Chasing Aqueous Biphasic Systems from Simple Salts by Exploring the LiTFSI/LiCl/H2O Phase Diagram

Nicolas Dubouis (1, 2) , Chanbum Park (3, 4) , Michael Deschamps (2, 5) , Soufiane Abdelghani-Idrissi (6) , Matej Kanduč (3, 7) , Annie Colin (6) , Mathieu Salanne (8, 2) , Joachim Dzubiella (3, 9) , Alexis Grimaud (2, 1) , Benjamin Rotenberg (2, 8)

1 CSE - Chimie du solide et de l'énergie
2 RS2E - Réseau sur le stockage électrochimique de l'énergie
3 HZB - Helmholtz-Zentrum Berlin für Materialien und Energie GmbH = Helmholtz Centre Berlin for Materials and Energy = Centre Helmholtz de Berlin pour les matériaux et l'énergie
4 HU Berlin - Humboldt-Universität zu Berlin = Humboldt University of Berlin = Université Humboldt de Berlin
5 CEMHTI - Conditions Extrêmes et Matériaux : Haute Température et Irradiation
6 ESPCI Paris - Ecole Superieure de Physique et de Chimie Industrielles de la Ville de Paris
7 IJS - Jozef Stefan Institute [Ljubljana]
8 PHENIX - PHysicochimie des Electrolytes et Nanosystèmes InterfaciauX
9 Albert-Ludwigs-Universität Freiburg

Aqueous biphasic systems (ABSs), in which two aqueous phases with different compositions coexist as separate liquids, were first reported more than a century ago with polymer solutions. Recent observations of ABS forming from concentrated mixtures of inorganic salts and ionic liquids raise the fundamental question of how “different” the components of such mixtures should be for a liquid–liquid phase separation to occur. Here we show that even two monovalent salts sharing a common cation (lithium) but with different anions, namely, LiCl and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI), may result in the formation of ABSs over a wide range of compositions at room temperature. Using a combination of experimental techniques and molecular simulations, we analyze the coexistence diagram and the mechanism driving the phase separation, arising from the different anion sizes. The understanding and control of ABS may provide new avenues for aqueous-based battery systems.

Domaines: Chimie théorique et/ou physique

Nicolas Dubouis, Chanbum Park, Michael Deschamps, Soufiane Abdelghani-Idrissi, Matej Kanduč, et al.. Chasing Aqueous Biphasic Systems from Simple Salts by Exploring the LiTFSI/LiCl/H2O Phase Diagram. ACS Central Science, 2019, 5 (4), pp.640-643. ⟨10.1021/acscentsci.8b00955⟩. ⟨hal-02124064⟩