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

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 m² 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.