JPH0521045A - Sealed battery - Google Patents

Abstract

PURPOSE:To suppress a self discharge when a battery being left in a charged state by providing a non-porous metal layer on a surface of a battery container made of a synthetic resin. CONSTITUTION:A closed type battery comprises a battery container A made of a synthetic resin, a non-porous metal layer B, a metal hydride electrode C, a separator D, and a nickel hydroxide electrode E. In the sealed battery of this constitution, the non-porous metal layer B is provided on the external or internal surface of the battery container A made of a synthetic resin. Thereby, hydrogens permeating the battery container A made of a synthetic resin are blocked by the metal layer B, the hydrogen penetration speed of which being small. As the result, the self discharging speed of a negative electrode accompanying hydrogen generation, is decreased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery having a negative electrode mainly composed of a hydrogen storage alloy and a battery container made of synthetic resin.

[0002]

2. Description of the Related Art A sealed battery having a hydrogen storage electrode mainly composed of a hydrogen storage alloy as a negative electrode includes an alkaline battery using a nickel hydroxide electrode or a manganese dioxide electrode as a positive electrode,
There is an acid battery using a lead electrode or the like for the positive electrode.

This hydrogen storage electrode uses a hydrogen storage alloy capable of reversibly storing and releasing hydrogen as an electrode, and the electrochemical redox reaction of the hydrogen is used for the electromotive reaction of the negative electrode of the battery. To do. The hydrogen storage alloy used for the hydrogen storage electrode is an intermetallic compound such as TiNi, Ti ₂ Ni, LaNi ₅ and TiMn ₂ or a material obtained by substituting the constituent elements of these intermetallic compounds with other elements. There is. These hydrogen storage alloys, when the composition is different, the hydrogen storage amount, the equilibrium hydrogen pressure, and the properties such as the retention capacity characteristics when charging and discharging are repeated in the electrolytic solution, so the composition of the alloy is changed,
Attempts have been made to improve the performance of hydrogen storage electrodes. A hydrogen storage alloy having an equilibrium pressure of about 0.01-1 atm at room temperature is often used for this electrode.

The hydrogen storage electrode is made of a porous material by bonding the powder of the hydrogen storage alloy with an electrolytic solution resistant polymer, sintering at a high temperature, or filling a foam metal. Was.

This type of sealed battery has a discharge capacity of several
As a container for a large battery of Ah or more, a container made of metal may be used, or a container made of an electrolytic solution resistant synthetic resin such as an acrylic-styrene copolymer or polypropylene may be used. When a metal container is used, it is necessary to seal the battery by welding, so that the efficiency of the battery assembling work is poor. However, when using a battery container made of synthetic resin, the battery can be sealed by bonding with an adhesive or by heat fusion at a much lower temperature than welding of metal,
Excellent in battery assembly work. In addition, when a battery container made of synthetic resin is used, an integrally molded product of a plurality of battery containers can be easily manufactured for an assembled battery composed of a plurality of batteries, which is also advantageous in that the battery container becomes inexpensive. is there.

[0006]

As described above, when a synthetic resin battery container is used as a battery container of a sealed battery having a negative electrode mainly composed of a hydrogen storage alloy, it is compared with the case where a metal battery container is used. Then, they found a problem that the self-discharge rate increased when the battery was left in a charged state.

Therefore, even in a sealed battery including a negative electrode mainly composed of a hydrogen storage alloy and a battery container made of synthetic resin, one having a low self-discharge rate is desired as in the case of using a metal battery container. It was

[0008]

In order to solve the above problems, the present invention provides a hermetically sealed battery comprising a negative electrode mainly composed of a hydrogen storage alloy and a battery container made of synthetic resin, the surface of the battery container being Provided is a sealed battery having a non-porous metal layer provided on the.

[0009]

When a synthetic resin battery container is used in a sealed battery having a negative electrode mainly composed of a hydrogen storage alloy,
As a result of investigating the cause of the increase in the self-discharge rate of the battery, the following was found.

That is, when the mass transfer does not occur between the inside and outside of the battery container, the hydrogen partial pressure inside the battery is equal to the equilibrium hydrogen pressure of the hydrogen storage alloy, and the hydrogen storage reaction of the hydrogen storage alloy is suppressed. Since the rate and the rate of the release reaction are equal, they are in an equilibrium state, and self-discharge of the negative electrode accompanied by generation of hydrogen does not occur. In an actual battery, the reaction that oxidizes hydrogen at the positive electrode occurs at a low rate, which consumes hydrogen in the battery and lowers the hydrogen partial pressure below the equilibrium hydrogen pressure. The equilibrium shifts in the direction in which hydrogen is released, causing self-discharge of the negative electrode with the generation of hydrogen. Since this self-discharge is a phenomenon that occurs inside the battery, it occurs regardless of the type of battery container. When a metal battery container is used, the rate at which hydrogen permeates the wall of the battery container is extremely low, so in this case, the self-discharge of the negative electrode accompanied by hydrogen generation is mainly
This is due to the reaction of hydrogen oxidation at the positive electrode.

On the other hand, the permeation rate of hydrogen in the synthetic resin is significantly higher than that in metal. The hydrogen partial pressure in the atmosphere outside the battery container is significantly smaller than the equilibrium hydrogen pressure of the hydrogen storage alloy used for the negative electrode. Therefore, when a synthetic resin battery container is used, the rate at which hydrogen in the battery permeates through the wall surface of the battery container and is lost to the outside of the battery is significantly higher than when a metal battery container is used. As a result, the hydrogen partial pressure in the battery is lowered, and the self-discharge rate of the negative electrode accompanied by the generation of hydrogen is increased.

In the present invention, since the non-porous metal layer is provided on the outer or inner surface of the synthetic resin battery container,
Hydrogen that permeates the battery container made of synthetic resin is blocked by the metal layer having a low hydrogen permeation rate, and as a result, the self-discharge rate of the negative electrode accompanied by hydrogen generation is reduced.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described with reference to the accompanying drawings with reference to the preferred embodiments. [Battery (A) of the present invention] Fig. 1 is a cross-section of a sealed nickel metal hydride storage battery (A) of the present invention, which has a rectangular outer shape and in which positive electrode plates and negative electrode plates are alternately laminated with separators in between. The schematic diagram of a surface is shown.

In FIG. 1, A is a battery case made of an acrylic-styrene copolymer. B is a non-porous metal nickel layer applied to the outer surface of the battery case A by electroless plating. C is a negative electrode hydrogen storage electrode. D is a separator made of a non-woven fabric of fibers of a mixture of polyethylene and sulfonated polystyrene to impart hydrophilicity. E is a sintered nickel hydroxide electrode having a positive electrode.

The battery container A has a thickness of about 2 mm, and the metallic nickel plating layer B has a thickness of about 100 μm.

The total weight of nickel hydroxide contained in the four positive electrode nickel hydroxide electrodes E is 39 per cell.
It is g. Therefore, assuming that nickel hydroxide follows a one-electron reaction, the theoretical capacity of the positive electrode of one battery is about 11
It is Ah. To this electrode was added 0.04 grams of cobalt hydroxide per gram of nickel hydroxide.

The negative electrode plate C was manufactured as follows.

The hydrogen storage alloy has a composition of LmNi in atomic ratio.
The constituent elements were melted in a metallic state in a high-frequency induction furnace in a vacuum so as to be _3.8 Co _0.7 Al _0.5 , cast, and then pulverized. Here, Lm is a lanthanum rich misch metal which is a mixture of rare earth metals containing about 90% by weight of La. This alloy powder was dispersed in an aqueous solution of polyvinyl alcohol that functions as a thickener and a binder to form a paste. Then, this paste was applied to both sides of a nickel-plated iron punching metal, dried, pressed, and cut to manufacture a hydrogen storage electrode.

The weight of the hydrogen storage alloy contained in the five negative plates of one battery was about 53 g. [Battery (a) of the present invention] A battery (a) of the present invention is a non-porous aluminum foil of the same thickness, instead of the non-porous metal nickel plating layer B in the battery (a) of the present invention. Was laminated with a polypropylene and vinylidene chloride resin film by heat welding, and the other structure was the same as the battery (a). [Conventional Battery (C)] The conventional battery (C) was manufactured in the same manner as the battery (A) except that the metal nickel plating layer B of the battery (A) of the present invention was not provided. [Experiment] To these sealed nickel-metal hydride storage batteries, an equal amount of an electrolytic solution of 0.4 M ZnO and 10 g / l LiOH in a 6 M KOH aqueous solution was injected.

The sealed nickel-metal hydride storage battery described above was used at a current of 10 hour rate based on the theoretical capacity of the positive electrode.
After performing the charge for an hour, the battery was charged and discharged twice at a rate of 5 hours.

Next, the discharge capacity before standing was measured under the condition that the battery was charged at a current of 10 hours for 15 hours and discharged at a current of 5 hours until the terminal voltage became 1V. Then, the discharge capacity after standing was measured under the condition that the battery was charged at a current of 10 hours for 15 hours, left for 20 days, and then discharged at a current of 5 hours until the terminal voltage became 1V. These charging and discharging are performed at an ambient temperature of 25 ° C,
The charged battery was left at 40 ° C.

In this test, the capacity retention rate after standing was defined as the discharge capacity after standing with respect to the discharge capacity before standing, and the value of the capacity retention rate of each battery obtained in the above test is shown in Table 1. Show.

[0023]

[Table 1] From Table 1, it is clear that the capacity retention rates of the batteries (a) and (b) of the present invention are remarkably high as compared with the conventional battery (c), and therefore the self-discharge rate is remarkably low.

In the above embodiment, the alkaline storage battery using the sintered nickel hydroxide electrode as the positive electrode is described. However, the electrolytic solution is an alkaline aqueous solution, and the positive electrode is a nickel fiber sintered body or foamed nickel. The same as in the above-mentioned examples when the electrode is filled with nickel oxide, the positive electrode active material is manganese dioxide, silver oxide, or silver peroxide, or when the electrolytic solution is an acidic aqueous solution and the positive electrode active material is lead peroxide. Produces the effect of. However, when the electrolytic solution is acidic, the hydrogen storage alloys of the above examples have low corrosion resistance.
It is desirable to use amorphous alloys with compositions such as those described in US Pat.

Further, in the above-mentioned embodiments, the case where the hydrogen storage alloy of the negative electrode has a specific composition is explained, but the effect of the present invention is that the hydrogen storage alloy in the battery is in equilibrium with the hydrogen storage alloy. Since hydrogen permeates the synthetic resin battery container and is lost to the outside of the battery with a low hydrogen partial pressure, it is suppressed by the metal layer having a slow hydrogen moving speed.
The composition of the hydrogen storage alloy of the negative electrode of the battery, in which the means of the present invention exerts its function and effect, is not limited to that of the above-mentioned embodiment.

Further, in the above embodiment, the case where the nickel electroless plating layer or the aluminum laminating film is used as the non-porous metal layer has been described. However, as the material of the metal layer, similar effects can be obtained when other materials such as chromium and copper are used, and therefore, the material of the metal layer in the present invention is not limited to those described in the embodiments. Further, as a means for providing a non-porous metal layer, a method such as vacuum vapor deposition, electroplating or thermal spraying can be applied.

The site where the non-porous metal layer is provided is
Not only on the outer surface of the battery container, but also on the inner surface, it is possible to obtain the same effects as those of the above-described embodiment. However, in this case, the positive electrode and the negative electrode in the battery,
Insulating means must be provided to prevent short circuits through the metal layer. When the metal layer provided on the inner surface of the battery container is in contact with the electrolytic solution, it is not a metal having poor corrosion resistance to an acid or alkaline electrolytic solution such as aluminum, but nickel is suitable in the alkaline electrolytic solution, for example. Lead is suitable in the acid electrolyte, for example.

[0028]

According to the present invention, there is an effect that self-discharge when a battery in a charged state is left is suppressed.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a sealed nickel-metal hydride storage battery (a) of the present invention, which has a rectangular outer shape and in which positive electrode plates and negative electrode plates are alternately laminated with separators in between.

[Simple explanation of symbols]

 A battery container made of synthetic resin B non-porous metal layer C hydrogen storage electrode D separator E nickel hydroxide electrode

Claims (1)

Claim: What is claimed is: 1. A sealed battery comprising a negative electrode mainly composed of a hydrogen storage alloy and a battery container made of synthetic resin, wherein a non-porous metal layer is provided on the surface of the battery container. A sealed battery characterized in that.