Anode Materials for Metal Hydride Batteries

The aim is to develop new hydrogen storage alloys. The alloys are to be used as active material in the negative electrode of nickel metal hydride batteries (NiMH). State-of-the-art for NiMH is intermetallic compounds based on rare earth elements. These are developed from LaNi5. CaNi5 has the same structure and comparable hydrogen storage properties. If suitable electrode materials can be developed based on CaNi5, there is a potential for cheaper materials with a higher capacity. Intermetallics based on CaNi5 with partial substitutions are prepared and tested during the project. The hydrogen storage alloys are prepared from the elements by mechanical alloying in a planetary ball mill. After milling for several hours nanocrystalline intermetallics or amorphous alloys are formed. The alloys are characterized by X-ray powder diffraction before and after annealing in inert atmosphere. The hydrogen storage capacity is measured by gas absorption and the electrochemical properties are tested in half cells.