Author ORCID Identifier

https://orcid.org/0000-0001-5264-3583

Date Available

8-10-2023

Year of Publication

2023

Degree Name

Doctor of Philosophy (PhD)

Document Type

Doctoral Dissertation

College

Engineering

Department/School/Program

Chemical and Materials Engineering

First Advisor

Dr. Qing Shao

Second Advisor

Dr. Yang-Tse Cheng

Abstract

The sustainable development of society needs sustainable energy solutions and the mitigation of greenhouse gas emissions. One key subject in this area is the development of safe and efficient ion-based batteries. Moreover, CO2 capture is a crucial pathway in mitigating emissions from the combustion of fossil fuels. Ongoing efforts are to improve both technologies' safety and efficiency. This thesis presents our efforts to conduct computational research on understanding advanced zwitterionic electrolytes and CO2 capture. Chapters 2-4 illustrate the computational research to understand ionic solvation in zwitterionic electrolytes. Solid-state electrolytes are essential for safer batteries. While solid polymer electrolytes have advantages such as high safety standards, flexibility, and ease of processing, they suffer from low ionic conductivity. Zwitterionic (ZW) materials have potential due to their unique structures and properties, offering high ionic conductivity and mechanical strength. However, the understanding of their underlying mechanisms and design principles is limited. Our study investigated the effect of ZW molecules in lithium salts and poly(ethylene oxide)-based (PEO) electrolytes through molecular dynamics simulations. We found that ZW molecules can make small Li+ and large anions diffuse at the same level under an electric field and have two distinct effects on Li+ transport and solvation in PEO electrolytes. ZW molecules can release Li+ from the trapping effect of EO chains, enhancing Li+ transport and slowing down Li+ transport by strong Li+-ZW associations. The accelerating effect becomes stronger as the EO chain length increases. We also studied how the chemical structure of ZW molecules affects their ionic disassociation effect and found that MPC, SB, and CB reduce Li+–EO association in the order of MPC > CB > SB (MPC: 2-methacryloyloxyethyl phosphorylcholine, SB: sulfobetaine ethylimidazole, CB: carboxybetaine ethylimidazole). Our simulations suggest that ZW molecule additives may be beneficial in high Li+ concentration environments. At a low Li+ concentration, all three molecules decrease Li+ diffusion, but at a high Li+ concentration, only SB has this effect. Chapter 5 illustrates our effort to develop quantum computing on CO2 capture. Quantum computing has the potential to enhance the efficiency, accuracy, and capabilities of simulating CO2 capture reactions through increased computational power, precision, and resources. In addition to molecular electronic energies, vibrational properties are crucial for understanding reaction kinetics. However, the anharmonicity effect correlates with the molecule size and plays a substantial role in molecular vibrational properties, which can be challenging to address using classical computing. By employing a variational quantum eigensolver algorithm, this work calculates both the molecular electronic and vibrational energies for the reaction pathways between CO2 and NH3. The study showcased the potential of quantum computing for calculating the vibrational energies of large molecules, thus demonstrating its applications in the study of CO2 capture reactions. In summary, this work illustrates the fundamental relationship between the chemical structures of ZW molecules and their ability to alter the ionic solvation and transport in electrolytes. This relationship can be used to rationalize the design of advanced electrolytes with high ionic conductivity. This work also illustrates the potential of quantum computing in enabling the computation of molecular properties critical for CO2 capture and conversion.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2023.370

Funding Information

This study was supported by the startup fund at the University of Kentucky in 2018.

The research was supported in part by an appointment with the Advanced Manufacturing Office Summer Internships program sponsored by the United States Department of Energy in 2022.

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