A Hybrid Anion for Ionic Liquid and Battery Electrolyte Applications: Half Triflamide, Half Carbonate

The better half: A hybrid imide anion consisting of a trifluorosulfonyl and a methylcarbonate group shows a unique coordination behaviour. Owing to the combination of electron‐withdrawing groups the new anion is less weakly coordinating than the symmetric TFSI salt. Reversible Na deposition and stripping was established in ethylene carbonate:propylene carbonate (EC:PC) electrolyte.

Abstract

The synthesis of a new imide type anion, methylcarbonate(trifluoromethylsulfonyl)imide (MCTFSI) is described and the physicochemical properties of its sodium and N‐butyl‐N‐methyl pyrrolidinium salts as well as structural information obtained by X‐ray diffraction studies of the sodium salt are discussed in terms of charge delocalisation, coordination chemistry and electrochemical behaviour with respect to the analogous imdides bis(trifluoromethanesulfonyl)imide (TFSI) and bis(fluorosulfonyl)imide (FSI). The insight obtained from studying the new anion informs and reemphasizes the concept of weakly coordinating anions and coordination chemistry in designing electrolyte salts.

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