Molecular Insights into the Complex Relationship between Capacitance and Pore Morphology in Nanoporous Carbon-based Supercapacitors

Alexander J. Pak, Gyeong S. Hwang

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Electrochemical double layer capacitors, or supercapacitors, are high-power energy storage devices that consist of large surface area electrodes (filled with electrolyte) to accommodate ion packing in accordance with classical electric double layer (EDL) theory. Nanoporous carbons (NPCs) have recently emerged as a class of electrode materials with the potential to dramatically improve the capacitance of these devices by leveraging ion confinement. However, the molecular mechanisms underlying such enhancements are a clear departure from EDL theory and remain an open question. In this paper, we present the concept of ion reorganization kinetics during charge/discharge cycles, especially within highly confining subnanometer pores, which necessarily dictates the capacitance. Our molecular dynamics voltammetric simulations of ionic liquid immersed in NPC electrodes (of varying pore size distributions) demonstrate that the most efficient ion migration, and thereby largest capacitance, is facilitated by nonuniformity of shape (e.g., from cylindrical to slitlike) along nanopore channels. On the basis of this understanding, we propose that a new structural descriptor, coined as the pore shape factor, can provide a new avenue for materials optimization. These findings also present a framework to understand and evaluate ion migration kinetics within charged nanoporous materials.

Original languageEnglish
Pages (from-to)34659-34667
Number of pages9
JournalACS Applied Materials and Interfaces
Issue number50
StatePublished - 21 Dec 2016

Bibliographical note

Publisher Copyright:
© 2016 American Chemical Society.


  • constant potential
  • ion migration kinetics
  • ionic liquid
  • molecular dynamics
  • pore size factor
  • subnanometer confinement


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