The PMGC measurements also revealed another important aspect when studying the gassing behavior of electrochemical cells. This concerns possible misinterpretation of data when using two-instead of three electrode cells. This aspect can be seen for cells the measured voltage between working and counter electrode is stated wrongly as the electrode potential of the working electrode, i.e. V vs. Na + /Na. The effect is negligible in case the polarization of the Na counter electrode is small. This is the case for the diglyme-based electrolyte (at reasonable currents). For carbonate electrolytes, however, the polarization can be much larger due to a more resistive SEI . The consequence of this is that the upper cut-off potential of the working electrode is effectively reached already at a lower value. For example, a targeted cut-off potential of 4.2 V vs. Na + /Na would be effectively reached already at 4.1 V vs. Na + /Na, if the counter electrode causes a 0.1 V polarization. This means, for example, that the stability of the electrolyte is overestimated.