Graduation date: 1995

Lithium-ion battery (LIB) is an indispensable energy storage device in portable electronics, and its applications in electric vehicles and grid-level energy storage are increasing dramatically in recent years due to high demands. To meet energy demands and address fire hazards, next generation batteries with better safety, higher energy density, and longer cycle life have been actively investigated. In this thesis, works on polymer and ceramic solid electrolytes to improve safety and energy density of rechargeable solid-state batteries are discussed. In the first section, a flexible composite solid electrolyte is presented. Since ceramic electrolytes have high conductivities but are fragile, and polymer electrolytes are easy to process but have low conductivities, we propose a composite structure that combines these advantages. A vertically aligned and connected ceramic electrolyte is realized through the ice-templating method to improve the ionic conduction. Then a polyether-based polymer electrolyte is added to make the composite electrolyte flexible. Specifically, vertically aligned and connected LATP and LAGP nanoparticles (NPs) in the polyethylene oxide (PEO) matrix are made. The conductivity reaches 0.52 × 10-4 S/cm for LATP/PEO, and 1.67 × 10-4 S/cm for aligned LAGP/PEO composite electrolytes, which are several times higher than that with randomly dispersed LATP/LAGP NPs in PEO. Compared to the pure PEO electrolyte, the mechanical and thermal stabilities of the composite solid electrolyte are higher. The LFP-LAGP/PEO-Li cell with 148.7 mAh/g during the first discharge at 0.3C has over 95% capacity retention after 200 cycles. This method opens a new approach to optimize ion conduction in composite solid electrolytes for solid-state batteries. In the next section, polyether-based polymer electrolytes such as PEO and PEG are studied. Polyether-based electrolytes are electrochemically unstable above 4 V, restricting their use with high voltage cathodes such as NMC for high energy density. A technique involving atomic layer deposition (ALD) of Al2O3 to stabilize the polyether-based electrolyte with 4 V class cathodes is described. With a 2 nm Al2O3 coating, the capacity retention stays at 84.7% after 80 cycles and 70.3% after 180 cycles for the polyether-based electrolyte. Without the coating, the capacity drops more than 50% after only 20 cycles. This study opens new opportunity to develop safe electrolytes for lithium batteries with high energy density. In the final section, we propose a new polymer electrolyte, a poly(vinylidene fluoride) (PVDF) polymer electrolyte with organic plasticizer dimethylformamide (DMF), which possesses compatibility with 4V cathode for high energy density and high ionic conductivity (1.2×10-4 S/cm) at room temperature. This polymer electrolyte can be used as a supplement for the polyether-based electrolytes we discussed in the first two sections. In this polymer electrolyte, palygorskite ((Mg,Al)2Si4O10(OH)) nanowires are introduced to form composite solid electrolytes (CPE) to enhance both stiffness and toughness of PVDF/DMF-based polymer electrolyte. With 5 wt % of palygorskite nanowires, the elastic modulus of the PVDF-DMF CPE increases from 9.0 MPa to 96 MPa, and its yield stress increases by 200%. We further demonstrate that full cells composed of Li(Ni1/3Mn1/3Co1/3)O2 (NMC 111) cathode, PVDF-DMF/palygorskite CPE, and lithium metal anode, can be cycled over 200 times at 0.3 C, with 97% capacity retention. Moreover, the PVDF-DMF electrolyte is nonflammable, making it a safer alternative to the conventional liquid electrolyte. Our work illustrates that the PVDF-DMF/palygorskite CPE is a promising electrolyte for solid state batteries with better safety and cycling performance. Collectively, we study the polyether-based polymer electrolyte and ceramic electrolyte to combine their advantages through the ice-templating method in a battery, use ALD technique to stabilize polyether-based electrolyte for high energy density, and propose an alternative PVDF/DMF-based polymer electrolyte with nanowire additives for high energy density and stable cycling, contributing to the rechargeable solid-state batteries, with better safety, higher energy density and better cycling stability.

Graduation date: 1996

Thesis (Ph. D.)--Brigham Young University Dept. of Chemical Engineering, 2006. / Includes bibliographical references (p. 155-165).

No description available.

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

Soft materials are indispensable components of energy storage and conversion technologies necessary for the renewable energy transition. Two key examples are electrolytes used in solid-state batteries and ion-exchange membranes used in electrolysis and electrodialysis. The figures of merit for these applications are often summarized using upper-bound relationships, which define the best possible combination of performance metrics for a given material. A promising route to break the upper-bound and to improve upon the state-of-the-art is engineering materials at the nanoscale. Two commonly employed strategies are the use of block copolymers and polymer nanocomposites. In the former, the sequence of different monomers along the backbone of the polymer chain is varied; in the latter, ceramic nanoparticles are mixed with polymers and processed to achieve different dispersion states. In both of these classes of materials, the self-assembly of molecular and colloidal components controls the structure and function of the resulting material. This dissertation investigates these structure-property relationships in model soft nanomaterials, namely colloids, polymer nanocomposites, and ion-exchange membranes, using experiments, molecular dynamics simulations, and theory. The dissertation can be divided into three parts. The first, Chapters 2 and 3, investigates polymer and polymer nanocomposite electrolytes for applications in solid-state Li batteries. Chapter 2 investigates the coarse-graining and force field parameterization of polymer electrolytes for molecular dynamics simulations. Chapter 3 reports the experimental characterization of polymer nanocomposite electrolytes, with a key focus on understanding how the particle dispersion state affects the ionic conductivity and mechanical reinforcement of the composite. The second part, Chapters 4 and 5, studies fundamental structure-property relationships in two types of polymer nanocomposites. In Chapter 4, the surface chemistry of hydrophilic silica nanoparticles is altered to promote miscibility in organic solvents and in semicrystalline polymers. In these "bare" nanocomposites, the particles are stabilized against aggregation via the adsorption of a polymer bound layer, which is quantitatively studied via small angle X-ray scattering. In Chapter 5, the surface-modified particles are densely grafted with polymer chains via surface-initiated polymerization to obtain matrix-free polymer grafted nanoparticle films. The collective dynamics of the nanoparticle cores in these self-supporting films, where all of the polymer is grafted to the particle surface, is then measured using X-ray photocorrelation spectroscopy at a variety of temperatures. In Chapters 6 and 7, random copolymer chemistries are used to create cation- and anion-exchange membranes, respectively, with controlled ion-exchange capacity and swelling behavior. The key finding of Chapter 6 is that water-lean cation-exchange membranes selectively transport ions with low free energies of hydration, allowing the design of specific-ion selective electrodialysis stacks for Li+ recovery applications. The analogous properties of anion-exchange membranes are suggested as an avenue for future research.

Les batteries au lithium tout solide présentent un grand intérêt pour le développement de systèmes de stockage de grande densité (volumique) d'énergie et sûrs notamment en raison de leur excellente stabilité thermique par rapport aux technologies lithium-ions à électrolyte liquide. Cependant, avec l'épaisseur de la batterie, de fortes limitations cinétiques sont observées, en raison i/ de la relativement faible mobilité des ions dans les matériaux inorganiques et ii/ de la présence de joints de grains généralement bloquants aux interfaces solide/solide. De plus au cours de la charge/décharge de la batterie, les matériaux actifs (réservoir de l'énergie) changent de volume ce qui induit des contraintes mécaniques interfaciales qui provoquent la formation de micro-fractures très dommageables à la cyclabilité de ces systèmes. Cette thèse concerne la réalisation et la caractérisation de batteries inorganiques monolithiques (avec les électrodes composites) en utilisant une méthode de frittage: Spark Plasma Sintering (SPS). La formulation des électrodes composites est fondamentale car ce sont de multi-matériaux qui doivent présenter de nombreuses fonctionnalités: 1) une grande densité d'énergie 2) une bonne percolation électronique (resp. ionique) enfin 3) une bonne tenue mécanique avec des interfaces électrodes/electrolyte stables afin d'assurer la durée de vie des cellules.Le principal objectif est de trouver des relations, pour des matériaux donnés, entre la texture des poudres initiales, la microstructure des céramiques obtenues par frittage SPS et les propriétés électriques (électronique et ionique) ainsi que les performances électrochimiques. / All-solid batteries with inorganic solid electrolytes are attractive candidates in electrochemical energy storage since they offer high safety, reliability and energy density. Aiming to increase the surface capacity strong efforts have been made to increase the thickness of the electrode. However, the thicker electrode, the more stress is generated at the solid/solid interfaces because of the volume change of the active material during lithium insertion/desinsertion upon cycling, which leads to formation of micro-cracks between the components and finally a bad cycling life. The possible answer to this issue is to build in place of a dense phase pure electrode, a composite electrode which is a multifunctional material. This composite electrode should contain a lot of electrochemically active material, the reservoir of energy; together with electronic and ionic conductor additives, to ensure efficient and homogeneous transfer of electrons and ions in the electrode volume.The main scope of this thesis was to develop all-solid-state batteries prepared by SPS method for applications at elevated temperatures. These batteries consist of a two composite electrodes separated by the NASICON-type solid electrolyte Li1.5Al0.5Ge1.5(PO4)3. The main objective was to find relationships, for given materials, between the initial powder granulometry (grain size, size distribution, agglomeration), the microstructure of ceramics obtained by SPS sintering, and the electrochemical performances of the final batteries. By creating electrodes with novel materials and better composition, the trade-off of power density and energy density can be minimized.

Les deux décennies écoulées ont connu le formidable essor de l'électronique portable qui a bouleversé notre société, essor rendu possible par l'invention des batteries Li-ion, qui fournissent une densité d'énergie élevée pour un poids et un volume réduits. Nous assistons aujourd'hui à une diversification des besoins en termes de stockage électrochimique de l'énergie, avec le développement de nouvelles applications (énergies renouvelables, transport) dont les contraintes ne sont pas les mêmes. Pour certaines applications, les exigences en termes de sécurité des personnes seront aussi importantes que celles en termes de densité d’énergie et de coût. Par ailleurs, la recherche se tourne de plus en plus vers les batteries Na-ion dont le coût de dépend pas du prix du lithium. En résumé, tel ou tel système de stockage électrochimique sera adapté à telle ou telle application.Le remplacement des électrolytes organiques liquides par des électrolytes solides inorganiques est une solution intéressante pour améliorer la sûreté des batteries, les conducteurs ioniques inorganiques étant non-inflammables, stables à haute température, et supposés plus stables chimiquement et électrochimiquement. L’emploi de ces matériaux dans des batteries « bulk tout-solide » s'accompagne néanmoins de problèmes interfaciaux limitant leurs performances, tels que la perte de contact entre particules aux interfaces, ou encore des problèmes de compatibilité chimique et électrochimique entre les matériaux. L’un des problèmes affectant ce type de batteries est l’interdiffusion d’espèces aux interfaces, accompagnée d'une augmentation d'impédance des batteries au cours du cyclage. Bien que des solutions aient déjà été proposées, comme le revêtement des particules de matière active par une couche de matériau moins réactif, il y a un manque de connaissance des espèces chimiques formées aux interfaces par réaction entre les matériaux, connaissance nécessaire afin d’améliorer les performances de tels systèmes. C'est là que se situait l'objectif de cette thèse: étudier les interactions se produisant aux interfaces électrode-électrolyte au sein de batteries «bulk tout-solide», et identifier les espèces chimiques formées. Le travail a été réalisé entre l’IPREM de Pau et le LRCS de l'Université d'Amiens. Deux électrolytes solides ont été étudiés: l’argyrodite Li6PS5Cl et le NaSICON Na3Zr2Si2PO12. Les matériaux été synthétisés, puis intégrés dans des batteries «bulk tout-solide». Les interfaces ont été caractérisées par spectroscopie photoélectronique à rayonnement X (XPS) et par spectroscopie d’électrons Auger (AES), deux techniques complémentaires, la première permettant l'identification et la quantification des espèces chimiques en extrême surface, la seconde permettant d’obtenir des informations sur leur répartition à l'échelle nanométrique.L’analyse de batteries «bulk tout-solide» basées sur l’électrolyte Na3Zr2Si2PO12 et utilisant le matériau actif Na3V2(PO4)3 a permis mettre en évidence des modifications micromorphologiques au cours du cyclage, accompagnées de phénomènes d’interdiffusion des éléments entre les particules. Les analyses AES conduites sur ce type de batteries nous ont permis de mieux décrire les phénomènes d’autodécharge.Les analyses conduites sur les batteries basées sur l’électrolyte Li6PS5Cl nous ont permis de montrer que cet électrolyte solide présente une bonne stabilité vis à vis du matériau d'électrode négative LTO. En revanche, il présente une réactivité interfaciale avec des matériaux d'électrode positive tels que LCO, NMC, LMO, LFP, ou LiV3O8. Cette réactivité se traduit par la formation d'espèces aux interfaces incluant LiCl, P2Sx , Li2Sn , S0 et des phosphates. En dépit des problèmes de réactivité interfaciale constatés, nous avons pu au cours de cette thèse mettre au point des batteries « tout-solide » basées sur l’électrolyte Li6PS5Cl présentant une bonne rétention de capacité sur 300 cycles lorsqu'elles sont cyclées entre 2,8 et 3,4V. / The last two decades have shown a tremendous spreading of portable electronics, changing our society. This change was made possible by the invention of Li-ion batteries, which provide a high energy density for a low weight and volume. More recently the development of new applications, such as electric vehicles or renewable energies, has led to new needs in terms of electrochemical storage. For some applications, user safety will be as important as cost and energy density. On the other hand, research around Na-ion batteries focuses an increased interest, because they do not depend on lithium cost. Replacing organic liquid electrolytes with inorganic solid electrolytes is an interesting solution to improve the safety of batteries, because inorganic ionic conductors are nonflammable, stable at high temperature, and supposed to be chemically and electrochemically more stable. Using those materials in all-solid-state batteries has however several limiting factors, such as loss of contact between particle at the interfaces during cycling, and also chemical/electrochemical compatibility issues between materials. Another issue with this type of batteries is the interdiffusion of species at interfaces leading to an impedance increase during cycling. Several solutions exist to mitigate those issues, such coating the active material particles with a less reactive inorganic material. However there is a lack of knowledge on the species forming at those interfaces, knowledge which is needed to improve the performances of such systems. Studying those interfacial interactions and characterizing the species formed as those interfaces was the main topic of this Ph.D thesis.This work has been done in collaboration between two laboratories : IPREM (University of Pau - CNRS, France) and LRCS (University of Amiens - CNRS, France). Two solid electrolytes have been studied: the argyrodite Li6PS5Cl and the NaSICON Na3Zr2Si2PO12. Those materials have been synthetized, then integrated in bulk all-solid-state batteries and their interfaces were characterized by X-Ray Photoelectron Spectroscopy (XPS) and Auger Electron Spectroscopy (AES). Those two techniques provide us very complementary information, the first allowing identification and quantification of surface species, the second one giving access to the spatial repartition of elements at a nanometric level.The analysis of bulk all-solid-state batteries based on the electrolyte Na3Zr2Si2PO12 using the active material Na3V2(PO4)3 showed micromorphologic changes during cycling, as well as interdiffusion phenomena between particles. AES analysis also allowed us to describe self-discharge issues.The study of Li6PS5Cl-based batteries highlighted that this solid electrolyte is stable towards the negative electrode active material LTO. It however has interfacial reactivity towards positive electrode active materials such as LCO, NMC, LMO, LFP and LiV3O8. This reactivity leads to the formation of several species such as LiCl, P2Sx , Li2Sn , S0 and phosphates at the interface with Li6PS5Cl. In spite of the encountered interfacial reactivity issues, we managed to build all-solid-state batteries based on Li6PS5Cl showing a good capacity retention over 300 cycles when cycled between 2.8 and 3.4V.

L’un des enjeux pour le développement des batteries tout-solide est d’augmenter la conductivité ionique des électrolytes solides. Le sujet de la thèse porte sur l’étude de deux types de matériaux d’électrolytes solides inorganiques cristallins: les Grenat Li7- 3xAlxLa3Zr2O12 (LLAZO) et les Nasicon Li1.15- 2xMgxZr1.85Y0.15(PO4)3 (LMZYPO). L’objectif de cette étude est de comprendre dans quelle mesure les propriétés conductrices des matériaux étudiés sont impactées par des modifications structurales générées soit par un procédé de traitement particulier, soit par une modification de la composition chimique, et ce grâce au croisement des données structurales acquises par diffraction des rayons X (DRX) et Résonance Magnétique Nucléaire (RMN) MAS avec des données de dynamique des ions déduites de mesures de RMN en température et de spectroscopie d’impédance électrochimique (SIE).Les poudres ont été synthétisées après optimisation des traitements thermiques par méthode solide-solide ou solgel. La densification des pastilles utilisées pour les mesures de conductivité ionique par SIE a été réalisée par la technique de frittage Spark Plasma Sintering (SPS).Dans le cas des grenats LLAZO, l’originalité de notre travail est d’avoir montré qu’un traitement de frittage par SPS, au-delà de la densification attendue des pastilles, engendre également des modifications structurales qui ont des conséquences directes sur la mobilité des ions lithium dans le matériau et par conséquent sur la conductivité ionique. Une augmentation franche de la dynamique microscopique des ions lithium après frittage par SPS a en effet été observée par des mesures en température de RMN de 7Li et le suivi des constantes de relaxation.La deuxième partie de l’étude constitue un travail exploratoire sur la substitution de Li+ par Mg2+ dans LMZYPO. Nous avons ainsi étudié les propriétés de conduction ionique de ces composés mixtes Li/Mg, en parallèle d’un examen minutieux des phases cristallines formées. Nous avons notamment montré que la présence de Mg2+ favorise la formation des phases β’ (P21/n) et β (Pbna) moins conductrices ce qui explique la diminution de la conductivité ionique avec le taux de substitution de Li+ par Mg2+ observée dans ces matériaux de type Nasicon.Nos travaux soulignent donc l’importance primordiale des effets de structure sur les propriétés de matériaux d’électrolytes solides de type céramique. / One of the issues for the development of all-solid-state batteries is to increase the ionic conductivity of solid electrolytes. The thesis work focuses on two types of materials as crystalline inorganic solid electrolytes: a Garnet Li7-3xAlxLa3Zr2O12 (LLAZO) and a Nasicon Li1.15-2xMgxZr1.85Y0.15(PO4)3 (LMZYPO). The objective of this study is to understand to what extent the conduction properties of the studied materials are impacted by structural modifications generated either by a particular treatment process, or by a modification of the chemical composition. Structural data acquired by X-ray diffraction (XRD) and Magic Angle Spinning (MAS) Nuclear Magnetic Resonance (NMR) were then crossed with ions dynamics data deduced from NMR measurements at variable temperature and electrochemical impedance spectroscopy (EIS).The powders were synthesized after optimizing thermal treatments using solid-solid or sol-gel methods. Spark Plasma Sintering (SPS) technique was used for the densification of the pellets used for ionic conductivity measurements by EIS.In the case of garnets LLAZO, the originality of our work is to have shown that a SPS sintering treatment, beyond the expected pellets densification, also generates structural modifications having direct consequences on the lithium ions mobility in the material and therefore on the ionic conductivity. A clear increase of the lithium ions microscopic dynamics after SPS sintering was indeed observed by variable temperature 7Li NMR measurements and the monitoring of the relaxation times.The second part of the study provides an exploratory work on the substitution of Li+ by Mg2+ in LMZYPO. We studied the ionic conduction properties of these mixed Li/Mg compounds, in parallel with a fine examination of the crystalline phases formed. We have showed in particular that the presence of Mg2+ favors the formation of the less conductive β’ (P21/n) and β (Pbna) phases, which explains the decrease of the ionic conductivity with the substitution level of Li+ by Mg2+ observed in these Nasicon type materials.Our work therefore highlights the crucial importance of structural effects on the conduction properties of ceramic solid electrolyte materials.