In this paper, we report that various kinds of active sites on graphite surface including active hydrophilic sites markedly affect the electrochemical performance of graphite anodes for lithium ion batteries under different humidity conditions. After depositing metals such as Ag and Cu by immersing and heat-treating, these active sites on the graphite surface were removed or covered and its electrochemical performance under the high humidity conditions was markedly improved. This suggests that lithium ion batteries can be assembled under less strict conditions and that it provides a valuable direction to lower the manufacturing cost for lithium ion batteries.

Magnetic properties of powders, thin films and single crystals have been investigated using magnetometry methods. This thesis provides analysis and conclusions that are supported by the results obtained from spectroscopic and diffraction measurements as well as from theoretical calculations. First, the magnetic behavior of transition metal (TM) doped ZnO with respect to doping, growth conditions and post annealing has been studied. Our findings indicate that the magnetic behavior stems from small clusters or precipitates of the dopant, with ferromagnetic or antiferromagnetic interactions. At the lowest dopant concentrations, the estimated cluster sizes are too small for high resolution imaging. Still, the clusters may be sufficiently large to generate a finite spontaneous magnetization even at room temperature and could easily be misinterpreted as an intrinsic ferromagnetic state of the TM:ZnO compound. Second, influence of lattice strain on both magnetic moment and anisotropy has been investigated for epitaxial MnAs thin films grown on GaAs substrates. The obtained magnetic moments and anisotropy values are higher than for bulk MnAs. The enhanced values are caused by highly strained local areas that have a stronger dependence on the in-plane axis strain than out-of plane axis strain. Finally, spin glass behavior in Li-layered oxides, used for battery applications, and a double perovskite material has been investigated. For both Li(NiCoMn)O2 and (Sr,La)MnWO6, a mixed-valence of one of the transition metal ions creates competing ferromagnetic and antiferromagnetic interactions resulting in a low temperature three-dimensional (3D) spin glass state. Additionally, Li(NiCoMn)O2 with large cationic mixing exhibits a percolating ferrimagnetic spin order in the high temperature region and coexists with a two-dimensional (2D) frustrated spin state in the mid temperature region. This is one of the rare observations where a dimensional crossover from 2D to 3D spin frustration appears in a reentrant material. / Felaktigt tryckt som Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology 720

Battery Management System (BMS) is an essential part in battery powered applications where large battery packs are in use. BMS ensures protection, controlling, supervision and accurate state estimation of battery pack to provide efficient energy management. However the particular application determines the accuracy and requirements of BMS where it has to implement; in electric vehicles (EVs) accuracy cannot be compromised. The software part of BMS estimates the states of the battery pack and takes the best possible decision. In EVs one of the key tasks of BMS’s software part is to provide the actual state of charge (SOC), which represents a crucial parameter to be determined, especially in lithium iron phosphate (LiFePO4) batteries, due to the presence of the high hysteresis behavior in the open circuit voltage than other kind of lithium batteries. This hysteresis phenomena appears with two different voltage curves during the charging and discharging process. The value of the voltage that the battery is going to assume during the off-loading operation depends on several factors, such as temperature, loop direction and ageing. In this research work, hybrid method is implemented in which advantages of several methods are achieved by implementing one technique combined with another. In this work SOC is calculated from coulomb counting method and in order to correct the error of SOC, an hysteresis model is developed and used due to presence of hysteresis effect in LiFePO4 batteries. An hysteresis model of the open circuit voltage (OCV) for a LiFePO4 cell is developed and implemented in MATLAB/Simulink© in order to reproduce the voltage response of the battery when no current from the cell is required (no load condition). Then the difference of estimated voltage and measured voltage is taken in order to correct the error of SOC calculated from coulomb counting or current integration method. To develop the hysteresis model which can reproduce the same voltage behavior, lot of experiments have been carried out practically in order to see the hysteresis voltage response and to see that how voltage curve change with the variation of temperature, ageing and loop direction. At the end model is validated with different driving profiles at different ambient temperatures.

The purpose of study is to research the development of electric vehicle technology in the United States. This study describes the United States public policies towards electric vehicle technology and system of innovation approaches. The government roles with the help of national system of innovation have been also covered in this study. The point of departure was the study of available literature and U.S energy policy acts which illustrates that the break-through in electric vehicles still not only depended on better battery technology and infrastructure for charging stations but also on social, economic and political factors. The important actors involved in the process are both at local and international level are private firms, governmental departments, research and development (R&D) institutes, nongovernment organizations (NGO’s) and environmental organizations etc. The arguments which are put forward in the background of development of such technologies are to reduce dependence on foreign oil and to reduce emissions of harmful gasses.

This bachelor thesis investigates what kind of battery system that is suitable for an electric driveline equipped with a mechanical fly wheel, focusing on a battery with high specific energy capacity. Basic battery theory such as the principle of an electrochemical cell, limitations and C-rate is explained as well as the different major battery systems that are available. Primary and secondary cells are discussed, including the major secondary chemistries such as lead acid, nickel cadmium (NiCd), nickel metal hydride (NiMH) and lithium ion (Li-ion). The different types of Li-ion chemistries are investigated, explained and compared against each other as well as other battery technologies. The need for more complex protection circuitry for Li-ion batteries is included in the comparison. Request for quotations are made to battery system manufacturers and evaluated. The result of the research is that the Li-ion NMC energy cell is the best alternative, even if the cost per cell is the most expensive compared to other major technologies. Due to the budget, the LiFeMnPO4 chemistry is used in the realisation of the final system, which is scaled down with consideration to the power requirement.

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.

Dans ce travail de thèse, nous avons exploré l'utilisation des nanomatériaux à base de carbone comme anode pour les batteries lithium-ion. Par rapport aux matériaux d'anode classiques qui sont de type carbone graphitique a des tailles de grains de l'ordre du micromètre, les matériaux de carbone de taille nanométrique présentent un grand potentiel non seulement pour l'application pratique en tant que matériau d'anode, mais aussi du point de vue de la science fondamentale car permettent l'exploration fine des phénomènes de diffusion des ions lithium. Dans le cadre de l'application pratique, nous avons exploré les nanofibres unidimensionnelles de carbone (CNF) en tant que matériau d'anode. Cette structure d'anode comporte un substrat métallique comme collecteur de courant mais n'avons pas utilisé des liants ce qui bénéficie a la stabilité à long terme. Pourtant, la densité d'énergie que nous avons obtenu était encore limitée à 370 mAh /g similaire à celle du carbone conventionnel. Afin d'améliorer la capacité des nanofibres de carbone bruts, nous les avons recouverts de silicium (par dépôt électrochimique), un matériau d'insertion de lithium avec une bien plus importante capacité de stockage. Le tapis hybrides Si / CNF ont permis d'améliorer nettement la capacité des matériaux de carbone jusqu'à deux fois de plus pour la plupart des cas. Du point de vue des études fondamentales, le graphène matériau bidimensionnel, a été synthétisé par dépôt chimique en phase vapeur (CVD) et utilisé comme un support pour mettre en évidence les chemins de diffusion des ions lithium. Par rapport à du graphite classique qui contient à la fois les deux plans de type basal et prismatique, seulement un plan basal bien défini et d'une grande surface spécifique peut être réalisé dans le cas du graphène. Nous avons découvert que la réaction électrochimique a l'électrode (substrat / graphène) est non seulement liée au nombre de couches de graphène mais s'appuie également sur la présence de défauts dans le plan de graphène. Combinant les résultats expérimentaux et les calculs de théoriques, nous avons pu prouver que le plan basal empêche la diffusion des ions de lithium avec une hauteur de barrière de diffusion élevé, alors que les divacancies et les défauts d'ordre supérieur peuvent constituer des raccourcis pour la diffusion des ions de lithium.

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.

The University of Waterloo Alternative Fuels Team’s participation in EcoCAR: The Next Challenge provided an unparalleled opportunity to execute advanced vehicle technology research with hands on learning and industry leading mentoring from practicing engineers in the automotive industry. This thesis investigates the optimization of the hybrid operating strategy on board the EcoCAR development vehicle. This investigation provides the framework to investigate the pros and cons of different hybrid control strategies, develop the model based design process for controls development in a student team environment and take the learning of this research and apply them to a mule development vehicle. A primary controls development model was created to simulate software controls before releasing to the vehicle level and served as a tool to evaluate and compare control strategies. The optimization routine was not directly compatible with this model and so a compromise was made to develop a simplified vehicle model in the MATLAB environment that would be useful for observing trends but realizing that the accuracy of the results may not be totally consistent with the real world vehicle. These optimization results were then used to create a new control strategy that was simulated in the original vehicle development model. This new control strategy exhibited a 15% gain in fuel economy over the best case from the literature during an Urban Dynamometer Driving Schedule (UDDS) drive cycle. Recommendations for future work include adding charge depletion operation to the simulation test cases and improving the accuracy of the optimization model by removing the simplifications that contributed to faster simulation time. This research has also illustrated the wide variability of drive cycles from the mildly aggressive UDDS cycle having 5 kilowatts average propulsion power to the very aggressive US06 cycle having 19 kilowatts average propulsion power and their impact on the efficiency of a particular control strategy. Understanding how to adapt or tune software for particular drive cycle or driver behaviour may lead to an interesting area of research.

Recent carbon allotropes such as carbon nanotubes (CNTs), fullerenes (C60s) and graphene have attracted great interests in both science and engineering due to their unique properties such as excellent electrical and mechanical properties as well as its vast surface area, and have led to many commercial applications. Especially, CNTs have been considered to be one of the promising candidates in the Li ion battery system because of its outstanding properties. However, the experimental results in the pristine CNT system have shown just slight improvement than original graphitic carbon material, which has been attributed to the weak adsorption of Li on CNTs. In this study, we investigated two types of CNT-C60 hybrid system consisting of CNTs and C60s to improve Li adsorption capabilities and predict its performance through quantum mechanical (QM) computations. First, we investigated adsorption energy of lithium (Li) on dilute CNT-C60 hybrid and CNT-C60 nanobud system as well as various electronic properties such as band structure, density of states (DOS), molecular orbital and charge distribution. Then, we expanded our interest to the more realistic condensed structure of CNT-C60 hybrid and nanobud system to examine actual electrochemical characteristics. The study of the condensed structure has been expanded to the very unique CNT-C60 nano-network system and examined mechanical strength as well as electronic properties. Finally, Li adsorption on other carbon allotropes system such as graphene-C60 hybrid and graphene-C60 bud system was investigated in order to provide fundamental understanding of electronic interaction between carbon allotrope and effect of Li adsorption.