Ionic Liquid Electrolytes for Metal-Air Batteries: Interactions between O2, Zn2+ and H2O Impurities. Issue 7 (1st January 2020)

• Record Type: Journal Article
• Authors: Alwast, D.; Schnaidt, J.; Jusys, Z.; Behm, R. J.
• Is Part Of: Journal of the Electrochemical Society. Volume 167:Issue 7(2020)
• Publication Date: 2020-01-01
• Subjects: Batteries -- Ionic Liquids -- Oxygen Evolution Reaction -- Oxygen Reduction Reaction; Electrochemistry -- Periodicals; 541.3705
• DOI: 10.1149/2.0052007JES
• Languages: English
• ISSNs: 0013-4651

Abstract

Abstract : Motivated by the potential of ionic liquids (ILs) to replace traditional aqueous electrolytes in Zn-air batteries, we investigated the effects arising from mutual interactions between O2 and Zn(TFSI)2 as well as the influence of H2 O impurities in the oxygen reduction/oxygen evolution reaction (ORR/OER) and in Zn deposition/dissolution on a glassy carbon (GC) electrode in the ionic liquid N-butyl-N-methylpyrrolidinium bis(trifluoromethanesulfonyl)-imide (BMP-TFSI) by differential electrochemical mass spectrometry. This allowed us to determine the number of electrons transferred per reduced/evolved O2 molecule. In O2 saturated neat BMP-TFSI the ORR and OER were found to be reversible, in Zn 2+ containing IL Zn deposition/stripping proceeds reversibly as well. Simultaneous addition of O2 and Zn 2+ suppresses Zn metal deposition, instead ZnO2 is formed in the ORR, which is reversible only after excursions to very negative potentials (−1.4 V). The addition of water leads to an enhancement of all processes described above, which is at least partly explained by a higher mobility of O2 and Zn 2+ in the water containing electrolytes. Consequences for the operation of Zn-air batteries in these electrolytes are discussed.