Kinetics of metal hydride electrodes when increasing the internal cell pressure

Abstract

An external argon gas pressure was applied to an electrochemical system where metal hydride electrodes made of LaNi 5 and MmNi 5 were investigated at different pressures using various electrochemical techniques. One could expect that the distinctive properties of the same alloy were unchanged regardless of the external pressure, but the differences in various properties for LaNi 5 at different applied external pressures were notable. It is assumed that this is a result of an improved charge efficiency because of a reduced hydrogen evolution. An increase of the discharge capacity with increasing external pressure was observed. The results indicate that the overpotential for the discharge reaction increases as the hydrogen evolution rate during charging increases. This increase might either be a result of mechanical rearrangement of the surface during hydrogen evolution or blocking of electrode surface because of remaining hydrogen gas bubbles in the electrode structure after charging.