Browsing by Author "Prieto, Amy, advisor"
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Item Open Access Electrochemically prepared metal antimonide nanostructures for lithium ion and sodium ion battery anodes(Colorado State University. Libraries, 2016) Jackson, Everett D., author; Prieto, Amy, advisor; Rappe, Anthony, committee member; Dandy, David, committee member; Bailey, Travis, committee member; Henry, Charles, committee memberThe use of energy fundamentally enables and globally supports post-industrial economies and is critical to all aspects of modern society. In recent years, it has become apparent that we will require superior energy technologies to support our society, including improved methods of generating, storing, and utilizing energy resources. Battery technology occupies a critical part of this new energy economy, and the development of electrochemical energy storage devices will be a critical factor for the successful implementation of renewable energy generation and efficiency strategies at the grid, transportation, and consumer levels. Current batteries suffer from limitations in energy density, power density, longevity, and overall cost. In addition, the inherent tradeoffs required in battery design make it impossible to create a single battery that is perfect for all applications. To overcome these issues, the development of low-cost and high-throughput methods, new strategies for materials design, and a comprehensive understanding of electrochemical mechanisms for battery performance is necessary. Herein, an in-depth study on the electrochemistry of a model anode system for rechargeable batteries based on metal antimony alloys produced through an electroplating approach is detailed. The first chapter of this dissertation provides a brief introduction of lithium ion and sodium ion battery technology. In the second chapter, a detailed review of the literature on antimony and metal antimonide alloys for battery anodes is provided. The third chapter details a study on copper antimonide thin films with varying stoichiometry produced through a facile electrodeposition process. In the fourth chapter, stoichiometric Cu2Sb thin films are studied as potential anodes for sodium ion batteries. The fifth chapter details the development of a process for electroplating zinc-antimony alloy thin films onto zinc and their electrochemical properties in sodium ion cells. The sixth and seventh chapters report the synthesis and characterization of copper-antimony alloy nanowire arrays produced through an alumina-templated process. These nanowire arrays are first used in an electrolyte-additive study to show the importance of surface stabilization for high surface area electrodes in chapter five. In chapter six, the rate performance is characterized under different thermal conditions for different compositions of copper-antimony alloy nanowire arrays as an assessment of the kinetic limitations of this electrode. The final chapter briefly describes some preliminary experiments that have been performed on characterizing the electrochemistry of metal salts in a deep eutectic solvent as a potential method for co-deposition of new metal antimonides.Item Open Access Energy storage improvement through material science approaches(Colorado State University. Libraries, 2013) Kelly, Brandon Joseph, author; Prieto, Amy, advisor; Kirkpatrick, Allan, committee member; Chen, Suren, committee member; Dasi, Prasad, committee memberA need for improved energy storage is apparent for the improvement of our society. Lithium ion batteries are one of the leading energy storage technologies being researched today. These batteries typically utilize coupled reduction/oxidation reactions with intercalation reactions in crystalline metal oxides with lithium ions as charge carriers to produce efficient and high power energy storage options. The cathode material (positive electrode) has been an emphasis in the recent research as it is currently the weakest link of the battery. Several systems of cathode materials have been studied with different structures and chemical makeup, all having advantages and disadvantages. One focus of the research presented below was creating a low cost and high performance cathode material by creating a composite of the low cost spinel structured LiMn2O4 and the higher capacity layered structure materials. Two compositional diagrams were used to map out the composition space between end members which include two dimensional layer structured LiCoO2, LiNiO2, LiNi0.8Co0.2O2 and three dimensional spinel structured LiMn2O4. Several compositions in each composition map were electrochemically tested and structurally characterized in an attempt to discover a high performance cathode material with a lower cost precursor. The best performing composition in each system shows the desired mixed phase of the layered and spinel crystal structures, yielding improved performance versus the individual end member components. The surrounding compositions were then tested in order to find the optimum composition and performance. The best performing composition was 0.2LiCoO2*0.7LiNi0.8Co0.2O2*0.1LiMn2O4 and yielded a specific capacity of 182mAh/g. Another promising area of chemical energy storage is in the storage of hydrogen gas in chemical hydrides. Hydrogen gas can be used as a fuel in a variety of applications as a viable method for storing and transporting energy. Currently, the storage of the hydrogen is one of the major obstacles to its use as a fuel, and is traditionally done in high pressure cylinders or cryogenic storage tanks. Chemical hydrides allow storage of hydrogen in a solid form with higher volumetric hydrogen storage density than both traditional options. These chemical hydrides however are not performing close to their theoretical values and need further improvement in order to be viable in mobile applications. In this study two complex chemical hydride materials (Li3AlH6 and LiNa2AlH6) with high theoretical storage values were studied and doped with catalysts in an attempt to increase the hydrogen yield. The successful improvement of both Li3AlH6 and LiNa2AlH6 with 2%LaCl3 catalyst was achieved improving the chemical hydrogen yield percent by 4.6% and 22.9% respectively.Item Open Access Investigation of the growth mechanism of highly branched silica nanowires grown using in-situ Cu-catalyst loading, and the development of electrochemical anodization synthetic methods specifically targeting solid ionically conducting materials(Colorado State University. Libraries, 2023) Boissiere, Jacob Daniel, author; Prieto, Amy, advisor; Finke, Richard, committee member; Rappe, Anthony, committee member; Dandy, David, committee memberGaining a better understanding of the world around us is the fundamental objective of science, with chemistry looking to better understand the processes and applications that occur on a molecular and sub-molecular scale. Developing this better understanding has allowed us to create medicine and computers, begin exploring space and understanding the atom and is a never-ending process of asking questions and testing hypotheses as we work toward an increasingly objective answer. The best that I can hope for, not only in my time in graduate school, but as I move forward in life, is that I have moved this understanding, even in the slightest, in the correct direction. This may be a small impact, but much of the work presented in this dissertation will focus on small things. Two significant research directions will be presented along with work on device and process development for characterization. The first major system that will be discussed is the chemical vapor deposition of highly branched silica nanowires that were grown in a single synthetic step as a result of in-situ Cu-catalyst loading. The second research direction involves the investigation into using electrochemical anodization synthesis as a way to target the formation and discovery of ionically conducting materials. The overall link between these research topics involves the focus on solid inorganic materials, with a broad direction of understanding materials systems, process development and optimization, careful characterization, hypothesis generation, and considerations of potential applications and future directions of the materials and techniques being investigated. Systems of interest could loosely be classified as energy related materials. Both systems provided unique and challenging aspects to understanding the synthetic processes involved as products were formed under highly dynamic environments. Additionally, device and process developments were perused to address systematic variables such as instability of products and improve overall reaction design and therefore reproducibility and significance of results. The first system investigated involved the chemical vapor deposition of silicon-based nanowire products. The initial objective of the project was to investigate the unique structures of highly branched nanowires that were grown through in-situ doping of Cu, and investigate their properties and performance as a potential anode material for use in Li-ion battery devices. The synthetic method used, and the unique structures observed were previously reported by the Prieto research group. The hypothesis was that these products were grown as crystalline Si and being catalytically oxidized due to the presence of Cu and Cu3Si post synthesis. The work presented here disproves this hypothesis, instead proposing that the product is grown as the oxide. Due to this new conclusion, the battery application study was no longer pursued, and investigation instead focused on developing and proposing a new growth hypothesis. This new hypothesis involves the formation of a multi-wire backbone, which is believed to be the first report to directly investigate and explain this phenomenon. The second research direction outlines the motivation, theory, and initial outcomes of attempting to develop a new synthetic methodology for ionically conducting materials through electrochemical anodization. While anodization is itself far from a new synthetic method, it has never been used to synthesize the targeted material systems, nor has it been used to pursue the synthesis of ionically conducting materials generally. Much of the discussion will revolve around the background, motivation, and hypotheses relating to this project. This focus is partially due to the limited success of certain research objectives, but the intention is to hopefully highlight the intrinsic value of the synthetic concept and theory behind it, as well as direct future potential research based on what has been learned. The synthetic results and discussion focus on the anodization synthesis of AgI, the morphologies and crystallographic properties of the materials formed, and insights into the synthetic process. The related systems of CuI and CuxS will also be touched upon, as well as attempts to pursue the synthesis of Na3PS4. Throughout these investigations, a variety of side project and collaborations were worked on, but the one of significance that will be included in the final chapter relates to the development of an air-free sample transfer holder. This was developed to allow the air-free transfer of a surface sensitive material between a glove-box and an X-ray photoelectron spectroscopy instrument. This enables more accurate and meaning data to be collected on samples that could otherwise be modified or compromised through exposure to ambient air before analysis.Item Open Access Part I: Structural characterization of doped nanostructured magnesium: understanding disorder for enhanced hydrogen absorption kinetics. Part II: Synthesis, film deposition, and characterization of quaternary metal chalcogenide nanocrystals for photovoltaic applications(Colorado State University. Libraries, 2017) Braun, Max B., author; Prieto, Amy, advisor; Finke, Richard, committee member; Rappe, Anthony, committee member; Neilson, James, committee member; de la Venta, Jose, committee memberThe production, storage, and subsequent consumption of energy are at the foundation of all human activity and livelihood. The theme of this dissertation is the pursuit of fundamentalunderstanding of the chemistry of materials that are used for energy production and storage. A strong emphasis is placed on a synthetic foundation that allows for systematic investigation into the fundamental chemistry that controls the applicable properties of the materials of interest. This dissertation is written in the "journals format" style—which is accepted by the Graduate School at Colorado State University—and is based on one peer-reviewed publication that has appeared in Chemistry of Materials as well as two manuscripts to be submitted, one to The Journal of Physical Chemistry C, and one to ACS Applied Materials and Interfaces. In order to create a context forthese publications, Chapters 1 and 3 provide an overview of the motivations for the projects, and then continue to detail the initial synthetic investigations and considerations for the two projects. In addition to recounting Mg nanocrystals synthetic refinement that was necessary for reproducible hydride kinetic analysis, Chapter 1 also briefly introduces some of the conventional models used for fitting of the hydriding kinetics data. Furthermore, initial investigations into the use of these models for our system are presented. Chapter 2 is a paper to be submitted to The Journal of Physical Chemistry C that describes the local and extended structure characterization of Mg nanocrystals (NCs) with a small amount of nickel added during synthesis. Ni has a dramatic effect on the de/hydriding kinetics of Mg NCs, and this chapter describes the use of a combination of multiple state-of-the-art characterization techniques to gain insight into the structural perturbations due to Ni inclusion in the Mg NCs. This insight is then used to establish the characteristics of Ni inclusion that results in the enhanced hydrogen absorption processes. Chapter 3 introduces the many considerations needed to be taken into account during the development of a novel synthesis for copper zinc tin chalcogenide colloidal nanocrystals. In addition to introducing synthetic approaches to achieve this goal, Chapter 3 also describes essential characteristics that need to be considered for further investigation into the properties of films made from the nanocrystals. Chapter 4 is a publication that appeared in Chemistry of Materials, that describes an approach to tuning the surface and ligand chemistry of Cu2ZnSnS4 nanocrystals for use as an absorber layer in next generation photovoltaic devices. The publication describes ligand exchange chemistry achieved via layer-by-layer dip-casting of nanocrystal thin films, and the effects that this exchange chemistry has on the resulting films. It also details the fabrication of full photovoltaic (PV) devices to characterize the benefits of controlling the surface chemistry can have on PV performance. Chapter 5 is a paper—to be submitted to ACS Applied Materials and Interfaces—that describes the investigations into how varying the chalcogen ratio (i.e., S:Se) leads to changes in the physical and electrical properties of thin films made from Cu2ZnSn(S1-xSex)4 (where 0 < x < 1) NCs. It highlights the novel synthetic procedure (detailed in chapter 3) that was required for a systematic, deconvoluted evaluation of S:Se composition on the materials optical and electronic properties. Moreover, the characteristics of full PV devices based on thin films of each stoichiometry (x=0 to x=1) are assessed to establish a relationship between composition and the materials performance.Item Open Access Part I: Synthesis and characterization of titania and magnesium nanoparticles for hydrogen production and storage. Part II: Characterization and growth of branched silicon nanowires grown via a simultaneous vapor-liquid-solid and vapor-solid-solid mechanism(Colorado State University. Libraries, 2015) Shissler, Daniel Jay, author; Prieto, Amy, advisor; Shores, Matthew, committee member; Rappé, Anthony, committee member; Van Orden, Alan, committee member; Dandy, David, committee memberTo view the abstract, please see the full text of the document.Item Open Access Synthesis and characterization of iron and copper chalcogenide nanomaterials for photovoltaic applications(Colorado State University. Libraries, 2014) Fredrick, Sarah J., author; Prieto, Amy, advisor; Neilson, James, committee member; Rappé, Anthony, committee member; Strauss, Steven, committee member; Williams, John, committee memberWith our current looming energy and climate crises, it is vital that we find alternative forms of energy that have a lower carbon footprint. Solar technology is an excellent candidate for such purposes as the sun is an essentially unlimited source of renewable energy. However, the cost of solar cells is not economically competitive with fossil fuels. Alternatives to the traditional silicon solar modules could be a path toward reducing the cost of solar technology. The topic of this thesis is the synthesis and characterization of such alternatives. Iron and copper-based materials are earth abundant and potentially more cost-effective. Furthermore, processing these materials as nanocrystals, rather than bulk films, can reduce the energy input for fabricating solar absorber layers, and in turn, reduce overall system costs. Iron pyrite (FeS2) and a related material, Fe2GeS4 are two materials with near ideal properties for solar absorption. While there has been a great deal interest in FeS2, Fe2GeS4 is a novel system on which minimal research has been performed. Herein is described the synthesis and characterization of both of these iron chalcogenides with a particular focus on the challenging surface chemistry presented by these systems. Another system of increasingly widespread interest in recent years in the class of earth-abundant photovoltaic materials is Cu2ZnSnS4 (CZTS). A vast body of literature has been developed, but detailed characterization is lacking in much of the work, hindering our fundamental understanding of the properties. The final chapter of this thesis is a perspective work describing common characterization techniques for CZTS. It analyzes their usefulness in determining the formation of the pure CZTS phase, in hopes of improving current understanding of the material.Item Open Access Using antimony as a model anode to study the chemical and mechanical stability of electrodes in Li-ion and next generation batteries(Colorado State University. Libraries, 2019) Schulze, Maxwell Connor, author; Prieto, Amy, advisor; Shores, Matthew, committee member; Neilson, James, committee member; Weinberger, Chris, committee memberAs humanity grapples with the ever-increasing global demand for electrical energy, we are concurrently trying to curb global greenhouse gas emissions on massive scales to avoid potentially catastrophic changes in the global climate. Strategies to address these problems include transitioning away from a fossil fuel powered society where electrical grid energy is instead generated from renewable sources and internal combustion engine vehicles are replaced with electrified ones. Both of these transitions require energy storage technologies that can deliver high efficiencies, large energy densities, large power outputs, long lifetimes, and good safety factors all while remaining affordable and sustainable to produce. Li-ion batteries have already proven their merit as an effective energy storage technology with high enough energy densities, low enough costs, and long enough lifetimes to be ubiquitous in powering portable electronic devices. While the performance metrics of Li-ion batteries have also started to allow all-electric vehicles and grid-level energy storage to become commercially feasible, limitations in their cycle lifetimes and safety concerns arising from their flammable nature still limit their widespread implementation for these application. Ultimately, the interactions between constituent materials of a battery and the modes of their degradation limit a battery's performance. As such, research to understand and mitigate the degradation of battery materials, including those that move beyond Li-ion battery chemistry, is necessary to promote the widespread, tunable, and diverse use of batteries in overcoming the challenges discussed. Herein, I present a study that uses antimony as a model anode material to develop an understanding of the critical limiting factors of next-generation battery materials. Antimony-based anodes exhibit degradation and concomitant short cycle-lifetimes that are typical of many promising next-generation battery materials, including those that move beyond Li-ion chemistries. Thus, antimony-based model anodes can be used to study such degradation, which is primarily due to chemical and mechanical instability of the electrode and its interfaces with other battery cell components. In the following chapters, strategies to improve the chemical or mechanical stability of the antimony-anode and its interfaces are developed and can be more generally applied to other promising next-generation electrode materials. The following is a journal format dissertation, with each chapter being a document that is published, submitted, or in preparation to a peer-reviewed journal. The first chapter reviews the basic operating principles of rechargeable batteries as well as critically discusses the electrochemical experiments that are common in battery materials research. In particular, the first chapter emphasizes the limits of testing half-cell configurations in representing the cycle lifetimes of full-cell batteries, the key metric needed for long cycle lifetimes in full-cells being extremely high coulombic efficiencies. Chapter two explores and develops mitigation strategies for detrimental mechano-chemical interactions at the interface between the active Cu-Sb anode and the current collector that arise from the existence of a ternary Li-Cu-Sb phase with structural similarity to both Cu2Sb and Li3Sb. While the existence of the ternary phase results in good reversibility of Cu-Sb electrodes when cycled in Li-ion batteries, it also results in the formation of voids at Cu-Sb interfaces that exacerbates delamination during cycling to result in short cycle lifetimes. Chapter three develops a procedure for the electrodeposition of antimony carbon nanotube composites as a strategy to address the bulk mechanical instability of the anode during cycling in Li- and Na-ion batteries. Results of chapter three reveal significant chemical instability at the anode-electrolyte interface and motivate much of the work performed in chapter four, which departs from focusing on antimony as an anode material and instead uses antimony to explore the properties of anode coatings. Chapter four is a systematic study that explores how annealing conditions affect properties of polyacrylonitrile coatings relevant to the chemical stabilization of the electrode-electrolyte interface. This study reveals that ion diffusion in annealed polyacrylonitrile films is correlated to the delocalization of electrons in conjugated domains within the polyacrylonitrile films. Finally, chapter five reviews the materials properties that have made the Li-ion battery so successful, such as the mechanically and chemically stable interfacial layers that form at the electrode-electrolyte interfaces. The chapter additionally highlights some recent progress in the battery materials field and suggests that electrolyte additives, interfacial coatings, and solid-state electrolytes as the most impactful types of materials to continue researching and developing for the future.Item Open Access Using X-ray photoelectron spectroscopy to understand the solid electrolyte interphase formation in sodium ion batteries(Colorado State University. Libraries, 2022) Gimble, Nathan Jacob, author; Prieto, Amy, advisor; Ackerson, Christopher, committee member; Rappe, Anthony, committee member; Popat, Ketul, committee memberSodium-ion batteries offer a more sustainable energy storage alternative to lithium while maintaining many of lithium's important characteristics. The solid electrolyte interphase (SEI) forms on the surface of the anode in both sodium and lithium-ion batteries. The SEI effects battery performance, particularly in sodium batteries, and understanding how it forms is critical for developing sodium ion batteries. Chapter I of this dissertation motivates sodium ion batteries, outlines the important differences between sodium and lithium, introduces the SEI, and establishes how the SEI is studied, ultimately placing this work in context with the field. As the SEI is derived from the electrolyte and is affected by electrolyte additives, the small molecule electrolyte additive fluoroethylene carbonate (FEC) is introduced as it is investigated throughout the dissertation. Chapter II explains how X-ray photoelectron spectroscopy can be used to study the SEI, providing examples of important protocols and pitfalls. Chapter III examines SEI formation by correlating electrochemistry from differential capacity with X-ray photoelectron spectroscopy (XPS). It is revealed that SEI species appear as a result of applied chemistry when the small molecule additive FEC is present. Without FEC, the SEI is present without significant electrochemistry in the differential capacity. Chapter IV builds off the results in Chapter III, identifying the conditions of spontaneous SEI formation due to sodium metal reactivity with the electrolyte. The spontaneous formation of the SEI is mitigated by FEC, the role of which is understood to be pre-passivation of sodium metal to prevent further electrolyte decomposition. Chapter V summarizes the work in this dissertation and outlines different directions the work can take moving forward.