Improving the Performance of Energy Storage Devices via Anionic Redox Chemistry
Iwnetim Abate (Tim)
4th year PhD student in Materials Science & Engineering at Stanford University
Zoom Password: matter_fun
Abstract: Increasing the practical energy density of battery materials is a crucial part of the global transition towards clean and renewable energy. In conventional lithium- and sodium-ion cathode materials, such as LiCoO2, transition metals (i.e. Co) are redox centers during cycling, enabling alkali metal ion extraction/insertion. Recently, redox activity in oxygen (anionic redox) has been shown to have the potential to significantly improve cell energy density as it can provide substantial additional capacity beyond that afforded by most transition metal redox couples. However, this additional capacity from anionic redox has come at the expense of reduced reversibility in the form of voltage hysteresis and voltage fade. In this talk, first, I will describe the mechanism responsible for the reduced reversibility in anionic redox active cathode materials. Second, I will show how the structure of the oxygen sub-lattice in a cathode material can be tuned to avoid voltage hysteresis. Finally, I will discuss a set of actionable design rules for harnessing the extra capacity from anionic redox reversibly in intercalation electrodes. These findings have the potential to accelerate the commercialization of cathode materials with enhanced performance.
Bio: Iwnetim (Tim) is a 4th year PhD student in Materials Science & Engineering at Stanford University and is co-advised by Prof. William Chueh and Prof. Thomas Devereaux. His research aims at improving the energy capacity of batteries to meet the ever-growing global demand for energy storage. To this end, his work combines X-ray and electrochemical characterization with quantum mechanical simulations to design better Lithium and Sodium-ion batteries. Prior to joining Stanford, he worked at IBM Alamden and Los Alamos National Laboratory. Tim obtained his B.S. in physics with minors in mathematics and economics from Minnesota State University Moorhead.
Reversible phase engineering via lithium intercalation
4th year PhD student in the labs of Prof. Aaron Lindenberg and Prof. William Chueh, Stanford University
Abstract: Advances in the engineering and dynamic control of material properties are a key component for technological progress in areas such as computation, optics and actuation. The chemical composition and atomic arrangement of a material are the main aspects determining its functionality. In this talk, I introduce a novel nano-battery platform with which we establish electrochemical lithium intercalation as a pathway to precisely control the lithium concentration in individual transition metal dichalcogenide (TMD) flakes, a class of layered materials with the potential to revolutionize nanoelectronics. In tungsten ditelluride, a TMD with exotic symmetry-controlled quantum, topological, and ferroelectric properties, this control over the composition LixWTe2 allows reversible switching between the pristine phase and a newly discovered, lithium-induced crystallographic phase. X-ray diffraction (XRD) and density functional theory studies reveal a large-magnitude lattice expansion, relative sliding of the layers and a symmetry different from any known TMD in this novel phase. Concurrent single-flake electrochemistry and operando X-ray diffraction experiments demonstrate dynamic, highly reversible structural control over the material. The talk concludes with preliminary results on the ultrafast structural dynamics of LixWTe2 after excitation with ultrashort light pulses, measured by ultrafast electron diffraction at different stages of the in situ lithiation process.
Bio: Philipp is a 4th year PhD student in the labs of Prof. Aaron Lindenberg and Prof. William Chueh. He studies ion intercalation-induced phase transitions and ionic motion in layered materials on atomic length and time scales. His research combines nanofabrication and electrochemistry with ultrafast spectroscopy and diffraction techniques.
Prior to joining Stanford in 2016, Philipp worked on different research projects around the world, ranging from plasma physics (Germany), manufacturing optimization (South Africa) to electron holography and gas sensing (Japan); he holds a Diplom degree in Materials Science from TU Dresden. When not in the lab, Philipp likes to spend his time outdoors, hiking, mountain biking and backpacking.