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Dissertation Proposal Defense – Matthew G. Boebinger
MSE Grad Presentation
Monday, April 23, 2018 - 3:00pm
Committee Members: Prof. Matthew McDowell, Advisor, MSE Prof. Josh Kacher, MSE Prof. Meilin Liu, MSE Prof. Gleb Yushin, MSE Prof. Ting Zhu, ME/MSE
“In Situ Examination of Nanoscale Reaction Pathways in Battery Materials”
In an effort to engineer cheaper, safer and more energy-dense batteries, new materials must be developed to store and transport active ions. However, the electrochemical reaction mechanisms of these materials must be understood and controlled to maximize reversibility during charge and discharge. The objective of this proposal is to use in situ transmission electron microscopy (TEM) to understand nanoscale reaction mechanisms and degradation processes in high-capacity electrode materials for Li-, Na- and K-ion batteries, as well as Li-ion conducting ceramic electrolytes. Na- and K-ion batteries are promising due to their low cost. However, the more substantial volumetric changes that these electrode materials undergo during reaction decreases the cyclability of these systems. For the continued development of these battery systems, it is critical to understand how the larger Na+ and K+ ions effect the nanoscale phase transformations of these reactions to improve reversibility of these battery systems. In addition, recent progress has been made towards engineering solid electrolytes for use in novel all-solid-state Li batteries with improved safety and higher energy density. However, the growth of a high-impedance interfacial phase at the Li metal – ceramic electrolyte interface is a challenge that has hindered development. In both of these cases, a better understanding of the structural and chemical evolution of these materials during reaction is needed. The first portion of this proposal is focused on using in situ experiments to understand the nanoscale transformation pathways in different battery materials during reaction with Li+, Na+ and K+ ions. The materials studied (Cu2S, FeS2 and Sb) show interesting and counter-intuitive phase evolution and mechanical degradation behavior when reacting with the alkali ions of different sizes. The second portion of the proposal is focused on investigating interfacial phase transformations between lithium metal and oxide/phosphate solid electrolyte materials. These experiments will be conducted in combination with macroscale characterization and electrochemistry techniques to draw connections between the nanoscale transformations and overall electrochemical behavior of these battery systems.