Three electrolytes were used in this study; (i) 1 M tetraethylammonium tetrafluoroborate (NEt4BF4) in acetonitrile, (ii) 1 M tetraethylphosphonium tetrafluoroborate (PEt4BF4) in acetonitrile, and (iii) undiluted 1-butyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (BMIM-TFSI) ionic liquid. PEt4BF4 was purchased from TCI Chemicals. BMIM-TFSI was purchased from IoLiTec Ionic Liquids Technologies. NEt4BF4 and PEt4BF4 were dried under vacuum at 100 °C for 72 h before being transferred to a N2 glovebox. Anhydrous acetonitrile (ACN) was purged with N2 for 3 h before being taken into a glovebox, where it was further dried using activated 3 Å molecular sieves. BMIM-TFSI was dried at room temperature under a dynamic vacuum for 120 h before being transferred to a N2 glovebox.