In this work, we examplarily focused on the IL N -methyl-N -propylpiperidinium bis(trifluoromethane)sulfonimide ([MPPip][TFSI]), which we had previously used for different electrochemical studies. We studied batches purchased between 2017 and 2022 from two suppliers and with different supplied purity, summarised in Table ). Additional information on the pre-treatments and evaluated water contents for the individual measurements presented in the manuscript and the SI are summarised in Table of the SI.