Non-Technical Abstract Fast ion conductors are an essential component of electrochemical devices such as fuel cells, solid-state batteries, gas separation membranes, and chemical sensors. An important criterion for ionic conductors to be suitable for such high-performance devices is high ionic conductivity at operating temperatures. In recent years, there has been a growing interest in developing sustainable, cost-effective, and high-conductivity oxide-ion conductors for intermediate-temperature solid-oxide fuel cells, one of the most efficient and cleanest energy conversion and storage technologies. One strategy is to design rare-earth-free fast-ion conductors. With support from the Solid State and Materials Chemistry Program in the Division of Materials Research at NSF, this project focuses on investigating the fundamental mechanisms of ionic conduction and revealing the relationship of chemical structure and conductivity in newly developed fast-ion conductors. The findings from this study provide valuable guidelines for rationally designing fast oxide-ion conductors. The research also develops unique characterization tools and protocols which are to be incorporated into the National High Magnetic Field Laboratory and made available to national and international users. Students assigned to this project, including undergraduates and a female minority graduate student, are provided with unique research training opportunities and guidance to advance their academic careers. The principal investigator's team disseminates the key findings and technological developments to the general public by creating educational videos and performing demonstrations at science events.
A new group of cost-effective and rare-earth-free fast ion conductors has been recently discovered. Some have unparalleled ion conductivity for intermediate-temperature solid-oxide fuel cells. The mechanism for such high ion conductivity is nevertheless unknown. This research uses Na-doped strontium silicates as model systems to understand how ions migrate in this class of fast-ion conductors. The study involves three major tasks including synthesis of strontium silicates with controlled alkaline element doping, advanced characterization with high-temperature high-resolution solid-state O-17, Na-23, and Si-29 NMR probing of structural defects and ion dynamics, and electrochemical measurements and computational efforts complementary to NMR characterizations to establish the important linkage between ion conductivity and structural defects.
