Sylvain FRANGER
Institut de Chimie Moléculaire et des Matériaux d’Orsay, Université Paris Sud
http://www.icmmo.u-psud.fr/Labos/ERIEE/cv/cv_auto.php?ID=190
Vendredi 9 mars à 14h (salle Magat) :
“High entropy oxides as promising materials for safe and efficient green solid state batteries”
Résumé
Constant electrification of many devices requires the development of high efficiency batteries. In this field, all-solid-state technology has many advantages over conventional commercial cells.
Indeed, without liquid electrolyte, devices are safer and also comply with current environmental standards. However, usual solid electrolytes are not sufficiently conductive to allow ultra fast charge/discharge rates (which are crucial for high power applications).
The search for new fast ionic conductors, at room temperature, is thus of critical interest for manufacturing high power batteries. It has been shown recently that the entropic contribution to the Gibbs free energy can be used to stabilize new oxide phases, similarly to the situation that occurs in high entropy alloys.
In particular, a rock salt structure was observed for entropy stabilized (Mg, Cu, Ni, Co, Zn)O with a random occupation of the cation sites.
Following this pioneering study, we showed that these compounds (hereafter called HEOx, from high entropy oxides) exhibit promising properties, especially we showed that the cations in HEOx can be substituted by alkali ions (with an intrinsic charge compensation mechanism), or combinations of +1 and +3 elements (with a self-charge compensation between the substituents), while keeping the rock salt structure.
We have shown that Li and Na substituted HEOx exhibit very large values of ionic conductivity, which makes them among the best oxide-based conductors and we have then also demonstrated their efficient implementation in all solid state batteries.
