Understanding and controlling the rest potential of carbon nanotube-based supercapacitors for energy density enhancement

Young Eun Yoo, Jinwoo Park, Woong Kim

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

We present a novel method for enhancing the energy density of an electrical double layer capacitor (EDLC). Surface modification of single-walled carbon nanotube (SWNT) electrodes significantly affects the rest potential (E0) of EDLCs; acid treatment and polyethyleneimine (PEI) coating of SWNTs shift E0 toward more positive and more negative values, respectively. Adjusting E0 towards the center of the electrolyte stability window can increase the cell voltage and hence the energy density. PEI coating on SWNTs increases the cell voltage from 0.8 V to 1.7 V in tetrabutylammonium perchlorate (TBAP)/tetrahydrofuran (THF) electrolyte, and from 2.5 V to 3.1 V in tetraethylammonium tetrafluoroborate (TEABF4)/3-cyanopropionic acid methyl ester (CPAME), respectively. Moreover, PEI-SWNT EDLCs exhibit excellent cycling stability (92% of capacitance retention over 10000 cycles). We attribute the shift in E0 to a change in the Fermi level of SWNTs owing to the surface charge modification. Injection of electrical charge into PEI-SWNTs consistently yielded similar trends and thus validated our hypothesis. Our results may help to push various electrolytes that have been overlooked so far to new frontiers for obtaining high energy-density supercapacitors.

Original languageEnglish
Pages (from-to)765-771
Number of pages7
JournalApplied Surface Science
Volume433
DOIs
Publication statusPublished - 2018 Mar 1

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Keywords

  • Carbon nanotube
  • Rest potential
  • Stability window
  • Supercapacitor
  • Surface modification

ASJC Scopus subject areas

  • Surfaces, Coatings and Films

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