Nickel hydrogen secondary battery

A nickel hydrogen secondary battery comprising an electrode group hermetically enclosed in a container together with an alkaline electrolyte, the electrode group including a positive electrode and a negative electrode which are stacked one on top of another through a separator, wherein

• the nickel hydrogen secondary battery contains Li, with a total amount of Li in the nickel hydrogen secondary battery of 15 to 50 mg/Ah, as determined as the mass in terms of LiOH per Ah of the positive electrode capacity,
• the negative electrode includes particles of a rare earth-Mg—Ni-based hydrogen storage alloy which contains a rare earth element, Mg and Ni,
• the particles of the hydrogen storage alloy include, on the surface thereof, a rare earth hydroxide which is a hydroxide of the rare earth element, and have a specific surface area of 0.1 to 0.5 m2/g, and
• the hydrogen storage alloy has a composition excluding yttrium in non-incidental quantities, and the composition is represented by a general formula:
• Ln1-xMgx(Ni1-yTy)z, wherein Ln represents at least one element selected from La, Pr, Nd, Pm, Sm, Eu, Ca, Sr, Sc, Ti, Zr and Hf;
• T represents at least one element selected from Mn, Co, V, Nb, Ta, Cr, Mo, Fe, Al, Ga, Zn, Sn, In, Cu, Si, P and B;
• and the subscripts x, y and z satisfy relations 0<x≤1, 0≤y≤0.5, and 2.5≤z≤4.5, respectively.