<p dir="ltr">The thesis goal was to design a quasi-solid-state battery electrolyte, which was optimized to function at ambient as well as low temperatures. In the first project, an array of quasi-solid-state electrolytes were developed and compared. A series of electrochemical, spectroscopic, and thermal experiments in addition to imaging techniques determined a top performer as well as elucidated possible mechanistic explanations. This systematic study attempted to validate literature conclusions about the failure mechanisms governing batteries (solid-state batteries) at ultralow temperatures, while also offering hypothesis driven additional insight. The optimized electrolyte, which will be deemed as CSPE@2MMeTHF, performed well for several key reasons, traced to the co-solvent used (Me-THF), the salt concentration, and its formation of a stable and suitable cathode-electrolyte interphase. It was able to perform well at 25 °C, and down to -25 °C. The second part of the work, focused on further optimizing the electrolyte by removing a ‘polymer wetting/soaking’ step, removing a ceramic component, and pairing it with a recently discovered anodic electrode material. Given that narrowing the research gap for low temperatures requires both electrolyte and electrode design, it was important to consider this aspect of the problem as well. The cathodic electrode used for the first project, traditionally performs poorly at low temperatures, allowing for a suitable experimental control for the electrolyte. However, the new anodic electrode had two ways of storing lithium ions, as opposed to just one in the former, making it an attractive option for the stated goal of a low-temperature solid-state battery. This second project is akin to a ‘proof-of-concept’ work and there is much more room for further study, especially in preparing a full cell with the aforementioned electrodes cathode (LFP) and anode (NbWO) with the second SPE@51DMMeT electrolyte. In summary, this thesis shows method design to prepare solid-state electrolytes with portion of liquid, two successfully developed electrolyte systems for low temperatures, and a rigorous discussion of factors that affect electrochemical performance. Demonstrated research activities are of great value to defense as the current lithium-ion batteries does not perform well at subzero temperatures.</p>

The increasing energy demand requires a transition from fossil fuels to renewable resources. Lithium-ion batteries (LIBs) offer a promising solution as efficient energy storage devices. However, the aluminum current collector (CC) in LIBs is susceptible to anodic dissolution above 3 V vs. Li+/Li in commercial carbonate liquid electrolytes, compromising the battery performance. In this study, various approaches were explored to mitigate anodic dissolution in LiFSI EC:DEC at high voltages of the aluminum CC in LIBs, employing cyclic voltammetry (CV) and scanning electron microscopy (SEM). It was found that boiling the Al foil in water in an air atmosphere to increase the thickness of the surface Al2O3 layer improved the anodic stability and offered enhanced protection against proton attack (due to the oxidation of the carbonate solvent at high voltage). However, increasing the LiFSI electrolyte concentration to 2 M did not increase the anodic stability due to the absence of a passivating AlF3 layer. Notably, in 4 M LiFSI, impurity-induced high F- concentration facilitated the formation of a passivating AlF3 layer, resulting in improved anodic stability. Moreover, specific volume ratios of LiFSI EC:DEC and 1 M LiPF6 EC:DEC (1:1) (LP40) yielded the F- concentration necessary for forming a passivating AlF3 layer and significantly enhanced the anodic stability. On the other hand, carbon-coating the Al foil did not show significant improvements regarding the anodic stability. It was found that the corrosion was time-dependent at a low scan rate, a drastic anodic dissolution of the aluminum was seen at higher temperatures, and the corrosion also became more pronounced. At room temperature, carbon-coated Al foils exhibited increased stability.

Prussian Blue analogues (PBAs) are a promising class of electrode active materials for batteries. Among them, copper nitroprusside, Cu[Fe(CN)5NO], has recently been investigated for its peculiar redox system, which also involves the nitrosyl ligand as a non-innocent ligand, in addition to the electroactivity of the metal sites, Cu and Fe. This paper studies the dynamics of the electrode, employing surface sensitive X-ray Photoelectron spectroscopy (XPS) and bulk sensitive X-ray absorption spectroscopy (XAS) techniques. XPS provided chemical information on the layers formed on electrode surfaces following the self-discharge process of the cathode material in the presence of the electrolyte. These layers consist mainly of electrolyte degradation products, such as LiF, LixPOyFz and LixPFy. Moreover, as evidenced by XAS and XPS, reduction at both metal sites takes place in the bulk and in the surface of the material, clearly evidencing that a self-discharge process is occurring. We observed faster processes and higher amounts of reduced species and decomposition products in the case of samples with a higher amount of coordination water.

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第24149号 / 人博第1052号 / 新制||人||246(附属図書館) / 2022||人博||1052(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 内本 喜晴, 教授 吉田 鉄平, 准教授 松井 敏明, 教授 林 晃敏 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

Electrochemical conversion devices are a developing technology that prove to be a viable and more efficient alternative to current environmentally friendly generation devices. As such, constant research has been done in the last few decades to increase their applications and reliability. One of these systems, and the focus of this research, is the single cell Solid Oxide Fuel Cell (SOFC). These systems are a developing technology which main caveat is the need of high operating temperatures and costs. As such, most multidisciplinary research has been focused on researching materials and/or processes that help mitigate the costs or lower the operating temperature. The research presented in this paper focused on the manufacturing of a cubic stabilized zirconia (CSZ) electrolyte thin membrane for a single cell SOFC through tape casting. Thus, the process was divided into slurry preparation, tape casting, further processing, and analysis of samples. First the tape was produced reaching optimal viscosity (between 500 to 6000 cP) and minimizing impurities. Then, the slurry was poured into the doctor's blade with a 200 micrometers gap and allowed to dry. Samples were punched from the green tape with a diameter of 28 inches. Afterwards, these samples were pressed and sintered with a force of 218016 N and temperature of 1550 degrees celsius, respectively. These steps are done to maximize density and grain growth and minimize porosity. Lastly, the tape went further analysis and it was stated that further research should be done to determine this tape viability for stationary SOFC application.

In this study, the effects of individual and combinatorial electrolyte solution comprised of carbohydrate, salt, and a stimulant injected into broiler hatching eggs on subsequent late term embryogenesis and post hatch performance up to D 10 were evaluated in separate trials. The effects of solution concentration and volume on embryo body weight and yolk reserves were likewise considered, and limited posthatch growth, body weight, and yolk sac effects of a compound electrolyte solution were evaluated. The individual and combinatorial effects of injected solutions were examined in an effort to yield the maximum physiological growth effects on embryogenesis from the metabolic pathways in which these compounds are involved. Limited effects on embryo and post hatch mortality were found. However, both post hatch yolk reserves and liver weights were affected by in ovo injection. These effects could be key in increasing bird weight by processing day.

This dissertation is written in two sections. The first section deals with the development of methods for the estimation of the effective electrolytic surface area of rough and porous silver electrodes in alkaline electrolyte. Data are presented comparing the results of three different methods of surface area estimation. Model pore electrodes were also prepared and oxidized to study the reactions in a pore. Data for constant current oxidations of these electrodes is given. The second section deals with the potentiostatic oxidations of silver in alkaline electrolyte. Data are presented on the total charge acceptance versus applied potential for a potential range that runs from the potential required to first produce silver (I) oxide to that required to evolve oxygen off the surface of the electrode. The shape of this plot indicates the formation of two types of silver (I) oxide. Three oxidation reactions were noted. The first was the formation of silver (I) oxide. The second was the formation of silver (II) oxide. The nature of the third reaction is not yet known; however, some evidence indicates it is the formation of silver (III) oxide.

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