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Electrochemical behavior of Zn/Zn(II) couples in aprotic ionic liquids based on pyrrolidinium and imidazolium cations and bis(trifluoromethanesulfonyl)imide and dicyanamide anions

Authors
Journal
Electrochimica Acta
0013-4686
Publisher
Elsevier
Publication Date
Volume
89
Identifiers
DOI: 10.1016/j.electacta.2012.11.023
Keywords
  • Room Temperature Ionic Liquids
  • Zn-Anode Secondary Batteries
  • Cyclic Voltammetry
  • Potentiodynamic Polarization
  • Tafel Analysis
Disciplines
  • Chemistry

Abstract

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 10−3mA/cm2, with the [Im]+ cation based RTIL possessing the highest value of 9.9×10−3mA/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.

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