Thermal properties of alkali bis(pentafluoroethylsulfonyl)amides, MPf(2)N (M = Li, Na, K, Rb, and Cs), and their binary mixtures have been revealed. Phase diagrams have been constructed for 10 binary systems, and their eutectic compositions and temperatures have been determined. It was found that the molten salt electrolytes with melting points in the intermediate temperature range (450 to 650) K are easily formed by mixing two kinds of single MPf(2)N salts.