The mechanism of Mg2+ conduction in ammine magnesium borohydride promoted by a neutral molecule. Issue 17 (31st March 2020)

• Record Type: Journal Article
• Authors: Yan, Yigang; Dononelli, Wilke; Jørgensen, Mathias; Grinderslev, Jakob B.; Lee, Young-Su; Cho, Young Whan; Černý, Radovan; Hammer, Bjørk; Jensen, Torben R.
• Is Part Of: Physical chemistry chemical physics. Volume 22:Issue 17(2020)
• Page Start: 9204
• Page End: 9209
• Publication Date: 2020-03-31
• Subjects: Chemistry, Physical and theoretical -- Periodicals; 541.3
• DOI: 10.1039/d0cp00158a
• Languages: English
• ISSNs: 1463-9076

Abstract

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. 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 Mg 2+ facilitated by a highly flexible structure, mainly owing to a network of di-hydrogen bonds, N–H δ + ⋯ − δ H–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 (Mg 2+ ) = 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.