Title: NMR and Theoretical Study of In-Pore Diffusivity of Ionic Liquid–Solvent Mixtures

Abstract

We report despite having a lower energy density than common batteries, electric double-layer capacitors (EDLCs) offer several advantages for high-power applications, including high power density, quick charge and discharge time, and long cycle life. Room-temperature ionic liquids (RTILs) have been intensely studied as promising electrolytes for applications in ELDCs because of their wide potential window, low volatility, as well as thermal and chemical stability. The main deficiency of neat RTILs in such applications is the sluggish diffusivity, which restricts the EDLCs’ power density. To alleviate the slow diffusivity, RTILs can be used in a mixture with organic solvents. In this study, we applied two-dimensional exchange nuclear magnetic resonance spectroscopy (2D EXSY NMR) and molecular dynamics (MD) simulations to investigate the diffusivity of anions of an RTIL, namely, 1-butyl-3-methyl-imidazolium bis(trifluoromethylsulfonyl)imide (BMIM⁺–TFSI^–), dissolved in five different organic solvents, in the micropores of activated carbon. We determined that the relative concentrations of ions in solutions in the micropores were higher than those in the bulk solutions and were also solvent-dependent. The ion diffusivities in the pores were found to be almost 2 orders of magnitude slower than in the bulk solutions, with methanol showing the largest relative disparity. These results suggested that themore » interactions of solvents with the activated carbon are critical not only to the power density of EDLCs but also to the energy density. The comparisons of ion diffusivities between the experiments and the MD simulations suggest the need to consider also the surface functionalities of activated carbon for the simulation of ion diffusion in the micropores of activated carbon.« less

Authors:

Cui, Jinlei ^[1]; Lin, Xiaobo ^[2]; Zhao, Wei  ^[2];

• Search DOE PAGES for author "Zhao, Wei"
• Search DOE PAGES for ORCID "0000-0003-1497-9312"

Cummings, Peter T. ^[2]; Pruski, Marek  ^[1];

• Search DOE PAGES for author "Pruski, Marek"
• Search DOE PAGES for ORCID "0000-0001-7800-5336"

Kobayashi, Takeshi  ^[1]

• Search DOE PAGES for author "Kobayashi, Takeshi"
• Search DOE PAGES for ORCID "0000-0002-6366-0925"

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+ Show Author Affiliations

1. Ames Lab., Ames, IA (United States)
2. Vanderbilt University, Nashville, TN (United States)

Publication Date:

Wed Jun 22 00:00:00 EDT 2022

Research Org.:

Ames Laboratory (AMES), Ames, IA (United States)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES)

OSTI Identifier:

1874480

Report Number(s):

IS-J-10,836
Journal ID: ISSN 1520-6106

Grant/Contract Number:  

AC02-07CH11358

Resource Type:

Accepted Manuscript

Journal Name:

Journal of Physical Chemistry. B, Condensed Matter, Materials, Surfaces, Interfaces and Biophysical Chemistry

Additional Journal Information:

Journal Volume: 126; Journal Issue: 26; Journal ID: ISSN 1520-6106

Publisher:

American Chemical Society

Country of Publication:

United States

Language:

English

Subject:

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; room temperature ionic liquid; in-pore diffusivity; NMR; molecular dynamics; electric double layer capacitors