Synthesis and Characterization of Three New Lithium‐Scandium Hexathiohypodiphosphates: Li_4–3xSc_xP₂S₆ (x = 0.358), m‐LiScP₂S₆, and t‐LiScP₂S₆

Abstract

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) Å, c = 6.5866(6) Å, V = 212.02(4) Å3, 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 P2 in an alternating fashion. It is isostructural to LiAlP2S6 and crystallizes in the space group C2/c (no. 15) with a = 6.933(1) Å, b = 10.754(2) Å, c = 11.694(2) Å, β = 94.41(3)°, V = 869.3(3) Å3, and Z = 4. Trigonal LiScP2S6 crystallizes in the space group P31c (no. 163) with a = b = 6.363(1) Å, c = 12.386(3) Å, V = 434.3(2) Å3, 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.

Size-Driven Stability of Lanthanide Thiophosphates Grown from an Iodide Flux

“…The pervasive interest in main group, transition, and rare earth metal sulfide chemistry is driven by their structural diversity and unique properties. − Replacing hard Lewis base oxide ligands with soft sulfides leads to a change in the bonding between the metal center and the ligand resulting in changes in the optical, magnetic, and structural properties of the materials. − Recently, particular interest has been directed toward thiophosphate materials that exhibit conducting and catalytic properties. , For example, a family of layered thiophosphate materials with a general formula MPS x , such as MnPS 3 , NiPS 3 , and ZnPS 3 , can be readily exfoliated and exhibits antiferromagnetic transitions at temperatures below 120 K. − Layered thiophosphites have shown potential for application in hydrogen evolution reactions and other energy applications. , Lithium and sodium thiophosphates, in particular, possess outstanding diffusion properties making them a potential class of materials for ion conduction applications and, as a result, have generated significant interest to comprehensively investigate these materials. ,− …”

“…8,9 For example, a family of layered thiophosphate materials with a general formula MPS x , such as MnPS 3 , NiPS 3 , and ZnPS 3 , can be readily exfoliated and exhibits antiferromagnetic transitions at temperatures below 120 K. 10−13 Layered thiophosphites have shown potential for application in hydrogen evolution reactions and other energy applications. 14,15 Lithium and sodium thiophosphates, in particular, possess outstanding diffusion properties making them a potential class of materials for ion conduction applications and, as a result, have generated significant interest to comprehensively investigate these materials. 8,16−22 Oxyphosphate ligands have been studied extensively and are known to exhibit various oxidation states, rich structural diversity, and different structural units ranging from isolated P(V)O 4 3− groups to infinite (P(V)O 3 − ) ∞ chains.…”

Li2MP2S6: Building-Block Approach to a Family of 2D Non-van der Waals-Layered Materials and Their Water, Ammonia, and Ion Intercalation Properties

“…Compounds Li 4–3 x V x P 2 S 6 ( x = 0.5) ( 1 ), Li 4–2 x Co x P 2 S 6 ( x = 0.75) ( 4 ), and Li 4–2 x Ni x P 2 S 6 ( x = 0.8) ( 5 ) crystallize in the P 3̅1 m space group isostructural to Li 4–3 x Sc x P 2 S 6 or Li 4–2 x M x P 2 S 6 (M = Mg, Fe, and Co). ,, The asymmetric unit of the crystal structures of 1 , 4, and 5 consists of one transition metal (V, Co, or Ni) mixed-occupied with Li (Li1), one disordered phosphorus split between P1 (major component) and P1A (minor component) for 1 (no disorder in P for 4 and 5 ), one sulfur, and one lithium site (Figure a,b). In both cases, 2D layers are formed in the ab -plane by edge sharing between MS 6 octahedra themselves or between MS 6 octahedra and P 2 S 6 polyhedra and stacked along the c -axis with Li ions filling the interlayer van der Waals gap (Figure c).…”

“…Takada et al first reported the synthesis of Li 4–2 x M x P 2 S 6 (M = Mg and Fe) under anhydrous conditions in a sealed quartz tube and determined its crystal structure in the trigonal system ( P 3̅1 m ). , Accordingly, Li 2 MgP 2 S 6 displayed couple of orders higher Li-ion conductivity compared to pure Li 4 P 2 S 6 , whose room-temperature conductivity is found to be 1.6 × 10 –7 S/cm, while on the other hand, Li 2 FeP 2 S 6 is a 3 V cathode . Lotsch's group showed that partial substitution of M 3+ in Li 4 P 2 S 6 can also stabilize the trigonal Li 4–2 x Mg x P 2 S 6 structure type as in the case of Li 4–3 x Sc x P 2 S 6 ( x = 0.358) . More recently, Rodriguez's group further expanded the family of Li 2 MP 2 S 6 structure type with new compositions of Fe and Co and reported their magnetic properties .…”

Crystal Structure and Ionic Conductivity of Na2MnP2S6

“…These materials which crystallize in extremely divers crystal structure types attracted much attention for their potentially useful properties, such as magnetism, ferroelectricity, photoluminescence, nonlinear optics, thermoelectricity, electrocatalysis, ionic conductivity, or reversible redox chemistry . Among the thiohypodiphosphate materials, the quaternary compounds A + M 3+ ( P 2 S 6 ) ( A = Li, Na, K, Rb, Cs, Tl, Cu, Ag and M = Al, Sc, V, Cr, Y, In, Sb, La, Ce, Pr, Sm, Tb, Er, Yb, Lu, Bi···) − were the most intensively studied with 38 representatives in the ICSD database followed by the ternary compounds containing divalent cations M 2 2+ ( P 2 S 6 ) ( M = Mg, Ca, Ba, V, Mn, Fe, Co, Ni, Zn, Pd, Cd, Hg, Sn, Pb, Eu···) − with 19 representatives. Ternary thiohypodiphosphate were also reported for monovalent- A 4 + ( P 2 S 6 ) ( A = Li, Na, K, Rb, Cs, Tl, Cu, and Ag), − trivalent- M 4/3 3+ ( P 2 S 6 ) ( M = Al, In, Ga···), , and tetravalent-cations M 4+ ( P 2 S 6 ) ( M = Ti, Zr, Hf, Sn, Th, U···). − Many quaternary compounds of the general formula A 2 + M 2+ ( P 2 S 6 ) ( A = Li, K, Rb, Cs, Ag and M = Mg, Mn, Fe, Ni, Zn, Pd···) − were reported in the literature as well.…”