The objective of this thesis was to investigate the suitability of some different Li4Ti5O12 materials as a negative electrode in hybrid supercapacitors. A hybrid supercapacitor is a combination of a battery and an electric double-layer capacitor that uses both a battery material and a capacitor material in the same device. The target for these combination devices is to bridge the performance gap between batteries and capacitors and enable both high energy and power density. To achieve this, materials with high capacity as well as high rate capability are needed. To improve the rate of the commonly slow battery materials nanosizing has been found to be an effective solution. This study shows that Li4Ti5O12 has a significantly higher experimental capacity than the most common capacitor material, activated carbon. The capacity remained high even at high discharge rates due to a successful nanostructuring that increased the accessibility of the material and shortened the diffusion distance for the ions, leading to a much improved power performance compared with the bulk material. The use of a nanostructured Li4Ti5O12 material in a hybrid device together with activated carbon was estimated to double the energy density compared to an electric double-layer capacitor and maintain the same good power performance. To further increase the energy density also improved materials for the positive electrode should be investigated.

The electric vehicle itself today outlives its battery, necessitating battery replacement. Lithium titanium oxide (LTO) has, in this context, been suggested as a new anode material in heavy electric vehicle applications due to intrinsic properties regarding safety, lifetime and availability. The work presented here is focused on the LTO electrode/electrolyte interface. Photoelectron spectroscopy (PES) has been applied to determine how and if the usage of LTO could prevent extensive anode-side electrolyte decomposition and build-up of a surface layer. The presence of a solid electrolyte interphase (SEI) comprising LiF, carbonates and ether compounds was found in half-cells utilizing a standard ethylene:diethylcarbonate electrolyte with 1 M LiPF6. Via testing of symmetrical LTO-LTO cells, the stability of the formed SEI was put in to question. Moreover, the traditional polyvinylidene difluoride (PVdF) binder was replaced by more environmentally benign carboxylmethyl cellulose (CMC) and polyacrilic acid (PAA) binders in LTO electrodes, and it was found that CMC helped to form a more stable surface-layer that proved beneficial for long term cycling. Following the half-cell studies, full-cells were investigated to observe how different cathodes influence the SEI of LTO. The SEI in full-cells displayed characteristics similar to the half-cells, however, when utilizing a high voltage LiNi0.5Mn1.5O4 cathode, more electrolyte decomposition could be observed. Increasing the operational temperature of this battery cell generated even more degradation products on the LTO electrodes. Mn was also found on the anode when using Mn-based cathodes, however, it was found in its ionic state and did not significantly affect the composition or behavior of the observed SEI layer. Furthermore, by exchanging the electrolyte solvent for propylene carbonate, the thickness of the SEI increased, and by replacing the LiPF6 salt for LiBF4 the stability of the SEI improved. Thus is it demonstrated that such a passivation can be beneficial for the long-term surface stability of the electrode. These findings can therefore help prolong the lifetime of LTO-based battery chemistries.

En raison de leur faible pression de vapeur et de leur stabilité électrochimique (5~6 V) et thermique, les dinitriles N≡C-(CH2)n-C≡N sont proposés comme solvants d’électrolytes alternatifs aux carbonates d’alkyles habituellement utilisés dans les batteries Li-ion. L’objectif de cette thèse est d’étudier le comportement physico-chimique de ces électrolytes alternatifs (viscosité, conductivité ionique, comportement thermique, propriétés volumétriques, etc.) et leur compatibilité avec une application dans les batteries Li-ion. Deux systèmes de batteries sont étudiés en utilisant une électrode positive d’oxyde lamellaire (LiNi1/3Mn1/3Co1/3O2) associée à une électrode négative à bas potentiel (graphite) ou à plus haut potentiel (Li4Ti5O12). La cyclabilité des électrodes en demi-pile et en pile complète est étudiée en fonction de la composition de l’électrolyte et de la nature du dinitrile utilisé. Les techniques de caractérisations suivantes : spectroscopie d’impédance électrochimique, microscopie électronique et spectroscopie de photoélectrons aux rayons X, sont utilisées pour suivre le processus de passivation des électrodes par formation d’une interface solide (SEI). L’effet de la présence d’additifs favorisant la formation de la couche de passivation a été étudié et leur efficacité est ainsi clairement mise en évidence. / Due to their low vapor pressure as well as their electrochemical (5~6 V) and thermal stability, dinitriles N≡C-(CH2)n-C≡N are proposed as alternative electrolyte solvents to alkyl carbonates commonly used in Li- ion batteries. The objective of this thesis is to study the physico-chemical behavior of these alternative electrolytes (viscosity, ionic conductivity, thermal behavior, volumetric properties, etc.) and their use in Li-ion batteries. Two battery systems are studied using a lamellar oxide (LiNi1/3Mn1/3Co1/3O2) as positive electrode associated with graphite or Li4Ti5O12 as negative electrodes. The cyclability of electrodes in half-cell and full-cell is studied according to the electrolyte composition and the nature of the dinitrile used. Characterization techniques like: electrochemical impedance spectroscopy, electron microscopy and X-Ray photoelectrons spectroscopy, are used to study the passivation of the negative electrode and the stability of the positive electrode. The effect of adding specific solid electrolyte interphase (SEI) builders is investigated and their efficiency is hence clearly demonstrated.

Les batteries lithium-ion (Li-ion) sont privilégiées dans de nombreuses applications comme solution de stockage de l’énergie. Le composé Li4Ti5O12 (LTO) est une alternative au graphite qui demeure majoritairement utilisé comme matériau d’électrode négative dans les batteries Li-ion. Pour de potentielles applications à haute température, il est nécessaire d’étudier les couches interfaciales qui se forment dans ces conditions en surface des électrodes LTO. En effet, la formation de telles couches est un phénomène commun aux batteries Li-ion, dont la maîtrise revêt un rôle fondamental pour l’obtention de bonnes performances électrochimiques. La surface des électrodes LTO a pour cela été principalement caractérisée par Spectroscopie Photoélectronique à rayonnement X (XPS) et des analyses complémentaires ont aussi été ponctuellement menées en microscopie Auger à balayage (Scanning Auger Microscopy : SAM) pour l’acquisition de cartographies élémentaires et en spectrométrie de masse d’ions secondaires à temps de vol (Time-of-Flight Secondary Ions Spectrometry : ToF-SIMS) pour établir des profils de concentration élémentaires et moléculaires en profondeur. Ces résultats ont été systématiquement confrontés aux données électrochimiques. L’influence de différents paramètres sur les propriétés de la couche interfaciale formée en cyclage face au lithium a été évaluée. Une comparaison des couches interfaciales formées au premier cycle à température ambiante, 60 °C et 85 °C a ainsi montré qu’une température de cyclage plus élevée favorise la formation d’une couche interfaciale plus épaisse. L’utilisation d’un électrolyte contenant l’additif VC accélère la formation d’une SEI plus épaisse dès le premier cycle, moins sujette au phénomène de dissolution au cours de la délithiation et susceptible d'améliorer la rétention de capacité en longs cyclages. La substitution du sel de lithium LiPF6 par le sel LiTFSI entraîne la formation d’une couche plus fine, ce qui est principalement dû à une quantité de LiF déposée plus faible. De manière similaire, la substitution des solvants EC:DMC par les solvants PC:EMC, induit la formation d’une couche plus fine, du fait d’une quantité moins importante de LiF déposée. Par ailleurs, plus la surface spécifique de l’additif carboné entrant dans la composition des électrodes est élevée, plus la part de LiF parmi les espèces de la couche interfaciale formée est élevée, sans que cela n’influence son épaisseur. Puis, le comportement des interfaces électrode/électrolyte dans une batterie LiMn2O4/Li4Ti5O12 a finalement été étudié. Une couche interfaciale se forme en surface des deux électrodes. Néanmoins la couche formée sur l’électrode positive est plus fine que celle formée sur l’électrode négative. Leur composition est similaire, à l’exception du composé MnF2 uniquement détecté sur l’électrode négative et provenant d’un phénomène de dissolution du matériau LiMn2O4. Un prolongement de ce travail peut être envisagé concernant des électrodes à base de particules LTO avec différents coatings. De plus, une synergie systématique entre les trois techniques utilisées dans cette thèse pourra être encouragée. / Lithium-ion (Li-ion) batteries have been considered as the solution of choice for energy storage in numerous applications. Li4Ti5O12 (LTO) compound is an alternative to the widely used graphite, as a negative electrode material. For potential high temperature applications, the study of interfacial layers formed on top of LTO electrodes in such conditions is a necessary step. The formation of such surface layers is commonly observed in lithium-ion batteries and their properties are critical for maintaining good batteries performances. Therefore, LTO electrodes surfaces were mainly analyzed by X-ray Photoelectron Spectroscopy (XPS) and complementary measurements were performed by Scanning Auger Microscopy (SAM) for the acquisition of elemental mappings and by Time-of-Flight Secondary Ions Spectrometry (ToF-SIMS) for depth profile analysis. Surface analysis results were systematically linked to electrochemical data. The influence of several parameters was investigated for LTO electrodes cycled versus lithium. The comparison of surface layers formed during the first cycle at room temperature, 60 °C and 85 °C showed that higher cycling temperatures induce the formation of a thicker layer. The use of a VC-containing electrolyte accelerates the formation of a thicker layer since the first cycle, less prone to dissolution during delithiation and susceptible to enhance the capacity retention for long cycling. Substitution of LiPF6 lithium salt by LiTFSI leads to the formation of thinner layer, which is mainly due to a lower amount of deposited LiF. Similar results are obtained for the substitution of EC:DMC solvants by PC:EMC. Furthermore, the higher the specific surface of the electrode carbonaceous additive is, the higher the share of LiF in the interfacial layer composition is, even if its thickness remains similar. Finally, the behavior of electrode/electrolyte interfaces was studied in a LiMn2O4 /Li4Ti5O12 full cell. Interfacial layers are formed on the surface of both electrodes. Nevertheless, the layer on the positive electrode is thinner than the one on the negative electrode. Their composition are similar except for MnF2 compound, coming from LiMn2O4 dissolution at the positive electrode, which is only detected on the negative electrode. This work could be continued with the study of electrodes based on coated LTO particles. Moreover, a greater synergy between three characterization techniques used in this work could be promoted.

This thesis develops a time-domain integrated modeling approach for design of hybrid-electric marine propulsion systems that enables co-simulation of powertrain dynamics along with ship hydrodynamics. This work illustrates the model-based design and analysis methodology by performing a case study for an EV conversion of a short-cross ferry using the BC Ferries’ M.V. Klitsa. A data acquisition study was performed to establish the typical mission cycle of the ship for its crossing route between Brentwood Bay and Mill Bay, across the Saanich Inlet near Victoria, BC Canada. The data provided by the data acquisition study serves as the primary means of validation for the model’s ability to accurately predict powertrain loads over the vessel’s standard crossing. This functionality enables model-based powertrain and propulsion system design optimization through simulation to intelligently deploy hybrid-electric propulsion architectures. The ship dynamics model is developed using a Newton-Euler approach which incorporates hydrodynamic coefficient data produced by potential flow solvers. The radiation forces resulting from vessel motion are fit to continuous time-domain transfer functions for computational efficiency. The ship resistance drag matrix is parameterized using results from uRANS CFD studies that span the operating range of the vessel. A model of the existing well-mounted azimuthing propeller is developed to predict thrust production and mechanical torque for pseudo-second quadrant operation to represent all operating conditions seen in real operation. The propeller model is parameterized from the results of a series of uRANS CFD on the propeller geometry. A full battery-electric powertrain model is produced to study the accuracy of the model in predicting the drivetrain loads, as well as assessing the technological feasibility of an EV conversion for this particular vessel. A dual-polarization equivalent circuit model is created for a large-scale LTO battery pack. An average value model with MTPA control and dynamics loss model is developed for a commercially available electric drive system. Power loss models were developed for required converter topologies for computational efficiency. The model results for load prediction are compared to data acquired, and results indicate that the approach is effective for enabling the study of various powertrain architecture alternatives. / Graduate

This thesis deals with description of preparation and use of monomers and copolymers for gel polymer electrolytes usable in electrochemical power sources. This thesis is divided in theoretical and experimental part. The theoretical part describes electrolytes focused on gel polymer electrolytes, measuring methods and materials used for experiments. The experimental part deals with calculation of composition of polymer electrolytes, method of preparation and evaluation of measured results. The method of applying GPE to a negative LTO electrode and a positive NMC electrode is described too. Linear Sweep Voltammetry (LSV) and Potentiostatic Electrochemical Impedance Spectroscopy (PEIS), Cyclic Voltammetry (CV) and Galvanostatic Cycling with Potential Limitation (GCPL) were chosen for measurement of properties.

Le fonctionnement des batteries lithium-ion, qu’il soit normal ou dans des conditions abusives, est accompagné d’une génération de gaz en particulier lors des premiers cycles. Celle-ci est intrinsèque au dispositif et est soumise à de nombreux paramètres tels que les matériaux d’électrodes utilisés, l’électrolyte ou encore les conditions opératoires. Cette génération de gaz est délétère : elle conduit à l’augmentation de la pression interne des batteries et pose donc des problèmes de sécurité. Cette étude vise à quantifier les volumes de gaz générés et à comprendre les mécanismes liés à la surpression dans les batteries. A cet effet, le format de batterie « pouch cell » a été adopté tout au long de ce travail de thèse. L’électrolyte choisi est le mélange EC:PC:3DMC + 1 mol.L-1 LiPF6. La première partie de ce travail est dédiée à la mise au point d’un protocole expérimental basé sur (i) l’analyse des matériaux d’électrodes (NMC, LFP, Gr, et LTO), (ii) la solubilité de gaz (O2, H2) comparées à (CO2, CH4) par PVT, et (iii) la quantification des volumes de gaz générés durant le cyclage en pouch cell, corrélée aux performances électrochimiques. Une analyse préalable en demi-piles et en dispositifs complets Gr//NMC et LTO//LFP a également été réalisée afin d’anticiper les performances attendues en pouch cells. Une analyse critique des données (de la littérature et de nos mesures) a permis de définir une procédure optimisée pour obtenir des résultats reproductibles et comparables lors des mesures de volume en pouch cells. La seconde partie de cette thèse consiste en la quantification du volume de gaz produit au cours du cyclage des pouch cells Gr//NMC, Gr//LFP, LTO//LFP et LTO//NMC. Ainsi, les tensions de fin de charge, l’effet du sel et de la température ont été discutés pour dégager les paramètres déterminants dans la génération de gaz en particulier lors de la formation de la SEI. Enfin, une analyse de la composition du gaz récupéré a été effectué par GC-MS et FTIR. A partir de résultats obtenus, des mécanismes ont été proposés et discutés. / The functioning of lithium-ion batteries, may it be under normal use or under abusive conditions, is accompanied by gas generation, especially during the first cycles. This extent of gas generation is dependent on the choice of electrode materials, the electrolyte, and the operating conditions. This gas generation is detrimental: the build-up of pressure leads to the over-pressure in the battery, raising serious concerns. This study is aimed at understanding the fundamental mechanisms governing these reactions. To do so, the « pouch cell » configuration was adopted throughout this thesis. The electrolyte we worked on is the mixture EC:PC:3DMC + 1 mol.L-1 LiPF6. The first chapter of this work is dedicated to development of an experimental protocol based on (i) the analysis of the electrodes materials (NMC, LFP, Gr and LTO), (ii) the gas solubilities (O2, H2) compared to (CO2, CH4) by PVT method, and (iii) the quantification of the volume of generated gases during the cycling of pouch cells which was correlated to the electrochemical performances. A preliminary analysis of half-cells and full cells Gr//NMC and LTO//LFP were also conducted to foresee the performances of the pouch cells. A critical analysis of data taken from the literature and from our own experiments enabled the optimization of a proper procedure to get reproducible and comparable results. The second part of this thesis consists in the quantification of the volume of gases generated during the cycling of Gr//NMC, Gr//LFP, LTO//LFP and LTO//NMC pouch cells. In that respect, the voltages of the end of charge and the effect of salt and of temperature were discussed to figure out the essential parameters in the gas generation and in particular during the formation of SEI. Lastly, a compositional analysis of gases was performed using GC-MS and FTIR. Based on those results, a mechanism is proposed and discussed herein.

Litiumjon-batterier har blivit väldigt populära för tillämpning i fordon. Den här teknologin har fler olika kemier att erbjuda som kontinuerligt förbättras. Litium-titanat-oxid-batterier använder (LTO) LTO som anod och erbjuder långt cyklingsliv samt minskar risk för SEI-bildning och litiumplätering.  Det här examensarbetet siktade på att undersöka om LTO-batterier kan användas som startbatterier i kommersiella fordon. Metodologin inkluderade två motorstart försök med en kommersiell 12s1p LTO-modul, laddnings/urladdningtester med en kommersiell LTO-cell med nominell spänning 2.3V samt överurladdningstester med byggda pouchceller. Materialet för pouchceller extraherades från en kommersiell LTO-cell och sedan studerades med SEM-EDX före och efter överurladdningstesterna. Resultatet visade att LTO-batterier kan användas som startbatterier i en diesel V8 motor även vid 39%SoC. Dessutom visade simuleringar att LTO-batterier kan användas inom Kinetic Energy Recovery System (KERS) tillämpning och behålla 60% SoC efter 500 laddning/urladdnings cykler. Resultaten från både KERS och motorstarterna visade att LTO är en lovande kandidat för ersättning av blybatterier. Laddnings/urladdnings tester visade att en kommersiell 12s1p LTO modul kan maximalt uppnå 73%SoC när den laddas med fordon-liknande strömmar. Däremot var SoC oberoende av laddningsström. Överurladdningstester med pouchceller visade att det är relativt ofarligt att urladda LTO 0.4V under spänningsgränsen utan stora ökningar i impedans eller stor kapacitetsförlust. Största förluster kopplades till åldring av NMC-baserade positiva elektroden. / Lithium ion batteries have become quite popular in vehicle applications in the past few decades. This technology offers multiple chemistries to choose from, that are continuously studied and improved. Lithium-titanate-oxide (LTO) batteries use LTO material as an anode, providing long cycling life, as well as essentially eliminating risk for SEI formation and lithium plating.  This Master thesis project aimed to investigate how well LTO-based lithium-ion batteries can perform in Start Ignition Lighting (SLI) application in commercial vehicles. The methodology included two engine crank tests with a commercial 12s1p LTO module, charge/discharge tests on a commercial LTO cell with nominal voltage 2.3V, as well as overdischarge cycling tests on assembled pouch cells. The materials for the pouch cells were extracted from a commercial LTO cell and later analysed with SEM-EDX before and after overdischarge tests. The results demonstrated that LTO-based Li-ion batteries can be successfully start a diesel V8 engine even at 39% SoC. Furthermore, when simulating an urban vehicle with an implemented Kinetic Energy Recovery System (KERS) application, a commercial cell LTO cell achieved and retained around 60\%SoC throughout 500 charge/discharge cycles. Combined results from KERS and engine start tests imply that LTO is a strong candidate for replacing lead-acid in these applications. Charge/discharge tests showed that commercial 12s1p LTO cell can maximum reach around 73%SoC when charged in a vehicle-like way. However, this maximum SoC limit was more or less independent of applied charging current. Furthermore, electrochemical overdischarge tests on the pouch cells demonstrated that it is relatively safe to overdischarge the cell 0.4V below the specified safety limit without significant rise in impedance or capacity fade. Major performance losses were attributed to the aging of the NMC-based positive electrode.

The thesis deals with the influence of low-flammable electrolytes on negative electrodes. The thesis describes materials used in lithium-ion batteries and functions of individual components. There is also a description of conductometry and electron microscopy, which is used in the practical part, ie during measurement. All findings are summarized at the end of the thesis.

This thesis deals with a study of lithium-ion batteries. It is focused into negative electrode materials and electrolytes. In this thesis is presented synthesis, electrochemical properties, possibilities to improving negative electrode materials as LTO (Lithium Titanate Oxid) and graphite. These electrode materials were investigated with respect to their compatibility at electrolytes with carbonate solvents, Sulfolane and DMF (DiMethylFormamide) in detail. The main aim of this thesis is to characterize electrode materials and electrolyte properties depending on wide range of temperatures and their comparison for the purpose of achievement of the best solution. The thesis is divided into two main parts. The theoretical part of thesis describes composition, process of synthesis and analysis of lithium-ion cell. Practical part contains measuring and evaluating of charge-discharge and irreversible capacity characteristics related to variety of environmental temperatures.