Mechanism of Lithium Cation Hopping between Tetragonal Thiophene Cages

Abstract

We report on the atomistic mechanism of elementary hopping processes of Li + ions in liquid thiophene obtained from abinitio molecular dynamics simulations. We observe the formation of cage structures which solvate the cation. Besides the actual molecular solvation structure, we provide an analysis of the pathway and timescale of basic Li + diffusion steps in terms of coordination by sulfur atoms. We compare our results to the situation in a thiophene derivative, namely 3,4-ethylenedioxythiophene (EDOT). The calculations reveal that in both thiophene and EDOT liquids, a tetrahedral structure is formed around the Li + ion. While in the case of the former, the Li cation is coordinated by four sulfur atoms, in the latter case it is surrounded by four oxygens. The tetrahedrons act as cages, which accommodate the cation for a considerable duration (of the order of 100 ps). The elementary diffusion step occurs through a "permeable edge" of the tetrahedron formed by two sulfur (or oxygen) atoms at a characteristic distance. This finding indicates that Li + conduction in thiophene derivatives can be improved by rationally designing the compound in such a way that maximizes the occurrence of sulfur atoms at that particular distance from each other.[a] Dr.

Secondary Structure Formation in Hybrid Synthetic/Peptide Polymers: Insights from Molecular Dynamics Simulations

“…[ 11 ] Beforehand, a preliminary study dealt with the understanding of lithium diffusion in amorphous thiophene. [ 12 ] This research line is presently intensified and will give rise to novel projects in the context of renewable energies.…”