Electrochemical characteristics of encapsulated metal-hydride-alloy electrodes

Metal hydride electrodes with copper-encapsulated alloys and non-coated alloys were fabricated using suitable conductive and binding agents. The charge-discharge characteristics of three kinds of hydride electrodes were comparatively investigated. The encapsulated alloy electrode is remarkably superior to the non-coated LaNi5-based one, discharging at a high rate and exhibiting a smaller capacity decay at the stage of cycle tests. The hydride alloy quality of hydride electrodes can be effectively determined by measuring rate capability. The results of vented cell experiments confirm that the capacity decay of non-coated alloy electrodes in sealed cells is not due to the oxidation of oxygen from the nickel hydroxide positive electrodes. The relationship between the equilibrium potential of hydride electrode and the equilibrium hydrogen pressure has been deduced by a succinct thermodynamic method, without consideration of the unknown activity of water and fugacity coefficient of hydrogen.