Rechargeable lithium-ion batteries are a staple of modern society, providing power to a significant portion of the world's electronics and rapidly replacing older power sources. The advent of widely available electric cars with batteries of up to 200 kWh, with an increasing emphasis on fast charging, has only increased their importance. Lithium-ion battery electronic and ionic properties are largely determined by the microstructure of the battery electrode film and can be heavily influenced by relatively small variations in film makeup, including the formation of voids or distribution of carbon and binder. Prior to this research, electrical properties, which are some of the most important characteristics to battery cost, performance, and safety, were either difficult or, in the case of contact resistance, impossible to directly measure. This dissertation focuses on the development and use of a micro-surface probe for measurement and mapping of lithium-ion battery film electronic characteristics. The measurement apparatus, inversion and mapping routines, and experimental data presented provide manufacturers and researchers with a better understanding of battery heterogeneity and the influence of microstructure on electrical properties. The micro-surface probe was used to map spatial variation on both a macro and micro scale; compare physical, electrical, and ionic properties; and validate tests that were previously used to estimate electronic parameters. Experiments on commercial-quality battery electrode films showed higher micro-heterogeneity than was previously assumed by a significant margin. Additionally, electronic and ionic properties were shown to not always be inversely related and some physical explanations for observed variation were explored. Macro-variations were measured and shown to exist across electrode films which were previously assumed to be uniform. Finally a comparison to the mechanical peel test, a common test used in industry as a proxy measurement of electrical contact resistance, proved the peel test to be inconclusive and showed that it will not always accurately reflect electrical properties of films. Direct measurements of both electrical conductivity and contact resistance provide a new and important tool to advance understanding and development of lithium-ion batteries. The magnitude of the measured resistivities and their significant variation demonstrates that a better understanding of film properties is needed and will significantly influence our understanding of modern battery parameters and the effects of manufacturing techniques on battery performance.
| Identifer | oai:union.ndltd.org:BGMYU2/oai:scholarsarchive.byu.edu:etd-10432 |
| Date | 06 April 2022 |
| Creators | Vogel, John Eric |
| Publisher | BYU ScholarsArchive |
| Source Sets | Brigham Young University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
| Rights | https://lib.byu.edu/about/copyright/ |
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