Hydrogen storage alloy for alkaline storage battery, and alkaline storage battery and alkaline storage battery system each including negative electrode having the alloy

摘要

To provide a hydrogen storage alloy for an alkaline storage battery that improves output power by pulverization of the alloy in the initial stage of partial charge and discharge cycles and that maintains its surface condition to improve the amount of lifetime work (Wh), and an alkaline storage battery and battery system. A hydrogen storage alloy for an alkaline storage battery includes a composition expressed by LaxReyMg1-x-yNin-m-vAlmTv (Re: rare earth element(s) including Y; T: Co, Mn, Zn; 0.17≦x≦0.64, 3.5≦n≦3.8, 0.06≦m≦0.22, v≧0), and a main phase of an A5B19 type crystal structure. A ratio of X/Y of the concentration ratio X of Al to Ni in a surface layer and the concentration ratio Y of Al to Ni in a bulk layer is 0.36≦X/Y≦0.85. An alkaline storage battery includes the hydrogen storage alloy in its negative electrode. An alkaline storage battery system performs partial charge and discharge control.

主权项

1. An alkaline storage battery comprising:
an electrode group including a hydrogen storage alloy negative electrode including negative electrode active material of a hydrogen storage alloy, a nickel positive electrode including positive electrode active material mainly containing nickel hydroxide, and a separator; an alkaline electrolyte; and an outer can housing the electrode group and the alkaline electrolyte, the hydrogen storage alloy including a composition expressed by
LaxReyMgi-x-yNin-m-vAlmTv, whereRe is at least one element selected from the group consisting of rare earth elements including Y and other than La,T is at least one element selected from the group consisting of Co, Mn, and Zn,0.17≦x≦0.64, 0.1≦1−x−y≦0.2, 3.5≦n≦3.8, 0.06≦m≦0.22, and v≧0, and has a main phase of an A5B19 type crystal structure, and a ratio of X/Y of the concentration ratio where X is Al/Ni % of aluminum to nickel in a surface layer and the concentration ratio where Y is Al/Ni % of aluminum to nickel in a bulk layer being 0.36 or more and 0.85 or less, and the hydrogen storage alloy negative electrode retaining the alkaline electrolyte in a retention amount, Z1, of 95 mg≦Z1≦125 mg per gram of the hydrogen storage alloy.