METAL HYDRIDE ELECTRODES MADE BY DRY POWD ER PROCESS USING FLAKE COPPER AND FLAKE NICKEL POWDERS

Metal hydride electrodes were prepared by a dry powder process, in whi ch a mixture of hydrogen storage alloy and fine dendritic copper or ni ckel powder were press-bound on a nickel mesh without polymeric binder . Newly developed flake powders of copper and nickel were found to pro vide a higher utilization efficiency of hydrogen storage alloy and a h igher mechanical strength of the electrodes than conventional dendriti c powders. It was also found that the flake copper or the flake nickel formed a lamellar-type network structure in the electrode, providing better binding ability and a higher electrical conductivity than a con ventional powder molding. The copper mixture in the weight ratio of Cu / alloy=0.2 was press-molded satisfactorily at 98 MPa, while the nick el mixture (Ni / alloy=0.2) needed much higher pressure (294 MPa) to g et the same performance. Less nickel content than Ni / alloy=0.2 broug ht about lower utilization efficiency and shorter cycle life of the el ectrode. The effect of flake powder was more prominent for the AB(2)-t ype alloy than the AB(5)-type alloy.