京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第21787号 / 工博第4604号 / 新制||工||1717(附属図書館) / 京都大学大学院工学研究科物質エネルギー化学専攻 / (主査)教授 安部 武志, 教授 作花 哲夫, 教授 阿部 竜 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DGAM

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Many material properties depend on specific details of microstructure and both optimal material performance and material reliability often correlate directly to microstructure. In nano- and micro-systems, the material's microstructure has a characteristic length scale that approaches that of the device in which it is used. Fundamental understanding and prediction of material behavior in nano- and micro-systems depend critically on methods for computing the effect of microstructure. Methods for including the physics and spatial attributes of microstructures are presented for a number of materials applications in devices. The research in our group includes applications of computation of macroscopic response of material microstructures, the development of methods for calculating microstructural evolution, and the morphological stability of structures. In this review, research highlights are presented for particular methods for computing the response in: 1) rechargeable lithium ion battery microstructures, 2) photonic composites with anisotropic particulate morphologies, 3) crack deflection in partially devitrified metallic glasses. / Singapore-MIT Alliance (SMA)

This thesis is concerned with kinetic characterisation of theinsertion compound LiMn2O4, which is used as positive electrodematerial in rechargeable lithium batteries. Three different typesof electrode configurations have been investigated, namely singleparticles, thin films and composite electrodes. Differentelectrochemical techniques, i.e. linear sweep voltammetry (LSV),electrochemical impedance spectroscopy (EIS), potential step, andgalvanostatic experiments were applied under various experimentalconditions. The majority of the experimental data were analysedby relevant mathematical models used for describing the reactionsteps of insertion compounds. It was concluded that a model based on interfacialcharge-transfer, solid-phase diffusion and an external iR-dropcould be fairly well fitted to LSV data measured on a singleelectrode system over a narrow range of sweep rates. However, itwas also found that the fitted parameter values vary greatly withthe characteristic length and the sweep rate. This indicates thatthe physical description used is too simple for explaining theelectrochemical responses measured over a large range of chargeand discharge rates. EIS was found to be a well-suited technique for separatingtime constants for different physical processes in the insertionand extraction reaction. It was demonstrated that the impedanceresponse is strongly dependent on the current collector used.According to the literature, reasonable values of theexchange-current density and solid-phase diffusion coefficientwere determined for various states-of-discharge, temperatures andelectrolyte compositions. Experiments were carried out in bothliquid and gel electrolytes. A method which improves thedistinction between the time constants related to thematerial’s intrinsic properties and possible porous effectsis presented. The method was applied to composite electrodes.This method utilises, in addition to the impedance responsemeasured in front of the electrode, also the impedance measuredat the backside of the electrode. Finally, the kinetics of a composite electrode was alsoinvestigated by in situ X-ray diffraction (in situ XRD) incombination with galvanostatic and potentiostatic experiments. Noevidence of lithium concentration gradients could be observedfrom XRD data, even at the highest rate applied (i.e. ~6C), thusexcluding solid-phase diffusion and also phase-boundary movement,as described by Fick’s law, as the ratelimiting step. <b>Key words:</b>linear sweep voltammetry, electrochemicalimpedance spectroscopy, potential step, in situ X-raydiffraction, microelectrodes, electrode kinetics, LiMn2O4cathode, rechargeable lithium batteries

Room temperature molten liquids are proposed to be good alternates for volatile and harmful organic compounds. They are useful in varied areas of applications ranging from synthesis, catalysis to energy storage molten electrolytes have certain unique characteristics such as low vapour pressure, reasonably high ionic conductivity, high thermal stability and wide electrochemical window. These molten liquids can be classified in to two types depending on the nature of the species present in the liquids. One, those liquids consists only of ions (e.g) conventional imidazolium based ionic liquids and other that consists of ions and solvents (e g) acetamide eutectics. Acetamide and its eutectics from room temperature molten solvents that is unique with interesting physicochemical properties. The solvent properties of molten acetamide are similar to water, with high dielectric consist of 60 at 353 k. its acid – base properties are also similar to water, and it can solublise variety of organic and inorganic compounds as well. in the present studies room temperature molten liquids consisting of acetamide as one of the components have been prepared and used for various applications. Room temperature molten electrolytes consisting of magnesium perchlorate/magnesium triflate as one of the constituents have been used for rechargeable magnesium batteries where as those consisting of zinc perchlorate /zinc triflate have been used for zinc based rechargeable batteries. Full utilization of cathode material (y-mno2) is achieved using amide-based molten liquid as electrolyte in rechargeable zinc based batteries. Ammonium nitrate/ lithium nitrate containing electrolytes have been used for electrochemical super capacitors. They have been used as solvent cum stabilizers for metallic nanochains that can be used as substrate in surface enchanced Raman scattering studies.

<p>This thesis is concerned with kinetic characterisation of theinsertion compound LiMn2O4, which is used as positive electrodematerial in rechargeable lithium batteries. Three different typesof electrode configurations have been investigated, namely singleparticles, thin films and composite electrodes. Differentelectrochemical techniques, i.e. linear sweep voltammetry (LSV),electrochemical impedance spectroscopy (EIS), potential step, andgalvanostatic experiments were applied under various experimentalconditions. The majority of the experimental data were analysedby relevant mathematical models used for describing the reactionsteps of insertion compounds.</p><p>It was concluded that a model based on interfacialcharge-transfer, solid-phase diffusion and an external iR-dropcould be fairly well fitted to LSV data measured on a singleelectrode system over a narrow range of sweep rates. However, itwas also found that the fitted parameter values vary greatly withthe characteristic length and the sweep rate. This indicates thatthe physical description used is too simple for explaining theelectrochemical responses measured over a large range of chargeand discharge rates.</p><p>EIS was found to be a well-suited technique for separatingtime constants for different physical processes in the insertionand extraction reaction. It was demonstrated that the impedanceresponse is strongly dependent on the current collector used.According to the literature, reasonable values of theexchange-current density and solid-phase diffusion coefficientwere determined for various states-of-discharge, temperatures andelectrolyte compositions. Experiments were carried out in bothliquid and gel electrolytes. A method which improves thedistinction between the time constants related to thematerial’s intrinsic properties and possible porous effectsis presented. The method was applied to composite electrodes.This method utilises, in addition to the impedance responsemeasured in front of the electrode, also the impedance measuredat the backside of the electrode.</p><p>Finally, the kinetics of a composite electrode was alsoinvestigated by in situ X-ray diffraction (in situ XRD) incombination with galvanostatic and potentiostatic experiments. Noevidence of lithium concentration gradients could be observedfrom XRD data, even at the highest rate applied (i.e. ~6C), thusexcluding solid-phase diffusion and also phase-boundary movement,as described by Fick’s law, as the ratelimiting step.</p><p><b>Key words:</b>linear sweep voltammetry, electrochemicalimpedance spectroscopy, potential step, in situ X-raydiffraction, microelectrodes, electrode kinetics, LiMn2O4cathode, rechargeable lithium batteries</p>

This thesis studies the performance of solid polymer lithium batteries from room temperature to elevated temperatures using mainly electrochemical techniques, with emphasis on the bulk properties of the polymer electrolyte and the electrode-electrolyte interfaces. Its contributions include: 1) Demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence, and improved the conductivity of the graft copolymer electrolyte (GCE) by almost an order of magnitude by changing the ion-conducting block from poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature \((T_g)\) poly(oxyethylene) acrylate (POEA). 2) Identified the rate-limiting step in the battery occurs at the cathode-electrolyte interface using both full cell and symmetric cell electrochemical impedance spectroscopy (EIS), improved the battery rate capability by using the GCE as both the electrolyte and the cathode binder to reduce the resistance at the cathode-electrolyte interface, and used TEM and SEM to visualize the polymer-particle interface (full cells with \(LiFePO_4\) as the cathode active material and lithium metal as the anode were assembled and tested). 3) Applied the solid polymer battery to oil and gas drilling application, performed high temperature (up to 210°C) cycling (both isothermal and thermal cycling), and demonstrated for the first time, current exchange between a solid polymer electrolyte and a liquid lithium metal. Both the cell open-circuit-voltage (OCV) and the overall GCE mass remained stable up to 200°C, suggesting that the GCE is electrochemically and gravimetrically stable at high temperatures. Used full cell EIS to study the behavior of the various battery parameters as a function of cycling and temperature. 4) Identified the thermal instability of the cell was due to the reactivity of lithium metal and its passivation film at high temperatures, and used Li/GCE/Li symmetric cell EIS to study the thermal stability of the anode-electrolyte interface, which was responsible for the fast capacity fade observed at high temperatures. 5) Proposed a new electrolyte material and a new battery design called polymer ionic liquid (PIL) battery that can dramatically improve the safety, energy density, and rate capability of rechargeable lithium batteries. / Engineering and Applied Sciences

Binder free vertical aligned (VA) CNT/sulfur composite electrodes with high sulfur loadings up to 70 wt% were synthesized delivering discharge capacities higher than 800 mAh g−1 of the total composite electrode mass. / Dieser Beitrag ist mit Zustimmung des Rechteinhabers aufgrund einer (DFG-geförderten) Allianz- bzw. Nationallizenz frei zugänglich.

L'augmentation des densités de puissance et d'énergie des SSE (système de stockage électrique) des véhicules électriques/véhicules hybrides rechargeable (VEs/VHRs), tout en conservant des coûts raisonnables pour l'utilisateur, et le développement de convertisseurs d'énergie électrique à haute densité de puissance volumique, et de plus en plus performant vont favoriser la production en masse de véhicules électrifiés. Une partie de ces véhicules électriques (VEs/VHRs) nécessitent une connexion au réseau pour la recharge des batteries. L’insertion de ces nouvelles charges dans le réseau présentera alors plusieurs enjeux et impacts significatifs pour les réseaux électriques puisqu’ils doivent répondre localement à des demandes de puissance non négligeables. Ce projet de thèse vise à étudier et réduire les impacts des VEs/VHRs sur les réseaux de distribution grâce à la technologie Vehicle-to-Grid (V2G). Le véhicule électrique alimente le réseau en fonction des besoins du système électrique (modèle bidirectionnel) et lui offre un service de flexibilité. Ces travaux de recherche ont pour but d'approfondir les concepts dans lequel l’alimentation des véhicules électriques (VE) et/ou hybrides de type P-VEH est intégrée à la gestion du réseau de distribution et des « hubs énergétiques » du futur. L’objectif de la thèse est d’abord étudier les service systèmes possible à fournir grâce à V2G, ensuite de concevoir un système de supervision qui assurera une gestion énergétique de ces nouvelles charges en choisissant le mode de recharge et/ou décharge adéquat et en prenant également en considération la demande de consommation locale et la présence de production de type renouvelable (photovoltaïque, éolien) dans le réseau de distribution. Cette supervision se fera dans un premier temps « en hors ligne » et par la suite « en ligne ». On aura recours à l’utilisation de méthodes d’intelligence artificielle comme l’apprentissage automatique (Machine Learning) et la logique floue, la commande prédictive ainsi que des méthodes d’optimisation hybrides (stochastiques et déterministes). / The power and energy density increment of the electrical storage system (ESS) of electric vehicles/Plug-in hybrid electric vehicles (EVs/PHEVs), while maintaining reasonable costs for the user, and the development of converters of electrical energy to high power density and more and more powerful, will encourage the mass production of electrified vehicles. Beyond, electric vehicles (EVs/PHEVs) require a connection to the grid for the charging of the batteries. The insertion of these new loads in the grid will then present several issues and significant impacts for electrical networks since they must respond locally to non-negligible power requests. This PhD thesis aims to study and reduce the impacts of the EVs/PHEVs on the distribution grid thanks to the vehicle-to-Grid (V2G) technology. The electric vehicle supplies the grid depending on the needs of the electrical system (bi-directional model) and offers a flexible service. These works of research have aimed to deepen the concepts in which the supply of electric vehicles (EV) and/or hybrids of type PHEV is integrated with the management of the distribution network and the future "energy hubs". The objective of the thesis is at first to examine the possible ancillary services provided by V2G, then to design a system of supervision which will ensure an energy management of these new loads by choosing the adequate mode of charge/discharge and also taking into consideration the request of local consumption and the presence of renewable production of type photovoltaic and wind in the distribution grid. This supervision will be in a first step "offline" and subsequently "online". The methods which are used in this thesis are as follows; artificial intelligence such as machine learning and fuzzy logic, the predictive control as well as the methods of hybrids optimization (stochastic and deterministic).

This thesis deals with novel electrolytes for magnesium batteries. Prepared electrolytes were composed of affordable solvents and chemicals, which can be handled at normal laboratory conditions. Specifically, solutions of tetrahydrofurane and dimethylsulfoxide with magnesium chloride, aluminium chloride, nitrilotriacetic acid and disodium ethylenediaminetetraacetic acid, were prepared. To determine electrolyte ability of magnesium stripping and deposition, the cyclic voltammetry was used. The kinetics of electrochemical reactions in terms of polarization resistance was studied by electrochemical impedance spectroscopy. Based on scanning electron microscopy and EDS analysis, the effect of atmospheric oxygen and humidity on magnesium electrode corrosion during cycling was discussed.