SUBJECT: Ph.D. Dissertation Defense
BY: Sang Yun Han
TIME: Thursday, April 1, 2021, 10:00 a.m.
PLACE: Virtual, N/A
TITLE: Creating Structured Materials using Alkali Metals as a Processing Agent and their Application in Energy Storage Systems
COMMITTEE: Dr. Matthew McDowell, Chair (ME/MSE)
Dr. Ting Zhu (ME)
Dr. Hailong Chen (ME)
Dr. Lee Seung Woo (ME)
Dr. Michael Filler (ChBE)


The aims of this thesis are i) to develop processing routes using alkali metals to create microstructured materials and ii) to understand the electro-chemo-mechanical properties of these materials in energy storage systems. Materials that have nanowire and porous morphologies have inherent advantages that arise from their structure, such as improved optical, electrical, and mechanical properties. However, there are limited pathways to create structured metals for use in devices. This work first investigates the use of lithium metal as a processing agent to create advanced material structures at low temperatures. Li is highly reactive and can form alloys with various metals at relatively low temperature (<300 °C), and it can easily be removed from Li alloys (electro)chemically. Here, we show how processing conditions can be controlled during chemical alloying and dealloying to fabricate different nano- and microscale structures, including nanowires or bicontinuous porous metal monoliths. These structured materials are further investigated as electrodes in solid-state batteries, revealing the relationship of the material structure and porosity to cycling stability. Finally, a force measurement system was constructed and used to investigate the evolution of stress within solid-state batteries as a function of the composition and structure of these metallic anodes, providing important insight into subtle structural changes during electrochemical cycling and degradation behavior. This work has presented new methods to fabricate structured metals and advanced our understanding of how these materials behave in next-generation energy storage systems with high energy density. To join: