Ionic relaxation in ‘Solvent-in-Salt’ electrolytes

 · Invited

Abstract

Solvent-in-salt (SIS) systems are one of the promising materials for the next generation of energy storage applications. The ion dynamic is significantly different in these systems from that of ionic liquids and diluted salt solutions. In this study we analyze ion dynamics of two salts Li-TFSI and Li-FSI in highly concentrated aqueous and acetonitrile solutions. We present the comprehensive study of these systems using the PFG-NMR, FTIR, QENS and MD simulations, with major focus on Broadband dielectric spectroscopy (BDS) covering the range up to 50 GHz. The estimated from the BDS data the conductivity relaxation time defines the characteristic crossover time between individual jumps of charge carriers and normal diffusion regime resulting in dc-conductivity. Analysis revealed that normal charge diffusion sets in on the distance ~1-2 Å, comparable to the average distance between the ions. Based on the idea of momentum conservation the distinct ion correlations were estimated and analyzed, and the results suggest that dependence of anion-cation correlations on solvent content. Presented analysis demonstrate that FSI based system shows faster dynamics with shorter onset of normal diffusion regime than TFSI based system resulting in higher conductivity.

*This work was supported by the Fluid Interface Reactions, Structures and Transport (FIRST) Center, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences. Research at the BASIS of the ORNL’s Spallation Neutron Source was sponsored by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. Access to the HFBS was provided by the Center for High Resolution Neutron Scattering, a partnership between the NIST and the NSF under agreement no. DMR-1508249.

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Presenters

  • Ivan Popov

    • Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Laboratory

Authors

  • Ivan Popov

    • Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Laboratory

  • Robert Sacci

    • Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Lab

  • Nicolette Sanders

    • Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA

  • Ray Matsumoto

    • Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA
    • Vanderbilt University

  • Matthew Thompson

    • Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA

  • Naresh Osti

    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

  • Takeshi Kobayashi

    • U.S. DOE Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA

  • Madhusudan Tyagi

    • National Institute of Standards and Technology
    • NIST Center for Neutron Research, 444 National Institute of Standards and Technology, Gaithersburg, 445 Maryland 20899, United States
    • National Institute of Science and Technology
    • NIST Center for Neutron Research | NIST
    • NIST

  • Eugene Mamontov

    • Oak Ridge National Lab
    • Neutron Scattering Division, Neutron Sciences Directorate, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Laboratory
    • Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN, USA

  • Marek Pruski

    • U.S. DOE Ames Laboratory, Iowa State University, Ames, Iowa 50011, USA

  • Peter Thomas Cummings

    • Department of Chemical and Biomolecular Engineering, Vanderbilt University, Nashville, Tennessee 37235, USA
    • Vanderbilt University

  • Alexei Sokolov

    • Oak Ridge National Lab
    • Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
    • Oak Ridge National Laboratory
    • University of Tennessee
    • Department of Chemistry, University of Tennessee, Knoxville, USA
    • Department of Chemistry, university of Tennessee