110th Anniversary: Theory of Activity Coefficients for Lithium Salts in Aqueous and Nonaqueous Solvents and in Solvent Mixtures

Abstract

On the basis of work by Bernard and Blum [Bernard, O.; Blum, L. Binding Mean Spherical Approximation for Pairing Ions: An Exponential Approximation and Thermodynamics. J. Chem. Phys. 1996, 104, 4746-4754], Barthel et al. [Barthel, J.; Krienke, H.; Holovko, M.; Kapko, V.; Protsykevich, I. The Application of the Associative Mean Spherical Approximation in the Theory of Nonaqueous Electrolyte Solutions. Condens. Matter Phys.2000, 3, 23], and Simonin et al. [Simonin, J.-P.; Bernard, O.; Blum, L. Real Ionic Solutions in the Mean Spherical Approximation. 3. Osmotic and Activity Coefficients for Associating Electrolytes in the Primitive Model. J. Phys. Chem. B1998, 102, 4411-4417], this work presents and validates a molecularthermodynamic model for lithium salt activity coefficients in aqueous and nonaqueous single-and mixed-solvent systems. The Binding Mean Spherical Approximation gives electrolyte activity due to long-range electrostatic forces, short-range hard-sphere repulsion, and ion-pair formation. The theory shows good agreement with measured salt activities up to 3 molar in aqueous and nonaqueous solvents using a solvent-dependent, concentration-independent, center-to-center distance of closest approach between ions as the single fitting parameter for each electrolyte system. For mixed-solvent electrolytes, the local solvation environment around the ions dictates short-range interactions. To account for preferential ion solvation in a mixed solvent, the center-to-center distance is obtained from Wang and co-workers' Dipolar Self-Consistent-Field Theory [Nakamura, I.; Shi, A.-C.; Wang, Z.-G. Ion Solvation in Liquid Mixtures: Effects of Solvent Reorganization. Phys. Rev. Lett. 2012, 109, 257802]. For a particular salt in a binary solvent mixture at fixed temperature, the model predicts salt activity coefficients using only the fitted single-solvent distances-of-closest approach.

Shifting-reference concentration cells to refine composition-dependent transport characterization of binary lithium-ion electrolytes

“…Second, ion/solvent interactions hold more solvent molecules in the solution phase, effectively decreasing the solvent's vapor pressure [29] and causing a corresponding increase in the solute's activity coefficient, leading to a consequent increase in !. These competing trends are also substantiated by more recent electrolyte theories such as the binding mean spherical approximation [30]. Note that the crossing points where !…”

Interfacial Effects on Transport Coefficient Measurements in Li-ion Battery Electrolytes

“…Again, this trend does not match previous results or physical intuition which would dictate a thermodynamic factor of 1 in the ideal dilute concentration limit, an initial decrease below 1 in the thermodynamic factor for dilute solutions, and an increase in thermodynamic factor above 1 for solutions in the semi-concentrated regime. [37]…”

Thermodynamic gE Models and Equations of State for Electrolytes in a Water-Poor Medium: A Review

“…Although existing electrolyte models have been addressed for this purpose, the application was mainly restricted to aqueous systems such as in Sadowski’s group. , This underlines the urgent need for the further development of thermodynamic electrolyte models. Recently, electrolyte models have been suggested for water-poor conditions, especially in the Held/Sadowski, de Hemptinne, Kontogeorgis, and Smirnova research groups (refs − ). Still, these are restricted either to water solvent , or to only one salt, or they require complete reparameterization or even solvent-dependent parameters .…”

“…Recently, electrolyte models have been suggested for water-poor conditions, especially in the Held/Sadowski, de Hemptinne, Kontogeorgis, and Smirnova research groups (refs − ). Still, these are restricted either to water solvent , or to only one salt, or they require complete reparameterization or even solvent-dependent parameters . This points to a lack of physical consistency, a natural matter of fact in complex solutions overlain by numerous single effects.…”