Regensburg 2019 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 33: Solid-Liquid Interfaces III
O 33.2: Vortrag
Dienstag, 2. April 2019, 14:15–14:30, H10
The ionic liquid|cobalt oxide interface and interaction with lithium - A model study for the solid|electrolyte interphase in Li-ion batteries — •Florian Buchner1, Jihyun Kim1, and R. Jürgen Behm1,2 — 1Institute of Surface Chemistry and Catalysis, Ulm University, D-89069 Ulm, Germany — 2Helmholtz-Institute Ulm (HIU) Electrochemical Energy Storage, D-89081 Ulm, Germany
Here we report results of a UHV study on the interaction of an Ionic Liquid (IL) with lithium on different cobalt oxide thin films as a model study for the solid|electrolyte interphase (SEI) in Li-ion batteries (LIBs). After characterization of CoO(111) and Co3O4(111) by X-ray photoelectron spectroscopy (XPS) and scanning probe microscopy, the interaction of ultrathin films of the battery-relevant IL 1-butyl-1-methylpyrrolidinium bis(trifluoromethylsulfonyl)imide [BMP][TFSI] with Li on CoO and Co3O4(111) was investigated, employing mainly XPS. The measurements reveal that intact ion pairs adsorb on both CoOx surfaces and that postdeposition of Li results in the decomposition of the cations and anions (Li3N, LiCxHyNz, LiF, etc.). In addition, the measurements reveal that Li deposition (both in the presence and absence of an IL adlayer) leads to the conversion of Co2+ to Co0 on CoO and the transformation from Co3+ to Co2+ on Co3O4(111) in the near surface region, due to charge transfer from Li to the surface together with the formation of Li2O. Hence, the XP spectra resolve the initial stages of the chemical SEI formation (IL decomposition) (in the absence of an applied potential) as well as the reduction of CoOx, which both play an essential role in the function of LIBs.