The Li6PS5Cl (NEI) SE powder was pretreated by a wet ball milling process to reduce the size of the agglomerates and this treatment was decided based on an experimental study assisted by Machine learning (ML) to decide the best milling conditions to produce Li6PS5Cl SE thin films . Wet ball milling experiments were executed using a ball milling machine (Pulverisette 7, Fritsch) with 10 mm-diameter zirconia milling media and a zirconia jar under the atmosphere of a dry room. P-xylene (≥ 99%, Sigma-Aldrich) was mixed with Li6PS5Cl powder and then milled at 300 rpm for 2 hours. After milling, the mixture was left to dry under a vacuum at 80°C for an overnight to obtain the wet milled SE (WM-SE) powder. Then, the PSD of the WM-SE was collected manually from several Scanning Electron Microscopy (Quanta 200F, FEI) images where the number of samples recorded was over 2000.