| Abstract | Motivated by the potential of using room temperature ionic liquids (RTILs) as electrolytes to replace traditional aqueous electrolytes for Zn-anode secondary batteries, Zn/Zn(II) redox reactions have been studied in four aprotic RTILs based on pyrrolidinium ([Pyrr]+) and imidazolium ([Im] +) cations, and bis(trifluoromethanesulfonyl)imide ([TFSI] -) and dicyanamide ([DCA]-) anions. Cyclic voltammetry results suggest a smaller overpotential for Zn redox in [Im]+ cation based and [DCA]- anion based RTILs than in [Pyrr]+ and [TFSI]- based RTILs. Potentiodynamic polarization experiments indicate a strong dependence of the electrode reaction mechanism for the Zn species on the RTIL anions. In [TFSI]- based RTILs, Zn2+ ions are the electroactive species, with the electrode reaction being a single-step, two-electron transfer process. In [DCA]- based RTILs, two-step, single-electron reactions account for the electrode mechanism. The exchange current densities derived from Tafel analysis for the Zn species in the four RTILs are greater than 10-3 mA/cm2, with the [Im]+ cation based RTIL possessing the highest value of 9.9 × 10-3 mA/cm2. The results obtained will assist in obtaining a better understanding of the electrochemical behavior of Zn in RTILs, shedding light on the development of RTILs for Zn-anode secondary batteries. © 2012 Elsevier Ltd. All Rights Reserved. |
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