Mesoscale Physics and Stochastics in Energy Storage

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1 Mesoscale Physics and Stochastics in Energy Storage Partha P. Mukherjee School of Mechanical Engineering, Purdue University Advances in electrochemical energy storage are critical toward enabling vehicle electrification, renewable energy integration into the electric grid, and powering myriad portable electronic devices. Recent years have witnessed an urgent need to accelerate innovation toward realizing improved and safe utilization of high energy and power densities, for example in lithium-ion batteries for electric vehicles. These are complex, dynamical systems which include coupled processes encompassing electronic/ionic/diffusive transport in solid/electrolyte phases, electrochemical reactions, diffusion induced stress generation, and thermal transport in porous electrodes. Fundamental understanding of the underlying transport, chemistry, microstructure, and interface interactions in porous electrode architectures is of critical importance. This talk will highlight the role of mesoscale complexations and stochasticity with examples from intercalation and conversion battery chemistries. Bio: Partha P. Mukherjee is currently an Associate Professor of Mechanical Engineering at Purdue University. Before joining Purdue, he was an Assistant Professor and Morris E. Foster Faculty Fellow of Mechanical Engineering at Texas A&M University (TAMU). Prior to starting his academic career at TAMU in 2012, he worked for four years in the U.S. Department of Energy Labs; a staff scientist ( ) at Oak Ridge National Laboratory, and a Director s research fellow ( ) at Los Alamos National Laboratory. He received his Ph.D. in Mechanical Engineering from the Pennsylvania State University in Prior to PhD studies, he worked as an engineer for four years at Fluent India Pvt. Ltd, a fully-owned subsidiary of Fluent Inc., currently Ansys Inc. He received the Scialog Fellows recognition, visiting faculty lectureship at the International Center for Theoretical Physics (ICTP, Trieste, Italy), TMS Young Leaders Award, emerging investigator distinction from the Institute of Physics, to name a few. His research interests are focused on mesoscale physics and stochastics of transport, chemistry and microstructure interactions, including an emphasis in the broad spectrum of energy storage and conversion.

2 Nanoscale Colocalization of Fluorogenic Probes Reveals the Role of Oxygen Vacancies in the Photocatalytic Activity of Tungsten Oxide Nanowires Bryce Sadtler Department of Chemistry, Washington University in St. Louis Defect engineering is a strategy that has been widely used to design active semiconductor photocatalysts. However, understanding the role of defects, such as oxygen vacancies, in controlling photocatalytic activity remains a challenge. In this talk I will discuss the use of chemically triggered fluorogenic probes to study the spatial distribution of active regions in individual tungsten oxide nanowires using super-resolution fluorescence microscopy. Through quantitative, coordinate-based colocalization of probe molecules activated by the same nanowires, we demonstrate that the nanoscale regions most active for the photocatalytic generation of hydroxyl radicals also possess a greater concentration of oxygen vacancies. Furthermore, we show how the distribution of active regions in a tungsten oxide nanowire is altered based on the ligands bound to its surface. These findings indicate that oxygen vacancies activate water molecules adsorbed onto the semiconductor surface to catalyze the generation of hydroxyl radicals, an important chemical intermediate in the production of fuels from sunlight.

3 Machine Learning Applications in Materials Data and Imaging Dane Morgan Department of Materials Science and Engineering, University of Wisconsin Madison, WI USA Machine learning methods are impacting almost every aspects of our lives, and science and engineering are no exception. Here we briefly discuss some of the areas where machine learning is changing how we do Materials Science and Engineering, and some specific applications we have pursued in our group. The first application is to modeling diffusion coefficients, and demonstrates the ability of elemental properties to capture key aspects of the physics of atomic transport and predict diffusion coefficients. The second application is to modeling irradiation hardening effects in steels for nuclear applications, and demonstrates that simply knowing composition and irradiation conditions can allow quantitative prediction of irradiation response. Both these applications make use of kernel regression approaches and I will discuss some of the challenges of these and related approaches in assessing model errors and domain of applicability. The third application is to automating the reading of electron microscopy images to assess damage from irradiation in nuclear steels, and demonstrates that machine vision tools can successfully count defects and measure their dimensions. This work suggests that many image analysis activities in materials characterization may soon be largely automated. Dane Morgan obtained a PhD in Physics from U.C. Berkeley in 1998, was a Postdoctoral Researcher and Research Scientist at MIT until 2004, and is now a Professor in Materials Science and Engineering and co-director of the Wisconsin Materials Institute at the University of Wisconsin, Madison. His work combines thermostatistics, thermokinetics, and informatics analysis with atomic scale calculations to understand and predict materials properties. A major focus of Morgan s work is energy applications, including fuel cells, batteries, and nuclear materials, but he also works in the areas of high-pressure geoscience and defect properties in semiconductors. Morgan has done extensive consulting work for industry and in 2011 served as vice president of research at Pellion Technologies, a startup energy technology company. Morgan is presently training or has graduated/trained over 60 graduate students and postdoctoral researchers, and worked with approximately 100 undergraduates in research. He is the Harvey D. Spangler Professor of Engineering and a University of Wisconsin Vilas Scholar, received the University of Wisconsin Award for Mentoring Undergraduates in Research, Scholarly and Creative Activities and the Harvey Spangler Award for Innovative Teaching and Learning Practices for his undergraduate mentoring activities, has won multiple top paper awards, and has published over 250 papers in materials science.

4 Designing Stable Perovskites for Energy Applications One Atom at a Time Rohan Mishra Department of Mechanical Engineering and Materials Science, Washington University in St. Louis rmishra@wustl.edu Advances in first-principles calculations based on density-functional theory now make it possible to successfully describe the atomic-scale properties of real materials with defects and imperfections. Concurrent advances in scanning transmission electron microscopy enables imaging and spectroscopy of the atomic and electronic structure of materials with unprecedent spatial and energy resolution. Naturally then, the combination of theory and microscopy provides an unparalleled probe to unravel the structure-property correlations in real materials. In this presentation, I will discuss our efforts to design new functional materials based on the perovskite framework with engineered defects and imperfections for various energy applications. Examples will include design of: lead-halide perovskites with defects engineered to achieve stable optoelectronic properties; new lead-free perovskite semiconductors for use in solar cells, and defective oxides for cleaner combustion of hydrocarbons. Rohan Mishra is an Assistant Professor of Mechanical Engineering and Materials Science at the Washington University of St. Louis, since Fall 2015 where he leads the Materials Modeling and Microscopy group (mcube.wustl.edu). He is also an affiliate faculty at the Institute of Materials Science and Engineering at Washington University. Prior to that ( ), he was a postdoctoral researcher in the Scanning Transmission Electron Microscopy group at Oak Ridge National Laboratory with a jointaffiliation from the Department of Physics at Vanderbilt University. He has a Bachelor in Technology in Metallurgical and Materials Engineering from National Institute of Technology Karnataka in India (2008) and a PhD. in Materials Science and Engineering from The Ohio State University (2012). His research interests are in the rational design of materials for various energyrelated applications by using a synergistic combination of electronic structure calculations and scanning transmission electron microscopy experiments.

5 Correlating Structure and Function for Nanoparticle Catalysts Graeme Henkelman Department of Chemistry and Biochemistry, University of Texas at Austin Metal nanoparticles of only atoms are synthesized using a dendrimer encapsulation technique to facilitate a direct comparison with density functional theory (DFT) calculations in terms of both structure and catalytic function. Structural characterization is done using electron microscopy, x-ray scattering, and electrochemical methods. Combining these tools with DFT calculations is found to improve the quality of the structural models. DFT is also successfully used to predict trends between structure and composition of the nanoparticles and their catalytic function for reactions including the reduction of oxygen and selective hydrogenation. This investigation demonstrates some remarkable properties of the nanoparticles, including facile structural rearrangements and nanoscale tuning parameters which can be used to optimize catalytic rates. In this presentation I will focus on a pair of random alloy bimetallic nanoparticles which have complete different trends in hydrogenation activity as a function of composition. Pd/Au is found to be tunable as a function of composition whereas Pt/Au is not. The reason behind these different behaviors will be discussed. Graeme Henkelman is an associate professor in the Department of Chemistry and Biochemistry and is affiliated with the ICES Center for Computational Molecular Sciences. He earned his Ph.D. in theoretical chemistry from the University of Washington. Research in the Henkelman group focuses on understanding atomic scale dynamics at surfaces and in materials. One of the important challenges in theoretical chemistry is bridging the gap between the fast time scale on which atoms move and the human time scale on which interesting dynamics take place. The group works to develop computational methods to extend the time scale of dynamics simulations. These computational methods are being used to better understand and help design new materials for energy conversion and storage. In many cases, slow kinetics in existing materials limit the potential of alternative energy sources. For example, we need to replace platinum with a better and less expensive catalyst in fuel cells to efficiently convert chemical to electrical energy. Another example is the need for battery materials with a higher energy and power density for vehicle applications. The Henkelman group collaborates with chemists, material scientists, and engineers to model existing materials, understand limitations in function at the atomic scale, and then use computational tools to search for alternatives. He is the recipient of an ICES Moncrief Grand Challenge Award.

6 Interface between Theory and Experiment in Electrochemical Energy Conversion and Storage Vijay Ramani Energy, Environmental & Chemical Engineering, Washington University in St. Louis Professor Ramani joined the Department of Energy, Environmental & Chemical Engineering at Washington University in 2016 as the Roma B. and Raymond H. Wittcoff Distinguished University Professor. He concurrently serves as the Director of the Center for Solar Energy and Energy Storage at WashU, and as Faculty Fellow for Entrepreneurship for the Danforth Campus. He is the recipient of the 3M Non-tenured Faculty Award (2010) and the Supramaniam Srinivasan Young Investigator Award from the Energy Technology Division of the Electrochemical Society (2012). He is the past Chair of the Industrial Electrochemistry and Electrochemical Engineering Division of ECS, and of Area 1E (Electrochemical Fundamentals) of AIChE. He has held an Extraordinary Professorship at North West University, South Africa, a visiting Professorship at Tsinghua University, and an Adjunct Professorship in Chemical Engineering at IIT-Madras. Vijay Ramani's research interests lie at the confluence of electrochemical engineering, materials science and renewable and sustainable energy technologies. The National Science Foundation, Office of Naval Research, ARPA- E, and Department of Energy have funded his research, with mechanisms including an NSF CAREER award (2009) and an ONR Young Investigator Award (ONR-YIP; 2010).