New inorganic ionic liquids possessing low melting temperatures and wide electrochemical windows: Ternary mixtures of alkali bis(fluorosulfonyl)amides

Abstract

Four kinds of ternary phase diagrams of alkali bis(fluorosulfonyl)amides, LiFSA–NaFSA–KFSA, LiFSA–NaFSA–CsFSA, LiFSA–KFSA–CsFSA and NaFSA–KFSA–CsFSA, have been constructed. All the ternary systems possess the only one eutectic point around equimolar composition with the temperature of 309–318 K. The electrochemical window of the eutectic LiFSA–KFSA–CsFSA ((xLi, xK, xCs) = (0.30, 0.35, 0.35)) is as wide as 5.4 V at 323 K with the cathode limit being lithium metal deposition. The electrochemical window of the eutectic NaFSA–KFSA–CsFSA ((xNa, xK, xCs) = (0.40, 0.25, 0.35)) is 4.9 V at 323 K with sodium metal deposition as the cathode limit reaction.