Revisiting the driving force inducing phase separation in PEG-phosphate aqueous biphasic systems.

Liquid phase separation using aqueous biphasic systems (ABS) is widely used in industrial processes for the extraction, separation and purification of macromolecules. Using water as the single solvent, a wide variety of solutes have been used to induce phase separation including polymers, ionic liquids or salts. For each system, polymer-polymer, polymer-ionic liquid, polymer-salt or salt-salt, different driving forces were proposed to induce phase separation.

Direct imaging of micrometer-thick interfaces in salt-salt aqueous biphasic systems.

Unlike the interface between two immiscible electrolyte solutions (ITIES) formed between water and polar solvents, molecular understanding of the liquid-liquid interface formed for aqueous biphasic systems (ABSs) is relatively limited and mostly relies on surface tension measurements and thermodynamic models. Here, high-resolution Raman imaging is used to provide spatial and chemical resolution of the interface of lithium chloride - lithium bis(trifluoromethanesulfonyl)imide - water (LiCl-LiTFSI-water) and HCl-LiTFSI-water, prototypical salt-salt ABSs found in a range of electrochemical applications. The concentration profiles of both TFSI anions and water are found to be sigmoidal thus not showing any signs of a positive adsorption for both salts and solvent.

Toggling Calcium Plating Activity and Reversibility through Modulation of Ca Speciation in Borohydride-based Electrolytes.

Learning how to tailor Ca speciation and electroactivity is of central importance to engineer next-generation battery electrolytes. Using an exemplar dual-salt electrolyte, Ca(BH) + Ca(TFSI) in THF, this work examines how to modulate a critical parameter proposed to govern electroactivity, the BH /Ca ratio. Introduction of a more-dissociating source of Ca via Ca(TFSI) drives re-speciation of strongly ion-paired Ca(BH), confirmed by ionic conductivity, Raman spectroscopy, and reaction microcalorimetry measurements, generating larger populations of charged species and enhancing plating currents.