Nouvelles stratégies de production in situ de sels de diazonium pour la modification éléctrochimique de surfaces

Date du colloque : 07/2011</p

Conception et caractérisation d’une batterie organique obtenue par greffage direct de molécules électroactives sur carbone activé

Date du colloque : 07/2013</p

Toward fully organic rechargeable charge storage devices based on carbon electrodes grafted with redox molecules

Activated carbon powders modified with naphthalimide and 2,2,6,6-tetramethylpiperidine-N-oxyl were assembled into a hybrid electrochemical capacitor containing an organic electrolyte. The fully organic rechargeable system demonstrated an increase in specific capacitance up to 51%, an extended operating voltage of 2.9 V in propylene carbonate, compared to 1.9 V for the unmodified system, and a power 2.5 times higher

Direct introduction of redox centers at activated carbon substrate based on acid-substituent-assisted diazotization

Redox properties have been imparted to activated carbon with a high degree of functionalization by chemical grafting of 2-amino-4,5-dimethoxybenzoic add in situ diazotized. The diazotization reaction was accomplished in the presence or in the absence of HCl for estimating the positive or negative effect of the carboxylic acid substituent on the grafting yield. Thermal gravimetric analysis, X-ray photoelectron spectroscopy and cyclic voltammetry experiments show that when the carboxylic acid group participates to the diazotization reaction. the grafting yield is improved and becomes even better than when the carboxylic group is not present, increasing the capacitance of pristine carbon electrode from 120 to 200 F/g

Effect of the porous texture of activated carbons on the electrochemical properties of molecule-grafted carbon products in organic media

Two commercial activated carbons, different from their texture, were grafted with electroactive molecules and tested for determining what texture is well-suited for the grafting. Microporous and mesoporous carbons, having approximately the same BET surface area, were selected. The electroactive molecule consists in a naphthalimide compound having an amine as surface attachment group. The present work was divided in two parts. In a first part, the modified carbons were characterized by thermal gravimetric analysis, X-ray photoelectron spectroscopy, elemental chemical analysis and nitrogen gas adsorption measurements have been used for studying the impact of the grafting on the textural properties of carbons. In a second part, the electrochemical properties of the modified carbons were studied in propylene carbonate +1 M Bu4NBF4. Results show that the grafting ruins the performances of the microporous carbon, while the mesoporous carbon appears well-suited for the grafting, showing a good compromise between electrolyte-accessibility and ionic transportation

Optimization of Electronic Transport at the Nanoscale through the Formation of Molecular Junctions within Composite Electrodes for Li-battery

National audienc

Covalent vs. non-covalent redox functionalization of C-LiFePO4 based electrodes

During high rate utilization of porous Li battery, Li+ refuelling from the electrolyte limits the discharge kinetics of positive electrodes. In the case of thick electrodes a strategy to buffer the resulting sharp drop of Li+ concentration gradient would be to functionalize the electrode with anionic based redox molecules (RMR) that would be therefore able to relay intercalation process. The occurrence of these RMR in the electrode should not however, induce adverse effect on Li intercalation processes. In this respect, this work studies the effect of functionalizing LFPC based electrodes by either covalent or non-covalent chemistry, on Li intercalation kinetics. To do so, model molecules containing a nitro group were introduced at the surface of both carbon conducting additives and active material (C-LiFePO4). It is shown that presumably due to formation of sp(3) defects, covalent anchoring using diazonium chemistry inhibits the intercalation kinetics in C-FePO4. On the contrary, if molecules such as pyrene derivatives are immobilized by pi-staking interactions, Li intercalation is not impeded. Therefore non-covalent functionalization of pyrene based RMR appears as a promising route to relay Li intercalation reaction during high power demand. The framework for future development of this strategy is discussed. (C) 2013 Elsevier B.V. All rights reserved

Etude d’un dispositif hybride rechargeable entièrement organique pour le stockage électrochimique de l’électricité

Le développement de nouveaux dispositifs de stockage de l’électricité est un élément essentiel pour corriger l’intermittence des énergies éolienne et photovoltaïque, et garantir ainsi une bonne maîtrise des flux. Une stratégie prometteuse consiste à introduire des molécules organiques électroactives à la surface de carbones activés pour ajouter une contribution faradique au stockage de la charge électrique.[1] Cependant, les exemples de dispositifs hybrides tout organique sont encore très rares et la plupart des molécules sélectionnées sont électroactives en milieux aqueux.[2] Dans ce travail, nous avons sélectionné deux molécules électroactives en milieux organiques qui se complètent idéalement pour la préparation d’un dispositif de stockage hybride entièrement organique (Figure 1). Chaque électrode est conçue pour fonctionner sur un domaine de potentiel optimal afin de maximiser la densité d’énergie. Les performances de ce dispositif ont été évaluées dans une cellule Swagelok® à trois électrodes et comparées à celles d’un dispositif symétrique carbone-carbone constitué de poudre de carbone non-modifiée.[3] References [1] Pognon, G., Brousse, T., Demarconnay, L., Belanger, D. J. Power Sources 2011, 196, 4117. [2] Algharaibeh, Z.; Pickup, P.G. Electrochem. Commun. 2011, 13, 147. [3] Lebègue, E.; Brousse, T.; Gaubicher, J.; Retoux, R.; Cougnon, C. J. Mater. Chem. A 2009, 2, 8599

New Concept to Boost Energy and Power Peformance of Practical Electrochemical Devices

International audienc