JPS6255271B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a battery electrode in which a sponge-like porous metal body having a three-dimensional structure having a continuous space is filled with a paste-like active material. The purpose of this is to equalize the amount of binder deposited inside and on the surface of the metal porous body, and to improve electrode performance.

The currently well-known typical method for manufacturing nickel electrodes for alkaline batteries is to sinter nickel powder to create a porous body, impregnate this porous body with nickel salt, and electrically or chemically conduct active material. This process is repeated to fill the desired capacity. However, in this method, the process of filling the active material is complicated and requires repeated filling, and there has been a strong desire to streamline the manufacturing process.

Therefore, in contrast to this method, there is a method in which a paste-like active material is directly rubbed and filled into a spongy metal porous material such as nickel, which has a relatively small three-dimensional pore diameter, and then pressurized to form an electrode. Since it can be filled with a large amount of active material, it can be expected to produce a high-capacity electrode and also to simplify the manufacturing process. In this method, it is effective to fill the metal porous body with a paste-like active material, dry it, and then impregnate it with a binder liquid to prevent the active material from falling off. However, the following problems arose in this binder liquid impregnation process.

That is, the paste-like active material is continuously filled into the long strip-shaped metal porous body 1 and dried, and then the seventh
As shown in Figures 1 to 8, the metal porous body 1 is introduced into the impregnating device 11' by the roller 30, impregnated with the binder liquid, and then moved and introduced into the next step of the water removal device. The water droplets 17' of the binder liquid having a high surface tension move while being non-uniformly adhered to the surface of the porous metal body 1, and the water is removed, resulting in the following problem. Namely, (1) A large amount of water droplets from the binder liquid move from the impregnation device to the moisture removal device, and drip or adhere to the moisture removal device and the path leading to it, causing rust and electrical leakage accidents in the moisture removal device and nearby devices. may occur.
In addition, (2) if water is removed while the water droplets of the binder liquid remain unevenly attached to the surface of the porous metal body, the concentration distribution of the binder on the surface and inside of the porous metal body will become uneven. , poor electrode performance. Furthermore, (3) the time spent immersed in the binder liquid becomes longer, resulting in excessive binder liquid impregnation, and water droplets of the binder liquid adhering to the surface of the porous metal body and being transferred. In addition, a large amount of binder liquid is used. Furthermore, (4) a large amount of the binder liquid is contained in the metal porous body and further adheres to the surface and is transferred, so the capacity of the water removal device must be increased and the size of the device must be increased.

The present invention solves these problems and provides a method for producing a battery electrode in which a binder liquid is uniformly adhered and contained in a porous metal body, and the amount of binder liquid used is reduced. It is. More specifically, a plurality of slits preferably made of an elastic material are provided near or in contact with the surface of a sponge-like porous metal body (hereinafter simply referred to as a porous metal body) having a three-dimensional structure in the form of a long strip, A liquid tank filled with a binder liquid made by dispersing fluororesin in water is formed between these slits, and by passing a metal porous body through this tank, the binder liquid is uniformly contained in the porous body. The present invention also relates to a battery electrode characterized in that it includes a step of removing water droplets of excess binder liquid adhering to the surface of the metal porous body using a slit to make the wetting of the binder liquid uniform.

The present invention will be described below based on drawings showing embodiments thereof.

FIG. 1 shows an apparatus for manufacturing a nickel electrode using, for example, nickel hydroxide as an active material, to which the present invention is applied. First, a long strip-shaped porous metal body 1 is continuously moved in the direction of the arrow by a first feed roller 2, and its edge portion is compressed by a pressurizer 3 to provide a lead attachment portion. Thereafter, it passes over a tank 4 containing a paste-like active material stirred by a stirrer 3. Filling jig 6 installed in filling machine 5 during this passage
The paste-like active material supplied onto the porous body 1 is rubbed into and filled into the metal porous body by the reciprocating motion of the brush 7 . Porous metal body 1 filled with active material after that
is sent to the dryer 9 by the second feed roller 8 and dried, and the excess active material adhering to the surface of the metal porous body 1 is removed by the next-stage removing device 10.

Next, the metal porous body 1 is fed into an impregnating device 11 containing a binder liquid, such as a suspension of fluororesin powder, in order to prevent the active material from falling off. Thereafter, it is guided to a moisture removal device 12 to remove moisture appropriately, and then the third feed roller 1
3 and becomes a battery electrode.

In a nickel electrode manufacturing apparatus having such a configuration, the paste-like active material is prepared by adding about 20% by weight of nickel powder as a conductive material to commercially available nickel hydroxide powder, and then adding 0.5% by weight of carboxymethylcellulose aqueous solution as a mixing agent. was added in an appropriate amount and stirred thoroughly. The binder liquid used was an aqueous dispersion of fluororesin with a concentration of 5% by weight, and the long band-shaped porous metal body 1 was a sponge-like porous nickel metal body with a porosity of 97% and a length of 20 m and a width of 150 mm. The feeding speed of the porous metal body 1 was 0.5 mm/sec.

The method for manufacturing battery electrodes using the electrode manufacturing apparatus described above includes a step of pressurizing and forming a lead attachment part on the edge of the metal porous body 1, and a step of applying nickel hydroxide powder to the metal porous body 1 made of nickel. , a step of filling a paste-like active material having at least nickel powder and a carboxymethyl cellulose aqueous solution;
A process of drying the metal porous body 1 filled with active material, a process of removing excess active material adhering to the surface of the metal porous body 1, and a process of drying the metal porous body 1 filled with the active material, and a process of removing a binder liquid such as a fluororesin dispersion. a step of incorporating it into the metal porous body 1;
It includes a step of appropriately removing moisture in the metal porous body 1 and drying it.

2 to 4, the porous metal body 1 is made to contain a binder liquid, water droplets made of the binder liquid adhering to the surface of the porous metal body 1 are removed, and the porous metal body 1 is An embodiment will be described in which a plurality of slits are provided near or in contact with the surface of the metal porous body 1 as a means for uniformizing the concentration distribution of the binder therein. In these figures, the impregnating device main body 14 has a binder liquid 17 inside it through an inlet guide 15 and an outlet guide 16 that protrude upward.
storage tanks 18, 19, 20 are provided, and guides 15, 1
6, an entrance slit forming member 21 and an exit slit forming member 22 are provided. 23,2
4 is a slit guide. The binder liquid in the storage tanks 19 and 20 is pumped to a pump 27 through pipes 25 and 26.
The storage tank 18 is filled with the liquid that overflows from the overflow pipe 28 or the storage tanks 19 and 2.
0 to the pump 27 again for circulation.

On the other hand, the metal porous body 1 passes between the guide 15 and the slit forming member 23 and between the guide 16 and the slit forming member 24. At this time, porous body 1
passes through the binder liquid 17 filled in the storage tank 18, so that it is impregnated with the binder liquid, and the binder liquid adhering to the surface of the metal porous body 1 is uniformly removed by the slit. The uniformity of the concentration distribution of the binder contained in the metal porous body 1 is promoted.

In the embodiment according to the present invention, in order to reduce the water droplets of the binder liquid 17 that adhere to the surface of the metal porous body 1 and are transferred in the direction of movement of the metal porous body 1 (in the direction of the arrow), the outlet slit is It was more effective to provide the forming member 22 in close contact with the surface of the metal porous body 1. Further, the binder liquid 17 into the metal porous body 1
The content of the inlet slit forming member 21 is adjusted.
This could be easily achieved by adjusting the gap between the slit-forming members 21 and 22 and the amount of the binder liquid interposed between the slit-forming members 21 and 22.

The amount of the binder liquid interposed between the inlet slit forming member 21 and the outlet slit forming member 22 on the surface of the porous metal body 1 is constant on the surface of the porous metal body 1, rather than being abundant. For example, the amount of the binder liquid between both slit forming members 21 and 22 is 1.2 to 5.0 times the apparent amount of the porous metal body 1, or the thickness of the layer is 1.2 to 5.0 times the thickness of the porous metal body 1. It was found that 3.0 times the content of the binder liquid becomes uniform, which ultimately leads to an improvement in electrode performance.

FIG. 5 shows the current-voltage characteristics of alkaline batteries A and B constructed by combining a nickel electrode manufactured according to an embodiment of the present invention and a slit electrode according to the conventional example with a sintered iron electrode, respectively.

Nickel electrodes manufactured by conventional methods containing a binder liquid have poor current-voltage characteristics because they contain an excessive amount of the binder liquid or are adhered unevenly. On the other hand, according to the present invention, since the content of the binder liquid is moderate and uniform, the current-voltage characteristics are improved.

FIG. 6 shows an example in which a spring 29 is attached to the slit-shaped member 22 to press the member 22 toward the metal porous body 1. Pneumatic pressure, hydraulic pressure, etc. may be used instead of a spring. According to this method, leakage of the binder liquid can be reduced and wear of the slit forming member can be compensated for.

The present invention is highly effective in containing a binder liquid into a dried metal porous body filled with a paste-like active material and further removing excess binder liquid adhering to the surface of the metal porous body. However, similar effects can be obtained by including a waterproofing agent in nickel sintered electrodes used in fuel cells, making the waterproofing agent uniform on the electrode surface, and even producing iron electrodes and cadmium electrodes. This can be easily inferred.

As described above, according to the present invention, it is possible to obtain an electrode with a uniform concentration distribution of the binder, and moreover, the power consumption of the water removal device can be reduced by 20% compared to the conventional device, and the use of the binder We were also able to reduce the amount by 20%.

Furthermore, it not only improves the performance of battery electrode bodies, but also reduces the amount of binder liquid used and is efficient.
Furthermore, dripping and leakage of excess binder liquid into the water removal device that follows the impregnation device that impregnates the metal porous body with the binder liquid and the path leading to this device is greatly reduced. , the waterproof structure, insulation measures, and the removal ability of the moisture removal device can be simplified, making it possible to reduce the size, weight, power consumption, and cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic vertical cross-sectional view showing the configuration of an electrode manufacturing apparatus in an embodiment of the present invention, FIG. The figure is a perspective view of the main parts, Figure 5 is a diagram showing the current-voltage characteristics of a nickel-iron battery using the nickel electrode according to the present invention and a battery using a conventional nickel electrode, and Figure 6 is a diagram showing the binder. FIG. 7 is a plan view of a conventional binder liquid impregnation device, and FIG. 8 is a sectional view taken along the line 7--' in FIG. 7. 1... Sponge-like metal porous body, 4... Paste-like active material, 5... Active material filling machine, 8... Dryer,
11... Binder liquid impregnation device, 15, 16... Guide, 17... Binder liquid, 21, 22... Slit forming member.

Claims (1)

[Claims] 1. A step of continuously filling a paste-like active material into a sponge-like porous metal body having a three-dimensional structure having spaces continuously connected in the form of a long strip, and this porous metal body. forming a liquid tank filled with a binder liquid between a plurality of slits provided near the surface of the dried metal porous body or in contact with the metal porous body; manufacturing a battery electrode characterized by comprising the steps of: homogenizing the content of a binder liquid in the porous metal body by passing through the metal porous body; and removing excess binder liquid on the surface of the metal porous body. Law. 2. A patent claim in which the binder liquid filled between the slits is always maintained at a constant amount within a range of 1.2 to 5 times the apparent volume of the porous metal body immersed in the liquid bath. A method for manufacturing a battery electrode according to item 1. 3. Claim 1, wherein the thickness of the binder liquid layer located between the slits and remaining on the surface of the porous metal body is in the range of 1.2 to 3 times the thickness of the porous metal body. A method for manufacturing electrodes for batteries.