Mixtures of Lithium Salts and Ionic Liquids at Defected Graphene Walls



In order to investigate the effect of defects on the structure of an electrode on the electric double layer of ionic-liquid-based electrolytes, we perform classical molecular dynamic simulations on mixtures of 1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM][BF4]) and lithium tetrafluoroborate (LiBF4) near charged graphene electrodes with different percentages of single defect vacancies, assuming planarity of the defected graphene, as follows from our density-functional theory calculations. Defects on the electrode's surface modify the surface charge density at the innermost layer of the electrochemical interface, which allows studying the structure of the electric double layer at a constant density of ions without changing either the voltage or the electrolyte composition. Indeed, we report that the presence of defects on the graphene electrodes can induce structural transitions in the innermost layer of the electric double layer. This result is supported by a thorough analysis of the structural properties of the layer and its energy landscape, particularly showing that there is a direct correlation between this defect-induced layer structure and the adsorption of the salt cations at the electrode, which is of utmost importance for the usage of these novel electrolytic mixtures in actual electrochemical devices. © 2019 Elsevier B.V.


Supplementary material is available at: https://ars.els-cdn.com/content/image/1-s2.0-S0167732219310165-mmc1.pdf


Ionic solutions, Boron compounds, Density functionals, Electrolytes, Electrolytes--Analysis, Fluorine compounds, Graphene, Lithium compounds, Mixtures, Molecular dynamics, 1-butyl-3-methylimidazolium tetrafluoroborate, Molecular dynamics, Lithium tetrafluoroborate


Spanish Ministry of Economy and Competitiveness (Grants MAT2014-57943-C3-1-P, MAT2014-57943-C3-3-P, MAT2017-89239-C2-1-P, MAT2017-89239-C2-2-P); Xunta de Galicia (AGRUP2015/11, ED431D 2017/06, ED431E 2018/08 and GRC ED431C 2016/001)


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