A nickel-metal hydride secondary battery is provided with: an outer package can having an opening at an upper end; an electrode group accommodated in the outer package can together with an alkaline electrolyte; and a sealing body that seals the opening of the outer package can. The sealing body includes a cover plate having a central through hole, and a valve element made of an elastic material to close the central through hole. The valve element includes a cylindrical main body part having a base end surface that covers the central through hole, and an extended diameter part positioned on an opposite side of the main body part from the base end surface and having a diameter made larger than a diameter of the main body part. A ratio R of a thickness T of the extended diameter part to a total height H of the valve element is equal to or higher than 27%.

An electrolytic method of loading hydrogen into a cathode includes placing the cathode and an anode in an electrochemical reaction vessel filled with a solvent, mixing a DC component and an AC component to produce an electrolytic current, and applying an electrolytic current to the cathode. The DC component includes cycling between: a first voltage applied to the cathode for a first period of time, a second voltage applied to the cathode for a second period of time, wherein the second voltage is higher than the first voltage, and wherein the second period of time is shorter than the first period of time. The AC component has a frequency between about 1 Hz and about 100 kHz. The peak sum of the voltages supplied by the DC component and AC component is higher than the dissociation voltage of the solvent.

A conventional bipolar battery is constituted of a combination of cells hermetically sealed for preventing a liquid junction and preventing corrosion of a peripheral device due to a liquid leakage. Therefore, electrolytic solution injecting processes are carried out as many as the number of cells, so that much times and costs have been required for manufacturing a large-scale battery. In addition, a wiring space has been required since the cells are connected to one another with wires. The use of a current collector formed of a one-end closed tubular conductor, the current collector having a bottom protruding outward to form a protrusion, eliminates the wiring space and achieves a reduction in ohmic loss due to the wires. In addition, an electrolytic solution in one cell is separated by a water-repellent sheet from an electrolytic solution in another cell, so that a liquid junction is prevented.

The invention relates to a starved metal hydride battery. The battery is characterized in that the battery further comprises adding of oxygen gas or hydrogen gas or hydrogen peroxide or a combination thereof in order to rebalance the electrodes and replenish the electrolyte by reactions with the electrode materials.

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-MgNi-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 m.sup.2/g.

A bipolar electrode includes a metal foil, a first active material layer provided on a front surface of the metal foil, and a second active material layer having a larger area than the first active material layer and provided on a rear surface of the metal foil. The second active material layer includes a low density region disposed in a peripheral portion in plan view as viewed from a thickness direction of the metal foil, and a high density region disposed more inside than the low density region and having a smaller porosity than the low density region.

A nickel-metal hydride battery is provided with a positive electrode and a negative electrode including hydrogen absorbing alloys. The hydrogen absorbing alloys of the negative electrode include a first hydrogen absorbing alloy and a second hydrogen absorbing alloy having a higher hydrogen equilibrium dissociation pressure than the first hydrogen absorbing alloy. Each hydrogen absorbing alloy includes an element A having high affinity for hydrogen and an element B having low affinity for hydrogen. The ratio of a substance amount of the element B to a substance amount of the element A is greater in the second hydrogen absorbing alloy than the first hydrogen absorbing alloy.

A battery includes an electrode group including an air electrode and a negative electrode stacked with a separator therebetween, and a battery case accommodating the electrode group along with an alkali electrolyte solution, wherein the air electrode includes an air electrode mixture containing a pyrochlore-type composite oxide and a manganese oxide, and the pyrochlore-type composite oxide is a bismuth-ruthenium oxide.

The invention relates to a starved metal hydride battery. The battery is characterized in that the battery further comprises added oxygen gas or hydrogen gas or hydrogen peroxide or a combination thereof in order to rebalance the electrodes and replenish the electrolyte by reactions with the electrode materials.

This disclosure relates to novel manganese hydrides, processes for their preparation, and their use in hydrogen storage applications. The disclosure also relates to processes for preparing manganese dialkyl compounds having high purity, and their use in the preparation of manganese hydrides having enhance hydrogen storage capacity.