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Lithium batteries play a critical and indispensable role in our modern way of life, enabling portability and further miniaturization of several technologies that would otherwise be either stationary or simply not possible. As one of the most important technologies of the twenty-first century, our civilization enjoys the immense benefits it currently offers, and that it stands to offer in the decades to come. The existence of current systems can be traced back to a compromise made during the initial stages of lithium battery commercialization, when energy content had to be sacrificed for safety, reliability and performance, due to the instability of the lithium metal anode when used with flammable, liquid electrolytes. Since then, academia and industry have embarked on a decades long quest to overturn this compromise, and recover that which has been lost. Liquid electrolytes and graphite anodes are largely responsible for the great benefits of high power that lithium batteries afford us, but achieving greater energy densities, safety and performance will require different battery materials; the question is which ones, the answer to which is a task complicated by the delicate balance of many factors. Current battery research has sought to develop solid electrolytes to do away with the flammability and explosion issues tied with liquid electrolytes, either in the form of polymer or inorganic electrolytes. Polymer electrolytes are flexible and easy to manufacture, but suffer from low ambient temperature conductivities and performance, while inorganic electrolytes have high conductivities and mechanical moduli, but are brittle and suffer from poor interfacial properties, including limited thermodynamic stability against electrode materials, in many cases. The ipossibility of combining together polymer and inorganic electrolyte materials, to give hybrid electrolytes, is attractive, but issues such as component compatibility, ionic transport across interfaces within the material, and the issues inherited from the parent materials, have frustrated efforts to find a successful hybrid electrolyte. The lack of a clear, superior hybrid system prevents focused efforts from being centered around a narrow set of systems, making it more difficult to identify additional clues that can inform current known requirements for hybrid systems. In this present work, systematic efforts to characterize first the individual components of novel hybrid systems, and subsequently to characterize model systems and complete hybrid systems, are described.Chapter 1 provides a framework of principles governing lithium batteries, as well as the current issues plaguing lithium battery research, while Chapter 2 lists the materials, methods and equipment used in this work. Chapter 3 focuses on identifying a suitable organic polymer matrix, capable of covalent attachment, as well as characterizing plates of the inorganic electrolyte lithium aluminum silicon phosporus titanium oxide (LASPT). This includes thermal and electrochemical characterization, including plate-strip measurements and impedance spectroscopy. To the end of better understanding these materials' electrochemical properties, the approach of systematically investigating various equivalent circuits is developed, for the purpose of modeling impedance data. A suitable silane polymer matrix, capable of covalent attachment, is found and dubbed "Entry 02". The chief lesson of this chapter is that function and performance need to be balanced, which in this case translates to covalent moieties and electrochemical performance, respectively. Chapter 4 centers around electrochemical characterization of model systems, consisting of a plate of the inorganic electrolyte LASPT sandwiched between two layers of an organic electrolyte. The organic electrolytes used are liquid and gel electrolytes, as well as the aforementioned Entry 02; the liquid electrolytes are combinations of different amounts of tetraglyme and lithium bis(trifluoromethanesulfonimide) (G 4 and LiTFSI), while the gel electrolytes are combinations of 1:1 G 4 :LiTFSI (termed a solvated ionic liquid, or SIL) and methylcellulose (MC), dubbed "SIL/MC films". The plate of inorganic electrolyte is either bare, or has had a controlled amount of silica (SiO 2 ) deposited onto its faces by way of atomic layer deposition (ALD). Subsequently, as will be seen in the following chapter, this layer is intended to be deposited on the surface of powdered inorganic electrolyte, for the purpose of facilitating covalent attachment of Entry 02. Achievement of this goal requires sufficient understanding of resistance at the organic- inorganic interface, a question that is addressed in this chapter; indeed, a planar geometry configuration allows for a simpler approach to tackling this problem. A systematic study of impedance data by way of an equivalent circuit investigation is undertaken; the main finding of this chapter is that the SiO 2 layer is not detected as a separate impedance feature, instead affecting existing impedance features of the starting components. Additionally, the presence of SiO 2 on the surface of LASPT plates has a positive effect for cyclic voltammetry (CV) and plate-strip experiments, improving the profile of voltammograms in the former case, and lowering the voltage profile while also increasing experiment duration in the latter case. Chapter 5 is the completion of efforts to prepare and characterize polymer- ceramic hybrid electrolytes, by combining the powedered inorganic electrolyte lithium aluminum germanium phosphate (LAGP) with Entry 02. A systematic study impedance data by way of equivalent circuits reveals a distribution of equivalent circuits, which is believed to correspond to a distribution of conduction paths. Plate-strip experiments also indicate that the presence of SiO 2 deposited onto the surface of LAGP particles has a positive effect on both duration and voltage profile. Chapter 6 studies the thermal and electrochemical properties of the cocrystalline electrolyte (the term "cocrystal" will be used interchangeably with "cocrystalline electrolyte") composed of adiponitrile and lithium hexafluorophosphate, (ADN) 2 LiPF 6 . Thermal properties of other cocrystals are also studied for comparison, namely with adiponitrile lithium hexafluoroarsenate (ADN) 2 LiAsF 6 , and adiponitrile lithium hexafluoroantimonate (ADN) 2 LiSbF 6 . In all cases, the cocrystals are found to be formed by high temperature (180 °C) dissolution and crystallization, a reversible phenomenon observed for both cocrystals prepared beforehand, and for raw, stoichiometric mixtures of the cocrystals’ components. Electrochemical characterization of hybrids of LAGP powder and (ADN) 2 LiPF 6 , as well as of (ADN) 2 LiPF 6 , is also performed. For hybrids, it is found from plate-strip experiments that performance is worse than for samples using only (ADN) 2 LiPF 6 , while impedance data shows that overall conductivity drops as the thickness of SiO 2 deposited onto LAGP particles increases. Thermal characterization data reveals that it is possible to quantify the amount of excess ADN present in (ADN) 2 LiPF 6 samples; impedance data indicates that excess ADN improves conductivity of these samples. Conductivity is hypothesized to depend heavily on the presence of a liquid layer, which is present in greater quantities when excess ADN is used – a feature that is believed to be present to a lesser extent when stoichiometric amounts of ADN and LiPF 6 are used. Full cell testing of (ADN) 2 LiPF 6 and saturated solutions of LiPF 6 in ADN reveals that conditioning the cells beforehand is beneficial to long-term cycling, but harmful to short-term discharge rate (C-rate) tests. It is hypothesized that conditioning allows for the formation of an interphase that is conducive to lower current, long-term testing; this interphase however is believed to be resistive in nature, explaining the inferior performance in C-rate tests, when compared to C-rate tests where the conditioning step is omitted. Chapter 7 concludes this work, by providing an overview and an outlook on the results and lessons learned in this work, with the chief lesson being that covalent attachment of an organic component to an inorganic one is a feasible strategy for preparing hybrid electrolytes. / Chemistry

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24635号 / 工博第5141号 / 新制||工||1982(附属図書館) / 京都大学大学院工学研究科分子工学専攻 / (主査)教授 佐藤 啓文, 教授 作花 哲夫, 教授 寺村 謙太郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

Aqueous electrolyte solutions at temperature and pressure conditions near the critical point of water are difficult to describe using traditional equations of state based upon the excess Gibbs energy. Models based upon the residual Helmholtz energy have proven more effective. Anderko and Pitzer1 developed a residual Helmholtz energy model (AP) for aqueous electrolyte solutions in which the electrolyte is assumed to be fully associated. The model has been effectively used in describing densities and vapor-liquid equilibria for simple electrolyte systems. The model is less effective for describing enthalpic properties such as heats of dilution. Oscarson and coworkers2, 3 modified the AP model for NaCl solutions by adding a term accounting for the change in Helmholtz energy as a result of aqueous dissociation reactions. This new model, called the RI model, is more accurate than the AP model at conditions where the NaCl dissociates more fully into ions. Liu et. al4, 5 modified the RI model by adding a term to describe interactions between ions in solution and by regressing new model parameter values. This new model, called the RIII model, is more accurate than both the AP model and the RI model and may be used to predict species concentrations in solution as a result of aqueous phase reactions. The RIII model has substantial thermodynamic inconsistencies, however, and is poorly suited for describing mixed solute solutions. This dissertation presents the RIV model which is an electrolyte solution model for solutions in the ranges of 350 °C to 400 °C and 18 MPa to 40 MPa. The RIV model has been applied to aqueous NaCl solutions and aqueous LiCl solutions. The RIV model is a modification of the AP model and includes aqueous phase reactions implicitly through fundamental species interactions. The RIV model is thermodynamically consistent. It is capable of describing densities and heats of dilution. Density predictions from the RIV model are less accurate than the AP model predictions (6.66 % error vs. 3.51 % error) but are reasonable. The heats of dilution predictions from the RIV model are much more accurate than those from the AP model (25.16 % error vs. 78.78 % error). Predictions of the ionic species concentration from the RIV model are likely to be poor as indicated by the poor agreement between experimental values and calculated values of equilibrium constants valid at infinite dilution. In order to provide the necessary data from which to regress the parameters of the RIV model, experimental heat of dilution values were determined using flow calorimetry techniques. These values are also reported in this dissertation.

Polymer electrolyte membrane fuel cells (PEMFCs) have recently acquired much attention as alternatives to combustion engines for power conversion. The primary interest in fuel cell technology is the possibility of 60% power conversion efficiency as compared to the 30% maximum theoretical efficiency limited to combustion engines and turbines. Although originally conceived to work with hydrogen as a fuel, difficulties relating to hydrogen storage have prompted much effort in using other fuels. Small organic molecules such as alcohols and formic acid have shown promise as alternatives to hydrogen in PEMFCs due to their higher stability at ambient conditions. The drawbacks for using these fuels in PEMFCs are related to their incomplete oxidation mechanisms, which lead to the production of carbon monoxide (CO). When carbon monoxide is released in fuel cells it binds strongly to the platinum anode thus limiting the adsorption and subsequent oxidation of more fuel. In order to promote the complete oxidation of fuels and limit poisoning due to CO, various metal and metal oxide catalysts have been used. Motivated by promising results seen in fuel cell catalysis, this research project is focused on the design and fabrication of novel platinum-composite catalysts for the electrooxidation of methanol, ethanol and formic acid. Various Pt-composites were fabricated including Pt-Au, PtRu, Pt-Pd and Pt-CeO2 catalysts. Electrochemical techniques were used to determine the catalytic ability of each novel composite toward the electrooxidation of methanol, ethanol and formic acid. This study indicates that the novel composites all have higher catalytic ability than bare Pt electrodes. The increase in catalytic ability is mostly attributed to the increase in CO poison tolerance and promotion of the complete oxidation mechanism of methanol, ethanol and iv formic acid. Formulations including bi- and tri-composite catalysts were fabricated and in many cases show the highest catalytic oxidation, suggesting tertiary catalytic effects. The combination of bi-metallic composites with ceria also showed highly increased catalytic oxidation ability. The following dissertation expounds on the relationship between composite material and the electrooxidation of methanol, ethanol and formic acid. The full electrochemical and material characterization of each composite electrode is provided.

The first part of the study deals with the preparation of carbon nanotube/polymer nanocomposite materials. The dispersion of multi-walled carbon nanotubes (MWNTs) using trifluoroacetic acid (TFA) as a co-solvent and its subsequent use in polymer nanocomposite fabrication is reported. The use of carbon nanotube/ polymer nanocomposite system for the fabrication of organic solar cells is also studied. TFA is a strong but volatile acid which is miscible with many commonly used organic solvents. Our study demonstrates that MWNTs can be effectively purified and readily dispersed in a range of organic solvents including dimethyl formamide (DMF), tetrahydrofuran (THF), and dichloromethane when mixed with 10 vol% trifluoroacetic acid (TFA). X-ray photoelectron spectroscopic analysis revealed that the chemical structure of the TFA-treated MWNTs remained intact without oxidation. The dispersed carbon nanotubes in TFA/THF solution were mixed with poly(methyl methacrylate) (PMMA) to fabricate polymer nanocomposites. A good dispersion of nanotubes in solution and in polymer matrices was observed and confirmed by SEM and optical microscopy study. Low percolation thresholds of electrical conductivity were observed from the fabricated MWNT/PMMA composite films. A carbon nanotube/ polymer nanocomposites system was also used for the fabrication of organic solar cells. A blend of single-wall carbon nanotubes (SWNTs) and poly3-hexylthiophene (P3HT) was used as the active layer in the device. The device characteristics showed that the fabrication of the solar cells was successful without any shorts in the circuit. The second part of the study deals with the preparation and characterization of electrode and electrolyte materials for lithium ion batteries. A system of lithium trifluoroacetate/ PMMA was used for its study as the electrolyte in lithium battery. A variety of different processing conditions were used to prepare the polymer electrolyte system. The conductivity of the electrolyte plays a critical role in the high power output of a battery. A high power output requires fast transport of lithium ions for which the conductivity of the electrolyte must be at least 3 x 10^-4 S/cm. Electrochemical Impedance Spectroscopy (EIS) was used to determine the conductivity of the polymer electrolyte films. Among the different processing conditions used to prepare the polymer electrolyte material, wet films of PMMA/salt system prepared by using 10vol% of TFA in THF showed the best results. At about 70wt% loading of the salt in the polymer, the conductivity obtained was about 1.1 x 10^-2 S/cm. Recently, the use of vanadium oxide material as intercalation host for lithium has gained widespread attention. Sol-gel derived vanadium oxide films were prepared and its use as a cathode material for lithium ion battery was studied. The application of carbon nanotubes in lithium ion battery was explored. A carbon nanotube /block copolymer (P3HT-b-PS) composite was prepared and its potential as an anode material was evaluated.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第24644号 / 工博第5150号 / 新制||工||1983(附属図書館) / 京都大学大学院工学研究科化学工学専攻 / (主査)教授 河瀬 元明, 准教授 中川 浩行, 教授 外輪 健一郎 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

The majority of this dissertation focuses on proton conducting materials that could be used at high operating temperatures. Higher operating temperatures are desirable as they will increase fuel cell efficiency, reduce cost, and simplify the heat management system. The factors governing proton conduction including segmental mobility, protogenic group identity, and charge carrier density were investigated on a variety of polymers containing 1H-1,2,3-triazole moieties. Proton conductivity measurements were made using AC impedance spectroscopy. Random copolymers and terpolymers of triazole-containing acrylates and poly(ethylene glycol)methyl ether acrylate (PEGMEA) have been synthesized. Conductivity increased with increasing degree of PEG incorporation until reaching a maximum at 30% mole PEGMEA. In comparison to benzimidazole-functionalized polyacrylate with 35% mole PEGMEA, the triazole analog showed a higher proton conductivity, and a less pronounced conductivity temperature dependence. Further increases in conductivity was achieved through the addition of trifluoroacetic acid. To study the effect of charge carrier density on proton conduction, polyacrylates containing a different number of triazole groups per repeat unit were synthesized. The result showed that introduction of more than one triazole per repeat unit did not result in an increase in conductivity as there was an accompanying increase in Tg. To improve the thermal and mechanical properties, triazole groups were tethered to a higher Tg backbone polymer, polynorbornene. Introduction of polyhedral oligomeric silsesquioxane (POSS) into triazole-functionalized polynorbornene was also investigated. In a parallel set of investigations, poly(2-(dimethylamino)ethyl methacrylate), PDMAEMA, and copolymers of DMAEMA and methyl methacrylate (PDMAEMA-co-PMMA) were synthesized via atom transfer radical polymerization (ATRP). Fluorescently-labeled PDMAEMAs were synthesized using fluorescent ATRP initiators to ensure the presence of one dye molecule on every polymer chain. PDMAEMAs and PDMAEMA-co-PMMA with different molecular weights have been deposited onto a negatively-charged silica surface via controlled flow deposition. The results show that the polymer deposition rate depends on molecular weight, and is inversely proportional to molecular weight. A preliminary adhesion study of 1-μm negatively charged silica spheres onto these functionalized surfaces indicates that by varying the molecular weight, the adhesion threshold can be changed. System modeling is being conducted to support experimental observations.

Anhydrous proton conducting polymers are highly sought after for applications in high temperature polymer electrolyte membrane fuel cells (PEMFCs). N-heterocycles (eg. imidazole, triazole, and benzimidazole), owing to their amphoteric nature, have been widely studied to develop efficient anhydrous proton transporting polymers. The proton conductivity of N-heterocyclic polymers is influenced by several factors and the design and development of polymers with a delicate balance among various synergistic and competing factors to provide appreciable proton conductivities has been a challenging task. In this thesis, the proton transport (PT) characteristics of polymers functionalized with two diverse classes of functional groups - N-heterocycles and phenols have been investigated and efforts have been made to develop the molecular design criteria for the design and development of efficient proton transporting functional groups and polymers. The proton conduction pathway in 1H-1,2,3-triazole polymers is probed by employing structurally analogous N-heterocyclic (triazole, imidazole, and pyrazole) and benz-N-heterocyclic (benzotriazole, benzimidazole, and benzopyrazole) polymers. Imidazole-like pathway was found to dominate the proton conductivity of triazole and pyrazole-like pathway makes only a negligible contribution, if any. Polymers containing benz-N-heterocycles exhibited higher proton conductivity than those with the corresponding N-heterocycles. Pyrazole-like functional groups, i.e. the molecules with two nitrogen atoms adjacent to each other, were found not to be good candidates for PT applications. A new class of proton transporting functional groups, phenols, has been introduced for anhydrous PT. One of the highlighting features of phenols over N-heterocycles is that the hydrogen bond donor/acceptor reorientation can happen on a single -OH site, allowing for facile reorientational dynamics in Grotthuss PT and enhanced proton conductivities in phenolic polymers. Unlike the case of N-heterocycles, comparable conductivities were achieved between poly (3,4,5-trihydroxy) styrene and the corresponding small molecule, pyrogallol. This observation suggests that reorientation should be considered as a crucial design parameter for PT functional groups. The PT characteristics of phenol-based biaryl polymers are studied and compared with the analogous phenol-based linear styrenic polymers. The two-dimensional disposition of -OH moieties in biaryl polymers, although resulted in lower apparent activation energies (Ea), did not improve the net proton conductivity due to the accompanying increase in glass transition temperature (Tg). Thus, the ease of synthesis and lower Tg values of phenol-based styrene polymers make the styrenic polymer architecture preferable over the biaryl architecture. Finally, the synthesis of a series of poly(3,4-dihydroxy styrene)-b-polystyrene block copolymers has been demonstrated via anionic polymerization. These block copolymers will provide an opportunity to systematically investigate the effect of nanoscale morphology on proton transport.

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