The hydrogen storage alloy, a nickel-hydrogen secondary battery, a nickel hydrogen battery

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PROBLEM TO BE SOLVED : To provide a hydrogen storage alloy that has improved cycle characteristics and a high operation voltage of a battery, and can suppress self-discharge when the hydrogen storage alloy is used as the negative electrode active substance of a nickel hydrogen secondary battery, to provide a negative electrode for a nickel hydrogen secondary battery manufactured using the hydrogen storage alloy, and to provide a nickel hydrogen secondary battery manufactured using the negative electrode. SOLUTION : The hydrogen storage alloy has a composition expressed by a formula RNiaCob, AlcMndMe(in the formula, R indicates at least one type selected from rare earth elements containing Y, and M indicates at least one type selected from elements other than R, Ni, Co, Al, and Mn, where 3.30≤a≤5.00, 0.10≤b≤0.90, 0.30≤c≤0.80, 0≤d≤0.15, 0≤e≤0.30, and 4.90≤a+b+c+d+e≤5.50). The hydrogen storage alloy is used for the nickel hydrogen secondary battery, where the hydrogen storage alloy has Al concentration higher than that of a base phase confirmed by a Comp image of 500 magnifications by EPMA of the sectional structure of the alloy and an element mapping image of Al and no precipitation phases having a grain size of not less than 2.0 μm are present. COPYRIGHT : (C)2009, JPO&INPIT