So-called "corrosion" of the aluminum current collector in the electrolyte 1 M LiTFSI in ethylene carbonate : diethyl carbonate, EC:DEC (3:7, by wt) has been investigated by electrochemical and analytical methods. In fact, Al "corrosion" in this electrolyte is actually an anodic Al dissolution reaction. In addition to Al dissolution various electrolyte degradation processes were identified. A combination of a specially developed on-line ICP-OES method and in situ EQCM measurements revealed that before the dissolution of aluminum starts, an "activation" process takes place for ca. 6 hours, which is accompanied by strong electrolyte oxidation. The electrolyte decomposition reactions were investigated by ex situ IC measurements which showed that the LiTFSI decomposed and that F- s the main decomposition product. ex situ GC-MS measurements revealed that also the solvent decomposes and CO2 as well as ethoxyethanol are formed as degradation products. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.081302jes] All rights reserved.