Gamzenur Özsin You can Identify the electrochemical stability window for the electrolyte and electrodes in your Na-ion system. Actually the electrochemical window is the voltage range within which the electrolyte and electrodes remain stable without undergoing unwanted reactions or degradation. This information can usually be determined experimentally through cyclic voltammetry (LSV) or other electrochemical techniques such as in-situ X-ray diffraction or in-situ spectroscopy, to gain insights into structural and chemical changes within the electrodes during cycling.