Mechanistic aspects of the reactions in magnesium-air batteries: The presence of common additives such as the water scavenger borohydride and a complexing agent (18-c-6) leads to a multitude of electro-catalyzed and purely chemical side reactions during reversible Mg deposition/stripping and the OER/ORR in neat and O2-saturated, Mg-containing BMP-TFSI electrolytes, respectively, which are identified by DEMS.