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Séminaire Chimie ED459

Les liquides ioniques birédox : une nouvelle opportunité pour les supercondensateurs

Dr. Olivier Fontaine, MCF (équipe AIME Agrégats Interfaces et Matériaux pour l’Énergie, ICGM Institut Charles Gerhardt UMR 5253, CNRS, ENSCM, Université de Montpellier)

publié le , mis à jour le

Le Jeudi 20 Octobre 2016 à 13h45
UM FdS, Salle de Cours SC-16.01

(la conférence sera présentée en français)

Biredox ionic liquids : new opportunity for supercapacitors

Kinetics of electrochemical reactions are several orders of magnitude slower in solids than in liquids as a result of the much lower ion diffusivity. On the other hand, the solid state maximizes the density of redox species, which is at least two orders of magnitude lower in molecular solutions because of solubility limitations. 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 (ILs) to achieve towards bulk like redox density at liquid like fast kinetics (Fig. 1a). The cation and anion of these biredox ILs bear moieties that undergo very fast reversible redox reactions.[1] As a first demonstration of their potential for high-capacity / high-rate charge storage, we used them in supercapacitors with specific capacitance of 200 F/g and 370 F/g respectively for 0.5 M of biredox ILs in BMimTFSI and for pure biredox ILs at 60°C (Fig. 1b).[2] This new class of functional materials opens up a wide new field in redox materials and their applications in energy storage and beyond.

Figure 1. Charge storage in EDLC with the biredox IL enhanced supercapacitor :
a. Structure of the biredox IL comprising a perfluorosulfonate anion bearing anthraquinone (AQ–PFS) and a methyl imidazolium cation bearing TEMPO (MIm+–TEMPO)
b. Cyclic voltammetry at 5 mV.s–1 with pure biredox IL at 60°C (red, solid line) and pure BMImTFSI (blue, dashed line) made with PICA activated carbon as electrodes.

References

1. E. Mourad, L. Coustan, S.A. Freunberger, A. Mehdi, A. Vioux, F. Favier, O. Fontaine, “Biredox ionic liquids : electrochemical investigation and impact of ion size on electron transfer”. Electrochimica Acta 2016, 206, 513–523. DOI : 10.1016/j.electacta.2016.02.211
2. E. Mourad, L. Coustan, S.A. Freunberger, A. Mehdi, A. Vioux, F. Favier, O. Fontaine, “Biredox ionic liquids with solid-like redox density in the liquid state for high-energy supercapacitors”. Nature Materials 2016, in press. DOI : 10.1038/nmat4808

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