Details

Autor(en) / Beteiligte

• Chen, Ying
• Ryu, Jaegeon
• Bazak, J. David
• Nguyen, Dan Thien
• Han, Kee Sung
• Li, Zheng
• Hu, Jian Zhi
• Mueller, Karl T
• Murugesan, Vijayakumar

Titel

Ion Solvation-Driven Liquid–Liquid Phase Separation in Divalent Electrolytes with Miscible Organic Solvents

Ist Teil von

• Journal of physical chemistry. C, 2023-08, Vol.127 (31), p.15443-15453

Ort / Verlag

United States: American Chemical Society

Erscheinungsjahr

2023

Quelle

Alma/SFX Local Collection

Beschreibungen/Notizen

• Liquid–liquid phase separation (LLPS) is a common phenomenon, but LLPS of electrolytes prepared in miscible organic solvents is rarely documented. In this study, we report four new cases of LLPS that occur in MgTFSI2 or ZnTFSI2 electrolytes in mixed organic solvents, and we use multimodal NMR methods to investigate the speciation differences between the upper and lower phases of these electrolytes. The conditions for the formation of this LLPS share four common features: cations with high charge density; anions with low charge density; a strongly coordinating solvent (indicated by its Gutmann donor number) with high compressibility; and a relatively weak coordinating solvent with low relative permittivity and high mobility. With these conditions, the cations tend to draw the strongly coordinating solvents together to form a densely packed, energetically favorable ion solvation region, while the cosolvents with low relative permittivity tend to form an ion-depleted dilute phase. Therefore, the driving force for LLPS with miscible solvents is the preferred interaction between cations and the strongly coordinating solvents that overcomes entropy loss due to phase separation. Furthermore, contact ion pairs and large ion aggregates are clearly evidenced in the dilute upper layer due to the incomplete screening of electrostatic interactions by the weaker cosolvent. This LLPS driven by cation solvation may be more common in multivalent electrolytes and is a design consideration that should not be overlooked in this context.