We proudly invite you to read a paper co-authored by prof. François Béguin, laureate of Welcome programme realized by the Foundation, published in Nature Materials under the title “Exploring electrolyte organization in supercapacitor electrodes with solid-state NMR”.
Supercapacitors are electrochemical energy-storage devices that exploit the electrostatic interaction between high-surfacearea nanoporous electrodes and electrolyte ions. Insight into the molecular mechanisms at work inside supercapacitor carbon electrodes is obtained with 13C and 11B ex situ magic-angle spinning nuclear magnetic resonance (MAS-NMR). In activated carbons soaked with an electrolyte solution, two distinct adsorption sites are detected by NMR, both undergoing chemical exchange with the free electrolyte molecules. On charging, anions are substituted by cations in the negative carbon electrode and cations by anions in the positive electrode, and their proportions in each electrode are quantified by NMR. Moreover, acetonitrile molecules are expelled from the adsorption sites at the negative electrode alone. Two nanoporous carbon materials were tested, with different nanotexture orders (using Raman and 13C MAS-NMR spectroscopies), and the more disordered carbon shows a better capacitance and a better tolerance to high voltages.