JPH0713896B2 - Sealed nickel cadmium battery - Google Patents

Description

TECHNICAL FIELD The present invention relates to an improvement of a sealed nickel-cadmium storage battery, and more particularly to a battery constituted by filling a porous metal support with an active material. Is.

2. Description of the Related Art A sealed nickel-cadmium storage battery consists of a positive electrode mainly composed of nickel hydroxide, a negative electrode mainly composed of cadmium hydroxide and a separator separating positive and negative electrodes from each other, and potassium hydroxide and sodium hydroxide as electrolytes. , And an alkaline aqueous solution such as lithium hydroxide.

As the negative electrode, a cadmium electrode such as a sintered type or a paste type is generally used, and as the positive electrode, a nickel hydroxide serving as a positive electrode active material is formed on a porous nickel sintered substrate by a method such as an electrolytic method or a chemical impregnation method. , Cobalt hydroxide, etc. are used. In addition, recently, a nickel positive electrode having a high capacity has been proposed in which a foamed metal having a three-dimensional network structure is used and is filled with an active material paste mainly containing nickel hydroxide.

The conventional active material filling process for a sintered nickel positive electrode requires a number of processes such as a chemical impregnation process such as an impregnation process, an alkali treatment process, a water washing process, and a drying process, in order to obtain a high capacity positive electrode. However, it is necessary to repeat these steps several times, which is very complicated.

On the other hand, the method using foam metal (porosity 90-95%)
By selecting one with a large pore size, it is possible to directly fill the substrate with the paste-like active material, and it is possible to manufacture a nickel positive electrode with a high capacity by a simple process of performing pressure processing after filling. . Regarding the characteristics of the positive electrode plate, in terms of capacity, the capacity density per unit volume of the conventional sintering type positive electrode plate is about 350 to 450 mAh / cc, whereas
A high capacity of about 520 mAh / cc is obtained, and the discharge characteristics at large currents are similar to those of the sintered type.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, the nickel positive electrode using a foam metal has a high porosity of the foam metal and can have a high capacity, but on the other hand, it has a problem of low strength as an electrode plate due to its high porosity. is there.

This is especially a problem at the time of winding when forming the battery group.

That is, since the electrode strength is low, there is a drawback that the electrode plate is likely to be broken during winding. As a method to prevent this, a method has been proposed in which a reinforcing body is put in foam metal (Actual No. Sho 53-62630) to improve the strength of the electrode plate, but in terms of an increase in the number of steps or cost. , There was a problem.

MEANS FOR SOLVING THE PROBLEMS The present invention uses a foamed metal having high porosity on one side and low porosity on the other side. Therefore, the above problem is solved by winding it.

Action The filling of the foam metal with the active material is greatly influenced by the porosity of the foam metal. Those having a high porosity have a high packing property, and those having a low porosity have a low packing property. Therefore, when a foam metal having a high-porosity surface and a low-porosity surface is filled with an active material, the high-porosity surface is largely filled with the active material, and the low-porosity surface is less filled. It

FIG. 1A is a schematic cross-sectional view of a conventional foam metal having a uniform porosity, and FIG. 1B is a high porosity on one side used in the present invention.
The other side shows a foamed metal with low porosity. FIG. 2 is a schematic sectional view of the electrode showing the distribution of the active material when these A and B are filled with the active material. As described above, when the foamed metal used in the present invention is filled with the active material, the result shown in FIG.
As shown in, the surface b ₂ of the metal foam having a high porosity has a high active material density, and the surface b _{1 having} a low porosity has a low active material density. Further, when the conventional foam metal A shown in FIG. 1A has a uniform porosity, the active material density is uniform on both surfaces a ₁ and a ₂ as shown in FIG. 2A. In the case of a conventional electrode having a uniform active material density by pressure-processing the electrode filled with the active material in this way, the surface-direction force exerted on the surface when pressure is applied is x ₁ , As in x ₂ , the a ₁ surface and the a ₂ surface are equivalent. However, the second active material density varies depending on the surface
FIG case of B, the force of pressurization is small y ₁ towards the active material less dense surface b _1, it is greater towards the active material dense surface b ₂
y ₂ . Therefore, when such an electrode is wound in forming a battery group, if the electrode B according to the present invention is wound with the surface b ₂ of the metal foam having a high porosity and a high active material density as the outer side, the electrode shown in FIG. As described above, since the electrode is easily bent with the b ₂ surface as the outer side, winding is facilitated and the degree of electrode breakage is reduced. On the other hand, in the conventional electrode, as shown in FIG. 3A, since the electrode plate has no directional property of bending, the degree of electrode bending does not change even if the electrode is wound in either direction.

Examples Examples of the present invention will be described below.

The foamed metal used for the nickel positive electrode is formed by nickel-plating polyurethane foam coated with carbon, which normally acts as a conductive material, and then by treating it at high temperature to quench the polyurethane foam, leaving a foamed nickel skeleton. To manufacture.

In the present invention, the anodes are usually arranged on both sides of the polyurethane foam coated with carbon to perform nickel plating, whereas the anodes are arranged only on one side and the carbon coating foamed polyurethane is subjected to nickel plating. As a result, nickel plating progresses from the surface on which the anode is arranged, so the surface on which the anode is arranged has a large amount of nickel plating (low porosity) and the opposite surface has a small amount of nickel plating (high porosity). Become. In this way
We prepared a metal foam with high porosity on one side and low porosity on the other side.

The foamed metal of the present invention produced in this manner and a conventionally used foamed metal are filled with an active material mainly composed of nickel hydroxide, subjected to pressure processing, and then cut into a predetermined size, and lead welding, etc. After performing the single plate processing of No. 3, the grouping was performed by the winding method as described above, the SC size sealed nickel cadmium storage battery was assembled, and the battery characteristics were compared. Regarding the battery characteristics, in order to detect the breakage of the electrode, the standard capacity was compared and the high rate discharge characteristics were compared.
The high rate discharge was compared by the ratio of the discharge capacity equivalent to 0.2C and the discharge capacity equivalent to 3C. If the electrode is broken,
Depending on the degree, there are those with a small 0.2C capacity and those with a high rate discharge capacity of about 3C. FIG. 4 is a comparison of the standard capacity (0.2 C discharge capacity) of the battery A manufactured by the conventional method and the battery B of the present invention. In FIG. 4A, the capacity decrease due to the breakage of the electrode is observed, whereas in B, it is within the designed range. Similarly, FIG. 5 is a diagram showing a comparison of 3C discharge capacity ratios. In the conventional device shown in FIG. 5A, the discharge capacity ratio is thought to decrease due to the breakage of the electrodes, whereas in the present invention B, it is not observed.

EFFECTS OF THE INVENTION As described above, according to the present invention, even if the number of steps is not increased, since the strength of the electrode, which is the conventional problem when using the foam metal, is low, the electrode is damaged during winding. It becomes possible to manufacture a sealed nickel cadmium storage battery with high capacity and high reliability.

BRIEF DESCRIPTION OF THE DRAWINGS FIGS. 1A and 1B are schematic sectional views of a conventional foam metal for a battery electrode and a foam metal used in the present invention, and FIGS. The figure which shows comparison, Figure 3A and B are the figure which shows the directionality of the electrode bending after the electrode pressure processing similarly, Figure 4 is the figure which shows the comparison of the discharge capacity distribution in 0.2C , Fifth
The figure shows the distribution of the discharge capacity ratio at 3C.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Shingo Tsuda 1006 Kadoma, Kadoma, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (72) Minor Yamaga 1006 Kadoma, Kadoma City, Osaka Matsuda Denki Sangyo

Claims (1)

[Claims] 1. A nickel positive electrode obtained by filling a foamed metal having a continuous three-dimensional network structure with an active material mainly composed of nickel hydroxide and pressurizing the foamed metal. One side of the foamed metal has high porosity and the other side. Is a low-porosity, spirally wound nickel-cadmium storage battery with the high-porosity surface facing outward.