Aspects of nickel-cadmium cells in single cycle applications. III. Effects of electrolyte additives on cadmium hydroxide crystal growth in sintered nickel negative electrodes during discharged storage

Abstract

The single duty cycle application requires nickel-cadmium cells to be stored for long periods in a discharged, short-circuited state. Under these conditions Cd(OH)2 active material in the negative electrode is subject to crystal growth processes which result in reduced charge efficiency when cycled after storage. Of equal importance, however, is the observed gross redistribution of Cd(OH)2 active material, whereby crystals penetrate into the separator, sometimes as far as the positive electrode. This must be considered undesirable and could lead to internal short-circuiting of the cell. This paper examines the effects of various surfactant electrolyte additives on Cd(OH)2 crystal growth and capacity of sintered, negative electrode material, stored in excess 6 M KOH, at various temperatures between +30 and +60°C. Results show that, under the test conditions, low concentrations (⩽0.1%) of the anionic surfactants sodium lauryl sulphate and turkey red oil strongly suppress Cd(OH)2 growth and result in markedly higher aged electrode capacities compared to control electrodes stored in the absence of these additives.