Synthesis and Crystal Structure of a New Alkali Metal Tantalum Sulfide: Na3TaS4

Herzog, S.; Näther, Christian; Dürichen, Peter; Bensch, Wolfgang

doi:10.1002/(sici)1521-3749(1998120)624:12<2021::aid-zaac2021>3.0.co;2-0

Cited by 9 publications

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“…It is also expected to be dynamically stable given the absence of negative frequency modes in the phonon dispersion curve (Figure S11), indicating that there are no phonon modes which could lead to a symmetry-lowering phase transition. However, considering the unsuccessful attempts to synthesize this compound, which always results in the formation of V 5 S 8 , S, and MgS, Mg 3 V 2 S 8 appears to be metastable with respect to the other Mg–V–S phases in the phase diagram (see the Materials and Methods section in the Supporting Information for synthesis details − ).…”

Section: Resultsmentioning

confidence: 99%

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

et al. 2020

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For magnesium ion batteries (MIBs) to be used commercially, new cathodes must be developed that show stable reversible Mg intercalation. VS 4 is one such promising material, with vanadium and disulfide anions [S 2 ] 2− forming onedimensional linear chains, with a large interchain spacing (5.83 Å) enabling reversible Mg insertion. However, little is known about the details of the redox processes and structural transformations that occur upon Mg intercalation and deintercalation. Here, employing a suite of local structure characterization methods including X-ray photoelectron spectroscopy (XPS), V and S X-ray absorption nearedge spectroscopy (XANES), and 51 V Hahn echo and magic-angle turning with phase-adjusted sideband separation (MATPASS) NMR, we show that the reaction proceeds via internal electron transfer from V 4+ to [S 2 ] 2− , resulting in the simultaneous and coupled oxidation of V 4+ to V 5+ and reduction of [S 2 ] 2− to S 2− . We report the formation of a previously unknown intermediate in the Mg−V−S compositional space, Mg 3 V 2 S 8 , comprising [VS 4 ] 3− tetrahedral units, identified by using density functional theory coupled with an evolutionary structure-predicting algorithm. The structure is verified experimentally via X-ray pair distribution function analysis. The voltage associated with the competing conversion reaction to form MgS plus V metal directly is similar to that of intermediate formation, resulting in two competing reaction pathways. Partial reversibility is seen to re-form the V 5+ and S 2− containing intermediate on charging instead of VS 4 . This work showcases the possibility of developing a family of transition metal polychalcogenides functioning via coupled cationic−anionic redox processes as a potential way of achieving higher capacities for MIBs.

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Section: Resultsmentioning

confidence: 99%

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

et al. 2020

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“…With tantalum in the oxidation state +5, the isolated TaS 4 tetrahedra have a 3-fold negative charge, and compared to the rare chemistry of phosphidotantalates, ternary and quaternary sulfidotantalates containing alkali metals are more common. For example, isolated TaS 4 tetrahedra were found in the ternary phases Na 3 TaS 4 , K 3 TaS 4 , Rb 3 TaS 4 , and Cs 3 TaS 4 . Such tetrahedra also occur in the quaternary phases RbBaTaS 4 and LiRb 2 TaS 4 , and in Cu- and Ag-substituted compounds like K 3 Cu 3 Ta 2 S 8 , K 2 AgTaS 4 , K 3 Ag 3 Ta 2 S 8 , Rb 2 CuTaS 4 , Rb 2 AgTaS 4 , and Cs 2 AgTaS 4 .…”

Section: Introductionmentioning

confidence: 99%

Na₇TaP₄: A Ternary Sodium Phosphidotantalate Containing [TaP₄]^7– Tetrahedra

et al. 2020

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While lithium phosphides have been investigated intensively, very little is known about the corresponding sodium-based phosphides. Here, we report on the first ternary Na–Ta–P compound Na7TaP4, which is easily accessible via ball milling of the elements and subsequent annealing. The single crystal X-ray structure determination [monoclinic symmetry; space group P21/c; and lattice parameters a = 11.5604(4), b = 8.1530(3), c = 11.5450(5) Å, and β = 101.602(3)°] reveals [TaP4]7– tetrahedra, which are surrounded by Na+ counterions. Na7TaP4 crystallizes in a new structure type. The structure can be described as a strongly distorted hexagonal close packing of P atoms, in which the Ta atoms are located in tetrahedral voids, and Na atoms occupy all octahedral voids and additionally 3/8 of the tetrahedral voids. The possibility to increase the ion conductivity by changing the number of charge carriers through aliovalent substitution in compounds containing [SiP4]8– and [AlP4]9– is considered. The 31P and 23Na MAS NMR as well as the Raman spectra are in accordance with the structure model, and band structure calculations predict a direct band gap of 2.9 eV.

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Oxide Addition to a Reactive Polysulfide Flux: Synthesis of K4Ba[Ti6OS20] Containing Isolated [Ti6OS8(S2)6]6− Clusters

Huang

Ibers

2001

Angew. Chem.

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Two crystal modifications of the title compound are synthesized by the reactive flux method from K 2 S, BaS, Ti, TiO 2 , and S (hexagonal modification: 823 K, 3 d, 80% yield, orthorhombic modification: 873 K, 2 d, 70% yield). As revealed by single crystal XRD, the hexagonal modification crystallizes in the space group P6 3 22 with Z = 2 and the orthorhombic modification in the space group Fddd with Z = 8. Both modifications consist of well-separated [Ti 6 OS 8 (S 2 ) 6 ] 6− anionic clusters and K + and Ba

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Synthesis and Crystal Structure of a New Alkali Metal Tantalum Sulfide: Na3TaS4

Cited by 9 publications

References 0 publications

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

Na₇TaP₄: A Ternary Sodium Phosphidotantalate Containing [TaP₄]^7– Tetrahedra

Oxide Addition to a Reactive Polysulfide Flux: Synthesis of K4Ba[Ti6OS20] Containing Isolated [Ti6OS8(S2)6]6− Clusters

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Synthesis and Crystal Structure of a New Alkali Metal Tantalum Sulfide: Na3TaS4

Cited by 9 publications

References 0 publications

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

Exploring Cation–Anion Redox Processes in One-Dimensional Linear Chain Vanadium Tetrasulfide Rechargeable Magnesium Ion Cathodes

Na7TaP4: A Ternary Sodium Phosphidotantalate Containing [TaP4]7– Tetrahedra

Oxide Addition to a Reactive Polysulfide Flux: Synthesis of K4Ba[Ti6OS20] Containing Isolated [Ti6OS8(S2)6]6− Clusters

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Na₇TaP₄: A Ternary Sodium Phosphidotantalate Containing [TaP₄]^7– Tetrahedra