Fast ion conductors, also known as solid electrolytes, are solids with highly mobile ions. They are widely employed in many technological applications, including fuel cells, batteries, and sensors. In this talk, in situ and in operando NMR/MRI for real-time monitoring of chemical and electrochemical reactions that occur during the synthesis and operation of ion conductors, tracer-exchange NMR for probing ion conduction pathways, and strategies for improving ionic conductivities and stabilities of fast ion conductors will be discussed.
New ion conductors with high ionic conductivities have been designed with in silico efforts; in situ monitoring of the synthesis process is necessary to chart the thermodynamic and kinetic pathways to the target structures with desirable properties. In this work, high-temperature in situ solid-state NMR is employed to follow the changes in structures and properties of precursors, intermediates, and final products during the synthesis of fast Li-ion conductors. Ionic conductivity is determined by three factors, i.e., charge carrier concentrations, ion dynamics, and ion transport pathways. A tracer-exchange NMR approach is devised on the basis of 6Li.7Li isotope replacement for determining Li transport pathways in ion conductors. This method has been demonstrated on a few ceramic Li-ion conductors and ceramic-polymer composite electrolytes. In operando NMR and MRI characterizations of solid electrolytes are performed to probe Li transport, Li distribution homogeneity, and Li microstructure formation during the charge-discharge operation of solid-state rechargeable batteries.
This effort aims to provide new approaches for advancing the synthesis science of high-performance ion conductors, to improve our fundamental understanding of ion conduction mechanisms, and to gain insights into structural features of solid electrolytes for fast ion conduction and long-term stability.
Yan-Yan Hu, Assistant Professor of Chemistry & Biochemistry at Florida State University, earned her B.S. in Chemistry from Tsinghua University (Beijing, China) in 2006 and her Ph. D. in Analytical Chemistry from Iowa State University (Ames, Iowa) in 2011. She worked as a Royal Society Newton Fellow, Marie Curie Research Fellow, and Clare Hall Research Fellow at the University of Cambridge from 2011 to 2014. She joined the faculty in the Department of Chemistry and Biochemistry at Florida State University as an Assistant Professor in the fall of 2014. Dr. Hu holds a joint appointment at the National High Field Magnetic Laboratory. Her research is focused on the development and applications of advanced in situ solid-state NMR for fundamental studies of energy materials, in particular, those for all-solid-state rechargeable batteries. She is a 2017 recipient of the Marion Milligan Mason Award from the American Association for the Advancement of Science, Emerging Young Investigator Award from the Florida Section of the ACS. She is selected as a Scialog Fellow for Energy Storage from the Research Corporation.