Utilizing ionic liquids for controlled N-doping in hard-templated, mesoporous carbon electrodes for high-performance electrochemical double-layer capacitors

Benjamin E. Wilson, Siyao He, Keegan Buffington, Stephen Rudisill, William H. Smyrl, Andreas Stein

Research output: Contribution to journalArticlepeer-review

32 Scopus citations

Abstract

The specific energy of electrochemical double-layer capacitors (EDLCs) can be increased by design of the pore architecture to provide large interfaces between electrodes and electrolyte and efficient access to these surfaces. Colloidal-crystal templated carbon electrodes with interconnected, uniform mesopores have demonstrated high capacitances at fast charge/discharge rates in EDLCs used with ionic liquid electrolytes. Here we aim to enhance capacitive performance further through nitrogen doping, by combining a phenol-formaldehyde precursor with the ionic liquid (IL) 1-ethyl-3-methylimidazolium dicyanoamide (EMI-DCA) as the nitrogen source. The IL content in this precursor affects the resistance, structural integrity, and specific capacitance of the porous electrodes. With an IL content up to 50 wt%, the electrode resistance is reduced while the bicontinuous mesoporous structure of the resulting carbon is preserved. The specific capacitance of an electrode prepared with 50% IL in the precursor increases over 40% at 10 A g-1 compared to mesoporous carbons prepared using only the phenol-formaldehyde resol. With an ionic liquid electrolyte, the maximum specific capacitance is 237 F g-1 at 0.1 A g-1, and a specific capacitance of at least 195 F g-1 is maintained after 1000 cycles at 1 A g-1. A higher IL content in the precursor results in reduced structural order and capacitive performance.

Original languageEnglish (US)
Pages (from-to)193-202
Number of pages10
JournalJournal of Power Sources
Volume298
DOIs
StatePublished - Dec 1 2015

Keywords

  • Colloidal templating
  • Electrochemical double-layer capacitor
  • Ionic liquid
  • Mesoporous carbon
  • Nitrogen-doped carbon

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