HYDROGEN STORAGE ALLOY, HYDROGEN STORAGE ALLOY ELECTRODE AND ITS MANUFACTURING METHOD, AND NICKEL

PROBLEM TO BE SOLVED : To quickly activate a nickel hydrogen storage battery in its initial period of operation, where the nickel hydrogen storage battery comprises a positive electrode using an active material of a powder chiefly containing nickel hydroxide, and a negative electrode using the active material of the powder of a hydrogen storage alloy containing rare earth element(s) and nickel (Ni) as main components and having a CaCu5 type crystal structure; and to provide the nickel hydrogen storage battery excellent in charge-discharge performance. SOLUTION : The hydrogen storage alloy contains the rare earth element(s) and nickel (Ni) as main components, and has the CaCu5 type crystal structure, where the ratio of a lattice constant in c-axis direction to a lattice constant in an a-axis direction of the crystal is 0.8084 or less. A manufacturing method makes the powder of the hydrogen storage alloy having the CaCu5 type crystal structure storage hydrogen so that a concentration (H/M) of hydrogen in the hydrogen storage alloy is 0.5 to 0.62, and keeps the powder less than 0.62 in H/M during afterward charging.