First, all batches were characterised by cyclic voltammetry using a well-defined Au(111) single crystal as working electrode. This electrode can be reproducibly prepared under various atmospheres, such as ultra-high vacuum, laboratory conditions, or in a glove box. The procedure for the electrode preparation and the experimental parameters for the following ex- For all investigated batches, two distinct electrochemical behaviours were observed in the CVs for Au(111). The cyclic voltammograms (CVs) recorded at a scan rate of 5 mV s -1 in two different batches of this IL are shown in Figure and b, covering a potential range from -1.5 V to 1.7 V (all potentials throughout this work are given versus the Zn/Zn[TFSI] 2 reference electrode). The black and red curves show the first and fifth cycles, respectively. CVs for the other batches are provided in the SI in Fig- . The respective behaviour for each batch is provided in Table .