CAS-Climate: Identifying and Characterizing the Structures and Physical Properties of Sodiated Intermetallics

Colorado State University, Fort Collins CO

Investigators

Abstract

Non-technical Abstract Lithium-ion rechargeable batteries have been integrated into our everyday lives in mobile electronics, and are being incorporated in a significant way in various modes of transportation. There is increasing demand to extend new energy storage technologies toward emerging applications such as batteries for the energy produced by devices like solar cells or windmills. However, there is no one perfect battery for every application! With the support of the Solid State and Materials Chemistry Program in the Division of Materials Research, Dr. Amy Prieto of Colorado State University and her students are focused on developing better materials for sodium ion batteries, because sodium is much more naturally abundant than lithium. Another key aspect of this project is the training that students receive in electrochemistry and energy storage research. This addresses the desperate need in the United States for a workforce trained in this field. Technical Abstract A common approach to Na-ion battery research is to simply screen the top candidates from Li-ion battery technologies for use in Na-ion systems. Often, this strategy is fundamentally flawed as Li and Na exhibit surprisingly different chemistries. The chemistries developed for cathodes and anodes for Na-ion batteries are not nearly as well developed or understood as those of Li, and some of the best anode materials for storing Li do not store Na. As a result, alloying anode materials, including antimony-based (Sb-based) alloys, have been of great interest due to their relatively high gravimetric and volumetric capacities and their ability to operate at potentials similar to Na/Na+, resulting in high overall energy densities. However, the structures produced during Na insertion into Sb do not appear to follow the thermodynamically predicted intermediates based on phase diagrams, and instead often proceed via amorphous intermediates. With the support of the Solid State and Materials Chemistry Program in the Division of Materials Research, Dr. Amy Prieto of Colorado State University and her students study these insertion processes and the NaxSby compounds formed by electrochemically sodiating/desodiating metal antimonides (MSb), which present a very rich compositional and structural landscape that is yet to be fundamentally understood. They develop and test a toolbox of characterization techniques to study these phases and apply these findings to other alloy-based electrodes. Underlying their research efforts is the hypothesis that if one can identify and characterize the intermediate solid-state structures that are accessed as these anodes are sodiated and desodiated, a deep understanding of the thermodynamics and kinetics of this system along with new materials for clean energy applications will emerge. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.