Understanding the effect of lattice polarisability on the electrochemical properties of lithium tetrahaloaluminates, LiAlX4 (X = Cl, Br, I)

Flores-González, N., López, M., Minafra, N., Bohnenberger, J., Viñes, F., Rudić, S., Krossing, I., Zeier, W. G., Illas, F. and Gregory, D. H. (2022) Understanding the effect of lattice polarisability on the electrochemical properties of lithium tetrahaloaluminates, LiAlX4 (X = Cl, Br, I). Journal of Materials Chemistry A, 10(25), pp. 13467-13475. (doi: 10.1039/D2TA02821B)

Abstract

Establishing links between the structure and physical properties of solid-state ionic conductors contributes not only to a rationale of their fundamental nature, but also provides design principles to accelerate the discovery of new materials. Lithium ion conduction in complex halides is not well-elucidated and so the interplay between lattice dynamics, electronic structure and electrochemical properties in such halides has been explored in the isostructural family of lithium tetrahaloaluminates LiAlX4 (X = Cl, Br, I). Using a combination of experimental methods (Diffuse reflectance UV-Vis spectroscopy, Pulse-Echo Speed of Sound measurements, Raman spectroscopy, Inelastic Neutron Scattering) and periodic density functional theory (DFT) based calculations, we demonstrate that softer lattices (quantified in terms of Debye frequencies or Li-phonon band centres as a function of X) provide lower activation energies for Li+ migration. However, the relationship between polarisability and Li+ conductivity is not straightforward. In line with expectations emergent from the Meyer-Neldel rule, the activation energy for Li+ hopping, Ea, and the pre-exponential terms collated as σ0 in the Arrenhius equation for activated conductivity, correlate. It is also evident that the electrochemical oxidative potential limit correlates with the X– phonon band centre in the vibrational density of states (VDOS) and that the electrochemical stability window (EW) and optical band gap are interlinked, as expected.

• Item Type: Articles
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Flores-Gonzalez, Dr Nicolas Andres and Gregory, Professor Duncan
• Authors: Flores-González, N., López, M., Minafra, N., Bohnenberger, J., Viñes, F., Rudić, S., Krossing, I., Zeier, W. G., Illas, F., and Gregory, D. H.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: Journal of Materials Chemistry A
• Publisher: Royal Society of Chemistry
• ISSN: 2050-7488
• ISSN (Online): 2050-7496
• Published Online: 01 June 2022
• Copyright Holders: Copyright © 2022 The Royal Society of Chemistry
• First Published: First published in Journal of Materials Chemistry A 10(25): 13467-13475
• Publisher Policy: Reproduced under a Creative Commons License

Project Code	Award No	Project Name	Principal Investigator	Funder's Name	Funder Ref	Lead Dept
190912		High throughput microwave synthesis of Li-ion battery materials	Serena Corr	Engineering and Physical Sciences Research Council (EPSRC)	EP/N001982/1	Chemistry