Influence of Solvent on Ion Aggregation and Transport in PY15TFSI Ionic Liquid鈥揂protic Solvent Mixtures

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• 作者：Oleg Borodin ; Wesley A. Henderson ; Eric T. Fox ; Marc Berman ; Mallory Gobet ; Steve Greenbaum
• 刊名：Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：September 12, 2013
• 年：2013
• 卷：117
• 期：36
• 页码：10581-10588
• 全文大小：466K
• 年卷期：v.117,no.36(September 12, 2013)
• ISSN：1520-5207

文摘

Molecular dynamics (MD) simulations using a many-body polarizable APPLE&P force field have been performed on mixtures of the N-methyl-N-pentylpyrrolidinium bis(trifluoromethanesulfonyl)imide (PY₁₅TFSI) ionic liquid (IL) with three molecular solvents: propylene carbonate (PC), dimethyl carbonate (DMC), and acetonitrile (AN). The MD simulations predict density, viscosity, and ionic conductivity values that agree well with the experimental results. In the solvent-rich regime, the ionic conductivity of the PY₁₅TFSI鈥揂N mixtures was found to be significantly higher than the conductivity of the corresponding 鈭扨C and 鈭扗MC mixtures, despite the similar viscosity values obtained from both the MD simulations and experiments for the 鈭扗MC and 鈭扐N mixtures. The significantly lower conductivity of the PY₁₅TFSI鈥揇MC mixtures, as compared to those for PY₁₅TFSI鈥揂N, in the solvent-rich regime was attributed to the more extensive ion aggregation observed for the 鈭扗MC mixtures. The PY₁₅TFSI鈥揇MC mixtures present an interesting case where the addition of the organic solvent to the IL results in an increase in the cation鈥揳nion correlations, in contrast to what is found for the mixtures with PC and AN, where ion motion became increasingly uncorrelated with addition of solvent. A combination of pfg-NMR and conductivity measurements confirmed the MD simulation predictions. Further insight into the molecular interactions and properties was also obtained using the MD simulations by examining the solvent distribution in the IL鈥搒olvent mixtures and the mixture excess properties.