Cation disorder and large tetragonal supercell ordering in the Li-rich argyrodite Li7Zn0.5SiS6

DOI: 10.1021/acs.chemmater.2c00320

Authors: Bernhard T. Leube (University of Liverpool) , Christopher M. Collins (University of Liverpool) , Luke M. Daniels (University of Liverpool) , Benjamin B. Duff (University of Liverpool) , Yun Dang (University of Liverpool) , Ruiyong Chen (University of Liverpool) , Michael W. Gaultois (University of Liverpool; Leverhulme Research Centre for Functional Materials Design) , Troy D. Manning (University of Liverpool) , Frédéric Blanc (University of Liverpool; Leverhulme Research Centre for Functional Materials Design) , Matthew S. Dyer (University of Liverpool; Leverhulme Research Centre for Functional Materials Design) , John B. Claridge (University of Liverpool; Leverhulme Research Centre for Functional Materials Design) , Matthew J. Rosseinsky (University of Liverpool; Leverhulme Research Centre for Functional Materials Design)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Chemistry Of Materials , VOL 4

State: Published (Approved)
Published: April 2022
Diamond Proposal Number(s): 17193

Abstract: 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 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 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 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 Li7Zn0.5SiS6 yielding a previously unseen distribution of Li sites, expanding our understanding of structure–property relationships in argyrodite materials.

Journal Keywords: Granular materials; Diffraction; Group theory; Materials; Chemical structure

Subject Areas: Materials, Chemistry


Instruments: I11-High Resolution Powder Diffraction

Added On: 20/04/2022 08:39

Documents:
acs.chemmater.2c00320.pdf

Discipline Tags:

Physical Chemistry Energy Materials Chemistry Materials Science Chemical Engineering Engineering & Technology

Technical Tags:

Diffraction X-ray Powder Diffraction