Ces travaux ont permis d'approfondir les mécanismes de (dé)lithiation et de vieillissement dans des électrodes à base de silicium et de LiFePO4 pour accumulateurs Li-ion à partir d'observations multi-échelles. Des cartographies de phases, autant à l'échelle de la particule qu'à l'échelle de l'électrode, ont été menées par microscopie électronique mettant en évidence de fortes hétérogénéités. Pour le silicium, la mise en place de cartographie unique par STEM/EELS, s'appuyant sur une base de données des pertes faibles d'alliages sensibles à l'air et au faisceau d'électrons, a permis de comprendre les mécanismes de lithiation à l'échelle du nanomètre. L'étude de la première lithiation a montré des différences de mécanismes de réaction avec le lithium suivant deux facteurs : la taille des particules et les défauts au sein de celles-ci. Il a été observé une composition d'alliage LixSi plus faible pour les nanoparticules que pour les microparticules. Les défauts dus notamment au broyage constituent des sites préférentiels de lithiation. En vieillissement, les nanoparticules subissent de profonds changements structuraux et morphologiques, passant d'un état sphérique cristallin (50 nm) à un réseau de fils amorphe (5-10 nm d'épaisseur) contenu dans une matrice de SEI. Pour le LiFePO4, il a été clairement montré, par la combinaison de plusieurs techniques de microscopies électroniques (diffraction des électrons en précession, EFSD : Electron Forward Scattering Diffraction, EFTEM), que les particules de taille nanométrique (100-200 nm) étaient soit entièrement lithiées soit entièrement délithiées à l'équilibre thermodynamique. De fortes hétérogénéités ont été observées dans les électrodes fines comme dans les électrodes épaisses. A l'échelle des particules, l'analyse statistique de plus de 64000 particules a montré que les plus petites particules se délithient en premier. A l'échelle de l'agglomérat, les cartographies de phases ont révélé un mécanisme « cœur-coquille » : la réaction débute de la surface vers le centre des agglomérats. A l'échelle de l'électrode, le front de propagation de phase se déplace suivant des chemins préférentiels de plus grandes porosités de la surface de l'électrode vers le collecteur de courant. La conductivité ionique au sein de nos électrodes est le facteur limitant. / This work aimed at better understanding the (de)lithiation and aging mechanisms in LiFePO4 and silicon-based electrodes for Li-ion batteries from multiscale investigations. Phase mapping was performed by electron microscopy at the particle scale and at the electrode scale. This highlights some strong heterogeneities. The silicon study has shown some different lithium reaction mechanisms following two effects: particle size and crystalline defects. A smaller lithium amount in LixSi alloy was highlighted for the nanoparticles rather than for the microparticles. The defects mainly due to milling are preferential sites for the lithiation. In aging, the nanoparticles have undergone structural and morphological changes. The pristine crystalline spherical shape (50 nm) was transformed into an amorphous wire network (5-10 nm of thickness) contained in a SEI matrix. Thanks to a combination of electron microscopy techniques (precession electron diffraction, Electron Forward Scattering Diffraction, EFTEM), it was clearly shown that the LiFePO4 particles (100-200 nm) are either fully lithiated or fully delithiated at the thermodynamic equilibrium. Strong heterogeneities were observed in the thin and thick electrodes. At the nanoscale, the statistical analysis of 64000 particles unambiguously shows that the small particles delithiate in first. At the mesoscale, the phase maps reveal a core-shell mechanism at the scale of the agglomerates, from the surface to the center of these agglomerates. At the electrode scale, the phase front would move following preferential paths into the higher porosity from the surface in contact with electrolyte toward the current collector. The electrode ionic conductivity is the limiting parameter.

Les batteries au lithium tout solide présentent un grand intérêt pour le développement de systèmes de stockage de grande densité (volumique) d'énergie et sûrs notamment en raison de leur excellente stabilité thermique par rapport aux technologies lithium-ions à électrolyte liquide. Cependant, avec l'épaisseur de la batterie, de fortes limitations cinétiques sont observées, en raison i/ de la relativement faible mobilité des ions dans les matériaux inorganiques et ii/ de la présence de joints de grains généralement bloquants aux interfaces solide/solide. De plus au cours de la charge/décharge de la batterie, les matériaux actifs (réservoir de l'énergie) changent de volume ce qui induit des contraintes mécaniques interfaciales qui provoquent la formation de micro-fractures très dommageables à la cyclabilité de ces systèmes. Cette thèse concerne la réalisation et la caractérisation de batteries inorganiques monolithiques (avec les électrodes composites) en utilisant une méthode de frittage: Spark Plasma Sintering (SPS). La formulation des électrodes composites est fondamentale car ce sont de multi-matériaux qui doivent présenter de nombreuses fonctionnalités: 1) une grande densité d'énergie 2) une bonne percolation électronique (resp. ionique) enfin 3) une bonne tenue mécanique avec des interfaces électrodes/electrolyte stables afin d'assurer la durée de vie des cellules.Le principal objectif est de trouver des relations, pour des matériaux donnés, entre la texture des poudres initiales, la microstructure des céramiques obtenues par frittage SPS et les propriétés électriques (électronique et ionique) ainsi que les performances électrochimiques. / All-solid batteries with inorganic solid electrolytes are attractive candidates in electrochemical energy storage since they offer high safety, reliability and energy density. Aiming to increase the surface capacity strong efforts have been made to increase the thickness of the electrode. However, the thicker electrode, the more stress is generated at the solid/solid interfaces because of the volume change of the active material during lithium insertion/desinsertion upon cycling, which leads to formation of micro-cracks between the components and finally a bad cycling life. The possible answer to this issue is to build in place of a dense phase pure electrode, a composite electrode which is a multifunctional material. This composite electrode should contain a lot of electrochemically active material, the reservoir of energy; together with electronic and ionic conductor additives, to ensure efficient and homogeneous transfer of electrons and ions in the electrode volume.The main scope of this thesis was to develop all-solid-state batteries prepared by SPS method for applications at elevated temperatures. These batteries consist of a two composite electrodes separated by the NASICON-type solid electrolyte Li1.5Al0.5Ge1.5(PO4)3. The main objective was to find relationships, for given materials, between the initial powder granulometry (grain size, size distribution, agglomeration), the microstructure of ceramics obtained by SPS sintering, and the electrochemical performances of the final batteries. By creating electrodes with novel materials and better composition, the trade-off of power density and energy density can be minimized.

This thesis deals with a design, construciton and testing of a switch-mode power supply (SMPS) which is working as a LiFEPO4 battery charger with output current up to 100~A and output voltage up to 14,6~V. The output voltage and current can be regulated by the operator from zero to maximum value. For this SMPS Half-bridge asymmetrical forward converter with two transformers and common output inductor topology is chosen. The control circuits are run by the IC SG3525. Cascaded regulation of output voltage and current is implemented by two discrete operational amplifiers. Undervoltage protection of the control circuits and independent overcurrent protection on the primary side is also implemented.

This master’s thesis deals with the design and fabrication of DC arc welder supplied from its own rechargeable battery. Battery cells’ type is LiFePO4 which can provide high currents even at relatively low capacity. The BMS circuits are designed within the battery. Major power part of the welder is a step-down converter with synchronously switching low transistors at the position of free-wheel diode. The converter operates at 100 kHz frequency. The current of the battery welder can be regulated in the range from 0 to 120 A.

Batterimodeller används för att representera batterier. För ändamål som batterihanteringssystem används idag främst empiriska modeller som representerar ett batteri med en motsvarande kretsmodell. Några nackdelar för dessa modeller ligger i dess oförmåga att simulera interna tillstånd och en tidskrävande parametriseringsprocess. Dessa nackdelar motiverar ingenjörer att vända sig till modeller som är baserade på fysiska lagar som ett alternativ eftersom de kan ge insikt i vad som händer inuti batteriet. Batterimodellerna som är baserade på de fysiska lagarna har alltför krävande beräkningar för att kunna användas för vissa applikationer, som batterihanteringssystem. Singel-partikelmodellen (SPM) är en fysikbaserad modell som används i detta avhandlingsprojekt. Syftet med projektet var att hitta en metod för att parametrisera SPM för nya kommersiella cylindriska HTPFR18650 1100mAh 3.2V litiumjärnfosfatceller. En litteraturundersökning och experiment användes för att extrahera parametervärdena. 17 parametrar valdes från litteraturundersökningen eftersom de kunde användas för att parametrisera modellen. Geometriska parametrar hittades genom en cellöppning. Tre typer av icke-destruktiva experiment som var inspirerade av litteraturen utfördes för att extrahera värden för de andra icke-geometriska parametrarna. Ett cykeltest med låg strömhastighet utfördes för att få en pseudo-OCV-kurva och för att extrahera kapacitetsrelaterade parametrarna. En känslighetsanalys genomfördes för galvanostatisk intermittent titreringsteknik testet (GITT) och pulstestet för de parametrar som var kopplade till transportoch kinetiska fenomen. Python matematisk batterimodellering (PyBaMM) användes för att simulera experimenten. Parametersamlingen Prada 2013 användes som standardvärden. Standardvärdena för de valda parametrarna ersattes av de värden som hittades genom experiment. Känslighetsanalysen visade att några av de valda parametrarna var känsliga för experimenten medan andra inte var det. Parametrarna extraherades genom fysiska relationer och genom att anpassa parametervärde för simuleringen så att den passar den experimentella datan under urladdningsförloppet. Värden för 14 av de 17 parametrarna extraherades i metoden. Den parametriserade modellen validerades mot två potentiella applikationer, en för ett batterielfordon och den andra för ett mild-hybridfordon. Den parametriserade modellen visade att den negativa partikelradien inte kan hittas med den föreslagna parametriseringsmetoden. Simuleringen visade sig också matchade den experimentella datan bättre under urladdning av cellerna jämfört till uppladdning. Flera förbättringar för framtida arbete har föreslagits, såsom att utvidgning av känslighetsanalysen, att erhålla OCV-kurvan från GITT istället för att använda pseudo-OCVkurvan, att använda strängare gränser vid kurvanpassningarna samt att skapa mer optimala tester för att extrahera parametervärdena. / Battery models are used to represent batteries. For purposes like battery management systems, empirical based models like the equivalent circuit models are widely used. These models have downsides regarding for example inability to simulate internal states and parametrization time that make engineers look at physics-based models as an alternative. The physics-based models are made up of physical relationships that offer insights into what is happening inside the battery. These are too computationally demanding to be used for certain applications, like battery managements systems. The Single Particle Model (SPM) is a physics-based model that is utilized in this thesis project. The aim of the project is to find a method to parametrize the SPM for fresh commercial cylindrical HTPFR18650 1100mAh 3.2V lithium iron phosphate cells. Literature survey and experiments were used to extract the parameter values. 17 parameters were selected from the literature survey since they could be used to parametrize the model. Geometrical parameters were found through a cell opening. Three types of nondestructive experiments inspired by literature were performed to extract values for the other non-geometric parameters. A low-rate cycling test was performed to get pseudo-OCV curve and to extract capacity related parameters. A sensitivity analysis is done for the GITT and the Pulse test for the parameters that were connected to the transport and kinetic phenomena. Python mathematical battery modelling (PyBaMM) was used to simulate the experiments. The Prada 2013 parameter set was be used as default values. The default values for the selected parameters were replaced by the values found through experiments. The sensitivity analysis showed that some of the selected parameters were sensitive while others were not. The parameters were extracted through physical relations and through curve fitting procedures during discharge. Values for 14 out of the 17 parameters were extracted in the method. The parametrized model was validated against two potential applications, one for a battery electric vehicle and the other for a mild hybrid. The parametrized model showed that the negative particle radius cannot be found through the proposed parametrization procedure. The simulation matched the experimental data better for discharging cells than charging cells. Several improvements for future work have been suggested such as extending the sensitivity analysis, obtaining the OCV-curve from GITT instead of low-rate cycling, having stricter bounds for the curve fitting as well as creating more optimal tests to extract the parameter values.

The thesis presents a modeling framework for simulating three dimensional effects in lithium-ion batteries. This is particularly important for understanding the performance of large scale batteries used under high power conditions such as in hybrid electric vehicle applications. While 1D approximations may be sufficient for the smaller scale batteries used in cell phones and laptops, they are severely limited when scaled up to larger batteries, where significant 3D gradients can develop in concentration, current, temperature, and voltage. Understanding these 3D effects is critical for designing lithium-ion batteries for improved safety and long term durability, as well as for conducting effective design optimization studies. The model couples an electrochemical battery model with a thermal model to understand how thermal effects will influence electrochemical behavior and to determine temperature distributions throughout the battery. Several modeling example results are presented including thermal influences on current distribution, design optimization of current collector thickness and current collector tab placement, and investigation of lithium plating risk in three dimensions. / text

Lithium-ion batteries are today finding use in automobiles aiming at reducing fuel consumption and emissions within transportation. The requirements on batteries used in vehicles are high regarding performance and lifetime, and a better understanding of the interior processes that dictate energy and power capabilities is a key to strategic development. This thesis concerns aging in lithium-ion cells using electrochemical tools to characterize electrode and electrolyte properties that affect performance and performance loss in the cells.   A central difficulty regarding battery aging is to manage the coupled effects of temperature and cycling conditions on the various degradation processes that determine the lifetime of a cell. In this thesis, post-mortem analyses on harvested electrode samples from small pouch cells and larger cylindrical cells aged under different conditions form the basis of aging evaluation. The characterization is focused on electrochemical impedance spectroscopy (EIS) measurements and physics-based EIS modeling supported by several material characterization techniques to investigate degradation in terms of properties that directly affect performance. The results suggest that increased temperature alter electrode degradation and limitations relate in several cases to electrolyte transport. Variations in electrode properties sampled from different locations in the cylindrical cells show that temperature and current distributions from cycling cause uneven material utilization and aging, in several dimensions. The correlation between cell performance and localized utilization/degradation is an important aspect in meeting the challenges of battery aging in vehicle applications.   The use of in-situ nuclear magnetic resonance (NMR) imaging to directly capture the development of concentration gradients in a battery electrolyte during operation is successfully demonstrated. The salt diffusion coefficient and transport number for a sample electrolyte are obtained from Li+ concentration profiles using a physics-based mass-transport model. The method allows visualization of performance limitations and can be a useful tool in the study of electrochemical systems. / <p>QC 20140512</p>

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs.

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs.

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs.