Phase diagrams of binary mixtures of alkali bis(trifluoromethylsulfonyl)amides have been constructed and their eutectic compositions and temperatures have been determined. It has been revealed that the molten salt electrolytes having the melting points in the intermediate temperature range (373 to 473) K are easily formed by simple mixing of two kinds of single alkali bis(trifluoromethylsulfonyl)amides salts. The 1:1 or 3:1 double salt is occasionally formed for some binary systems.

Densities, viscosities and ionic conductivities of single salts and the binary eutectic mixtures of alkali bis(trifluoromethylsulfonyl)amides, MTFSAs (M = Li, Na, K, Rb, Cs), were measured in the temperature range of 413-573 K. Cyclic voltammetry revealed that the binary eutectic melts have wide electrochemical windows of 5.0-6.0 V. It was found that alkali metals reversibly deposit on a nickel electrode at the cathode limit potentials. The order of the deposition potential was determined to be Na > Li > (K, Rb, Cs).