Li5SnP3: a member of the series Li10+4xSn2−xP6 for x=0 comprising the fast lithium‐ion conductors Li8SnP4 (x=0.5) and Li14SnP6 (x=1)

The targeted search for suitable solid‐state ionic conductors requires a certain understanding of the conduction mechanism and the correlation of the structures and the resulting properties of the material. Thus, the investigation of various ionic conductors with respect to their structural composition is crucial for the design of next‐generation materials as demanded. We report here on Li(5)SnP(3) which completes with x=0 the series Li(10+4x )Sn(2−x )P(6) of the fast lithium‐ion conductors α‐ and β‐Li(8)SnP(4) (x=0.5) and Li(14)SnP(6) (x=1). Synthesis, crystal structure determination by single‐crystal and powder X‐ray diffraction methods, as well as (6)Li, (31)P and (119)Sn MAS NMR and temperature‐dependent (7)Li NMR spectroscopy together with electrochemical impedance studies are reported. The correlation between the ionic conductivity and the occupation of octahedral and tetrahedral sites in a close‐packed array of P atoms in the series of compounds is discussed. We conclude from this series that in order to receive fast ion conductors a partial occupation of the octahedral vacancies seems to be crucial

Fast Ionic Conductivity in the Most Lithium-Rich Phosphidosilicate Li14SiP6.

Solid electrolytes with superionic conductivity are required as a main component for all-solid-state batteries. Here we present a novel solid electrolyte with three-dimensional conducting pathways based on "lithium-rich" phosphidosilicates with ionic conductivity of σ > 10-3 S cm-1 at room temperature and activation energy of 30-32 kJ mol-1 expanding the recently introduced family of lithium phosphidotetrelates. Aiming toward higher lithium ion conductivities, systematic investigations of lithium phosphidosilicates gave access to the so far lithium-richest compound within this class of materials. The crystalline material (space group Fm3m), which shows reversible thermal phase transitions, can be readily obtained by ball mill synthesis from the elements followed by moderate thermal treatment of the mixture. Lithium diffusion pathways via both tetrahedral and octahedral voids are analyzed by temperature-dependent powder neutron diffraction measurements in combination with maximum entropy method and DFT calculations. Moreover, the lithium ion mobility structurally indicated by a disordered Li/Si occupancy in the tetrahedral voids plus partially filled octahedral voids is studied by temperature-dependent impedance and 7Li NMR spectroscopy

Na₃Ge₂P₃: A Zintl Phase Featuring [P₃Ge–GeP₃] Dimers as Building Blocks

Recently, ternary lithium phosphidotetrelates have attracted interest particularly due to their high ionic conductivities, while corresponding sodium and heavier alkali metal compounds have been less investigated. Hence, we report the synthesis and characterization of the novel ternary sodium phosphidogermanate Na3Ge2P3, which is readily accessible via ball milling of the elements and subsequent annealing. According to single crystal X-ray structure determination, Na3Ge2P3 crystallizes in the monoclinic space group P21/c (no. 14.) with unit cell parameters of a = 7.2894(6) Å, b = 14.7725(8) Å, c = 7.0528(6) Å, β = 106.331(6)° and forms an unprecedented two-dimensional polyanionic network in the b/c plane of interconnected [P3Ge–GeP3] building units. The system can also be interpreted as differently sized ring structures that interconnect and form a two-dimensional network. A comparison with related ternary compounds from the corresponding phase system as well as with the binary compound GeP shows that the polyanionic network of Na3Ge2P3 resembles an intermediate step between highly condensed cages and discrete polyanions, which highlights the structural variety of phosphidogermanates. The structure is confirmed by 23Na- and 31P-MAS NMR measurements and Raman spectroscopy. Computational investigation of the electronic structure reveals that Na3Ge2P3 is an indirect band gap semiconductor with a band gap of 2.9 eV

A Combined Metal-Halide/Metal Flux Synthetic Route towards Type-I Clathrates

Peer reviewe

Fast Lithium ion conduction in Lithium phosphidoaluminates

Solid electrolyte materials are crucial for the development of high‐energy‐density all‐solid‐state batteries (ASSB) using a nonflammable electrolyte. In order to retain a low lithium‐ion transfer resistance, fast lithium ion conducting solid electrolytes are required. We report on the novel superionic conductor Li9AlP4 which is easily synthesised from the elements via ball‐milling and subsequent annealing at moderate temperatures and which is characterized by single‐crystal and powder X‐ray diffraction. This representative of the novel compound class of lithium phosphidoaluminates has, as an undoped material, a remarkable fast ionic conductivity of 3 mS cm−1 and a low activation energy of 29 kJ mol−1 as determined by impedance spectroscopy. Temperature‐dependent 7Li NMR spectroscopy supports the fast lithium motion. In addition, Li9AlP4 combines a very high lithium content with a very low theoretical density of 1.703 g cm−3. The distribution of the Li atoms over the diverse crystallographic positions between the [AlP4]9− tetrahedra is analyzed by means of DFT calculations

Charged Si9 Clusters in Neat Solids and the Detection of [H2Si9]2− in Solution

Polyanionic silicon clusters are provided by the Zintl phases K4Si4, comprising [Si4]4− units, and K12Si17, consisting of [Si4]4− and [Si9]4− clusters. A combination of solid-state MAS-NMR, solution NMR, and Raman spectroscopy, electrospray ionization mass spectrometry, and quantum-chemical investigations was used to investigate four- and nine-atomic silicon Zintl clusters in neat solids and solution. The results were compared to 29Si isotope-enriched samples. 29Si-MAS NMR and Raman shifts of the phase-pure solids K4Si4 and K12Si17 were interpreted by quantum-chemical calculations. Extraction of [Si9]4− clusters from K12Si17 with liquid ammonia/222crypt and their transfer to pyridine yields in a red solid containing Si9 clusters. This compound was characterized by elemental and EDX analyses and 29Si-MAS NMR and Raman spectroscopy. Charged Si9 clusters were detected by 29Si NMR in solution. 29Si and 1H NMR spectra reveal the presence of the [H2Si9]2− cluster anion in solution.Peer reviewe

Toward tunable immobilized molecular catalysts: Functionalizing the methylene bridge of bis(N-heterocyclic carbene) ligands

A new immobilization mode for methylene-bridged bis(NHC) (NHC=N-heterocyclic carbene) ligand systems is presented, allowing fine-tuning of the steric and electronic properties of the bidentate ligand. For example, four hydroxymethyl-functionalized imidazolium salts (1 a-c and 2 a) and three bis(NHC) Pd complexes 3 a, 3 b, and 4 a are described. The chloro-functionalized bis(NHC) Pd complex 4 a was obtained quantitatively by conversion of the hydroxyl substituent of complex 3 a into a chloro substituent by employing thionyl chloride. All three bis(NHC) complexes 3 a, 3 b, and 4 a were characterized by NMR spectroscopy, elemental analysis, mass spectrometry, and single-crystal X-ray diffraction. Two different synthetic routes were applied to immobilize the bis(NHC) Pd complex 3 a on polystyrene. The obtained heterogeneous catalyst 5 b was utilized for Suzuki-Miyaura cross-coupling reactions and could be recycled without significant activity loss in four runs. Furthermore, the water-soluble homogeneous catalyst 3 a itself could be employed for Suzuki-Miyaura cross-coupling reactions in water

Aliovalent substitution in phosphide-based materials – Crystal structures of Na10AlTaP6 and Na3GaP2 featuring edge-sharing EP4 tetrahedra (E=Al/Ta and Ga)

Funding Information: The work was carried out as part of the research project ASSB coordinated by ZAE Bayern. The project is funded by the Bavarian Ministry of Economic Affairs, Regional Development and Energy. We thank Christoph Wallach for recording the Raman spectrum. Open access funding enabled and organized by Projekt DEAL. Publisher Copyright: © 2021 The Authors. Zeitschrift für anorganische und allgemeine Chemie published by Wiley-VCH GmbHRecently, ternary lithium phosphides have been studied intensively owing to their high lithium ion conductivities. Much less is known about the corresponding sodium-containing compounds, and during investigations aiming for sodium phosphidotrielates, two new compounds have been obtained. The sodium phosphidoaluminumtantalate Na10AlTaP6, at first obtained as a by-product from the reaction with the container material, crystallizes in the monoclinic space group P21/n (no. 14) with lattice parameters of a=8.0790(3) Å, b=7.3489(2) Å, c=13.2054(4) Å, and β=90.773(2)°. The crystal structure contains dimers of edge-sharing [(Al0.5Ta0.5)P4] tetrahedra with a mixed Al/Ta site. DFT calculations support the presence of this type of arrangement instead of homonuclear Al2P6 or Ta2P6 dimers. The 31P and 23Na MAS NMR as well as the Raman spectra confirm the structure model. The assignment of the chemical shifts is confirmed applying the DFT-PBE method on the basis of the ordered structural model with mixed AlTaP6 dimers. Thesodium phosphidogallate Na3GaP2 crystallizes in the orthorhombic space group Ibam (no. 72) with lattice parameters of a=13.081(3) Å, b=6.728(1) Å, and c=6.211(1) Å and is isotypic to Na3AlP2. Na3GaP2 exhibits linear chains of edge-sharing 1∞[GaP4/2] tetrahedra. For both compounds band structure calculations predict indirect band gaps of 2.9 eV.Peer reviewe

Synthesis and Characterization of the Lithium-Rich Phosphidosilicates Li₁₀Si₂P₆ and Li₃Si₃P₇

The lithium phosphidosilicates Li₁₀Si₂P₆ and Li₃Si₃P₇ are obtained by high-temperature reactions of the elements or including binary Li–P precursors. Li₁₀Si₂P₆ (<i>P</i>2₁/<i>n</i>, <i>Z</i> = 2, <i>a</i> = 7.2051(4) Å, <i>b</i> = 6.5808(4) Å, <i>c</i> = 11.6405(7) Å, β = 90.580(4)°) features edge-sharing SiP₄ double tetrahedra forming [Si₂P₆]^10– units with a crystal structure isotypic to Na₁₀Si₂P₆ and Na₁₀Ge₂P₆. Li₃Si₃P₇ (<i>P</i>2₁/<i>m</i>, <i>Z</i> = 2, <i>a</i> = 6.3356(4) Å, <i>b</i> = 7.2198(4) Å, <i>c</i> = 10.6176(6) Å, β = 102.941(6)°) crystallizes in a new structure type, wherein SiP₄ tetrahedra are linked via common vertices and which are further connected by polyphosphide chains to form unique _∞²[Si₃P₇]^3– double layers. The two-dimensional Si–P slabs that are separated by Li atoms can be regarded as three covalently linked atoms layers: a defect α-arsenic type layer of P atoms sandwiched between two defect wurzite-type Si₃P₄ layers. The single crystal and powder X-ray structure solutions are supported by solid-state ⁷Li, ²⁹Si, and ³¹P magic-angle spinning NMR measurements