The nickel-hydrogen secondary battery

A nickel hydrogen secondary battery 2 includes an outer can 10 and an electrode group 22 accommodated in the outer can 10 in a sealed state together with an alkaline electrolyte. The electrode group 22 includes a positive electrode 24 and a negative electrode 26 having a separator 28 sandwiched therebetween, the alkaline electrolyte includes NaOH as the main solute, and the negative electrode 26 includes a hydrogen storage alloy having a composition represented by a general formula : Ln 1-x Mg x Ni y-z M z , wherein Ln is at least one element selected from rare earth elements and Zr; M is Al; subscripts x, y and z satisfy the following relations, respectively : 0‰¤x‰¤0.05, 3.3‰¤y‰¤3.6, and 0‰¤z‰¤0.50; and the content of La among rare earth elements in Ln is 25% or less.