2025 Theses Doctoral

Advanced Materials: Lithium-ion Battery Anodes and Enriched Isotopes

Wild, Joseph Francis

Advanced materials exist on the leading edge of technology. The development of materials in the form of superior properties, scalable production, and fundamental scientific understanding leads to both anticipated and unforeseen advancements across multiple fields of science and technology.

This doctoral dissertation explores two classes of advanced materials: nanostructured carbon-silicon composites for lithium-ion battery anodes and enriched isotopes for nuclear fusion and medical applications. Both areas address pressing global challenges - energy storage for sustainable electrification and the availability of isotopically pure materials for nuclear energy and radiopharmaceuticals.

The first class of materials, discussed in Chapter 3, focuses on the design and synthesis of micron-sized nanoporous silicon-carbon composites for high-performance lithium-ion battery anodes. Silicon offers a theoretical capacity over ten times greater than that of conventional graphite anodes but suffers from severe volume expansion and unstable solid-electrolyte interphase (SEI) formation. Here, a scalable chemical vapor deposition (CVD) process is developed to form ultrathin silicon layers on nanoporous carbon, mitigating fracture and improving electrochemical stability. The resulting composite exhibits high specific capacity (>1400 mAh/g), stable cycling (<5% decay per 100 cycles), and air/water stability, making it an attractive candidate for next-generation lithium-ion batteries. The corresponding NMC-(Si-C) full cells demonstrate promising performance, with the potential to approach 400 Wh/kg - a threshold that could significantly impact electric vehicle (EV) range and adoption.

The second class of materials, explored in Chapters 4 and 5, are isotopically enriched elements, which underpin technologies such as nuclear fusion, radiopharmaceuticals, and quantum computing. While enriched isotopes are crucial to these fields, their separation remains highly inefficient due to the nearly identical chemical behavior of isotopic variants. Traditional methods such as electromagnetic isotope separation (EMIS) and gas centrifugation are limited by low throughput and applicability only to gaseous compounds, respectively, leaving many elements - including lithium, calcium, and lanthanides - without practical enrichment pathways.

To address this challenge, a new approach, liquid-phase centrifugation, is introduced as a highly efficient, scalable, and safe method capable of enriching any element on the periodic table. The fundamental equations governing isotope separation via liquid centrifugation are derived, validated experimentally across multiple isotopic systems (Ca, Mo, O, H, and Li), and extended to large-scale practical considerations. Experimental results show single-stage selectivities of 1.046-1.067 per unit mass difference, surpassing the capabilities of many existing enrichment techniques. Furthermore, the potential for countercurrent liquid centrifugation is evaluated, demonstrating that throughput and efficiency can be dramatically increased through staged cascading, analogous to gas centrifuge systems. These findings suggest that liquid-phase centrifugation is well-positioned to recast isotope enrichment, greatly increasing global production capacity for key isotopes used in nuclear energy, medical imaging, and fundamental research.

Together, the advancements presented in this dissertation contribute to sustainable energy storage solutions and the development of scalable isotope separation technologies, providing necessary innovations for electric vehicles, nuclear fusion, and medical applications. By addressing fundamental material and process limitations, this work advances the long-standing pursuit of efficient, high-performance materials for the future of energy and science.