Patent ID: 8475608

Claim:
A magnesium-based hydrogen storage alloy which comprises a first phase of metallic magnesium (Mg) and second phase of a magnesium-containing intermetallic compound of formula Mg x M y , where M represents an alloying element forming the intermetallic compound by bonding Mg, x represents a mass percent of Mg and y represents a mass percent of M, which comprises from about 16 mass-% to about 63 mass-% of magnesium, the alloy comprising magnesium in a total amount which is not less than 60 mass-% and having a phase of a primary crystallized magnesium-containing intermetallic compound in its solidification structure, and wherein the total amount of magnesium is sufficient for obtaining a theoretical hydrogen occlusion quantity in the alloy of not less than 5 mass-%, and wherein the alloy has been initially activated at a temperature of not higher than 300° C. under a hydrogen pressure condition of not more than 3 MPa.