HYDROGEN STORAGE ALLOY AND ELECTRODE FOR NICKEL-HYDROGEN BATTERY USING THE SAME

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PROBLEM TO BE SOLVED : To provide a hydrogen storage alloy which imparts a uniform performance to a battery and shows a high activity at the initial stage, and a nickel-hydrogen secondary battery using the same. SOLUTION : The AB5-type hydrogen storage alloy has a CaCu5 crystal structure, a composition represented by the formula : MmNiaMnbAlcCodMe(wherein Mm is a misch metal; M is one chosen from Cu, Ti, V, Cr and Zn; and a-e each represents a mole number against 1 molar Mm and satisfies 4.8≤a+b+c+d≤5.4, 3.5≤a≤4.5, 0.2≤b≤0.7, 0.1≤c≤0.4, 0.1≤d≤0.8, 0≤e≤0.2 and 4.80≤a+b+c+d+s≤5.40), a carbon content of the alloy of ≤300 ppm and an iron content of ≤0.5 wt.%. The hydrogen storage alloy thus obtained shows a high activity at the initial stage and is suitably used as a negative electrode of the nickel secondary battery.