Sodium-ion batteries (SIBs) are considered as a promising alternative to lithium-ion batteries (LIBs) for large-scale renewable energy storage units due to the abundance of sodium resource and its low cost. However, the development of anode materials for SIBs to date has been mainly limited to some traditional anodes for LIBs, such as carbonaceous materials. SnSe2 is a member of two dimensional layered transition metal dichalcogenide (TMD) family, which has been predicted to have high theoretical capacity as anode material for sodium ion batteries (756 mAh g-1), thanks to its layered crystal structure. Yet, there have been no studies on using SnSe2 as Na ion battery anode. In this thesis, we developed a simple synthesis method to prepare pure SnSe2 nanosheets, employing N2 saturated NaHSe solution as a new selenium source. The SnSe2 2D sheets achieve theoretical capacity during the first cycle, and a stable and reversible specific capacity of 515 mAh g-1 at 0.1 A g-1 after 100 cycles, with excellent rate performance. Among all of the reported transition metal selenides, our SnSe2 sample has the highest reversible capacity and the best rate performances. A combination of ex-situ high resolution transmission electron microscopy (HRTEM) and X-ray diffraction was used to study the mechanism of sodiation and desodiation process in this SnSe2, and to understand the reason for the excellent results that we have obtained. The analysis indicate that a combination of conversion and alloying reactions take place with SnSe2 anodes during battery operation, which helps to explain the high capacity of SnSe2 anodes for SIBs compared to other binary selenides. Density functional theory was used to elucidate the volume changes taking place in this important 2D material.

La demande urgente d'innovations dans le domaine du stockage de l'énergie est liée au développement récent de la production d'énergie renouvelable ainsi qu'à la diversification des produits électroniques portables qui consomment de plus en plus d'énergie. Il existe plusieurs technologies pour le stockage et la conversion électrochimique de l'énergie, les plus notables étant les batteries aux ions lithium, les piles à combustible et les supercondensateurs. Ces systèmes sont utilisés de façon complémentaire des uns aux autres dans des applications différentes. Par exemple, les batteries sont plus facilement transportables que les piles à combustible et ont de bonne densité d'énergie alors que les supercondensateurs ont des densités de puissance plus élevés et une meilleure durée de vie. L'objectif principal de ces travaux est d'étudier les performances électrochimiques d'une nouvelle famille de matériaux bidimensionnel appelée MXène, en vue de proposer de nouvelles solutions pour le stockage de l'énergie. Pour y arriver, plusieurs directions ont été explorées. Dans un premier temps, la thèse se concentre sur les supercondensateurs dans des électrolytes aqueux et aux effets des groupes de surface. La seconde partie se concentre sur les systèmes de batterie et de capacités à ions sodium. Une cellule complète comportant une anode en carbone et une cathode de MXène a été développées. La dernière partie de la thèse présente l'étude des MXènes pour les supercondensateur en milieu organique. Une attention particulière est apportée à l'étude du mécanisme d'intercalation des ions entre les feuillets de MXène. Différentes techniques de caractérisations ont été utilisées, en particulier la voltampérométrie cyclique, le cyclage galvanostatique, la spectroscopie d'impédance, la microscopie électronique et la diffraction des rayons X. / An increase in energy and power densities is needed to match the growing energy storage demands linked with the development of renewable energy production and portable electronics. Several energy storage technologies exist including lithium ion batteries, sodium ion batteries, fuel cells and electrochemical capacitors. These systems are complementary to each other. For example, electrochemical capacitors (ECs) can deliver high power densities whereas batteries are used for high energy densities applications. The first objective of this work is to investigate the electrochemical performances of a new family of 2-D material called MXene and propose new solutions to tackle the energy storage concern. To achieve this goal, several directions have been explored. The first part of the research focuses on MXene behavior as electrode material for electrochemical capacitors in aqueous electrolytes. The next part starts with sodium-ion batteries, and a new hybrid system of sodium ion capacitor is proposed. The last part is the study of MXene electrodes for supercapacitors is organic electrolytes. The energy storage mechanisms are thoroughly investigated. Different characterization techniques were used in this work, such as cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy, scanning electron microscopy and X-ray diffraction.

The demand for electrical energy storage has increased tremendously in recent years, especially in the applications of portable electronic devices, transportation and renewable energy. The performances of lithium-ion and sodium-ion batteries depend on their electrode materials. In commercial Li-ion batteries with graphite anodes the intercalation potential of lithium in graphite is close to the reversible Li/Li⁺ half-cell potential. The proximity of the potentials can result in unintended electroplating of metallic instead of intercalation of lithium in the graphite anode and frequently leads to internal shorting and overheating, which constitute unacceptable hazards, especially when the batteries are large, as they are in cars and airplanes. Moreover, graphite cannot be readily used as the anode material of Na-ion batteries, because electroplating of metallic sodium on graphite is kinetically favored over sodium intercalation in graphite. This dissertation examines safer Li-ion and Na-ion battery anode materials. / text

Doctor of Philosophy / Department of Mechanical and Nuclear Engineering / Gurpreet Singh / The inevitable depletion of fossil fuels and related environmental issues has led to exploration of alternative energy sources and storage technologies. Among various energy storage technologies, rechargeable metal-ion batteries (MIB) are at the forefront. One dominant factor affecting the performance of MIB is the choice of electrode material. This thesis reports synthesis of paper like electrodes composed for three representative layered materials (van der Waals sheets) namely reduced graphene oxide (rGO), molybdenum disulfide (MoS₂) and hexagonal boron nitride (BN) and their use as a flexible negative electrode for Li and Na-ion batteries. Additionally, layered or sandwiched structures of vdW sheets with precursor-derived ceramics (PDCs) were explored as high C-rate electrode materials. Electrochemical performance of rGO paper electrodes depended upon its reduction temperature, with maximum Li charge capacity of 325 mAh.g⁻¹ observed for specimen annealed at 900°C. However, a sharp decline in Na charge capacity was noted for rGO annealed above 500 °C. More importantly, annealing of GO in NH₃ at 500 °C showed negligible cyclability for Na-ions while there was improvement in electrode's Li-ion cycling performance. This is due to increased level of ordering in graphene sheets and decreased interlayer spacing with increasing annealing temperatures in Ar or reduction at moderate temperatures in NH₃. Further enhancement in rGO electrodes was achieved by interfacing exfoliated MoS₂ with rGO in 8:2 wt. ratios. Such papers showed good Na cycling ability with charge capacity of approx. 225.mAh.g⁻¹ and coulombic efficiency reaching 99%. Composite paper electrode of rGO and silicon oxycarbide SiOC (a type of PDC) was tested as high power-high energy anode material. Owing to this unique structure, the SiOC/rGO composite electrode exhibited stable Li-ion charge capacity of 543.mAh.g⁻¹ at 2400 mA.g⁻¹ with nearly 100% average cycling efficiency. Further, mechanical characterization of composite papers revealed difference in fracture mechanism between rGO and 60SiOC composite freestanding paper. This work demonstrates the first high power density silicon based PDC/rGO composite with high cyclic stability. Composite paper electrodes of exfoliated MoS₂ sheets and silicon carbonitride (another type of PDC material) were prepared by chemical interfacing of MoS₂ with polysilazane followed by pyrolysis . Microscopic and spectroscopic techniques confirmed ceramization of polymer to ceramic phase on surfaces on MoS₂. The electrode showed classical three-phase behavior characteristics of a conversion reaction. Excellent C-rate performance and Li capacity of 530 mAh.g⁻¹ which is approximately 3 times higher than bulk MoS₂ was observed. Composite papers of BN sheets with SiCN (SiCN/BN) showed improved electrical conductivity, high-temperature oxidation resistance (at 1000 °C), and high electrochemical activity (~517 mAh g⁻¹ at 100 mA g⁻¹) toward Li-ions generally not observed in SiCN or B-doped SiCN. Chemical characterization of the composite suggests increased free-carbon content in the SiCN phase, which may have exceeded the percolation limit, leading to the improved conductivity and Li-reversible capacity. The novel approach to synthesis of van der Waals sheets and its PDC composites along with battery cyclic performance testing offers a starting point to further explore the cyclic performance of other van der Waals sheets functionalized with various other PDC chemistries.

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Sodium-ion batteries (SIBs) are rechargeable batteries analogous to lithium-ion batteries but use sodium ions (Na+) as the charge carriers. They are considered a promising alternative for lithium-ion batteries (LIBs) in renewable large-scale energy storage applications due to their similar electrochemical mechanisms and abundant sodium resources. Two-dimensional (2D) materials, with atomic or molecular thickness and large lateral lengths, have emerged as important functional materials due to their unique structures and excellent properties. These 2D nanosheets have been highly studied as sodium-ion battery anodes. They have large interlayer spacing, which can effectively buffer the big volume expansion and prevent electrode collapse during the charge-discharge process. Different strategies such as preparing composites, heterostructures, expanded structures, and chemical functionalization can greatly improve cycling stability and lead to high reversible capacity. In this dissertation, state-of-the-art SIB based on 2D material electrodes will be presented. In particular, Tin-based 2D materials and laser-scribed graphene anodes are discussed. Different strategies involving engineering both synthesis methods, intrinsic properties of materials, and device architecture are used to optimize the battery performance.

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第19739号 / 工博第4194号 / 新制||工||1647(附属図書館) / 32775 / 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 陰山 洋, 教授 作花 哲夫 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

No description available.

京都大学 / 新制・課程博士 / 博士(工学) / 甲第25302号 / 工博第5261号 / 新制||工||2001(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 阿部 竜, 教授 陰山 洋 / 学位規則第4条第1項該当 / Doctor of Agricultural Science / Kyoto University / DGAM

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.