Biredox ionic liquids with solid-like redox density in the liquid state for high-energy supercapacitors

Eléonore Mourad, Laura Coustan, Pierre Lannelongue, Dodzi Zigah, Ahmad Mehdi, André Vioux, Stefan A. Freunberger, Frédéric Favier, Olivier Fontaine

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Kinetics of electrochemical reactions are several orders of magnitude slower in solids than in liquids as a result of the much lower ion di_usivity. Yet, the solid state maximizes the density of redox species, which is at least two orders of magnitude lower in liquids because of solubility limitations. With regard to electrochemical energy storage devices, this leads to highenergy batteries with limited power and high-power supercapacitors with a well-known energy deficiency. For such devices the ideal system should endow the liquid state with a density of redox species close to the solid state. Here we report an approach based on biredox ionic liquids to achieve bulk-like redox density at liquid-like fast kinetics. The cation and anion of these biredox ionic liquids bear moieties that undergo very fast reversible redox reactions. As a first demonstration of their potential for high-capacity/high-rate charge storage, we used them in redox supercapacitors. These ionic liquids are able to decouple charge storage from an ion-accessible electrode surface, by storing significant charge in the pores of the electrodes, to minimize self-discharge and leakage current as a result of retaining the redox species in the pores, and to raise working voltage due to their wide electrochemical window.

Original languageEnglish
Pages (from-to)446-454
Number of pages9
JournalNature Materials
Volume16
Issue number4
DOIs
Publication statusPublished - 1 Jan 2017
Externally publishedYes

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ASJC Scopus subject areas

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering

Fields of Expertise

  • Advanced Materials Science

Cite this

Mourad, E., Coustan, L., Lannelongue, P., Zigah, D., Mehdi, A., Vioux, A., ... Fontaine, O. (2017). Biredox ionic liquids with solid-like redox density in the liquid state for high-energy supercapacitors. Nature Materials, 16(4), 446-454. https://doi.org/10.1038/nmat4808, https://doi.org/10.1038/NMAT4808