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Time-resolved SERS study of the oxygen reduction reaction in ionic liquid electrolytes for non-aqueous lithium-oxygen cells

Abstract

Superoxide (O2•-) is the key intermediate formed during oxygen reduction in non-aqueous electrolytes. One significant obstacle towards the realisation of a practical lithium-oxygen (Li-O2) battery is electrolyte instability in the presence of radical oxides, principally superoxide. Here we use the Raman active bands of O2•- as a diagnostic molecule for probing the influence of the electrolyte on reaction processes and intermediaries at the electrode surface. In situ surface enhanced Raman studies of the interphase at a roughened Au electrode with controlled and dynamic surface potentials were performed in two ionic liquids with differing properties: 1-butyl-1-methyl-azepenium bis(trifluoromethanesulphonyl)imide (Aze14TFSI), which has a large/soft cation, and triethylsulphonium bis(trifluoromethanesulphonyl)imide (TESTFSI), which has a relatively small/hard and e- accepting cation. The counter-cation and potential were seen to significantly influence the radical nature of O2•-. The analysis of peak intensities and Stark shifts in O2•- related spectral bands allowed for key information on its character and electrolyte interactions to be elucidated. Time-resolved studies of dynamic surface potentials permitted real time observation of the flux and reorientation of ions at the electrode/electrolyte interface.

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Publication details

The article was accepted on 02 Jun 2017 and first published on 06 Jun 2017


Article type: Paper
DOI: 10.1039/C7FD00170C
Citation: Faraday Discuss., 2017, Accepted Manuscript
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    Time-resolved SERS study of the oxygen reduction reaction in ionic liquid electrolytes for non-aqueous lithium-oxygen cells

    P. Radjenovic and L. Hardwick, Faraday Discuss., 2017, Accepted Manuscript , DOI: 10.1039/C7FD00170C

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