Mechanochemical synthesis and structure of lithium tetrahaloaluminates, LiAlX₄ (X = Cl, Br, I); a family of Li-ion conducting ternary halides

Flores-Gonzalez, N., Minafra, N., Dewald, G., Reardon, H., Smith, R. I., Adams, S., Gregory, D. H. and Zeier, W. G. (2021) Mechanochemical synthesis and structure of lithium tetrahaloaluminates, LiAlX₄ (X = Cl, Br, I); a family of Li-ion conducting ternary halides. ACS Materials Letters, 3(5), pp. 652-657. (doi: 10.1021/acsmaterialslett.1c00055) (PMID:34476400) (PMCID:PMC8397468)

Abstract

State-of-the-art oxides and sulfides with high Li-ion conductivity and good electrochemical stability are among the most promising candidates for solid-state electrolytes in secondary batteries. Yet emerging halides offer promising alternatives because of their intrinsic low Li+ migration energy barriers, high electrochemical oxidative stability, and beneficial mechanical properties. Mechanochemical synthesis has enabled the characterization of LiAlX4 compounds to be extended and the iodide, LiAlI4, to be synthesized for the first time (monoclinic P21/c, Z = 4; a = 8.0846(1) Å; b = 7.4369(1) Å; c = 14.8890(2) Å; β = 93.0457(8)°). Of the tetrahaloaluminates, LiAlBr4 exhibited the highest ionic conductivity at room temperature (0.033 mS cm–1), while LiAlCl4 showed a conductivity of 0.17 mS cm–1 at 333 K, coupled with the highest thermal and oxidative stability. Modeling of the diffusion pathways suggests that the Li-ion transport mechanism in each tetrahaloaluminate is closely related and mediated by both halide polarizability and concerted complex anion motions.

• Item Type: Articles
• Additional Information: The authors acknowledge the Advanced Human Capital Pro-gram of the National Commission for Scientific and Technolog-ical Research (CONICYT/Becas Chile/No 72170338) for a PhD scholarship for N.F.G., the Royal Society of Chemistry for Re-searcher Mobility Grant M19-8459 and the EPSRC for associ-ated funding under grant EP/N001982/1. The authors also thank the UK Science and Technology Facilities Council (STFC) and the Material Science Beamline X04SA at the Paul Scherrer Institute (PSI) for the award of ISIS Xpress access and MESQUIK access measurements, respectively and Dr Nicola Casati at PSI for collecting the latter data. N.M. and W.Z. are grateful for sup-port by the Deutsche Forschungsgemeinschaft (DFG) under grant number ZE 1010/4-1.
• Status: Published
• Refereed: Yes
• Glasgow Author(s) Enlighten ID: Flores-Gonzalez, Dr Nicolas Andres and Gregory, Professor Duncan
• Authors: Flores-Gonzalez, N., Minafra, N., Dewald, G., Reardon, H., Smith, R. I., Adams, S., Gregory, D. H., and Zeier, W. G.
• College/School: College of Science and Engineering > School of Chemistry
• Journal Name: ACS Materials Letters
• Publisher: American Chemical Society
• ISSN: 2639-4979
• ISSN (Online): 2639-4979
• Published Online: 20 April 2021
• Copyright Holders: Copyright © 2021 The Authors
• First Published: First published in ACS Materials Letters 3(5):652-657
• Publisher Policy: Reproduced under a Creative Commons Licence

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