La mise en œuvre de nouvelles formulations d’électrolytes adaptées à des électrodes positives à haut potentiel pour batterie lithium-ion est un défi majeur pour des systèmes à haute densité d’énergie. Afin d’obtenir une stabilité en oxydation supérieure à 5 V vs. Li+/Li, différents solvants (dinitriles, lactones, phosphates) ont été analysés. Nous avons montré par voltampérométrie cyclique que des électrolytes contenant du sébaconitrile sont stables jusqu’à 5,3 V vs. Li+/Li sur LiCoPO4. Toutefois, les résultats obtenus par impédance électrochimique et spectroscopie photoélectronique X ont révélé la présence d’une nouvelle interface à l’électrode positive issue de la dégradation de l’électrolyte. Bien que cette dégradation limite la cyclabilité, une optimisation de l’interface formée pourrait s’avérer un atout du point de vue de la sûreté du système grâce à une protection de l’électrode positive. / Implementation of new electrolyte formulations adapted to high potential positive electrodes for lithium-ion battery is a key challenge for high energy density systems. In order to obtain stability in oxidation greater than 5 V vs. Li+/Li, various solvents (dinitriles, lactones, phosphates) were analyzed. We have shown by cyclic voltammetry that electrolytes containing sebaconitrile are stable up to 5.3 V vs. Li+/Li on LiCoPO4. Nonetheless, the results obtained by electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy revealed the presence of a new interface onto the positive electrode due to electrolyte degradation. Even though this degradation limits the cycle ability, optimization of the formed interface could be an asset in view of the system safety through the protection of the positive electrode.

Ce mémoire est consacré à l'étude théorique des matériaux de cathode pour batteries Li-ion de structure olivine LiMPO4 (M=Mn, Fe, Co, Ni), des phases délithiées MPO4 et des phases mixtes LiFexMn1-xPO4, FexMn1-xPO4 et LiFexCo1-xPO4. La stabilité des phases magnétiques et les paramètres de maille théoriques ont été déterminés par la méthode des pseudopotentiels et comparés aux données expérimentales. Les structures électroniques ont été calculées par une méthode « tout électron » et analysées en termes d'hybridation des orbitales atomiques Ces résultats ont permis d'interpréter les spectres de photoélectrons X et d'absorption des rayons X, en particulier les modifications réversibles associées aux cycles de lithiation/délithiation. Les effets de la polarisation de spin et de la corrélation électronique ont été discutés. Enfin, le calcul des paramètres Mössbauer du 57Fe a montré qu'un accord quantitatif entre les résultats théoriques et les données expérimentales nécessitait la prise en compte de ces deux effets. Ce type de calcul a permis de prédire et d'expliquer que la transformation LiFePO4FePO4 s'accompagnait de la variation du gradient de champ électrique Vzz d'une extrémité à l'autre de l'échelle Mössbauer pour 57Fe. / This thesis is devoted to the theoretical study of the cathode materials for Li-ion batteries with olivine structure LiMPO4 (M=Mn, Fe, Co, Ni), the delithiated phases MPO4 and the mixed phases LiFexMn1-xPO4, FexMn1-xPO4 and LiFexCo1-xPO4. The magnetic phase stability and lattice parameters were theoretically determined from pseudopotential calculations and the results have been compared with experiments. Electronic structures were obtained from all electron calculations and analyzed in terms of orbital hybridization. The results have been used for the interpretation of X-ray photoemission and X-ray absorption spectra, especially changes due to lithiation/delithiation cycles. Effects of spin polarization and electronic correlation on the electronic structures have been also discussed. It has been shown that ab initio calculations of the 57Fe Mössbauer parameters also require these two effects in order to obtain a quantitative agreement with experiments. Finally, it was found that LiFePO4FePO4 transformation involves a dramatic change of the electric field gradient VZZ from one end to the other of the 57Fe Mössbauer scale.

Lithium Ion Batteries (LIBs) are important in today's society, powering cars and mobile devices. LIBs consist of a negative anode commonly made of graphite, and a positive cathode commonly made from transition metal oxides. Between these electrodes are separators and organic solvent based electrolyte. Due to the high potential of LIBs the electrolyte is reduced at the anode. The electrolyte reduction results in the formation of a layer called the Solid Electrolyte Interphase (SEI), which prohibits the further breakdown of the electrolyte. Despite being researched for over50 years, the composition formation of the SEI is still poorly understood. The aim of this project is to develop strategies for efficient identification and classification of various active and intermediate components in the SEI, to, in turn, gain an understanding of the reactions taking place, which will help find routes to stabilize and tailor the composition of the SEI layer for long-term stability and optimal battery performance. For a model gold/li-ion battery electrolyte system, Raman spectra will be obtained using Surface Enhanced Raman Spectroscopy (SERS) in a spectroelectrochemical application where the voltage of the working gold electrode is swept from high to low potentials. Spectra of common components of the SEI as well as similar compounds will be simulated using Density Functional Theory (DFT). The DFT data is also used to calculate the spontaneity of reactions speculated to form the SEI. The simulated data will be validated by comparing it to experimental spectra from pure substances. The spectroelectrochemical SERS results show a clear formation of Li-carbonate at the SERS substrate, as well as the decomposition of the electrolyte into other species, according to the simulated data. It is however shown that there are several issues when modelling spectra, that makes it harder to correlate the simulated spectra with the spectroelectrochemical spectra. These issues include limited knowledge of the structure of the compounds thought to form on the anode surface, and incorrect choices in simulational parameters. To solve these issues, more work is needed in these areas, and the spectroelectrochemical methods used in this thesis needs to be combined with other experimental methods to narrow down the amount of compounds to be modelled. More work is also needed to avoid impurities in the electrolyte. Impurities leads to a thick inorganic layer which prohibits the observation of species in the organic layer.

<p>Lithium ion batteries have been regarded as one of the most promising and intriguing energy storage devices in modern society since 1990s. A lithium ion battery contains three main components, cathode, anode, and electrolyte, and the performance of battery depends on each component and the compatibility between them. Electrolyte acts as a lithium ions conduction medium and two electrodes contribute mainly to the electrochemical performance. Generally, cathode is the limiting factor in terms of capacity and cell potential, which attracts significant research interests in this field.Different from conventional slurry thick film cathodes with additional electrochemically inactive additives, binder-free thin film cathode has become a promising candidate for advanced high-performance lithium ion batteries towards applications such as all-solid-state battery, portable electronics, and microelectronics. However, these electrodes generally require modifications to improve the performance due to intrinsically slow kinetics of cathode materials. </p> <p>In this thesis work, pulsed laser deposition has been applied to design thin film cathode electrodes with advanced nanostructures and improved electrochemical performance. Both single-phase nanostructure designs and multi-phase nanocomposite designs are explored. In terms of materials, the thesis focuses on manganese based layered oxides because of their high electrochemical performance. In Chapter 3 of the nanocomposite cathode work, well dispersed Au nanoparticles were introduced into highly textured LiNi_0.5Mn_0.3Co_0.2O₂(NMC532) matrix to act as localized current collectors and decrease the charge transfer resistance. To further develop this design, in Chapter 4, tilted Au pillars were incorporated into Li₂MnO₃ with more effective conductive Au distribution using simple one-step oblique angle pulsed laser deposition. In Chapter 5, the same methodology was also applied to grow 3D Li₂MnO₃ with tilted and isolated columnar morphology, which largely increase the lithium ion intercalation and the resulted rate capability. Finally, in Chapter 6, direct cathode integration of NMC532 was attempted on glass substrates for potential industrial applications. </p>

Department of Chemistry / As an alternative energy source, lithium ion batteries have become increasingly important with a wide range of applications in industry, and many international companies are investing in this big project. This study was aimed at the development of safer lithium-ion power sources by using new organic additives to overcome the possible safety problems. In this study, the conformations and energies of several synthesized boronates were investigated through computational study using density functional theory (DFT) with the Becke’s three-parameter hybrid method utilizing the Lee-Young-Parr correlation functional (B3LYP). After initial energy optimization using Møller-Plesset Perturbation theory (MP2), the conformational preferences and energetics in vacuo were investigated using DFT calculations and the 6-31G(d,p) basis set. Subsequently, cyclic voltammetry and electrochemical impedance spectroscopy were used to characterize the compounds in terms of their usefulness as electrolyte additives. At least two of these show excellent promise for use in lithium-ion batteries.

Natural graphite from cheap and abundant natural sources is an attractive anode material for lithium ion batteries. We report on modifications of such a common natural graphite, whose electrochemical performance is very poor, with solutions of (NH4)2S2O8, concentrated nitric acid, and green chemical solutions such of e.g. hydrogen peroxide and ceric sulfate. These treatments resulted in markedly im-proved electrochemical performance (reversible capacity, coulombic efficiency in the first cycle and cycling behavior). This is attributed to the effective removal of active defects, formation of a new dense surface film consisting of oxides, improvement of the graphite stability, and introduction of more nanochannels/micropores. These changes inhibit the decomposition of electrolyte solution, pre-vent the movement of graphene planes along a-axis direction, and provide more passage and storage sites for lithium. The methods are mild, and the uniformity of the product can be well controlled. Pilot experiments show promising results for their application in industry.

Indiana University-Purdue University Indianapolis (IUPUI) / In the last years, lithium-ion batteries (LIBs) have become the most important energy storage system for consumer electronics, electric vehicles, and smart grids. The development of lithium-ion batteries (LIBs) based on current practice allows an energy density increase estimated at 10% per year. However, the required power for portable electronic devices is predicted to increase at a much faster rate, namely 20% per year. Similarly, the global electric vehicle battery capacity is expected to increase from around 170 GWh per year today to 1.5 TWh per year in 2030--this is an increase of 125% per year. Without a breakthrough in battery design technology, it will be difficult to keep up with the increasing energy demand. To that end, a design methodology to accelerate the LIB development is needed. This can be achieved through the integration of electro-chemical numerical simulations and machine learning algorithms. To help this cause, this study develops a design methodology and framework using Simcenter Battery Design Studio® (BDS) and Bayesian optimization for design and optimization of cylindrical cell type 18650. The materials of the cathode are Nickel-Cobalt-Aluminum (NCA)/Nickel-Manganese-Cobalt-Aluminum (NMCA), anode is graphite, and electrolyte is Lithium hexafluorophosphate (LiPF6). Bayesian optimization has emerged as a powerful gradient-free optimization methodology to solve optimization problems that involve the evaluation of expensive black-box functions. The black-box functions are simulations of the cyclic performance test in Simcenter Battery Design Studio. The physics model used for this study is based on full system model described by Fuller and Newman. It uses Butler-Volmer Equation for ion-transportation across an interface and solvent diffusion model (Ploehn Model) for Aging of Lithium-Ion Battery Cells. The BDS model considers effects of SEI, cell electrode and microstructure dimensions, and charge-discharge rates to simulate battery degradation. Two objectives are optimized: maximization of the specific energy and minimization of the capacity fade. We perform global sensitivity analysis and see that thickness and porosity of the coating of the LIB electrodes that affect the objective functions the most. As such the design variables selected for this study are thickness and porosity of the electrodes. The thickness is restricted to vary from 22microns to 240microns and the porosity varies from 0.22 to 0.54. Two case studies are carried out using the above-mentioned objective functions and parameters. In the first study, cycling tests of 18650 NCA cathode Li-ion cells are simulated. The cells are charged and discharged using a constant 0.2C rate for 500 cycles. In the second case study a cathode active material more relevant to the electric vehicle industry, Nickel-Manganese-Cobalt-Aluminum (NMCA), is used. Here, the cells are cycled for 5 different charge-discharge scenarios to replicate charge-discharge scenario that an EVs battery module experiences. The results show that the design and optimization methodology can identify cells to satisfy the design objective that extend and improve the pareto front outside the original sampling plan for several practical charge-discharge scenarios which maximize energy density and minimize capacity fade.

This thesis aims at formulating and validating models for electrochemical energy storage devices. More specifically, the devices under consideration are lithium ion batteries and polymer electrolyte fuel cells. A model is formulated to describe an experimental cell setup consisting of a LixNi0.8Co0.15Al0.05O2 composite porous electrode with three porous separators and a reference electrode between a current collector and a pure Li planar electrode. The purpose of the study being the identification of possible degradation mechanisms in the cell, the model contains contact resistances between the electronic conductor and the intercalation particles of the porous electrode and between the current collector and the porous electrode. On the basis of this model formulation, an analytical solution is derived for the impedances between each pair of electrodes in the cell. The impedance formulation is used to analyse experimental data obtained for fresh and aged LixNi0.8Co0.15Al0.05O2 composite porous electrodes. Ageing scenarios are formulated based on experimental observations and related published electrochemical and material characterisation studies. A hybrid genetic optimisation technique is used to simultaneously fit the model to the impedance spectra of the fresh, and subsequently also to the aged, electrode at three states of charge. The parameter fitting results in good representations of the experimental impedance spectra by the fitted ones, with the fitted parameter values comparing well to literature values and supporting the assumed ageing scenario. Furthermore, a steady state model for a polymer electrolyte fuel cell is studied under idealised conditions. The cell is assumed to be fed with reactant gases at sufficiently high stoichiometric rates to ensure uniform conditions everywhere in the flow fields such that only the physical phenomena in the porous backings, the porous electrodes and the polymer electrolyte membrane need to be considered. Emphasis is put on how spatially resolved porous electrodes and nonequilibrium water transport across the interface between the gas phase and the ionic conductor affect the model results for the performance of the cell. The future use of the model in higher dimensions and necessary steps towards its validation are briefly discussed.

<p>  </p> <p>Fossil fuel has dominated the global energy market for centuries, and the world is undergoing a great energy revolution from fossil fuel energy to renewable energies, given the concerns on global warming and extreme weather caused by the emission of carbon dioxide. Lithium ion batteries (LIBs) play an irreplaceable role in this incredible energy transition from fossil energy to renewable energy, given their importance in energy storage for electricity grids and promoting the mass adoption of battery electric vehicles (BEVs). Extreme fast charging (XFC) of LIBs, aiming to shorten the charging time to 15 minutes, will significantly improve their adoption in both the EV market and grid energy storage. However, XFC has been significantly hindered by the relatively sluggish Li+ transport within LIBs.</p> <p>Herein, effects caused by increasing charging rates (from 1C, 4C to 6C) on LiNi0.6Mn0.2Co0.2O2 (NMC622) || graphite cell were systematically probed via various characterization methods. From electrochemical test on their rate/long term cycling performance, the significant decrease in available capacity under high charging rates was verified. Structural evolutions of cycled NMC622 cathode and graphite anode were further probed via ex-situ powder diffraction, and it was found that lattice parameters <em>a</em> and <em>c</em> of NMC622 experience irreversible evolution due to loss of active Li+ within NMC622; no structural evolution was found for the graphite anode, even after 200 cycles under 6C (10 minutes) high charging rates. The aging behavior of liquid electrolyte was further analyzed via inductively coupled plasma-optical emission spectrometry (ICP-OES) and gas chromatography-mass spectrometry (GC-MS), increased Li+ concentration under higher charging rates and show-up of diethyl carbonate (DEC) and dimethyl carbonate (DMC) caused by transesterification both suggest faster aging/degradation of liquid electrolyte under higher charging rates.  </p> <p>Given the structural evolution of NMC622 caused by irreversible Li+ loss after long term cycling, the structural evolution of both NMC622 cathode and lithiated graphite anode were further studied via operando neutron diffraction on customized LiNi0.6Mn0.2Co0.2O2 (NMC622) || graphite cell. Via a quantitative analysis of collected Bragg peaks for NMC622 and lithiated graphite anode, we found the rate independent structural evolution of NMC622: its lattice parameters <em>a</em> and <em>c</em> are mainly determined by Li+ contents within it (<em>x</em> within Li<em>x</em>Ni0.6Mn0.2Co0.2O2) and follow the same evolution during the deintercalation process, from slowest 0.27 C charging to the fastest 4.4 C charging. For graphite intercalated compounds (GICs) formed during Li+ intercalating into graphite, the sequential phase transition from pure graphite → stage III (LiC30) → stage II (LiC12) → stage I (LiC6) phase under 0.27 C charging is consistent with previous studies. This sequential phase transition is generally maintained under increasing charging rates, and the co-existence of LiC12 phase and LiC6 was found for lithiated graphite under 4.4 C charging, mainly due to the large inhomogeneity under these high charging rates. Meanwhile, for the stage II (LiC12) → stage I (LiC6) transition, which contributes half the specific capacity for the graphite anode, quantitative analysis via Johnson-Mehl-Avrami-Kolmogorov (JMAK) model suggests it to be a diffusion-controlled, one-dimensional transition, with decreasing nucleation kinetics under increasing charging rates. </p> <p>Based on the LiC12 → LiC6 transition process, strategies to improve the Li+ transport properties were further utilized. Various cosolvents with smaller viscosity, from dimethyl carbonate (DMC), ethyl acetate (EA), methyl acetate (MA) to ethyl formate (EF), were further tested by replacing 20% (weight percent) ethyl methyl carbonate (EMC) of typical 1.2 M LiPF6 salt solvated in ethylene carbonate (EC)/EMC solvents (with a weight ratio of 30:70). From the measurement of their ion conductivity, the introduction of these cosolvents indeed enhanced the Li+ transport properties. This was further verified by improved rate performance from 2C, 3C to 4C charging for liquid electrolytes using these cosolvents. Both X-ray absorption spectroscopy (XAS) and X-ray powder diffraction (XRD) indicated the increase of Ni valence state and structural evolution of NMC622, all resulting from the irreversible loss of active Li+ within the NMC622 cathode. From long term cycling performance and further analysis of interfaces formed between electrode and anode, the best performance of electrolyte using DMC cosolvent was attributed to the most stable solid electrolyte interphase (SEI) and cathode electrolyte interphase (CEI) formed during the cycling. </p>

Lithium-ion batteries (LIB) represent a promising energy storage solution in the pursuit of electrification to combat climate change. In order for LIBs to be used across different industries, they have to be commercially viable. The viability for manufacturing LIBs at scale is increasing, with manufacturing costs decreasing 89% in the last ten years. However, the LIB manufacturing process is complex and can generate large amounts of scrap due to various non-conformities (NCs). Therefore, to further increase the ability to manufacture high-quality LIBs at scale, it is crucial to minimize the occurrence of NCs by understanding their root causes. This thesis examines the characteristics of one of the non-conformities occurring in the electrode coating process, namely the formation of craters on the coated surface of the anode electrode. The thesis was conducted at Northvolt Labs using a DMAIC approach to establish relationships between various process parameters and the formation of craters in two processes, coating, and its precursor process, slurry mixing. Utilizing the data models linear regression, CART regression, regularized linear regression, and a slurry experiment, process parameters and characteristics that affect crater formation were identified. Firstly, from the data models, it was distinguished that the speed of the supply pump used in transferring the slurry from the supply tank to the slot die, and the pressure in the filter pump, have the largest effect on crater formation. Further, the time that the slurry spends in storage, i.e. from a completely mixed slurry batch to it being applied in coating, affects crater formation. In this case, the longer the slurry is stored, the more craters are found. Another notable result is that refilling the coating supply tank induces crater formation. The mentioned results indicate that the various stages of slurry transfer undertaken before coating can result in advantageous conditions for craters to form. Moreover, it was discovered that changes in the loading level of the coated anode surface can indicate crater formation. The slurry experiment discovered that by contaminating the slurry with lubricant grease, NCs with similar characteristics to the crater could be generated. While not likely related to craters, this result provides valuable insights for slurry contamination. In addition to the data models and experiments, actions to facilitate future statistical analysis investigations are proposed. This thesis also proposes actions that can be undertaken to potentially mitigate the formation of craters. Suggested actions include methods to investigate the optimal storage time of the slurry before used in coating. Further, we recommend that the coating process should be monitored through the use of control charts on the loading level measurements of the coated surface. Consequently, large changes in loading level can be detected, entailing potential crater formation. We also propose adding lubricant grease as a potential risk in the PFMEA Northvolt uses for process risk evaluation. This recommendation is also complemented with suggested actions on how to handle the risks of lubricant grease contamination. / Användandet av litiumjonbatterier (LIB) som energilagring är en potentiell lösning för omställning till ett elektrifierat samhälle. Tillverkningsprocessen för LIBs är dock komplex och har en tendens att generera stora mängder kassationer på grund av olika typer av defekter. Denna studie ämnar att undersöka egenskaperna hos en av defekterna som kallas krater som kan förekomma i en av delprocesserna för litiumjonbatteritillverkning, elektrodbeläggning, där batteriets elektroder skapas genom att en blandning av aktiva material appliceras på en metallfolie. Kratern förekommer som en cirkulär form på den belagda ytan av anodelektroden. Studien genomfördes hos batteritillverkaren Northvolt Labs och använde en struktur enligt DMAIC cykeln. Syftet med studien var att fastställa samband mellan olika processparametrar och kraterformation för två olika processer, elektrodbeläggning och dess föregångare, framställning av den aktiva materialblandningen. Genom att använda datamodellerna linjär regression, CART-regression, en regulariserad linjär regression  samt ett experiment kunde processparametrar och egenskaper som påverkar kraterbildningen etableras. Resultaten från datamodellerna indikerar att varvtalet i pumpen som tillför ytbeläggningsmaskinen med den aktiva materialblandningen samt trycket i filterpumpen har den största effekten på kraterbildning. Vidare så påverkar tiden som den aktiva materialblandningen lagras innan den används i beläggningsprocessen. Resultaten indikerar att ju längre tid en aktiv materialblandning lagras, desto mer kraterbildning. Samtliga resultat som nämnts ovan anvisar att de olika stadier den aktiva materialblandningen överförs bland olika behållare och verktyg kan ge upphov till kraterbildning. Ytterligare resultat från datamodellerna indikerar att en minskad tjocklek av den belagda ytan, mätt med enheten g/cm2, kan påvisa när kratrar uppstår. Detta resultat kan härledas till att kratrarna orsakar en nedåtbuktning i den belagda ytan. Utifrån experimentet med den aktiva materialblandningen kunde det fastlås att kraterliknande defekter kunde genereras genom att kontaminera blandningen med smörjfett. Dessa defekter är sannolikt inte besläktade med kratern, men dess uppkomst ger värdefulla insikter hur kontaminering kan påverka kvaliteten på den belagda ytan. Utöver resultat från datamodellerna och experimentet så presenterar även denna studie förslag på hur framtida undersökningar av statistisk karaktär kan förbättras. Studien föreslår också konkreta åtanganden som kan genomföras med syfte att reducera kraterbildning. Detta inkluderar hur ett projekt med syfte att fastslå den optimala lagringstiden för den aktiva materialblandningen innan den används i ytbeläggningsprocessen kan utformas. Vidare rekommenderas att ytbeläggningsprocessen övervakas med hjälp av att upprätta styrdiagram för ytbeläggningens nivåförändringar. Följaktligen kan stora förändringar i ytbeläggningens jämnhet detekteras, vilket kan vara en indikator på kraterbildning. Studien rekommenderar också att tillägga kontaminering av smörjfett i den aktiva materialblandningen som en potentiell risk i Northvolts PFMEA. Denna rekommendation kompletteras även med förslag på åtanganden som kan tas för att hantera risken för kontaminering av smörjfett.