Abstract: For oxygen reduction in a battery an auxiliary electrode is provided having two layers, one with hydrophilic characteristics, the other hydrophobic. The hydrophilic layer is preferably of activated carbon bound in plastic and the hydrophobic layer of porous polytetrafluorethylene. Electrical contact is established between a conductor on the outside of the activated carbon layer and the negative main electrode. Preferably the exposed surface of the auxiliary electrode is provided with a metal ion barrier. Also preferably at least two such auxiliary electrodes are provided to make the battery orientation insensitive.