Surface Study of Lithium−Air Battery Oxygen Cathodes in Different Solvent−Electrolyte pairs

F. MARCHINI; S. HERRERA; W.R. TORRERS; A.Y. TESIO; F.J. WILLIAMS; E.J. CALVO

LANGMUIR

AMER CHEMICAL SOC

Lugar: Washington; Año: 2015 vol. 31 p. 9236 - 9245

0743-7463

The O2/Li2O2 electrode reaction has been studied on lowsurface area Au electrodes in three solvent−electrolyte pairs (0.1 M LiPF6/DMSO, LiPF6/ACN, and LiBF4/ACN) using an electrochemical cell coupledto UHV XPS spectrometer, EQCM, AFM, and DEMS. The XPS spectra ofthe surfaces after treatment at selected electrode potentials for the O2reduction and reoxidation of the surface show the presence of C and Sfrom solvent decomposition and of F and P from electrolyte decomposition.Furthermore, Li 1s and O 1s peaks due to Li2O2 and decomposition productssuch as carbonate, organics, LiF, high oxidation sulfur, and phosphoruscompounds were also observed. Using ACN instead of DMSO results in lesssolvent decomposition, whereas using LiBF4 results in less electrolytedecomposition. XPS, AFM, and EQCM show that O2 reduction productsremoval only takes place at very high overpotentials. In agreement with XPS which shows removal of carbonate surface species, DEMS confirms evolution of CO2 and consumption of O2 at 4.5 V, but LiF cannot be removed completely in a round trip of the Li−O2 battery cathode.