Dynamics and Structural Evolution in a Solid-state Mg-ion Conductor

Dr. Michael Heere
IAM-ESS, Karlsruhe Institute of Technology (KIT), Eggenstein, Germany.

By Dr. Michael Heere, IAM-ESS, Karlsruhe Institute of Technology (KIT), Eggenstein, Germany.

Neutrons are a unique probe for non-destructive structural studies of energy materials, especially for future investigation and development of highly conductive solid-state Mg-based electrolytes; neutrons are one of the main requirements for successful post-Li battery research. Recently, a new compound synthesized from γ-Mg(BH4)2 and ethylenediamine (C2H8N2, abbreviation “en”) was reported by Roedern et al. to have an exceptionally high magnesium ion conductivity of up to 6.10-5 S/cm at 70 °C in the solid-state [1]. In our work, the structure of this new compound has been solved and shows a different ratio of the precursors, γ-Mg(BH4)2 : [Mg(en)3(BH4)2], while the initially reported one was 2:1. A new ratio of precursors will increase the ionic conductivity, simply because there is less unreacted γ-Mg(BH4)2. High-resolution neutron powder diffraction data was previously collected at the NOVA beamline at J-Parc Spallation Source, Japan, and shows a very good correlation with the proposed model. Conductivity measurements will be presented as well as quasi-elastic neutron scattering (QENS) experiments.
MH acknowledges the project “Energy Research with Neutrons (ErwiN)” [2], which is funded by the German Federal Ministry of Education and Research (BMBF).
Michael Heere1,2, Volodia Gounaris3, Xiao Li3, Jian Wang3, and Yaroslav Filinchuk3
(1) Institute for Applied Materials—Energy Storage Systems (IAM-ESS), Karlsruhe Institute of Technology (KIT), 76344 Eggenstein, Germany.
(2) Heinz Maier-Leibnitz Zentrum (MLZ), Technische Universität München, Lichtenbergstr. 1 85748 Garching b. München, Germany.
(3) Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium.

[1] Roedern, E., R.-S. Kühnel, A. Remhof, and C. Battaglia, Magnesium Ethylenediamine Borohydride as Solid-State Electrolyte for Magnesium Batteries. Scientific reports, 2017. 7: p. 46189.
[2] Heere, M., M.J. Mühlbauer, A. Schökel, M. Knapp, H. Ehrenberg, and A. Senyshyn, Energy research with neutrons (ErwiN) and installation of a fast neutron powder diffraction option at the MLZ, Germany. Journal of Applied Crystallography, 2018. 51(3).


Michael’s PhD was based within the Marie Curie ITN “ECOSTORE” at the Institute for Energy Technology (IFE) in Kjeller, Norway (Supervisor Prof. B.C. Hauback). Energy materials for applications such as hydrogen storage and batteries as well as new developments in sample environments are of his main interests, while being responsible for building up a new fast powder diffractometer ‘ErwiN’ at the research neutron source in Munich, Germany.