Crystal chemical data of high- (HT) and low-temperature (LT) modifications of lithium argyrodites with the compositions Li(7)PCh(6) (Ch=S, Se), Li(6)PCh(5)X (X=Cl, Br, I), Li(6)AsS(5)Br, and Li(6)AsCh(5)I (Ch=S, Se) based on single-crystal, powder X-ray (113 K

The development of safe and long-lasting all-solid-state lithium-ion batteries needs electrolytes with exceptionally good transport properties. Here, we report on the combination of several solid-state nuclear magnetic resonance (NMR) techniques which have been used to precisely probe short-range as well as long-range Li + dynamics in Li 6 PS 5 Br from an atomic-scale point of view. NMR data clearly reveal an extraordinary high Li diffusivity. This manifests in so-called diffusion-induced spin−lattice relaxation NMR rate peaks showing up at temperatures as low as 260 K. From a quantitative point of view, at ambient temperature the Li jump rate is of the order of 10 9 s −1 which corresponds to a Li + conductivity in order of 10 −3 to 10 −2 S/cm, thus, indicating "liquid-like" Li + diffusion behavior in Li 6 PS 5 Br.

Li(7)PS(6) and Li(7)PSe(6) belong to a class of new solids that exhibit high Li(+) mobility. A series of quaternary solid solutions Li(7)PS(6-x)Se(x) (0 < or = x < or = 6) were characterised by X-ray crystallography and magic-angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. The high-temperature (HT) modifications were studied by single-crystal investigations (both F43m, Z=4, Li(7)PS(6): a=9.993(1) A, Li(7)PSe(6): a=10.475(1) A) and show the typical argyrodite structures with strongly disordered Li atoms. HT-Li(7)PS(6) and HT-Li(7)PSe(6) transform reversibly into low-temperature (LT) modifications with ordered Li atoms. X-ray powder diagrams show the structures of LT-Li(7)PS(6) and LT-Li(7)PSe(6) to be closely related to orthorhombic LT-alpha-Cu(7)PSe(6). Single crystals of the LT modifications are not available due to multiple twinning and formation of antiphase domains. The gradual substitution of S by Se shows characteristic site preferences closely connected to the functionalities of the different types of chalcogen atoms (S, Se). High-resolution solid-state (31)P NMR is a powerful method to differentiate quantitatively between the distinct (PS(4-n)Se(n))(3-) local environments. Their population distribution differs significantly from a statistical scenario, revealing a pronounced preference for P-S over P-Se bonding. This preference, shown for the series of LT samples, can be quantified in terms of an equilibrium constant specifying the melt reaction Se(P)+S(2-) <==>S(P)+Se(2-), prior to crystallisation. The (77)Se MAS-NMR spectra reveal that the chalcogen distributions in the second and third coordination sphere of the P atoms are essentially statistical. The number of crystallographically independent Li atoms in both LT modifications was analysed by means of (6)Li{(7)Li} cross polarisation magic angle spinning (CPMAS).

Lithium-rich argyrodites belong to a relatively new group of fast ion conducting solids. They might serve as powerful electrolytes in all-solid-state lithium-ion batteries being, from a medium-term point of view, the key technology when safe energy storage systems have to be developed. Spin-lattice relaxation (SLR) nuclear magnetic resonance (NMR) measurements carried out in the rotating frame of reference turned out to be the method of choice to study Li dynamics in argyrodites. When plotted as a function of the inverse temperature, the SLR rates log10(R1ρ) reveal an asymmetric diffusion-induced rate peak. The rate peak contains information on the Li jump rate, the activation energy of the hopping process as well as correlation effects. In particular, considering the high-temperature flank of the SLR NMR rate peak recorded in the rotating frame of reference, an activation energy of approximately 0.49 eV is found. This value represents long-range lithium jump diffusion in crystalline Li7PSe6. As an example, at 325 K the Li jump rate determined from SLR NMR is in the order of 1.4 × 10(5) s(-1). The pronounced asymmetry of the rate peak R1ρ(1/T) points to correlated Li motion. It is comparable to that which is typically found for structurally disordered materials showing a broad range of correlation times.

A comprehensive multinuclear (7Li, 31P, 75As, 77Se, 127I) NMR study has been conducted to characterize local structural configurations and atomic distributions in the crystallographically ordered solid solutions of composition Li6PS5-x Se x I (0 ≤ x ≤ 1) and in Li6AsS5I. Throughout the composition range, structural ordering between the atoms on the Wyckoff sites 4a and 4c is maintained, with the I− ions exclusively occupying the 4a sites. 31P magic-angle spinning nuclear magnetic resonance (MAS NMR) can serve to differentiate between the various possible PS4-n Se n 3− tetrahedral units in a quantitative fashion, indicating a preference of P-S relative to P-Se bonding. Each individual PS4-n Se n 3− tetrahedron is represented by a peak cluster containing up to five resonances, representing the five different configurations in which the PCh4 3− units are surrounded by the four closest chalcogenide anions occupying the 4c sites; the distribution of S2− and Se2− over these sites is close to statistical. Non-linear 7Li chemical shift trends as a function of x are interpreted to indicate that the Coulombic traps created by sulfur-rich PS4-n Se n 3− ions (n ≥ 2) within the energy landscape of the lithium ions are deeper than those of the other anionic species present (i.e. selenium-richer PCh4 3− tetrahedra, isolated chalcogenide or iodide ions), causing the Li+ ions to spend on average more time near them. Temperature dependent static 7Li NMR linewidths measured on Li6PS5I and Li6AsS5I indicate a two-step motional narrowing process characterized by a clear dynamic distinction between a more rapid localized intra-cage process and a slower, long-range inter-cage process. In the solid solutions this differentiation gradually disappears, leading to an overall increase of lithium ionic mobility with increasing selenium content, which can be attributed to the influences of higher anionic polarizability and a widening of the lithium migration pathways caused by lattice expansion. Furthermore, the low-temperature phase transition in Li6PS5I, which tends to immobilize the lithium ions below 170 K, is suppressed in the solid solutions. The results offer interesting new insights into the -structure/ionic mobility correlations in this new class of compounds.

A comprehensive multinuclear (7Li, 31P, 35Cl, 77Se, 79Br) nuclear magnetic resonance (NMR) study has been conducted to characterize local structural configurations and atomic distributions in the crystallographically disordered solid solutions of composition Li6PS5−x Se x X (0 ≤ x ≤ 1, X = Cl, Br) with the Argyrodite structure. In contrast to the situation with the corresponding iodide homologs, there is no structural ordering between the 4a and 4c sites, with the halide ions occupying both of them with close to statistical probabilities. Nevertheless, throughout the composition range, the 16e Wyckoff sites of the Argyrodite structure are exclusively occupied by the chalcogen atoms, forming PY4 3− (Y = S, Se) tetrahedra, indicating the absence of P-halogen bonds. 31P magic-angle spinning (MAS)-NMR can serve to differentiate between the various possible PS4−n Se n 3− tetrahedral units in a quantitative fashion. Compared to the case of the anion-ordered Li6PS5−x Se x I solid solutions, the preference of P–S over P–Se bonding is significantly stronger, but it is weaker than in the halide free solid solutions Li7PS6−x Se x . Each individual PS4−n Se n 3− tetrahedron is represented by a peak cluster of up to five resonances, representing the five different configurations in which the PY4 3− ions are surrounded by the four closest chalcogenide and halide anions occupying the 4c sites; this distribution is close to statistical and can be used to deduce deviations of sample compositions from ideal stoichiometry. Non-linear 7Li chemical shift trends as a function of x are interpreted to indicate that the Coulombic traps created by sulfur-rich PS4−n Se n 3− ions (n ≤ 2) within the energy landscape of the lithium ions are deeper than those of the other anionic species present (i.e., selenium-richer PY4 3− tetrahedra, isolated chalcogenide or iodide ions), causing the Li+ ions to spend on average more time near them. Temperature dependent static 7Li NMR linewidths indicate higher mobility in the present systems than in the previously studied Li6PS5−x Se x I solid solutions. Unlike the situation in Li6PS5−x Se x I no rate distinction between intra-cage and inter-cage ionic motion is evident. Lithium ionic mobility increases with increasing selenium content. This effect can be attributed to the influences of higher anionic polarizability and a widening of the lithium ion migration pathways caused by lattice expansion. The results offer interesting new insights into the structure/ionic mobility correlations in this new class of compounds.

A new organic–inorganic two-dimensional hybrid compound, [CuMoO4(C2H8N2)], has been hydro­thermally synthesized at 443 K. The unit cell contains layers composed of CuN2O4 octa­hedra and MoO4 tetra­hedra. Corner-sharing MoO4 and CuN2O4 polyhedra form CuMoO4 bimetallic sites that are joined together through O atoms, forming an edge-sharing Cu2Mo2O4 chain along the c axis. The one-dimensional chains are further linked through bridging O atoms that join the Cu and Mo atoms into respective chains along the b axis, thus establishing layers in the bc plane. The ethyl­enediamine ligand is coordinated to the Cu atom through its two N atoms and is oriented perpendicularly to the two-dimensional –Cu—O—Mo– layers. The average distance between adjacent layers, as calculated by consideration of the closest and furthest distances between two layers, is 8.7 Å. The oxidation states of the Mo and Cu atoms of VI and II, respectively, were confirmed by bond-valence sum calculations.

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