Abstract
There is a critical need to gain insight into the fundamentals of electron/charge/mass transfer mechanisms and reaction kinetics which define the functional basis for a range of electrochemical energy storage technologies (e.g. batteries, fuel cells, and supercapacitors). In situ electrochemical cell scanning/transmission electron microscopy (in situ ec-S/TEM) is an emerging in situ TEM characterization method that utilizes the concept of membrane-type liquid flow cells but with the extended versatility to probe nanoscale electrochemical related phenomena within a thin layer of electrolyte. Recent advances in MicroElectroMechanicalSystems (MEMS) based fabrication methods allow for the direct fabrication of silicon microchip devices that support thin electron transparent silicon nitride viewing membranes with integrated working, counter and reference electrodes. These microchip devices serve as a platform for 1) sealing volatile liquid electrolytes from the high vacuum environment of the TEM, 2) performing quantitative electrochemical measurements, and 3) simultaneously characterizing electrochemically stimulated processes through imaging, diffraction, and spectroscopy. In this presentation, we will define the approach needed to obtain quantitative electrochemistry measurements in small-scale electrochemical liquid cells through cyclic voltammetry, chronopoteniometry, chronoamperometry, and electrical impedance spectroscopy while discussing the practical uses, limitations and issues with experimental artifacts. Then we will show how in situ ec-S/TEM can be utilized to investigate specific issues that currently limit performance and device functionality of batteries, fuel cells, and supercapacitors.
Bio
Raymond R. Unocic is a R&D Staff Scientist in ORNL’s Center for Nanophase Materials Science Division. Prior to ORNL, he received his B.S. in Metallurgical Engineering from The Ohio State University, M.S. in Materials Science and Engineering from Lehigh University, and Ph.D. in Materials Science and Engineering from The Ohio State University (2008). In 2009 he joined ORNL under the prestigious Alvin M. Weinberg Early Career Fellowship then transitioned to Staff Scientist in 2011. His research is focused on the utilization of advanced electron microscopy characterization methods (aberration corrected STEM, HRTEM, EELS, EFTEM, EDS, and in situ S/TEM) for materials research. His current research interests are centered on the development and application of novel in situ electrochemical S/TEM characterization techniques to probe site-specific chemical and electrochemical processes for energy