Effects of fluorination on the hydriding and electrochemical properties of a gas-atomized Zr-based hydrogen storage alloy

The feasibility of using fluorination to improve the charging/discharging abilities of a Zr-based AB₂ hydrogen storage alloy prepared by atomization has been evaluated. Electrodes produced by the as-received powder have only 73% of the discharge capacity of that prepared from cast alloy. Because of the difference in cooling rate, larger as-atomized powder consisted of a profoundly dendritic structure on the surface, while the smaller ones tended to have a smoother surface. After F treatment for 20 or 60 min, the powder possessed better activation properties and discharge capacities, although the hydrogenation ability did not improve much. F treatment also enhanced the rate capability of alloy electrodes. It was found that the F ions preferably dissolved the oxide layer on the powder surface, and formed channels connecting the surface Ni-rich layers formed during the treatment. All these factors contributed to the improvement of the electrochemical properties of the atomized powder.