CAREER: Analytical Cryo-Scanning Transmission Electron Microscopy for Understanding Physical and Chemical Processes at Liquid/Solid Interfaces

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Non-technical summary: Interfaces and surfaces play a special role in synthesizing novel materials, enabling chemical reactions, designing electronic devices, and determining the mechanical stability of structural materials. To realize the goal of understanding processes at interfaces between liquids and solids, processes that for example determine how batteries function and how they fail, the objective of this project is to develop and apply novel electron microscopy techniques that allow not only solid/solid, but also liquid/solid and soft/hard interfaces to be studied at the nanometer to atomic scale. This project will have an impact on science and technology by providing high-resolution characterization techniques of materials that are of interest for a wide range of technologies thereby promoting the progress of sciences, materials discovery and applications. The project will also provide stimulating and authentic experiences for freshmen, K-12 students and teachers with the goal of motivating a new generation of scientists. Microscopy will play a central role in these efforts, which include the development of a freshman laboratory module and a microscopy-based science kit for K-12 teachers nationwide. Technical summary: Recent advances in electron microscopy have opened a new era of atomic resolution imaging and spectroscopy inside solids. Liquid/solid interfaces have yet to be imaged at high spatial resolution but play a critical role in a range of biological, chemical and physical processes from catalysis to electrochemical energy storage to the formation of biominerals. Inspired by electron microscopy of biological systems, with this CAREER award, the PI develops new sample preparation techniques that use rapid freezing to stabilize the soft and liquid components of composite systems in a vitreous state enabling structural and spectroscopic studies by cryo-STEM. Materials that are sufficiently thin for direct analysis in the microscope such as nanostructured electrode materials in liquid electrolytes, the crystal structure and defects of the inorganic crystalline components and the surrounding liquid will be simultaneously imaged. For thicker samples, including lithium-metal batteries, cryo-focused ion beam lift-out will be developed to gain access to the internal liquid/solid interfaces. This characterization platform will be used to study the early stages of dendrite formation at lithium-metal/electrolyte interfaces to gain a fundamental understanding of the mechanisms governing their formation and growth. The ability to identify nucleation sites for dendritic growth will shed new light on a central challenge in developing high-energy rechargeable metal batteries.With the goal of creating a broader, more diverse workforce, this project focuses on attracting and recruiting students into the fields of science, technology, engineering and mathematics at an earlier stage. K-12 teacher development is supported through MicroWorld, a microscopy-based module that will be adapted to meet the challenges of the Next Generation Science Standards. This module will benefit teacher workshops for K-12 teachers who work in minority-serving schools and will also be made available to teachers nationwide through the CCMR Lending Library of Experiments. Freshmen will benefit from the development of FLAME, a new Freshman Lab on Advanced Microscopy with Electrons. This project will therefore impact science, technology, engineering and mathematics education, both at the K-12 and the college level.