JPS63965A - Manufacture of cadmium negative electrode plate for alkaline storage battery - Google Patents

Abstract

PURPOSE:To make it possible to produce negative electrode plates continuously, by adding two specific substances to an active substance paste including cadmium and water. CONSTITUTION:To an active substance paste including cadmium oxide and water, both one or more of hydroxycarboxylic acid and its salts, and one or more of boric acid and its salts are added. Therefore, since the time of standing use of the active substance paste is extended to about 30 hours, the continuous production as long as 24 hours is possible in the longest case.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for manufacturing a paste-type cadmium negative electrode plate for alkaline storage batteries.

Conventional technology and its problems Paste type cadmium negative electrode plate I! When producing I, the raw material active material powder may be cadmium cadmium, cadmium hydroxide, or cadmium oxide. Among these, metal cadmium has a very high valence and low activity, so it is not used as a main raw material for active materials. Furthermore, since cadmium hydroxide has a lower density than cadmium oxide or metal cadmium, there is a disadvantage that the energy density per volume of the negative electrode plate is low. On the other hand, cadmium oxide is most suitable as an active material raw material for paste-type negative electrode plates in terms of raw material cost, energy density, and electrode plate performance.

On the other hand, organic solvents and water can be considered as solvents for dispersing the active material powder, but if water is used because the raw material cost is low, cadmium oxide will react with water in a short time and change to cadmium hydroxide. , not only the energy density per plate volume decreases, but also the active material paste solidifies. In other words, it becomes impossible to apply the active material paste to the current collector or the core. For this reason, in the past, a solvent had to be used as the solvent. When using right buttock solvent,
Because there is no reaction in which cadmium oxide changes to cadmium hydroxide, a base-type cadmium negative electrode plate with good workability, high energy density per electrode plate volume, and high active material utilization rate can be obtained. It is more expensive than water, and requires various measures to prevent pollution, fire, and the working environment when handling it, which complicates the manufacturing process and significantly increases manufacturing costs.

Under these circumstances, one proposal has been made recently. The content is that a hydroxycarboxylic acid or its salt is added to an active 4171ff paste using cadmium oxide as an active material raw material.

According to this method, even if inexpensive water is used as a solvent, the conversion of cadmium oxide to cadmium hydroxide is suppressed for a long time, so the viscosity of the active material paste is stabilized and workability is good. However, with this method,
If no external force is applied to the active material paste, it has the effect of suppressing the hydration reaction of cadmium oxide and stabilizing the viscosity for about 24 to 70 hours. When stirring, shearing force, etc. are applied as in the case of adhesion, this effect is considerably reduced, and the paste viscosity could only be stabilized for about 3 hours.

For these reasons, there has been a need for a new method for stabilizing active material paste that will enable continuous production of paste-type cadmium negative frame plates.

Means for Solving the Problems The present invention involves the production of a paste-type cadmium negative electrode plate for alkaline storage batteries, in which at least one substance selected from a hydroxycarboxylic acid or a salt thereof is added to an active material paste containing cadmium oxide and water. By adding at least one of boric acid, boric acid, or a salt thereof, the viscosity of the active material paste is stabilized over time, thereby enabling continuous production of paste-type cadmium negative electrode plates.

Effect: When a hydroxycarboxylic acid or its salt is added to an active material paste containing cadmium oxide and water, when force such as stirring is applied as mentioned above, the time period during which the viscosity of the active material paste remains stable is It took about 3 hours. On the other hand, when boric acid or its salt is added to the active material paste instead of hydroxycarboxylic acid or its salt, the time during which the viscosity of the active material paste is stable is 10 minutes or less. However,
These two substances are living things! When both are added to one paste, the viscosity of the active material paste remains stable for about 30 minutes.
It was found that the hydration reaction of cadmium oxide was suppressed as the time increased dramatically.

The reason behind this hidden problem is not clear, but when boric acid or its salt is added alone to the active material paste, the viscosity of the active material paste decreases somewhat compared to when nothing is added. The pot life of cadmium oxide until the hydration reaction occurs and it loses its fluidity is almost the same as when nothing is added, so there is no movement toward suppressing the hydration reaction of cadmium oxide with boric acid or its salts. It seems that there are almost no. On the other hand, it is clear that hydroxycarboxylic acids and their salts have the ability to suppress the hydration reaction of cadmium oxide, although there are differences depending on the stirring conditions etc. It is thought that it has the effect of sustaining the action of the salt and its salts for a long time.

Comparing the method of the present invention and the conventional method from a technical point of view, in the case of the conventional method, the pot life of the active material paste is about 3 hours, as mentioned above. When this method is used to produce a paste-type negative electrode plate, the time required to prepare the active material paste and cleaning up afterward is included in the approximately 3 hours, so the net time used to manufacture the negative electrode plate is It is only a very short amount of time, approximately one hour. In other words, in the case of this conventional method, it is almost impossible to continuously produce paste-type negative lfiVi, and productivity is low and costs are low due to the low yield of raw materials and the difficulty in automating production equipment. becomes higher. On the other hand, in the case of the method of the present invention, as mentioned earlier, the pot life of the active material paste is about 30 hours, so continuous production for 8 hours, 12 hours, or at most 24 hours is possible. Contrary to the conventional method mentioned above, this is a revolutionary manufacturing method with high productivity and low cost, and its industrial value is great.

Example The present invention will be explained below using examples.

First, as an example of the present invention, a negative electrode plate was produced in the following manner.

Example 1 (Example of the present invention) 100 parts by weight of cadmium oxide powder, 18 parts by weight of Jinba cadmium powder, 0.6 parts by weight of methylcellulose, 5 parts by weight of vinyl chloride polymer latex emulsion, vinyl chloride-acrylic copolymer 0.8 parts by weight of the short fibers were mixed with 0.3 parts by weight of monosodium citrate and 0.2 parts by weight of potassium borate as cadmium oxide hydration reaction inhibitors, and mixed with the active material paste. did. This paste was applied to a porous plate made of nickel-plated iron, and then dried at 90° C. for 1 hour to produce a negative electrode plate. This is designated as sample A.

Example 2 (Example of the present invention) An Ω electrode plate was produced in the same manner as in Example 1 except that boric acid was used instead of potassium borate in Example 1. This is designated as sample B.

Example 3 (Example of the present invention) All procedures were carried out in the same manner as in Example 1 except that sodium hydrogen tartrate was used instead of monosodium citrate in Example 1, and sodium borate was used instead of potassium borate. A negative electrode plate was installed.

This is designated as sample C.

Example 4 (Example of the present invention) A negative electrode plate was produced in the same manner as in Example 1 except that citric acid was used instead of monosodium citrate in Example 1. This is designated as sample D.

Example 5 (Example of the present invention) Everything was carried out except that 0.15 parts by weight of citric acid and 0.15 parts by weight of monopotassium citrate were used instead of 0.3 parts by weight of sodium citric acid R1 in Example 1. A negative electrode plate was produced in the same manner as in Example 1. This is designated as sample E.

Example 6 (Example of the present invention) Instead of 0.3 parts of monosodium citrate in Example 1, 0.151 parts of tartaric acid and 0.3 parts of potassium gluconate were used.
using 151 parts of ffi, and 1 part by weight of boron mO and 0 parts by weight of sodium borate instead of 0.2 parts of potassium borate.
A harvest board was prepared in the same manner as in Example 1 except that 11 parts of . This is designated as sample F.

Next, as three comparative examples for the method of the present invention, negative electrode plates were produced using the conventional method as follows.

Example 7 (conventional method example) Example 1 1 column 1 contains 1 citric acid i'll 1 sodium 0.
A negative rod plate was prepared in the same manner as in Example 1, except that 0.5 fi 51 parts of monosodium citrate was used instead of 3 parts by weight and 0.21 fi parts of potassium borate. This is designated as sample G.

Example 8 (conventional method example) 0.3 parts by weight of monosodium citrate in Example 1,
Although 0.5 parts by weight of potassium borate alone was used instead of 0.2 parts by weight of potassium borate, the active material paste lost fluidity during cross-talk, making it impossible to apply it to the porous plate. .

Example 9 (Example of conventional method) Quen Fl! from the formulation in Example 1! However, the active material paste lost its fluidity during kneading, and it was impossible to apply it to the porous temporary.

As mentioned above, in Examples 8 and 9, the hydration reaction of cadmium oxide could not be suppressed, and the paste lost its fluidity and solidified during kneading, so the sample negative electrode plate could not be heated to 1F7. I could not do it.

Next, FIG. 1 and FIG. 2 will be explained, in which samples A to G produced in Examples 1 to 7 are compared.

FIG. 1 is a diagram showing the relationship between the elapsed time after the start of coating on a perforated plate and the date of application of the active material per unit area of the perforated plate (after drying). As is clear from this, Examples 1 to 6 of the present invention
It can be seen that in Samples A to F, the coating density remained constant for a long time and the paste viscosity was stable compared to Sample G of Conventional Example 7.

Figure 2 shows the combination of the negative electrode plates of samples A-G and the sintered nickel positive electrode plate prepared by the usual method to obtain a nominal capacity ffi 1.
．． These are the results of manufacturing a 9Ah cylindrical sealed nickel-cadmium storage battery and measuring its cycle life. A- in the diagram
G corresponds to negative electrode plate samples A to G, respectively. As is clear from this, Sample A- of Examples 1 to 6 of the present invention
The battery using F as the negative electrode plate maintains its capacity even after 1200 cycles, whereas the battery using Sample G of Conventional Method Example 7 as the negative electrode plate significantly decreases in capacity after about 800 cycles. My life is over.

In addition, when the battery was disassembled after the above test and the negative electrode plate was examined, no abnormality was observed in samples A to F, but in sample G, there were differences in the amount of active material applied depending on the part, and there were differences in the amount of applied material. Internal short circuits occurred in many parts. This is thought to be due to the poor viscosity and stability of the original active material paste. In other words, in the case of the manufacturing method of the present invention, in addition to the long pot life of the active material paste, the viscosity of the active material paste is stable, so it can be applied uniformly to the perforated plate.
It is thought that the cycle life has been improved.

Experiment Next, the results of a study on the necessary addition amount of the cadmium oxide hydration reaction inhibiting substance in the present invention will be described.

An active material paste was prepared by transporting sodium citric acid from the group consisting of hydroxycarboxylic acids or their salts and potassium borate from the group consisting of boric acid or its salts, and by changing the mixing ratio. ) was added, and the pot life until the paste lost its fluidity was measured. The results are shown in FIG. The effect of adding potassium borate to monosodium citrate is stable in the range of about 10 wt% to 240 wt%, but 24
It can be seen that if continuous production is assumed, the content should be in the range of 5 to 250 wt%.

Next, we investigated the optimal addition level of this two-component hydration reaction inhibitor to cadmium oxide.

The results are shown in FIG. Note that the amount of potassium borate added to monosodium citrate was 5 wt%. The horizontal axis represents the substance that inhibits the hydration reaction of cadmium oxide, and the vertical axis represents the pot life of the active material paste. As in the case of Figure 3, assuming 24-hour continuous production, the required addition rate of the Eiwa reaction inhibitor is the ffi of cadmium oxide.
0.1 wt% or more based on ffi, that is, citric acid 1
Sodium is required to be 0.095 wt% or more. In view of the above results, it is necessary that the amount of the hydration reaction inhibiting substance added is within the following range.

Monosodium citrate is ffiffi of cadmium oxide
0.095 wt% or more of potassium borate is required per m of monosodium citrate.
It is in the range of 50 wt%.

Among the Paddy reaction inhibitors, in addition to citric acid, gluconic acid, tartaric acid, and their respective salts have similar effects as hydroxycarboxylic acid-based substances, and as boric acid-based substances, in addition to potassium borate, boric acid , confirmed that sodium borate has an equivalent effect.

Effects of the Invention As described above, according to the present invention, it is possible to stabilize the viscosity of an active material paste for a long time, enable continuous production of paste-type cadmium negative electrode plates, and increase productivity. , it can offer excellent advantages such as lower costs.

[Brief explanation of drawings]

Figure 1 is a diagram showing the relationship between the elapsed application time and hanging time of the active material paste of the present invention and the active material paste of the conventional method.
The figure shows the life characteristics of a nickel-cadmium storage battery using the negative plate obtained by the present invention and the negative plate obtained by the conventional method. Figure 3 shows the two-component hydration reaction inhibiting material of the present invention. Figure 4 is a diagram showing the relationship between the mixing ratio of the active material paste and the working time of the active material paste, and Figure 4 is a diagram showing the relationship between the mixing ratio of the two-component Eiwa reaction inhibiting substance of the present invention with respect to cadmium and the working time of the active material paste. be. Mouth Wi Wi Iν Book (Hei, Koho) Ya 1 Open Open 1 I 7 Le WK / Collection 3 Orders Case description 1985 Patent Application No. 144648M 2. Title of the invention: Process for manufacturing cadmium negative electrode plates for alkaline storage batteries 3. Relationship with the case of the person making the amendment Patent applicant: 601 4, Date of dispatch of the amendment order) August 26, 1986
Day 5. Target of correction Drawing 6. Contents of correction

Claims (3)

[Claims] (1) In a manufacturing method for obtaining a paste-type cadmium negative electrode plate by applying an active material paste containing cadmium oxide and water to a current collector or core and drying it, hydroxycarboxylic acid or its salt is added to the active material paste. A method for producing a cadmium negative electrode plate for an alkaline storage battery, which comprises adding at least one substance selected from the group consisting of boric acid and at least one substance selected from the group consisting of boric acid and a salt thereof. (2) The amount of the hydroxycarboxylic acid or its salt added is 0.095% or more based on the weight of cadmium oxide, and the amount of the boric acid or its salt added is equal to the amount of the hydroxycarboxylic acid or its salt added. The method for producing a cadmium negative electrode plate for an alkaline storage battery according to claim (1), wherein the amount is 5 to 250% by weight. (3) Claim (1) or (2) wherein the hydroxycarboxylic acid is citric acid, gluconic acid, or tartaric acid.
) The method for producing a cadmium negative electrode plate for alkaline storage batteries as described in item 1.