Lithium-doped rotator phases as ion conducting electrolytes

• Applicant: Professor Dr. Roland Böhmer
• Subject Area: Physical Chemistry of Solids and Surfaces, Material Characterisation ; Experimental Condensed Matter Physics
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 429918288

• Final Report Year: 2024

Final Report Abstract

Modern battery electrolytes require materials that display high electrical conductivity, paired with a good mechanical strength. With the goal to fulfill these seemingly opposing conditions as well as possible, in this project rotator phases, where rapidly reorienting polar molecules form a crystal lattice, were doped with suitable lithium salts in different concentrations. Nuclear magnetic proton, deuteron, and lithium resonance experiments as well as dielectric spectroscopy and rheology were the main tools to examine how the rotational dynamics of the matrix molecules couple to the application-relevant translational mobility of the lithium ions. With this combination of methods, allowing for a selective access to the different degrees of freedom in ionic conductors, for the example of a 5% lithium-doped succinonitrileglutaronitrile mixture it was possible to obtain evidence in favor of the so-called paddle-wheel mechanism. Exploring also rather highly lithium doped nitrile matrices, we were additionally able to demonstrate a coupling of charge transport and mechanical strength in a large temperature window. In order to enable a comparison with the particular dynamical behavior of the nitriles, we investigated doped cycloalcohols, another class of plastic crystals that display a similarly interesting coupling of molecular and ionic motions.

Publications

• Deuteron nuclear magnetic resonance and dielectric studies of molecular reorientation and charge transport in succinonitrile-glutaronitrile plastic crystals. Journal of Non-Crystalline Solids: X, 14, 100097.
  Lansab, Sofiane; Münzner, Philipp; Zimmermann, Herbert & Böhmer, Roland
  
• Paddle-wheel mechanism in doped succinonitrile–glutaronitrile plastic electrolyte: a joint magnetic resonance, dielectric, and viscosimetry study of Li ion translational and molecular reorientational dynamics. Physical Chemistry Chemical Physics, 25(13), 9382-9393.
  Lansab, S.; Grabe, B. & Böhmer, R.
  
• Shear rheology senses the electrical room-temperature conductivity optimum in highly Li doped dinitrile electrolytes. The Journal of Chemical Physics, 160(8).
  Lansab, Sofiane; Schwan, Tobias; Moch, Kevin & Böhmer, Roland