Date on Master's Thesis/Doctoral Dissertation

5-2022

Document Type

Doctoral Dissertation

Degree Name

Ph. D.

Department

Chemical Engineering

Degree Program

Chemical Engineering, PhD

Committee Chair

Sathitsuksanoh, Noppadon

Committee Member

Willing, Gerold A.

Committee Member

Jaeger, Vance W.

Committee Member

Thompson, Lee

Author's Keywords

Lewis-acid; oxygen-vacancy; biomass; catalysis; MOF; Li-Se battery

Abstract

My long-term goal is to develop catalytic systems to produce renewable energy for a sustainable society. The overall research objective of my dissertation is to advance understanding of Lewis acidic materials for (1) conversion of renewable lignin into phenolics and (2) enhanced cycling stability of lithium metal batteries to safely store renewable electricity from wind and solar, thereby laying the groundwork for our transition to a sustainable society. Petroleum is a conventional feedstock for current transportation fuels (gasoline, diesel, and jet fuels). However, petroleum is a finite resource and produces greenhouse gases (CO2 and CH4) upon processing, which contributes to climate change. Therefore, we need to develop ways to tap into alternative feedstocks. Many researchers have investigated the use of catalytic conversion of lignocellulosic biomass to produce biofuels (bioethanol). During bioethanol production, carbohydrates (cellulose and hemicellulose) are digested to produce bioethanol. The residual lignin is left behind. The ability to catalytically convert lignin into high-value chemicals will incentivize biorefineries and promote a sustainable bio-economy. Electricity is another renewable energy that can be produced from wind and solar. The major challenge in using electricity-driven transportations (electric vehicles) lies in their storage in lithium metal batteries. However, chemical and electrochemical reactions in conventional lithium-metal batteries are not stable. The movement of undesired anions promotes capacity decay and hazardous lithium dendrite growth. As a result, these batteries have short lives and short-circuiting, which leads to fire and explosion. The ability to control the reactivity of the ions in the electrolytes will enable safety and promote future electric vehicles for a cleaner environment. My dissertation focuses on the development of Lewis acidic materials to address the challenges in (1) lignin upcycling and (2) the safety and cyclability of lithium metal batteries. First, lignin is an oxygen-rich phenolic polymer. To efficiently release the phenolic monomers from lignin, I developed the Lewis acid catalysts in the form of oxygen vacancies to activate the oxygen functionality of lignin. Second, I grafted the Lewis acidic metal-organic frameworks (MOFs) onto the polypropylene separator to immobilize the TFSI- anions in conventional electrolytes (1M LiTFSI in organic solvents). The developed materials restrict the mobility of anions and polyselenides, thereby improving the lithium-selenium batteries' capacity retention and cycling stability. I divided this dissertation into six chapters to cover background about Lewis acidic materials and their uses for catalytic lignin upgrading and lithium-selenium batteries. The first four chapters of this dissertation describe the engineering/development of the Lewis acidic material for the catalysis of bioderived organics, lignin. Then, chapter five describes the incorporation of the Lewis acidic MOFs into a polypropylene separator to improve battery capacity and safety. Incorporating the Lewis acidic MOFs controlled ion transport properties, thereby restricting the mobility of undesired anions and polyselenides and improving capacity retention in lithium-selenium batteries. Finally, Chapter six suggests future research directions to create next-generation alkali metal-based batteries that are safe and powerful to face future challenges for developing a sustainable carbon zero society.

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