Brown University School of Engineering

Joint Materials/Solid Mechanics Seminar Series: "Atomic-resolution study of energy conversion and storage materials"

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Monday, March 17, 2014 4:00pm - 5:00pm

Robert F. Klie, Nanoscale Physics Group, University of Illinois at Chicago. While recent advances in energy conversion and storage have revolutionized the consumer electronics market, we still lack a fundamental understanding of the effects that currently limit the devices’ efficiencies and lifetimes. Aberration-corrected scanning transmission electron microscopy (STEM) is becoming one of the most promising characterization tools to study the effects of repeated charging/discharging cycles on electrode aging in Li-ion battery materials or defects in solar-cell devices, due to the wide-range of techniques available on advanced STEM instruments, including the direct imaging of both heavy and light elements, energy-dispersive X-ray and electron energy loss (EEL) spectroscopies and a variety of in-situ methods. Here, I will present the latest results from the new probe aberration-corrected cold-field emission JEOL JEM-ARM200CF at the University of Illinois at Chicago (UIC), which allows in-situ characterization with 78 pm spatial resolution and an energy resolution of 350 meV in the temperature range between 10 K and 1,300 K using a variety of in-situ heating, cooling, tomography and electrical feedback holders. In particular, I will focus on Li2MnO3-based cathode materials for Li-ion battery applications and CdTe grain boundaries for poly-crystalline solar-cell devices. The experimental results will be combined with first-principles density functional theory calculations, as well as electrochemical and transport property measurements to develop an atomic-scale model of the role of defects, interfaces and grain boundaries in these highly complex materials.