Kristen Abels PhD Thesis Defense

Kristen Abels
PhD Candidate
Chemical Engineering
Academic advisor: William Tarpeh

Abstract: "While the clean energy transition is reducing society’s reliance on hydrocarbon fuels, it is increasing our reliance on elements that are critical to renewable energy technologies (e.g., lithium, nickel, cobalt). This increased demand brings about the dual challenge of (1) increasing supply via recovery from unconventional sources, and (2) designing more energy-efficient separation and purification processes to ensure that supply chains align with the clean energy future that they intend to support. My dissertation research has focused on the design of novel polymeric membranes and membrane processes to support a circular lithium economy. This work spans length scales from material synthesis and fundamental ion transport studies to process design, bench-scale validation, and systems-level life cycle and technoeconomic assessment.

In my doctoral research, I have developed a platform polymer synthesis and characterization workflow that has enabled the systematic study of structure-function relationships influencing ion transport within polymeric membranes functionalized with ion-coordinating ligands. This work has revealed structure-performance trends that guide rational material design for complex ion separation applications and has also highlighted a subset of pyridyl-functionalized membranes as promising candidates for lithium/cobalt/nickel separations for battery recycling. At the device innovation level, a cross-disciplinary collaboration with colleagues from the Department of Materials Science Engineering at Stanford University and SLAC National Accelerator Laboratory involved the design of thin-film coated battery separators to bring lithium sulfur batteries closer to market readiness. In this work, a new thin film cation exchange membrane chemistry was engineered to mitigate polysulfide shuttling – thereby addressing the major challenge affecting the long-term stability of lithium-sulfur batteries. Finally, at the process- and systems-design level, the design, bench-scale validation, modelling, and lifecycle and technoeconomic assessment was performed to evaluate a novel Donnan dialysis process for low-energy lithium brine concentration in direct lithium extraction applications."