Tailored 3‐Alkoxy‐<i>N</i>,<i>N</i>,<i>N</i>,2,2‐Pentamethylpropan‐1‐Ammonium <i>Bis</i>(trifluoromethylsulfonyl)Imide Ionic Liquids for Room‐Temperature Fluoride‐Ion Batteries

Abstract Two novel liquid electrolytes for room‐temperature fluoride ion batteries are presented. These electrolytes are based on ionic liquids with quaternary ammonium cations 3‐methoxy‐ N , N , N ,2,2‐pentamethylpropan‐1‐aminium (MNPA) and N , N , N ,2,2‐pentamethyl‐3‐(2,2,2‐trifluoroethoxy)propane‐1‐aminium (NPPA) combined with a bis (trifluoromethylsulfonyl)‐imide (TFSI) counterion. Quaternary ammonium fluorides can be added at concentrations up to 0.7 M to a functional fluoride electrolyte with a total diffusivity of 4.99 × 10 −12 m 2 s −1 , a viscosity of 260 mP⋅s and a wide operational voltage range exceeding 5.4 V. The liquid ion electrolyte with the MNPA cation supports stable fluoride ion shuttling for up to 100 h.