JPS5833667B2 - Manufacturing method for battery electrodes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention involves moving a metal porous body having a three-dimensional structure (hereinafter referred to as foamed metal) having continuously connected voids, and The present invention relates to a method for manufacturing a battery electrode in which a paste-like active material is filled in a battery electrode.

Currently, a typical well-known anode for alkaline storage batteries is a sintered electrode.

This electrode is made by filling a carbon mold with nickel powder together with a metal net made of nickel, nickel-plated iron, etc. or a thin porous plate with almost no caloric pressure, and then baking it at a temperature of about 900°C in a hydrogen stream. Combined porosity 70
~so% porous substrate is used.

To fill the active material, the above substrate is impregnated with a highly concentrated nickel nitrate aqueous solution, dried, washed with electrolytic waves in a concentrated caustic alkaline aqueous solution at high temperature, and dried, or simply immersed in an alkaline aqueous solution. There are methods such as drying and heating decomposition.

These manufacturing methods require a complicated filling process of the active material and require repeated filling, so there has been a demand for rationalization of the manufacturing process.

A non-sintered electrode has been proposed as one method to improve this problem.

This electrode is manufactured by applying active material mixed with a binder to the core material of a metal net and applying pressure. It was difficult to fill.

On the other hand, an electrode with a three-dimensional structure is obtained by using a foamed metal as an active material holder, filling the foamed metal with a paste-like active material mixed with a binder, and applying pressure. Since the active material is filled inside the foamed metal, there is little capacity loss due to active material falling off, and high capacity can be expected because the active material can be packed at a high density.

However, when using a long piece of foamed metal to continuously fill it with active material, simply passing the foamed metal through the paste-like active material does not allow the active material to be uniformly distributed inside the foamed metal. This caused the problem that the liquid was not filled.

In addition, methods such as the active material kneading method for lead electrodes, in which the active material is pressed and filled using a pressure roller, etc., have small pores in the foamed metal, and the compressive strength is weak, so surface pores easily form. They cannot be hired because they are blinded.

In view of the above points, the present invention provides a method for densely and smoothly filling a foamed metal with a paste-like active material.

That is, the present invention supplies a paste-like active material to the top surface of a long strip-shaped foamed metal e, and rubs the active material with a rubbing tool that reciprocates on the top surface of the foamed metal to fill the voids in the foamed metal. It is characterized by:

According to this method, the paste-like active material is rubbed with a rubbing tool and filled little by little, so a large compressive force is not applied to the foamed metal, the pores on the two surfaces are not closed, and the paste is rubbed one after another. The voids are filled with the active material contained in the active material, and can be filled with high density.

Moreover, when adopting such a method, the foamed metal is placed above the paste tank C containing the active material.

It is convenient to supply the active material from the periphery of the foamed metal to the upper surface while stirring the active material in the paste tank below the foamed metal.

When using this method, as will be described later, in response to the pressurization caused by rubbing on the upper surface of the foam metal, a depressurizing effect occurs on the lower surface, further improving the filling efficiency.

The present invention will be explained below using examples.

First, the configuration of a continuous active material filling device will be explained.

Approximately 10 tons of nickel powder as a conductive material is added to commercially available nickel hydroxide powder, mixed well and stirred. Next, an appropriate amount of water or carboxymethyl cellulose aqueous solution is added and further stirred to form a paste-like active material.

This paste-like active material is put into the active material container 2, the stirrer drive motor 12 is operated, the rotary stirrer 11 is rotated, and the paste-like active material 3 is further kneaded well.

Note that the amount of paste-like active material 3 is adjusted so that it is above the porous plate 13 disposed at the top of the container 2.

The elongated foamed metal 1 is first passed manually from the main shaft roller 7 to the auxiliary roller 9, from between the perforated plate 13 and the brush 5 attached to the scrubbing tool 4, through the auxiliary roller 10, and then to the main shaft roller 8. After that, the main shaft roller 7.8 is automatically rotated to move the long metal foam.

At the same time as the main shaft roller 7.8 is actuated, the rubbing tool 4 is caused to slide along the moving direction of the foamed metal by the rubbing tool drive motor 6.

In this way, the paste-like active material is filled into the continuously moving elongated foamed metal by the sliding movement of the stirrer 11 and the scraper 4 on the foamed metal.

A schematic diagram of its configuration is shown in FIGS. 1 and 2.

Note that the foam metal may be moved continuously or intermittently.

Next, the filling mechanism of the paste active material will be explained.

First, after driving the agitator 11 and the scraping tool 4, the main shaft roller 7.8 is driven to move the elongated foamed metal 1 little by little.

The stirrer 11 uses two sets of four blades as shown in Fig. 2, and is rotated so that the active material is pressurized and moves from the center of the container 2 to the periphery, causing the active material to foam. While moving to the surface of the metal, at the same time the rubbing tool moves parallel to the direction of travel of the foam metal,
The active material on the top surface of the foam metal is rubbed with a rubber brush.

The movement of this rubbing tool is not limited to the above-mentioned direction, but may also be a reciprocating movement.

However, the filling state is best when the foam metal moves parallel to the moving direction as described above.

All of these operations are performed continuously to continuously fill the active material into the foamed metal.

The conditions for filling the active material are as follows.

The foam metal used is 15 cm wide, 5 m long, and 2 thick.
．． 5mm.

Porosity: 96±1%, total volume of active material filling area: approximately 50%
1, and the paste active material is placed in the filling device approximately 80% by 2.
It was accommodated.

The rubbing tool with a rubber brush has a width of 16 cm, a thickness of 3, and 10 sheets are used, the amplitude of the rubbing tool is 80 mm, and the speed is 1.
cycles/second.

The rotational speed of the stirrer was 3 to 5 revolutions/second, the moving speed of the foamed metal was 0.5 mm 7 seconds, and the solid content concentration in the paste was about 70 weight φ.

Based on these conditions, a more detailed filling situation of the paste active material is shown in FIG.

A in FIG. 3 shows the movement of the active material in the stirrer, and as other examples, B in FIG. 3 and C in FIG. 3 show the movement of the active material in the horizontal stirrer 14. .

In FIG. 3A, the two stirrers 11 are rotating so as to move the active material from the center to the periphery.

That is, the active material is stirred from the center, through the periphery, and up to the upper surface of the foam metal.

Therefore, the central part becomes depressurized, a depressurization (suction) phenomenon occurs at the lower surface of the foam metal, and the active material that has risen and moved from the periphery is rubbed by the brush of the rubbing tool on the upper surface of the foam metal. The foamed metal is moved into the foamed metal.

The active material enters the inside of the foamed metal from the top surface, and a portion of it passes through the bottom surface, gradually filling the entire foamed metal with the active material uniformly. (a raised part) and a corresponding reduced pressure part are created to efficiently fill the active material.

This improves the filling efficiency compared to simply stirring.

Therefore, it is a more effective filling method.

Also, even if the stirrer is horizontal, B in Figure 3.

As shown in C, move the foam metal horizontally (or move it horizontally) with a plate-shaped stirrer perpendicular to the direction of travel of the foam metal.
Then, in the direction of pushing the active material, the active material bulges around one side and is pushed to the upper surface of the foamed metal.

Correspondingly, since the opposite direction is the direction of tension, the pressure is slightly reduced, and the lower surface of the foamed metal is sucked.

In the figure, the thick arrow indicates the direction in which the active material is being sucked.

In this way, the active material is pressurized by the rubbing tool on the top surface of the foamed metal and sucked in on the bottom surface, so a kind of circulation of the active material occurs, and the active material is sufficiently filled to the inside of the foamed metal. become.

As mentioned above, pressure action (pushing up, rubbing) and depressurization (
This is a method for manufacturing electrodes for alkaline storage batteries that can be more efficiently and uniformly filled with a large amount of active material into a foamed metal using a stirring filling method that incorporates a tensile action.

It is desirable that the direction of stirring of the paste-like active material is perpendicular to the direction of movement of the foamed metal.

The active material cannot be efficiently filled unless the active material is pushed up and bulges onto the foamed metal from the periphery.

If only the bottom surface of the foamed metal is stirred, the amount of filling will decrease.

Therefore, it is effective that the traveling direction of the foamed metal is perpendicular to the moving direction of the active material during stirring.

Although the active material can be filled simply by stirring, the amount of filling tends to be uneven.

Next, the direction in which the surface of the foamed metal is rubbed is preferably parallel to the direction in which the foamed metal travels.

For example, if you move the scraping tool in a direction perpendicular to the direction of movement of the moving foam metal, the active material that has risen from the periphery will be pushed back and returned to its original state, allowing it to be efficiently activated on the top surface of the foam metal. Cannot be filled with substances.

That is, the active material on the upper surface of the foamed metal is pushed downward without passing through the foamed metal, resulting in a very poor filling efficiency.

Therefore, it is more effective to perform the rubbing operation of the active material parallel to the traveling direction of the moving metal foam.

In the above embodiment, the active material was stirred and supplied from the lower surface of the foam metal, but the stirred paste may be supplied from the upper surface of the foam metal.

However, the filling condition in the example is better.

By stirring, the active material can be prevented from settling and the concentration distribution can be prevented from becoming uneven, and a large amount of the active material can be filled.

Next, using the apparatus shown in Figure 1, the long foamed metal filled with the active material is cut into appropriate sizes, dried, immersed in a 3 weight φ fluororesin dispersion, pulled out, and semi-dried. After applying pressure in the thickness direction at a pressure of 400 Kp/m and completely drying, it was cut into a size of 50 x 55 mm, and a lead terminal was attached to form a nickel electrode.

As described above, about 10 electrodes were randomly selected from appropriate positions on a long piece of foamed metal, and the following capacity comparison test was conducted.

As the electrode in the comparative example, a sintered nickel anode, which is generally used in commercially available nickel-cadmium batteries, was used.

Its capacity is nominal IAh, electrode size 50ii x 55m
m, and the thickness is 1.1 mm.

In addition, the same foamed metal as above was simply passed through the paste-like active material at a speed of 0.5 rnm for 7 seconds, the passing time was 10 minutes, the foamed metal was filled with the active material, and then the above procedure was carried out. An electrode was prepared in the same manner as in the example.

This will be referred to as a mouth, and the electrode according to the above embodiment will be referred to as C.

For the capacitance test, electrode A is 0.2A, and electrode port C is 0.4A.
All of the batteries were discharged at a rate of about 5 hours (0.2C), and charge/discharge cycles were repeated in which the batteries were charged to about 130 to 140 of the discharge amount, and the capacity at the 10th cycle, when the capacity was stable, was compared.

The discharge characteristics at that time are shown in FIG.

When comparing electrodes of the same size, the discharge capacity of each electrode is 1.2±0. I A h% electrode port is 1.4
5±0.25Ah, and the electrode C of the present invention is 2.0±0
．． I A h is about 1.8 times that of electrode A.

In addition, although the same foamed metal is used for the electrode port, the amount of active material contained therein varies widely, and the filling amount is also much smaller than that of the product of the present invention.

When the electrode opening was cut, it was confirmed that the active material was not evenly filled inside.

The capacity variation is also more than twice as large compared to the product of the present invention.
This poses a practical problem.

As described above, in the present invention, the three-dimensionally structured metal porous body is filled with the active material in the form of a paste while being rubbed with a rubbing tool, so that the active material can be filled densely and smoothly.

[Brief explanation of the drawing]

Fig. 1 is a schematic diagram of the configuration of a continuous active material filling device used in an example of the present invention, Fig. 2 is a schematic cross-sectional diagram of the same device, and Figs. 3A and B
, C shows the filling status of paste-like active material, A shows an example using a rotary stirrer, B and C show an example using a horizontal stirrer, and Figure 4 shows a comparison of discharge capacity characteristics of various electrodes. It is a diagram. 1... Foamed metal, 2... Container (paste tank), 3... Paste active material, 4...
...Rubbing tool, 11゜14...Stirrer, 13.
...Perforated plate.

Claims (1)

[Scope of Claims] 1. A paste-like active material is supplied to the upper surface of a three-dimensionally structured band-shaped porous metal body having continuously connected voids, and the active material is reciprocated on the upper surface of the porous body. A method for producing a battery electrode, characterized in that the voids in the porous body are filled by rubbing with a rubbing tool. 2 A strip-shaped metal porous body having a three-dimensional structure having continuous voids is placed on the top of a paste tank, and the paste-like active material in the paste tank is stirred on the lower surface of the porous body, and the active material is stirred at the bottom of the porous body. A battery characterized in that a substance is supplied to the upper surface of the porous body from its periphery, and the active material is rubbed by a rubbing tool that reciprocates on the upper surface of the porous body C to fill the voids of the porous body. Method of manufacturing electrodes for use.