The Maximum Electrical Conductivity of Associated Lithium Salts in Solvents for Lithium-Air Batteries

The choice of optimal electrolytes is crucial for improving the electrochemical performance of a lithium-air battery because it determines the morphology of the discharge products in the cathode and the conductivity of the electrolyte. We have critically analyzed an important aspect related to the behavior of highly associated electrolytes, as those used in lithium-air batteries: the prediction of the concentration of maximum conductivity. Lithium triflate and lithium bis(tri-fluoromethyl sulfonyl)imide in glymes of low dielectric constant (1,2-di-methoxyethane and bis(2-methoxy-ethyl)ether) were used as a model of electrolytes exhibiting strong ionic clustering. The viscosity and lithium transference number of all the electrolytes were measured, and it was found that the correlation between the concentration of maximum conductivity and coefficient that describes the high-order dependence of the electrolyte viscosity with the concentration is no longer valid in these electrolytes because of the failure of Walden's rule, although a qualitative correlation with the salts' association constant was observed.