General approach: Another focus of this work was to find an improved way of processing the data from the DEMS measurements. The common way to analyze DEMS data in battery research is to follow one m/z ratio to quantify a certain gas . While this analysis is straight-forward, overlapping of signals caused by different gases can lead to misinterpretation. A common approach to deal with this problem is to correct the signals for contributions from other gases of known concentration . A less precise approach is to plainly define a m/z signal to a certain gas In this work, we follow a different approach. Instead of detecting single m/z values, the full mass spectra between 1 to 100 m/z is taken for the analysis. From the intensities of all m/z ratios, the most probable concentrations are fitted using a multiple concentration determination (MCD) algorithm. Therefore, an additive overlap of the individual spectra of the expected species is calculated, using the least-squares method to fit this to the baseline corrected spectra. Using a suitable calibration, this analysis provides the quantitative gas evolution rates for all expected gases from the full spectra. The described approach has been applied to mass spectrometry in the past but, to the best of our knowledge, has never been applied for DEMS studying Li-ion/Na-ion batteries.