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Joos M, Conrad M, Rad A, Kaghazchi P, Bette S, Merkle R, Dinnebier RE, Schleid T, Maier J. Ion transport mechanism in anhydrous lithium thiocyanate LiSCN Part I: ionic conductivity and defect chemistry. Phys Chem Chem Phys 2022; 24:20189-20197. [PMID: 35971978 DOI: 10.1039/d2cp01836e] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
This work reports on the ion transport properties and defect chemistry in anhydrous lithium thiocyanate Li(SCN), which is a pseudo-halide Li+ cation conductor. An extensive doping study was conducted, employing magnesium, zinc and cobalt thiocyanate as donor dopants to systematically vary the conductivity and derive a defect model. The investigations are based on impedance measurements and supported by other analytical techniques such as X-ray powder diffraction (XRPD), infrared (IR) spectroscopy, and density functional theory (DFT) calculations. The material was identified as Schottky disordered with lithium vacancies being the majority mobile charge carriers. In the case of Mg2+ as dopant, defect association with lithium vacancies was observed at low temperatures. Despite a comparably low Schottky defect formation enthalpy of (0.6 ± 0.3) eV, the unexpectedly high lithium vacancy migration enthalpy of (0.89 ± 0.08) eV distinguishes Li(SCN) from the chemically related lithium halides. A detailed defect model of Li(SCN) is presented and respective thermodynamic and kinetic data are given. The thiocyanate anion (SCN)- has a significant impact on ion mobility due to its anisotropic structure and bifunctionality in forming both Li-N and Li-S bonds. More details about the impact on ion dynamics at local and global scale, and on the defect chemical analysis of the premelting regime at high temperatures are given in separate publications (Part II and Part III).
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Affiliation(s)
- Markus Joos
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - Maurice Conrad
- Institut für Anorganische Chemie, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany.,Present address; Institut für Photovoltaik, University of Stuttgart, Pfaffenwaldring 47, 70569, Stuttgart, Germany
| | - Ashkan Rad
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - Payam Kaghazchi
- Forschungszentrum Jülich GmbH, Institute of Energy and Climate Research, Materials Synthesis and Processing (IEK-1), 52425, Jülich, Germany
| | - Sebastian Bette
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany. .,Institut für Anorganische Chemie, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Rotraut Merkle
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - Robert E Dinnebier
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
| | - Thomas Schleid
- Institut für Anorganische Chemie, University of Stuttgart, Pfaffenwaldring 55, 70569, Stuttgart, Germany
| | - Joachim Maier
- Max Planck Institute for Solid State Research, Heisenbergstr. 1, 70569, Stuttgart, Germany.
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Joos M, Conrad M, Moudrakovski I, Terban MW, Rad A, Kaghazchi P, Merkle R, Dinnebier RE, Schleid T, Maier J. Ion Transport Mechanism in Anhydrous Lithium Thiocyanate LiSCN Part II: Frequency Dependence and Slow Jump Relaxation. Phys Chem Chem Phys 2022; 24:20198-20209. [DOI: 10.1039/d2cp01837c] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Specific aspects of the Li+ cation conductivity of anhydrous Li(SCN) are investigated, in particular the high migration enthalpy of lithium vacancies. Close inspection of impedance spectra and conductivity data reveals...
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