Properties of pellet- and paste-type electrodes of AB5 hydrogen storage alloy

The discharge capacities of pellet- and paste-type AB 5 alloy electrodes were investigated. The LmNi 3.6 Al 0.4 Co 0.7 Mn 0.3 alloy was chosen and the alloy powder was coated with various amounts of copper by the electroless plating method. The pellet-type electrodes were fabricated by cold pressing the copper-coated alloy powder into disks of 10 mm diameter without any binding material and the paste-type electrodes were prepared by pasting the bare or the copper-coated alloy powders onto the foamed nickel with some organic binders. The discharge capacities of the electrodes were measured through half cell tests. The experimental results showed that for the pellet-type electrodes, as the amount of copper coat increased the discharge capacity per weight of electrode decreased whereas that per weight of alloy increased. For the paste-type electrodes the copper coated alloy powder showed a much higher discharge capacity than the bare alloy powder. However, the increase of the copper coat over a certain amount did not increase the discharge capacity per weight of alloy while decreasing that per weight of electrode. Considering the discharge capacity and mechanical endurance, the most promising electrode was the paste-type electrode with 2.5 wt.% Cu-coated alloy powder and no carbon black.