Silicon-based electrodes are the most promising negative electrodes for the next generation high capacity lithium ion batteries (LIB) as silicon provides a theoretical capacity of 3579 mAh g-1, more than 10 times higher than that of the state-of-the-art graphite negative electrodes. However, silicon-based electrodes suffer from poor cycle life due to large volume expansion and contraction during lithiation/delithiation. In order to improve the electrochemical performance a number of strategies have been employed, such as dispersion of silicon in active/inactive matrixes, devising of novel nanostructures, and various coatings for protection. Amongst these strategies, silicon-carbon coating based composites are one of the most promising because carbon coating is comparatively flexible, easy to obtain, and scalable with various industrial processes. Low cost and renewable lignin, which constitutes up to 30% dry mass of the organic carbon on earth, is widely available from paper and pulp mills which produce lignin in excess of 50 million tons annually worldwide. It is a natural bio-polymer with high carbon content and highly interconnected aromatic network existing as a structural adhesive found in plants. Generally burnt for energy on site, lignin is gradually finding its way into high value-added products such as precursor for carbon fibers, active material in negative electrodes, and raw material for supercapacitors. This dissertation focuses on high performance silicon-based negative electrodes utilizing lignin as the carbon precursor for conductive additive, binder, and carbon coating. To my knowledge this is one of the first works attempting to utilize and summarize the performance of lignin in silicon-based negative electrodes. The first part of the dissertation shows that silicon-lignin composites treated at 800 ºC displayed good capacity and cycling performance. The second part goes to generalize the effect of temperature on silicon-lignin composites and shows that a low temperature treatment granted an electrode with superior performance and cycling properties owing to the preservation of polymeric properties of lignin. The final part of the dissertation discusses the current research trends in SiOx based negative electrodes and extends lignin to that field. This dissertation will, hopefully, provide knowledge and insight for fellow researchers wishing to utilize lignin or other renewable resources in devising advanced battery electrodes.

Ce mémoire est consacré à l'étude de deux matériaux d'électrodes négatives pour batteries Li-ion : NiSb2 et TiSnSb. Ces matériaux de conversion possèdent des capacités presque deux fois supérieures à celle du graphite, actuellement utilisé, mais ils souffrent i) d'une faible cyclabilité causée par les variations volumiques caractéristiques de ce type d'électrode et ii) d'une grande perte de lithium irréversible lors de la 1ère insertion due à la réactivité de surface avec l'électrolyte. Les mécanismes réactionnels avec le lithium ont été étudiés en profondeur par diffraction des rayons X, spectrométrie Mössbauer (119Sn et 121Sb). Les études in situ et ex situ en spectroscopie d'absorption X ont permis d'identifier la formation de nanoparticules de métal de transition très réactives et dont l'instabilité est probablement à l'origine des phénomènes de relaxation observés dans l'électrode à l'état déchargé. L'amélioration des performances a été réalisée grâce à l'élaboration d'électrodes composites contenant des fibres de carbone et de la CMC. Cette formulation d'électrodes permet d'atteindre une cyclabilité de 250 cycles pour TiSnSb à régimes variables entre 4C et C. L'ajout de FEC dans l'électrolyte apparait également comme une solution pour augmenter la durée de vie des électrodes.L'interface électrode/électrolyte a été analysée par Résonance Magnétique Nucléaire, Spectroscopie Photoéletronique à rayonnement X et spectroscopie infrarouge. Li2CO3 est l'espèce majoritairement formée lors de la réduction de l'électrolyte en 1ère décharge (lié à la création de nouvelles surfaces lors de la réaction et à expansion volumique). Lors de la charge, une restructuration (ou fragmentation) de la SEI (couche de passivation) est probable à cause de la contraction de l'électrode. L'épaisseur de la couche de SEI à l'interface continue de croitre après 15 cycles. / The thesis is devoted to the study of two negative electrode materials for Li-ion batteries: NiSb2 and TiSnSb. These conversion type materials have high capacities greater than graphite electrode used in current devices. However, these compounds suffer from i) a low cyclability caused by volumetric variations which are characteristic of this type of electrode, and ii) a loss of lithium (irreversible process) during the 1st insertion due to the reduction of the liquid electrolyte on the surface of active material.The mechanisms have been studied by X-Ray Diffraction, Mössbauer Spectroscopy (119Sn and 121Sb). The in situ and ex situ X-ray Absorption Spectroscopy analysis have allowed identifying both the formation of highly reactive Ti and Ni nanoparticles and a relaxation effect in the discharged electrode at 0V. The improvement of performances is based on the composite electrodes formulation using carbon fibers as conductive additive and Carboxymethyl cellulose CMC as binder. A cyclability of 250 cycles at C and 4C rate is reached for TiSnSb electrodes. The addition of Fluoro Ethylene Carbonate (FEC) in the electrolyte is another way to increase the life span of electrodes.The electrode/electrolyte interface has been analyzed by Nuclear Magnetic Resonance, X-ray Photoelectron Spectroscopy and Infrared Spectroscopy. During the discharge, among the species produced from the reduction of electrolyte Li2CO3 is in the majority because new surfaces are created (volumetric expansion). On charge, a fragmentation of the Solid Electrolyte Interphase (SEI) deposited on the surface of the active material grains is observed. Moreover, first XPS investigations have shown that the SEI thickness continuously increases on cycling.

We consider the prediction algorithm and performance evaluation for prognostics and health management (PHM) problems, especially the prediction of remaining useful life (RUL) for the milling machine cutter and lithium ‐ ion battery. We modeled battery as a voltage source and internal resisters. By analyzing voltage change trend during discharge, we made the prediction of battery remain discharge time in one discharge cycle. By analyzing internal resistance change trend during multiple cycles, we were able to predict the battery remaining useful time during its life time. We showed that the battery rest profile is correlated with the RUL. Numerical results using the realistic battery aging data from NASA prognostics data repository yielded satisfactory performance for battery prognosis as measured by certain performance metrics. We built a battery test platform and simulated more usage pattern and verified the prediction algorithm. Prognostic performance metrics were used to compare different algorithms.

<p>The focus of this work is to develop and employ numerical methods that provide characterization of granular microstructures, dynamic fragmentation of brittle materials, and dynamic fracture of three-dimensional bodies.</p><p>We first propose the fabric tensor formalism to describe the structure and evolution of lithium-ion electrode microstructure during the calendaring process. Fabric tensors are directional measures of particulate assemblies based on inter-particle connectivity, relating to the structural and transport properties of the electrode. Applying this technique to X-ray computed tomography of cathode microstructure, we show that fabric tensors capture the evolution of the inter-particle contact distribution and are therefore good measures for the internal state of and electronic transport within the electrode. </p><p>We then shift focus to the development and analysis of fracture models within finite element simulations. A difficult problem to characterize in the realm of fracture modeling is that of fragmentation, wherein brittle materials subjected to a uniform tensile loading break apart into a large number of smaller pieces. We explore the effect of numerical precision in the results of dynamic fragmentation simulations using the cohesive element approach on a one-dimensional domain. By introducing random and non-random field variations, we discern that round-off error plays a significant role in establishing a mesh-convergent solution for uniform fragmentation problems. Further, by using differing magnitudes of randomized material properties and mesh discretizations, we find that employing randomness can improve convergence behavior and provide a computational savings.</p><p>The Thick Level-Set model is implemented to describe brittle media undergoing dynamic fragmentation as an alternative to the cohesive element approach. This non-local damage model features a level-set function that defines the extent and severity of degradation and uses a length scale to limit the damage gradient. In terms of energy dissipated by fracture and mean fragment size, we find that the proposed model reproduces the rate-dependent observations of analytical approaches, cohesive element simulations, and experimental studies.</p><p>Lastly, the Thick Level-Set model is implemented in three dimensions to describe the dynamic failure of brittle media, such as the active material particles in the battery cathode during manufacturing. The proposed model matches expected behavior from physical experiments, analytical approaches, and numerical models, and mesh convergence is established. We find that the use of an asymmetrical damage model to represent tensile damage is important to producing the expected results for brittle fracture problems.</p><p>The impact of this work is that designers of lithium-ion battery components can employ the numerical methods presented herein to analyze the evolving electrode microstructure during manufacturing, operational, and extraordinary loadings. This allows for enhanced designs and manufacturing methods that advance the state of battery technology. Further, these numerical tools have applicability in a broad range of fields, from geotechnical analysis to ice-sheet modeling to armor design to hydraulic fracturing.</p> / Dissertation

Degradation behavior of commercial lithium-ion pouch cells containing LiCoO2 cathode and graphite anode was investigated for a cycling under continuous overcharge condition. This condition is frequently experienced in electric vehicles in an event of Battery Management System (BMS) failure. Failure of BMS results in an unbalanced module further resulting in overcharging or overdischarging the cells. Commercial cells with 5Ah capacity were continuously cycled at different upper cutoff voltages and 1C-rate to develop a better understanding of the overcharge process. The results show that as the upper cutoff voltage is extended, the cell gains a higher initial capacity. However, the cycle life of the cell diminishes significantly. The extent of overcharge was found to be an important parameter not only for the electrochemical performance but also for cell integrity. Cells overcharged beyond 4.5 V had a significant volume increase and a rapid increase in the capacity fade. The cell starts to swell at this stage and a considerable increase in the temperature and internal resistance of the cells is observed. Thermal imaging of the cell revealed non-uniform temperature distribution and localized degradation sites were identified. Evidence of lithium plating and electrolyte deposits on anode was observed in cells charged beyond 4.4 V, with SEM-EDS verifying their presence. A comparative study of various State of Health (SoH) estimation parameters is presented and the proposed parameter Φ_R based on internal resistance measurement is found to be a good indicator of aggravated degradation in cells.<br>

Background:          The growing number of electric vehicles gives rise to a whole new reverse supply chain. Once the electric vehicle batteries reach their end-of-life, societal and governmental pressure forces automotive manufacturers to set up a network for disposing the hazardous batteries. Although, the volumes of returned batteries remain low, volumes will increase in upcoming years. Current networks and processes related to the return flow of electric vehicle batteries are not well established, nor well defined. Thus, creating an urgency to develop efficient collection networks.   Purpose:                  The purpose of this study is to investigate how reverse logistics networks are currently set up and to provide an overview of how the different actors and processes are connected. In addition, this thesis aims to identify challenges encountered by logistics providers and recyclers. By doing so, we hope to contribute to the research gap of which factors that constitutes a bottleneck for further development of the reverse logistics chain of electric vehicle batteries.   Method:                  The thesis conducts an interview study and is qualitative in nature. Semi-structured interviews generated empirical data, which was analysed through cross-case analysis incorporating a thematic analysis. Through this analysis we were able to achieve new theoretical understandings in connection to institutional theory.   Conclusion:             Through empirical findings a detailed framework of the reverse logistics chain of EVBs is portrayed. Furthermore, different challenges span over the processes illustrated in the framework. This presents an overview which is not found in current literature and extends current research on this topic.

Thesis advisor: Udayan Mohanty / Rechargeable batteries, especially lithium ion batteries, have greatly transformed mobile electronic devices nowadays. Due to the ever-depletion of fossil fuel and the need to reduce CO2 emissions, the development of batteries needs to extend the success in small electronic devices to other fields such as electric vehicles and large-scale renewable energy storage. Li-ion batteries, however, even when fully developed, may not meet the requirements for future electric vehicles and grid-scale energy storage due to the inherent limitations related with intercalation chemistry. As such, alternative battery systems should be developed in order to meet these important future applications. This dissertation presents our successes in improving Li-O2 battery performance for electric vehicle application and integrating a redox flow battery into a photoelectrochemical cell for direct solar energy storage application. Li-O2 batteries have attracted much attention in recent years for electric vehicle application since it offers much higher gravimetric energy density than Li-ion ones. However, the development of this technology has been greatly hindered by the poor cycling performance. The key reason is the instability of carbon cathode under operation conditions. Our strategy is to protect the carbon cathode from reactive intermediates by a thin uniform layer grown by atomic layer depostion. The protected electrode significantly minimized parasitic reactions and enhanced cycling performance. Furthermore, the well-defined pore structures in our carbon electrode also enabled the fundamental studies of cathode reactions. Redox flow batteries (RFB), on the other hand, are well-suited for large-scale stationary energy storage in general, and for intermittent, renewable energy storage in particular. The efficient capture, storage and dispatch of renewable solar energy are major challenges to expand solar energy utilization. Solar rechargeable redox flow batteries (SRFBs) offer a highly promising solution by directly converting and storing solar energy in a RFB with the integration of a photoelectrochemical cell. One major challenge in this field is the low cell open-circuit potential, mainly due to the insufficient photovoltages of the photoelectrode systems. By combining two highly efficient photoelectrodes, Ta3N5 and Si (coated with GaN), we show that a high-voltage SRFB could be unassistedly photocharged and discharged with a high solar-to-chemical efficiency. / Thesis (PhD) — Boston College, 2018. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

Thesis advisor: Dunwei Wang / In this work, we present our findings regarding the low-temperature, solid-state conversion of Cu₂S nanowires to Cu₂S/Cu₅FeS₄ rod-in-tube structures, Cu₂S/ZnS segmented nanowires, and a full conversion of Cu₂S nanowires to ZnS nanowires. These conversion reactions occur at temperatures as low as 105 degrees Celsius, a much lower temperature than those required for reported solid-state reactions. The key feature of the Cu₂S nanowires that enables such low conversion temperatures is the high ionic diffusivity of the Cu⁺ within a stable S sublattice. The second portion of this work will focus on the oxide-stabilization and utilization of TiSi₂ nanonets as a lithium-ion battery anode. This nanostructure, first synthesized in our lab, was previously demonstrated to possess a lithium storage capacity when cycled against a metallic Li electrode. However, with subsequent lithiation and delithiation cycles, the TiSi₂ nanonet structure was found to be unstable. By allowing a thin oxide layer to form on the surface of the nanonet, we were able to improve the capacity retention of the nanonets in a lithium-ion half-cell; 89.8% of the capacity of the oxide-coated TiSi₂ was retained after 300 cycles compared to 62.3% of the capacity of as-synthesized TiSi₂ nanonets after 300 cycles. The layered structure of C49 TiSi₂ exhibited in the nanonets allows for a specific capacity greater than 700 mAh g(-1), and the high electrical conductivity of the material in conjunction with the layered structure confer the ability to cycle the anode at rates of up to 6C, i.e., 10 minute charge and discharge cycles, while still maintaining more than 75% of the capacity at 1C, i.e., 1 hour charge and discharge cycles. / Thesis (MS) — Boston College, 2013. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Chemistry.

L’électrode négative des batteries lithium-ion est communément en graphite. Bien qu’ayant une capacité spécifique intéressante, le vieillissement, la cinétique d’intercalation et le transport du lithium à la fois dans le matériau actif et les porosités de l’électrode limitent son fonctionnement optimal et homogène. Dans ce travail de thèse, les mécanismes à l’origine de ces limites sont explicités grâce à un modèle multi-physique de type électrode poreuse.Une étude de sensibilité des paramètres du modèle a montré l’importance des paramètres liés à la cinétique d’intercalation et au transport du lithium en phase solide et liquide. L’exploitation du modèle, validé expérimentalement, montre que, lors du fonctionnement de l’électrode, les apparences d’hétérogénéité de lithiation sont corrélées à la forme particulière du potentiel d’équilibre du graphite vis-à-vis de son taux de lithiation. La modélisation de la distribution de taille des particules, amplifie grandement ces hétérogénéités et dégrade fortement la performance globale de l’électrode. En première approche, une mesure operando de la distribution des états de lithiation confirme l’aspect hétérogène du fonctionnement de l’électrode.Les données des performances en cyclages et en calendaire de cellules graphite-NMC ont permis de construire différents modèles de vieillissement de l’électrode. La croissance de la couche de passivation (SEI) peut expliquer à elle seule la perte de lithium cyclable. Les hétérogénéités de SEI obtenues par le modèle sont négligeables en l’état. Les gains de capacités et les pertes brutales sont expliqués respectivement par des mécanismes de dissolution de SEI et de formation de lithium-plating. / Negative electrodes of lithium-ion batteries are mainly based on graphite, because of their good electrochemical properties. Unfortunately, intercalation kinetics, aging phenomena and lithium transport through active material and electrode porosity decay the optimal and homogeneous operations of this electrode. Origins of these limits are investigated in this work thanks to a porous electrode model.A sensitivity study indicates that preponderant model parameters are related to the kinetics and lithium transport in solid and liquid phases. The model is experimentally validated at a cell scale and predicts the appearances of lithium heterogeneities during the graphite lithiation. They are correlated to the staged shape of the graphite equilibrium potential. Modeling additional inhomogeneity sources, especially particle distribution, amplifies these heterogeneities and decrease drastically cell performance. In a first approach, an operando measure of the local lithiation state confirms this heterogeneity aspect during operations.In a second part, data of cycled and calendar aged graphite-NMC cell validates different aging models. The growth of the passive layer on the graphite surface (SEI) explains the cyclable lithium loss on its own. SEI heterogeneities are negligible in the porous model as opposition to experimental finding. Capacity recoveries and sudden loss are explained respectively via a SEI dissolution mechanism and lithium-plating correlated to the degradation of the electrode transport properties.

Silicon (in the form of lithium silicides) has almost ten times the theoretical charge storage capacity of graphite, the anode material used in most commercially-available lithium-ion batteries. Replacing graphite with silicon therefore promises a substantial improvement over the state-of-the-art in electrochemical energy storage. However, it has proved difficult to realise this high theoretical capacity in a practical electrochemical cell and maintain it over repeated charge-discharge cycles. This dissertation presents experimental work probing the changes in local structure occurring during the electrochemical reactions of lithium with silicon, using neutron total scattering and nuclear magnetic resonance, together with novel processing methodologies for analysing the resulting data, in the hope of suggesting ways of improving the performance of silicon-based lithium-ion batteries. Neutron total scattering patterns were obtained from silicon-based anode materials extracted from cells at various states of charge. These samples were composed of a heterogeneous mixture of amorphous, crystalline and disordered crystalline materials. Reverse Monte Carlo is a technique for obtaining structural information from experimental data (particularly total scattering patterns) from amorphous and disordered crystalline materials. However, previously existing Reverse Monte Carlo software could only handle homogeneous materials. Therefore, the RMCprofile software package was extended to handle data from heterogeneous samples. The improved RMCprofile was applied to the aforementioned total scattering patterns, but the much stronger scattering from the other components (themselves not well-characterised) swamped that from the lithium silicide. Future work should attempt to reduce the scattering from the inactive components, particularly the hard-to-model incoherent scattering. NMR data were acquired in situ from silicon-nanowire-based lithium-ion batteries during repeated charge-discharge cycles, achieving much better electrochemical performance than had been seen in previous in situ experiments with silicon. Owing to the large quantities of data obtained, an automated, model-free dimensionality reduction technique was needed. The NMR data were processed using principal component analysis and a variant of non-negative matrix factorisation. With both of these methods, one of the components was found to be associated with high voltages vs. ${Li \vert{} Li^{+}}$ (i.e. a fully discharged anode). This region has seen very little interest by comparison with the low voltage (high levels of lithiation) region of the charge-discharge cycle, so this discovery suggests a new avenue for future research.