JPH0410182B2 - - Google Patents

Description

[Detailed description of the invention]

(a) Industrial Application Field This invention relates to a method for manufacturing electrodes for batteries, and in particular to a method for filling active materials in electrodes used in alkaline storage batteries. (b) Prior Art As methods for manufacturing electrode plates for alkaline storage batteries, especially nickel-cadmium batteries, the sintering method and the paste method have been known for a long time. In recent years, new manufacturing methods have been studied in which a metal fiber sintered body or a sponge-like metal (foamed metal) is used as a substrate (metal porous body). These metal porous bodies have a porosity of 88-95
%, and the pore diameter is up to several hundred μm, so the active material powder can be directly filled inside, simplifying the manufacturing process. However, it is surprisingly difficult to fill the active material powder directly inside the device evenly and densely, and many methods have been proposed. For example, in JP-A-53-10832 and JP-A-58-223261, attempts are made to fill the active material using suction force;
In JP-A-55-121270 and JP-A-55-14686, the active material is forcibly pushed in using a rubbing tool, and in JP-A-59-81866 and JP-A-59-
Publication No. 81868 describes that filling is performed using the pressure used when spraying the active material slurry. However, these methods have problems in terms of uniform filling. As in the above-mentioned method, when a force is applied that causes the active material to penetrate from one side of the metal porous body to the back side, a filtration effect works and the active material becomes clogged. As a result, the density of the active material becomes dense at the surface layer of the porous metal body and coarse at the inside. In order to solve this problem, the particle size of the active material should be made much smaller than the pore size of the porous metal material, but in practice, fine particulate active materials are difficult to handle and have a small bulk density. There was a problem that high-density packing was not possible. (c) Problems to be Solved by the Invention The present invention provides a method for manufacturing a battery electrode in which a porous metal body is filled with an active material uniformly and at high density. (d) Means for solving the problems The method for manufacturing the battery electrode of the present invention includes adding a dispersion medium to active material powder to form a kneaded product exhibiting Newtonian flow;
A porous metal body is immersed in the kneaded material, and the porous metal body is brought into contact with a roller installed in the kneaded material, and the roller is rotated at a circumferential speed different from the moving speed of the porous metal body to remove the active material. The purpose is to fill the In addition, when the circumferential speed of the roller is rotated in the same direction as the moving speed of the porous metal body,
Further effects can be obtained by setting the rotation speed to 0.5 times or more, or 0.5 times or more when rotating in the opposite direction. Incidentally, as the metal porous body, a metal fiber sintered body, a foamed metal, etc. are used. (e) Effect The inventor conducted various experiments in order to achieve high-density packing using a wet method, and obtained the following knowledge. First, when a kneaded material with a low moisture content is placed on a porous metal body and rubbed with a spatula-like jig, water preferentially enters the porous metal body, and the powder is transferred to the surface layer of the porous metal body. It only adheres as a kneaded material and does not reach the center of the porous metal body. In other words, the kneaded material appears to be filtered through the porous metal body. On the other hand, basically the same development occurs even if the water content of the mixture is increased somewhat. This is because the kneaded material is a non-Newtonian fluid that does not exhibit Newtonian flow. However, if the kneaded material is adjusted to exhibit Newtonian flow, the powder will penetrate into the interior of the metal porous body. The reason why the active material slurry adjusted to exhibit Newtonian flow can be efficiently filled inside the substrate is because the affinity between the active material powder and the medium (water in this case) is improved, and this improves the affinity between the active material powder and the medium (water in this case). It is possible to greatly suppress the overeffect of However, even if such a slurry is used, it is not possible to completely avoid overaction, and when filling is actually carried out, a slurry layer with a low water content is inevitably formed on the surface of the porous metal body. However, what is surprising is that this slurry layer with a low water content is still a fluid exhibiting Newtonian flow, so when the roller is rotated so that it is in contact with the surface of the porous metal body, it is forced into the inside of the porous metal body. It will be done. Furthermore, the viscosity of the kneaded material
Filling will proceed smoothly when it is below about 3000cps. It has been found that one of the methods for making this kneaded material exhibit Newtonian flow and achieve a viscosity of 3000 cps or less is to add a small amount of hexametaphosphate to the kneaded material. This is because the addition of hexametaphosphate to the kneaded material lowers the viscosity and improves fluidity. In addition, a roller is placed in a tank filled with the kneaded material so as to be in contact with the porous metal body,
It is effective to rotate this, and this is a feature of the present invention. This is due to the rotation of the rollers.
This is because the low water content kneaded material that adheres to the surface layer of the porous metal body and inhibits filling into the inside of the porous metal body is press-fitted. (f) Examples Experimental Example 1 It was found that the rotational speed of the roller provided in the tank filled with the kneaded material affected the filling amount. The test results are shown in FIG. In Figure 1, the "speed ratio" on the x-axis is the ratio of the circumferential speed of the roller to the moving speed of the metal porous body, where the (+) side is the same direction of movement and the (-) side is rotation in the opposite direction. It means. As is clear from FIG. 1, a high filling amount was obtained when the peripheral speed was twice or more when rotating in the same direction and 0.5 times or more when rotating in the opposite direction.
Incidentally, FIG. 2 shows a conceptual diagram of a typical apparatus according to the present invention. In FIG. 2, 1 is a metal porous body, 2 is a guide roller of the metal porous body, 3 is a filling roller that also serves as a reversing roller, 4 is a kneaded material made of nickel hydroxide, and 5 is a scraper. Example 1 To a mixture consisting of 95 parts by weight of nickel hydroxide and 5 parts by weight of cobalt hydroxide, 30 parts by weight of a 0.3% aqueous solution of hydroxypropyl cellulose (HPC) containing 0.3% sodium hexametaphosphate was added, and after mixing,
A kneaded product was obtained. This kneaded material is placed in a tank as shown in Figure 2, a porous metal body which is a sintered body of nickel fibers is introduced into the tank, and a roller in contact with this is moved at a circumferential speed three times the moving speed of the porous metal body. Then rotate it in the same direction. After removing the kneaded material adhering to the surface of the metal porous body filled with the kneaded material, it is dried, and then
A pressure of 1 ton/cm ² was applied to form the electrode A of the present invention. Example 2 Electrode B of the present invention was obtained in the same manner as in Example 1, except that 40 parts by weight of a 3% HPC aqueous solution was added to a mixture consisting of 95 parts by weight of nickel hydroxide and 5 parts by weight of cobalt hydroxide. Comparative Example 1 Comparative electrode C similar to Example except that the roller was rotated at a circumferential speed equal to the moving speed of the porous metal body.
I got it. Comparative Example 2 Comparative electrode D was obtained in the same manner as in Example 1 except that 30 parts by weight of a 3% HPC aqueous solution was added to a mixture consisting of 95 parts by weight of nickel hydroxide and 5 parts by weight of cobalt hydroxide. We investigated the fluidity and viscosity of the kneaded materials during the manufacturing process used for these electrodes A, B, C, and D, as well as the filling amount, filling state, and utilization rate when used as electrodes, and the test results are as shown in the following table. I got it.

[Table] Comparing Electrode A and Electrode C from this result, the one in which the roller installed in the kneaded material tank was rotated at a circumferential speed faster than the substrate movement speed (electrode A) was the one in which the roller was rotated at the same circumferential speed. The filling amount is much larger than that of (electrode C), the variation in the filling amount is small, and a good filling state can be obtained. Comparing Electrode A and Electrode B, we find that electrode B, which does not use sodium hexametaphosphate and adjusts fluidity and viscosity by adjusting the amount of glue and water added, has good filling properties, but The filling amount is about 10% smaller than that of electrode A due to the large amount of water in the kneaded material, and since the amount of glue added is also large, electrode A with added sodium hexametaphosphate has a higher utilization rate. On the other hand, in the kneaded material (electrode D) that does not exhibit Newtonian flow,
Almost impossible to fill. In other words, the low water content kneaded material that is introduced into the kneaded material and formed near the surface of the porous metal material is filled into the inside of the porous metal material with a slight pressure. Although the viscosity increases, it still maintains Newtonian flow. The main reason for this is thought to be that the flow resistance when flowing into the porous metal body is kept low because of this. In the examples, a nickel fiber sintered body was used as the metal porous body, but the method of the present invention is also suitable for foamed metal and the like. Furthermore, "Newtonian flow" here means that it shows a viscosity that is reproducible with a general viscometer (for example, a B-type viscometer), and even if it does not show ideal Newtonian flow. good. In addition, in the method of the present invention, the active material is filled by the rotation of rollers, so even if a metal fiber sintered body is used, which is said to have a weak bond in the sintered part, there is little damage and it can be easily processed during the process. It is excellent. (G) Effects of the Invention According to the manufacturing method of the present invention, a sufficient amount of filling can be obtained by simply rotating the roller on the surface of the porous metal body, the damage to the porous metal body is small, and the active material is evenly filled. Its industrial value is extremely large.

[Brief explanation of drawings]

FIG. 1 shows the relationship between the filling amount and the ratio between the moving speed of the metal porous body and the rotational circumferential speed of the roller, and FIG. 2 is a conceptual diagram of the active material filling device. 1... Metal porous body, 2... Guide roller, 3...
...filling roller, 4...kneaded material, 5...scraper.

Claims (1)

[Scope of Claims] 1 A dispersion medium is added to active material powder to form a kneaded product exhibiting Newtonian flow, a porous metal body is immersed in the kneaded product, and the porous metal body is brought into contact with a roller placed in the kneaded product. and filling the active material by rotating the roller at a circumferential speed different from the moving speed of the porous metal body. 2. The battery electrode according to claim 1, wherein the circumferential speed of the roller is at least twice the moving speed of the porous metal body when rotating in the same direction, and at least 0.5 times when rotating in the opposite direction. manufacturing method. 3. The method for manufacturing a battery electrode according to claim 1, characterized in that nickel hydroxide is used as the active material powder. 4. The method for producing a battery electrode according to claim 1, characterized in that water is used as the dispersion medium and hexametaphosphate is added to the dispersion medium.