JPH0218548B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a battery electrode, which is composed of a sponge-like porous metal material having three-dimensionally continuous voids as a substrate, and filled with active material powder in the form of a paste. This is to improve the connection part. Currently, the manufacturing methods for battery electrodes are (1)
(2) A method of compressing or coating a powder mainly composed of active materials using a core metal such as a perforated plate, screen, or grid as a support; (3) A method of compacting a powder mainly composed of active materials; The following methods have been adopted: filling a metal bag or tube with holes with a powder mainly consisting of an active material, and (4) filling a sintered substrate with an active material. Among these methods, (1) and (2) are mainly used for primary batteries, and (2), (3), and (4) are mainly used for secondary batteries. (1) compared to (2),
The main reason for (3) and (4) is that the physical strength of the electrode is relatively large. Among these methods, methods (3) and (4) have particularly high physical strength and are adopted for highly reliable batteries. Among them, method (4) is relatively expensive, but the electrode has excellent electrochemical properties. On the other hand, sponge-like porous metal bodies have recently been commercially available as equivalent to core metals or sintered substrates. Therefore, various proposals have been made regarding electrodes that use this as a substrate and fill it with active material powder. Because the sponge-like porous metal material has extremely high porosity, this electrode can be packed more densely than at least the method (4), and the pore diameter of the porous material can be freely selected, making it highly active. The manufacturing method is similar to methods (2) and (3) because it can be directly filled with powder, which is mainly composed of substances.
It has the potential to be extremely simple. Furthermore, since the electrode properties have a structure in which a three-dimensionally extending lattice surrounds the active material layer, it is expected that the electrode properties will be close to the current best electrode properties (4). In an electrode using a sponge metal porous material as a substrate, in order to achieve high density packing, for example, 500 mAh/cc or more in the case of nickel hydroxide, after filling the inside of the substrate with active material powder, such as nickel hydroxide, It is necessary to apply an extremely large pressure of approximately 700 kg/cm ² or more. Therefore, especially in the case of electrodes having a large area, the pressurizing device becomes a problem. Regarding this pressurization, according to a roll press in which the substrate filled with active material is sandwiched between a pair of rollers and continuously pressurized, the pressurized surface is close to line contact, so it is possible to apply continuous pressure with a relatively small device. is possible. Observing the deformation of the electrode due to this operation, we find that
When the roller surface is provided with minute irregularities, the extension of the electrode in the traveling direction is smaller than when using a roller with a flat surface, but it is impossible to completely eliminate the extension of the electrode. This elongation of the electrode causes cracks to form in the pressure-compressed portion of the substrate, which is formed as the welded portion of the lead terminal prior to filling with the active material. In other words, since the metal density of a sponge-like porous metal material is low, it is difficult to connect a lead plate by spot welding, etc. Therefore, before filling the active material, the substrate is compressed as a lead connection part to reduce the metal density. A method of forming a high part is convenient. However, the pressure operation after filling the active material causes elongation in the active material filled part, whereas the lead connection part is already highly compressed and has no room for elongation, so the lead connection part Cracks occur irregularly in the lead, resulting in inconveniences such as not being able to secure the necessary area for the lead connection portion, or detachment from the electrode after the lead connection. This pattern will be explained with reference to FIGS. 1 to 3. 1 is a substrate made of a long band-shaped sponge-like porous metal body, 2
is a pressure compression section provided in a band shape in the longitudinal direction at the center. After filling the active material in this state, roller pressing is performed. Figure 2 shows the state before pressing, and Figure 3 shows the state after pressing. Due to the pressing of the active material filled part 3, a tensile force in the longitudinal direction acts on the compressed part 2, as shown by 4. This will result in irregular cracks. The continuously roll-pressed substrate is cut in a direction perpendicular to the longitudinal direction so as to be separated at the center of the compressed part 2 in FIG. 1, and processed into an electrode plate including at least one compressed part. . Then, a lead is welded to the compressed portion to form a battery electrode plate. In this case, as described above, if irregular cracks are present in the compressed portion, problems such as the lead coming off from the electrode during lead welding will occur. The present invention eliminates the above-mentioned drawbacks and provides a method for providing a lead connection portion that has the necessary area as a lead connection portion and is free from cracks. That is, a long substrate made of a sponge-like metal porous material is provided with a band-shaped pressurized compression part along its longitudinal direction, and a crack or notch is forcibly provided in advance approximately in the center of this compression part, or It is intended to provide an uncompressed portion that allows elongation but is easily determined. This uncompressed part is created when the compressed part is formed, but cracks and notches can be created at the same time as the compression.
Moreover, it is sufficient if it is before the roller press. Hereinafter, the present invention will be explained in more detail with reference to Examples. Figures 4 and 5 show examples in which a crack 5 is provided so as to divide the compressed part 2 into two parts, front and rear. In this way, when the substrate filled with the active material is pressed by a pair of rolls whose axes are perpendicular to the longitudinal direction of the substrate 1, the active material filled portion 3 will extend in the longitudinal direction of the substrate, and accordingly. Even if a tensile force is applied to the compressed part 2, the crack 5 only spreads back and forth, and the compressed part 2 before and after it only spreads.
No cracks are generated in a and 2b. After this roller press, the electrode plates are cut into individual electrode plates at the positions indicated by the dashed-dotted lines in FIG. Each electrode plate obtained in this way has the compressed portion 2a divided into two parts.
Or 2b remains, so a lead plate is spot welded there and wound in a direction perpendicular to the longitudinal direction of the substrate 1 to form an electrode plate group. In addition, there are two types of sponge-like metal porous bodies: those whose spaces are spherical and those whose spaces are approximately spindle-shaped.For electrode plates that are wound in a spiral, it is best to align the winding direction with the minor axis direction of the spindle. This is advantageous in preventing cracking of the electrode plate. On the other hand, when forming a long sponge-like porous body, it is advantageous to apply a tensile force in the longitudinal direction so that the longitudinal direction of the spindle coincides with the longitudinal direction of the porous body. Therefore, when such a configuration is adopted, it is preferable that the compression part 2 for lead connection is provided in the longitudinal direction of the board 1.
Although the above-mentioned disadvantages become noticeable, according to the present invention, such disadvantages can be eliminated. FIG. 6 shows an example in which a hole 6 is punched in the center of the compressed portion 2 instead of a crack, and the same effect as in the previous example can be obtained. 7 and 8 show an example in which an uncompressed part 7 is left in the center of the compressed part 2. Since the uncompressed part 7 has a lower density than the compressed part 2, it will be elongated and cut during roller pressing, but the compressed parts 2a and 2b without cracks will remain before and after that, so the above example It also functions as a lead connection. In the above example, one crack or uncompressed part is formed at the center of the compressed part, but two or more cracks or uncompressed parts may be provided before and after the crack as long as the necessary area for the lead connection part is secured. Next, a specific example will be described. Example 1 A long substrate (having 55 spindle-shaped spaces/inch with the major axis in the longitudinal direction) made of a sponge-like porous nickel material with a thickness of 1.1 mm, a width of 200 mm, and a porosity of 95% was prepared as shown in FIG. Width 3mm, length 20mm as shown
A band-shaped compressed part with a size of is formed. The thickness of this compressed part is approximately 0.2 mm. Next, a crack is provided so as to divide this compressed part into two parts, front and back. On the other hand, nickel powder and carbonyl nickel powder are added to nickel hydroxide powder having an average particle size of 70 μm, and an aqueous solution of carboxymethyl cellulose is further kneaded to prepare a paste-like active material mixture. After filling the above-mentioned substrate with this active material, the active material on the surface of the substrate was removed, and then the substrate was sandwiched between rollers with a diameter of 300 mm to a thickness of 0.7 mm.
Apply pressure so that The surface of this roller is provided with numerous recesses each having a depth of approximately 0.01 mm. Next, the center of the crack is cut perpendicular to the longitudinal direction to form an electrode having at least one compressed part, and the electrode is dried. In this way, a nickel electrode is obtained. Example 2 In Example 1, a diameter of 3 mm was placed at the center of the substrate compression part.
A nickel electrode was obtained in the same manner as in Example 1, with a circular punched hole of mm in diameter. Example 3 In Example 1, the thickness was set at the center of the compressed part of the substrate.
An uncompressed portion of 0.9 mm and width of approximately 1 mm is provided, and a nickel electrode is obtained by the same operation as in Example 1. Although the example uses a nickel electrode, the same applies when a sponge-like porous metal material is used as a support for a positive electrode such as lead oxide, manganese dioxide, or silver oxide, and a negative electrode such as cadmium, zinc, or iron. Applicable to Next, 50 electrode plates were manufactured for each of Examples 1 to 3 and a comparative example in which the compressed portion was not subjected to any processing, by changing the pressure of the roller press and changing the packing density of the active material. In this case, the following table shows a comparison of the number of defects caused by cracks in the compressed parts that constitute the lead connection parts of the electrode plates.

[Table] Also, the packing density obtained by the method of Example 1 is 50~
We prototyped 10 KR-AA type batteries of 520 mAh/cc, 39 x 60 mm in size, combining nickel electrodes with general-purpose cadmium electrodes.
The characteristics when discharged at 500 mA after being charged for an hour are shown by A in Fig. 9. B shows the discharge characteristics of a battery using a nickel electrode as a comparative example. As described above, according to the present invention, it is possible to eliminate defects in the lead connection portion, and it is possible to obtain an electrode of constant quality with excellent discharge characteristics.

[Brief explanation of drawings]

Fig. 1 is a plan view showing a sponge-like porous substrate with a compression section provided, Fig. 2 is a sectional view taken along the line -' in Fig. 1, Fig. 3 is a sectional view after roller pressing, and Fig. 4 is a sectional view taken along the line -' in Fig. 1.
The figure is a plan view of the substrate used in the embodiment of the present invention.
The figure is a sectional view taken along the line 4-', FIGS. 6 and 7 are plan views showing other examples of the board, 8 is a sectional view taken along the line 7-', and 9 is a nickel-cadmium battery. A comparison of the discharge characteristics is shown. 1...Substrate, 2...Compressed part, 5...Crack, 6...
...Punching hole, 7...Uncompressed part.

Claims (1)

[Claims] 1. A step of forming a band-shaped compressed part constituting a lead connection part along the longitudinal direction of a long substrate made of a sponge-like porous metal material, and a step of filling the substrate with a paste-like active material mixture. Next, the step of pressing the substrate with a pair of rollers whose axes are arranged perpendicular to the longitudinal direction of the substrate, and then cutting the substrate at the center of the strip-shaped compression part in the direction perpendicular to the longitudinal direction of the substrate. A method for producing a battery electrode comprising the step of dividing the compressed part into two parts by forming an electrode plate including at least one compressed part constituting a lead connection part, the method of manufacturing a battery electrode comprising the step of dividing the compressed part into two parts by applying a roller press to the compressed part at the same time as the compression or by applying a roller press to the compressed part at the same time as the compression. 1. A method for manufacturing a battery electrode, comprising the step of previously forming a crack, a notch, or an easily cutable uncompressed part so as to divide a band-shaped compressed part into front and back halves in the longitudinal direction.