Yan Yigang, Dononelli Wilke, Jørgensen Mathias, Grinderslev Jakob B, Lee Young-Su, Cho Young Whan, Černý Radovan, Hammer Bjørk, Jensen Torben R
Interdisciplinary Nanoscience Center (iNANO) and Department of Chemistry, Aarhus University, Langelandsgade 140, 8000 Aarhus C, Denmark.
Phys Chem Chem Phys. 2020 May 7;22(17):9204-9209. doi: 10.1039/d0cp00158a. Epub 2020 Mar 31.
Light weight and cheap electrolytes with fast multi-valent ion conductivity can pave the way for future high-energy density solid-state batteries, beyond the lithium-ion battery. Here we present the mechanism of Mg-ion conductivity of monoammine magnesium borohydride, Mg(BH)·NH. Density functional theory calculations (DFT) reveal that the neutral molecule (NH) in Mg(BH)·NH is exchanged between the lattice and interstitial Mg facilitated by a highly flexible structure, mainly owing to a network of di-hydrogen bonds, N-HH-B and the versatile coordination of the BH ligand. DFT shows that di-hydrogen bonds in inorganic matter and hydrogen bonds in bio-materials have similar bond strengths and bond lengths. As a result of the high structural flexibiliy, the Mg-ion conductivity is dramatically improved at moderate temperature, e.g. σ(Mg) = 3.3 × 10 S cm at T = 80 °C for Mg(BH)·NH, which is approximately 8 orders of magnitude higher than that of Mg(BH). Our results may inspire a new approach for the design and discovery of unprecedented multivalent ion conductors.
重量轻且价格低廉、具有快速多价离子传导性的电解质可为超越锂离子电池的未来高能量密度固态电池铺平道路。在此，我们展示了单氨硼氢化镁Mg(BH₄)₃·NH₃的镁离子传导机制。密度泛函理论计算（DFT）表明，Mg(BH₄)₃·NH₃中的中性分子（NH₃）在高度灵活的结构促进下，在晶格和间隙镁之间交换，这主要归因于双氢键网络N-H···H-B以及BH₄配体的多功能配位。DFT表明无机物中的双氢键和生物材料中的氢键具有相似的键强度和键长。由于高度的结构灵活性，在中等温度下镁离子传导率显著提高，例如对于Mg(BH₄)₃·NH₃，在T = 80 °C时σ(Mg²⁺) = 3.3 × 10⁻⁵ S cm⁻¹，这比Mg(BH₄)₂的传导率高出约8个数量级。我们的结果可能会激发一种设计和发现前所未有的多价离子导体的新方法。
