Na3SbS3: Single Crystal X-ray Diffraction, Raman Spectroscopy, and Impedance Measurements

Degradation at the Na3SbS4/Anode Interface in an Operating All-Solid-State Sodium Battery

All-solid-state sodium batteries utilize earth-abundant elements and are sustainable systems for large-scale energy storage and electric transportation. Replacing flammable carbonate-based electrolytes with solid-state ionic conductors promotes battery safety. Using solid-state electrolytes (SEs) also eliminates the need for packing when fabricating tandem cells, potentially enabling further enhanced energy density. Na₃SbS₄, a Na⁺ conductor, remains stable in dry air and shows high Na⁺ conductivity (σ ≈ 1.0 × 10^-3 S/cm) and is thus a promising SE for applications in sodium batteries. However, upon repeated electrochemical cycling, Na₃SbS₄-containing Na batteries exhibit decaying capacity and limited cycle life, which is likely associated with the decomposition of Na₃SbS₄ at the electrode/electrolyte interface. This work presents an in-depth analysis of the decomposition chemistry occurring at the Na₃SbS₄/anode interface using combined in situ Raman and post-mortem characterization. The results indicate that the SbS₄^3- counterion is electrochemically reduced when experiencing Na⁺ reduction potentials, and this reduction chemistry likely follows multiple pathways. The observed reduction products include SbS₃^3-, the Sb₂S₇^4- dimer, the NaSb binary phase, and Na₂S. We also observed the irreversibility of the decomposition and, as a consequence, the accumulation of the degradation products over cycles. Also notable is the heterogeneity of this degradation chemistry across the interface. Through the spectroelectrochemical characterizations, we reveal the possible mechanisms of the Na₃SbS₄ decomposition at the solid electrolyte/anode interface in an operating device.

Remarkable Infrared Nonlinear Optical, Dielectric, and Strong Diamagnetic Characteristics of Semiconducting K3[BiS3]

The ternary sulfido bismuthate K₃[BiS₃] is synthesized in quantitative yields. The material exhibits nonlinear optical properties with strong second harmonic generation properties at arbitrary wavelengths in the infrared spectral range and a notable laser-induced damage threshold of 5.22 GW cm^-2 for pulsed laser radiation at a wavelength of 1040 nm, a pulse duration of 180 fs, and a repetition rate of 12.5 kHz. K₃[BiS₃] indicates semiconductivity with a direct optical band gap of 2.51 eV. Dielectric and impedance characterizations demonstrate κ values in the range of 6-13 at 1 kHz and a high electrical resistivity. A strong diamagnetic behavior with a susceptibility of -2.73 × 10^-4 m³ kg^-1 at room temperature is observed. These results suggest it is a promising nonlinear optical candidate for the infrared region. The synergic physical characteristics of K₃[BiS₃] provide insight into the correlation of optical, electrical, and magnetic properties.

The cation and anion bonding modes make a difference: an unprecedented layered structure and a tri(hetero)nuclear moiety in thioantimonates(V)

Mixing solutions of M²⁺ (M = Cu²⁺ or Zn²⁺) salts containing cyclam (cyclam = 1,4,8,11-tetraazacyclotetradecane) as the ligand and an aqueous solution of Na₃SbS₄·9H₂O at room temperature led to the crystallization of two new compounds within minutes: {[Cu(cyclam)]₃[SbS₄]₂}_n·20nH₂O (I) and {[Zn(cyclam)]₃[SbS₄]₂}·8H₂O (II). In the structure of I [SbS₄]^3- anions acting as a tridentate ligand join CuN₄S₂ octahedra generating twelve-membered rings by corner-sharing of SbS₄ and CuN₄S₂ units. The rings are condensed into layers, which are stacked onto each other in a 6R polytype manner. The layers contain large pores with the water molecules located between the layers above and below the pores. In contrast, the structure of II comprises a discrete molecular tri(hetero)nuclear moiety with a bidentate [SbS₄]^3- anion connecting two rectangular pyramidal ZnN₄S polyhedra. The crystal water molecules of I and II can be thermally removed, and I and II are recovered by treatment under a humid atmosphere. The EPR spectrum of I indicates the presence of Cu²⁺ cations, which is unusual in the environment of S^2- anions. The different bonding situations and the preferences for the coordination geometries of Cu²⁺ and Zn²⁺ cations are rationalized by DFT based calculations, demonstrating that Cu²⁺ prefers an octahedral environment while Zn²⁺ adopts the square-pyramidal coordination. The pronounced differences in the vibrational spectra are also analyzed with DFT, showing how the different modes are influenced by the differing bond strengths.

Structural diversities in centrosymmetric La8S4Cl8La12S8Cl4[SbS3]8 and non-centrosymmetric Ln12S8Cl8[SbS3]4 (Ln = La and Ce): syntheses, crystal and electronic structures, and optical properties

Three thioantimonides charge compensated by Ln/S/Cl cationic layers, namely, La8S4Cl8La12S8Cl4[SbS3]8 and Ln12S8Cl8[SbS3]4 (Ln = La and Ce), have been discovered by conventional solid-state reactions. The former crystallizes in the centrosymmetric space group Pbcm (no. 57), while the latter adopts the polar non-centrosymmetric space group Cc (no. 9). Both of them contain isolated SbS3 trigonal-pyramidal units, which are connected either with the alternating centric [La8S4Cl8]8+ and mirror-symmetric [La12S8Cl4]16+ cationic layers perpendicular to the [001] direction in La8S4Cl8La12S8Cl4[SbS3]8 or with the acentric [Ln12S8Cl8]12+ cationic layers perpendicular to the [100] direction in Ln12S8Cl8[SbS3]4. Interestingly, the discrete SbS3 trigonal pyramids pack in a centrosymmetric and non-centrosymmetric fashion in La8S4Cl8La12S8Cl4[SbS3]8 and La12S8Cl8[SbS3]4, respectively, which can be ascribed to the different compositions and packing fashions in Ln/S/Cl cationic layers. In addition, optical gaps of 2.31 and 2.60 eV for La12S8Cl8[SbS3]4 and La8S4Cl8La12S8Cl4[SbS3]8, respectively, were determined by UV/vis reflectance spectroscopy, showing a blue shift with respect to La7Sb9S24, which can be attributed to the greater contributions of La to the bottom of the CB as confirmed by the DFT study.

Mechanistic insight of KBiQ2 (Q = S, Se) using panoramic synthesis towards synthesis-by-design

Solid-state synthesis has historically focused on reactants and end products; however, knowledge of reaction pathways, intermediate phases and their formation may provide mechanistic insight of solid-state reactions. With an increased understanding of reaction progressions, design principles can be deduced, affording more predictive power in materials synthesis. In pursuit of this goal, in situ powder X-ray diffraction is employed to observe crystalline phase evolution over the course of the reaction, thereby constructing a “panoramic” view of the reaction from beginning to end. We conducted in situ diffraction studies in the K–Bi–Q (Q = S, Se) system to understand the formation of phases occurring in this system in the course of their reactions. Powder mixtures of K₂Q to Bi₂Q₃ in 1 : 1 and 1.5 : 1 ratios were heated to 800 °C or 650 °C, while simultaneously collecting diffraction data. Three new phases, K₃BiS₃, β-KBiS₂, and β-KBiSe₂, were discovered. Panoramic synthesis showed that K₃BiQ₃ serves an important mechanistic role as a structural intermediate in both chalcogen systems (Q = S, Se) in the path to form the KBiQ₂ structure. Thermal analysis and calculations at the density functional theory (DFT) level show that the cation-ordered β-KBiQ₂ polymorphs are the thermodynamically stable phase in this compositional space, while Pair Distribution Function (PDF) analysis shows that all α-KBiQ₂ structures have local disorder due to stereochemically active lone pair expression of the bismuth atoms. The formation of the β-KBiQ₂ structures, both of which crystallize in the α-NaFeO₂ structure type, show a boundary where the structure can be disordered or ordered with regards to the alkali metal and bismuth. A cation radius tolerance for six-coordinate cation site sharing of ∼ 1.3 is proposed. The mechanistic insight the panoramic synthesis technique provides in the K–Bi–Q system is progress towards the overarching goal of synthesis-by-design.

This work uses in situ powder X-ray diffraction studies to observe crystalline phase evolution over the course of multiple K-Bi-Q (Q = S, Se) reactions, thereby constructing a “panoramic” view of each reaction from beginning to end.

Synthesis and crystal structure of catena-poly[[bis[(2,2';6',2''-terpyridine)-manganese(II)]-μ4-penta-thio-dianti-monato] tetra-hydrate] showing a 1D MnSbS network

The asymmetric unit of the title compound, {[Mn2Sb2S5(C15H11N3)2]·4H2O} n , consists of two crystallographically independent MnII ions, two unique terpyridine ligands, one [Sb2S5]4- anion and four solvent water mol-ecules, all of which are located in general positions. The [Sb2S5]4- anion consists of two SbS3 units that share common corners. Each of the MnII ions is fivefold coordinated by two symmetry-related S atoms of [Sb2S5]4- anions and three N atoms of a terpyridine ligand within an irregular coordination. Each two anions are linked by two [Mn(terpyridine)]2+ cations into chains along the c-axis direction that consist of eight-membered Mn2Sb2S4 rings. These chains are further connected into a three-dimensional network by inter-molecular O-H⋯O and O-H⋯S hydrogen bonds. The crystal investigated was twinned and therefore, a twin refinement using data in HKLF-5 [Sheldrick (2015 ▸). Acta Cryst. C71, 3-8] format was performed.

Bis(2,2′:6′,2′′-terpyridine-κ3N,N′,N′′)nickel(II) bis(perchlorate) hemihydrate

In the title compound, [Ni(C15H11N3)2](ClO4)2·0.5H2O, the Ni2+cation is coordinated by two terpyridine ligands to form a discrete complex and the coordination polyhedron can be described as a slightly distorted octahedron. It crystallizes as a hemihydrate with two perchlorate anions to compensate the charges. In the crystal, one of the two crystallographically independent perchlorate anions is involved in O—H...O hydrogen bonding to the water molecules, where two inversion-related water molecules link two inversion-related perchlorate anions into a ring with anR42(12) loop. The O-atom position of the water molecule is only half occupied,i.e.only half of the anions are involved in hydrogen bonding. A similar arrangement of two anions is also observed for the second crystallographically independent perchlorate anion but no water molecules are located between the anions. The cationic complex and the perchlorate anions are additionally linked by a number of weak C—H...O hydrogen bonds, forming a three-dimensional supramolecular structure. The crystal structure of the monohydrate of the same complex has been reported [Bakeret al.(1995).Aust. J. Chem.48, 1373–1378].

Li17Sb13S28: A New Lithium Ion Conductor and addition to the Phase Diagram Li2S-Sb2S3

Li17Sb13S28 was synthesized by solid-state reaction of stoichiometric amounts of anhydrous Li2S and Sb2S3. The crystal structure of Li17Sb13S28 was determined from dark-red single crystals at room temperature. The title compound crystallizes in the monoclinic space group C2/m (no. 12) with a=12.765(2) Å, b=11.6195(8) Å, c=9.2564(9) Å, β=119.665(6)°, V=1193.0(2) Å(3), and Z=4 (data at 20 °C, lattice constants from powder diffraction). The crystal structure contains one cation site with a mixed occupation by Li and Sb, and one with an antimony split position. Antimony and sulfur form slightly distorted tetragonal bipyramidal [SbS5E] units (E=free electron pair). Six of these units are arranged around a vacancy in the anion substructure. The lone electron pairs E of the antimony(III) cations are arranged around these vacancies. Thus, a variant of the rock salt structure type with ordered vacancies in the anionic substructure results. Impedance spectroscopic measurements of Li17Sb13S28 show a specific conductivity of 2.9×10(-9) Ω(-1) cm(-1) at 323 K and of 7.9×10(-6) Ω(-1) cm(-1) at 563 K, the corresponding activation energy is EA=0.4 eV below 403 K and EA=0.6 eV above. Raman spectra are dominated by the Sb-S stretching modes of the [SbS5] units at 315 and 341 cm(-1) at room temperature. Differential thermal analysis (DTA) measurements of Li17Sb13S28 indicate peritectic melting at 854 K.