Séminaire de Monika Schönhoff (University of Münster)
Direct measurement of ion mobility by electrophoretic NMR and implications for correlated ion migration in concentrated electrolytes
le vendredi 9 octobre 2020 à 11h
en salle des conseils de l’UFR de Chimie (42.43.101) et en visio (lien à venir)
Résumé
Ion transport in electrolyte materials, e.g. for Li ion batteries, is often influenced by the strong ion correlations in concentrated electrolytes. Commonly employed multinuclear (e.g. 1H, 7Li, 19F) Pulsed-Field-Gradient (PFG)-NMR diffusion is not sufficient to identify the conductivity contributions of specific ion species, since the electrophoretic mobility µ has to be known. Electrophoretic NMR (eNMR) allows to directly measure the electrophoretic mobility of ions with NMR-active nuclei. The lecture presents its application to ionic liquids, polymeric and oligomeric (glyme) electrolyte systems. Drift velocities of ions and even of uncharged molecular components in the electric field can be identified. These lead to conclusions on ion correlation effects which control charge transport in concentrated electrolytes. Such correlation effects are for example evident in ion motion in clusters formed by Li+ coordination, or by the role of ion-ion anticorrelations of different ion species.
