New molecules

The functionalization of carbon-based materials by different molecules is also a way to retain the intrinsic advantages of a carbon-based electrode (long lifetime, high power density), while providing it with a new property (increased ion conduction , Hydrophilicity for the aqueous medium) or a significant increase in capacity. This last strategy is the result of a long-standing collaboration with the laboratory of Professor Daniel Bélanger at the Université du Québec à Montréal. It is supported by a thesis of the regional project PERLE 2, and more recently with the project ANR ICROSS (PROGELEC 2013).

Theme: chemical modification of carbons as electrode materials for supercapacitors in aqueous media.

This doctoral work is carried out in co-supervision between the IMN and the University of Quebec in Montreal and consists in developing new supercapacitors operating in aqueous electrolyte. In order to increase the amount of energy stored in the carbon-based supercapacitors, electroactive molecules of the quinone type are grafted covalently to the carbon surface. The functionalization method used is the chemical reduction of a diazonium salt generated in situ which allows the spontaneous grafting of a substituted phenyl group.

Theme: In-situ functionalisation of composite electrodes by a "non-covalent" approach for pseudo-capacitive storage

In order to increase the energy of the supercapacitor electrodes, we have proposed a new concept to graft by pi-stacking interactions a supercapacitor electrode by pyrene derivatives either operando (during cell operation) or In situ (open circuit) while limiting the alteration of electronic transport. The performances measured in half-cell are remarkable because it is possible, according to the type of carbon selected in an electrode of 10 mg / cm 2, to deliver up to 125 kW / kg_electrode in fast discharge and 280 Wh / kg_electrode during slow discharges (8 minutes).

Theme: Functionalization of activated carbon electrodes for supercapacitor electrodes in organic medium

This theme is the result of a collaboration with the MOLTECH Anjou laboratory and Dr. Charles Cougnon, in the framework of the Estelle Lebègue thesis ( "Grafting of electroactive molecules on activated carbons for the electrochemical storage of energy"). This thesis, initiated through the regional project PERLE2, makes it possible to envisage the use of activated carbon electrodes modified by electroactive molecules, operating in an organic medium with an increased energy density compared to the current systems based on Carbon electrodes.

Evolution of the capacity of a composite electrode
CF in an M-M electrolyte cycled at 100mV / s between 2.0 and 4.4V

The three previous aspects are taken into account in the recently launched ANR ICROSS project. This project aims to double the energy density of existing supercapacitors from 5 to 10 Wh / kg (or 7 to 15 Wh / L). Unlike most current research efforts aimed at replacing carbon with other materials (oxides, nitrides), which leads to drastic changes in manufacturing processes, we propose to keep the carbon electrode but by implementing Electroactive molecules that will be anchored to the carbon surface. This strategy makes it possible to add a faradic component to the carbon double layer capacity. This objective will be achieved by keeping the same cell voltage (or slightly higher), almost the same double layer capacitance (EDLC), but by adding an additional faradic capacitance (and not capacitance since these are purely faradic phenomena ) To the two carbon electrodes by functionalization of their surface with judiciously chosen electroactive molecules. The choice of electroactive molecules (multi-electron processes preferred to mono-electronic processes, low molecular weight, appropriate to the electrochemical window ...), choice of carbon (large surface, adequate porosity and little affected by molecular grafting, etc. ...), the interaction between molecules and carbon powder (high grafting efficiency, etc.) and finally the behavior of modified carbon electrodes in different organic electrolytes (or ionic liquid) are the key points controlling Final performance of modified carbon electrodes.

Références

Le Comte, A., Pognon, G., Brousse, T., Bélanger, D., Determination of the quinone-loading of a modified carbon powder-based electrode for electrochemical capacitor (2013) Electrochemistry, 81 (10), pp. 863-866.

Lebègue, E., Brousse, T., Gaubicher, J., Cougnon, C., Chemical functionalization of activated carbon through radical and diradical intermediates (2013) Electrochemistry Communications, 34, pp. 14-17.

Lebègue, E., Brousse, T., Gaubicher, J., Cougnon, C., Spontaneous arylation of activated carbon from aminobenzene organic acids as source of diazonium ions in mild conditions (2013) Electrochimica Acta, 88, pp. 680-687.

Weissmann, M., Crosnier, O., Brousse, T., Bélanger, D., Electrochemical study of anthraquinone groups, grafted by the diazonium chemistry, in different aqueous media-relevance for the development of aqueous hybrid electrochemical capacitor (2012) Electrochimica Acta, 82, pp. 250-256.

Lebègue, E., Brousse, T., Crosnier, O., Gaubicher, J., Cougnon, C., Direct introduction of redox centers at activated carbon substrate based on acid-substituent-assisted diazotization (2012) Electrochemistry Communications, 25 (1), pp. 124-127.

Madec, L., Bouvrée, A., Blanchard, P., Cougnon, C., Brousse, T., Lestriez, B., Guyomard, D., Gaubicher, J., In situ redox functionalization of composite electrodes for high power-high energy electrochemical storage systems via a non-covalent approach (2012) Energy and Environmental Science, 5 (1), pp. 5379-5386.

Lebègue, E., Madec, L., Brousse, T., Gaubicher, J., Levillain, E., Cougnon, C., Modification of activated carbons based on diazonium ions in situ produced from aminobenzene organic acid without addition of other acid (2011) Journal of Materials Chemistry, 21 (33), pp. 12221-12223.

Pognon, G., Brousse, T., Demarconnay, L., Bélanger, D., Performance and stability of electrochemical capacitor based on anthraquinone modified activated carbon (2011) Journal of Power Sources, 196 (8), pp. 4117-4122.

Pognon, G., Brousse, T., Bélanger, D., Effect of molecular grafting on the pore size distribution and the double layer capacitance of activated carbon for electrochemical double layer capacitors (2011) Carbon, 49 (4), pp. 1340-1348.