Nuclear probes of conductivity in Na-ion battery materials

Non-technical Description

This project explores conductivity in low-cost sodium-based materials for use in rechargeable batteries. Understanding how ions move in a battery is crucial for improving battery performance, including energy density, operating potential, and charge/discharge rates, but our understanding of the relationship between electrical conductivity, ionic conductivity, and diffusion in sodium-ion cathode materials is incomplete.

This project, supported by the Ceramics Program in the Division of Materials Research at NSF, will investigate conductivity with experimental probes of the nuclei of atoms in combination with traditional tools to study battery materials. Mossbauer spectroscopy will be used to investigate the interactions between atomic nuclei and its surrounding electrons.

Quasielastic neutron scattering will be used to study the dynamics of atoms, providing information about the displacements of atoms on the length scale of Angstroms to nanometers, and time scale of picoseconds to tens of nanoseconds. Together, these techniques will provide new insights that enhance our understanding of conductivity in sodium-ion batteries and promote the development of safer, higher capacity, and more sustainable battery technologies.

Sodium-ion batteries are being investigated because of their potential to reduce reliance on lithium and other scarce, high-cost metals. This research addresses the global need for better energy storage solutions, and provides research training opportunities and career mentorship for undergraduate students. It also supports the establishment of a regional center for collaboration on operando and in situ Mossbauer spectroscopy studies.

Technical Summary

The primary goal of this research is to study conductivity in sodium-ion battery cathodes using nuclear probes of Mossbauer spectroscopy and quasielastic neutron scattering to address the roles of electrical conductivity, ionic conductivity, and diffusion in cathodes. Mossbauer spectroscopy is a lab-based technique that probes the hyperfine interactions between the nucleus and the surrounding electrons.

Ex situ temperature-dependent Mossbauer will be used to determine activation energies for polaron mobility. In situ measurements of Mossbauer spectra during electrochemical cycling will provide information about phase, oxidation state, and coordination environment during active cycling. Quasielastic neutron scattering (QENS) is a probe of the dynamical relaxation process in a material.

Temperature-dependent QENS measurements will be used to study sodium diffusion, revealing temporal and microscopic spatial information about diffusing ions that cannot be gained with other experimental techniques. These complementary nuclear techniques, alongside other commonly used tools for investigating battery materials, will be used to examine three hypotheses about the location and transport of active ions in battery cathode materials.

The new knowledge about conductivity in cathodes will advance fundamental understanding of battery cathodes and promote the development of new materials. This research project also trains undergraduate students in energy storage research and creates a pathway for their continuation on to advanced degree programs and careers.

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.