Materials Science Research Lecture
***Refreshments at 3:45pm in Noyes lobby
Abstract:
High energy-dense battery applications rely on layered oxide cathodes; however, the fundamental redox mechanism has not been clarified even for the first generation LiCoO2-based materials, and overcoming the energy density bottleneck remains a formidable challenge. Conventional wisdom defines low-voltage redox as centered on cations , and high-voltage redox as formation of oxidized oxygen species. Here, through in-situ and ex-situ spectroscopy, guided by theoretical modeling, we show that oxide cathodes, represented by LiCoO2 and LiNiO2, operate through enhancement of delocalized negative charge transfer (NCT) ground states upon charging throughout the whole voltage range. NCT inherently engages high covalency and oxygen holes, leading to optimized performance without conventional redox centers or oxygen dimer formations. World-first, full-edge imaging-mode resonant inelastic X-ray scattering concludes the origin of irradiation-induced O2 features, which emergence indicates a stability threshold for oxygen hole density. Our NCT-based redox mechanism resolves many long-standing controversies and provides a roadmap for high energy density electrode design.
More about the Speaker:
Professor Devereaux received his Ph.D. in Physics from the University of Oregon in 1991, M.S. from University of Oregon in 1988, and B.S from New York University in 1986.
Professor Devereaux is a professor in Materials Science & Engineering and Photon Science at SLAC National Accelerator Laboratory and Stanford University, and a Senior Fellow of the Precourt Institute for Energy. He was formerly the Director of the Stanford Institute for Materials and Energy Sciences (SIMES) from 2011-2020.
Professor Devereaux was a Post-doctoral Fellow at the Max Planck Institut, Stuttgart, (1991-1993), a Post-doctoral Fellow at the University of California, Davis, CA, (1993-1996), an Assistant Professor at The George Washington University, Washington, DC, (1996-1999), and an Associate Professor (1999-2006) and Professor (2006-2007) at the University of Waterloo, Waterloo, ON, Canada
His main research interests lie in the areas of theoretical condensed matter physics and computational physics. His research effort focuses on using the tools of computational physics to understand quantum materials. The goal of his research is to understand equilibrium and ultrafast non-equilibrium electron dynamics via a combination of analytical theory and numerical simulations to provide insight into materials of relevance to energy science. His group carries out numerical simulations on SIMES' high-performance compute cluster, the National Energy Research Scientific Computing Center (NERSC), and other US computational facilities. The specific focus of the group is the development of numerical methods and theories of photon-based spectroscopies of strongly correlated quantum materials and novel materials for energy storage.