Improvements in energy storage are required to facilitate the transition to renewable energy and the electrification of transport. Lithium-ion batteries (LIBs) are a promising solution, but the current leading chemistry, consisting of a layered oxide cathode and a graphite anode separated by a liquid electrolyte, has been optimized to near-theoretical limits. Replacing the graphitic carbon with Li metal would significantly improve energy density but the instability of the Li metal-electrolyte interface introduces performance and safety challenges. Using a solid-state electrolyte (SSE) to construct an all-solid-state battery (ASSB) could mitigate these issues. However, an ideal SSE material has yet to be identified.
\r\n \r\nThousands of known Li-containing materials have not yet been evaluated as SSEs. Data-driven methods could prioritize materials for experimental study but have historically lacked sufficient data and optimal representations. Chapter 2 presents the largest structure-ionic conductivity database to date and uses semi-supervised learning to determine the highest-performing descriptors. From ~26,000 Li-containing materials, 212 candidates are identified and screened using semi-empirical and first-principles calculations. Li3BS3 exhibits ionic conductivity above 10-3 S cm-1 with defect engineering through substitution and mechanical milling.
\r\n \r\nChapter 3 explores Cl, Al, and Si substitution in Li3BS3 to reveal mechanisms of ionic conductivity enhancement. At low substitution levels, conductivity improvements are driven by disordered environments from reduced crystallinity and microstructural effects. For Cl and Al, higher substitution generates fully amorphous phases with ionic conductivity above 10-4 S cm-1. Sufficient Si substitution produces novel crystalline phases with conductivities exceeding 10-3 S cm-1.
\r\n \r\nPrevious approaches, such as that in Chapter 2, could not represent disordered compounds, excluding much of the training data and candidate materials. This is particularly significant given the importance of disorder highlighted in Chapters 2 and 3 and the prevalence of disorder in known superionic conductors. Chapter 4 implements a transfer-learned graph representation compatible with disordered structures. A larger database is curated and used to train models for screening all known Li-containing materials. Experimental validation of superionic conductivity in an identified candidate demonstrates the utility of this graph-based approach for discovering experimentally relevant, high-performance materials.
", "doi": "10.7907/fn7h-vz84", "publication_date": "2026", "thesis_type": "phd", "thesis_year": "2026" }, { "id": "thesis:17097", "collection": "thesis", "collection_id": "17097", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:03272025-184257192", "type": "thesis", "title": "Investigation and Control of the Electrode/Electrolyte Interface in Electrochemical Systems", "author": [ { "family_name": "Lee", "given_name": "Brian Chansol", "orcid": "0000-0002-0898-0838", "clpid": "Lee-Brian-Chansol" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "In electrochemical reactions, the electrode/electrolyte interface is of vital importance, as no reactivity occurs in the bulk electrode or the electrolyte. Often, the interface can be the difference between a successful reaction and a failure. In this thesis, we present three works wherein the electrode/electrolyte interface is studied and controlled to drive desired electrochemical reactivity. A Mg-In alloy is employed for Mg metal batteries to prevent Mg dendrite growth, which can cause cell shorting and failure. By coating the surface of Mg metal electrodes with the Mg-In alloy, the nucleation of Mg dendrites is suppressed and instead the Mg electroalloys into the surface alloy upon reduction, significantly increasing the cell life time. Next, the Li-intercalation material LiTiS\u2082 is studied for use in organic reductive electrosynthesis as counter anodes. Traditional metal sacrificial counter anodes are known to cause issues such as surface passivation, chemical reactivity, and cross-plating at the working electrode, which is deleterious to the desired organic reactivity. It is found that LiTiS\u2082 surface is less reactive in organic electrolytes, reducing both passivation and chemical reactivity. Further, Li\u207a de-intercalated from LiTiS\u2082 oxidation is found to be less susceptible to cross-plating than Zn, a common sacrificial anode. Finally, the effect of electrode material on the electrochemical reduction of \u1d57BuI is studied. Using electrochemical characterization, it is found that the reduction is catalyzed on Au and Ag through adsorption of the initial substrate, as well as the adsorption of the reactive intermediate tBu radical. The catalysis of \u1d57BuI reduction can have meaningful consequences for organic reactivity, driving the desirable generation of the carbanion nucleophile from alkyl halide reactants.", "doi": "10.7907/fz2d-pe37", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17192", "collection": "thesis", "collection_id": "17192", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05022025-025023583", "type": "thesis", "title": "Beyond Li: Challenges in Moving Towards Earth-Abundant Battery Materials", "author": [ { "family_name": "Qian", "given_name": "Michelle Dena", "orcid": "0000-0002-4815-1014", "clpid": "Qian-Michelle-Dena" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Rossman", "given_name": "George Robert", "orcid": "0000-0002-4571-6884", "clpid": "Rossman-G-R" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Batteries are a necessary component towards the advancement and proliferation of modern day technology, and are also an essential piece of the transition towards renewable energy. The lithium-ion battery (LIB) is the most common type of rechargeable battery, and the archetype relies on a traditional layered transition metal oxide cathode, organic electrolyte with a lithium salt, and a graphite anode. The design of these cells has been optimized to the point that the energy densities in these batteries are approaching their theoretical capacities. Combined with the supply chain challenges associated with many typical cathode elements and increasing energy demand, this highlights the need for new earth-abundant, high energy density battery technology. This thesis addresses challenges in two such systems: Mg-S and sodium-ion batteries (SIBs). Mg-S batteries suffer from capacity fade related to the polysulfide shuttle effect, which results in loss of active material and passivation of the anode. Here, we demonstrate that the rate of passivation is inversely proportional to the chain length of the polysulfides present in solution, and that passivation can be slowed or even reversed through addition of S\u2088 and the consequent perturbation of existing polysulfide speciation equilibria. SIBs are frequently touted as a \"drop-in\" technology for LIBs due to both systems relying on mobile alkali ions, but SIBs have inherently lower energy densities due to larger Na\u207a ion. In Chapters 3 and 4 we explore anion redox as a method of increasing energy densities in SIBs--Chapter 3 shows that in LiNaFeS\u2082, the charge compensation mechanisms from Li and Na cycling are identical. However, Na\u207a cycling is worsened compared to Li\u207a by structural degradation from the removal and insertion of the bulky Na\u207a ion, emphasizing the differences that exist between optimizing SIB cathode performance compared with that of LIBs. In Chapter 4, we aim to develop structure-property relationships that enable a stronger understanding of anion redox that can be leveraged to design high energy density, multielectron redox cathodes. Through the examination of the electrochemically inactive NaCu1.5Fe0.5S\u2082 and its vacancy-containing derivative NaCu1.125Fe0.625S\u2082, we show that vacancies in the transition metal layer enable redox although the redox is observed occurs on the transition metals. The study also demonstrates potential limitations of ideal model systems and bulk spectroscopic analysis techniques in materials with low degrees of redox.
", "doi": "10.7907/s5ws-m162", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17233", "collection": "thesis", "collection_id": "17233", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05152025-202058082", "primary_object_url": { "basename": "Stradley_Thesis.pdf", "content": "final", "filesize": 41167317, "license": "other", "mime_type": "application/pdf", "url": "/17233/3/Stradley_Thesis.pdf", "version": "v5.0.0" }, "type": "thesis", "title": "Materials and Interfaces to Enable Reversible Mg Electrochemistry for Energy Storage Applications", "author": [ { "family_name": "Stradley", "given_name": "Steven Hartzel", "orcid": "0009-0009-7154-608X", "clpid": "Stradley-Steven-Hartzel" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Climate change drives the need for a dramatically increased deployment of electric vehicles and intermittent renewable energy sources. Each of these depends intimately on batteries for range and reliability. Although Li-ion batteries are the current industry standard for electrochemical energy storage, they are based on scarce and unevenly distributed resources. It is thus crucial to develop rechargeable battery chemistries based on more energy dense and resource equitable materials. Orders of magnitude more abundant and energy dense than Li, Mg is an attractive alternative to Li for energy storage. Despite its many attractive properties, deployment of Mg-based chemistries is hindered by a lack of cathode, anode, and electrolyte materials which support Mg electrochemistry and are mutually compatible. This thesis endeavors to deploy new materials to sustain reversible Mg electrochemistry and to understand how certain material properties impact electrochemical performance. First, we investigate new cathode materials based on Earth-abundant transition metal chlorides. These cathodes cycle somewhat reversibly but are prone to rapid capacity fade due to active material dissolution and shuttle. We identify electrolyte modification as a means to combat this fade. Next, we characterize halide-free Mg electrolytes based on weakly coordinating Si-centered anions. These electrolytes display impressively high oxidative stabilities but also relatively high reductive overpotentials and a fatal vulnerability to passivation by H\u2082O. We then consider a class of electrolytes based on B-centered anions with aryl ligands. These systems show exceptionally low reductive overpotentials among halide-free Mg electrolytes. We increase the bulk of the anion and correspondingly observe a slight increase in the reductive overpotential and an enhancement in rate performance. Though this class of compounds shows a low oxidative stability, the structure-property relationships gleaned from it may prove useful in future electrolyte studies. Finally, we deploy Al as an Earth-abundant, high capacity alloying anode for Mg-based batteries. Though the native kinetics for Mg-Al alloying prove too sluggish for practical systems, we use Bi to enhance the alloying kinetics of Al by two orders of magnitude. Though alloying capacity is limited by a large particle size, we present a viable method for enhancing Al alloying kinetics to relevant rates, thereby unlocking a highly desirable material for future studies. Taken together, this work expands the scope of cathode, electrolyte, and anode materials which support reversible Mg electrochemistry. Though imperfect, the lessons we learn from them may inform future design decisions to enable reversible Mg-based batteries.", "doi": "10.7907/vs2j-ep54", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17264", "collection": "thesis", "collection_id": "17264", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05222025-165729471", "primary_object_url": { "basename": "pham_kim_2024_thesis-final.pdf", "content": "final", "filesize": 41860246, "license": "other", "mime_type": "application/pdf", "url": "/17264/1/pham_kim_2024_thesis-final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Application of Ultrafast Spectroscopy Techniques to Probe Correlated Ion Hopping Mechanisms in Solid-State Ion Conductors", "author": [ { "family_name": "Pham", "given_name": "Kim Hoang", "orcid": "0000-0003-4053-6363", "clpid": "Pham-Kim-Hoang" } ], "thesis_advisor": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Blake", "given_name": "Geoffrey A.", "orcid": "0000-0003-0787-1610", "clpid": "Blake-G-A" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Superionic conductors, or solid-state ion conductors that surpass the ionic con- ductivity of its liquid counterpart, can enable more energy dense batteries, robust artificial ion pumps, and optimized fuel cells. The mechanisms enabling superionic conductivity still remain elusive, though many-body correlations between the mi- grating ions, lattice vibrational modes, and charge screening clouds have all been posited to greatly enhance ionic conduction. Most spectroscopic techniques cannot directly probe and validate the role of such correlations due to their inability to transiently resolve these ultrafast dynamics occurring at picosecond timescales. In this work, we develop an ultrafast technique that measures the time-resolved change in impedance while a light source ranging from UV to THz frequencies selectively excites an ion-coupled correlation. The technique is used to compare the relative changes in impedance of a solid-state Li\u207a conductor Li0.5La0.5TiO3 (LLTO) before and after light excitation to elucidate the role of charge screening clouds, optical phonons, and acoustic phonons on ion migration. From our techniques, we deter- mine that electronic screening and rocking phonon-mode interactions significantly dominate the ion migration pathway of LLTO compared to acoustic phonons. Al- though we only present one case study, our technique can extend to O\u00b2\u207b, H\u207a, or other charge carrier transport phenomena where ultrafast correlations control transport. Furthermore, the temporal relaxation of the measured impedance can distinguish ion transport effects caused by many-body correlations, optical heating, correlation, and memory behavior.", "doi": "10.7907/825x-r459", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:17399", "collection": "thesis", "collection_id": "17399", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032025-064811859", "type": "thesis", "title": "Multielectron Redox in Lithium-Rich, Industrial-Element Sulfides for High Energy Density Lithium-Ion Battery Cathodes", "author": [ { "family_name": "Patheria", "given_name": "Eshaan Salim", "orcid": "0000-0002-2761-8498", "clpid": "Patheria-Eshaan-Salim" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Chan", "given_name": "Garnet K.", "orcid": "0000-0001-8009-6038", "clpid": "Chan-G-K" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "Manthiram", "given_name": "Karthish", "orcid": "0000-0001-9260-3391", "clpid": "Manthiram-Karthish" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "This thesis develops a thermodynamic and electronic framework for lithium-ion battery cathodes and applies it to a new class of high-capacity sulfides composed exclusively of industrially abundant elements.\r\nIt introduces lithium-rich cathodes composed of aluminum, iron, and sulfur that leverage reversible multielectron anion redox, in which the formation and cleavage of sulfur-sulfur bonds enable especially high extents of charge storage.\r\nA core design framework is established linking delithiated-phase stability to accessible electrochemical redox capacity.\r\nThe chemical space is expanded with copper-substituted phases, in which unique copper-sulfur electronic interactions delocalize charge compensation beyond sulfur-sulfur bonds, thereby improving the reversibility of anion redox.\r\nThese materials achieve high energy densities using only industrial elements, offering a promising foundation for next-generation lithium-ion cathodes that address both performance and raw materials constraints.\r\nThus, this thesis advances the long-term goal of building more sustainable energy systems and expanding access to electricity worldwide.", "doi": "10.7907/2pdg-hs94", "publication_date": "2025", "thesis_type": "phd", "thesis_year": "2025" }, { "id": "thesis:16267", "collection": "thesis", "collection_id": "16267", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:12152023-235139391", "primary_object_url": { "basename": "Ware_thesis_final.pdf", "content": "final", "filesize": 24589417, "license": "other", "mime_type": "application/pdf", "url": "/16267/1/Ware_thesis_final.pdf", "version": "v7.0.0" }, "type": "thesis", "title": "Nonaqueous Electrolyte Design for Energy Storage and Electrosynthesis", "author": [ { "family_name": "Ware", "given_name": "Skyler Danielle", "orcid": "0000-0002-3249-1946", "clpid": "Ware-Skyler-Danielle" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Lewis", "given_name": "Nathan Saul", "orcid": "0000-0001-5245-0538", "clpid": "Lewis-N-S" }, { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "3MT Competition (Caltech)" }, { "literal": "div_chem" } ], "abstract": "Electrochemically driven metal redox has enabled advances in both academic and industrial processes, including production of metals from their ores, storage of renewable energy in batteries and fuel cells, and greener chemical synthesis conditions. While many electrochemical reactions are performed in aqueous solutions, applications in energy storage and organic synthesis often require extreme applied potentials that lie outside the electrochemical stability window of water or necessitate water-free conditions to prevent undesirable side reactions. Herein, we develop tailored non-aqueous electrolytes for applications in both energy storage and organic electrosynthesis and analyze the effects of electrolyte composition on interfacial and electrochemical reactions. First, a series of highly concentrated solvate electrolytes is developed for Li-S batteries, and interfacial reactivity between the solvate electrolytes and the Li anode is investigated in detail. The addition of a fluoroether cosolvent limits electrolyte decomposition at the Li surface, improving cycling stability and enabling new high-temperature applications. Next, samarium(III)/(II) redox is investigated in a variety of non-aqueous electrolytes to support an electrocatalytic cycle for samarium-mediated carbon-carbon bond formation. The coordination environment of the samarium salt, which can be tuned through anion exchange between the electrolyte and the samarium precursor, strongly affects the reversibility and reducing power of the samarium redox couple. Third, electrolyte additives are studied to increase the desolvation barrier of Zn\u00b2\u207a. When Zn sacrificial anodes are used in organic electrosynthesis, such additives may prevent deleterious cross-plating of Zn\u00b2\u207a at the cathode. Finally, a detailed guide to troubleshooting metal sacrificial anodes is presented with special attention to issues commonly encountered in reductive electrosynthesis.", "doi": "10.7907/kx7f-2065", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16440", "collection": "thesis", "collection_id": "16440", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:05302024-015407649", "primary_object_url": { "basename": "Zachery_Iton_Caltech_Thesis_2024_V2.pdf", "content": "final", "filesize": 56370845, "license": "other", "mime_type": "application/pdf", "url": "/16440/1/Zachery_Iton_Caltech_Thesis_2024_V2.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Superionic Conduction of Next-Generation Mobile Ions in Solids Enabled by Coordinating Ligands", "author": [ { "family_name": "Iton", "given_name": "Zachery William Benjamin", "orcid": "https://orcid.org/0000-0002-2226-9006", "clpid": "Iton-Zachery-William-Benjamin" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Atwater", "given_name": "Harry Albert", "orcid": "0000-0001-9435-0201", "clpid": "Atwater-H-A" }, { "family_name": "Greer", "given_name": "Julia R.", "orcid": "0000-0002-9675-1508", "clpid": "Greer-J-R" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_eng" } ], "abstract": "Advancements in battery technologies are a critical step towards meeting the growing demand for sustainable energy storage solutions. The development of next-generation battery technologies using \"beyond-Li\" ions, like Na\u207a, K\u207a, Mg\u00b2\u207a, Ca\u00b2\u207a, Zn\u00b2\u207a, and Al\u00b3\u207a, could potentially offer improved performance, safety, and cost-effectiveness over traditional lithium-ion systems. However, the realization of next-generation battery technology based on \"beyond-Li\" mobile ions is limited, in part, due to a lack of understanding of solid state conduction of next-generation ions, which governs ion transport in electrodes, interphases, and solid electrolytes. \u201cBeyond-Li\u201d ions tend to have relatively low mobility in solids due to: (1) the larger ionic radii (Na\u207a, K\u207a, Ca\u00b2\u207a), which limit the accessible migration pathways, or (2) higher charge densities (Mg\u00b2\u207a, Zn\u00b2\u207a Al\u00b3\u207a), which results in strong electrostatic interactions within the solid.
\r\n \r\nThis work discusses several structure-property relationships and structural modifications that are hypothesized to lead to facile conduction of next-generation working ions. A notable discovery is the superionic conductivity of ZnPS3 after exposure to humid environments. Water is introduced into the grain boundaries, thereby enabling Zn\u00b2\u207a ions from the material to migrate and conduct freely in the network of adsorbed water. The introduction of water leads to potential H\u207a, therefore a methodology for decoupling the contributions of Zn\u00b2\u207a and H\u207a in mixed ionic conducting solids using ion-selective EIS, transference number measurements, and deposition experiments is established.
\r\n \r\nFurther extending this approach, superionic conductivity of other next-generation ions in electronically-insulating inorganic solids is achieved by leveraging the established ion exchange/intercalation mechanism of MPS3 (M = Cd, Mn) materials. The mobile cations that are introduced are coordinated with H2O ligands which simultaneously increase the size of the bottlenecks within the migration pathway and screen the charge-dense ions resulting in high mobilities. Potential applications can be extended to water-incompatible systems by replacing the water ligands with aprotic molecules.
\r\n \r\nThese insights contribute significantly to the understanding and development of next-generation battery technologies, representing an important step toward the development of more sustainable and efficient energy storage solutions.
", "doi": "10.7907/fwyd-2w86", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:16161", "collection": "thesis", "collection_id": "16161", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:08212023-202451948", "primary_object_url": { "basename": "Zhang_Caltech_Thesis_Final.pdf", "content": "final", "filesize": 45557113, "license": "other", "mime_type": "application/pdf", "url": "/16161/1/Zhang_Caltech_Thesis_Final.pdf", "version": "v4.0.0" }, "type": "thesis", "title": "Efforts Towards C-C Bond Formations: From Ni Catalysis to Transition-Metal Free Electrolysis", "author": [ { "family_name": "Zhang", "given_name": "Wanji Wendy", "orcid": "0000-0002-6895-9598", "clpid": "Zhang-Wanji-Wendy" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Reisman", "given_name": "Sarah E.", "orcid": "0000-0001-8244-9300", "clpid": "Reisman-S-E" }, { "family_name": "Stoltz", "given_name": "Brian M.", "orcid": "0000-0001-9837-1528", "clpid": "Stoltz-B-M" }, { "family_name": "Fu", "given_name": "Gregory C.", "orcid": "0000-0002-0927-680X", "clpid": "Fu-G-C" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "The selective construction of C-C bonds has been a critical challenge in modern synthetic organic chemistry. Among the numerous methodologies developed, cross-coupling remains an attractive strategy for direct C-C bond formation. Herein, a diverse range of cross-coupling reactions for C-C bond formations are investigated from different perspectives. First, the mechanism of a Ni/cyano-box-catalyzed asymmetric Suzuki alkynylation is studied. The existing data is consistent with a radical chain pathway that is previously proposed for other Ni-catalyzed enantioselective cross-coupling reactions. Next, moving on from the traditional electrophile-nucleophile cross-couplings, we explore Ni-catalyzed reductive coupling of alkyl halides with internal olefins in the presence of a hydrosilane. With judicious choice of the directing group, hydroalkylation of internal olefins can be achieved with high regio- and enantioselectivity. Following that, an electrochemically driven, transition-metal free cross-electrophile coupling reaction is explored as a greener alternative to constructive C(sp\u00b3)-C(sp\u00b3) bonds. Specifically, we focus on improving the Mg sacrificial anode performance in these electroreductive systems. By carefully choosing the electrolyte composition, we are able to manipulate the metal electrode interfaces for a more effective counter electrode. Finally, Al stripping in ethereal solvents is investigated for its application as a sacrificial anode in reductive electrosynthesis. Inspired by Al corrosion chemistry, we are able to achieve bulk Al stripping in THF-based electrolyte by incorporating halide co-supporting electrolytes.
", "doi": "10.7907/czam-9x35", "publication_date": "2024", "thesis_type": "phd", "thesis_year": "2024" }, { "id": "thesis:15279", "collection": "thesis", "collection_id": "15279", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06022023-055053747", "type": "thesis", "title": "Complex Charge Compensation Mechanisms in Lithium-Rich Chalcogenide Cathodes", "author": [ { "family_name": "Zak", "given_name": "Joshua Joseph", "orcid": "0000-0003-3793-7254", "clpid": "Zak-Joshua-Joseph" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Cushing", "given_name": "Scott K.", "orcid": "0000-0003-3538-2259", "clpid": "Cushing-Scott-K" }, { "family_name": "Giapis", "given_name": "Konstantinos P.", "orcid": "0000-0002-7393-298X", "clpid": "Giapis-K-P" }, { "family_name": "Faber", "given_name": "Katherine T.", "orcid": "0000-0001-6585-2536", "clpid": "Faber-K-T" }, { "family_name": "Hadt", "given_name": "Ryan G.", "orcid": "0000-0001-6026-1358", "clpid": "Hadt-Ryan-G" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Lithium-ion batteries have revolutionized the world by enabling long-lasting portable electronics, electrified transportation, and grid storage solutions for renewable energy implementation. However, current commercialized technologies are limited by the one electron transfer per transition metal paradigm utilized by cathode materials that operate with an intercalation-based charge storage mechanism. Finding ways to increase the charge storage capabilities of the cathode into the multielectron regime has long been a focus of research efforts, and involvement of structural anions in the redox has been demonstrated as a promising way to accomplish multielectron storage. Layered lithium-rich oxide materials have been shown to afford dramatic improvements to overall storage capacity but are plagued by complex mechanisms and unwanted side reactions that lead to poor cycling stability and characterization difficulties. This thesis expands upon previous understanding of oxide-based anion redox materials and extends the exploration into sulfide and selenide systems, which allow the study of anion redox without the side processes that affect oxides. First, a dynamic charge compensation mechanism of late group metal-poor, lithium-rich oxide, Li2Ru0.3Mn0.7O3, is uncovered and found to involve an irreversible anion oxidation that leads to involvement of redox states on transition metals previously thought to be unavailable. Second, active electrolyte additives are explored as a method of stabilizing the cathode-electrolyte interface of anion redox material, Li2RuO3. Third, reversible anion redox is demonstrated in alkali-rich sulfides, Li2FeS2 and LiNaFeS2, and proven to occur through oxidation of sulfides (S2-) to persulfides ([S2]2-). Understanding of the structural ramifications of anion oxidation in Li2FeS2 is further expanded through computational and experimental methods. Fourth, the role of metal-anion covalency is systematically investigated through anion substitution of Li2FeS2 with S2-, highlighting the importance of a holistic understanding of changes to the electronic and physical structure of anion redox materials to predict long-term performance. Finally, detailed perspectives and future outlooks on sulfur redox in lithium battery systems are offered with an exhaustive survey of thermodynamically stable binary and ternary persulfide materials.
", "doi": "10.7907/1k50-3811", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" }, { "id": "thesis:16071", "collection": "thesis", "collection_id": "16071", "cite_using_url": "https://resolver.caltech.edu/CaltechTHESIS:06032023-004803929", "primary_object_url": { "basename": "Steve_Kim_Thesis_compressed.pdf", "content": "final", "filesize": 4723734, "license": "other", "mime_type": "application/pdf", "url": "/16071/4/Steve_Kim_Thesis_compressed.pdf", "version": "v8.0.0" }, "type": "thesis", "title": "Design Rules for Multi-Electron Systems in Next-Generation Batteries: From Mg Electrode-Electrolyte Interface to Anion Redox Activation in Li-Rich Sulfides", "author": [ { "family_name": "Kim", "given_name": "Seong Shik (Steve)", "orcid": "0000-0003-2604-6392", "clpid": "Kim-Seong-Shik-Steve" } ], "thesis_advisor": [ { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "thesis_committee": [ { "family_name": "Wang", "given_name": "Zhen-Gang", "orcid": "0000-0002-3361-6114", "clpid": "Wang-Zhen-Gang" }, { "family_name": "Brady", "given_name": "John F.", "orcid": "0000-0001-5817-9128", "clpid": "Brady-J-F" }, { "family_name": "Agapie", "given_name": "Theodor", "orcid": "0000-0002-9692-7614", "clpid": "Agapie-T" }, { "family_name": "See", "given_name": "Kimberly", "orcid": "0000-0002-0133-9693", "clpid": "See-Kimberly" } ], "local_group": [ { "literal": "div_chem" } ], "abstract": "Li-ion batteries (LIBs) have revolutionized the modern world, powering portable electronic devices and more recently realizing electrification of transportation. With more technological advancements that further improved the performance, LIBs also play an important role as one of the most promising energy storage systems in transforming into renewable energy sources and achieving net zero emissions. However, state-of-the-art intercalation-based LIBs are beginning to mature and reach their theoretical capacity limits. To further improve the electrochemical performance of batteries and meet growing demands of energy storage applications, there have been growing efforts to increase the energy density beyond the limits of conventional LIBs. In this thesis, we examine two examples of multi-electron systems\u2013Mg electrolytes and Li-rich sulfide cathode materials\u2013to gain insights and establish design principles.
\r\n\r\nFirst, we explore the magnesium aluminum chloride complex (MACC) electrolyte to study the role of the electrode-electrolyte interface in Mg charge transfer. We demonstrate that MACC electrolyte which normally requires electrolytic conditioning can be chemically activated by the small addition of Mg(HMDS)\u2082. Solution-phase characterization reveals that Mg(HMDS)\u2082 helps prevent the formation of passivating film on the Mg surface by scavenging trace amounts of H\u2082O. Mg(HMDS)\u2082 also reacts with MACC to form free Cl\u207b which decorates the Mg surface which facilitates Mg electrodeposition and stripping.
\r\n\r\nNext, we investigate three different alkali-rich sulfides-LiNaFeS\u2082, LiNaCoS\u2082, and Li1.33-1.33zTi0.67+0.33zVaczS\u2082 - to probe the role of electronic and physical structure in governing reversible anion redox. We demonstrate that cryomilling LiNaFeS\u2082 mitigates particle fracturing by increasing microstrain and reducing crystallite size. Isostructural LiNaCoS\u2082 exhibits more covalent interactions between the transition metal-d and S-p states compared to LiNaFeS\u2082, but undergoes an irreversible conversion reaction. Lastly, Li\u2082TiS\u2083 exhibits no electrochemical activity, but introducing cationic vacancies in Li1.33-1.33zTi0.67+0.33zVaczS\u2082 activates S oxidation. Li1.33-1.33zTi0.67+0.33zVaczS\u2082 is studied further to study first-cycle activation and voltage hysteresis in Li-rich sulfides.
", "doi": "10.7907/v52j-t589", "publication_date": "2023", "thesis_type": "phd", "thesis_year": "2023" } ]