Capacitance of thin films containing polymerized ionic liquids

Rajeev Kumar; Jyoti P Mahalik; Kevin S Silmore; Zaneta Wojnarowska; Andrew Erwin; John F Ankner; Alexei P Sokolov; Bobby G Sumpter; Vera Bocharova

doi:10.1126/sciadv.aba7952

Capacitance of thin films containing polymerized ionic liquids

Sci Adv. 2020 Jun 26;6(26):eaba7952. doi: 10.1126/sciadv.aba7952. eCollection 2020 Jun.

Authors

Rajeev Kumar^{1

2

3}, Jyoti P Mahalik^{1

3}, Kevin S Silmore⁴, Zaneta Wojnarowska⁵, Andrew Erwin^{6

7}, John F Ankner⁸, Alexei P Sokolov^{6

9

10}, Bobby G Sumpter^{1

2}, Vera Bocharova⁶

Affiliations

¹ Center for Nanophase Materials Sciences, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
² Computational Sciences and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
³ Department of Mathematics, University of Tennessee, Knoxville, TN 37996, USA.
⁴ Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
⁵ Institute of Physics,University of Silesia,SMCEBI, 75 Pulku Piechoty 1A, 41-500 Chorzow, Poland.
⁶ Chemical Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
⁷ School of Materials Science and Engineering, Georgia Tech, Atlanta, GA 30332, USA.
⁸ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
⁹ Department of Physics and Astronomy, University of Tennessee, Knoxville, TN 37996, USA.
¹⁰ Department of Chemistry, University of Tennessee, Knoxville, TN 37996, USA.

Abstract

Electrode-polymer interfaces dictate many of the properties of thin films such as capacitance, the electric field experienced by polymers, and charge transport. However, structure and dynamics of charged polymers near electrodes remain poorly understood, especially in the high concentration limit representative of the melts. To develop an understanding of electric field-induced transformations of electrode-polymer interfaces, we have studied electrified interfaces of an imidazolium-based polymerized ionic liquid (PolyIL) using combinations of broadband dielectric spectroscopy, specular neutron reflectivity, and simulations based on the Rayleigh's dissipation function formalism. Overall, we obtained the camel-shaped dependence of the capacitance on applied voltage, which originated from the responses of an adsorbed polymer layer to applied voltages. This work provides additional insights related to the effects of molecular weight in affecting structure and properties of electrode-polymer interfaces, which are essential for designing next-generation energy storage and harvesting devices.

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