Dr. Omer CaprazUniversity of Illinois at Urbana-Champaign
Rechargeable Li-ion batteries are electrochemical energy storage devices in which lithium ions are cycled between two electrodes, and they have been widely commercialized in portable electronics. However, more powerful and faster charging Li-ion batteries are required in more demanding applications such as electrical vehicles. The higher rate-exchange of lithium ions generates significant electrochemically-induced stresses and strains in the electrodes that ultimately lead to performance degradation. Stress and strain developments in battery electrodes during electrochemical cycling have only been studied individually. The relative contributions of stress and strain evolution to battery performance and degradation modes have remained unknown. In this presentation, I will first describe a new technique to probe the electro-chemo-mechanical responses of Li-ion electrodes by calculating the electrochemical stiffness via coordinated in situ stress and strain measurements in lithium manganese oxide (LiMn2O4) cathodes. In contrast to elastic stiffness constants, electrochemical stiffness is a measure of the relative stress and strain responses of the electrodes at a particular point during electrochemical cycling. Tracking changes in electrochemical stiffness reveals underlying mechanisms governing kinetic limitations on lithium insertion and removal from the electrode as well as bulk property changes on the mechanical responses. Second, I will present the effects of various interfacial coatings on the strain generation in the Li-ion electrodes. In situ strain measurements provide new insight into the electrochemical-induced volumetric changes in electrodes also provide guidance to reduce strain and capacity fade in Li-ion electrodes by employing material-based strategies. Finally, I will briefly discuss future strategies to investigate and control electro-chemo-mechanical responses in the next generation electrochemical energy conversion and storage devices.
Dr. Çapraz graduated from Middle East Technical University (Ankara, Turkey) with a bachelor’s degree in Chemical Engineering in 2010. In December 2014, He received his Ph.D. degree in Chemical and Biochemical Engineering with a Mechanical Engineering minor from Iowa State University. During his Ph.D. studies, he investigated nano-scale mechanical deformations during the formation of porous anodic oxide films and stress-corrosion cracking. He is currently a post-doctoral researcher in the Beckman Institute at the University of Illinois at Urbana-Champaign, working with Prof. Nancy Sottos and Prof. Scott White. His post-doctoral studies have focused on the understanding and controlling of chemo-mechanical degradation modes in Li-ion batteries.
Host: Dr. Reza Shahbazian-Yassar
For more information, please contact Prof. Reza Shahbazian-Yassar at email@example.com.