proposed conductors is highlighted in detail in this thesis. Systematic investigation of the ion transport mechanism in the polymeric ion conductors has been carried out using various spectroscopic techniques at different time and length scales. Such detailed investigations demonstrate the key structural and physical parameters for design of alternative polymer conductors for rechargeable batteries. Though the thesis discusses the various polymeric conductors in the context of lithium-based batteries, it is strongly felt that the design strategies are equally likely to be beneficial for different battery chemistries as well as for other electrochemical generation and storage devices. A brief discussion of the contents and highlights of the individual chapters are described below: The thesis comprises of six Chapters. Chapter 1 briefly reviews the important developments and materials of lithium-based batteries, with specific focus on Li-ion and Li-S batteries. It starts with discussions on different types of liquid, solid crystalline and solid-like electrolytes. Their materials characteristics, advantages and disadvantages are discussed in the context of secondary batteries such as lithium-ion and lithium-sulphur batteries. As prospective alternative electrolytes polymer based soft matter electrolytes are discussed in detail. Special emphasis is given to the recent developments in polymer electrolytes and their ion conduction mechanism, which are central themes to this thesis. The importance of investigation of charge transport, typically ion, on electrochemical processes is also briefly discussed in Chapter 1. A brief discussion about the characteristics, materials and non-trivialities of the electrochemical storage process in Li-S battery is also reviewed. Chapter 2A demonstrates a binary polymer physical network based gel (PN-x) electrolyte, comprising of an ionic liquid confined inside a binary polymer system for electrochemical devices such as secondary batteries. The synthesis, physical property and electrochemical performances are studied as a function of content of one of the polymers in this Chapter. A physical network of two polymers with different functional groups leads to multiple interesting consequences. The polymer physical network characteristics determine all physical properties including electrochemical property of the ionic liquid integrated PN based GPE. The conductivities of the proposed gel are nearly an order in magnitude higher than the unconfined ionic liquid electrolyte and displays good dimensional stability and electrochemical performance in a separator-free battery configuration. The ac-impedance spectroscopy, steady shear viscosity measurement, dynamic rheology are employed to study physical properties of the proposed gel polymer electrolyte. Chapter 2B discusses the detailed investigations of the ion transport mechanism of the gel polymer electrolyte, as discussed in Chapter 2A. Ion conduction mechanism is investigated in the light of ion diffusion and solvent dynamics of the entrapped ionic liquid inside the polymer. The studies reveal a heavy influence of network characteristics on the ion conduction mechanism. The influence of solvent dynamics on the ion transport is drastically altered by polymer physical network. Consequently, a drastic change in the ion mobility and nature of predominant charge carrier is observed in the polymer physical network based gel electrolyte. A clear transformation from dual ion conductivity to a predominantly anion conductivity is observed on going from single polymer to a dual polymer network. The spectroscopic tools such as pulsed field gradient nuclear magnetic resonance (PFG–NMR), Brillouin light scattering spectroscopy, ac-impedance spectroscopy, FT-Raman and FTIR spectroscopy were used to elucidate the ion transport mechanism in the Chapter. Chapter 3 demonstrates a simple design strategy of gel polymer electrolyte comprising of a lithium salt (lithium bis(trifluoromethanesulfonyl) imide, LiTFSI) solvated by two plastic crystalline solvents, one a solid (succinonitrile, abbreviated as SN) and another a (room temperature) ionic liquid (1-butyl-1-methyl-pyrrolidinium bis(trifluoromethane sulfonyl) imide, (abbreviated as IL) confined inside a linear network of poly(methyl methacrylate) (PMMA). The concentration of the IL component determines the physical properties of the unconfined electrolyte and when confined inside the polymer network in gel polymer electrolyte. Intrinsic dynamics of one plastic crystal influences the conduction mechanism of gel polymer electrolytes. The enhanced disordering in the plastic phase of succinonitrile by IL doping alters both the local ion environment and viscosity. The proposed plastic crystal electrolytes show predominantly anion conduction (tTFSI ≈ 0.5) however, lithium transference number (tLi ≈ 0.2) is nearly an order higher than the ionic liquid electrolyte (IL-LiTFSI) (tLi ≈ 0.02-0.06), discussed in Chapter 2. The gel polymer electrolyte displayed high mechanical compliability, stable Li-electrode | electrolyte interface, low rate of Al corrosion and stable cyclability. The promising electrochemical performance further justifies simple strategy of employing mixed physical state plasticizers to tune the physical properties of polymer electrolytes requisite for application in rechargeable batteries. Chapter 4A proposes a novel liquid dendrimer–based single ion conducting liquid electrolyte as potential alternative to conventional molecular liquid solvent–salt solutions and conventional solid polymer electrolytes for rechargeable batteries, sensors and actuators. The physical properties are investigated as a function of peripheral functionalities in the first generation poly(propyl ether imine) (G1-PETIM)–lithium salt complexes. The change in peripheral group simultaneously affects the effective physical properties viz. viscosity, ionic conductivity, ion diffusion coefficients, transference numbers and also the electrochemical response. The specific change from ester (–COOR) to cyano (–CN) terminated peripheral group resulted in a remarkable switch over from a high cation (tLi+ = 0.9 for –COOR) to a high anion (tPF6- = 0.8 for –CN) transference number. Chapter 4B presents an analysis of the frequency dependent ionic conductivity of single ion dendrimer conductors by using time temperature scaling principles (TTSPs) and dielectric modeling of the electrode polarization. The TTSP provides information on the salt dissociation and number density of mobile charges and hence provides direct insights into the ion conduction mechanism. Summerfield and Baranovskii–Cordes scaling laws, which are well known TTSPs, have been applied to analyze the ion conductivity. The electrode polarization, which quantifies the number density of mobile charges and ionic mobility, is studied using Macdonald-Coelho model of electrode polarization. The combination of these two theoretical investigations of the experimental data emanating from one technique i.e. ac– impedance spectroscopy, predicts independently the contributions of the effect of mobile ion charges and ionic mobility to ion conduction mechanism. In Chapter 5 focus shifts from polymer ion conductors to polymer mixed ion-electron conductor. The polymer mixed ion-electron conductor is demonstrated as a novel electrode material for Li-S battery. A simple strategy to overcome the challenges towards practical realization of a stable high performance Li–S battery is discussed. A soft mixed conducting polymeric network is utilized to configure sulphur nanoparticle. The soft matter network provides efficient and distinct pathways for lithium and electron conduction simultaneously. A lithiated polyethylene glycol (PEG) based surfactant tethered on ultra-small sulphur nanoparticles and wrapped up with polyaniline (PAni) (abbreviated as S-MIEC) is demonstrated here as an exceptional cathode for Li–S batteries. The S-MIEC is characterized by several methods: powder-X-ray diffraction (PXRD), thermo gravimetric analysis (TGA), fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), ac-impedance spectroscopy and dc current-voltage measurements are performed to evaluate conductivity of S-MIEC cathode. Electrochemical studies such as cyclic voltammetry, galvanostatic charge-discharge cycling, galvanostatic intermittent titration (GITT) are performed to demonstrate feasibility of S-MIEC in the Li–S battery performance. Chapter 6 provides a brief summary of the work carried out as part of this thesis and also demonstrates the future perspective of the present work. Potential of the polymer physical network based gel polymer electrolytes, which are discussed in Chapter 2A-B for lithium-ion batteries, are demonstrated in Li-S battery. The proposed polymer physical network confines higher order lithium polysulfides (typically Li2S8) dissolved in tetraethylene glycol dimethyl ether (TEGDME) based electrolyte (TEGDME-1M LiTFSI). The three dimensional polymer network is proposed to be formed by physical blending of the poly(acrylonitrile) (PAN) with the copolymer of AN and poly(ethylene glycol) methyl ether methacrylate (PEGMA), [ P(AN–co–PEGMA)]. We extend here the similar synthetic approaches as described in Chapter 2A. The approach proposed and demonstrated in this concluding Chapter is expected to mitigate some of the major issues of Li-S chemistry. The proposed Li2S8 confined gel electrolyte exhibits moderately high values of ionic conductivity, 2 × 10-3 Ω-1cm-1 and shows a stable capacity of 350 mAhg-1 over 30 days in a separator free Li-S battery.

In this thesis the potential benefits of combining a photovoltaic (PV) system with a battery storage are investigated. The thesis is conducted at the company WSP in Uppsala and the aim is to design a PV system for the new city bus depot that is planned to be built in Uppsala, estimate the PV system capacity and investigate whether a battery storage can increase the self-consumption of the system. The results of this study are that the most appropriate installation of the PV modules is to place them horizontally on the roof and by that one can achieve an installed power of 715 kWp and a total annual electricity production of 871 MWh. This corresponds to a self-sufficiency of 29 % and a self-consumption of 92 %, which indicate that overproduction of electricity sometimes occurs. How different battery storages, based on both lead-acid and lithium-ion batteries, affect the system is evaluated by developing a battery model in MATLAB. From the results of the battery model it is concluded that battery storages with a capacity of 0.3–0.8 kWh/kWp are most suitable to combine with the PV system and this applies to both lead-acid and lithium-ion batteries. The interval 0.3–0.8 kWh/kWp corresponds to battery capacities of 200–600 kWh and the self-consumption increases to 93–94 % for the lead-acid battery storages and to 93–95 % for the lithium-ion battery storages. The economic analysis show that it is generally more profitable to increase self-consumption of self-produced PV power than to sell it to the grid. However, the high costs that are associated with the battery storages eliminates the economic benefits of the increased self-consumption of PV power. Therefore, it is not considered possible to justify the installation of a battery storage at the bus depot.

Transition metals (TMs) are ‘elements whose atoms have partially filled d-shell, or which can give rise to cations with an incomplete d-shell’. In TMs, the d-shell overlaps with next higher s-shell. Most of the TMs exhibit more than one (multiple) oxidation states. Some TMs, such as silver and gold, occur naturally in their metallic state but, most of the TM minerals are generally oxides. Most of the minerals on the planet earth are metal oxides, because of large free energies of formation for the oxides. The thermodynamic stability of the oxides is determined from the Ellingham diagram. Ellingham diagram shows the temperature dependence of the stability (free energy) for binaries such as metal oxides. Ellingham diagram also shows the ease of reducibility of metal oxides. TM oxides of general formulas MO, M2O3, MO2, M2O5, MO3 are known to exist, many of them being the ultimate products of oxidation in air in their highest oxidation states. In addition, TM oxides also exist in lower oxidation states which are prepared under controlled conditions. The nature of bonding in these oxides varies from mainly ionic (e.g. NiO, CoO) to mainly covalent (e.g. OsO4). Simple binary oxides of the compositions, MO, generally possess the rock salt structure (e.g. NiO), while the dioxides, MO2, possess the rutile structure (e.g. TiO2); many sesquioxides, M2O3, possess the corundum structure (e.g. Cr2O3). TMs form important ternary oxides like perovskites (e.g. CaTiO3), spinels (e.g. MgFe2O4) and so on. In TM oxides, the valence (outer) d-shell could be empty, d0 (e. g. TiO2), partially filled, dn (1≤ n≤ 9) (e.g. TiO, VO, NiO etc.) or completely filled, d10 (e.g. ZnO, CdO, Cu2O etc.). The outer d electrons in TM oxides could be localized or delocalized. Localized outer d electrons give insulators/semiconductors, while delocalized/itinerant d electrons make the TM oxide ‘metallic’ (e.g. ReO3, RuO2). Partially filled dn states are normally expected to give rise to itinerant (metallic) electron behaviour. But most of TM oxides with partially filled d shell are insulators because of special electronic energy (correlation energy) involved in d electron transfer to adjacent sites. Such insulating TM oxides are known as Mott insulators (e. g. NiO, CoO etc.). Certain TM oxides are known to exhibit both localized (insulating) and itinerant (metallic) behaviour as a function of temperature or pressure. For example, VO2 shows a insulator–metal transition at ~340K. Similar transitions are also known for V2O3, metal-rich EuO and so on. The chemical composition and bonding of TM oxides, which determine the crystal and electronic structures, give rise to functional properties. Table 1 gives representative examples. Properties like ionic conductivity and diffusion are governed by both the crystal structure and the defect structure (point defects), whereas properties such as magnetism and electron transport mainly arise from the electronic structures of the materials. Accordingly, TM oxides provide a platform for exploring functional materials properties. Among the various functional materials properties exhibited by transition metal oxides, the present thesis is devoted to investigations of lithium ion battery cathodes, inorganic pigments and magnetic perovskites. Over the years, most of the lithium containing first row transition metal oxides of rock salt derived structure have been investigated for possible application as cathode materials in lithium ion batteries (LIBs). First major breakthrough in LIBs research was achieved by electrochemically deinserting and inserting lithium in LiCoO2. A new series of cathode materials for LIBs were prepared by incorporating excess lithium into the transition metal containing layered lithium oxides through solid solution formation between Li2MnO3–LiMO2 (M = Cr, Mn, Fe, Co, Ni), known as lithium-rich layered oxides (LLOs). LLOs exhibit improved electrochemical performance as compared to the corresponding end members and hence received significant attention as a potential next generation cathode materials for LIBs in recent times. LiCoO2 (R-3m) crystallizes in the layered α-NaFeO2 structure with the oxygens in a ccp arrangement. Li+ and Co3+ ions almost perfectly order in the octahedral sites (3a and 3b) to give alternating (111) planes of LiO6 and CoO6 octahedra. Table 1. Materials properties exhibited by representative TM oxides. Property Example(s) Ferroelectricity BaTiO3, PbTiO3, Bi4Ti3O12 Nonlinear Optical Response LiNbO3 Multiferroic response BiFeO3, TbMnO3 Microwave dielectric properties Ba3ZnTa2O9 Relaxor Dielectric Properties Pb3MgNb2O9, Colossal Magnetoresistance Tl2Mn2O7 Metallic ‘Ferroelectricity’ Cd2Re2O7 Superconductivity AOs2O6(A = K, Rb, Cs) Redox deinsertion/insertion of LiCoO2 lithium Photocatalysis/water splitting TiO2 Pigment Ca(1-x)LaxTaO(2-x)N1+x (yellow-red), YIn1-xMnxO3 (blue) Metallic Ferromagnetism CrO2 Antiferromagnetism NiO, LaFeO3 Zero thermal expansion ZrW2O8 The reversible capacity of LiCoO2 in common LIBs is relatively low at around 140 mA h g-1 (half of theoretical capacity), corresponding to: LiCo3+O2 → Li0.5Co3+0.5Co4+0.5O2 + 0.5Li+ + 0.5e– . Substitution of one or more transition metal ions in LiCOO2 has been explored to improve the electrochemical performance. The structure of LLOs is described as a solid solution or nano composite of Li2MnO3 (C2/m) and LiMO2 (R-3m). The electrochemical deinsertion/insertion behaviour of LLOs is complex and also not yet understood completely. The present thesis consists of four parts. After a brief introduction (Part 1), Part 2 is devoted to materials for Li-ion battery cathode, consisting of three Chapters 2.1, 2.2 and 2.3. In Chapter 2.1, we describe the synthesis, crystal structure, magnetic and electrochemical characterization of new LiCoO2 type rock salt oxides of formula, Li3M2RuO6 (M = Co, Ni). The M =Co oxide adopts the LiCoO2 (R-3m) structure, whereas the M = Ni oxide also adopts a similar layered structure related to Li2TiO3. Magnetic susceptibility measurements reveal that in Li3Co2RuO6, the oxidation states of transition metal ions are Co3+, Co2+ and Ru4+, whereas in Li3Ni2RuO6, the oxidation states are Ni2+ and Ru5+. Li3Co2RuO6 orders antiferromagnetically at ~10K. On the other hand, Li3Ni2RuO6 presents a ferrimagnetic behaviour with a Curie temperature of ~100K. Electrochemical Li-deinsertion/insertion studies show that high first charge capacities (between ca.160 and 180 mA h g−1) corresponding to ca.2/3 of theoretical capacity are reached albeit, in both cases, capacity retention and cyclability are not satisfactory. Chapter 2.2 presents a study of new ruthenium containing LLOs, Li3MRuO5 (M = Co and Ni). Both the oxides crystallize in the layered LLO type LiCoO2 (α-NaFeO2) structure consisting of Li[Li0.2M0.4Ru0.4]O2 layers. Magnetic susceptibility data suggest that the oxidation states of transition metals are Li3Co3+Ru4+O5 for the M = Co compound and Li3Ni2+Ru5+O5 for the M = Ni compound. Electrochemical investigations of lithium deintercalation–intercalation behaviour reveal that both Co and Ni phases exhibit attractive specific capacities of ca. 200 mA h g-1 at an average voltage of 4 V, that has been interpreted as due to the oxidation of Co3+ and Ru4+ in Li3CoRuO5 and Ni2+ to Ni4+ in the case of Li3NiRuO5. Thus, we find that ruthenium plays a favourable role in LLOs than in non-LLOs in stabilizing higher reversible electrochemical capacities. In Chapter 2.3, we describe the synthesis, crystal structure and lithium deinsertion–insertion electrochemistry of two new LLOs, Li3MRuO5 (M=Mn, Fe) which are analogs of the oxides described in Chapter 2.2. The Li3MnRuO5 oxide adopts a structure related to Li2MnO3 (C2/m), while the Li3FeRuO5 oxide adopts a near-perfect LiCoO2 (R-3m) structure. Lithium electrochemistry shows typical behaviour of LLOs for both oxides, where participation of oxide ions in the electrochemical processes is observed. A long first charge process with capacities of 240 mA h g-1 (2.3 Li per f.u.) and 144 mA h g-1 (1.38 Li per f.u.) is observed for Li3MnRuO5 and Li3FeRuO5, respectively. Further discharge–charge cycling points to partial reversibility. X-ray photoelectron spectroscopy (XPS) characterisation of both pristine and electrochemically oxidized Li3MRuO5 reveals that in the Li3MnRuO5 oxide, Mn3+ and Ru4+ are partially oxidized to Mn4+ and Ru5+ in the sloping region at low voltage, while in the long plateau, O2- is also oxidized. In the Li3FeRuO5 oxide, the oxidation process appears to affect only Ru (4+ to 5+ in the sloping region) and O2- (plateau), while Fe seems to retain its 3+ state. Another characteristic feature of TMs is formation of several coloured solid materials where d–d transitions, band gap transitions and charge transfer transitions are involved in the colouration mechanism. Coloured TM oxides absorbing visible light find important applications as visible light photocatalyst (for example, yellow BiVO4 for solar water splitting and red Sr1-xNbO3 for oxidation of methylene blue) and inorganic pigments [for example, Egyptian blue (CaCuSi4O10), Malachite green (Cu2CO3(OH)2), Ochre red (Fe2O3)]. Pigments are applied as colouring materials in inks, dyes, paints, plastics, ceramic glazers, enamels and textiles. In this thesis, we have focused on the coloured TM oxides for possible application as inorganic pigments. Generally, colours arise from electronic transitions that absorb visible light. Colours of the inorganic pigments arise mainly from electronic transitions involving TM ions in various ligand fields and charge transfer transitions governed by different selection rules. The ligand field d–d transitions are parity forbidden but are relaxed due to various reasons, such as distortion (absence of center of inversion) and vibronic coupling. The d-electrons can be excited by light absorption in the visible region of the spectrum imparting colour to the material. Charge transfer transitions in the visible region are not restricted by the parity selection rules and therefore give intense colours. Here we have investigated the colours of manganese in unusual oxidation state (Mn5+) as well as the colours of different 3d-TM ions in distorted octahedral and trigonal prismatic sites in appropriate colourless crystalline host oxides. These results are discussed in Part 3 of the thesis. In Chapter 3.1, we describe a blue/green inorganic material, Ba3(P1−xMnxO4)2 (I) based on tetrahedral Mn5+O4 :3d2 chromophore. The solid solutions (I) which are sky-blue and turquoise-blue for x ≤ 0•25 and dark green for x ≥ 0•50, are readily synthesized in air from commonly available starting materials, stabilizing the Mn5+O4 chromophore in an isostructural phosphate host. We suggest that the covalency/ionicity of P–O/Mn–O bonds in the solid solutions tunes the crystal field strength around Mn(V) such that a blue colour results for materials with small values of x. The material could serve as a nontoxic blue/green inorganic pigment. In Chapter 3.2, an experimental investigation of the stabilization of the turquoise-coloured Mn5+O4 chromophore in various oxide hosts, viz., A3(VO4)2 (A = Ba, Sr, Ca), YVO4, and Ba2MO4 (M = Ti, Si), has been carried out. The results reveal that substitution of Mn5+O4 occurs in Ba3(VO4)2 forming the entire solid solution series Ba3(V1−xMnxO4)2 (0 < x ≤ 1.0), while, with the corresponding strontium derivative, only up to about 10% of Mn5+O4 substitution is possible. Ca3(VO4)2 and YVO4 do not stabilize Mn5+O4 at all. With Ba2MO4 (M = Ti, Si), we could prepare only partially substituted materials, Ba2M1−xMn5+xO4+x/2 for x up to 0.15, that are turquoise-coloured. We rationalize the results that a large stabilization of the O 2p-valence band states occurs in the presence of the electropositive barium that renders the Mn5+ oxidation state accessible in oxoanion compounds containing PO43−, VO43−, etc. By way of proof-of-concept, we synthesized new turquoise-coloured Mn5+O4 materials, Ba5(BO3)(MnO4)2Cl and Ba5(BO3)(PO4)(MnO4)Cl, based on the apatite – Ba5(PO4)3Cl – structure. Chapter 3.3 discusses crystal structures, and optical absorption spectra/colours of 3d-transition metal substituted lyonsite type oxides, Li3Al1-xMIIIx(MoO4)3 (0< x ≤1.0) (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (0< x ≤1.0) (MII = Co, Ni, Cu). Crystal structures determined from Rietveld refinement of PXRD data reveal that in the smaller trivalent metal substituted lyonsite oxides, MIII ions occupy the octahedral (8d, 4c) sites and the lithium ions exclusively occur at the trigonal prismatic (4c) site in the orthorhombic (Pnma) structure; on the other hand, larger divalent cations (CoII/CuII) substituted derivatives show occupancy of CoII/CuII ions at both the octahedral and trigonal prismatic sites. We have investigated the colours and optical absorption spectra of Li3Al1-xMIIIx(MoO4)3 (MIII = Cr, Fe) and Li3-xAl1-xMII2x(MoO4)3 (MII = Co, Ni, Cu) and interpreted the results in terms of average crystal field strengths experienced by MIII/MII ions at multiple coordination geometries. We have also identified the role of metal-to-metal charge transfer (MMCT) from the partially filled transition metal 3d orbitals to the empty Mo – 4d orbitals in the resulting colours of these oxides. B The ABO3 perovskite structure consists of a three dimensional framework of corner shared BO6 octahedra in which large A cation occupies dodecahedral site, surrounded by twelve oxide ions. The ideal cubic structure occurs when the Goldschmidt’s tolerance factor, t = (rA + rO)/{√2(rB + rO)}, adopts a value of unity and the A–O and B–O bond distances are perfectly matched. The BO6 octahedra tilt and bend the B – O – B bridges co-operatively to adjust for the non-ideal size of A cations, resulting deviation from ideal cubic structure to lower symmetries. Ordering of cations at the A and B sites of perovskite structure is an important phenomenon. Ordering of site cations in double (A2BB'O6) and multiple (A3BB'2O9) perovskites give rise to newer and interesting materials properties. Depending upon the constituent transition metals and ordering, double perovskite oxides exhibit a variety of magnetic behaviour such as ferromagnetism, ferrimagnetism, antiferromagnetism, spin-glass magnetism and so on. We also have coupled magnetic properties such as magnetoresistance (Sr2FeMoO6), magnetodielectric (La2NiMnO6) and magnetooptic (Sr2CrWO6) behaviour. Here we have investigated new magnetically frustrated double perovskite oxides of the formula Ln3B2RuO9(B = Co, Ni and Ln = La, Nd). The Chapter 4.1 describes Ln3B2RuO9 (B = Co, Ni and Ln = La, Nd) oxides (prepared by a solid state metathesis route) which adopt a monoclinic (P21/n) A2BB'O6 double perovskite structure, wherein the two independent octahedral 2c and 2d sites are occupied by B2+ and (B2+1/3Ru5+2/3) atoms, respectively. Temperature dependence of the molar magnetic susceptibility plots obtained under zero field cooled (ZFC) condition exhibit maxima in the temperature range 25–35K, suggesting an antiferromagnetic interaction in all these oxides. Ln3B2RuO9 oxides show spin-glass behavior and no long-range magnetic order is found down to 2 K. The results reveal the importance of competing nearest neighbour (NN), next nearest neighbor (NNN) and third nearest neighbour (third NN) interactions between the magnetic Ni2+/Co2+ and Ru5+ atoms in the partially ordered double perovskite structure that conspire to thwart the expected ferromagnetic order in these materials.

L'utilisation de systèmes de stockage de l'énergie électrique tels que les batteries nécessite l'assemblage de plusieurs cellules. Comme chacune de ces dernières peut avoir des caractéristiques légèrement différentes ainsi que des conditions d'environnement thermique ou de vieillissement distinctes, l'utilisation d'un système d'équilibrage permettant une bonne gestion de la répartition de l'énergie au sein des éléments qui composent le pack est nécessaire. Les travaux de recherche présentés se rapportent à l'étude et à la conception d'un tel circuit d'équilibrage à base de convertisseurs d'énergie intégrables ainsi qu'aux sollicitations électriques engendrées dans les cellules lors de son utilisation. / To store electrical energy in batteries, the use of multiple cells is needed. Since each of these cells can have slightly different characteristics and also different thermal or aging environmental conditions, a balancing system is required to manage the energy inside the battery pack. The researches described in this document show the study and the design of such a balancing system based on power electronics converters and also the impact of these systems on the electrochemical cells.