Issue 17, 2020

The mechanism of Mg2+ conduction in ammine magnesium borohydride promoted by a neutral molecule

Abstract

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(BH4)2·NH3. Density functional theory calculations (DFT) reveal that the neutral molecule (NH3) in Mg(BH4)2·NH3 is exchanged between the lattice and interstitial Mg2+ facilitated by a highly flexible structure, mainly owing to a network of di-hydrogen bonds, N–Hδ+δH–B and the versatile coordination of the BH4 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(Mg2+) = 3.3 × 10−4 S cm−1 at T = 80 °C for Mg(BH4)2·NH3, which is approximately 8 orders of magnitude higher than that of Mg(BH4)2. Our results may inspire a new approach for the design and discovery of unprecedented multivalent ion conductors.

Graphical abstract: The mechanism of Mg2+ conduction in ammine magnesium borohydride promoted by a neutral molecule

Supplementary files

Article information

Article type
Paper
Submitted
10 Jan 2020
Accepted
23 Mar 2020
First published
23 Mar 2020

Phys. Chem. Chem. Phys., 2020,22, 9204-9209

The mechanism of Mg2+ conduction in ammine magnesium borohydride promoted by a neutral molecule

Y. Yan, W. Dononelli, M. Jørgensen, J. B. Grinderslev, Y. Lee, Y. W. Cho, R. Černý, B. Hammer and T. R. Jensen, Phys. Chem. Chem. Phys., 2020, 22, 9204 DOI: 10.1039/D0CP00158A

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