Abstract: A nickel hydrogen secondary battery accommodates an electrode group including a positive electrode and a negative electrode which are stacked one on top of another through a separator, together with an alkaline electrolyte. The battery contains Li, with a total amount of Li in the battery 2 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 rare earth-Mg—Ni-based hydrogen storage alloy which contains a rare earth element, Mg and Ni. The hydrogen storage alloy particles 44 includes, on the surface thereof, a rare earth hydroxide which is the hydroxide of a rare earth element and has a specific surface area of 0.1 to 0.5 m2/g.

Abstract: A nickel hydrogen secondary battery comprises an outer can and an electrode group accommodated in a hermetically sealed state together with an alkaline electrolyte solution in the outer can, wherein the electrode group comprises a positive electrode and a negative electrode stacked through a separator, wherein the negative electrode contains a hydrogen absorbing alloy powder that is an aggregate of particles of a hydrogen absorbing alloy, wherein the hydrogen absorbing alloy powder is such that when an average particle size of the particles is represented by M; a particle size of ½ of the M is represented by P; and a particle size of ? of the M is represented by Q, a content of the particles having a particle size equal to or smaller than the P is lower than 20% by mass of the whole of the hydrogen absorbing alloy powder; and the content of the particles having a particle size equal to or smaller than the Q is lower than 10% by mass of the whole of the hydrogen absorbing alloy powder.

Abstract: A nickel-hydrogen secondary battery includes an electrode group that includes a separator, a positive electrode and a negative electrode, and the negative electrode contains a hydrogen storage alloy having a crystal structure in which an AB2 type unit and an AB5 type unit are laminated, in which a PCT characteristic diagram at 80° C. includes a first plateau region having a hydrogen pressure Pd1 when hydrogen is stored by 0.25 times an effective hydrogen storage amount that is a hydrogen storage amount when a hydrogen pressure is 1 MPa, and a second plateau region having a hydrogen pressure Pd2 when hydrogen is stored by 0.70 times the effective hydrogen storage amount, and Pd1 and Pd2 satisfy a relation of 0.6?log10(Pd2/Pd1).

Abstract: A nickel hydrogen secondary battery accommodates an electrode group including a positive electrode and a negative electrode which are stacked one on top of another through a separator, together with an alkaline electrolyte. The battery contains Li, with a total amount of Li in the battery 2 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 rare earth-Mg—Ni-based hydrogen storage alloy which contains a rare earth element, Mg and Ni. The hydrogen storage alloy particles 44 includes, on the surface thereof, a rare earth hydroxide which is the hydroxide of a rare earth element and has a specific surface area of 0.1 to 0.5 m2/g.