To increase an initial hydrogen absorption speed by a method wherein a specific surface area of spherical powder obtained with misch metal being applied as its raw material is defined.
Spherical powder is produced by a gas atomizing process from mixed molten metal of misch metal, nickel and other metals under application of inert gas. As required, the powder is heat treated at 600 to 1000°C for about 30 minutes to 20 hours. This heat treatment is carried out for eliminating stain left in the powder particle when it is solidified, preventing breakage of the powder particle caused by repetition of electrical charging and electrical discharging and decreasing the reduction in a capacity of the battery. Then, the powder is processed with acid in such a way that its specific surface area becomes more than 0.03m2k/g. With such an arrangement as above, oxide covering the surface of the powder particle is substantially removed and concurrently the flat surface of the particle is etched in a complex manner, resulting in that its surface area is remarkably increased and further an initial activation of powder reaches a value required as a battery.
KIMURA DAISUKE
NISHIKAWA SHUNICHIRO
MARUO TADAYUKI
