JPH06105613B2 - Method of manufacturing alkaline storage battery - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for manufacturing an alkaline storage battery such as a nickel-cadmium storage battery having a cadmium electrode on the negative electrode, and particularly to a method for manufacturing the negative electrode.

In the battery having the above structure, the utilization factor of the active material in the negative electrode gradually decreases as the charge and discharge cycle progresses,
As a result, there is a problem that the battery capacity is lowered.

This phenomenon is considered to be mainly due to the following reasons.

That is, as the charge / discharge cycle progresses, cadmium hydroxide, which is a discharge product, is generated so as to cover the surface of metal cadmium, which is a charge product, and prevents contact between the metal cadmium and the electrolytic solution, so that a metal that cannot be discharged It is thought to be caused by the accumulation of cadmium.

In order to solve the above problems, conventionally, a polymer paste such as methyl cellulose or polyvinyl alcohol is applied to the surface of the electrode plate to change the crystal form of the cadmium hydroxide, thereby closing the metal cadmium. It is known that the electrolytic solution and the metal cadmium can be easily brought into contact with each other to prevent the decrease in the negative electrode capacity.
For example, as disclosed in JP-A-61-158664, there has been proposed a method in which a polymer aqueous solution is applied to a negative electrode plate to form a polymer film on the surface of the negative electrode plate.

However, in the above-mentioned manufacturing method, the polymer does not penetrate into the pores of the negative electrode plate, so that the polymer paste cannot penetrate into the surface of the active material inside the electrode plate. For this reason, it is not possible to completely prevent the clogging of the metal cadmium and the contact between the metal cadmium and the electrolytic solution may be hindered, which is not sufficient to prevent the decrease in the negative electrode capacity.

Therefore, as shown in JP-A-61-158666, a method of impregnating a negative electrode plate with an aqueous polymer solution under reduced pressure has been proposed.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the above-mentioned production method, the polymer cannot be sufficiently permeated into the pores of the negative electrode plate, and it is still not sufficient to prevent the decrease in negative electrode capacity. In addition, equipment and the like for creating a depressurized state are required separately, and it takes a long time to evacuate to bring the depressurized state. Therefore, there is a problem that the manufacturing cost of the negative electrode plate increases.

In view of these problems, the present invention allows the polymer paste to penetrate into the pores of the negative electrode plate more than ever before,
It is an object of the present invention to provide a method for manufacturing an alkaline storage battery, which can prevent the negative electrode capacity from being reduced with the progress of charge / discharge cycles and can manufacture a negative electrode plate at low cost.

Means for Solving the Problems In order to solve the above problems, the present invention provides a step of holding a low-viscosity solvent in the pores of a sintered cadmium negative electrode plate, and a polymer paste soluble in the solvent. The alkaline storage battery is manufactured by the steps of dissolving the material in the solvent and holding the polymer paste in the pores of the negative electrode plate.

Action As described above, if the structure is such that the low viscosity solvent is first retained in the pores of the sintered cadmium negative electrode plate, even if air is present in the pores, the pores are The solvent can be easily permeated. If the solvent penetrates into the pores, the polymer paste easily dissolves in this solvent. Therefore, even if the polymer paste has high viscosity, the polymer paste should penetrate into the pores. You can Therefore, the polymer paste can be permeated to the surface of the active material inside the electrode plate, and thus the clogging of metal cadmium can be sufficiently prevented. As a result, even when the charging / discharging cycle progresses, the contact between the metal cadmium and the electrolytic solution is not hindered, and the reduction in the negative electrode capacity can be sufficiently prevented.

In addition, in the case of the above configuration, equipment for creating a reduced pressure state and the like are not necessary, and time such as evacuation for reducing the pressure state is also unnecessary, thus significantly reducing the manufacturing cost of the negative electrode plate. be able to.

EXAMPLES The examples of the present invention are described below.

First Embodiment First, a sintered cadmium electrode plate is formed to remove impurities in the electrode plate. Next, this cadmium electrode plate is washed with water and then dried. Then, the cadmium electrode plate is immersed in water to contain water, and then a 1 wt% methylcellulose aqueous solution is applied to the cadmium electrode plate. Then, after drying the cadmium plate, the plate is cut into a size of 200 mm × 33.5 mm. As a result, a negative electrode plate having an electrode plate capacity of 3000 mAh was obtained. Then, a battery was prepared using this negative electrode plate, two sintered nickel positive electrode plates having the same dimensions as the negative electrode plate as a counter electrode of the negative electrode plate, and an aqueous potassium hydroxide solution having a specific gravity of 1.23.

Hereinafter, the battery thus manufactured will be referred to as (A) battery.

[Second Example] A cadmium electrode plate was dipped in a methanol solution so that the cadmium electrode plate contained methanol.
A battery was produced in the same manner as in Example 1 except that a 1 wt% methylcellulose methanol solution was applied to produce the negative electrode.

Hereinafter, the battery thus manufactured is referred to as a (B) battery.

[Third Example] After washing with water after the chemical conversion step, 1 w was obtained without drying.
A battery was manufactured in the same manner as in Example 1 except that a negative electrode was manufactured by applying a t% methylcellulose aqueous solution.

Hereinafter, the battery thus manufactured will be referred to as a (C) battery.

[Comparative example]

A battery was prepared in the same manner as in Example 1 except that the negative electrode was prepared by applying a 1 wt% methylcellulose aqueous solution to the cadmium plate without immersing the cadmium plate in water.

Hereinafter, the battery thus manufactured will be referred to as a (D) battery.

A battery was produced in the same manner as in Example 1 except that the negative electrode was produced without performing the steps subsequent to the step of immersing the cadmium electrode plate in water.

Hereinafter, the battery thus manufactured will be referred to as (E) battery.

Here, the cycle characteristics of the batteries (A) to (C) of the present invention and the batteries (D) and (E) of the comparative examples were examined. The results are shown in FIG. In addition, the experimental condition is that the current value of 3/10 of the electrode plate capacity is filled for 4.8 hours, then 1/1 of the electrode plate capacity is filled.
The discharge was performed at the current value of.

As is clear from FIG. 1, the battery capacity of the (D) battery and the (E) battery of the comparative example drastically decreased as the charge / discharge cycle progressed, and after 300 cycles, (D)
It is recognized that the battery capacity decreases to about 2200 mAh for the battery, and the battery capacity decreases to about 1600 mAh for the (E) battery. On the other hand, in the batteries (A) to (C) of the present invention, the battery capacity did not decrease so much even if the charge and discharge cycle proceeded, and
It is recognized that the battery capacities of the (A) battery and the (B) battery are maintained at approximately 2800 mAh and the (C) battery is maintained at approximately 2900 mAh even after the lapse of cycles. As a result, it can be seen that the batteries (A) to (C) of the present invention have dramatically improved cycle characteristics as compared with the batteries (D) and (E) of Comparative Examples.

It is noted that the battery (C) of the present invention has a slightly higher initial battery capacity and battery capacity after 300 cycles than the same batteries (A) and (B) of the present invention. . It is considered that this is due to the following reasons.

That is, since the (C) battery omits the drying process after the chemical conversion process, the number of times of drying is one less than that in the manufacturing processes of the (A) battery and the (B) battery. Therefore, it is considered that since the oxidation of cadmium in the negative electrode can be further prevented, the activity of the cadmium active material is higher than that of the batteries (A) and (B).

Further, in the case of the battery manufacturing method (C) of the present invention, since the 1 wt% aqueous solution of methyl cellulose is applied in an undried state after the chemical conversion step and the water washing step, the water washing step and the application of the methyl cellulose aqueous solution are performed. It is possible to make it continuous with the process. Therefore, these two steps can be performed on the same line, and the number of production steps can be reduced, so that the manufacturing cost of the alkaline storage battery can be further reduced.

Further, although all of the above-mentioned examples have a water washing step, the effects of the present invention can be obtained even if this water washing step is omitted. In this case, the chemical liquid during the chemical conversion step serves as a solvent for the polymer paste.

In addition, the present invention also requires a drying step after forming the polymer film, but in this case, the cadmium active material is sufficiently covered with the polymer film, so that the oxidation of the cadmium active material is minute.

As described above, in the present invention, after the low viscosity solvent is held in the pores of the sintered cadmium negative electrode plate, the high viscosity polymer paste is applied to the surface of the negative electrode plate. Since the polymeric paste is dissolved in the low-viscosity solvent, the polymeric paste can be easily permeated into the pores even when air is present in the pores. Therefore, the polymer paste can be permeated to the surface of the active material inside the electrode plate, and thus the clogging of metal cadmium can be sufficiently prevented. As a result, even if the charge / discharge cycle progresses, the contact between the metal cadmium and the electrolytic solution is not hindered, and it is possible to prevent the reduction of the negative electrode capacity, so that the performance of the alkaline storage battery is leapt. The effect is that it can be improved.

In addition, since there is no need for equipment or the like for creating a reduced pressure state, and the time for vacuuming or the like for achieving a reduced pressure state is also unnecessary, the manufacturing cost of the negative electrode plate can be significantly reduced. Can play.

[Brief description of drawings]

FIG. 1 is a graph showing cycle characteristics of the batteries (A) to (C) of the present invention and the batteries (D) and (E) of Comparative Examples.

Claims (2)

[Claims] 1. A step of holding a low-viscosity solvent in the pores of a sintered cadmium negative electrode plate, and dissolving a high-molecular-weight solvent that is soluble in the solvent in the solvent to obtain a void in the negative electrode plate. A method for manufacturing an alkaline storage battery, comprising a step of holding a polymer paste in a hole. 2. The step of retaining the low-viscosity solvent comprises:
The method for producing an alkaline storage battery according to claim (1), wherein the cleaning liquid used when cleaning the sintered cadmium negative electrode plate is carried out by holding the cleaning liquid as the low-viscosity solvent on the negative electrode plate.