JPS608585B2 - Manufacturing method for alkaline storage battery sintered electrodes - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing competitively woven electrodes for alkaline storage batteries, particularly for nickel-cadmium storage batteries.

Generally, this type of sintered electrode is made by mixing nickel powder with a small specific gravity with a thickener and water, applying this mixture to a core of nickel or nickel-plated wire mesh, punched metal, etc., and then placing it in a reducing atmosphere. 800-10 in
The thickener and water are heated to 00q0 to decompose the thickener and water to form a porous nickel composite substrate, and the porous portions of this substrate are filled with specified amounts of shadow and water.
It is impregnated with a positive active material to form negative and positive electrode plates. In this impregnation process, salts of negative and positive active materials are used as impregnating liquid (cadmium salt on the cathode side, nickel salt on the anode side).
For example, an impregnation method involves impregnating a chloride substrate with an aqueous solution of nitrates, sulfates, and chlorides, then converting the salts into hydroxides as active materials by chemical substitution, electrolysis, or thermal decomposition in an alkali solution, and then washing and drying the salts with water. The process is repeated several times to obtain a specified amount of active material. In all of the above impregnation steps, a layer of active material is deposited on the substrate surface, that is, a hydroxide such as cadmium hydroxide on the cathode side and nickel hydroxide on the anode side.

These deposits block the pores of the porous substrate, and since they are non-falling, they remain unremoved even in the next washing with water, which causes variations in the amount of impregnation in the next impregnation step. Furthermore, the active material deposited on the surface of the substrate falls off from the electrodes during charging or storage of the battery and moves into the electrolytic solution, causing self-discharge.

Therefore, in order to eliminate these drawbacks, a method has been explored in which the deposits on the substrate surface are removed with a brush or the like by brushing when washing the hydroxide formed by chemical substitution etc. in the above impregnation process with water. There is. however,
According to this method, it takes a lot of man-hours to perform brushing each time the electrode is washed with water, making the impregnation process complicated, and there is a concern that not only the electrode surface will be damaged but also the active material in the porous portions of the substrate will be removed.

Alternatively, as shown in Japanese Patent Publication No. 39-14323, the substrate taken out from the impregnating liquid is immediately immersed in water or running water for 1 to 2 seconds, and this instantaneous immersion in water causes A method has been proposed to remove deposits on the substrate surface, but in actual production, the immersion time is instantaneous (1 to 10 minutes).
It is difficult to maintain uniformity for 2 seconds), and if soaked for a long time, salts in the porous parts of the substrate will also be dissolved and removed, resulting in unevenness and a decrease in the amount of impregnation.

The present invention has been made in view of these points, and its gist is that instead of immersing a substrate impregnated with an active material salt in water, a substrate having the same composition as the original impregnating liquid, but with a lower concentration than the original impregnating liquid. The method involves immersing the bond in a low-concentration salt solution, and through this operation, the concentration of salts adhering to the substrate surface is reduced by diffusion due to the concentration difference, making it easier to remove from the substrate surface. The time required to remove deposits from the substrate surface can be kept to several tens of seconds, and uniform immersion time and removal can be achieved, making it practical.

That is, ``the present invention is a porous sintered substrate made by sintering fine nickel powder, and salts of Tatsuike active material (cadmium salt on the cathode side).
After impregnating the anode side with nickel salt), the substrate was placed in a salt solution having the same composition as the above impregnating solution but at a lower concentration than the impregnating solution for several tens of seconds.Diffusion due to these concentration differences occurred. It is characterized by reducing the concentration of salts adhering to the substrate surface and removing them from the substrate surface, and then converting the salts in the porous parts of the substrate into hydroxides by chemical substitution, electrolysis, or thermal decomposition in an alkaline bath. A method for manufacturing Yin and Yang sintered electrodes for alkaline storage batteries.

Here, the diffusion rate of the impregnating salt solution is determined by the concentration difference between the impregnating salt solution and the immersing salt solution. The specific gravity of the impregnated salt solution was determined by considering the following points: ensuring the desired amount of impregnation with a fixed number of impregnations, maintaining the utilization rate, and dissolving and cleaning deposits on the substrate surface without causing variations in the amount of impregnation. .

30-1.50 nickel nitrate is suitable.

In addition, the specific gravity of nickel nitrate, which is the above imitation salt solution, is 1.3.
If it is less than 0, the diffusion rate is fast and the immersion time is limited to a short time, making it difficult to obtain uniformity and lowering the utilization rate.

In addition, if the specific gravity is 1.50 or more, the diffusion rate becomes slow, and although sufficient soaking time, impregnation amount, and utilization rate can be ensured, the effect of melting and cleaning deposits on the substrate surface decreases, making it difficult to remove deposits. Next, in an embodiment of the present invention, a porous sintered substrate of 65 x 41 x 0.6 (ribs) made by sintering fine nickel powder is heated at a temperature of 70 oo to 8000 with a specific gravity of 1. .7
After soaking in nickel nitrate with a specific gravity of 0 to 1.74 for 2 hours to impregnate the active material sea, it was soaked in nickel nitrate with a specific gravity of 1.40 at room temperature for 3 hours, and then subjected to intermediate drying ``alkali treatment (chemical layer fusuma). A series of steps including water washing and drying is performed 3 to 4 times, and a specified amount of active material (nickel hydroxide) is filled into the substrate to form an anode plate.

In the case of the cathode plate as well, cadmium nitrate may be used as the impregnating salt, and the same operation may be performed using cadmium nitrate having a lower concentration than the impregnating salt as the bonding salt. The table below compares each value when the method of the present invention and the conventional method (using water) are applied as a means for removing salts from the substrate surface during the manufacture of anode plates. Table 2 compares the amount of impregnation depending on the bond solution and soaking time. Table 2 compares the variation in the amount of impregnation and the utilization rate when measurements were made under the same conditions except for the soaking solution.

As is clear from Table 1, Table 2, and the above table, by applying the method of the present invention, compared to the conventional method (using water), it is possible to secure a sufficient soaking time to a practical extent, and the variation in the amount of impregnation is also extremely small. 4. The usage rate will not decline.

The reason for this is that with the conventional method, there is a concern that even the material impregnated into the porous parts of the substrate may be washed away, so it is necessary to shorten the soaking time. The active material is the sum of the amount of impregnation impregnated into the substrate and the amount of corrosion of the substrate by the impregnating liquid, and when the impregnated salt in the porous parts of the substrate is washed away as in the conventional method, in addition to the amount of impregnation. Even the amount of corrosion was reduced, and as a result, the utilization rate was poor as shown in Table 2 above.Also, the surface condition of the electrode plate was not much different from that of the electrode plate immersed in water.Contrary to the present application, the substrate First, a low concentration of active material salt is soaked in the porous part,
A manufacturing method has been proposed in which the active material salt is then impregnated with a high concentration of active material salt to increase the amount of impregnation in a single impregnation process. The active material salt at a low concentration does not reduce its concentration, but rather increases its concentration, making it difficult to remove it from the substrate surface.

As described above, according to the present invention, it is possible to significantly reduce the variation in the amount of impregnation in the step of impregnating the active material in a dew pond, to fill the porous portions of the substrate with a specified amount of the active material in a specified number of times, and to reduce the amount of impregnation present on the surface of the substrate. Manufacture of a practical competitively connected electrode that can secure several tens of seconds for kimono removal operation and achieve more uniform immersion time and removal compared to instantaneous (1 to 2 seconds) underwater or running water removal operation. It provides law.

Claims (1)

[Claims] 1. After a porous sintered substrate is impregnated with salts of a predetermined active material, it is immersed in a salt solution having the same composition as the impregnating solution but at a lower concentration than that of the impregnating solution. A method for producing a sintered electrode for an alkaline storage battery, which comprises reducing the concentration of salts adhering to the surface of a substrate, removing them from the surface of the substrate, and then converting the salts in the porous portions of the substrate into hydroxides.