Munehisa Ikoma

ALKALINE STORAGE BATTERY

An alkaline storage battery includes, as main constituent elements, a positive electrode having nickel hydroxide as an active material, a negative electrode, a separator, and an electrolyte made of an aqueous alkali solution, and a foamed three-dimensional porous substrate composed of nickel as a main component is used as a core substrate of the positive electrode, and the weight ratio of this core substrate in the positive electrode is set to 30% to 50%, thereby allowing both electron conductivity and ion conductivity of the positive electrode, with long life and high output even under severe conditions.

Self‐Discharge Mechanism of Sealed‐Type Nickel/Metal‐Hydride Battery

Factors affecting the self-discharge rate of a nickel/metal-hydride (Ni-MH) battery, generally much higher than that of nickel/cadmium (Ni-Cd) battery, are investigated, and the self-discharge mechanism is discussed. Ammonia and amine participate in the shuttle reaction like nitrate ion in the Ni-Cd battery, resulting in acceleration of the self-discharge. When nonwoven fabric made of sulfonated-polypropylene is used as a separator instead of conventional polyamide separator, the self-discharge rate of the Ni-MH battery is strongly depressed, to the same level as that of Ni-Cd battery.

Effect of alkali-treatment of hydrogen storage alloy on the degradation of Ni/MH batteries

Alkali-treatment at high temperature of the hydrogen storage alloy which was used as the negative electrode of nickel/metal-hydride batteries could enhance the cycle life. Al dissolves from the alloy surface, rare earth metal hydroxides form on the alloy surface, while Ni and Co exist as metals near the surface. Mn dissolves first and then deposits again as an oxide on the alloy surface. The corrosion reaction caused by alkali-treatment of the alloy stops at a certain stage. The above three points can be considered as the main factors for the long cycle life for the alkali-treated alloys.

Method for producing hydrogen storage alloy particles and sealed-type nickel-metal hydride storage battery using the same

A method for manufacturing hydrogen storage alloy particles comprises steps of obtaining a melt of the hydrogen storage alloy and pulverizing the hydrogen storage alloy by water atomizing process, whereby the melt is pulverized by contacting or colliding with high-speed jetting thereto to be dispersed in the form of solidified fine particles. By employing an aqueous solution of hypophosphorous acid or an alkali aqueous solution in place of water during the water atomizing process, or by etching the oxide films once formed on the surface of the hydrogen storage alloy particles with an aqueous solution of a strong acid, the thickness of the oxide film can be made thinner, and thus a high discharge capacity of a battery configured with a negative electrode comprising the alloy particles can be realized.

Charge characteristics of sealed-type nickel/metal-hydride battery

Abstract Factors for elevating the battery internal pressure of sealed-type nickel/metalhydride (Ni–MH) battery during rapid charge were investigated, and a suppressing method and the mechanism were discussed. As a result, elevation of battery internal pressure during rapid charge was found to be caused by hydrogen gas generated at the negative electrode. It was also found that the battery internal pressure during rapid charge is notably suppressed by letting the surface of negative electrode be hydrophobic. This is considered to be owing to the promotion of chemical absorption of hydrogen onto the hydrogen storage alloy at the solid–liquid interface.

Rectangular sealed alkaline storage battery and module battery thereof

A relatively large rectangular sealed alkaline storage battery used for electric cars, etc. is disclosed. The battery has such an inner construction as to inhibit deformation of the electrode group caused by charging and discharging so as to improve the life characteristics. The electrode group comprises positive electrode plates alternating with negative electrode plates in a planar direction and separators between the adjacent electrode plates. The electrode group and an alkali electrolyte are inserted in a container, which is sealed by a cover provided with a safety vent and the position of the electrode group in the container is controlled by fixing poles to the cover. The amount of the alkali electrolyte is 1.5-2.5 cm3/ battery capacity 1 Ah. Especially, for a module battery, a given distance is provided between the shorter side face of the electrode group and the inner wall of the container, and the outer longer side faces of the container are constrained by a metallic plate.

Improvement of basic performances of a nickel–metal hydride battery

To develop a sealed-type nickel-metal hydride battery for use in portable equipment or in electric vehicles, investigations were conducted on negative electrodes using AB5-type hydrogen storage alloy and positive electrodes. For the cycle life performance of the battery, alkaline treatment of the alloy and the substitution of more than 50% to the alloy with Co were effective. For the positive electrode, zinc as a solid solution in the nickel positive electrode obviously prevented γ-NiOOH from being formed in the charging process of β-Ni(OH)2 and suppressed the migration of the electrolyte solution in the separator to the active material of the positive electrode. Also, hydrophobic treatment of the surface of the alloy was effective to prevent the elevation of the battery internal pressure of the battery in high rate charge.