LiBi₃S₅—A lithium bismuth sulfide with strong cation disorder

Abstract

Among chalcogenide semiconductors for thermoelectric applications, alkali-metal bismuth compounds occur in many complex compositions favorable for high performance. Although LiBi₃S₅ had been announced in 1977, the potential 1D lithium-ion conductor has hitherto eluded selective synthesis and structure determination. In this study, we present a solid-state route to phase-pure LiBi₃S₅ powder starting from LiBiS₂ and Bi₂S₃. Neutron diffractograms and lithium NMR spectra reveal its crystal structure to be a cation-disordered variety of the AgBi₃S₅ type (synthetic pavonite; monoclinic, C2/m). Topological analyses and lithium NMR relaxometry suggest that correlated lithium-ion diffusion with activation energies up to 0.66(2) eV occurs along the channels in b direction including tetrahedral voids. Because of cation disorder, immobile bismuth(III) ions clog these pathways, making LiBi₃S₅ a moderate to poor ionic conductor. The synthesis route reported is nonetheless promising for new lithium bismuth sulfides with, possibly ordered, structure types of the pavonite homologous series.

Dr. Dennis Wiedemann

Technischer Berater für Umweltfragen
Chemiker · Kristallograph

Ich bin promovierter Chemiker und berate zu immissionsschutz- und wasserrechtlichen Genehmigungsfragen.