The present disclosure relates to improved processes for the preparation of metal hydrides. The present disclosure also relates to metal hydrides, e.g., metal hydrides prepared by the processes described herein, that exhibit enhanced hydrogen storage capacity when used as hydrogen storage systems.

A nickel-metal hydride secondary battery includes an outer can and a group of electrodes housed in the outer can together with an alkaline electrolytic solution. The group of electrodes includes a positive electrode and a negative electrode that are superposed with a separator interposed therebetween, and the negative electrode includes a hydrogen absorbing alloy for nickel-metal hydride secondary batteries, the hydrogen absorbing alloy having a single composition and composed of a plurality of crystal phases.

A hydrogen storage alloy suitable for prescribed pretreatment, that is, pretreatment wherein mechanical pulverization is performed after pulverizing a hydrogen storage alloy and absorbing/desorbing hydrogen is provided. The hydrogen storage alloy comprises a parent phase having a CaCu.sub.5-type, that is, an AB.sub.5-type crystal structure, wherein the A site is constituted from a rare earth element containing La; and the B site does not contain Co and contains at least Ni, Al, and Mn, with the ratio (Mn/Al) of the content of Mn (molar ratio) to the content of Al (molar ratio) being 0.60 or more and less than 1.56, and the ratio (La/(Mn+Al)) of the content of La (molar ratio) to the total content of the content of Al (molar ratio) and the content of Mn (molar ratio) being more than 0.92.

A battery includes an outer can, and an electrode group that is accommodated in the outer can together with an alkaline electrolyte solution, in which the electrode group includes a positive electrode and a negative electrode superposed with a separator being interposed therebetween, the positive electrode includes a positive electrode core and a positive electrode mixture packed in the positive electrode core, the positive electrode mixture includes a nickel hydroxide powder that is an aggregate of a particle of nickel hydroxide as a positive electrode active material, and a conductive material, the conductive material is a high-valent cobalt compound provided with a high valence and having a valence of higher than three, the high-valent cobalt compound containing sodium, and the conductive material is in an amount of 0.5 parts by mass or more and 5.0 parts by mass or less based on 100 parts by mass of the positive electrode active material.

A battery comprises an electrode group including a separator, a positive electrode and a negative electrode. The negative electrode comprises a negative electrode core, negative electrode mixture layers retained to the negative electrode core, and a fluorine resin layer disposed on the surface of the negative electrode mixture layers. The negative electrode mixture layers include a first outermost peripheral region located at the outermost periphery of the electrode group and a second outermost peripheral region located opposite to the first outermost peripheral region. When the amount of the fluorine resin constituting a first fluorine resin layer in a portion of the first outermost peripheral region is represented by A, and the amount of the fluorine resin constituting a second fluorine resin layer in a portion of the second outermost peripheral region is represented by B, a relation A>B is satisfied.

A nickel-hydrogen secondary battery includes an electrode group which contains a positive electrode, a negative electrode, and a separator, wherein the negative electrode includes a negative electrode core, and a negative electrode mixture layer held by the negative electrode core, wherein the negative electrode mixture layer contains a fluororesin; a quantity of the fluororesin, expressed by a mass applied per unit area of the negative electrode, is within a range of 0.2 mg/cm.sup.2 or more and 2.0 mg/cm.sup.2 or less; and a fluororesin content which is a ratio of the fluororesin contained in a unit volume of the negative electrode mixture layer is higher in an inner layer portion than in an outer layer portion in the negative electrode mixture layer.

A positive electrode for an alkaline secondary battery has high discharge capacity in a low temperature environment. The positive electrode included in the alkaline secondary battery has a positive electrode active material including 100 parts by mass of nickel hydroxide, and an additive including yttrium oxide. The nickel hydroxide includes an -phase single phase.

A battery includes an electrode group including an air electrode and a negative electrode stacked with a separator therebetween, and an accommodating bag accommodating the electrode group along with an alkali electrolyte solution. The air electrode includes a catalyst for an air secondary battery. This catalyst for an air secondary battery is produced by a method for producing a catalyst for an air secondary battery, the method including a precursor preparation step of preparing a bismuth-ruthenium oxide precursor, a calcination step of calcining the bismuth-ruthenium oxide precursor obtained in this precursor preparation step to form a bismuth-ruthenium oxide, and a nitric acid treatment step of immersing the bismuth-ruthenium oxide obtained by this calcination step in a nitric acid aqueous solution.

An alkaline secondary battery negative electrode and a composition forming the negative electrode, containing an active material, a binder resin, and an electrically conductive agent containing an electrically conductive carbon material. When a value of D50 is defined to be an average particle size X and a value of D20 is defined to be a particle size Y in a cumulative particle size distribution obtained by measuring the active material using a laser diffractometry particle size distribution meter, the average particle size X is 10 m or less, and the particle size Y is in the range of 30% to 70% of the average particle size X.

The present disclosure concerns a method of producing an activated negative electrode powder for use in nickel-metal hydride (NiMH) batteries, the method comprising the steps: a) providing at least one previously cycled NiMH battery; b) isolating a negative electrode powder from the previously cycled NiMH battery; c) wet-milling or milling the negative electrode powder, thereby obtaining a mixture of the activated negative electrode powder and a byproduct rich in rare earth hydroxides; and d) separating the activated negative electrode powder from the byproduct. The disclosure further relates to an activated negative electrode powder produced by the said method, as well as battery electrodes and batteries comprising such a powder.