Cation Disorder and Large Tetragonal Supercell Ordering in the Li-Rich Argyrodite Li₇Zn_0.5SiS₆

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Leube, Bernhard T, Collins, Christopher M ORCID: 0000-0002-0101-4426, Daniels, Luke M ORCID: 0000-0002-7077-6125, Duff, Benjamin B, Dang, Yun, Chen, Ruiyong ORCID: 0000-0002-5340-248X, Gaultois, Michael W ORCID: 0000-0003-2172-2507, Manning, Troy D ORCID: 0000-0002-7624-4306, Blanc, Frederic ORCID: 0000-0001-9171-1454, Dyer, Matthew S ORCID: 0000-0002-4923-3003 et al (show 2 more authors) , Claridge, John B ORCID: 0000-0003-4849-6714 and Rosseinsky, Matthew J ORCID: 0000-0002-1910-2483 (2022) Cation Disorder and Large Tetragonal Supercell Ordering in the Li-Rich Argyrodite Li₇Zn_0.5SiS₆ CHEMISTRY OF MATERIALS, 34 (9). pp. 4073-4087. ISSN 0897-4756, 1520-5002

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Abstract

A tetragonal argyrodite with >7 mobile cations, Li<inf>7</inf>Zn<inf>0.5</inf>SiS<inf>6</inf>, is experimentally realized for the first time through solid state synthesis and exploration of the Li−Zn−Si−S phase diagram. The crystal structure of Li<inf>7</inf>Zn<inf>0.5</inf>SiS<inf>6</inf> was solved ab initio from high-resolution X-ray and neutron powder diffraction data and supported by solid-state NMR. Li<inf>7</inf>Zn<inf>0.5</inf>SiS<inf>6</inf> adopts a tetragonal I4 structure at room temperature with ordered Li and Zn positions and undergoes a transition above 411.1 K to a higher symmetry disordered F43m structure more typical of Li-containing argyrodites. Simultaneous occupation of four types of Li site (T5, T5a, T2, T4) at high temperature and five types of Li site (T5, T2, T4, T1, and a new trigonal planar T2a position) at room temperature is observed. This combination of sites forms interconnected Li pathways driven by the incorporation of Zn²⁺ into the Li sublattice and enables a range of possible jump processes. Zn²⁺ occupies the 48h T5 site in the high-temperature F43m structure, and a unique ordering pattern emerges in which only a subset of these T5 sites are occupied at room temperature in I4 Li<inf>7</inf>Zn<inf>0.5</inf>SiS<inf>6</inf>. The ionic conductivity, examined via AC impedance spectroscopy and VT-NMR, is 1.0(2) × 10⁻⁷ S cm⁻¹ at room temperature and 4.3(4) × 10⁻⁴ S cm⁻¹ at 503 K. The transition between the ordered I4 and disordered F43m structures is associated with a dramatic decrease in activation energy to 0.34(1) eV above 411 K. The incorporation of a small amount of Zn²⁺ exercises dramatic control of Li order in Li<inf>7</inf>Zn<inf>0.5</inf>SiS<inf>6</inf> yielding a previously unseen distribution of Li sites, expanding our understanding of structure−property relationships in argyrodite materials.

Item Type:	Article
Additional Information:	No access restrictions, data can be made immediately available.
Uncontrolled Keywords:	3402 Inorganic Chemistry, 34 Chemical Sciences
Divisions:	Faculty of Science & Engineering > School of Physical Sciences
Depositing User:	Symplectic Admin
Date Deposited:	19 May 2022 13:59
Last Modified:	16 Jun 2026 10:22
DOI:	10.1021/acs.chemmater.2c00320
Open Access URL:	https://pubs.acs.org/doi/10.1021/acs.chemmater.2c0...
Related Websites:	Author Publisher
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3155160
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