An investigation of electrochemical storage device materials has been undertaken in four parts. The bulk and interfacial resistance of Na+ beta-alumina tubes were separated using a galvanostatic charge-discharge method. Sodium silicide was characterized to better understand its synthesis. BiMn2O5 was produced using a sol-gel method and tested for pseudocapacity. Different lithium ion anode and cathode materials were deposited using a new electrophoretic deposition method. A novel galvanostatic charge-discharge method was developed for the determination of bulk and interface resistance in Na+ beta-alumina solid electrolytes [BASE]. Dense and duplex BASE tubes were tested by varying the exposed surface area. The results of dense BASE tube pairs were used to determine the bulk and interfacial resistance components, while duplex BASE tubes were tested to determine the reduction in interfacial resistance. It was found that duplex tubes had reduced the interfacial resistance by 75%, when compared to a uniformly dense electrolyte. Sodium silicide was characterized using various methods to better understand the phase and the Na-Si phase diagram. EMF experiments using Na+ BASE tubes was used to determine the activity in the silicon rich region of the phase diagram, which showed a sodium activity of 0.5 at 550°C. TGA/DSC was used to determine phase transformation temperatures, as well as the heat of formation for NaSi, which was recorded to be below 1 kJ mol-1. A sol-gel precipitation method was used to produce fine BiMn2O5 powders used for supercapacitors. The powders resulting from a consistent method were tested for pseudocapacitance using bulk and thin film electrodes. Bulk electrodes had a gravimetric capacitance of 10 F g-1, while thin film electrodes only reached 2.6 F g-1. Lithium ion battery anode (Li4Ti5O12) and cathode (LiFePO4, LiMn2O4, LiMn1.5Ni0.5O4) materials were electrophoretically deposited with the assistance of PAZO-Na and CMC-Na. Cathodes were successfully deposited on aluminium substrates, and were tested in the potential window 2 – 4.3 V. The LiFePO4 cathodes showed capacity of 146.7 mAh g-1 at C/10, while showing capacity retention of 103% after 50 cycles. / Thesis / Doctor of Philosophy (PhD) / The goal of this work is to examine materials used in different types of electrochemical storage devices. The modification of resistive properties of β-alumina electrolytes are examined for use in high temperature sodium batteries. Electrophoretic deposition methods are used to rapidly make thin electrodes for lithium ion batteries and supercapacitors. The stoichiometric compound NaSi, a potentially safer and greener method of producing hydrogen gas, is characterized for a better understanding of its properties, and therefore production.

Lithium-ion based battery energy storage system has become one of the most popular forms of energy storage system for its high charge and discharge efficiency and high energy density. This dissertation proposes a high-efficiency grid-tie lithium-ion battery based energy storage system, which consists of a LiFePO4 battery based energy storage and associated battery management system (BMS), a high-efficiency bidirectional ac-dc converter and the central control unit which controls the operation mode and grid interface of the energy storage system. The BMS estimates the state of charge (SOC) and state of health (SOH) of each battery cell in the pack and applies active charge equalization to balance the charge of all the cells in the pack. The bidirectional ac-dc converter works as the interface between the battery pack and the ac grid, which needs to meet the requirements of bidirectional power flow capability and to ensure high power factor and low THD as well as to regulate the dc side power regulation. A highly efficient dual-buck converter based bidirectional ac-dc converter is proposed. The implemented converter efficiency peaks at 97.8% at 50-kHz switching frequency for both rectifier and inverter modes. To better utilize the dc bus voltage and eliminate the two dc bus bulk capacitors in the conventional dual-buck converter, a novel bidirectional ac-dc converter is proposed by replacing the capacitor leg of the dual-buck converter based single-phase bidirectional ac-dc converter with a half-bridge switch leg. Based on the single-phase bidirectional ac-dc converter topology, three novel three-phase bidirectional ac-dc converter topologies are proposed. In order to control the bidirectional power flow and at the same time stabilize the system in mode transition, an admittance compensator along with a quasi-proportional-resonant (QPR) controller is adopted to allow smooth startup and elimination of the steady-state error over the entire load range. The proposed QPR controller is designed and implemented with a digital controller. The entire system has been simulated in both PSIM and Simulink and verified with hardware experiments. Small transient currents are observed with the power transferred from rectifier mode to inverter mode at peak current point and also from inverter mode to rectifier mode at peak current point. The designed BMS monitors and reports all battery cells parameters in the pack and estimates the SOC of each battery cell by using the Coulomb counting plus an accurate open-circuit voltage model. The SOC information is then used to control the isolated bidirectional dc-dc converter based active cell balancing circuits to mitigate the mismatch among the series connected cells. Using the proposed SOC balancing technique, the entire battery storage system has demonstrated more capacity than the system without SOC balancing. / Ph. D.

Lithium-ion batteries are complex systems and making a simulation model of them is always challenging. A method for producing an accurate model with high capabilities for predicting the behavior of the battery in a time and cost efficient way is desired in this field of work. The aim of this thesis has been to develop a method to be close to the desired method as much as possible, especially in two important aspects, time and cost. The method which is the goal of this thesis should fulfill the below five requirements: 1. Able to produce a generic battery model for different types of lithium-ion batteries 2. No or low cost for the development of the model 3. A time span around one week for obtaining the model 4. Able to predict the most aspects of the battery’s behavior like the voltage, SOC, temperature and, preferably, simulate the degradation effects, safety and thermal aspects 5. Accuracy with less than 15% error The start point of this thesis was the study of current methods for cell modeling. Based on their approach, they are divided into three categories, abstract, black box and white box methods. Each of these methods has its own advantages and disadvantages, but none of them are able to fulfill the above requirements. This thesis presents a method, called “gray box”, which is, partially, a mix of the black and white boxes’ concepts. The gray box method uses values for model’s parameters from different sources. Firstly, some chemical/physical measurements like in the case of the white box method, secondly, some of the physical tests/experiments used in the case of the black box method and thirdly, information provided by cell datasheets, books, papers, journals and scientific databases. As practical part of this thesis, a prismatic cell, EIG C20 with 20Ah capacity was selected as the sample cell and its electrochemical model was produced with the proposed method. Some of the model’s parameters are measured and some others are estimated. Also, the abilities of AutoLion, a specialized software for lithium-ion battery modeling were used to accelerate the modeling process. Finally, the physical tests were used as part of the references for calculating the accuracy of the produced model. The results show that the gray box method can produce a model with nearly no cost, in less than one week and with error around 30% for the HPPC tests and, less than this, for the OCV and voltage tests. The proposed method could, largely, fulfill the five mentioned requirements. These results were achieved even without using any physical tests/experimental data for tuning the parameters, which is expected to reduce the error considerably. These are promising results for the idea of the gray box which is in its nascent stages and needs time to develop and be useful for commercial purposes.

This dissertation addresses the synthesis mechanism of mesoporous titania thin films with 2D Hexagonal Close Packed (HCP) cylindrical nanopores by an evaporation-induced self-assembly (EISA) method with Pluronic surfactants P123 and F127 as structure directing agents, and their applications in photovoltaics and lithium ion batteries. To provide orthogonal alignment of the pores, surface modification of substrates with crosslinked surfactant has been used to provide a chemically neutral surface. GISAXS studies show not only that aging at 4°C facilitates ordered mesostructure development, but also that aging at this temperature helps to provide orthogonal orientation of the cylindrical micelles which assemble into an ordered mesophase directly by a disorder-order transition. These films provide pores with 8-9 nm diameter, which is precisely the structure expected to provide short carrier diffusion length and high hole conductivity required for efficient bulk heterojunction solar cells. In addition, anatase titania is a n-type semiconductor with a band gap of +3.2 eV. Therefore, titania readily absorbs UV light with a wavelength below 387 nm. Because of this, these titania films can be used as window layers with a p-type semiconductor incorporated into the pores and at the top surface of the device to synthesize a photovoltaic cell. The pores provide opportunities to increase the surface area for contact between the two semiconductors, to align a p-type semiconductor at the junction, and to induce quantum confinement effects. These titania films with hexagonal phase are infiltrated with a hole conducting polymer, poly(3-hexylthiophene) (P3HT), in order to create a p-n junctions for organic-inorganic hybrid solar cells, by spin coating followed by thermal annealing. This assembly is hypothesized to give better photovoltaic performance compared to disordered or bicontinuous cubic nanopore arrangements; confinement in cylindrical nanopores is expected to provide isolated, regioregular “wires” of conjugated polymers with tunable optoelectronic properties, such as improved hole conductivity over that in bicontinuous cubic structure. The kinetics of infiltration into the pores show that maximum infiltration occurs within less than one hour in these films, and give materials with improved photovoltaic performance relative to planar TiO2/P3HT assemblies. These oriented mesoporous titania films are also used to develop an inorganic solar cell by depositing CdTe at the top using the Close Spaced Sublimation (CSS) technique. A power conversion efficiency of 5.53% is measured for heterostructures built using mesoporous titania films, which is significantly enhanced relative to planar TiO2/CdTe devices and prior reports in the literature. These mesoporous titania films have a great potential in inorganic solar cell development and can potentially replace CdS window layers which are conventionally used in inorganic CdS-CdTe solar cells. The last part of the dissertation addresses layer-by-layer synthesis to increase the thickness of mesoporous titania films with vertically oriented 2D-HCP nanopores, and their use in lithium ion batteries as negative electrodes because of advantages such as good cycling stability, small volume expansion (~3%) during intercalation/extraction and high discharge voltage plateau. The high surface area and small wall thickness of these titania films provide excellent lithium ion insertion and reduced Li-ion diffusion length, resulting in stable capacities as high as 200-250 mAh/g over 200 cycles.

Solid state lithium ion electrolytes are important to the development of next generation safer and high power density lithium ion batteries. Perovskite-structured LLT is a promising solid electrolyte with high lithium ion conductivity. LLT also serves as a good model system to understand lithium ion diffusion behaviors in solids. In this thesis, molecular dynamics and related atomistic computer simulations were used to study the diffusion behavior and diffusion mechanism in bulk crystal and grain boundary in lithium lanthanum titanate (LLT) solid state electrolytes. The effects of defect concentration on the structure and lithium ion diffusion behaviors in LLT were systematically studied and the lithium ion self-diffusion and diffusion energy barrier were investigated by both dynamic simulations and static calculations using the nudged elastic band (NEB) method. The simulation results show that there exist an optimal vacancy concentration at around x=0.067 at which lithium ions have the highest diffusion coefficient and the lowest diffusion energy barrier. The lowest energy barrier from dynamics simulations was found to be around 0.22 eV, which compared favorably with 0.19 eV from static NEB calculations. It was also found that lithium ions diffuse through bottleneck structures made of oxygen ions, which expand in dimension by 8-10% when lithium ions pass through. By designing perovskite structures with large bottleneck sizes can lead to materials with higher lithium ion conductivities. The structure and diffusion behavior of lithium silicate glasses and their interfaces, due to their importance as a grain boundary phase, with LLT crystals were also investigated by using molecular dynamics simulations. The short and medium range structures of the lithium silicate glasses were characterized and the ceramic/glass interface models were obtained using MD simulations. Lithium ion diffusion behaviors in the glass and across the glass/ceramic interfaces were investigated. It was found that there existed a minor segregation of lithium ions at the glass/crystal interface. Lithium ion diffusion energy barrier at the interface was found to be dominated by the glass phase.

Les nouvelles technologies sont de plus en plus demandeuses de sources de forte densité d’énergie respectueuses de l’environnement. Les accumulateurs lithium-ion semblent être la meilleure solution pour les applications mobiles et pour le domaine de l’automobile. Afin de répondre aux besoins en énergie de plus en plus importants, de nouveaux matériaux d’électrode négative sont nécessaires pour remplacer le carbone qui a désormais atteint son stade de maturité. En particulier, les composites silicium/carbone (Si/C) semblent être prometteurs pour augmenter la densité d’énergie des accumulateurs mais présentent de faibles rétentions de capacité au cours du cyclage. L’amélioration de la cyclabilité des composites Si/C fait l’objet de ce travail de thèse. La synthèse des composites par atomisation avec de l’alcool polyvinylique comme précurseur carboné suivie d’une pyrolyse est présentée. Les performances électrochimiques des matériaux résultants sont comparées à celles obtenues par d’autres composites, élaborés par lyophilisation et par broyage. Les propriétés intrinsèques des composites ont été modifiées par deux voies différentes afin d’améliorer leur cyclabilité. Dans un premiers temps, les effets de la réticulation de l’alcool polyvinylique ont été étudiés, puis ceux liés à l’ajout d’un catalyseur favorisant la graphitisation du carbone. La cyclabilité des composites Si/C peut également être améliorée en modifiant la nature du liant utilisé lors de la préparation des électrodes. L’intérêt bénéfique de l’emploi de l’acide polyacrylique en remplacement du fluorure de polyvinylidène couramment utilisé dans des électrodes à base de composites Si/C est démontré. / New technologies require more and more environment friendly sources of high energy density. Lithium-ion batteries seem to be the best solution for mobile and automotive applications. In order to meet the future energy requirements, new negative electrode materials are needed to replace carbon which has now reached a mature stage. Especially, silicon/carbon composites (Si/C) appear to be promising candidates to increase the energy density of batteries, but they still present poor capacity retention upon cycling. The improvement of Si/C composites cyclability is the subject of this thesis. The synthesis of Si/C composites by spray drying with polyvinyl alcohol as carbon precursor, followed by pyrolysis, is presented. The electrochemical performances are compared with those obtained for other composites, prepared by freeze drying and ball-milling. The intrinsic properties of the composites were modified in two different ways to improve their cyclability. First, we studied the effects of polyvinyl alcohol crosslinking, and then those related to the graphitization of carbon contained in these composites. The cyclability of Si/C composites can also be improved by changing the nature of the binder used during the electrodes preparation. The beneficial interest of using polyacrylic acid in replacement of polyvinylidene fluoride binder commonly used in Si/C based electrodes is shown.

Ce travail vise à modéliser le vieillissement des batteries lithium-ion soumises à des sollicitations de type véhicule (électrique ou hybride). Cette étude a notamment pour but d’optimiser le dimensionnement des packs batteries pour véhicule et les stratégies de gestion électrique. Une approche originale, de type fatigue mécanique, a été sélectionnée car potentiellement capable de modéliser des sollicitations complexes et variées. Cette approche a été développée pour une batterie lithium-ion spécifique graphite/NCA. Il apparaît qu’un simple cumul de dommage n’est pas entièrement pertinent et que deux contributions au vieillissement sont à l’œuvre : l’une en fonction de la charge échangée et l’autre en fonction du temps. De multiples essais de vieillissement ont été effectués et montrent l’influence très importante de la température, du courant et de l’état de charge sur chacune de ces contributions. Ces essais permettent de mettre en équation l’impact de chacun de ces paramètres sur la vitesse de dégradation. Il en découle un modèle informatique de prévision du vieillissement, capable de prendre en compte les périodes d’arrêt comme de roulage. Les résultats, sur des sollicitations peu à moyennement complexes, donnent une très faible erreur au niveau de la prévision. Des analyses post-mortem ont également été effectuées sur les batteries étudiées afin de comprendre les mécanismes en jeu. Plusieurs analyses (physico-chimiques et électrochimiques, par spectroscopie d’impédance) permettent de relier les principaux mécanismes de vieillissement à chacune des deux contributions : une altération de la structure cristalline du matériau actif d’électrode positive pour la contribution fatigue, la passivation du matériau actif d’électrode négative pour la contribution temporelle. Ces analyses apportent une vision plus complète du vieillissement et justifient les hypothèses effectuées lors de la mise en place du modèle. Elles permettent également d’envisager une généralisation du modèle à d’autres technologies de batteries lithium-ion. D’ailleurs, un essai de généralisation à une autre batterie commerciale a permis de vérifier la fiabilité et de détecter les limites de notre approche. / This scientific piece of work aims at modeling the aging of lithium-ion batteries, depending on the vehicle stress (electric or hybrid type). More specifically, this study intends to optimise the design of battery packs for vehicle and power management strategies. A original mechanical fatigue approach has been selected as potentially able to model complex and varied demands. This approach was developed for a specific graphite / NCA lithium-ion battery. It appears that a simple damage accumulation is not entirely relevant, and that two contributions to aging are ongoing: one based on charge throughput and the other based on time. Multiple aging tests were performed and have shown the important influence of temperature, current power and state of charge for each contribution. They led to the establishment of equations linking each of these parameters to battery degradation rate. Thanks to these equations, a computer model for aging prevision has been built, able to take into account both cycling and calendar ageing. The model gives, for slightly to moderately complex solicitations, a very small predicting error. Postmortem analyses were also performed on the batteries to understand the mechanisms involved. Several analytical techniques (physicochemical and electrochemical, impedance spectroscopy) make possible to connect the main mechanisms of ageing to the contributions: an alteration of the crystalline structure of the positive electrode active material for the fatigue contribution, passivation of the negative electrode active material for the time contribution. These analyses provide a more complete view of aging and justify the hypothesis made during the implementation of the model. These electrochemical results allow us to consider a generalisation to other lithium-ion battery technologies. Indeed, an attempt to generalise the model to another commercial battery has made possible to check the reliability and to detect limits of this approach.

Limiter le vieillissement des accumulateurs lithium-ion est un challenge pour optimiser leur utilisation notamment dans le domaine spatial. La qualité de la couche de passivation (SEI), formée à la surface de l’électrode négative de graphite lors des premiers cycles de vie de la batterie, est déterminante pour ses performances futures. Celle-ci est composée de polymères et de divers sels de lithium dont la dissolution, la précipitation et la migration affectent les performances. Cette étude vise à comprendre l’impact de ces composés sur la cyclabilité et de proposer des solutions à l’effet néfaste de ces sels sur le bon fonctionnement et le vieillissement de l’accumulateur Li-ion. La première partie de ce travail aborde l’impact de divers sels de lithium de la SEI (LiF, Li2CO3, LiOH, LiOCH3, LiOC2H5) sur le comportement en cyclage des accumulateurs. Par la suite, nous avons proposé des solutions pour améliorer le comportement qu’engendre la présence de ces sels sur les performances à travers deux approches. La première concerne l’utilisation de co-solvants complexants de la famille des glymes. La seconde approche consiste à modifier les propriétés interfaciales électrodes/électrolyte par l’ajout d’additifs tensioactifs à l’électrolyte. Les résultats montrent dans les deux cas des améliorations notables de la cyclabilité des dispositifs en demi-pile et en cellule complète. / Limiting the lithium-ion batteries ageing is a challenge to overcome in the field of spatial applications. The quality of the solid electrolyte interfaces (SEI), created at the electrode surface during the first cycles of the battery, is decisive for its future performances. The SEI is composed of polymers and several lithium salts which are able to dissolve, precipitate and migrate in the electrolyte and hence modify the battery performances. This study aims to understand the impact of the dissolution of these compounds on the cell cycling ability and to propose solutions to avoid the harmful effects of these salts on the battery ageing. The first part of this study is devoted to the study of the effect of dissolved SEI lithium salts (LiF, LiOH, Li2O, Li2CO3 , LiOCH3, LiOC2H5) on the cycling ability of half and full cells.In order to improve the battery performances in spite of the presence of these SEI salts in the electrolyte, two solutions have been examined. The first one is to add a co-solvent belonging to the glyme family which is able to form complexes with lithium ions and the second to use a surfactant additive which will modify the interfacial electrode/electrolyte properties. Results show that in both cases an improvement in half-cell or full-cell cycling ability was achieved.

No description available.

Für den Einsatz in Autobatterien gibt es besondere Anforderungen an den Elektrolyten im Bereich der Energie- und Leistungsdichten, um beispielsweise thermische Verluste gering zu halten. Hochleitfähige Elektrolyte mit Leitfähigkeiten im Millisiemensbereich sind hier ebenso notwendig wie auch sichere, d.h. möglichst nicht brennbare und einen niedrigen Dampfdruck besitzende Materialien. Um diese Vorgaben zu erreichen, ist es notwendig, einen polymeren Separator zu entwickeln, welcher auf brennbare organische Lösungsmittel verzichtet und damit eine drastische Steigerung der Sicherheit gewährleistet. Gleichzeitig müssen hierbei die Leistungsvorgaben bezüglich der Leitfähigkeit erfüllt werden. Zu diesem Zweck wurde ein Konzept basierend auf der Kombination von einer polymeren sauerstoffreichen Matrix und einer ionischen Flüssigkeit entwickelt und verifiziert. Dabei wurden folgende Erkenntnisse gewonnen: 1. Es wurden neuartige diacrylierte sauerstoffreiche Matrixkomponenten mit vielen Carbonylfunktionen, für eine gute Lithiumleitfähigkeit, synthetisiert. 2. Es wurden mehrere neue ionische Flüssigkeiten sowohl auf Imidazolbasis als auch auf Ammoniumbasis synthetisiert und charakterisiert. 3. Die Einflüsse der Kationenstruktur und der Einfluss der Gegenionen im Bezug auf Schmelzpunkte und Leitfähigkeiten wurden untersucht. 4. Aus den entwickelten Materialien wurden Blendsysteme hergestellt und mittels Impedanzspektrometrie untersucht: Leitfähigkeiten von 10-4S/cm bei Raumtemperatur sind realisierbar. 5. Die Blendsysteme wurden auf ihre thermische Stabilität hin untersucht: Stabilitäten bis 250°C sind erreichbar. Dabei wird keine kristalline Struktur beobachtet. / Within the field of energy storage and charge transfer, the lithium polymer batteries are one of the leading technologies, due to their low manufacture cost and their possible variety of packaging shapes. Despite their good thermal stability and very good weight to energy ratio, lithium ion batteries use as a electrolyte system a mixture of ethylene carbonate and diethyl carbonate as solvent which have a high risk of deflagration when they come in contact with water. Thus the developement of new materials for lithium-ion-batteries are necessary. For the electrolyte there are special requirements in terms of energy- and power density e.g. in order to minimize thermal loss. High conductivity electrolytes with conductivities in the range of milisiemens are as essential as safe materials, like non flammable non-volatile materials. To fulfill these requirements it is important to develop a polymeric lithium ion conductor, which is free of flammable organic solvents in order to ensure safety. Simultaneously it is also ,mandatory to achieve high performances in terms of ion-conductivity. Therefore a concept based on a combination of an oxygen rich polymeric matrix and ionic liquids was developed and verified. Following results were achieved . 1. Synthesis of new diacryalted oxygen rich matrix components with many carbonylfunctions for a good lithium ion transport. 2. Synthesis and characterization of new ionic liquids based on imidazol or ammonium compounds. 3. Investigation of the influences of the cation structure and counter ions for melting points and ion conductivity. 4. Creation of Blendsystems with the developed materials 5. Thermal investigations of these solid-state-electrolytes with DSC and TGA measurements, resulting in thermal stabilities up to 250°C.No crystallization were observed. 6. investigation of these solid-state-electrolytes via AC-impedance spectrometry, resulting in conductivities of 10-4S/cm at room temperature.