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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.

Rechargeable lithium-ion batteries have both the power and energy capabilities to be utilized in hybrid electric vehicles and other power demanding applications. However, there are obstacles primarily related to reliability in safety and lifetime. Additionally, there is still room for improvement in the battery performance. In this work, physics-based mathematical models have been successfully set-up and numerically solved to investigate performance, safety, and aging in lithium-ion battery systems. This modeling approach enabled a detailed analysis of the electrochemical processes related to these issues. As the models included many parameters and spatial resolution of several variables with time or frequency, strategies for investigation needed to be developed for most of the work. The accuracy of the investigation was consolidated by the utilization of parameters characterized from experimental work. The performance expressed in terms of polarization was determined for a power-optimized battery cell undergoing various operating conditions. A methodology that separated and quantified the contribution of each process to the polarization was set up, allowing the study of the contributions as a snapshot in time and as an average over a cycle. Mass transport in electrolyte was shown to be a crucial feature to improve especially if the battery is expected to undergo high current-loads for long periods of time. Safety-concerns when a battery cell is short-circuited were investigated for three types of short-circuit scenarios. All scenarios raised the temperature to the point where exothermic side reactions were initiated. The similarities between the scenarios in temperature increase were a result of the limiting current being reached. The differences, however small, were related to the placement of the short-circuit. Especially when the current collectors were not directly connected by the short circuit, an increased electronic resistance was observed which lowered both the generated current and heat. The aging of a battery cell was investigated by model analysis of electrodes harvested from fresh and aged cells. A methodology was used where a frequency-dependent model was fitted to three-electrode impedance experiments by tuning parameters associated to electrode degradation. For cycled cells, electrolyte decomposition products inhibiting the mass transport in the electrolyte and particle cracking in the positive electrode increased the impedance. A similar model was also set up for investigation of the lithium intercalation processes in PAN-based carbon fibers, showing it to have both good mass transport and kinetic capabilities. / Laddningsbara litiumjonbatterier har både ur energi- och effektsynpunkt möjligheten att kunna användas i elhybridfordon och inom andra effektkrävande tillämpningsområden. Batteriets säkerhet och livslängd är dock inte helt tillförlitliga. Dessutom finns det fortfarande utrymme för förbättringar av litiumjonbatteriets prestanda. I det här arbetet har matematiska modeller baserade på fysikaliska egenskaper framgångsrikt ställts upp och lösts numeriskt för att studera prestandan, säkerheten samt åldrandet hos litiumjonbatterisystem. Denna typ av modellering gjorde det möjligt att detaljerat analysera hur de elektrokemiska processerna bidrar. Eftersom modellerna omfattade ett stort antal parametrar och har variabler som förändras i åtminstone en dimension med tid eller frekvens, krävdes det att tydliga strategier för arbetet ställdes upp. Modelleringsstudiens noggrannhet stärktes av att flertalet av de använda parametrarna hade bestämts experimentellt. Polarisationen som ett mått på prestanda bestämdes för ett effektoptimerat batteri under olika laster. En metodik som separerar och beräknar hur mycket varje process bidrar till polarisationen skapades och användes för att studera bidragen över tid eller över en hel lastcykel. Resultaten visade att masstransporten i elektrolyten påverkar till stor del och bör förbättras om batteriet förväntas belastas med hög ström under lång tid. Säkerheten i samband med kortslutning av en battericell undersöktes för tre olika fall av kortslutningar. Alla fall uppvisade en temperaturökning som skulle kunna bidra till att exoterma reaktioner startas och termisk rusning uppstår. Temperaturökningen var liknande i samtliga kortslutningsfall och berodde på att gränsströmmen nåddes inom cellen. Skillnaderna mellan kortslutningsfallen var inte så betydande men kunde härledas till kortslutningens placering. Framförallt fallet då strömtilledarna inte kontakterades av kortslutningen observerades en ökad elektronisk resistans som sänkte både strömmen och värmeproduktionen. Åldringen i en battericell undersöktes genom modellanalys av elektroder som tagits från nya eller åldrade celler. Som metod användes en frekvensberoende modell som anpassades till tre-elektrod-impedansmätningar genom förändring av parametrar som beskriver elektrodnedbrytning. Då cellerna cyklats, visade förändringen av dessa parametrar att impedansen ökar på grund av nedbrytningsprodukter från elektrolyten som hindrar masstransporten och att det aktiva materialet i positiva elektroden spricker. En liknande modell användes också till att undersöka PAN-baserade kolfibrers förmåga att interkalera litium och resultaten visade på att den har mycket goda elektrokemiska egenskaper. / <p>QC 20130520</p>

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&amp;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 thesis investigates novel algorithms for enabling the use of first-principle electrochemical models for battery monitoring and control in advanced battery management systems (BMSs). Specifically, the fast solution and state estimation of a high-fidelity spatially resolved thermal-electrochemical lithium-ion battery model commonly referred to as the pseudo two-dimensional (P2D) model are investigated. The partial-differential algebraic equations (PDAEs) constituting the model are spatially discretised using Chebyshev orthogonal collocation enabling fast and accurate simulations up to high C-rates. This implementation of the P2D model is then used in combination with an extended Kalman filter (EKF) algorithm modified for differential-algebraic equations (DAEs) to estimate the states of the model, e.g. lithium concentrations, overpotential. The state estimation algorithm is able to rapidly recover the model states from current, voltage and temperature measurements. Results show that the error on the state estimate falls below 1% in less than 200s despite a 30% error on battery initial state-of-charge (SoC) and additive measurement noise with 10mV and 0.5&deg;C standard deviations. The parameter accuracy of such first-principle models is of utmost importance for the trustworthy estimation of internal battery electrochemical states. Therefore, the identifiability of the simpler single particle (SP) electrochemical model is investigated both in principle and in practice. Grouping parameters and partially non-dimensionalising the SP model equations in order to understand the maximum expected degrees of freedom in the problem reveals that there are only six unique parameters in the SP model. The structural identifiability is then examined by asking whether the transfer function of the linearised SP model is unique. It is found that the model is unique provided that the electrode open circuit voltage curves have a non-zero gradient, the parameters are ordered, and that the behaviour of the kinetics of each electrode is lumped together into a single parameter which is the charge transfer resistance. The practical estimation of the SP model parameters from frequency-domain experimental data obtained by electrochemical impedance spectroscopy (EIS) is then investigated and shows that estimation at a single SoC is insufficient to obtain satisfactory results and EIS data at multiple SoCs must be combined.

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

Ce mémoire est consacré à l’étude de nouveaux composites à base de Ni/Ti/Sn/Si comme matériaux d’électrodes négatives pour accumulateurs rechargeables Li-ion. Ces matériaux se présentent sous la forme d’une matrice active ou inactive électrochimiquement, enrichie avec du silicium pour former un composite nanostructuré. Ils présentent des capacités massiques supérieures à celles du carbone avec de bonnes performances en terme de capacité réversible, stabilité électrochimique, et cinétique de réaction. La mécanosynthèse a été choisie comme méthode d’élaboration de ces composites. Les propriétés physico-chimiques des composites ainsi synthétisés ont été caractérisées par diffraction des Rayons X, spectrométrie Mössbauer de 119Sn et microscopie électronique à balayage. Les caractérisations électrochimiques ont été effectuées par cyclages galvanostatiques. La complémentarité entre ces différentes techniques a permis d’analyser les mécanismes réactionnels. L’étude détaillée de ces nouveaux matériaux composites, nous a permis de mettre en évidence l’influence de la matrice et du taux d’enrichissement en silicium sur les performances électrochimiques (capacité réversible pouvant atteindre 1300 mAh.g¡1 et efficacité coulombique >99,5%). Ces matériaux présentent une grande flexibilité de composition permettant d’adapter leur capacité massique aux applications visées. / This work has been devoted to new Ni/Ti/Sn/Si based composites as negative electrode materials for lithium-ion batteries. Thesematerials are formed by tin based electrochemically active matrix and/or silicon based electrochemically inactive matrix enriched with silicon. They were obtained by ball milling method leading to nanostructured compositeswith strongly improved electrochemical performances compared to commercially used carbon. This includes reversible capacity, electrochemical stability and reaction kinetics.The composites were characterized by X-ray diffraction, 119Sn Mössbauer spectroscopy and scanning electron microscopy while their electrochemical performances were carried out by galvanostatic cycling. Finally, the reaction mechanisms were elucidated from X-ray diffraction and 119Sn Mössbauer spectroscopy used in operando mode. By combining these results with empirical models, it has been possible to optimize the composition and the synthesis conditions of the composite to improve the electrochemical properties and obtain reversible specific capacity up to 1300 mAh.g-1 with Coulombic efficiency higher than 99.5%. In addition, the composition flexibility of these materials allows to adapt their electrochemical properties to specific applications.

Made available in DSpace on 2014-06-11T19:23:26Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-07-31Bitstream added on 2014-06-13T18:09:34Z : No. of bitstreams: 1 zanatta_cs_me_bauru.pdf: 2567546 bytes, checksum: b92343b4c48fcdf306ed6a95bf902804 (MD5) / Materiais nanoestruturados vêm sendo amplamente estudados pela comunidade científica, devido às suas propriedades únicas obtidas com o controle da síntese dos materiais. Por meio do controle experimental, esses materiais podem ser utilizados em numerosas áreas, tais como na eletrônica e na fotônica. Dentre os vários métodos químicos, o processo poliol vem sendo utilizado devido à fácil obtenção de nanopartículas de óxidos e metais na sua forma elementar. O presente trabalho teve como objetivo a síntese do óxido de zinco nanoestruturado por meio do método poliol. Diferentes precursores metálicos, tais como acetato de zinco dihidratado, nitrato de zinco hexahidratado, sulfato de zinco monohidratado e cloreto de zinco anidro e diferentes tempos de permanência da síntese foram utilizados para verificar possíveis interferências dos ânions precursores na síntese e na morfologia do óxido de zinco quando obtido. Os materiais obtidos das sínteses foram caracterizados por difração de raios X (DRX), análises térmicas (TG/DTA), medidas de adsorção de gás nitrogênio, microscopia eletrônica de varredura (MEV), microscopia eletrônica de varredura de alta resolução (MEV-FEG) e cronopotenciometria. Por meio destas técnias mostrou-se a viabilidade da obtenção do óxido de zinco nanoestruturado dd maneira direta a partir do acetato de zinco, através de refluxo em etilenoglicol por 2, 4 e 8 horas seguido de lavagem e centrifugação. A menor nanoestrutura encontrada apresentou partículas com dimensão de aproximadamente 25 nm e formato poliédrico, as quais foram observadas pelo FEG. A técnica de cronopotenciometria, representada por meio das curvas de carga/descarga mostraram que a utilização do compósito contendo o óxido de zinco sintetizado apresenta melhores resultados quando comparados ao uso... / Nanostructered materials have been extensively studied by the scientific community due to their unique properties obtained by controlled synthesis of materials. By means of the control of parameters, this new materials can be used in a number of applications in electronic and photonic technology. Among the several methods to obtain nanoparticles or nanostructured materials, the polyol method has been applied because it shows easy procedures to produce nanostructured oxides and elemental metals. The aim of this work is the synthesis of nanostructured zinc oxide, one of the most multifunctional oxides, by the polyol method. Different precursors salts like zinc acetate dihydrate, zinc nitrate hexahydrate, zinc sulfate monohydrate and zinc chloride anhydrate, as well as several times of reflux, were used to investigate the influence of the precursos anions on the synthesis and on the morphology of the crystals of zinc oxide whenever produced. The obtained powders were characterized by X-ray diffraction (DRX), thermal analyses (TG/DTA), and measurements of 'N IND. 2' gas adsorption, scanning electronic and field emission microscopy (MEV and FEG) and chronopotentiometry. These techniques showed the possibility of producing nanostructured zinc oxide in direct way from the reflux in etylenglycol for 2, 4 and 8 hours, followed by washing and centrifugation. The smallest nanostructure observed by FEG presented around 25 nm polyhedral particles. The chronopotentiometry, present charge/discharge curves showing better results for the electrode made of polimer composite containing ZnO nanoparticles than the obtaining results for the oxide alone. The best results showed reversibility of the lithium-ion cell upon 20 cycles, applying 3 μΑ electric current and showing a charge potential up to 4.2 V.

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