Abstract

Next-generation batteries with improved microstructure and performance are on their way to meet the market demands for high-energy and power storage systems. Among different types of batteries, Li-ion batteries remain the best choice for their high energy density and long lifetime. There is a constant but slow improvement in Li-ion batteries by developing new materials and fabrication techniques. However, further improvements are still needed to meet government and industry goals for cost, cycling performance, and cell lifetime. A fundamental understanding of particle-level interactions can shed light on designing new porous electrodes for high-performance batteries. This is a complex problem because electrodes have a multi-component, multi-phase microstructure made through multiple fabrication processes (i.e., mixing, coating, drying, and calendering). Each of these processes can affect the final microstructure (particle and pore locations) differently. This work seeks to understand the porous microstructure evolution of Li-ion electrodes during the drying and calendering fabrication processes by a combination of modeling and experimental approaches. The goal is to understand the mechanisms by which the electrode components and fabrication processes determine the battery microstructure and subsequent cell performance. A multi-phase smoothed particle (MPSP) model has been developed on a publically available simulation platform known as LAMMPS. This model was used to simulate particle-level interactions and predict the mechanical and transport properties of four fabricated electrodes (i.e. a graphite anode and three traditional metal oxide cathodes). One challenge was to include different electrode components and their interactions and relate them to physical properties like density and viscosity that can be measured experimentally. Another challenge was to generate required electrode property data for model validation, which in general was not found in the literature. Therefore, a series of experiments were conducted to provide that information, namely slurry viscosity, electronic conductivity, porosity, tortuosity, elastic modulus, and electrode crosssections. Understanding these properties has value to the battery community independent of their use in this study. The MPSP model helps us explain observed transport heterogeneity after calendering but brings up new questions about the drying process that have not been addressed in previous works. Therefore, the drying fabrication step was studied experimentally in more detail to fill this knowledge gap and explain our simulation results. The MPSP model can also be used as a predictive tool to explore the design space of Li-ion electrodes where conducting the actual experiments is very challenging. For example, the distinct effect of particle size, shape, orientation, and stiffness on electrode transport and mechanical properties are difficult to determine independently, and therefore this model is an ideal tool to understand the effect of these properties. The final model, which is publically available, could be used with adjustments by future workers to test new materials, fabrication processes, or electrode design (e.g., a multi-layered structure).

Degree

PhD

College and Department

Ira A. Fulton College of Engineering and Technology; Chemical Engineering

Rights

https://lib.byu.edu/about/copyright/

Date Submitted

2021-12-22

Document Type

Dissertation

Handle

http://hdl.lib.byu.edu/1877/etd12008

Keywords

Li-ion battery fabrication, heterogeneity, electronic conductivity, tortuosity, Young's modulus, microstructure prediction

Language

english

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