Understanding the Key to Unlocking Fast Li-ion Conduction in Fluoride-based Solid Electrolytes

NON-TECHNICAL SUMMARY

All-solid-state batteries have the potential to increase the energy density of liquid-based cells by 30%. Unfortunately, they currently suffer from chemical degradation at the interfaces and deposition of Li between particles of the oxides frequently used as the electrolyte, which ultimately hinders their long-term reversibility. The goal of this work, supported by the Ceramics Program within the Division of Materials Research, is to develop fluoride-based materials that are more robust against these detrimental side reactions. While fluorides have been explored as solid electrolytes in the past, very few phases with fast ionic conductivity at room temperature have been discovered. This work postulates that the formation energy of defects plays a critical role for enabling fast diffusion and seeks to elucidate ways to control their evolution during synthesis.

TECHNICAL SUMMARY

This project will study new fluoride-based garnets and Zr-based compounds to better understand how the structural rigidity of fluorides affects ionic conductivity. Electrochemical impedance spectroscopy and Density Functional Theory (DFT) calculations will be used to gain a deeper understanding of charge transport through the weakly polarizable anionic sublattice of fluorides. Aliovalent chemical substitutions will be performed to examine the impact of increasing the lithium content or creating vacancies in the lattice has on the conductivity. Fundamentally, the proposed research seeks to develop a deeper understanding of how to promote fast ion transport in fluoride-based solid electrolytes through an integrated approach involving synthesis, advanced characterization, and theoretical modeling.

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.

Award Number: 2602721
Principal Investigator: Brent Melot
Funds Obligated: $91,969
State: NY