The data processing of the DEMS results provides quantitative results on the types and amounts of gases being released. Validation of these results can be obtained by pressure monitoring during galvanostatic cycling (PMGC) as independent method. During a PMGC measurement, the pressure change in a closed cell of defined volume is followed during battery charge/discharge. The pressure change is directly related to the gas formation, i.e. the total amount of gas being released can be calculated from the pressure change, the dead volume of the cell and using the ideal gas law. A commercial device with two-electrode geometry was used for this purpose. A comparison of the accumulated gases measured independently with DEMS and PMGC over the first two cycles of a cell is shown in Figure . The total gas amounts found in both experiments are very comparable reaching values of around 200-250 µmol/g. This indicates accurate calibration of the DEMS data and correct assignment of the evolved gases. It is worthwhile to note that the PMGC data also shows an undulating behavior. This is initially unexpected as a continuous release of gas should result in a continuous increase in pressure. However, as the pressure cell is a closed system, some gases may be consumed by successive reactions or diffuse out of the cell over time. The latter would be particularly likely for H2. The signal of the pressure cell can be also influenced due to changes in the dead volume as the density of the electrode materials (NaMNO cathode) or their amounts (Na anode) depend on the state-of-charge. Overall, however, the PMGC measurements strongly support the analysis of the DEMS data obtained for the cell with the 2G electrolyte.