To mitigate the aforementioned issues, repositories containing appropriately annotated data obtained with different methods and starting materials and reported by various research groups would allow for determining benchmark systems. Currently, there are several approaches to developing ontologies and repositories in this research area. However, these do not yet provide a definite solution for reporting and storing the data from this work. Using literature data currently available in a database dedicated to CVs for single-crystal electrodes, 53 we compared CVs for Au(111) recorded in the herein investigated IL, which are shown in the Supporting Information (SI 2). The data from the repository show similar discrepancies to those illustrated in Figure . However, the origin of the discrepancies can not be inferred due to the limited number of database entries and possibly also missing metadata. Yet another issue for electrochemical measurements in nonaqueous electrolytes is that reference electrode potentials cannot simply be adjusted to each other, making a comparison even more tedious. Approaches are currently being explored to mitigate this issue. In this work, we demonstrated the use of welldefined single-crystal electrodes (Au(111)) for assessing the quality of ionic liquid electrolytes ([MPPip][TFSI]). Using cyclic voltammetry, we measured different electrochemical behaviours for batches of the same IL, where the behaviour was independent of the supplier and the sup-plied purity. We also exemplified that surface science techniques requiring UHV conditions are a great addition to the analytical toolbox for studying the purity of ILs. Here, we demonstrated with XPS measurements that molecular sieves might not be suitable for drying an ionic liquid since Na and Si are transferred during this process in the IL. Finally, after adding water to the IL, the electrochemical properties changed over time due to a slow decay of O 2 in the IL. In total, our study clearly illustrates the necessity of using ILs with different LOT numbers and/or from different suppliers. Even though it might seem obvious, detailed reporting of the purity of the electrolyte before and after a pretreatment is mandatory to avoid misinterpretation of the results.