Our group uses state-of-the-art x-ray characterization to see inside complex nanomaterials during operation and harness the mesoscale phenomena for advanced functionality. Specifically, we are interested in understanding the fundamental interactions leading to increased electrocatalytic activity and durability of catalysts. We also apply x-ray imaging resonant and non-resonant diffraction to study ion intercalation and ion transport in materials for energy storage. Finally, we induce novel states in quantum materials and interrogate their properties with x-rays at free-electron lasers.
1. Defect dynamics and phase transformations in energy storage materials: Electrochemical energy storage devices, the dominant power source for mobile electronics, are increasingly used in hybrid and fully electric vehicles and are promising candidates for the grid storage. Electrodes with increased capacity, faster charge rates, and minimal capacity fade are required. Our group uses various state-of-the-art x-ray scattering and imaging techniques to study the dynamical processes in nanoparticulate lithium-ion and sodium-ion based positive electrode materials. The in-situ understanding of the ion-motion-induced physical phenomena at the single particle level is key to for advanced functionality.
2. New phases of matter far from equilibrium: The emergence of order through symmetry breaking is a fascinating phenomenon. It leads to a plethora of intriguing ground states found in antiferromagnets, Mott insulators, superconductors, and density wave systems. Exploiting states of matter far from equilibrium provides even more surprising routes to symmetry-lowered, ordered states. Photoexcitation is unique in accessing non-equilibrium dynamics, and our group uses pump-probe techniques at the recently developed x-ray free-electron lasers to study ultrafast processes in strongly correlated electrons systems. We seek to explore new non-equilibrium phases of matter, which have the potential for technological applications.
3. Self-assembly of biological photonic crystals: Light interference, as was realized as early as the beginning of the 19th century by Lord Rayleigh, is a common cause of the bright coloring of various animals such as the spine of the sea mouse, butterfly wings, feathers of birds of paradise, or the skin of chameleons. These photonic crystals are not only interesting for evolutionary biology but also appealing for metamaterial research and exciting applications such as designing Weyl points. Our group uses coherent x-ray imaging and ptychography to study the self-assembly processes underpinning the formation of biological photonic crystals in various species.
J. J. Huang, D. Weinstock, H. Hirsh, R. Bouck, M. Zhang, O. Yu. Gorobtsov, M. Okamura, R. Harder, W. Cha, J. P. C. Ruff, Y. S. Meng, and A. Singer, “Disorder Dynamics in Battery Nanoparticles During Phase Transitions Revealed by Operando Single-Particle Diffraction”
Advanced Energy Materials, 12, 2103521 (2022).
D. Weinstock, H. S. Hirsh, O. Yu Gorobtsov, M. Zhang, J. Huang, R. Bouck, J. P. C. Ruff, Y. S. Meng, A. Singer, “Structure-selective operando x-ray spectroscopy”
ACS Energy Letters 7, 261-266 (2021).
Yifei Sun, Oleg Yu Gorobstov, Linqin Mu, Daniel Weinstock, Ryan Bouck, Wonsuk Cha, Nikolaos Bouklas, Feng Lin, and Andrej Singer, “X-ray nanoimaging of crystal defects in single grains of solid-state electrolyte AlxLi7-3xLa3Zr2O12”
Nano letters 21, 4570–4576 (2021).
O. Gorobtsov, L. Ponet, S. K. K. Patel, N. Hua, A. G. Shabalin, S. Hrkac, J. Wingert, D. Cela, J. M. Glownia, D. Zhu, R. Medapalli, M. Chollet, S. Artyukhin, E. E. Fullerton, O. G. Shpyrko, and A. Singer, “Ultrafast control of a vibrational state near the spin density wave critical point”
Nature Communications, 12, 2865 (2021).