Fouling and corrosion of electrode plates in nickel cadmium batteries

Abstract

The aim of this study is investigation of fouling propensity in nickel cadmium electrodes after degradation of alkaline-electrolyte from rich-hydroxide to rich-carbonate along with time. Gradually, CO2 absorption from the air into the alkaline electrolyte leads to the destruction of electrodes and the formation of precipitated layers resulting in reduction of electrical capacity and life time of batteries. Based on the microscopic observations (SEM), spectroscopic evidences (FTIR and XRD) and thermal experiments (TG-DTA) significant damages and fouling phenomena were categorized as: salt islands, graphite films, etched graphite, cadmium dendrites, cadmium oxide/sulfide and cathodic corrosion. The experimental results revealed that nickel cathodes have experienced more surface damages with respect to cadmium anodes. Although the anode is the source of cadmium species, however the fouling layers of cadmium oxide and cadmium sulfide were assigned to be the main causes of cathode damage, leading to the decreasing of electrode current and the increasing of internal resistance of the cells. On the other hand, the main damage on the surface of anode electrode was attributed to graphite coatings and cadmium hydroxide stripped from the cathode. The microscopic observations showed that almost 2% of cathode surface was corroded, while the anode surface had experienced no corrosion.