Investigating the electrochemical windows of ionic liquids

The structure effect on the electrochemical windows (EWs) was studied using cyclic voltammetry (CV) in 16 ionic liquids (ILs), consisting of various cations such as piperidinium, pyridinium, pyrrolidinium, phosphonium, morpholinium, ammonium, sulfonium and imidazolium, and anions including bis(trifluoromethylsulfonyl)imide, tris(pentafluoroethyl)trifluorophosphate, dicyanamide, trifluoroacetate and trifluoromethanesulfonate. It was found that all studied ILs have good EWs to be utilized as electrolytes in different electrochemical applications pertaining to industry. Furthermore, it was found that the structure of ILs affected the EW and both the cation and anion have important effect on the reductive and oxidative limits, respectively. The reductive limits of the studied ILs were found to follow the sequence of [P14,666]+ > [N112,1O2]+ > [HMPyrr]+ > [BMPyrr]+ > [EMIm]+ > [MOEMMor]+ ≈ [MOPMPip]+ > [S222]+ > [BMPy]+ ≈ [HPy]+ ≈ [HPPy]+. The oxidative limits were found to follow the sequence of [TFSI]− > [TPTP]− > [TfO]− > [DCA]− > [TFA]−.