Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride
The discovery of new inorganic magnesium electrolytes may act as a foundation for the rational design of novel types of solid-state batteries. Here we investigated a new type of organic-inorganic metal hydride, isopropylamine magnesium borohydride, Mg(BH<sub>4</sub>)<sub>2</sub&...
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MDPI AG
2022-12-01
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| Series: | Inorganics |
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| Online Access: | https://www.mdpi.com/2304-6740/11/1/17 |
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| author | Lasse G. Kristensen Mads B. Amdisen Mie Andersen Torben R. Jensen |
| author_facet | Lasse G. Kristensen Mads B. Amdisen Mie Andersen Torben R. Jensen |
| author_sort | Lasse G. Kristensen |
| collection | DOAJ |
| description | The discovery of new inorganic magnesium electrolytes may act as a foundation for the rational design of novel types of solid-state batteries. Here we investigated a new type of organic-inorganic metal hydride, isopropylamine magnesium borohydride, Mg(BH<sub>4</sub>)<sub>2</sub>∙(CH<sub>3</sub>)<sub>2</sub>CHNH<sub>2</sub>, with hydrophobic domains in the solid state, which appear to promote fast Mg<sup>2+</sup> ionic conductivity. A new synthetic strategy was designed by combination of solvent-based methods and mechanochemistry. The orthorhombic structure of Mg(BH<sub>4</sub>)<sub>2</sub>∙(CH<sub>3</sub>)<sub>2</sub>CHNH<sub>2</sub> was solved <i>ab initio</i> by the Rietveld refinement of synchrotron X-ray powder diffraction data and density functional theory (DFT) structural optimization in space group <i>I</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub> (unit cell, <i>a</i> = 9.8019(1) Å, <i>b</i> = 12.1799(2) Å and <i>c</i> = 17.3386(2) Å). The DFT calculations reveal that the three-dimensional structure may be stabilized by weak dispersive interactions between apolar moieties and that these may be disordered. Nanoparticles and heat treatment (at <i>T</i> > 56 °C) produce a highly conductive composite, σ(Mg<sup>2+</sup>) = 2.86 × 10<sup>−7</sup>, and 2.85 × 10<sup>−5</sup> S cm<sup>−1</sup> at −10 and 40 °C, respectively, with a low activation energy, <i>E</i><sub>a</sub> = 0.65 eV. Nanoparticles stabilize the partially eutectic molten state and prevent recrystallization even at low temperatures and provide a high mechanical stability of the composite. |
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| last_indexed | 2024-03-09T12:16:05Z |
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| spelling | doaj.art-a6b845ce63b5455d93a324e1ea38c9a02023-11-30T22:47:08ZengMDPI AGInorganics2304-67402022-12-011111710.3390/inorganics11010017Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium BorohydrideLasse G. Kristensen0Mads B. Amdisen1Mie Andersen2Torben R. Jensen3Interdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, DenmarkInterdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, DenmarkInterdisciplinary Nanoscience Center (iNANO), Aarhus Institute of Advanced Studies (AIAS), Department of Physics and Astronomy, Center for Interstellar Catalysis, University of Aarhus, DK-8000 Aarhus C, DenmarkInterdisciplinary Nanoscience Center (iNANO), Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C, DenmarkThe discovery of new inorganic magnesium electrolytes may act as a foundation for the rational design of novel types of solid-state batteries. Here we investigated a new type of organic-inorganic metal hydride, isopropylamine magnesium borohydride, Mg(BH<sub>4</sub>)<sub>2</sub>∙(CH<sub>3</sub>)<sub>2</sub>CHNH<sub>2</sub>, with hydrophobic domains in the solid state, which appear to promote fast Mg<sup>2+</sup> ionic conductivity. A new synthetic strategy was designed by combination of solvent-based methods and mechanochemistry. The orthorhombic structure of Mg(BH<sub>4</sub>)<sub>2</sub>∙(CH<sub>3</sub>)<sub>2</sub>CHNH<sub>2</sub> was solved <i>ab initio</i> by the Rietveld refinement of synchrotron X-ray powder diffraction data and density functional theory (DFT) structural optimization in space group <i>I</i>2<sub>1</sub>2<sub>1</sub>2<sub>1</sub> (unit cell, <i>a</i> = 9.8019(1) Å, <i>b</i> = 12.1799(2) Å and <i>c</i> = 17.3386(2) Å). The DFT calculations reveal that the three-dimensional structure may be stabilized by weak dispersive interactions between apolar moieties and that these may be disordered. Nanoparticles and heat treatment (at <i>T</i> > 56 °C) produce a highly conductive composite, σ(Mg<sup>2+</sup>) = 2.86 × 10<sup>−7</sup>, and 2.85 × 10<sup>−5</sup> S cm<sup>−1</sup> at −10 and 40 °C, respectively, with a low activation energy, <i>E</i><sub>a</sub> = 0.65 eV. Nanoparticles stabilize the partially eutectic molten state and prevent recrystallization even at low temperatures and provide a high mechanical stability of the composite.https://www.mdpi.com/2304-6740/11/1/17structureionic conductivitycomplex borohydridemechanochemistry |
| spellingShingle | Lasse G. Kristensen Mads B. Amdisen Mie Andersen Torben R. Jensen Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride Inorganics structure ionic conductivity complex borohydride mechanochemistry |
| title | Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride |
| title_full | Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride |
| title_fullStr | Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride |
| title_full_unstemmed | Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride |
| title_short | Synthesis, Structure and Mg<sup>2+</sup> Ionic Conductivity of Isopropylamine Magnesium Borohydride |
| title_sort | synthesis structure and mg sup 2 sup ionic conductivity of isopropylamine magnesium borohydride |
| topic | structure ionic conductivity complex borohydride mechanochemistry |
| url | https://www.mdpi.com/2304-6740/11/1/17 |
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