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Mechanism of Lithium Cation Hopping between Tetragonal Thiophene Cages
Author(s) -
PartoviAzar Pouya,
Sebastiani Daniel
Publication year - 2019
Publication title -
batteries and supercaps
Language(s) - English
Resource type - Journals
ISSN - 2566-6223
DOI - 10.1002/batt.201900043
Subject(s) - thiophene , lithium (medication) , tetrahedron , tetragonal crystal system , chemistry , ion , crystallography , solvation , sulfur , computational chemistry , diffusion , chemical physics , delocalized electron , ab initio , ab initio quantum chemistry methods , inorganic chemistry , molecule , crystal structure , thermodynamics , organic chemistry , physics , medicine , endocrinology
We report on the atomistic mechanism of elementary hopping processes of Li + ions in liquid thiophene obtained from ab‐initio 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.