JPS61138472A - Alkaline battery - Google Patents

Abstract

PURPOSE:To improve large current discharge characteristic while maintaining good quick charging characteristic by employing a paste cadmium negative pole and such electrolyte as mainly composed of potassium hydroxide of specific concentration. CONSTITUTION:Paste cadmium negative pole applied with porous fluororesin layer is provided where the negative pole active substance is mainly composed of cadmium oxide and the filling density of active substance is brought to 1,100-1,400mAh/cc through pressurization prior to negative electrolysis which is executed to achieve metal cadmium of 400-600mAg/cc, while electrolyte mainly composed of potassium hydroxide having concentration of 6.5-8.0 normality is provided. Consequently, when employing metal cadmium of 400-600mAg/ cc per unit volume of negative pole, the conductivity of negative pole active substance is improved through increase of the concentration of metal cadmium while the inner resistance is reduced to improve larger current discharge characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to improving the large current discharge characteristics of a negative electrode gas absorption type sealed alkaline storage battery using a paste type negative electrode provided with a fluororesin microporous layer. be.

Conventional technology Conventionally, this type of sealed alkaline storage battery was developed in Japanese Patent Application Laid-open No. 57
As described in Publication No. 53068, a paste-type negative electrode with a fluororesin microporous layer provided on the surface is known, and the electrolyte mainly contains potassium hydroxide with a concentration of 5.5 to 7.0N. It was intended to be.

Problems to be Solved by the Invention In such conventional technology, the reaction area is increased due to high porosity, and the gas absorption properties are significantly improved due to the increased water repellency due to the fluororesin microporous layer. . However, on the other hand, there were problems such as an increase in internal resistance and a decrease in large current discharge characteristics.

In the past, there have been examples in which large current discharge characteristics have been slightly improved by using an electrolytic solution containing high concentration potassium hydroxide as a main component, but this has not been fully satisfactory. That is, since the resistance at the negative electrode was greater than that of the conductive dust in the electrolyte, the effect of the conductive dust in the electrolyte was small.

The present invention solves these problems and improves the large current discharge characteristics without impairing the gas absorption characteristics of the negative electrode.

Means for Solving the Problem In order to solve this problem, the present invention includes a paste-type cadmium negative electrode having a microporous layer of fluororesin on its surface.
This negative electrode active material is mainly composed of cadmium oxide, and the packing density of the active material can be increased to 1 by pressurizing it before negative electrolysis.
100 to 1400 mAh/cc, and is electrolyzed negatively so that metal cadmium is 400 to 600 mAh/cc, and the main components are this negative electrode and potassium hydroxide with a concentration of 6.5 to 8.0 normal. It is equipped with an electrolyte.

Effect When using this method, when the metal cadmium per unit volume of the negative electrode is set to 400-600mAh/cc, compared to the conventional method,
As the metal cadmium concentration increases, the conductive dust in the negative electrode active material layer improves, reducing the internal resistance as shown in Figure 1.
This improves large current discharge characteristics.

In order to increase the amount of metal cadmium while maintaining the amount of cadmium oxide after negative electrolysis, it is necessary to increase the packing density by applying pressure before negative electrolysis.

Pressurization lowers the porosity and reduces the reaction area for oxygen gas absorption, but because the proportion of metal cadmium, which is a reactant, increases, the deterioration of the oxygen gas absorption capacity is avoided, as shown in Figure 2. I found out something.

Furthermore, when using the above-mentioned negative electrode to construct a sealed alkaline storage battery equipped with an electrolyte mainly composed of potassium hydroxide with a concentration of 6.5 to 8.0 normal, compared to the conventional negative electrode, a large current discharge It was also found that the properties were significantly improved.

The reason why the synergistic effect is exhibited as described above is thought to be as follows. In other words, as shown in Figure 4, it is known that the conductive dust in potassium hydroxide aqueous solution reaches its maximum when the concentration is around 7.2N, but in the conventional negative electrode, the absolute concentration of metal cadmium is small. Therefore, the internal resistance of the electrode plate itself was large, and this became the rate-limiting reaction during large current discharge, making the electrolyte less effective. Compared to this, in the negative electrode according to the present invention, since the resistance of the negative electrode is reduced,
Conductive dust in the electrolytic solution becomes rate-determining during large current discharge, and the combination of the negative electrode of the present invention and the electrolytic solution with high conductive dust exhibits a synergistic effect and improves the large current discharge characteristics.

Examples In the following, examples of the present invention will be described using a cylindrical sealed nickel
Cadmium alkaline storage battery (SC size).

The nominal capacity (1200mAh) will be explained in detail while comparing with the conventional example.

First, 100 parts by weight of cadmium oxide powder, 0.5 parts by weight of synthetic resin single fibers, 0.75 parts by weight of polyvinyl alcohol dissolved in 30 parts by weight of ethylene glycol were kneaded to form a paste, and this was mixed into a paste with a thickness of 100 μm. It is applied to both sides of a perforated iron plate made of nickel plated iron with a thickness of 100°C, and then dried at about 110°C. Next, this negative electrode was
After cutting into a size of 205 mm x 205 mm, metal cadmium was heated at 250 to 450 mAh/in a potassium hydroxide aqueous solution.
ccI! : After negative electrolysis, wash with water and dry.

Next, it is immersed in 5 layers of fluororesin suspension for 30 minutes and then dried to form a fluororesin microporous layer. The packing density at this time is
The negative electrode obtained in this way is a conventional product.

Next, as in the case of the conventional product, after applying and drying the paste, the filling density is 1100 to 14oOmAh/cc.
It is then pressure-molded to give a metal cadmium content of 400 to 600 mAh/cc (porosity of about 40%), electrolyzed negatively, washed with water and dried, and then a fluororesin microporous layer is provided on the surface. The negative electrode thus obtained is the product of the present invention.

A separator made of polyamide nonwoven fabric is interposed between the negative electrode and the sintered positive electrode, and the electrode plate is wound in a spiral shape. After inserting this electrode plate group into a battery container, an electrolyte containing 7N potassium hydroxide as its main component is released. The quantity was controlled to be so small that no liquid was produced, and then the caps were sealed to obtain 16 types of sealed alkaline storage batteries as shown in Table 1.

Table 1 Figure 1 shows the relationship between metallic cadmium and internal resistor after charging at 120mAX for 15 hours at 20'C. In FIG. 1, the conventional negative electrode B is a prototype/165-8, and the negative electrode A of the present invention is a prototype/1613-16. As shown in Figure 1, as the metal cadmium per volume increases,
Internal resistance decreases. This is because metal cadmium becomes a conductive material and increases the conductivity of the active material. When the metal cadmium is at least 400 mAh/cc, the internal resistance is stable and better than the conventional one.

FIG. 2 shows the behavior of the internal pressure of the battery at 20° C. during charging at 1200 mA for 3 hours. In FIG. 2, the conventional negative electrode B is a prototype/16.1 to 4, and the negative electrode A of the present invention is:
Prototype/16.9-12. As shown in Figure 2,
.

In the negative electrode A of the present invention in which the amount of metal cadmium per volume is increased, it is possible to obtain good gas absorption characteristics similar to the conventional negative electrode B even at a high packing density.

Figure 3 shows 1 200mA at 20'C as in Figure 2.
The behavior of the internal pressure of the battery during charging for ×3 hours is shown. In FIG. 3, the conventional negative electrode B is the prototype A65-8, and the negative electrode A of the present invention is the prototype A63-16. As shown in Fig. 3, in the conventional negative electrode BK, the amount of metal cadmium was 450
When mA h/cc c f exceeds 600 mAh/cc, hydrogen gas is generated, but in the negative electrode A of the present invention, hydrogen is generated and the internal pressure increases from the time when the voltage exceeds 600 mAh/cc.

In the negative electrode A according to the present invention, the amount of metal cadmium is 9.
The reason why hydrogen is not generated until \- is 600 mAh/cc is because the pressure applied before negative electrolysis increases the packing density and secures an uncharged area. In the negative electrode A of the present invention, hydrogen is similarly generated when the packing density is less than 1100 mAh/cc.

From the above results, in the negative electrode A according to the present invention, the large current discharge characteristics are improved without deteriorating the gas absorption characteristics when the packing density is in the range of 1100 to 1400 mAh/cc and the metal cadmium is in the range of 400 to 600 mAh.

Next, as shown in Table 2, eight types of sealed alkaline storage batteries were constructed by combining negative electrodes and electrolytes.

Table 2 10/7 In Table 2, as the conventional negative electrode B, the negative electrode of Prototype/163 was used, and as the negative electrode A of the present invention, the negative electrode of Prototype/1611 was used. Moreover, 0.5 N of sodium hydroxide was added to the electrolytic solution as an additive.

FIG. 4 shows the discharge efficiency (12A discharge capacity/240 mA discharge capacity) at 12A discharge at an ambient temperature of 20'C. In FIG. 4, D indicates the prototype batteries A to II, and C indicates the prototype batteries H to F.

As shown in FIG. 4, the discharge efficiency reaches its maximum value when the potassium hydroxide concentration is 6.5 to 7.5 normal.

This is because, as shown in FIG. 6, the electrical resistance of potassium hydroxide at 20'C is the lowest near 7.2 normal. However, in batteries using conventional negative electrodes, the effect of electrolyte concentration is about 5%, whereas in Battery C using the negative electrode of the present invention, the effect is significantly improved to about 10%. This is due to the synergistic effect of the negative electrode of the present invention, which has a low internal resistance, and the electrolytic solution, which has a high conductivity. The above effect is exhibited when the potassium hydroxide concentration is 6.
The range is 611, . . . , 8 stipulations.

In Figure 6, at an ambient temperature of 20'C. The internal pressure behavior during 1.2A rapid charging is shown. In FIG. 6, C is a conventional battery, and G is a battery according to the present invention.

FIG. 7 shows the voltage behavior during 12A discharge at an ambient temperature of 20'C. In FIG. 7, C is a conventional battery, and G is a battery of the present invention.

Effects of the Invention As described above, according to the present invention, it is possible to obtain the effect of improving large current discharge characteristics while maintaining good rapid charging characteristics.

[Brief explanation of the drawing]

Figure 1 is a diagram showing the relationship between the amount of metallic cadmium and internal resistance in a cadmium negative electrode, Figure 2 is a diagram showing the relationship between the negative electrode active material packing density and battery internal pressure, and Figure 3 is a diagram showing the relationship between the amount of metallic cadmium and internal battery pressure. 4 is a characteristic diagram showing the relationship between potassium hydroxide concentration and discharge capacity ratio, FIG. 5 is a diagram showing the relationship between potassium hydroxide concentration and electrical resistance, and FIG. 6 is a characteristic diagram showing the relationship between potassium hydroxide concentration and electric resistance. FIG. 7 is a diagram showing the relationship between charging time and battery internal pressure in the embodiment of the present invention, and FIG. 7 is a diagram showing the discharge characteristics in the embodiment of the present invention. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 4
Tsunaga is 7 noumu, -((L';i>Fig.

Claims (1)

[Claims] It has a paste-type cadmium negative electrode with a microporous layer of fluororesin on its surface and an alkaline electrolyte, and the active material of the negative electrode is mainly cadmium oxide, and the pressure is applied before the negative electrolysis. The active material packing density is 1100-140.
0mAh/cc, and metal cadmium is 400mAh/cc.
An alkaline storage battery that undergoes negative electrolysis to achieve ~600 mAh/cc, and the alkaline electrolyte is an aqueous solution containing potassium hydroxide as a main component with a concentration of 6.5 to 8.0 normal.