Synthesis and Characterization of Three New Lithium‐Scandium Hexathiohypodiphosphates: Li4–3xScxP2S6 (x = 0.358), m‐LiScP2S6, and t‐LiScP2S6

We report the first examples of lithium rare earth metal hexathiohypodiphosphates(IV). Three new lithium-scandium hexathiohypodiphosphates(IV) were synthesized and characterized. The compounds crystallize in three different structure types, featuring isolated ethane-like [P2S6](4-) hexathiohypodiphosphate(IV) units. Li2.926Sc0.358P2S6 or Li4-3xScxP2S6 (x = 0.358) crystallizes in the space group P31m (no. 162) with a = b = 6.0966(5) angstrom, c = 6.5866(6) angstrom, V = 212.02(4) angstrom(3), and Z = 1. The compound is isostructural to Li2FeP2S6 as well as the Li ion conductor Li4-2xMgxP2S6 (x = 1/3, 2/3). Monoclinic LiScP2S6 was found to be a layered compound with van der Waals gaps. The layers consist of edge sharing octahedra that are occupied by Li, Sc, and P-2 in an alternating fashion. It is isostructural to LiAlP2S6 and crystallizes in the space group C2/c (no. 15) with a = 6.933(1) angstrom, b = 10.754(2) angstrom, c = 11.694(2) angstrom, beta = 94.41(3)degrees, V = 869.3(3) angstrom(3), and Z = 4. Trigonal LiScP2S6 crystallizes in the space group P31c (no. 163) with a = b = 6.363(1) angstrom, c = 12.386(3) angstrom, V = 434.3(2) angstrom(3), and Z = 2, and is isostructural to AgInP2S6 and AgScP2S6. Its structure is closely related to the monoclinic version, except that trigonal LiScP2S6 features disordered [P2/2P6/6S6](4-) units. The new phases were investigated by Raman spectroscopy, thermal analysis, and DFT calculations. We further demonstrate that Li4-3xScxP2S6 shows significantly enhanced Li ion conductivity compared to the parent compound Li4P2S6.