Sn Substitution in the Lithium Superionic Argyrodite Li6PCh5I (Ch = S and Se)

Ajay Gautam; Michael Ghidiu; Anna-Lena Hansen; Saneyuki Ohno; Wolfgang G Zeier

doi:10.1021/acs.inorgchem.1c02813

Sn Substitution in the Lithium Superionic Argyrodite Li₆PCh₅I (Ch = S and Se)

Inorg Chem. 2021 Dec 20;60(24):18975-18980. doi: 10.1021/acs.inorgchem.1c02813. Epub 2021 Dec 1.

Authors

Ajay Gautam¹, Michael Ghidiu¹, Anna-Lena Hansen², Saneyuki Ohno³, Wolfgang G Zeier^{4

5}

Affiliations

¹ Institute of Physical Chemistry, Justus-Liebig-University Giessen, Heinrich-Buff-Ring 17, D-35392 Giessen, Germany.
² Institute for Applied Materials - Energy Storage Systems, Karlsruhe Institute of Technology, Hermann-von-Helmholtz-Platz 1, D-76344 Eggenstein-Leopoldshafen, Germany.
³ Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, 744 Motooka, Nishi-ku, 819-0395 Fukuoka, Japan.
⁴ Institute of Inorganic and Analytical Chemistry, University of Münster, Corrensstrasse 30, 48149 Münster, Germany.
⁵ Institut für Energie- und Klimaforschung (IEK), IEK-12: Helmholtz-Institut Münster, Forschungszentrum Jülich, 48149 Münster, Germany.

PMID: 34851091
DOI: 10.1021/acs.inorgchem.1c02813

Abstract

The lithium argyrodites Li₆PS₅X (X = Cl, Br, and I) have attracted interest as fast solid ionic conductors for solid-state batteries. Within this class of materials, it has been previously suggested that more polarizable anions and larger substituents should influence the ionic conductivity (e.g., substituting S by Se). Building upon this work, we explore the influence of Sn substitution in lithium argyrodites Li_6+xSn_xP_1-xSe₅I in direct comparison to the previously reported Li_6+xSn_xP_1-xS₅I series. The (P⁵⁺/Sn⁴⁺)Se₄^3/4- polyhedral volume, unit cell volume, and lithium coordination tetrahedra Li(48h)-(S/Se)₃-I increase with Sn substitution in this new selenide series. Impedance spectroscopy reveals that increasing Sn⁴⁺ substitution results in a fivefold improvement in the ionic conductivity when compared to Li₆PSe₅I. This work provides further understanding of compositional influences for optimizing the ionic conductivity of solid electrolytes.