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Accelerating charging dynamics in subnanometre pores

Nature Materials volume 13, pages 387–393 (2014)Cite this article

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An Erratum to this article was published on 22 April 2014

This article has been updated

Abstract

Supercapacitors have exceptional power density and cyclability but smaller energy density than batteries. Their energy density can be increased using ionic liquids and electrodes with subnanometre pores, but this tends to reduce their power density and compromise the key advantage of supercapacitors. To help address this issue through material optimization, here we unravel the mechanisms of charging subnanometre pores with ionic liquids using molecular dynamics simulations, navigated by a phenomenological model. We show that charging of ionophilic pores is a diffusive process, often accompanied by overfilling followed by de-filling. In sharp contrast to conventional expectations, charging is fast because ion diffusion during charging can be an order of magnitude faster than in the bulk, and charging itself is accelerated by the onset of collective modes. Further acceleration can be achieved using ionophobic pores by eliminating overfilling/de-filling and thus leading to charging behaviour qualitatively different from that in conventional, ionophilic pores.

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Figure 1: Charging of narrow electrode pores with room-temperature ionic liquids.
Figure 2: Charging of nanopores predicted by the mean field model.
Figure 3: Ion self-diffusion during charging of ionophilic pores.
Figure 4: Charging of ionophilic pores obtained from molecular dynamics simulations.
Figure 5: Self-diffusion and charging in ionophobic pores.

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  • 25 March 2014

    In the version of this Article originally published, the e-mail address of Svyatoslav Kondrat was misspelt; it should have read ‘s.kondrat@fz-juelich.de’. This error has now been corrected in the online versions of the Article.

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Acknowledgements

We thank the Clemson-CCIT office and E. Duffy for providing computer facilities. R.Q. acknowledges the support of the NSF (CBET-1264578). S.K. and A.K. were supported by the Engineering and Physical Science Research Council via Grant EP/H004319/1. We are grateful to Y. Gogotsi, P. Simon, C. Pérez, J. Griffin, G. Oshanin and F. Stoeckli for fruitful discussions, and X. Jiang for technical assistance.

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Authors and Affiliations

  1. Forschungszentrum Jülich, IBG-1: Biotechnology, 52425 Jülich, Germany

    Svyatoslav Kondrat

  2. Department of Chemistry, Faculty of Natural Sciences, Imperial College London, SW7 2AZ, UK

    Svyatoslav Kondrat & Alexei A. Kornyshev

  3. Department of Mechanical Engineering, Clemson University, Clemson, South Carolina 29634-0921, USA

    Peng Wu & Rui Qiao

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  1. Svyatoslav Kondrat
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Contributions

A.A.K., R.Q. and S.K. designed the research. P.W. performed MD simulations and S.K. performed MFT calculations. The results were analysed jointly by R.Q., S.K., A.A.K. and P.W., and all participated in writing the paper.

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Correspondence to Svyatoslav Kondrat, Rui Qiao or Alexei A. Kornyshev.

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Kondrat, S., Wu, P., Qiao, R. et al. Accelerating charging dynamics in subnanometre pores. Nature Mater 13, 387–393 (2014). https://doi.org/10.1038/nmat3916

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