Leube, Bernhard, Collins, Chris, Daniels, Luke, Duff, Benjamin, Dang, Yun, Chen, Ruiyong, Gaultois, Michael, Manning, Troy, Blanc, Frederic, Dyer, Matthew, Claridge, John and Rosseinsky, Matthew (2022) Cation Disorder and Large Tetragonal Supercell Ordering in the Li-rich Argyrodite Li7Zn0.5SiS6. [Data Collection]
Description
A tetragonal argyrodite with >7 mobile cations, Li7Zn0.5SiS6, 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 Li7Zn0.5SiS6 was solved ab initio from high-resolution X-ray and neutron powder diffraction data and supported by solid-state NMR. Li7Zn0.5SiS6 adopts a tetragonal I4 ̅ structure at room temperature with ordered Li and Zn positions and undergoes a transition above 411.1(5) K to a higher symmetry disordered F4 ̅3m 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 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 F4 ̅3m structure, and a unique ordering pattern emerges in which only a subset of these T5 sites are occupied at room temperature in I4 ̅ Li7Zn0.5SiS6. The ionic conductivity, examined via AC impedance spectroscopy and VT-NMR, is 1.0(2) × 10–7 S cm–1 at room temperature and is 4.3(4) × 10–4 S cm–1at 503 K. The transition between the ordered I4 ̅ and disordered F4 ̅3m 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 Li7Zn0.5SiS6 yielding a previously unseen distribution of Li sites, expanding our understanding of structure-property relationships in argyrodite materials.
| Keywords: | Argyrodite, Materials Chemistry, Crystallography, Ionic conductivity |
|---|---|
| Divisions: | Faculty of Science and Engineering > School of Physical Sciences > Chemistry |
| Depositing User: | Luke Daniels |
| Date Deposited: | 24 May 2022 08:03 |
| Last Modified: | 24 May 2022 08:03 |
| DOI: | 10.17638/datacat.liverpool.ac.uk/1603 |
| URI: | https://datacat.liverpool.ac.uk/id/eprint/1603 |
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