Hydrogen storage alloy, negative electrode for nickel metal hydride secondary battery, nickel metal hydride secondary battery

摘要

PPROBLEM 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. PSOLUTION: The hydrogen storage alloy has a composition expressed by a formula RNiSBa/SBCoSBb/SB, AlSBc/SBMnSBd/SBMSBe/SB(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 3.30a5.00, 0.10b0.90, 0.30c0.80, 0d0.15, 0e0.30, and 4.90a+b+c+d+e5.50). 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 m are present. PCOPYRIGHT: (C)2009,JPO&INPIT