This thesis suggests a new approach to extend the lifetime of Lithium-ion batteries for a Home Energy Storage System equipped with a renewable energy source. The new configuration improves the lifetime of the energy storage device by using the pulsed charge-discharge method. The batteries in this system can be charged either using solar panels when solar energy is available or by the grid power during off-peak hours when the electricity cost is at its lowest rate. In the new configuration, the battery bank is split into two equal sections to employ pulsed charge-discharge method. Interrupting the charge or discharge current provides a relaxation time for the lithium ions to diffuse gradually into the electrodes material of Lithium-ion batteries, this reduces the damage in the microstructure of the electrodes and thus it helps to prolong the battery lifetime. The spilt bank strategy improves the longevity of Lithium-ion batteries while maximizing the solar energy utilization. This strategy leads to reduce the reliance on the grid power which decreases the consumer’s total energy cost as well. To show the usefulness of the new approach, different modes of operation are discussed in details along with simulation results. An experimental setup is also developed to evaluate the effectiveness of the new approach in extending the Lifetime of Lithium-ion batteries. / Thesis / Master of Applied Science (MASc)

The subject of this thesis is the application of magnetic resonance methods to the characterization and quantification of lithium-ion transport in a wide range of lithium-ion battery electrolyte materials relevant to the electromobility and energy storage sectors. In particular, field-gradient magnetic resonance techniques, in the form of PFG-NMR diffusivity measurements of both liquid- and solid-state electrolytes and in situ MRI of electrochemical cells, comprise the core means by which these characterizations were performed. PFG-NMR and ionic conductivity studies of a range of liquid-state electrolyte mixtures were performed, as a function of temperature, to assess how key mass and charge transport properties reflect differences in composition. In situ MRI was used to study the effect of temperature on steady-state concentration gradient formation in polarized liquid electrolytes, with the results quantitatively compared to model predictions. This approach was then extended, using a combination of MRI and spatially-resolved PFG-NMR, to study the interlinked effects of temperature and current density on concentration gradient formation, and to attempt a comprehensive characterization of the ion transport parameters with spatial resolution. Finally, PFG-NMR and MAS-NMR were applied in a solid-state electrolyte context to investigate compositional effects on ion transport in the argyrodite family of lithium-sulphide ion conductors, and the influence of macroscopic sample format (glass, crystalline powder, compressed crystalline pellet) on micro-scale ion transport in a thio-LISICON ion conductor. Taken together, the studies demonstrate the effectiveness of magnetic resonance methods for the robust elucidation of the means by which material properties impact ion transport in technologically-relevant lithium-ion electrolyte systems. / Dissertation / Doctor of Science (PhD) / Lithium-ion batteries are a critical component of the ongoing efforts to transition the global automobile fleet to electric vehicles and integrate renewable energy sources into the electricity grid. An important aspect of designing and optimizing lithium-ion batteries is a comprehensive understanding of the factors which impact the ability of the electrolyte in the battery to ferry the lithium ions from one electrode to the other, the process which enables them to release energy into the circuit to power a device. This thesis describes results obtained from measuring the diffusion of the ions within the electrolyte for both conventional liquid-state electrolytes, and emerging solid-state electrolyte materials. It also includes studies which make use of MRI to image the flow of ions within the liquid-state electrolyte of an operating battery mimic, and monitor the concentration changes of the ions across the electrolyte as a current is applied to it.

Recently, the production of lithium-ion batteries (LIB) has grown rapidly, highlighting the need for efficient and environmentally friendly recycling of LIB waste. In this work, the usage of so-called deep eutectic solvents (DESs) for the leaching of the LIB cathode material lithium cobaltoxide is investigated. The initial DESs investigated are mixtures of poly(ethylene glycol) (PEG200) and an organic acid: tartaric, ascorbic, citric, oxalic or succinic acid (PEG:TA (4:1), PEG:AA (8:1), PEG:CA (4:1), PEG:OA (2:1) and PEG:SA (6:1), the molar ratio in parenthesis). Thermogravimetric analysis shows that the solvents are stable up to 180-190 °C. DESs were analyzed with FTIR spectroscopy, pH was measured using a pH-meter and viscosity using a rolling-ball viscometer. The highest leaching efficiency was obtained using PEG:AA followed by PEG:OA, both having the ability to reduce Co(III). This ability was dominant over pH and viscosity influence. For the other three solvents, leaching efficiency increases in the order of decreasing pH (PEG:TA>PEG:CA>PEG:SA). More investigations of leaching as a function of time are needed to determine the impact of viscosity. PEG:CA and PEG:AA are used to study the impact of solid-to-liquid ratio. For PEG:AA the optimal S/L-ratio is 20 mg/g. For PEG:CA the optimal S/L-ratio is different for Li and Co. Three additional CA based DESs are made using ethylene glycol (EG) and choline chloride (ChCl): EG:CA, ChCl:EG:CA and ChCl:PEG:CA. Adding ChCl to EG:CA and PEG:CA increases the leaching efficiency from ca 5 and 10 to ca 30% and the color changes from pink to blue, indicating the formation of tetrachlorocobalt complexes. This reaction may produce chlorine gas, although none was detected using potassium iodide starch paper. Study of leaching as afunction of time of ChCl:EG:CA shows the reaction slows down significantly after 24 h, indicating that the reaction has reached or is near equilibrium at this point. Antisolvent crystallization of this solvent using ethanol was not succesful.

The acceleration towards achieving a low carbon society has raised many challenges in the energy sector. The existing systems, highly dependent on fossil fuels, are not sustainable and recommendations are made to accelerate the transition by using more renewable and low-carbon sources of energy. By being responsible for over 70 % of the greenhouse gas emissions, cities or districts have a major role to play in this transition and present a large potential for implementation of renewable energy systems. The optimization of those systems and a better use of energy are crucial to reduce emissions and reach carbon neutrality. This study evaluates the potential of the implementation of three storage solutions for a decentralized energy system in a residential cluster in Ludvika, Sweden, equipped with photovoltaics panels. The first solution includes stationary batteries, the second includes a hydrogen storage solution and the third offers a hybrid solution from the two previous storages. Simulations were conducted using two numerical tools with an hourly resolution.The first scenario was conducted using Spine modelling tools, and the other simulations, including the cost analysis, were conducted on Excel with the support of Visual Basic for Applications. The comparison between the three solutions showed that the stationary batteries, blessed with a higher efficiency, offers the best results. The autonomy of the site, initially at 19.1 %, was raised to 22.8 % due to the batteries, and the system allowed to save up to 9.6 MW∙h per year. The investment price of the battery system was the highest of the three solutions. However, the payback period is reached in 20 years, within the average lifespan of the batteries and 10 years shorter than with the other solutions. The results also showed that the benefits of implementing a hydrogen storage solution were not visible as the excess in the photovoltaic production was not enough to cover the energy demand in a long-term period.

Physics-based electrochemical models are useful tools for optimizing battery cell and material design, managing battery use, and understanding physical phenomena, all of which are key in enabling adoption of batteries to electrify transportation, grid storage, and other high carbon emission industries. Fitting these models to experiments can be a useful approach to determine missing parameters that may be difficult to identify experimentally. In this dissertation, two use cases of this approach — model parameterization and degradation tracking — are explored. An introduction to the need for batteries and an overview of challenges in the field is presented in Chapter 1. Of these challenges, those that can be addressed by battery modeling solutions are discussed in further detail. An overview of continuum level physics-based electrochemical models is provided, and the case is made for the utility of parameter estimation. In Chapter 2, an extension of a published model for lithium trivandate cathodes for lithiumion batteries is outlined. While the original model described (de)lithiation and phase change in the cathode, the new model describes simultaneous lithiation of the original phase, lithiation of the newly formed phase, and phase change. Parameters associated with the thermodynamics and kinetics of charge transfer and lithium transport in the second phase are estimated directly from experimental data. This study serves as an example of using the model fitting approach to determine model parameters that would be difficult to isolate and measure experimentally. Chapter 3 explores a similar concept of model parameterization, this time focusing on the electrode tortuosity. Tortuosity is a hard to quantify parameter that describes how tortuous of a path lithium ions must travel through an electrode or separator. Because there are several experimental measurement techniques suggested in the literature that do not always provide consistent results, an approach to fit the tortuosity to a standard rate capability experiment is introduced. The Bayesian approach returns uncertainties in tortuosity estimates, which can be used to predict a range of outcomes for high-rate performance. Covariance between parameters in the model and their impact on uncertainties in tortuosity is also discussed. Beyond model parameterization, parameter estimation can also be useful in the context of tracking degradation by fitting a physics-based model over the course of cycling and interpreting the evolution of the parameter estimates. In Chapter 4, this idea is explored by fitting the model developed in Chapter 2 to cycling of an LVO cell. Parameter estimates are interpreted in conjunction with traditional tear down and electrochemical analysis to identify root causes of degradation for this cell. Depending on the number of parameters being simultaneously estimated, it can become an onerous task to fit model parameters, especially if the physics-based model cannot easily be enclosed in an efficient optimization algorithm. To this end, machine learning (ML) can be useful. If a ML model is trained offline on synthetic data generated by a battery model to map the observable electrochemical data to parameters in the battery model, the ML model can be deployed to estimate parameters from experiment. These models can be referred to as inverse ML models, since they perform the inverse task of a "forward" physics based model. The procedure described above is implemented in Chapter 5. Interpretable ML models are trained on published synthetic data generated by equivalent circuit models. Pseudo-OCV (slow charge, C/25) full cell voltage curves are passed into the inverse ML models to estimate degradation modes in lithium ion batteries and classify which electrode limits cell capacity. These models are useful in diagnosing the state of the battery at any given time. Accuracies of the inverse ML models are evaluated on independent test sets also composed of synthetic data and are published to benchmark future diagnostic studies. The insights derived from the trained ML models in terms of which features in the full cell voltage curves are predictive of the degradation modes are compared to expert insights. In chapter 6, the robustness of the inverse ML approach towards model-experiment disagreement is probed. If the experiment does not directly map onto the protocol used to generate the synthetic training data for the ML model, or if the model itself is inherently a poor descriptor of experiment, the inverse ML model will inevitably return inaccurate estimates. In this chapter, a feed forward neural network (NN) is employed as the inverse ML model. In two case studies of model-experiment disagreement, the NN returns biased parameter estimates. A simple data augmentation procedure is introduced to mitigate these biases. Chapter 7 ties together the understanding developed in the previous chapters by applying more robust neural networks to estimate parameters for LVO cells cycled at different rates. This study demonstrates how to interpret parameter estimates in conjunction with cycling data to gain mechanistic insight into degradation. A complex map of coupled degradation hypotheses is reduced to a smaller subset of possible mechanisms for two exemplary LVO cells, and parameter estimates for a larger set of LVO cells are discussed. The framework presented in this study synergistically combines experiment, physics-based modeling, and machine learning to better understand degradation phenomena.

Abstract Background:  Electric Vehicles (EVs) have been identified as a sustainable alternative to reduce the world’s dependence on fossil fuels. EV sales are starting to reach significant numbers. Subsequently, the demand for Lithium-Ion Batteries (LIBs), a key component in EVs, has increased. Due to the higher demand, a greater volume of LIBs will enter the waste stream. The waste-management strategies commonly used for the disposal of LIBs create potential risks of soil and air pollution, affecting the sustainability of EVs. The underdeveloped waste-management strategies, and the environmental and social risks related to improper disposal of LIBs, makes the study of second-life strategies of LIBs relevant.  Circular Economy (CE) promotes circular instead of linear flows of materials to reduce environmental impacts and maximize resource efficiency. LIB recycling is gaining popularity since LIBs contain valuable metals such as cobalt and lithium. A major challenge for LIB recycling is developing economical ways to extract and process metals from spent LIBs. The reviewed literature points to aresearch gap formed by the lack of study on the standardization of LIBs aimed to improve LIB recycling. The research gap is relevant because the reviewed literature points to a connection between standardization, innovation, and sustainability. Innovation of LIBs is a driver of sustainable transportation solutions, and the study of LIB standardization is relevant for two reasons. Firstly, standardization may influence further innovations needed to enable sustainable transportation. Secondly, standardization is relevant to achieve better recycling of LIBs and reduce the negative environmental and health effects of improper LIB disposal. Objectives:  During the development of the theoretical framework, two paradoxes were observed. The first paradox is between the dimensions of innovation and sustainability. Innovation acts positively on sustainability by enabling LIB development necessary to include EVs in the transportation sector. On the other hand, improper disposal of LIBs results in pollution affecting sustainability negatively. The second paradox is between the dimensions of standardization and innovation. Academics perceive standardization either as an enabler or as a hinder to innovation. Standardization enables innovation by giving a path and conditions for further technological developments, but standardization could also constrain the freethinking needed in innovation. Considering that innovation of LIBs has been a driver in the development of EVs, often described as a sustainable transportation solution, the study of LIBs’ standardization is relevant in the context of further innovation and higher sustainability goals.  The purpose of this study is to help to fill the gap in existing research on LIB recycling by exploring what factors in the dimensions of standardization, innovation, and sustainability are perceived as relevant for LIBs’ standardization aimed for better recycling. Moreover, the purpose of this thesis is also to explore how these factors influence further innovation of LIBs. Consequently, this thesis seeks to answer the following research question: What factors are perceived to be relevant for standardization of LIBs in the dimensions of standardization, innovation and sustainability aimed to improve recycling, and why? Also, how could these factors influence innovation of LIBs? Methodology:  Research in standardization aimed for recycling of LIBs is in its infancy. Therefore, the research problem is perceived as unstructured and modestly understood. Consequently, an exploratory research design has been selected for this thesis. The chosen research strategy was to conduct a case study focused on automotive firms. The selection of the case was based on four criteria. The first criterion was to select a firm in Sweden. The second criterion was to choose a firm with a defined strategy towards electric vehicles and a track of being innovative. A third criterion behind the selection was the firm’s potential for growth in units sold. The fourth criterion was that the firm should have a publicly known ambition or strategy towards sustainability. Volvo Cars Corporation (VCC) fulfilled all four criteria and was selected as the study case for this thesis. Data was collected by conducting semi-structured interviews with key organizational members involved in work related to second-life strategies of LIBs, development of LIBs, sustainability analysis, andlegislations or standardization. The sampling then focused on informants in the business areas of R&D,which covers these organizational activities. The interview questions were based on factors found to berelevant during the literature review within the dimensions of standardization, innovation, and sustainability. Also, each factor was associated with corresponding attributes. The formulation of the interview questions aimed to explore the relevance of an attribute for the standardization of LIBs aimed for better recycling and to explore how the factor influences innovation. The explored factors in the dimension of standardization were the source of standard, working groups for standardization development, practices during standard development, and design of standards. Meanwhile, the explored factors in the dimension of innovation were network effects and barriers to entry. In the sustainability dimension, the explored factors were exploration-exploitation balance and network effects.  The data analysis for the interviewees was based on first-order categorization of the answers, followed by creating second-order themes. The first-order categories and second-order themes were used for analyzing and assessing the relevance of the explored factors for the standardization of LIBs. Afterward, the second-order and aggregate themes were considered for the analysis of the factors’ influence on innovation. Moreover, the second-order themes have been used to identify new relevant factors to be considered in the standardization of LIBs with an influence in innovation. In this work, those identified relevant factors are referred asidentified elements. Finally, the analysis for the influence of the identified elements on innovation was visualized by the elaboration of a thematic map.  Results & Analysis:  The explored factors of standardization sources, working groups for standardization development, practices during development of standards and design of standards within the dimension of standardization were perceived as relevant and influenced innovation in combination with other identified elements. The most relevant identified elements were maturity, rigid standards, harmonization, flexibility, tacit knowledge, and culture. Maturity and rigid standards were perceived as the dominant among the identified elements by being important to avoid a negative influence on innovation caused by technology lock-in and obsolescence of the developed standards. Regarding identified elements with a positive influence on innovation, harmonization, culture, tacit knowledge, and flexibility are perceived as relevant to innovation by enabling common solutions in harmonized alliances, clarity in scope for the standards, and allowing freedom in the choice of methods. In the case of explored factors in the dimensions of innovation and sustainability, the explored factors of networks effects, entry barriers, and exploration-exploitation were perceived as relevant for the standardization of LIBs. Moreover, the results of the identified elements showed technology lock-in and iiiinefficient products as the biggest influence negatively affecting innovation and sustainability,respectively. The most important identified elements are maturity and investments for the technology lock-in aggregate theme, whereas efficiency, pricing, and environmental impact are identified for the case of inefficient products. Regarding aggregate themes enabling innovation and sustainability, they were presented in the form of resource and process optimization, market dynamics, and holistic view. Among the dominant identified elements enabling innovation are efficiency and specialized facilities.In addition to positive and negative aggregate themes, the aggregate theme of technology path was created. This aggregate theme refers to a technology development path that could influence innovation and or sustainability in potentially different ways: positive, neutral, or negative. The dominant identified elements in this theme are infrastructure, social realm, and consumer preference and awareness. Conclusions:  This thesis explored the relevance of factors in the dimensions of standardization, innovation, and sustainability on LIB standardization and their influence on the innovation of LIBs. The exploration of the factors’ perceived relevance answered the research question and resulted in new identified elementsrelevant to be considered in the standardization of LIBs with an influence on innovation. Consequently, this thesis fulfilled its purpose by helping to fill the gap in the existing research on LIB recycling. The main conclusions for the exploration of factors within the dimension of standardization are two. Firstly, the explored factors are relevant to be considered in the standardization of LIBs. Secondly, the exploration led to the new identified elements with negative and positive influence on innovation. The identified elements of maturity and rigid standards showed a negative influence on innovation in the form of technology lock-in or obsolescence of standards. However, the identified elements of harmonization, flexibility, tacit knowledge, and culture, showed a positive influence on further innovation of LIBs. The main conclusions for the dimensions of sustainability and innovation were that the explored factors are relevant in LIB standardization. Also, high compatibility between LIB manufacturers and recyclers raises challenges towards innovation while supporting sustainability. Also, consumer preferences and their shifts play a central role with negative and positive influence on innovation and sustainability and as a driver to certain segments of standardization.

Lithium-ion battery responses to bipolar pulse perturbations of less than two minute duration and one C-rate amplitude are studied as general-purpose diagnostics signals that encode the cell impedance, remaining charge, and degradation level. It is shown that the information is derived from a combination of the linear and nonlinear system dynamics of the electrochemical overpotentials, open-circuit voltage change, and hysteresis of the cell. Experimental data is analyzed using an equivalent circuit composed of a conventional resistor-capacitor pair model, a square-root-order convolution-defined diffusion element, and a piece-wise-linear open-circuit voltage element. This bipolar pulse model disaggregates the battery voltage response into its constituent dynamics and allows the nonlinearities to be isolated. The nonlinearities are crucial features which allow the battery charge, health, and incremental capacity features to be regressed directly from the pulse voltage response using ridge regression and feedforward neural networks. Assessment of different pulse shapes suggests that the diagnostics power of the pulse may increase with higher amplitude and shorter duration. Real-world applications are then investigated, including the estimation of charge imbalance using the series-module pulse response, and state-space formulation of the convolution-defined diffusion element. Further refinement of the pulse techniques could simplify battery diagnostics by providing, from a single pulse diagnostic, the key states of charge, health, and power necessary to operate a reliable system.

Ni-rich layered oxide materials have gained significant attention due to the ongoing advances and demands in energy storage. The energy revolution continues to catapult the need for improved battery materials, especially for applications in portable electronic devices and electric vehicles. Lithium batteries are at the frontier of energy storage. Due to geopolitical concerns, there is a growing need to understand the chemistries of Co-free, Ni-rich layered oxide materials which are cost-efficient and possess increased practical capacity. The challenge to studying this class of materials is their inherent electronic and structural fragility. The fragility of these materials is facilitated by a cooperation of metal cation migration, lattice oxygen loss, and undesirable oxide cathode-electrolyte interfacial reactions. Each of these phenomena contribute to complex electrolyte decomposition pathways and oxide cathode structural distortions. Structural instability leads to poor battery performance metrics including specific capacity fading and decreased Coulombic efficiency. Electrolyte decomposition occurs at the oxide cathode surface, but it can lead to bulk electronic and structural changes, chemomechanical breakdown, and irreversible phase transformations in the material. The work in this dissertation focuses on understanding some of the chemistries associated with degradation of representative Ni-rich layered oxides, specifically LiNiO2 (LNO) and LiNixMnyCozO2 (NMC) (where x+y+z =1) materials. Chapter 1 provides a comprehensive review of the interfacial chemistries of fragile, Ni-rich layered oxide materials with carbonate-based liquid electrolytes. These reactions are key in deducing mechanistic pathways that promote thermal runaway. Uncontrollable oxygen loss and electrolyte oxidation leads to catastrophic battery fires and explosions. The chapter highlights the material properties that become perturbed during high states-of-charge which complicate the materials chemistry associated with Ni-rich layered oxides. Lastly, a few strategies to mitigate undesired, structurally detrimental reactions at the Ni-rich layered oxide cathode surface are provided in Chapter 1. To obtain the technical data detailed in this dissertation, a variety of analytical methods are employed. Chapter 2 introduces the working principles of the X-ray techniques, electron microscopy, and other quantification methods. X-ray techniques including synchrotron X-ray absorption spectroscopy (XAS), and its components XANES and EXAFS are discussed. Other X-ray techniques, including X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are additionally included. Electron microscopy techniques, including transmission electron microscopy (TEM), scanning electron microscopy (SEM), and scanning transmission electron microscopy (STEM) are provided. Quantification methods, such as gas chromatography – flame ionization detection (GC-FID) and other electrochemical testing methods are also described. Detailed experimental information obtained using the analytical methods is provided in the technical chapters. In understanding the chemistry of Ni-rich layered oxides, exploring surface reconstruction is key. Surface reconstruction, a phenomenon caused by a collaboration between Li/Ni cation intermixing and lattice oxygen loss, is one of the major explanations for structural degradation in Ni-rich layered oxide materials. Chapter 3 explores surface reconstruction and deduces a mechanism by which lattice oxygen is loss in LiNi0.6Mn0.2Co0.2O2 (NMC622). By exploiting Li+ intercalation chemistry, the work emulates various states-of-charge to explore how delithiation impacts small, organic molecule oxidation. Benzyl alcohol serves as a good probing molecule. It is similar to an oxidizable, nonaqueous electrolytic species that undergoes oxidation at the oxide cathode surface. Structure-reactivity trends are defined to correlate electronic and structural changes, lattice oxygen loss, and small molecule oxidation. After studying a proxy molecule, a practical system is required to grasp the complexity of the cathode-electrolyte interfacial reactions that promote Ni-rich layered oxide degradation. In Chapter 4, an electrolyte stirring experiment is described. Stirring experiments provide an accelerated testing method which helps to deduce the influences of chemical electrolyte decomposition on structural degradation of LiNiO2 (LNO). X-ray techniques are used to illustrate electronic perturbations and structural distortions in the material after probing with EC/DMC w/w 3:7 LiPF6. Additionally, this dissertation chapter features a novel voltage oscillation experiment that is employed to quantify Ni-rich oxide cathode degradation at the phase transition regions. LNO has three charging plateaus – H1  M, M  H2, and H2  H3. The latter two plateaus have been largely associated with irreversible structural fragility in Ni-rich layered oxides. Cation intermixing and oxygen loss are two phenomena that are largely associated with decreased Li+ intercalation kinetics and increased undesired side reactions. Although researchers debate the chemical phenomenon that occur at each of the phase transitions, most agree that the H2  H3 transition is highly influenced by irreversible lattice oxygen loss. This dissertation chapter describes the studies used to explore the electronic changes and structural distortions that accompany the voltage oscillation electrochemical testing. While Ni-rich layered oxides are largely employed as lithium battery cathodes, this class of material is unique in that it is a reducible and electronically tunable. Electronically modifiable metal oxide materials provide a unique platform to lend information to other applications, such as catalysis. There is much debate surrounding the role of metal oxides on metal nanocatalyst performance for catalytically reductive pathways. Chapter 5 discusses the method of employing LiNiO2 and other NMC materials as electronically tunable metal oxides to determine the role of the reducible metal oxide support on the gold (Au) nanocatalyst for p-nitrophenol reduction to p-aminophenol. By obtaining a continuum of nickel (Ni) oxidation states using delithiation strategies, structural-activity relationship trends are provided. Conversion rates for each of the delithiated materials was calculated using pseudo first-order kinetics. Lastly, a detailed discussion on metal oxide reducibility and its influences on key mechanistic factors, such as the induction period is included. Chapter 6 in this dissertation provides conclusions for the technical work provided. It bridges the works together and describes the overarching findings associated with the chemistries of Ni-rich layered oxide materials. This dissertation lays the foundation for future experimentation and innovation in understanding the surface chemistry of Ni-rich layered oxides. Chapter 7 provides future perspectives for each of the technical works included herein. Additionally, the final chapter includes insights toward the future of lithium batteries and other cathode chemistries. As the world navigates the energy revolution, it is important to provide global perspectives expected to catapult a sustainable future with batteries towards a greener world. / Doctor of Philosophy / Rechargeable lithium batteries have gained a significant surge of interest due to the ongoing demands for portable electronic devices, as well as the global trend towards electric vehicles to decrease the carbon footprint. Lithium batteries reside at the pinnacle of the energy transition. Layered oxide materials are typically employed as the cathode in Li-ion batteries. Ni-rich layered oxides have gained much interest due to their low cost and good charge/discharge capabilities. As consumers want increased charging rates and longer lifetimes, researchers struggle to optimize the balance between incorporating Ni-rich cathodes and increased safety concerns caused by cathode structural fragility. The lack of structural robustness is largely due to the surface reactivity of Ni-rich layered oxide materials. Bonding arrangements and electron transfer pathways intrinsic to this class of material increases the complexity in understanding the surface chemistry and the associated degradation pathways. Oxygen loss is the major cause of the safety issues in lithium batteries such as battery fires and explosions. To mitigate the safety concerns, it is imperative to understand the chemistries that promote organic, liquid electrolyte decomposition, electronic and structural changes, chemomechanical breakdown, and irreversible phase transformations. Each of these components leads to decreased battery performance. The work in this dissertation describes model and practical platforms to probe and understand the chemistries associated with battery performance degradation. A variety of analytical methods were utilized to determine overall structure-activity relationship trends and are highlighted in Chapter 2. Chapters 3-5 is technical research providing insight on Ni-rich layered oxide degradation pathways and behaviors. The work advances the understanding of battery surface chemistry which will lead to improved cathode design. As batteries continue to grow, it is important to know other applications that benefit from the unique chemistry of Ni-rich layered oxide materials. By exploiting the lithium battery cathode chemistry, this dissertation highlights a method to utilize these materials to understand the role of metal oxides on Au nanocatalysts. Conclusions to the findings in this dissertation are provided in Chapter 6. Future perspectives on the technical research provided herein this dissertation is included in Chapter 7. Additionally, Chapter 7 details future perspectives for lithium batteries and how they can facilitate the global transition toward a sustainable future.

Alkali-ion batteries have revolutionized modern life through enabling the widespread application of portable electronic devices. The call for adapting renewable energy in many applications will also see an increase in the demand of alkali-ion batteries, specially to account for the intermittent nature of the renewable energy sources. However, the advancement of such technologies will require innovation on the forefront of materials development as well as fundamental understanding on the physical and chemical processes from atomic to device length scales. Herein, we focus on advancing energy storage devices such as alkali-ion batteries through cathode materials development and discovery as well as fundamental understanding through multiscale advanced synchrotron spectroscopic and microscopic characterizations. Multiscale electrochemical properties of cathode materials are unraveled through complementary characterizations and design principles are developed for stable cathode materials for alkali-ion batteries. In Chapter 1, we provide a comprehensive background on alkali-ion batteries and cathode materials. The future prospect of Li-ion and beyond Li-ion batteries are summarized. Surface to bulk chemistry of alkali-ion cathode materials is introduced. The prospect of combined cationic and anionic redox processes to enhance the energy density of cathode materials is discussed. Structural and chemical complexities in cathode materials during electrochemical cycling as well as due to anionic redox are summarized. In Chapter 2, we explain an inaugural effort on tuning the 3D nano/mesoscale elemental distribution of cathode materials to positively impact the electrochemical performance of cathode materials. We show that engineering the elemental distribution can take advantage of depth dependent redox reactions and curtail harmful side reactions at cathode-electrolyte interface which can stabilize the electrochemical performance. In Chapter 3, we show that the surface to bulk chemistry of cathode particles is distinct under applied electrochemical potential. We show that the severe surface degradation at the beginning stages of cycling can impact the long-term cycling performance of cathode materials in alkali-ion batteries. In Chapter 4, we utilize the structural and chemical complexities of sodium layered oxide materials to synthesize stable cathode materials for half cell and full cell sodium-ion batteries. Meanwhile, challenges with enabling long term cycling (more than 1000 cycles) are deciphered to be transition metal dissolution and local and global structural transformations. In Chapter 5, we utilize anionic redox in conjunction with conventional cationic redox of cathode materials for alkali-ion batteries to enhance the energy density. We show that the stability of anionic redox is closely related to the local transition metal environment. We also show that a reversible evolution of local transition metal environment during cycling can lead to stable anionic redox. In Chapter 6, we provide design principles for cathode materials for advanced alkali-ion batteries for application under extreme environments (e.g., outer space and nuclear power industries). For the first time, we systematically study the microstructural evolution of cathode materials under extreme irradiation and temperature to unravel the key factors affecting the stability of battery cathodes. Our experimental and computational studies show that a cathode material with smaller cationic antisite defect formation energy than another is more resilient under extreme environments. / Doctor of Philosophy / Alkali-ion batteries are finding many applications in our life, ranging from portable electronic devices, electric vehicles, grid energy storage, space exploration and so on. Cathode materials play a crucial role in the overall performance of alkali-ion batteries. Reliable application of alkali-ion batteries requires stable and high-energy cathode materials. Hence, design principles must be developed for high-performance cathode materials. Such design principles can be benefited from advanced characterizations that can reveal the surface-to-bulk properties of cathode materials. Herein, we focus on formulating design principles for cathode materials for alkali-ion batteries. Aided by advanced synchrotron characterizations, we reveal the surface-to-bulk properties of cathodes and their role on the long-term stability of alkali-ion batteries. We present tuning structural and chemical complexities as a method of designing advanced cathode materials. We show that energy density of cathode materials can be enhanced by taking advantage of a combined cationic and anionic redox. Lastly, we show design principles for stable cathode materials under extreme conditions in outer space and nuclear power industries (under extreme irradiation and temperature). Our study shows that structurally resilient cathode materials under extreme irradiation and temperature can be designed if the size of positively charged cations in cathode materials are almost similar. Our study provides valuable insights on the development of advanced cathode materials for alkali-ion batteries which can aid the future development of energy storage devices.

The development and commercialization of alkali ion secondary batteries has played a critical role in the development of personal electronics and electric vehicles. The recent increase in demand for electric vehicles has pushed for lighter batteries with a higher energy density to reduce the weight of the vehicle while with an emphasis on improving the mile range. A resurgence has occurred in lithium, and sodium, metal anode research due to their high theoretical capacities, low densities, and low redox potentials. However, Li and Na metal anodes suffer from major safety issues and long-term cycling stability. This dissertation focuses on the investigation of the interfacial chemistries between alkali metal-carbon host interactions and the electrode-electrolyte interactions of the cathode and anode with boron-based electrolytes to establish design rules for "lean" alkali metal composite anodes and improve long-term stability to enable alkali metal batteries for practical electrochemical applications. Chapter 2 of this thesis focuses on the design and preliminary investigation of "lean" lithium-carbon nanofiber (<5 mAh cm-2) composite anodes in full cell testing using a LiNi0.6Mn0.2Co0.2O2 (NMC 622) cathode. We used the electrodeposition method to synthesize the Li-CNF composite anodes with a range of electrodeposition capacities and current densities and electrolyte formulations. Increasing the electrodeposition capacity improved the cycle life with 3 mAh cm-2 areal capacity and 2% vinylene carbonate (VC) electrolyte additive gave the best cycle life before reaching a state of "rapid cell failure". Increasing the electrodeposition rate reduced cycling stability and had a faster fade in capacity. The electrodeposition of lithium metal into a 2D graphite anode significantly improved cycle life, implying the increased crystallinity of the carbon substrate promotes improved anode stability and cycling capabilities. As the increased crystallinity of the carbon anode was shown to improve the "lean" composite anode's performance, Chapter 3 focuses on utilizing a CNF electrode designed with a higher degree of graphitization and probing the interacting mechanism of Li and Na with the CNF host. Characterization of the CNF properties found the material to be more reminiscent of hard carbon materials. Electrochemical analysis showed better long-term performance for Na-CNF symmetric cells. Kinetic analysis, using cyclic voltammetry (CV), revealed that Na ions successfully (de)intercalated within the CNF crystalline interlayers, while Li ions were limited to surface adsorption. A change in mechanism was quickly observed in the Na-CNF symmetric cycling from metal stripping/plating to ion intercalation/deintercalation, enabling the superior cycling stability of the composite anode. Improving the Na metal stability is necessary for enabling Na-CNF improved long-term performance. Sodium batteries have begun to garner more attention for grid storage applications due to their overall lower cost and less volumetric constraint required. However, sodium cathodes have poor electrode-electrolyte stability, leading to nanocracks in the cathode particles and transition metal dissolution. Chapter 4 focuses on electrolyte engineering with the boron salts sodium difluoro(oxolato)borate (NaDFOB) and sodium tetrafluoroborate (NaBF4) mixed together with sodium hexafluorophosphate (NaPF6) to improve the electrode-electrolyte compatibility and cathode particle stability. The electrolytes containing NaDFOB showed improved electrochemical stability at various temperatures, the formation of a more robust electrode-electrolyte interphase, and suppression in transition metal (TM) reduction and dissolution of the cathode particles measured after cycling. In Chapter 5, we focus on the electrochemical properties and the anode-electrolyte interfacial chemistry properties of the sodium borate salt electrolytes. Similar to Chapter 4, the NaDFOB containing electrolytes have improved electrochemical performance and stability. Following the same electrodeposition parameters as Chapter 2, we find the NaDFOB electrolytes improves the stability of electrodeposited Na metal and the "lean" composite anode's cyclability. This study suggests the great potential for the NaDFOB electrolytes for Na ion battery applications. / Doctor of Philosophy / The ever-increasing demand for high energy storage in personal electronics, electric vehicles, and grid energy storage has driven for research to safely enable alkali metal (Li and Na) anodes for practical energy storage applications. Key research efforts have focused on developing alkali metal composite anodes, as well as improving the electrode-electrolyte interfacial chemistries. A fundamental understanding of the electrode interactions with the electrolyte or host materials is necessary to progress towards safer batteries and better battery material design for long-term applications. Improving the interfacial interactions between the host-guest or electrode-electrolyte interfaces allows for more efficient charge transfer processes to occur, reduces interfacial resistance, and improves overall stability within the battery. As a result, there is great potential in understanding the host-guest and electrode-electrolyte interactions for the design of longer-lasting and safer batteries. This dissertation focuses on probing the interfacial chemistries of the battery materials to enable "lean" alkali metal composite anodes and improve electrode stability through electrolyte interactions. The anode-host interactions are first explored through preliminary design development for "lean" alkali composite anodes using carbon nanofiber (CNF) electrodes. The effect on increasing the crystallinity of the CNF host on the Li- and Na-CNF interactions for enhanced electrochemical performance and stability is then investigated. In an effort to improve the capabilities of Na batteries, the electrode-electrolyte interactions of the cathode- and anode-electrolyte interfacial chemistries using sodium borate salts are probed using electrochemical and X-ray analysis. Overall, this dissertation explores how the interfacial interactions affect, and improve, battery performance and stability. This work provides insights for understanding alkali metal-host and electrode-electrolyte properties and guidance for potential future research of the stabilization for Li- and Na-metal batteries.