Scientists at NSU and the Institute of Solid State Chemistry and Mechanochemistry Siberian Branch of the Russian Academy of Sciences (SSCMI) have moved closer to an understanding of the ion transfer process. Their research results were published in the “Structural Chemistry” journal. Everyone knows liquid electrolytes, they are the ones that conduct electric current in ordinary batteries. However, solid electrolytes exist with them and the scientific community is still questioning how ions are transferred in them. Some organic salts of substituted ammonia have rather high ionic conductivity in a solid state.
With the help of single crystal and powder X-ray diffraction, IR spectroscopy, and computational methods it was possible to demonstrate that the structure of the tetrabutylammonium cation in organic salts can easily undergo conformational changes. The authors did this by analyzing an array of crystallographic data on compounds containing tetra-n-butylammonium cations.
Denis Rychkov, Head of the NSU Department of Natural Sciences Laboratory of Physicochemical Fundamentals of Pharmaceutical Materials and Deputy Director for Science at ISSCM SB RAS, talked about their research,
Our initial assumption and research results suggests that tetra-n-butylammonium cations have "tails" that form the salt’s crystal framework. They have the proper equilibrium state, but it obviously does not match the conduction. An analysis of the tetra-n-butylammonium cations geometry in these structures demonstrated that the “tails” rotate in such a way that their structure turns from a tetrahedron into almost a square.
The researchers suggest that the conductivity of solid electrolytes based on quaternary ammonium salts is due to anions that are smaller and fill the free space between large tailed cations.