JPH09283129A - Method of manufacturing cadmium electrode plate for alkaline storage battery - Google Patents

Abstract

(57) Abstract: [PROBLEMS] To provide a method for producing a cadmium electrode plate for an alkaline storage battery, which can reduce the amount (dissipation amount) of methylcellulose dissolved in a cleaning liquid in cleaning a chemical conversion electrode plate. An unformed electrode plate in which an unformed active material layer is formed by filling an active material paste containing an active material material made of cadmium oxide and a binder made of methylcellulose into a current collector. make. The density of the non-activated material layer is 2.
The unformed electrode plate is pressed in the thickness direction so as to be 3 to 3.6 g / cc, and then the formed electrode is formed to form an electrode plate. The chemical conversion plate in the chemical conversion plate is removed by immersing the chemical conversion plate in purified water flowing at a predetermined flow rate. As a result, the amount of methyl cellulose after washing the chemical conversion plate becomes 80% by weight or more based on the amount of methyl cellulose before washing the chemical conversion plate.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for manufacturing a cadmium electrode plate for an alkaline storage battery.

[0002]

2. Description of the Related Art Cadmium plates used in alkaline storage batteries such as nickel-cadmium storage batteries are generally manufactured as follows. First, an active material material made of cadmium oxide and a binder made of methylcellulose are kneaded to prepare an active material paste. Next, the active material paste is filled in a current collector made of a conductive core material such as punching metal to form an unformed electrode plate having an unformed active material layer formed on the current collector, and this is dried. Next, the unformed electrode plate is pressed by a rolling mill in the thickness direction to make the unformed active material layer have a predetermined density. Next, the non-formed electrode plate is subjected to one or more times of formation charge / discharge in an alkaline aqueous solution (electrolyte) such as an aqueous solution of potassium hydroxide to form a formation electrode plate. Next, the chemical conversion electrode plate is washed with purified water to remove the electrolytic solution in the conversion electrode plate, and then dried to complete a cadmium electrode plate. As a specific method of removing the electrolytic solution, for example, there is a method of immersing the chemical conversion electrode plate in purified water flowing at a predetermined flow rate. If the electrolytic solution in the chemical conversion electrode plate is not removed in this way, it becomes difficult for the discharge product cadmium hydroxide to change to the charge product cadmium, and the active material may be inactivated.

In manufacturing a cadmium electrode plate, a carbon layer may be formed on the surface of the active material layer of the cadmium electrode plate completed by removing the electrolytic solution in order to enhance the oxygen gas absorption performance. The carbon layer is formed, for example, by applying a paste prepared by kneading carbon powder and methyl cellulose onto the surface of the electrode plate.

[0004]

However, since methyl cellulose used as a binder for the active material is water-soluble, when the chemical conversion plate is washed to remove the electrolytic solution, the methyl cellulose is Dissolves in the wash solution. For example, when the chemical conversion plate is immersed in purified water having a flow rate of 0.07 m / sec and a temperature of 20 ° C. for 30 minutes, the dissolved amount (disappearing amount) of methylcellulose becomes 30% by weight. Also, 14
When soaked for a period of time, the amount of dissolution becomes 55% by weight, and about half of methylcellulose is dissolved. When methyl cellulose is dissolved in the cleaning liquid as described above, the binding strength of the active material layer is lowered, and the active material is easily dropped from the electrode plate. In the conventional method, the amount of methylcellulose lost by washing is large, and the amount of methylcellulose after washing the chemical conversion plate is 7 to the amount of methylcellulose before washing the conversion electrode plate.
It was about 0% by weight. Therefore, there is a problem that the amount of active material dropped off increases and the life of the alkaline storage battery is shortened. Further, when the methyl cellulose disappears, the effect of suppressing the expansion of the active material possessed by the methyl cellulose decreases. This also shortens the life of the alkaline storage battery. Further, when the carbon layer is formed on the surface of the active material layer by application such as roller transfer, a force is applied to the active material layer when the carbon layer is formed, and the active material layer is separated from the electrode plate. .

An object of the present invention is to provide a method for producing a cadmium electrode plate for an alkaline storage battery, which can reduce the amount of methylcellulose dissolved in the cleaning liquid in cleaning the chemical conversion electrode plate.

Another object of the present invention is to provide a method for producing a cadmium electrode plate for an alkaline storage battery, which can prevent the active material from falling off due to the dissolution of methylcellulose in washing the chemical conversion electrode plate.

Another object of the present invention is to prevent the active material layer from peeling from the electrode plate when a carbon layer is formed on the surface of the active material layer due to the dissolution of methylcellulose in washing the chemical conversion electrode plate. It is to provide a method for manufacturing a cadmium electrode plate.

[0008]

In order to solve the above problems, the present invention fills a current collector with an active material paste containing an active material material made of cadmium oxide and a binder made of methylcellulose. Make an unformed electrode plate in which the unformed active material layer is formed on the current collector, press the unformed electrode plate in the thickness direction and then form the formed electrode plate, and wash the formed electrode plate with the cleaning liquid. A method for producing a cadmium electrode plate for an alkaline storage battery in which an active material layer is formed on a current collector by removing a formation solution in a formation electrode plate. In the first invention, the unformed active material plate is pressed in the thickness direction to suppress the dissolution of methylcellulose so that the density of the unformed active material layer becomes 2.3 to 3.6 g / cc. Cleaning may be the same as conventional. By doing so, the amount of methyl cellulose after washing the chemical conversion plate with respect to the amount of methyl cellulose before washing the chemical conversion plate (hereinafter, simply referred to as residual amount of methyl cellulose) is 80.
More than weight%.

In the first aspect of the invention, the residual amount of methylcellulose is increased (to 80% by weight or more) to prevent the active material from falling off the electrode plate, and the active material layer from the electrode plate when forming the carbon layer is suppressed. Of peeling. The density of the non-activated material layer is 2.
When it is less than 3 g / cc, the pore volume of the active material layer becomes large and the contact area with the cleaning liquid increases, so that the amount of methylcellulose dissolved by the cleaning increases. Further, if the unformed electrode plate is pressed so that the density of the unformed active material layer exceeds 3.6 g / cc, the electrode plate may warp.

In the second aspect of the present invention, the unpressurized electrode plate is pressurized in the same manner as in the prior art, and the washing conditions are changed from the prior art to suppress the dissolution of methylcellulose. In order to increase the residual amount of methyl cellulose by selecting the washing conditions, the chemical conversion plate is placed in a washing liquid consisting of purified water at a temperature of 25 to 50 ° C in an amount of 0.5 to 1
The chemical conversion plate may be washed by immersion for a time. The flow rate of the cleaning liquid in the case of performing cleaning under this condition may be the same as that of the conventional one, but within the range of this condition, the flow rate can be made higher than that of the conventional one. Experiments have shown that even if the flow velocity is increased to 0.7 m / sec, the residual amount of methyl cellulose can be maintained at 80% by weight or more. When the temperature is lower than 25 ° C, the amount of methylcellulose dissolved by washing increases.
Incidentally, if the second invention is applied when the pressure applied to the unformed electrode plate is made higher than the conventional pressure as in the first invention, the synergistic effect of both inventions can be obtained.

In the third aspect of the invention, the residual amount of methyl cellulose is increased by using an alkaline liquid as the cleaning liquid. That is, the chemical conversion plate is washed by immersing it for 0.5 to 1 hour in a cleaning liquid composed of an alkaline aqueous solution having a pH of 11 to 13. If the pH is less than 11, the amount of methylcellulose dissolved by washing increases. Also, pH
Is more than 13, a large amount of alkali remains in the electrode plate, which causes a problem of carbonation of the active material.

In order to sufficiently prevent the active material from falling off, the amount of methyl cellulose to be blended in the active material paste is appropriately selected and the residual amount of methyl cellulose is set to 80% by weight or more so that the active material layer in the active material layer after washing is The content of methyl cellulose is preferably 0.3% by weight or more. However, 3.
When the content exceeds 0% by weight, the amount of the active material packed decreases, so the content of methylcellulose in the active material layer after washing is
It is preferably 3.0% by weight or less.

Further, the present invention is applied to a method for producing a cadmium electrode plate in which a carbon layer containing carbon is formed on the surface of an active material layer after washing the chemical electrode plate to remove the formation solution in the electrode plate. Therefore, it is possible to suppress the peeling of the active material layer from the electrode plate when the carbon layer is formed.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Each cadmium electrode plate used in the test was manufactured as follows. First, 66.76 parts by weight of an active material material made of cadmium oxide powder, 32 parts by weight of water, 1 part by weight of a reinforcing material made of nylon fiber, and 0.24 parts by weight of a binder made of methylcellulose are kneaded to make an active material paste. made. Next, 49 g of the active material paste was filled in a current collector made of punching metal to prepare an unformed electrode plate in which an unformed active material layer was formed on the current collector. Next, this was left to dry in an atmosphere of 140 ° C. for 0.5 hour. Next, the unformed electrode plate was pressed in the thickness direction by a rolling mill to make the unformed active material layers have respective densities shown in Table 1. In addition,
In order to set the density of the unformed active material layer to 2.3 to 3.6 g / cc, the unformed electrode plate may be pressed at a pressure of 50 to 400 kg / cm ² . The amount of methylcellulose in the active material layer at this point (before washing) is 0.35% by weight.

Next, the unformed electrode plate is immersed in an aqueous potassium hydroxide solution having a concentration of 30% by weight, charged at 210 mA for 15 hours, and then discharged at 420 mA for 4 hours.
The chemical electrode plate was made repeatedly. Next, the electrode plate was immersed in a cleaning liquid flowing at a flow rate of 0.07 m / sec for 30 minutes to remove the electrolytic solution in the electrode plate. The cleaning liquid used for this cleaning had the temperature and pH shown in Table 1, respectively. It should be noted that purified water was used as the cleaning liquid having a pH of 6.9,
A potassium hydroxide solution was used as the cleaning liquid having a pH of 10 to 12. Then, the chemical conversion electrode plate was left to stand in an atmosphere of 80 ° C. for 30 minutes and dried to complete each cadmium electrode plate used in the test.

Next, each electrode plate was cut into a size of 40 × 40 mm and dropped from a height of 300 mm 10 times to measure the amount of active material falling from the electrode plate.

A mixture of carbon powder and methyl cellulose was roll-transferred onto the surface of the active material layer of each electrode plate to give a thickness of 1
A carbon layer having a thickness of 0 μm was formed, and the rate of occurrence of peeling of the active material layer generated when forming the carbon layer was examined (test number: 50 sheets each). The results of these tests are also shown in Table 1. The peeling occurrence rate is the ratio of the number of peeled pieces.

[0018]

[Table 1] Examples 1 to 3 in Table 1 above are examples of the first invention,
Examples 4 to 7 are examples of the second invention, and are 8th and 9th.
Is the third embodiment. From this table, the cadmium electrode plate of the present example, because it can suppress the dissolution of methylcellulose in the cleaning liquid, compared with the cadmium electrode plate of the comparative example, the amount of active material loss and the activity that occurs when forming the carbon layer. It can be seen that the incidence of peeling of the material layer can be lowered.

Next, each of the above-mentioned electrode plates (negative electrode plates) is
AA alkaline storage batteries were made by combining a sintered nickel electrode plate (positive electrode plate) of Ah and an electrolytic solution containing a potassium hydroxide solution. Then, each battery is 9 at 1 CmA.
A cycle life test was performed in which charging and discharging were repeated by charging for 0 minutes and then discharging at 1 CmA. FIG. 1 shows the measurement result. From this figure, it can be seen that the battery using the cadmium electrode of the present example has a longer cycle life than the battery using the cadmium electrode of the comparative example.

Then, various electrode plates were prepared in the same manner as in Example 1 except that the methyl cellulose contained in the active material paste was changed and the content of methyl cellulose in the active material layer after washing was different. Then, the amount of active material falling off of each electrode plate and the rate of occurrence of exfoliation of the active material layer that occurs when forming the carbon layer were examined (3 tests). FIG. 2 shows the relationship between the content of methyl cellulose and the amount of active material falling off the electrode plate. Further, FIG. 3 shows the relationship between the content of methyl cellulose and the incidence of peeling of the active material layer. From both figures, when the content of methyl cellulose in the active material layer after washing is less than 0.3% by weight, the amount of active material dropped off increases, and the active material layer easily peels off when the carbon layer is formed. I understand.

Next, the pressure applied to the unformed electrode plate was changed, and other various steps were carried out in the same manner as in Example 1 to prepare various electrode plates having different density of the unformed active material layer. Then, the amount of methylcellulose dissolved when each electrode plate was immersed in the cleaning solution (the amount of methylcellulose in the electrode plate disappeared) was measured, and the relationship between the density of the unactivated material layer and the amount of methylcellulose dissolved was examined. It was FIG. 4 shows the measurement results. From this figure, it can be seen that when the density of the unactivated material layer becomes high, the dissolution amount of methylcellulose decreases, and when the density of the unactivated material layer becomes 2.3 g / cc or more, the dissolution amount of methylcellulose falls below 20% by weight. I understand. From this, the density of the unactivated material layer is set to 2.
When the amount is 3 g / cc or more, the residual amount of methyl cellulose is 8
It can be seen that the amount can be 0% by weight or more.

Next, various electrode plates were prepared in the same manner as in Example 4 except that the temperature of the cleaning liquid for cleaning the chemically-formed electrode plate was changed. Then, the dissolution amount of methyl cellulose when each electrode plate was immersed in the cleaning liquid was measured to examine the relationship between the temperature of the cleaning liquid and the dissolution amount of methyl cellulose. FIG. 5 shows the measurement results. As shown in the figure, when the temperature of the cleaning liquid increases, the amount of methylcellulose dissolved decreases, and
It can be seen that the dissolved amount of methyl cellulose falls below 20% by weight at 5 ° C or higher. From this, the temperature of the cleaning liquid is 25 ° C.
It can be seen that the amount of residual methyl cellulose can be 80% by weight or more by the above.

Next, various pH plates were prepared in the same manner as in Example 8 except that the pH of the cleaning solution for cleaning the chemical conversion electrode plate was changed. Then, the dissolution amount of methyl cellulose when each electrode plate was immersed in the cleaning liquid was measured to investigate the relationship between the pH of the cleaning liquid and the dissolution amount of methyl cellulose. FIG. 6 shows the measurement result. From this figure, it can be seen that the dissolved amount of methyl cellulose decreases as the pH of the cleaning liquid increases, and the dissolved amount of methyl cellulose falls below 20% by weight when the pH becomes 11 or more. From this, it can be seen that when the pH of the cleaning liquid is set to 11 or more, the residual amount of methyl cellulose can be set to 80% by weight or more.

[0024]

EFFECTS OF THE INVENTION According to the present invention, in the washing of the chemical conversion plate, the amount of methylcellulose dissolved in the washing liquid (disappearing amount) can be reduced and a large amount of methylcellulose can remain in the active material layer. It is possible to suppress the active material from falling off from the electrode plate and to prevent the active material layer from peeling off from the electrode plate when forming the carbon layer. As a result, the use of the cadmium electrode plate of the present invention can extend the cycle life of the alkaline storage battery.

[Brief description of drawings]

FIG. 1 is a diagram showing cycle life characteristics of each battery used in a test.

FIG. 2 is a graph showing the relationship between the content of methyl cellulose and the amount of active material removed.

FIG. 3 is a diagram showing the relationship between the content of methyl cellulose and the rate of occurrence of peeling of an active material layer that occurs when forming a carbon layer.

FIG. 4 is a diagram showing a relationship between a density of an unactivated material layer and a dissolution amount (disappearance amount) of methylcellulose.

FIG. 5 is a graph showing the relationship between the temperature of the cleaning liquid and the amount of methylcellulose dissolved (disappearing amount).

FIG. 6 is a diagram showing the relationship between the pH of the cleaning liquid and the amount of methylcellulose dissolved (disappearing amount).

Claims (5)

[Claims] 1. An unformed material in which an unformed active material layer is formed on the current collector by filling an active material paste containing an active material material made of cadmium oxide and a binder made of methylcellulose into the current collector. The electrode plate is made, the unformed electrode plate is pressed in the thickness direction and then formed to form the formed electrode plate, and the formed electrode plate is washed with a cleaning liquid to remove the forming solution in the formed electrode plate and A method for producing a cadmium electrode plate for an alkaline storage battery, in which an active material layer is formed on a current collector, wherein the unformed electrode plate has a density of 2.3 to 3.6 g / cc. So that the amount of methylcellulose remaining in the active material layer after washing the chemical conversion plate with respect to the amount of methylcellulose before washing the chemical conversion plate is 80% by weight or more. Al which is characterized by Method of manufacturing a cadmium plate for the Li battery. 2. An unformed material in which an unformed active material layer is formed by filling an active material paste containing an active material material made of cadmium oxide and a binder made of methylcellulose into the current collector. The electrode plate is made, the unformed electrode plate is pressed in the thickness direction and then formed to form the formed electrode plate, and the formed electrode plate is washed with a cleaning liquid to remove the forming solution in the formed electrode plate and In the method for producing a cadmium electrode plate for an alkaline storage battery in which an active material layer is formed on a current collector, the chemical conversion electrode plate is washed for 0.5 to 1 hour in a cleaning liquid made of purified water at a temperature of 25 to 50 ° C. Dipping is performed, and the amount of methylcellulose remaining in the active material layer after washing the chemical conversion electrode plate with respect to the amount of methylcellulose before washing the chemical conversion electrode plate is set to 80% by weight or more. Characteristic alkali Method for producing a battery for a cadmium plate. 3. An unformed material in which an unformed active material layer is formed by filling the current collector with an active material paste containing an active material material made of cadmium oxide and a binder made of methylcellulose. The electrode plate is made, the unformed electrode plate is pressed in the thickness direction and then formed to form the formed electrode plate, and the formed electrode plate is washed with a cleaning liquid to remove the forming solution in the formed electrode plate and In the method for producing a cadmium electrode plate for an alkaline storage battery in which an active material layer is formed on a current collector, the washing of the chemical conversion electrode plate is performed by immersing it in a cleaning liquid composed of an alkaline aqueous solution having a pH of 11 to 13 for 0.5 to 1 hour. The amount of methyl cellulose remaining in the active material layer after washing the chemical conversion electrode plate with respect to the amount of methyl cellulose before washing the conversion electrode plate is 80% by weight or more. Do Method of manufacturing a cadmium plate for potash battery. 4. The amount of methylcellulose in the active material paste is determined so that the amount of methylcellulose after washing the chemical conversion electrode plate with respect to the active material layer is 0.3 to 3.0% by weight. The method for producing a cadmium electrode plate for an alkaline storage battery according to any one of claims 1 to 3. 5. The carbon layer containing carbon is formed on the surface of the active material layer after the chemical conversion plate is washed to remove the chemical conversion solution in the chemical conversion plate. The manufacturing method of the cadmium electrode plate for alkaline storage batteries of Claims 1-4.