Anion Ordering to Induce Polar Metal Coordinations and Single Ion Anisotropies.

• Applicant: Dr. Silke Hampel, since 10/2019
• Subject Area: Solid State and Surface Chemistry, Material Synthesis ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: from 2017 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 388667006

• Final Report Year: 2023

Final Report Abstract

The aim of the project was the synthesis of new mixed anion compounds with heteroleptic coordination geometries. The synthesis should be better understood along with a fundamental understanding of the structure-property relationships. New materials with new properties were expected to establish new exciting application-oriented research areas or directly an application. In homoleptic atomic coordination (homós: Greek for equal), a cation is coordinated by several equal anions. In heteroleptic (héteros: Greek for different) atomic coordination the cation is surrounded by at least two different anions. Since the anions differ in their properties such as charge, ion radii, electronegativity, polarizability, a distortion of the coordination polyhedron occurs. This Jahn-Teller effect results in an octahedral compression/stretching caused by the degeneracy of the molecular orbitals of the transition metal. Thus, mixed anion compounds offer new additional possibilities to specifically induce a distortion of the coordination polyhedron, therefore influencing the local and electronic structure and eventually achieving a change in properties. In this project, several new materials were successfully synthesized either by solid-state reaction (SSR) or by chemical vapor phase transport (CVT). In principle, these new materials can be divided into two classes of materials. One class is the bichalcogenides with the general composition (Li2TM)ChO (TM = Fe, Mn, Co; Ch = S, Se). All compounds have a cubic antiperovskite crystal structure, are prepared from low-cost, non-toxic precursors and exhibit chemical flexibility, which allows to improve the already promising properties such as high lithium ion diffusion, thermal stability as well as the high practical specific capacity. This makes them a promising alternative cathode material for lithium ion batteries. The compounds (Li2Fe)SO, and the solid-state solutions (Li2Fe)S1-xSexO, (Li2Fe1-yMny)SO were concretely investigated. Furthermore, the new compound CsBa6V4S12ClO4 was identified, also a bichalcogenide. This compound has a deep-red color due to a low-energy charge transfer, which can be explained by an electron transfer from S2- to V5+. The other class is the 2D Janus materials with the new representative RhSeCl. RhSeCl crystals have a plate-like morphology typical of 2D materials and crystallize in the non-centrosymmetric space group P63mc. The crystal structure consists of alternating layers of edge-linked Rh octahedra, whereby the octahedral angle is distorted by the heteroleptic coordination. Polycrystalline powder was prepared by SSR and single crystals by CVT. Magnetization measurements show the diamagnetic nature of these compounds.

Publications

• Extended Chemical Flexibility of Cubic Anti-Perovskite Lithium Battery Cathode Materials. Inorganic Chemistry, 57(21), 13296-13299.
  Lai, Kwing To; Antonyshyn, Iryna; Prots, Yurii & Valldor, Martin
  
• Operando Studies of Antiperovskite Lithium Battery Cathode Material (Li2Fe)SO. ACS Applied Energy Materials, 1(11), 6593-6599.
  Mikhailova, Daria; Giebeler, Lars; Maletti, Sebastian; Oswald, Steffen; Sarapulova, Angelina; Indris, Sylvio; Hu, Zhiwei; Bednarcik, Jozef & Valldor, Martin
  
• Bichalcogenide Model Systems for Magnetic Chains with Variable Spin Sizes and Optional Crystallographic Inversion Symmetry. Inorganic Chemistry, 58(18), 11978-11982.
  Valldor, Martin & Morrow, Ryan
  
• Synthesis, Crystal Structure, and Optical Characterization of the Sulfide Chloride Oxide CsBa6V4S12ClO4 with a Near-Infrared Fluorescence. Inorganic Chemistry, 58(21), 14728-14733.
  Valldor, Martin; Galle, Lydia; Eichler, Franziska; Wolf, André & Morrow, Ryan
  
• Impact of inversion symmetry on a quasi-1D S  =  1 system. Journal of Physics: Condensed Matter, 32(22), 225802.
  Kim, J. K.; Ranjith, K. M.; Burkhardt, U.; Prots, Yu; Baenitz, M. & Valldor, M.
  
• Synthesis of (Li2Fe1–yMny)SO Antiperovskites with Comprehensive Investigations of (Li2Fe0.5Mn0.5)SO as Cathode in Li-ion Batteries. Inorganic Chemistry, 59(21), 15626-15635.
  Gorbunov, Mikhail V.; Carrocci, Salvatore; Maletti, Sebastian; Valldor, Martin; Doert, Thomas; Hampel, Silke; Gonzalez, Martinez Ignacio Guillermo; Mikhailova, Daria & Gräßler, Nico
  
• Tuning the electrochemical properties by anionic substitution of Li-rich antiperovskite (Li2Fe)S1−xSexO cathodes for Li-ion batteries. Journal of Materials Chemistry A, 9(40), 23095-23105.
  Mohamed, M. A. A.; Gorbunov, Mikhail V.; Valldor, Martin; Hampel, Silke; Gräßler, Nico & Mikhailova, Daria
  
• Crystal growth of the 2D Janus rhodium chalcohalide RhSeCl. Inorganic Chemistry Frontiers, 10(10), 2911-2916.
  Nowak, Domenic; Valldor, Martin; Rubrecht, Bastian; Froeschke, Samuel; Eltoukhy, Samar; Büchner, Bernd; Hampel, Silke & Gräßler, Nico
  
• Mechanochemical synthesis of Li-rich (Li2Fe)SO cathode for Li-ion batteries. Green Chemistry, 25(10), 3878-3887.
  Mohamed, M. A. A.; Saadallah, H. A. A.; Gonzalez-Martinez, I. G.; Hantusch, M.; Valldor, M.; Büchner, B.; Hampel, S. & Gräßler, N.