<p> Energy storage has received much attention due to the increasing use of energy, especially renewable energy. Lithium-ion batteries have great characteristics for electrical energy storage. Higher specific energy density, cycle life, cell voltage, shorter charge times gives lithium-ion batteries favorable energy storage characteristics over other battery chemistries. Although lithium-ion batteries are increasing in use for electrical energy storage, their safety still poses an engineering problem. When lithium-ion batteries are abused, they can enter thermal runaway. This event is dangerous as it can eject hot gases and shrapnel. Previous studies focused on different aspects of thermal runaway, for example, heat generation from chemical reactions, propagation to other cells, and the physics of gas venting. One phenomenon that has not received much attention is the evaporation of the electrolyte out of a failed lithium-ion battery. Understanding the effect of electrolyte evaporation is key to having a more complete understanding of thermal runaway. In this thesis, the physics of electrolyte evaporation is studied with the purpose of developing more accurate thermal abuse models. An evaporation model was developed, based on porous drying theory and a 1-D liquid diffusion process. Experiments were conducted to identify the liquid diffusion coefficient which governs the rate of electrolyte transport within the porous separator within the battery. The 1-D liquid diffusion model was then implemented into an existing thermal abuse model and exercised for a typical oven test scenario. Results showed that the physics-based evaporation model resulted in excellent agreement with experimental data at different oven temperatures.</p>

In this thesis, a physics-based single particle modeling is presented to analyze a proposed direct coupled hybrid energy storage modules using lithium-ion battery and ultracapacitor. Firstly, a state of the art for the energy storage system in the electrified vehicles are summarized. Several energy storage elements including lead-acid battery, nickel-metal hydride battery, lithium-ion battery, ultracapacitor, and lithium-ion capacitor are reviewed. Requirements of the energy storage systems in electric, hybrid electric, and plug-in hybrid electric vehicles are generalized. Typical hybrid energy storage system topologies are also reviewed. Moreover, these energy storage elements and hybrid energy storage system topologies are compared to the requirements of the energy storage systems in terms of specific power and specific energy. Secondly, the performance of different battery balancing topologies, including line shunting, ring shunting, synchronous flyback, multi-winding, and dissipative shunting are analyzed based on a linear programming methodology. As a traction battery in an electric or plug-in electric vehicle, high voltage lithium-ion packs are typically configured in a modular fashion, therefore, the analysis considers the balancing topologies at module level and cell level and focuses on minimum balancing time, minimum plug-in charge time, minimum energy loss, and component counts of every balancing topology for the entire battery pack. Thirdly, different modeling techniques for the lithium-ion battery and ultracapacitor are presented. One of the main contributions of this thesis is the development of a physics-based single particle modeling embedded with a solid-electrolyte interface growth model for a lithium-ion battery in battery management system. This development considers the numerical solution of diffusion equation, cell level quantities, parametrization method, effects of number of shells in a spherical particle, SOC-SOH estimation algorithms, and aging effects. The accuracy of the modeling is validated by experimental results of a Panasonic NCR18650A lithium-ion battery cell. Fourthly, the physics-based modeling is applied to analyze the performance of a proposed direct coupled hybrid energy storage module topology based on the Panasonic NCR18650A lithium-ion battery and Maxwell BCAP0350 ultracapacitor. There are many ways to directly connect battery cells and ultracapacitor cells in a module which would influence the performance of the module. The results show that a module has 9 cells in a battery string and 14 cells in an ultracapacitor string can obtain the highest power capability and utilize the most of the energy in an ultracapacitor. More ultracapacitor strings connected in parallel would increase the power density but reduce the energy density. Moreover, the simulation and experimental results indicate that the direct coupled hybrid modules can extend the operating range and slow the capacity fade of lithium-ion battery. An SOC-SOH estimation algorithm for the hybrid module is also developed based on the physics-based modeling. Finally, a pack design methodology is proposed to meet U.S. Advanced Battery Consortium LLC PHEV-40, power-assist, and 48V HEV performance targets for the battery packs or the proposed direct coupled topologies. In order to explore replacement tradeoffs between the battery and ultracapacitor, a case study of the direct coupled topologies is presented. From the case study, ultracapacitors enhance the power capability for short term pulse power and marginally reduce the cost of an entire energy storage system. Moreover, the hybrid module topologies can keep a relatively long all-electric range when the batteries degrade. / Dissertation / Doctor of Philosophy (PhD)

Lack of technical cleanliness and particle contaminations in Lithium-ion battery manufacturing affect the performance of batteries which are a risk for the safety and quality of the product. Therefore, part of the manufacturing process occurs inside the Clean and Dry room area to maintain technical cleanliness. This paper aims to provide a framework to control particle contamination inside the Clean and Dry room and strengthen the product's quality and safety. A literature study was conducted, which was completed by a field study at Northvolt Labs in Västerås to achieve the study's aims. The study contributes to existing theories by providing a framework to find root causes of particle contamination in the manufacturing process based on the existing literature and standards. The Six Sigma problem-solving methodology DMAIC was implemented to conduct the field study. A risk assessment was conducted to find the possible threats toward technical cleanliness in the cell assembly process. The risk sources were identified by implementing measurement methods from relevant standards. The results indicate a high risk for technical cleanliness are coming from the decontamination method, material, machines, and environment. Furthermore, several recommendations were given that are expected to decrease the amount of nonconformity in the process. / Brist på teknisk renhet och partikelföroreningar vid tillverkning av litiumjonbatterier påverkar dess prestanda och utgör en risk för produktens säkerhet och kvalitet. Därför sker en del av tillverkningsprocessen i ett Clean &amp; Dry rum för att upprätthålla teknisk renhet. Denna uppsats syftar till att ge ett ramverk för att kontrollera partikelföroreningar och därmed stärka produktens kvalitet och säkerhet. För att uppnå syftet genomfördes först en litteraturstudie vilket vidare kompletterades med en fältstudie vid Northvolt Labs i Västerås. Studien bidrar till befintliga teorier genom att tillhandahålla ett ramverk för att hitta och åtgärda rotorsaker till partikelkontaminering i tillverkningsprocessen baserat på befintlig litteratur och standarder. Sex Sigma problemlösningsmetoden DMAIC implementerades för att genomföra fältstudien. En riskbedömning genomfördes för att hitta riskfyllda aktiviteter i processen. Vidare implementerades mätmetoder från relevanta standarder för att mäta kontamineringsnivån. Resultaten indikerar stor risk för tekniskrenhet från saneringsmetoder, material, maskiner och miljön. Vidare rekommenderas flera åtgärder för att underhålla tekniskrenhet vilka förväntas minska avvikelser i processen.

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To reach the Swedish goal of reaching a completely fossil-free electricity sector by the year 2040, there is a need for an increased rate of installed renewable electricity sources. Companies have the opportunity to work towards this goal by investing in solar power technologies, which results in a lowered electricity bill, and an additional revenue when electricity is sold to the grid. As a result, the investment usually pays back within a reasonable timeframe. GEHAB is a company located that is located in Alvesta, Sweden, and they are interested in investing in rooftop solar power. This thesis investigates the potential and effects of such an investment at the company through energy simulations. This is done through four different scenarios, which aim at finding the largest possible installation, the most cost-optimal installation, according to the Levelized Cost Of Energy (LCOE), the impact of an added battery installation and finding the current issues with becoming a net-zero consumer of electricity. Finally, a sensitivity analysis was made to investigate how different factors impacted the LCOE. The results showed that the most cost-optimal size for the company to invest in was a 215 kWp installation, which is smaller than the maximum possible size of 335 kWp that can be installed on the rooftop. Such an installation would have an LCOE of -366 SEK/MWh when the avoided costs are included. The discounted payback time of that investment was 11.3 years. The involvement of batteries showed that they would lead to a higher LCOE and for the largest possible solar installation size, including a battery, means that it would not pay back within the lifetime of the PVs. Finally, the net-zero electricity consumption scenario found that currently, the largest issue to reach this scenario is that there is a regulation that limits solar installations to 500 kWp to avoid an energy tax.

An investigation of electrochemical storage device materials has been undertaken in four parts. The bulk and interfacial resistance of Na+ beta-alumina tubes were separated using a galvanostatic charge-discharge method. Sodium silicide was characterized to better understand its synthesis. BiMn2O5 was produced using a sol-gel method and tested for pseudocapacity. Different lithium ion anode and cathode materials were deposited using a new electrophoretic deposition method. A novel galvanostatic charge-discharge method was developed for the determination of bulk and interface resistance in Na+ beta-alumina solid electrolytes [BASE]. Dense and duplex BASE tubes were tested by varying the exposed surface area. The results of dense BASE tube pairs were used to determine the bulk and interfacial resistance components, while duplex BASE tubes were tested to determine the reduction in interfacial resistance. It was found that duplex tubes had reduced the interfacial resistance by 75%, when compared to a uniformly dense electrolyte. Sodium silicide was characterized using various methods to better understand the phase and the Na-Si phase diagram. EMF experiments using Na+ BASE tubes was used to determine the activity in the silicon rich region of the phase diagram, which showed a sodium activity of 0.5 at 550°C. TGA/DSC was used to determine phase transformation temperatures, as well as the heat of formation for NaSi, which was recorded to be below 1 kJ mol-1. A sol-gel precipitation method was used to produce fine BiMn2O5 powders used for supercapacitors. The powders resulting from a consistent method were tested for pseudocapacitance using bulk and thin film electrodes. Bulk electrodes had a gravimetric capacitance of 10 F g-1, while thin film electrodes only reached 2.6 F g-1. Lithium ion battery anode (Li4Ti5O12) and cathode (LiFePO4, LiMn2O4, LiMn1.5Ni0.5O4) materials were electrophoretically deposited with the assistance of PAZO-Na and CMC-Na. Cathodes were successfully deposited on aluminium substrates, and were tested in the potential window 2 – 4.3 V. The LiFePO4 cathodes showed capacity of 146.7 mAh g-1 at C/10, while showing capacity retention of 103% after 50 cycles. / Thesis / Doctor of Philosophy (PhD) / The goal of this work is to examine materials used in different types of electrochemical storage devices. The modification of resistive properties of β-alumina electrolytes are examined for use in high temperature sodium batteries. Electrophoretic deposition methods are used to rapidly make thin electrodes for lithium ion batteries and supercapacitors. The stoichiometric compound NaSi, a potentially safer and greener method of producing hydrogen gas, is characterized for a better understanding of its properties, and therefore production.

Lithium-ion based battery energy storage system has become one of the most popular forms of energy storage system for its high charge and discharge efficiency and high energy density. This dissertation proposes a high-efficiency grid-tie lithium-ion battery based energy storage system, which consists of a LiFePO4 battery based energy storage and associated battery management system (BMS), a high-efficiency bidirectional ac-dc converter and the central control unit which controls the operation mode and grid interface of the energy storage system. The BMS estimates the state of charge (SOC) and state of health (SOH) of each battery cell in the pack and applies active charge equalization to balance the charge of all the cells in the pack. The bidirectional ac-dc converter works as the interface between the battery pack and the ac grid, which needs to meet the requirements of bidirectional power flow capability and to ensure high power factor and low THD as well as to regulate the dc side power regulation. A highly efficient dual-buck converter based bidirectional ac-dc converter is proposed. The implemented converter efficiency peaks at 97.8% at 50-kHz switching frequency for both rectifier and inverter modes. To better utilize the dc bus voltage and eliminate the two dc bus bulk capacitors in the conventional dual-buck converter, a novel bidirectional ac-dc converter is proposed by replacing the capacitor leg of the dual-buck converter based single-phase bidirectional ac-dc converter with a half-bridge switch leg. Based on the single-phase bidirectional ac-dc converter topology, three novel three-phase bidirectional ac-dc converter topologies are proposed. In order to control the bidirectional power flow and at the same time stabilize the system in mode transition, an admittance compensator along with a quasi-proportional-resonant (QPR) controller is adopted to allow smooth startup and elimination of the steady-state error over the entire load range. The proposed QPR controller is designed and implemented with a digital controller. The entire system has been simulated in both PSIM and Simulink and verified with hardware experiments. Small transient currents are observed with the power transferred from rectifier mode to inverter mode at peak current point and also from inverter mode to rectifier mode at peak current point. The designed BMS monitors and reports all battery cells parameters in the pack and estimates the SOC of each battery cell by using the Coulomb counting plus an accurate open-circuit voltage model. The SOC information is then used to control the isolated bidirectional dc-dc converter based active cell balancing circuits to mitigate the mismatch among the series connected cells. Using the proposed SOC balancing technique, the entire battery storage system has demonstrated more capacity than the system without SOC balancing. / Ph. D.

<p dir="ltr">Applications of Lithium-ion batteries (LIBs) are so widely spread from transportation like electric vehicles to portable storage devices. This is mainly due to their lighter weight and smaller size with higher energy density when compared to Lead-acid, Nickel Cadmium (Ni-Cd), and other batteries. One of the applications of LIB includes electric propulsion in-air like quadcopters. These electrically-propelled vehicles have diverse applications including risky jobs like wildlife management, search and rescue, and jobs that can be automated such as delivery of smaller packages, urban planning, and so on. These electrically-propelled vehicles produce heat around the LIB which leads to thermal abuse of the battery. Also, there are often cases where LIB undergoes different abuse conditions in-air when operating these vehicles. Present battery BMSs are highly accurate but require edge and cloud with a deep learning model to safely operate quadcopters in the air. In the work, we present a BMS capable of edge-cloud data transfer with a deep-learning model to predict the RUL of the battery. Benchmark differences between data collected on-ground and in-air are presented for comparison. It turns out that the temperature collected in the air is less than the temperature on the ground when different current profiles are experimented on different batteries used in quadcopters. This study helps in the improvement of BMS with edge-cloud and deep-learning models and helps in understanding the behavior of battery in-air.</p>

This dissertation addresses the synthesis mechanism of mesoporous titania thin films with 2D Hexagonal Close Packed (HCP) cylindrical nanopores by an evaporation-induced self-assembly (EISA) method with Pluronic surfactants P123 and F127 as structure directing agents, and their applications in photovoltaics and lithium ion batteries. To provide orthogonal alignment of the pores, surface modification of substrates with crosslinked surfactant has been used to provide a chemically neutral surface. GISAXS studies show not only that aging at 4°C facilitates ordered mesostructure development, but also that aging at this temperature helps to provide orthogonal orientation of the cylindrical micelles which assemble into an ordered mesophase directly by a disorder-order transition. These films provide pores with 8-9 nm diameter, which is precisely the structure expected to provide short carrier diffusion length and high hole conductivity required for efficient bulk heterojunction solar cells. In addition, anatase titania is a n-type semiconductor with a band gap of +3.2 eV. Therefore, titania readily absorbs UV light with a wavelength below 387 nm. Because of this, these titania films can be used as window layers with a p-type semiconductor incorporated into the pores and at the top surface of the device to synthesize a photovoltaic cell. The pores provide opportunities to increase the surface area for contact between the two semiconductors, to align a p-type semiconductor at the junction, and to induce quantum confinement effects. These titania films with hexagonal phase are infiltrated with a hole conducting polymer, poly(3-hexylthiophene) (P3HT), in order to create a p-n junctions for organic-inorganic hybrid solar cells, by spin coating followed by thermal annealing. This assembly is hypothesized to give better photovoltaic performance compared to disordered or bicontinuous cubic nanopore arrangements; confinement in cylindrical nanopores is expected to provide isolated, regioregular “wires” of conjugated polymers with tunable optoelectronic properties, such as improved hole conductivity over that in bicontinuous cubic structure. The kinetics of infiltration into the pores show that maximum infiltration occurs within less than one hour in these films, and give materials with improved photovoltaic performance relative to planar TiO2/P3HT assemblies. These oriented mesoporous titania films are also used to develop an inorganic solar cell by depositing CdTe at the top using the Close Spaced Sublimation (CSS) technique. A power conversion efficiency of 5.53% is measured for heterostructures built using mesoporous titania films, which is significantly enhanced relative to planar TiO2/CdTe devices and prior reports in the literature. These mesoporous titania films have a great potential in inorganic solar cell development and can potentially replace CdS window layers which are conventionally used in inorganic CdS-CdTe solar cells. The last part of the dissertation addresses layer-by-layer synthesis to increase the thickness of mesoporous titania films with vertically oriented 2D-HCP nanopores, and their use in lithium ion batteries as negative electrodes because of advantages such as good cycling stability, small volume expansion (~3%) during intercalation/extraction and high discharge voltage plateau. The high surface area and small wall thickness of these titania films provide excellent lithium ion insertion and reduced Li-ion diffusion length, resulting in stable capacities as high as 200-250 mAh/g over 200 cycles.

Les nouvelles technologies sont de plus en plus demandeuses de sources de forte densité d’énergie respectueuses de l’environnement. Les accumulateurs lithium-ion semblent être la meilleure solution pour les applications mobiles et pour le domaine de l’automobile. Afin de répondre aux besoins en énergie de plus en plus importants, de nouveaux matériaux d’électrode négative sont nécessaires pour remplacer le carbone qui a désormais atteint son stade de maturité. En particulier, les composites silicium/carbone (Si/C) semblent être prometteurs pour augmenter la densité d’énergie des accumulateurs mais présentent de faibles rétentions de capacité au cours du cyclage. L’amélioration de la cyclabilité des composites Si/C fait l’objet de ce travail de thèse. La synthèse des composites par atomisation avec de l’alcool polyvinylique comme précurseur carboné suivie d’une pyrolyse est présentée. Les performances électrochimiques des matériaux résultants sont comparées à celles obtenues par d’autres composites, élaborés par lyophilisation et par broyage. Les propriétés intrinsèques des composites ont été modifiées par deux voies différentes afin d’améliorer leur cyclabilité. Dans un premiers temps, les effets de la réticulation de l’alcool polyvinylique ont été étudiés, puis ceux liés à l’ajout d’un catalyseur favorisant la graphitisation du carbone. La cyclabilité des composites Si/C peut également être améliorée en modifiant la nature du liant utilisé lors de la préparation des électrodes. L’intérêt bénéfique de l’emploi de l’acide polyacrylique en remplacement du fluorure de polyvinylidène couramment utilisé dans des électrodes à base de composites Si/C est démontré. / New technologies require more and more environment friendly sources of high energy density. Lithium-ion batteries seem to be the best solution for mobile and automotive applications. In order to meet the future energy requirements, new negative electrode materials are needed to replace carbon which has now reached a mature stage. Especially, silicon/carbon composites (Si/C) appear to be promising candidates to increase the energy density of batteries, but they still present poor capacity retention upon cycling. The improvement of Si/C composites cyclability is the subject of this thesis. The synthesis of Si/C composites by spray drying with polyvinyl alcohol as carbon precursor, followed by pyrolysis, is presented. The electrochemical performances are compared with those obtained for other composites, prepared by freeze drying and ball-milling. The intrinsic properties of the composites were modified in two different ways to improve their cyclability. First, we studied the effects of polyvinyl alcohol crosslinking, and then those related to the graphitization of carbon contained in these composites. The cyclability of Si/C composites can also be improved by changing the nature of the binder used during the electrodes preparation. The beneficial interest of using polyacrylic acid in replacement of polyvinylidene fluoride binder commonly used in Si/C based electrodes is shown.