JPH06295727A - Sealed alkaline storage battery - Google Patents

Abstract

PURPOSE:To provide an alkaline storage battery which is excellent in the cycle service life and has a high industrial value. CONSTITUTION:An electrode group is constituted through a separator between a negative electrode and a paste type positive electrode where paste formed by kneading an active material mainly composed of nickel hydroxide, a thickener and water is filled in a metallic porous body, and this electrode group is charged in a battery container. In this storage battery, polyvinyl alcohol is added to both poles of the positive electrode and the negative electrode. This negative electrode may be a paste type negative electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed alkaline storage battery such as a nickel-cadmium storage battery or a nickel-hydrogen storage battery.

[0002]

2. Description of the Related Art Conventional sealed alkaline storage batteries include nickel-cadmium storage batteries and nickel-hydrogen storage batteries, which have recently received attention. This type of storage battery has an electrode group in which a positive electrode and a negative electrode are spirally wound via a separator, and a cylindrical sealed alkaline storage battery in which this electrode group is loaded in a battery container, or a positive electrode and a negative electrode are separated by a separator. There is an angle-sealed Alcal storage battery in which a battery container is loaded with the electrode group by stacking the electrode groups in a stacked manner via the. In particular, in recent years, the paste method, which is very advantageous in promoting a higher capacity of a sealed alkaline storage battery, is becoming the mainstream of the manufacturing method of the positive electrode and the negative electrode than the conventional sintering method.

[0003]

However, in comparison with a storage battery composed of a sintered electrode, a storage battery composed of a paste type electrode is still not suitable as a sintered type electrode in terms of reliability of cycle life. The problem that it does not reach is left. This is because it is difficult to maintain the electrode capacity for a long period of time because the paste type electrode has a weaker physical strength than the sintered type electrode. This is because the electrolyte taken in causes an apparent liquid depletion and eventually the cycle life of the storage battery is exhausted.

The present invention has been made in consideration of the above-mentioned problems, and provides a sealed alkaline storage battery of high industrial value with excellent cycle life in the conventional sealed alkaline storage battery and high capacity type sealed alkaline storage battery. With the goal.

[0005]

According to the present invention, a negative electrode and a paste type positive electrode having a metal porous body filled with a paste obtained by kneading an active material mainly containing nickel hydroxide, a thickener and water are provided. A sealed alkaline storage battery, which comprises an electrode group via a separator and which is loaded into a battery container, wherein polyvinyl alcohol is added to both the positive electrode and the negative electrode. . Also,
The negative electrode may be a paste type negative electrode.

[0006]

[Function] There have been several proposals to add polyvinyl alcohol as a binder to the negative electrode, but all of them have only been able to improve the physical strength of the electrode, and a sealed alkaline It has not been possible to sufficiently improve the cycle life of the storage battery. It is considered that this is because it was not possible to prevent the electrolytic solution from being taken into the separator due to the swelling of the paste-type positive electrode due to charge / discharge.

Further, when polyvinyl alcohol is added only to the paste type positive electrode, the physical strength of the paste type negative electrode is not sufficient, so that the negative electrode plate active material falls off with charge and discharge, and the electrode capacity decreases. As a result, the cycle life of the sealed alkaline storage battery is exhausted. However, by adding polyvinyl alcohol, which is less likely to swell in the alkaline electrolyte, to both the positive electrode and the negative electrode at the same time, it is possible to prevent the exhaustion of the electrolytic solution in the separator due to the uptake of the electrolytic solution for a long period of time. Long cycle life.

[0008]

The present invention will be described in detail below with reference to examples. Example 1 90 parts by weight of nickel hydroxide powder, 10 parts by weight of cobalt oxide, carboxymethyl cellulose as a thickener, and polyvinyl alcohol as a binder were kneaded together with water to form a paste, which had a porosity of 95%. The paste type nickel positive electrode a used in the present invention was obtained by filling a nickel-plated metal porous body having an average pore diameter of 200 μm, drying and molding.

An active material paste obtained by kneading 90 parts by weight of cadmium oxide, 10 parts by weight of nickel powder and fibers with an ethylene glycol solution of carboxymethyl cellulose and an ethylene glycol solution of polyvinyl alcohol was prepared as a current collector. Was coated on a nickel-plated punched substrate and dried at about 120 ° C. for 2 hours to obtain a cadmium oxide coated plate. Next, a mixture of metal cadmium, nickel powder, carboxymethyl cellulose, polyvinyl alcohol, fluororesin dispersion and ion-exchanged water was kneaded to obtain a metal cadmium paste.
This paste was applied to both sides of the above cadmium oxide coated plate and dried at about 150 ° C. to obtain a cadmium negative electrode b used in the present invention.

On the other hand, for comparison with the present invention, only polyvinyl alcohol was not added, and only the pasted nickel positive electrode c prepared in the same manner as the pasted nickel positive electrode a used in the present invention and polyvinyl alcohol were added. A paste type cadmium negative electrode d was prepared in the same manner as the paste type cadmium negative electrode b used in the present invention.

Here, a battery A according to the present invention using a paste type nickel positive electrode a and a paste type cadmium negative electrode b,
As a comparative example, a battery B prepared by using a paste type nickel positive electrode c without adding polyvinyl alcohol and a paste type cadmium negative electrode b, and a paste type nickel positive electrode a and a paste type cadmium negative electrode d without adding polyvinyl alcohol were prepared. Electrode C used, and paste type nickel positive electrode c without addition of polyvinyl alcohol
A battery D was prepared using the paste type cadmium negative electrode d to which polyvinyl alcohol was not added.

FIG. 1 shows changes in battery capacity and internal resistance of each battery with respect to cycles when these batteries were charged and discharged. Battery A has the longest cycle life and shows a stable capacity for a long time, and the internal resistance does not change so much. However, in batteries B and C in which polyvinyl alcohol was added to only one of the electrodes, the capacity decreased as the cycle progressed. In particular, it is considered that the internal resistance of the battery B is gradually increased and the liquid in the battery is dry. In Battery D, the capacity decreased without showing a stable capacity even once, and at the same time, the internal resistance also increased.

The thickness of the positive electrode portion was measured from the cross section of each battery after 300 cycles of charging / discharging, and the positive electrode thickness swelling degree compared with the initial thickness at the time of electrode preparation is shown in Table 1.
When the paste type nickel positive electrodes of the batteries B and D are significantly swollen in Table 1 and the internal resistance is increased in FIG. 1, when the polyvinyl alcohol as the binder is not added to the paste type nickel positive electrodes, It is considered that the electrode itself swelled with the charging / discharging cycle to take in the electrolytic solution and the liquid in the separator became dry.

On the other hand, when polyvinyl alcohol, which is a binder, is added to the paste type nickel positive electrode, at least the separator is used because the degree of swelling of the electrode is low and the change in internal resistance with charge / discharge cycles is gradual. The liquid inside is considered to be retained. In the case of the battery C whose capacity has decreased nevertheless, it is considered that the capacity was decreased due to the loss of the active material of the paste-type cadmium negative electrode, which resulted in the negative electrode regulation.

[0015]

[Table 1]

Example 2 The results of the same test as in Example 1 using the nickel-hydrogen storage alloy negative electrode are shown in FIG. 2 and Table 2. It has been found that the effects of the present invention are exactly the same.

[0017]

[Table 2]

From the above, it can be easily predicted that the present invention can be similarly applied to not only the cylindrical sealed alkaline storage battery but also the angular sealed alkaline storage battery.

[0019]

As described above, according to the present invention, it is possible to supply a conventional sealed alkaline storage battery or a high-capacity sealed alkaline storage battery having a high cycle value and a high industrial value. It has become possible.

[Brief description of drawings]

FIG. 1 is a diagram showing a cycle change of a capacity retention rate and an internal resistance of a nickel-cadmium storage battery.

FIG. 2 is a diagram showing a cycle change of a capacity maintenance ratio and an internal resistance of a nickel-hydrogen storage battery.

Claims (2)

[Claims] 1. An electrode group is provided with a separator between a negative electrode and a paste type positive electrode in which a paste obtained by kneading an active material mainly containing nickel hydroxide, a thickener and water is filled in a metal porous body. A sealed alkaline storage battery comprising the electrode group in a battery container, wherein polyvinyl alcohol is added to both the positive electrode and the negative electrode of the sealed alkaline storage battery. 2. The sealed alkaline storage battery according to claim 1, wherein the negative electrode is a paste type negative electrode.