Substitutional disorder: Structure and ion dynamics of the argyrodites Li 6 PS 5 Cl, Li 6 PS 5 Br and Li 6 PS 5 I

I. Hanghofer*, M. Brinek, S. L. Eisbacher, B. Bitschnau, M. Volck, V. Hennige, I. Hanzu, D. Rettenwander, H. M.R. Wilkening

*Corresponding author for this work

Research output: Contribution to journalArticle

Abstract

For the development of safe and long-lasting lithium-ion batteries we need electrolytes with excellent ionic transport properties. Argyrodite-type Li 6 PS 5 X (X: Cl, Br, I) belongs to a family of such a class of materials offering ionic conductivities, at least if Li 6 PS 5 Br and Li 6 PS 5 Cl are considered, in the mS cm -1 range at room temperature. Although already tested as ceramic electrolytes in battery cells, a comprehensive picture about the ion dynamics is still missing. While Li 6 PS 5 Br and Li 6 PS 5 Cl show an exceptionally high Li ion conductivity, that of Li 6 PS 5 I with its polarizable I anions is by some orders of magnitude lower. This astonishing effect has not been satisfactorily understood so far. Studying the ion dynamics over a broad time and length scale is expected to help shed light on this aspect. Here, we used broadband impedance spectroscopy and 7 Li NMR relaxation measurements and show that very fast local Li ion exchange processes are taking place in all three compounds. Most importantly, the diffusion-induced NMR spin-lattice relaxation in Li 6 PS 5 I is almost identical to that of its relatives. Considering the substitutional disorder effects in Li 6 PS 5 X (X = Br, Cl), we conclude that in structurally ordered Li 6 PS 5 I the important inter-cage jump processes are switched off, hindering the ions from taking part in long-range ion transport.

Original languageEnglish
Pages (from-to)8489-8507
Number of pages19
JournalPhysical Chemistry Chemical Physics
Volume21
Issue number16
DOIs
Publication statusPublished - 1 Jan 2019

ASJC Scopus subject areas

  • Physics and Astronomy(all)
  • Physical and Theoretical Chemistry

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