Lithium Chalcogenidotetrelates: LiChTSynthesis and Characterization of New Li⁺ Ion Conducting Li/Sn/Se Compounds

Five new lithium chalcogenidotetrelates, so-called “LiChT” phases, with the elemental combination Li/Sn/Se, Li4[SnSe4] (1), 1∞{Li2[SnSe3]} (2), and the respective solvates Li4[SnSe4]·13H2O (3), Li4[Sn2Se6]·14H2O (4), and Li4[SnSe4]·16MeOH (5) were generated in single-crystalline form. We present and discuss syntheses, crystal structures, spectroscopic and thermal behavior, as well as Li+ ion conducting properties of the phases that represent uncommon Li+ ion conducting materials with a maximum conductivity found for 1 (σ20°C = 2 × 10–5 S·cm–1, σ100°C = 9 × 10–4 S·cm–1). The latter was elucidated via impedance spectroscopy and further studied by electronic structure calculations, revealing vacancy migration as the dominant Li+ transport mechanism. Thus, studies on a selenido-LISICON family were found to be a very interesting starting point for an extension of the LISICON-related solid state lithium ion conductors (SSLIC).