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 La_xRe_yMg_1-x-yNi_n-m-vAl_mT_v (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.