<p>Li-ion batteries are not only a technology for the future, they are indeed already the technology of choice for today’s mobile phones, laptops and cordless power tools. Their ability to provide high energy densities inexpensively and in a way which conforms to modern environmental standards is constantly opening up new markets for these batteries. To be able to maintain this trend, it is imperative that all issues which relate safety to performance be studied in the greatest detail. The surface chemistry of the electrode-electrolyte interfaces is intrinsically crucial to Li-ion battery performance and safety. Unfortunately, the reactions occurring at these interfaces are still poorly understood. The aim of this thesis is therefore to increase our understanding of the surface chemistries and stability phenomena at the electrode-electrolyte interfaces for three novel Li-ion battery electrode materials.</p><p>Photoelectron spectroscopy has been used to study the surface chemistry of the anode material AlSb and the cathode materials LiFePO₄ and Li₂FeSiO₄. The cathode materials were both carbon-coated to improve inter-particle contact. The surface chemistry of these electrodes has been investigated in relation to their electrochemical performance and X-ray diffraction obtained structural results. Surface film formation and degradation reactions are also discussed.</p><p>For AlSb, it has been shown that most of the surface layer deposition occurs between 0.50 and 0.01 V <i>vs.</i> Li°/Li⁺ and that cycling performance improves when the lower cut-off potential of 0.50 V is used instead of 0.01 V. For both LiFePO₄ and Li₂FeSiO₄, the surface layer has been found to be very thin and does not provide complete surface coverage. Li₂CO₃ was also found on the surface of Li₂FeSiO₄ on exposure to air; this was found to disappear from the surface in a PC-based electrolyte. These results combine to give the promise of good long-term cycling with increased performance and safety for all three electrode materials studied.</p>

Li-ion batteries are not only a technology for the future, they are indeed already the technology of choice for today’s mobile phones, laptops and cordless power tools. Their ability to provide high energy densities inexpensively and in a way which conforms to modern environmental standards is constantly opening up new markets for these batteries. To be able to maintain this trend, it is imperative that all issues which relate safety to performance be studied in the greatest detail. The surface chemistry of the electrode-electrolyte interfaces is intrinsically crucial to Li-ion battery performance and safety. Unfortunately, the reactions occurring at these interfaces are still poorly understood. The aim of this thesis is therefore to increase our understanding of the surface chemistries and stability phenomena at the electrode-electrolyte interfaces for three novel Li-ion battery electrode materials. Photoelectron spectroscopy has been used to study the surface chemistry of the anode material AlSb and the cathode materials LiFePO4 and Li2FeSiO4. The cathode materials were both carbon-coated to improve inter-particle contact. The surface chemistry of these electrodes has been investigated in relation to their electrochemical performance and X-ray diffraction obtained structural results. Surface film formation and degradation reactions are also discussed. For AlSb, it has been shown that most of the surface layer deposition occurs between 0.50 and 0.01 V vs. Li°/Li+ and that cycling performance improves when the lower cut-off potential of 0.50 V is used instead of 0.01 V. For both LiFePO4 and Li2FeSiO4, the surface layer has been found to be very thin and does not provide complete surface coverage. Li2CO3 was also found on the surface of Li2FeSiO4 on exposure to air; this was found to disappear from the surface in a PC-based electrolyte. These results combine to give the promise of good long-term cycling with increased performance and safety for all three electrode materials studied.

The research presented is based on alternative anode materials for high temperature steam electrolysis. The key to commercially viable renewable energy economy is based on energy storage of intermittent sources. Hydrogen is the preferred form of energy storage for solid oxide electrolysis cells. However, conventional anode material lanthanum strontium manganite (LSM), suffers from poor ionic conductivity, thus prohibiting much of the bulk electrode from providing an enhanced electrochemical performance. This study explores the use of a double-layered perovskite system with mixed electronic and ionic conductivity for use as anode material. Specifically, the SmBa₁₋ₓSrₓCo₂O[sub](5+δ) system (SBSCO) is analyzed for characteristics that may enhance the performance and feasibility of SBSCO as an alternative anode material to LSM. Previous in-house work showed SmBa₀.₅Sr₀.₅Co₂O[sub](5+δ) had the lowest area specific resistance of any double- layered material reported. Here the system is further explored by studying the full range of compositions. From X-ray diffraction analysis, increased Sr substitution leads to a tetragonal phase change in SBSCO. High temperature x-ray diffraction of compositions showed thermal stability of structure. Magnetization measurements are reported for selected compositions. The stability of SBSCO was examined in CO₂ containing atmospheres. Despite containing alkaline earth metals, the system offers limited CO₂ tolerance. A set of thermodynamic parameters is presented based on CO₂ partial pressure and temperature. Model indicates SBSCO is a stable electrode material for both electrolysis and fuel cell modes. Compositions were tested for steam electrolysis performance with the use of YSZ electrolyte, and Ni-YSZ and La₀.₄Sr₀.₄Ni₀.₀₆Ti₀.₉₄O₂.₉₄ cathodes. SmBa₀.₃Sr₀.₇Co₂O[sub](5+δ) had the highest performance for compositions (0≤x≤1) based on I-V curves and impedance measurements. Stability tests were conducted in potentiostatic mode and no delamination was observed for SBSCO in microstructural analysis after testing. From these studies, SBSCO is demonstrated to be a suitable for application in electrolysis and an alternative for LSM as anode material.

La forte progression démographique mondiale induit une demande d’énergietoujours en hausse. Ceci se traduit par un fort développement de nouvelles énergiesrenouvelables qui nécessitent, de par leur nature intermittente, des dispositifs de stockagede l’énergie. Parmi eux les supercondensateurs permettent un stockage électrostatique decharges (supercondensateurs à base de carbones activés), mais certains systèmes, ditspseudocapacitifs, font en outre intervenir des réactions redox rapides de surface.L’association des deux systèmes permettent d’accéder à des propriétés intéressantes, enparticulier pour le système MnO2/carbone activé. Cependant, les oxydes de manganèse sontd’excellents matériaux pseudocapacitifs mais assez peu conducteurs électroniques.L’objectif de ce travail est d’améliorer cette conductivité en les associant avec des oxydes decobalt conducteurs. Pour cela, une approche « architecturale » de synthèse de matériaux aété choisie. En partant d’oxydes de Mn et de Co lamellaires, ceux-ci sont exfoliés pourobtenir des nanofeuillets de nature différente. S’ensuit une étape de réempilement pouraboutir à un matériau lamellaire alterné. L’analyse structurale et morphologique desmatériaux prouve que des nanocomposites très finement divisés sont obtenus. Lespropriétés électrochimiques obtenues pour ces nanocomposites s’avèrent meilleures quecelles des matériaux initiaux, tant en densité d’énergie qu’en puissance. Cette stratégieoriginale est prometteuse et ouvre la voie à des réempilements de différente nature,notamment le graphène. / The ever increasing demand of renewable energies imposes, due to theirintermittent nature, the development of performant energy storage devices. Supercapacitorsare reliable devices that offer a high power density and numerous investigations are focusingon increasing their energy densities. In particular, asymmetric "metal oxides / activatedcarbons" supercapacitors are possible candidates. The MnO2/carbon system is the mostinvestigated system, due to its capability to work in aqueous medium at potentials up to 2 V,as well as to the low cost and environmental friendliness of manganese. Nevertheless, thissystem suffers from the poor electronic conductivity of manganese. This work reports anoriginal strategy for novel electrode materials involving exfoliation and restacking processesof lamellar “building blocks”: lamellar manganese oxides for their pseudocapacitiveproperties and lamellar cobalt oxyhydroxides for their high electronic conductivity. Thematerial engineering strategy focuses on the exfoliation of the lamellar materials intooligolamellae. The obtained suspensions are then restacked through various strategies andnew well defined mixed oxides are obtained. After structural and morphologicalcharacterization, it is clear that these nanocomposites present an intimate mix of the twoinitial phases. The electrochemical responses are hereby enhanced, proving the intertwinedrelationship between structure, morphology and properties. Furthermore, this architecturalapproach of building novel electrode materials is original and efficient and can easily betransposed to other “building blocks”, including graphene.

Ce mémoire est consacré à l’étude des composites à base de phosphates de type NASICON comme matériaux d’électrode pour batteries sodium-ion : Na1+xFexTi2-x(PO4)3/C et Na1+xFexSn2-x(PO4)3/C avec 0 ≤ x ≤ 1. Ces composites ont été synthétisés par voie solide suivie d’une pyrolyse avec le saccharose. Ils sont constitués de particules ayant une porosité élevée et enrobées par du carbone conférant à l’électrode une bonne conductivité ionique et électronique. Les mécanismes réactionnels se produisant lors des cycles de charge-décharge ont été analysés en mode operando par diffraction des rayons X, spectroscopies Mössbauer du 57Fe et de 119Sn et spectroscopie d’absorption X. Pour les composites fer-titane, ces mécanismes sont essentiellement basés sur la diffusion des ions Na+ dans les canaux des phases cristallisées avec changements d’état d’oxydation des métaux. Pour les composites fer-étain, les mécanismes sont plus complexes incluant insertion, conversion conduisant à la destruction des phases NASICON, puis formation d’alliages NaxSn. Les meilleures performances électrochimiques ont été obtenues pour Na1,5Fe0,5Ti1,5(PO4)3/C avec un potentiel de fonctionnement de 2,2 V vs Na+/Na0. Même si ces deux familles de matériaux peuvent être utilisées à plus bas potentiel, les performances doivent être améliorées pour envisager leur application comme électrode négative. / This thesis is devoted to the study of phosphate based composites with NASICON type structure, that are used as electrode materials for sodium-ion batteries: Na1+xFexTi2-x (PO4)3/C et Na1+xFexSn2-x(PO4)3/C with 0 ≤ x ≤ 1. These composites were synthesized by solid state route followed by a pyrolysis reaction with sucrose. They consist of particles having high porosity and coated with carbon giving to the electrode good ionic and electronic conductivity. The reaction mechanisms occurring during charge-discharge cycles were analyzed in operando mode, by X-ray diffraction, 57Fe and 119Sn Mössbauer spectroscopies and X-ray absorption spectroscopy. For the iron-titanium composites, the mechanisms are essentially based on the diffusion of Na+ in the channels of the crystalline phases with changes of transition metal oxidation state. For iron-tin composites, the mechanisms are more complex including insertion, conversion leading to the destruction of the NASICON phases and then reversible formation of NaxSn alloys. The best electrochemical performances were obtained for Na1,5Fe0,5Ti1,5(PO4)3/C with an operating potential of 2.2 V vs. Na+/Na0. Although these two types of materials can be used at lower potential, the performances must be improved to consider their application as the negative electrode.

Organic electrode materials represent an intriguing alternative to their inorganic counterparts due to their sustainable and environmental-friendly properties. Their plastic character allows for the realization of light-weight, versatile and disposable devices for energy storage. Conducting redox polymers (CRPs) are one type of the organic electrode materials involved, which consist of a π-conjugated polymer backbone and covalently attached redox units, the so-called pendant. The polymer backbone can provide conductivity while it is oxidized or reduced (i. e., p- or n-doped) and the concurrent redox chemistry of the pendant provides charge capacity. The combination of these two components enables CRPs to provide both high charge capacity and high power capability. This dyad polymeric framework provides a solution to the two main problems associated with organic electrode materials based on small molecules: the dissolution of the active material in the electrolyte, and the sluggish charge transport within the material. This thesis introduces a general synthetic strategy to obtain the monomeric CRPs building blocks, followed by electrochemical polymerization to afford the active CRPs material. The choice of pendant and of polymer backbone depends on the potential match between these two components, i.e. the redox reaction of the pendant and the doping of backbone occurring within the same potential region. In the thesis, terephthalate and polythiophene were selected as the pendant and polymer backbone respectively, to get access to low potential CRPs. It was found that the presence of a non-conjugated linker between polymer backbone and pendant is essential for the polymerizability of the monomers as well as for the preservation of individual redox activities. The resulting CRPs exhibited fast charge transport within the polymer film and low activation barriers for charge propagation. These low potential CRPs were designed as the anode materials for energy storage applications. The combination of redox active pendant as charge carrier and a conductive polymer backbone reveals new insights into the requirements of organic matter based electrical energy storage materials.

The dissertation thesis deals with electrode materials and components for lithium-ion power sources. The thesis works with two different kinds of materials, concretely nanostructured Li4Ti5O12 with spinel basis and LiCoO2 with layered structure. The electrochemical properties, structure and element analysis and utilization possibilities in electrochemical industry of new technological electrode material Li4Ti5O12 were investigated. The influences of admixtures and electrolytes on characteristics of electrode materials with aforesaid active masses were also examined. Low cost price, environmental safety and obtained results of electrochemical measurements and structure analysis refer to wide possibilities of usage electrode material Li4Ti5O12 in the field of electrochemistry.

This article presents a facile and effective approach for synthesizing three-dimensional (3D) graphenecoupled Schiff-base hierarchically porous polymers (GS-HPPs). The method involves the polymerization of melamine and 1,4-phthalaldehyde, yielding Schiff-base porous polymers on the interconnected macroporous frameworks of 3D graphene aerogels. The as-synthesized GS-HPPs possess hierarchically porous structures containing macro-/meso-/micropores, along with large specific surface areas up to 776 m² g⁻¹ and high nitrogen contents up to 36.8 wt%. Consequently, 3D nitrogen-enriched hierarchically porous carbon (N-HPC) materials with macro-/meso-/micropores were obtained by the pyrolysis of the GS-HPPs at a high temperature of 800 °C under a nitrogen atmosphere. With a hierarchically porous structure, good thermal stability and a high nitrogen-doping content up to 7.2 wt%, the N-HPC samples show a high specific capacitance of 335 F g⁻¹ at 0.1 A g⁻¹ in 6 M KOH, a good capacitance retention with increasing current density, and an outstanding cycling stability. The superior electrochemical performance means that the N-HPC materials have great potential as electrode materials for supercapacitors.

京都大学 / 0048 / 新制・課程博士 / 博士(エネルギー科学) / 甲第18607号 / エネ博第303号 / 新制||エネ||62(附属図書館) / 31507 / 京都大学大学院エネルギー科学研究科エネルギー基礎科学専攻 / (主査)教授 萩原 理加, 教授 佐川 尚, 教授 平藤 哲司 / 学位規則第4条第1項該当 / Doctor of Energy Science / Kyoto University / DFAM

Elektrochemische Energiespeicher sind entscheidend für eine zuverlässige Energieversorgung angesichts steigender Nachfrage und knapper Ressourcen. Die fortlaufende Entwicklung möglichst umweltfreundlicher Materialien mit guter Verfügbarkeit ist essenziell für die Verbesserung von deren Leistungsfähigkeit. Ziel der Arbeit war die Nutzung cellulosebasierter Präkursoren zur Herstellung von Elektrodenmaterialien für die elektrochemischen Energiespeicher Superkondensator und Li-Ionen-Batterie. Dabei werden die Struktur-Eigenschaftsbeziehungen von Präkursormaterial und Kohlenstoff, sowie deren Einfluss auf die resultierenden elektrochemischen Leistungen untersucht. Mittels Acetatverfahren können sphärische Partikel auf Basis von Cellulose mit einer Partikelgröße < 5 µm und enger Partikelgrößenverteilung hergestellt werden. Bei der Herstellung sphärischer Partikel aus Celluloseacetat werden eine Vielzahl verschiedener Parameter im Herstellungsprozess variiert und deren Einfluss auf die Eigenschaften der sphärischen Partikel verändert. Außerdem werden die Cellulosederivate Celluloseacetat-butyrat und Celluloseacetat-phthalat als Ausgangsmaterial zur Herstellung sphärischer Partikel verwendet. Die hergestellten sphärischen Partikel werden mittels Pyrolyse zu Kohlenstoff umgewandelt, wobei zum einen der Einfluss der Eigenschaften der sphärischen Präkursoren auf die resultierenden Kohlenstoffe und zum anderen der Einfluss verschiedener Carbonisierungsbedingungen (Carbonisierungstemperatur, Haltezeit, Heizrate) anhand von sphärischen Celluloseacetatpartikeln mit einer Partikelgröße < 5 µm untersucht werden. Zur Vergrößerung der Oberfläche und zur Veränderung der Porenstruktur werden aktivierte Kohlenstoffe hergestellt. Dabei wird KOH in verschiedenen Aktivierungsgraden C : KOH verwendet sowie alternative Aktivierungsreagenzien getestet. Die (aktivierten) Kohlenstoffe dienen als Elektrodenmaterialien in Superkondensatoren, Li-Ionen-Batterien und Li-Ionen-Kondensatoren. Die hergestellten Kohlenstoffe zeigen vielversprechende Kapazitäten als Elektrodenmaterial in symmetrischen Superkondensatoren mit KOH-Elektrolytlösung, insbesondere bei Verwendung von aktiviertem Kohlenstoff aus sphärischen Celluloseacetatpartikeln. Außerdem werden verschiedene neutrale wässrige Elektrolytlösungen als Alternative zu alkalischen KOH-Lösungen getestet und der Einfluss von Konzentration und Arbeitstemperatur betrachtet. Weiterhin kann die Eignung der hergestellten nicht-aktivierten Kohlenstoffe aus Celluloseacetat-Perlen als Anodenmaterial in Lithium-Ionen-Batterien als Alternative zu Graphit gezeigt werden, insbesondere hinsichtlich Langzeitstabilität und dem Einsatz bei hohen Betriebstemperaturen. Auch ein möglicher Einsatz der aktivierten Kohlenstoffe aus Celluloseacetat-Perlen in Li-Ionen-Kondensatoren als Kathodenmaterial mit TNO-Anode wird geprüft.:ABBILDUNGSVERZEICHNIS TABELLENVERZEICHNIS ABKÜRZUNGSVERZEICHNIS SYMBOLVERZEICHNIS 1 EINLEITUNG 2 THEORETISCHE GRUNDLAGEN 2.1 Ausgangsmaterialien 2.1.1 Cellulose 2.1.2 Celluloseester (Celluloseacetat, Celluloseacetat-butyrat, Celluloseacetat-phthalat) 2.1.3 Sphärische Partikel aus Cellulose und Cellulosederivaten 2.2 Kohlenstoffe 2.2.1 Kohlenstoffe in Energiespeichern 2.2.2 Amorphe Kohlenstoffe 2.2.3 Aktivierte Kohlenstoffe 2.3 Elektrochemische Speichermethoden 2.3.1 Superkondensatoren 2.3.1.1 Speicherarten – EDLC vs. Pseudokapazität 2.3.1.2 Elektrodenmaterialien 2.3.1.3 Elektrolytsysteme 2.3.2 Lithium-Ionen-Batterien 2.3.3 Lithium-Ionen-Kondensatoren 2.4 Methoden zur strukturellen Charakterisierung 2.4.1 Laserbeugungsspektroskopie 2.4.2 Sedimentationsverhalten zur Bestimmung der Porosität 2.4.3 Stickstoffphysiosorption 2.4.4 Raman-Spektroskopie 2.4.5 Rasterelektronenmikroskopie 2.4.6 Röntgendiffraktometrie 2.4.7 Viskositätsmessungen 2.5 Elektrochemische Charakterisierung 2.5.1 Zyklische Voltammetrie 2.5.2 Galvanostatisches Zyklieren 2.5.3 Elektrochemische Impedanzspektroskopie 2.5.4 Galvanostatische intermittierende Titrationstechnik 3 EXPERIMENTELLER TEIL 3.1 Herstellung Perlcellulose 3.1.1 Herstellung der sphärischen Celluloseester / Deacetylierung 3.1.2 Variationen der Parameter 3.2 Carbonisierung / Aktivierung 3.3 Herstellung der Elektrochemischen Energiespeicher 3.3.1 Superkondensatoren 3.3.2 Lithium-Ionen-Batterien 3.3.3 Lithium-Ionen-Kondensatoren 3.4 Chemikalien 3.5 Geräte und Methoden 4 ERGEBNISSE & DISKUSSION 4.1 Ausgangsmaterialien für die Herstellung von sphärischen Celluloseestern 4.2 Sphärische Celluloseester 4.2.1 Verschiedene CA-Materialien 4.2.2 Deacetylierung zur Perlcellulose 4.2.3 Partikelgröße 4.2.4 Salzgehalt 4.2.5 Tensidgehalt 4.2.6 Celluloseacetat-butyrat 4.2.7 Celluloseacetat-phthalat 4.2.8 Zusammenfassung der Herstellung sphärischer Partikel aus Celluloseestern 4.3 Kohlenstoffe auf Basis von sphärischen Celluloseestern 4.3.1 Einfluss der Carbonisierungsbedingungen auf die hergestellten Kohlenstoffe aus CA1-Perlen 4.3.2 Einfluss der verschiedenen Herstellungsbedingungen der Celluloseacetat-Perlen auf den resultierenden Kohlenstoff 4.3.3 Kohlenstoffe aus Celluloseacetat-butyrat-Perlen 4.3.4 Kohlenstoffe aus Celluloseacetat-phthalat 4.3.5 Zusammenhänge zwischen Präkursoren und Kohlenstoffen 4.4 Aktivierte Kohlenstoffe 4.4.1 Aktivierung von CA- und CAB-Perlen mit KOH 4.4.2 Vergleich von KOH mit anderen Aktivierungsreagenzien 4.5 Superkondensatoren mit Elektroden aus Kohlenstoffen auf Basis von sphärischen Celluloseestern in alkalischen Elektrolyten 4.5.1 Einfluss der Carbonisierungsbedingungen auf die Performance von Superkondensatoren mit CA1-Elektroden 4.5.2 Superkondensatoren auf Basis von Kohlenstoffen aus verschiedenen Celluloseestern 4.5.3 Aktivierte Kohlenstoffe 4.5.4 Zusammenhang zwischen den hergestellten Kohlenstoffen und deren Einsatz als Elektrodenmaterial in Superkondensatoren 4.6 Vergleich von alkalischen und neutralen Elektrolyten in Superkondensatoren 4.6.1 Charakterisierung der Elektrolyte 4.6.2 Neutrale Elektrolyte und alkalische Elektrolyte im Vergleich 4.6.3 Einfluss von Konzentration und Temperatur auf die Zellperformance mit Na2SO4-Elektrolyten 4.7 Kohlenstoffe aus sphärischen Celluloseestern als Anodenmaterial in Lithium-Ionen-Batterien 4.7.1 Einfluss der Carbonisierungsbedingungen auf CA1 als Anodenmaterial 4.7.2 Bindersysteme 4.7.3 Kohlenstoffe aus Celluloseestern mit verschiedenen Herstellungsbedingungen 4.7.4 Einfluss der Temperatur 4.8 Lithium-Ionen-Kondensatoren mit aktiviertem Kohlenstoff aus CA-Perlen als Kathodenmaterial 4.9 Vergleich der Kohlenstoffe als Elektrodenmaterial in den verschiedenen Energiespeichersystemen 5 ZUSAMMENFASSUNG 6 LITERATURVERZEICHNIS 7 ANHANG