Poor SEI formation of Na metals in carbonate electrolytes is a known issue in battery research . Our results therefore underline the general problem when comparing electrochemical measurements in two-electrode configuration, especially when using Li or Na as counter electrodes and different electrolyte formulations (ethers vs. The appearance of dimethyl ether (although at very small amounts) is different from our previous study in which H2, CO, CH4 and ethylene were found for symmetrical cells with a 2G electrolyte . This highlights the benefit of using the MCD algorithm and The detection of dimethyl ether is consistent with Qin et al. who suggested that this compound is a likely degradation product of 2G and it was found in Li-O2 batteries .