Location: Fiber Optics Building, Easton Hub Auditorium
Abstract: The high-rate exchange of lithium ions required for more power and faster charging of Li-ion batteries generates significant stresses and strains in the electrodes that ultimately lead to performance degradation. To date, electrochemically-induced stresses and strains in battery electrodes have only been studied individually and the relative contributions to battery performance/degradation have remained unknown. This seminar describes a new technique to probe the electro-chemo-mechanical response of electrodes by calculating the electrochemical stiffness via coordinated in situ stress and strain measurements. In contrast to the elastic stiffness constants, the electrochemical stiffness is a measure of the potential or capacity dependence of the stress and strain responses of the electrodes. Electrochemical stiffness evolution is characterized in both graphite anodes and lithium manganese oxide (LiMn2O4) cathodes. Tracking changes in the electrochemical stiffness provides new insights into the effects of individual phase changes on the mechanical responses of as well as insight into kinetic limitations on lithium insertion and removal from the host electrode. Overall, this novel approach offers a new analytical tool for interrogating advanced battery materials, enabling the design and assessment of high-power and high-rate battery materials.
Bio: Nancy Sottos is the Donald B. Willet Professor of Engineering in the Department of Materials Science and Engineering at the University of Illinois Urbana-Champaign. She is also a co-chair of the Molecular and Electronic Nanostructures Research Theme at the Beckman Institute. Sottos started her career at Illinois in 1991 after earning a Ph.D. in mechanical engineering from the University of Delaware. Her research group studies the mechanics of complex, heterogeneous materials such as self-healing polymers and advanced composites, specializing in characterization of deformation and failure in these material systems. Sottos’ research and teaching awards include the ONR Young Investigator Award (1992), Outstanding Engineering Advisor Award (1992, 1998, 1999 and 2002), the R.E. Miller award for Excellence in Teaching (1999), University Scholar (2002), the University of Delaware Presidential Citation for Outstanding Achievement (2002), the Hetényi Best Paper Award from the Society for Experimental Mechanics (2004, 2016), Scientific American's SciAm 50 Award (2008), the M.M. Frocht and B.J. Lazan awards from the Society for Experimental Mechanics (2011), the Daniel Drucker Eminent Faculty Award (2014) and an IChemE Global Research Award (2016). She is a Fellow of the Society of Engineering Science and the Society for Experimental Mechanics and serves on the editorial boards for Experimental Mechanics and Composites Science and Technology.