Issue 67, 2020

The effect of diameter size of single-walled carbon nanotubes on their high-temperature energy storage behaviour in ionic liquid-based electric double-layer capacitors

Abstract

We investigated the effect of the diameter size of single-walled carbon nanotubes (SWCNTs), on their high-temperature energy storage behavior in an electric double layer capacitor (EDLC) using the ionic liquid triethyl(2-methoxyethyl) phosphonium bis(trifluoromethylsulfonyl)imide (P222(2O1)-TFSI). We used four SWCNT samples with diameter sizes ranging from 0.8 to 5 nm, and evaluated their electrochemical charge storage behavior through galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS). We found that for the SWCNTs with small average diameter of 1 nm, the value of the electrode capacitance measured at a current density of 5 mA g−1 increased from 15.8 at room temperature to 27.5 F g−1 at 150 °C, and the value measured at a current density of 80 mA g−1 increased from 14.0 at room temperature to 22.1 F g−1 at 150 °C. The larger diameter samples on the other hand did not show any significant change in their capacitance with temperature. We calculated the size of the interstitial tube spaces from the Raman spectra of the samples, and used density functional theory (DFT) calculations to estimate the sizes of the cation and anion of the electrolyte. The obtained results suggest that the temperature-induced changes in the electrolyte properties improved the ion accessibility into the otherwise constrained space inside the small diameter SWCNTs, while the spaces inside the larger SWCNTs already provided easily accessible storage sites hence good performance at room temperature, making the increase in temperature of little to no effect on the charge storage performance in such SWCNTs.

Graphical abstract: The effect of diameter size of single-walled carbon nanotubes on their high-temperature energy storage behaviour in ionic liquid-based electric double-layer capacitors

Supplementary files

Article information

Article type
Paper
Submitted
08 Oct 2020
Accepted
22 Oct 2020
First published
11 Nov 2020
This article is Open Access
Creative Commons BY license

RSC Adv., 2020,10, 41209-41216

The effect of diameter size of single-walled carbon nanotubes on their high-temperature energy storage behaviour in ionic liquid-based electric double-layer capacitors

A. Al-zubaidi, N. Asai, Y. Ishii and S. Kawasaki, RSC Adv., 2020, 10, 41209 DOI: 10.1039/D0RA08579K

This article is licensed under a Creative Commons Attribution 3.0 Unported Licence. You can use material from this article in other publications without requesting further permissions from the RSC, provided that the correct acknowledgement is given.

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