Sn Substitution in the Lithium Superionic Argyrodite Li<sub>6</sub>PCh<sub>5</sub>I (Ch = S and Se)
Ajay Gautam, Michael Ghidiu, Anna‐Lena Hansen, Saneyuki Ohno, Wolfgang G. Zeier
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 Li6+xSnxP1–xSe5I in direct comparison to the previously reported Li6+xSnxP1–xS5I series. The (P5+/Sn4+)Se43/4– 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.