Plastic-bonded electrodes for nickel-cadmium accumulators: VI. Oxygen recombination rate on sealed cell cadmium electrodes

Abstract

The recombination ( i.e., reduction) of oxygen on pocket-type cadmium electrodes, utilizable in sealed Ni-Cd cells, occurs on areas covered with a thin layer of alkaline electrolyte. Hence, in the presence of a non-woven electrolyte carrier with a low permeability for oxygen, or by blocking the side of the electrode facing the gas space of the cell (which is not in contact with the electrolyte carrier), the recombination of oxygen is reduced to an insignificant level for sealed Ni-Cd cells. A comparison of results obtained with pocket-type and plastic-bonded cadmium electrodes showed that oxygen is reduced on metal parts of the electrode (perforated pocket, current collector, contacting metal screen) which are covered with a thin electrolyte layer, are easily accessible to oxygen, and are short-circuited by the electroactive Cd/Cd 2+ material. The latter has a sufficiently negative potential and electronic conductance to allow the electroreduction of oxygen to take place.