In this thesis, the diffusion of lithium was studied on boron-doped diamond (BDD) as a potential anode material in lithium ion batteries (LIB). The initial interaction between deposited lithium and BDD thin films was studied using X-ray Photoelectron Spectroscopy (XPS). Diffusion is directly linked to reactions between lithium and carbon atoms in the BDD-lithium interface. By measuring binding energies of core-electrons of carbon and lithium before and after deposition, these reactions can be analyzed. Scanning Electron Microscopy (SEM) was used to study the BDD surface and the behaviour of deposited lithium. Experiments show that a chemical interaction occurs between lithium and carbon atoms in the surfacelayers of the BDD. The diffusion of lithium is discussed from spectroscopic data and suggests that surface diffusion is occurring and no proof of bulk diffusion was found. The results do not exclude bulk diffusion in later states but it was not found in the initial interaction at the interface after depositing lithium. SEM images show that lithium clusters in the nanometer range are formed on the BDD surface. The results of this study give insights in the initial diffusion behaviour of lithium at the BDD interface and possible following events are discussed.

<p>The single particle model was extended to include electrode and particle volume expansion effects observed in high capacity alloying electrodes. The model was used to predict voltage profiles in sodium ion batteries with tin and tin-phosphide negative electrodes. It was seen that the profiles predicted by the modified model were significantly better than the classical model. A parametric study was done to understand the impact of properties such as particle radius, diffusivity, reaction rate etc on the performance of the electrode. The model was also modified for incorporating particles having a cylindrical morphology. For the same material properties, it was seen that cylindrical particles outperform spherical particles for large L/R values in the cylinder due to the diffusion limitations at low L/R ratios. A lattice spring-based degradation model was used to observe crack formation and creep relaxation within the particle. It was observed that the fraction of broken bonds increases with an increase in strain rate. At low strain rates, it was seen that there was a significant expansion in particle volumes due to creep deformation. This expansion helped release particle stresses subsequently reducing the amount of fracture.</p>

As an efficient means of energy storage, rechargeable batteries, especially the lithium-ion batteries (LIBs) have been a vital component in solving the upcoming energy crisis and environmental problems. Recently, the development of electric vehicle market puts new requirement on the next generation LIBs, including superior energy density, safety and cycling stability, etc. Compared with experimental investigation, Physics-based models provide a surrogate method to not only tackle the underlying physics of the complex battery system, but also optimize the design of battery systems. In this thesis, I will show how I use the physics-based continuum model and cooperate with some experimental methods to understand the lithium transport phenomena inside the multiscale battery electrode systems, based on which the models are then applied to guide the experimental optimization of battery electrode design and to quantitively understand the degradation of high-performance electrodes. The thesis is divided into three parts. First part (Chapter 2) presents a systematical model selection study on the multiscale LiNi₀.₃₃Mn₀.₃₃Co₀.₃₃O₂ (NMC₁₁₁) electrode. Discharge and voltage relaxation curves, interrogated with theory, are used to distinguish between lithium transport impedance that arise on the scale of the active crystal and on the scale of agglomerates (secondary particles) comprised of nanoscale crystals. Model-selection algorithms are applied to determine that the agglomerate scale transport is dominant in the NMC₁₁₁ electrode studied here. This study not only discovers the dominant length scale for lithium transport, but also provide a validated model (the agglomerate model) for later study. The second part (Chapter 3 & 4) talks about understanding & optimization of ion transport in porous electrodes. In Chapter 3, multi-scale physics-based models for different active material systems, which have been parameterized and validated with discharge experiments, are optimized by varying porosity and mass loading to achieve maximum volumetric energy density. The optimization results show that with a re-scaling of the current rate, the optimal results follow a general design rule that is captured in a convenient correlation. Chapter 4 extends the model to simulate the performance of advanced electrode architectures utilizing aligned channels, by quantifying the impact of aligned channel electrode structures on cell rate capability. Then the optimization algorithm in Chapter 3 is applied to these aligned-channel electrodes. The final part (Chapter 5) shows how I use the physics-based model to quantitatively analyze the battery degradation. The validated model is applied to cycling data to obtain parameter estimates indicative of degradation modes. It’s found that growth rates of interfacial impedance and active material loss are greater at 4.5 V, as might be expected. However, when charged to 4.5V, degradation rates are lower at a cycling C-rate of 1.0 h⁻¹ than at 0.5 h⁻¹. Once performance changes are quantified, we use further simulation to evaluate the contribution of individual degradation modes to fade of cell performance metric such as capacity, power density, and energy density.

Thesis (Ph.D. (Physics)) -- University of Limpopo, 2021 / Titanium dioxide is among the most abundant materials and it has many of interesting physical and chemical properties (i.e., low density, high thermal and mechanical strength, insensitivity to corrosion) that make it a compound of choice for electrodes materials in energy storage. There are, however, limitations on the theoretical side to using the main electronic structure theories such as Hartree-Fock (HF) or densityfunctional (DFT) especially for large periodic and molecular systems. The aim of the theses is to develop a new, widely transferable, self-consistent density functional tight binding SCC-DFTB data base of TiO2, which could be applied in energy storage anodes with a large number of atoms. The TiO2, LiTiO2 and NaTiO2 potentials were derived following the SCC-DFTB parameterization procedure; where the generalized gradient approximation (GGA) and local density approximation (LDA) exchange-correlation functional were employed yielding Slater-Koster DFTB parameters. The results of derived parameters were validated by being compared with those of the bulk rutile and brookite polymorphs. The structural lattice parameters and electronic properties, such as the bandgaps were well reproduced. Most mechanical properties were close to those in literature, except mainly for C33 which tended to be underestimated due to the choice of exchange-correlation functional. The variation of the bulk lattice parameter and volume with lithiation and sodiation were predicted and compared reasonably with those in literature. The newly derived DFTB parameters were further used to calculate bulk properties of the anatase, which is chemically more stable than other polymorphs. Generally, the accuracy of the lattice structural, electronic and mechanical properties of the bulk anantase were consistent with those of the rutile and brookite polymorphs. Furthermore, nanostructures consisting of a large number of atoms, which extend beyond the normal scope of the conventional DFT calculations, were modelled both structurally and electronically. Structural variations with lithiation was consistent with experimental and sodiation tends to enhance volume expansion than lithiation. Anatase TiO2 and LiTO2 nanotubes of various diameters were generated using NanoWrap builder within MedeA® software. Its outstanding resistance to expansion during lithium insertion and larger surface area make the TiO2 nanotube a promising candidate for rechargeable lithium ion batteries. The outcomes of this study will be beneficial to future development of TiO2 nanotube and other nanostructures. Lastly, our DFTB Slater-Koster potentials were applied to recently discovered trigonal bipyramid (TB), i.e. TiO2 (TB)-I and TiO2 (TB)-II polymorphs, which have enormous 1D channels that provide suitable pathways for mobile ion transport. All structural, electronic properties were consistent with those in literature and all elastic properties agreed excellently with those that were calculated using DFT methods. Finally, the bulk structures of the two polymorphs, were lithiated and sodiated versions and electronic and structural properties were studied, together with the lithiated versions of associated nanostructures consisting of a large number of atoms. Generally, the TiO2 (TB)-I structure was found to be mechanically, energetically more stable and ductile than TiO2 (TB)-II. Hence, it will be beneficial to use TiO2 (TB)-I as an anode material for sodium ion batteries (SIB), due to its unique ductility and larger 1D channels. / National Research Fund (NRF), Department of Science and Innovation (DSI), Material Modelling Centre

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Le contact entre l'électrode et l'électrolyte est primordial pour le bon fonctionnement d'une batterie Lithium-Ion. L'imprégnation de l'électrode positive par un électrolyte liquide a toujours été considérée comme totale, cependant les phénomènes ne sont pas exactement connus. Ainsi, ces travaux s'intéressent à l'influence de la composition de l'électrode positive (matière active et agent conducteur) sur cette imprégnation. Après une première étude des propriétés conductrices, électrochimiques et morphologiques d'électrodes présentant des formulations plus ou moins éloignées des formulations industrielles, une méthode utilisant l'équation de Washburn a été développée afin d'étudier l'imprégnation des pores modélisés par un ensemble de tubes capillaires. L'utilisation de l'hexadecane, considéré comme un liquide parfaitement mouillant, a permis de déterminer la taille effective des pores indépendamment de l'électrolyte, et celle-ci a pu être comparée à des résultats obtenus grâce à la méthode de thermoporosimétrie. Puis, les régimes de Washburn obtenus lors de la diffusion de l'électrolyte ont mis en évidence les cinétiques d'ascension. Par la suite, la méthode de Washburn a été utilisée afin de caractériser les propriétés d'imprégnation d'électrodes élaborées avec un nouveau liant et selon un procédé innovant s'affranchissant de l'utilisation de solvant. L'utilisation d'un additif permettant la création de porosité d'une part, et la réticulation du liant d'autre part permettent d'obtenir une imprégnation de l'électrolyte comparable à celle observée pour les électrodes fabriquées par voie solvant / The contact between the electrode and the electrolyte is essential for a Lithium-Ion battery functioning. The impregnation of a positive electrode by the electrolyte has always been considered as total; however the phenomena are not exactly known. Thus, in this work, the influence of the positive electrode composition (active material, conductive agent and binder) on the impregnation has been investigated. After a first study focusing on the conductive, electrochemical and morphological properties of the electrodes, with different types of formulation, a method using Washburn equation has been developed in order to study the impregnation of the electrode’s pores, which were modeled as capillary tubes. With the use of hexadecane, considered as a perfectly wetting liquid, the effective pore size has been determined and then compared to the results given by the thermoporosimetry method. Then, the kinetics of ascension have been identified with the Washburn regimes obtained with the diffusion of the electrolyte in the cathodes. Afterwards, Washburn method has been used in order to characterize the impregnation properties of electrodes elaborated with an innovative process without solvent. Thanks to the use of an additive allowing the creation of porosity in one hand and the reticulation of the binder in the other hand, an impregnation of these new electrode by the electrolyte has been considered as comparable to the one observed for the cathodes made with solvent

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第20707号 / 工博第4404号 / 新制||工||1684(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 阿部 竜, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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No description available.

Many sectors and industries are being pushed by policymakers and consumers towards an industrial transformation to become more sustainable. This in order to reduce the negative impact on the environment caused by the emissions of toxic substances and greenhouse gases, as well to promote more efficient use of resources. The transport sector and specifically the automotive industry is seen as one of the main actors within the climate debate due to their high environmental impact in terms of emissions. Therefore, authorities and customers are pushing automotive manufacturers to shift towards electric mobility. However, a rapid shift is not simple. The supply of raw materials needed to sustain the production of batteries does not meet the demand. In turn, causing shortages of some materials and heavily increasing their prices. This thesis addresses the supplier selection problem within a Swedish lithium-ion battery manufacturer with clients mainly in the automotive industry. The study has analyzed a set of relevant criteria to evaluate a supplier within the high-tech industry within a specific context. Furthermore, the study has determined whether differences exist between the importance of the criteria depending on the strategic profile of the material. The strategic profile depends on the profit impact and the supply risk of the material. In order to assess the importance weights of the criteria, the analytical hierarchy process (AHP) was used and interviews were conducted with purchasing experts in the industry. This study provides a new approach to the existing literature of supplier selection, by studying this process in an industry in which it has never been done and also by assessing the supplier selection by categorizing the materials by their strategic profile, an approach that has not been studied in literature until the moment. Results show that the importance of some of the supplier selection criteria vary widely between the strategic profile of the materials, while the importance of other criteria remain the same. In addition, the study has also determined that the importance of the criteria vary also within the supplier selection process, having different importance levels at different steps. Finally, the results show that some criteria of a certain criticality represent a go-no go gate in the selection process. The conclusions are that the supplier selection process within the battery industry cannot be regarded as a homogenous process and that supplier selection criteria vary with the strategic importance of the material. Thus, suppliers must be assessed with different criteria importance weights when using a tool such as the AHP to perform supplier selection. Additionally, the critical criteria for each material must be determined prior to use the tool. / Politiker och konsumenter ställer allt högre krav på industrin att genomföra åtgärder för att bli mer hållbara, exempelvis genom att minska utsläpp av giftiga ämnen och växthusgaser samt ett mer effektivt resursanvändande. Transportsektorn och bilindustrin är särskilt utpekade inom miljödebatten på grund av deras höga miljöpåverkan och stora mängder av utsläpp. Biltillverkarna drivs därför mot en industriell omvandling där förnybara bränslen ska ersätta fossila bränslen. Övergången till eldrivna fordon är en långsam och komplicerad process där flödeskedjan för effektiv tillverkning av bilbatterier fortfarande är under utveckling. Tillgången på vissa råmaterial som behövs för produktionen av batterier räcker inte för att mätta efterfrågan vilket drar upp prisnivån. Samtidigt etablerar sig många nya leverantörer av råmaterial vars varierande kvalitet och pålitlighet skapar ytterligare utmaningar hos batteritillverkarna. Studien behandlar urvalsprocessen vid inköp av material hos en svensk litium-jonbatteritillverkare med kunder främst inom bilindustrin. Urvalskriterier för att utvärdera leverantörer inom högteknologisk industri analyserats. Därtill har det utretts om skillnader existerar mellan kriteriernas betydelse beroende på råvarornas strategiska profil. Den strategiska profilen beräknas genom dess påverkan på produktens slutkostnad tillsammans med risken för avbrott i försörjningskedjan. Metoden Analytic Hierarchy Process (AHP) används för att bedöma dessa kriteriers betydelse. Därtill har intervjuer genomförts med branch-experter för att ge fördjupad insikt i kriteriernas betydelse. Studien ger två huvudsakliga bidrag till den akademiska litteraturen. Först och främst utvärderas urvalskriterierna, som identifierats i litteraturstudien, inom en industrisektor där de inte prövats tidigare. Urvalskriterierna för leverantörsval appliceras dessutom specifikt för råmaterial av olika strategisk profil för att studera i vilken utsträckning de skiljer sig åt. Även denna ansats är tidigare oprövad inom den akademiska litteraturen. Resultaten visar att vikten av vissa kriterier varierar i hög utsträckning mellan material av olika strategisk profil, medan andra kriterier är näst intill opåverkade. Studien har dessutom fastställt att betydelsen av vissa kriterier varierar mellan olika steg i urvalsprocessen. Somliga kriterier representerar en kritisk punkt i urvalsprocessen och utesluter de leverantörer som inte kan leverera upp till en miniminivå. Studiens slutsas är att urvalsprocessen vid val av leverantör inom batteribranschen inte kan ses som en homogen process då urvalskriterierna varierar med materialets strategiska betydelse. Råmaterialens strategiska profil måste alltså tas i beaktning vid användning av ett urvalsverktyg som AHP. De kritiska kriterier som leverantören måste leva upp till måste dessutom fastställas innan verktyget kan tas i bruk.