Evidence for a Solid-Electrolyte Inductive Effect in the Superionic Conductor Li(10)Ge(1–x)Sn(x)P(2)S(12)

[Image: see text] Strategies to enhance ionic conductivities in solid electrolytes typically focus on the effects of modifying their crystal structures or of tuning mobile-ion stoichiometries. A less-explored approach is to modulate the chemical bonding interactions within a material to promote fast lithium-ion diffusion. Recently, the idea of a solid-electrolyte inductive effect has been proposed, whereby changes in bonding within the solid-electrolyte host framework modify the potential energy landscape for the mobile ions, resulting in an enhanced ionic conductivity. Direct evidence for a solid-electrolyte inductive effect, however, is lacking—in part because of the challenge of quantifying changes in local bonding interactions within a solid-electrolyte host framework. Here, we consider the evidence for a solid-electrolyte inductive effect in the archetypal superionic lithium-ion conductor Li(10)Ge(1–x)Sn(x)P(2)S(12). Substituting Ge for Sn weakens the {Ge,Sn}–S bonding interactions and increases the charge density associated with the S(2–) ions. This charge redistribution modifies the Li(+) substructure causing Li(+) ions to bind more strongly to the host framework S(2–) anions, which in turn modulates the Li(+) ion potential energy surface, increasing local barriers for Li(+) ion diffusion. Each of these effects is consistent with the predictions of the solid-electrolyte inductive effect model. Density functional theory calculations predict that this inductive effect occurs even in the absence of changes to the host framework geometry due to Ge → Sn substitution. These results provide direct evidence in support of a measurable solid–electrolyte inductive effect and demonstrate its application as a practical strategy for tuning ionic conductivities in superionic lithium-ion conductors.