Trends and Perspectives of Neutron Spectroscopy

IN6-SHARP: towards a new cold neutron spectrometer at ILL. Illustration of the potentialities of QENS to probe the dynamics of Ionic liquids in bulk and under 1D nanometric confinement.

by Dr Jean-Marc Zanotti (LLB)

→ Europe/Berlin
JCNS seminar room

JCNS seminar room
Description

Q. Berrod1, F. Ferdeghini1, P. Judeinstein1, J. Dijon2, J.-M. Zanotti1
1 Laboratoire Léon Brillouin (CEA-CNRS), Université Paris-Saclay, 91191 Gif-sur-Yvette, France

2 CEA/LITEN/DTNM, 38054 Grenoble, France

Following the agreement to strengthen the Franco-Swedish cooperation in the field of neutron scattering, the Laboratoire Léon Brillouin (LLB) is involved in the construction of an inelastic time-of-flight spectrometer. After the announcement of the Orphée reactor shutdown in 2020, the project originally planned at Saclay has been be transferred to the Laue Langevin Institute (ILL). This renaissance takes the form of an A type CRG contract concluded on September 29th 2017 between the DRF of the CEA, the INP of the CNRS, and the ILL. This new project SHARP (Spectromètre Hybride Alpes Région Parisienne) consists of a complete rebuilding of the IN6 secondary spectrometer: sample environment, time-of-flight chamber and detection. This seminar will start by an update on the project.

We will then illustrate the potentialities of Quasi-Elastic Neutron Scattering (QENS) in the study of Ionic liquids (ILs). ILs are pure solutions of charged organic molecules with no solvent. These molecular electrolytes show a property original for a pure liquid: they self-organize in nanometric fluctuating aggregates1. When probed at the macroscopic scale, ILs behave as highly dissociated (i.e. strong) electrolytes2 while, at the molecular scale, they show clear characteristics of weak ionic solutions3. In this talk, we report a multi-scale analysis that sheds new light on these apparently at odd behaviors4,5.

Due to their remarkable chemical and electrochemical stability, ILs have been identified as prime candidates electrolytes for the development of new safe and sustainable energy storage systems. We show6 a noticeable enhancement (by a factor 3) of the transport properties of a neat IL under CNT (Carbon NanoTube) confinement in a 1D situation. Such CNT membranes are a possible route to boost the transport properties and hence the specific power of lithium batteries7. We then address the conductivity of electrolytes directly relevant to the field of electrochemical storage systems: ILs charged with lithium salts. We show that these electrolytes confined in 1D CNT membranes show a drastic and unprecedented increase in ionic conductivity. Compared to the bulk analogues, we indeed report conductivity gains by a factor up to 50 upon macroscopic 1D CNT confinement.

We think that the disruptive concept of a 1D CNT based separator laying at the cross-road of basic science is probably of interest for future technological outcomes.

  1. Hayes, R., Warr, G. G. & Atkin, R. Structure and Nanostructure in Ionic Liquids. Chem. Rev. 115, 6357–6426 (2015).

  2. Lee, A. A., Vella, D., Perkin, S. & Goriely, A. Are Room-Temperature Ionic Liquids Dilute Electrolytes? J. Phys. Chem. Lett. 6, 159–163 (2015).

  3. Gebbie, M. A., Dobbs, H. A., Valtiner, M. & Israelachvili, J. N. Long-range electrostatic screening in ionic liquids. Proc. Natl. Acad. Sci. 112, 7432–7437 (2015).

  4. Ferdeghini, F. et al. Nanostructuration of ionic liquids: impact on the cation mobility. A multi-scale study. Nanoscale 9, 1901–1908 (2017).

  5. Quentin Berrod et al. Ionic Liquids: evidence of the viscosity scale-dependence. Sci. Rep. 7, (2017).

  6. Berrod, Q. et al. Enhanced ionic liquid mobility induced by confinement in 1D CNT membranes. Nanoscale 8, 7845–7848 (2016).

  7. Berrod, Q., Ferdeghini, F., Judeinstein, P. & Zanotti, J.-M. Nanocomposite membranes for electrochemical devices. Patent WO 2016151142 A1. (2016).