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, Li-4[SnSe4] (1), (1)(infinity){Li-2[SnSe3]} (2), and the respective solvates Li-4[SnSe4]center dot 13H(2)O (3), Li-4[Sn2SeO center dot 14H(2)O (4), and Li-4[SnSe4]center dot 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 (sigma(20 degrees C) = 2 X 10(-5) S.cm(-1), sigma(100 degrees C) = 9 X 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).