JPH05205737A - Manufacture of nickel hydroxide electrode for alkaline storage battery - Google Patents

Abstract

PURPOSE:To improve the filling efficiency of the active material by holding alkali in a porous nickel sintered board, and thinning down the alkali concentration of the surface of the board than that of the core side, and impregnating the board with the acidic nickel salt aqueous solution. CONSTITUTION:After impregnating a board with the acidic nickel salt and performing the alkali processing to it, a part of the alkali is eliminated by the washing, and the board, of which part holds alkali, is dipped in the water for some ten seconds. The moisture thereby penetrates into the board to dilute the alkali of the surface and increase the alkali concentration near the board core body higher than that of the surface of the board. At the time of impregnating this board with the acidic nickel continuously, the conversion to nickel hydroxide is generated in the water primarily near the board core body to prevent the blinding on the surface of the board. The conversion to nickel hydroxide is generated simultaneously with the impregnation with the acidic nickel salt and the alkali processing and the next impregnation with the acidic nickel salt. Consequently, a highly concentrated nickel nitride aqueous solution or the like is not used as the impregnation liquid to perform the filling efficiently.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a hydroxide of an alkaline storage battery in which a porous nickel sintered substrate is impregnated with an acidic nickel salt such as nickel nitrate and then alkali treated to fill the substrate with an active material. The present invention relates to a method for manufacturing a nickel electrode.

[0002]

2. Description of the Related Art As a method for producing a nickel hydroxide electrode for an alkaline storage battery, a porous nickel sintered substrate, which is an active material holder, is immersed in an acidic nickel salt impregnating solution such as nickel nitrate and the like A method in which a nickel salt is impregnated and then the nickel salt is converted to nickel hydroxide in an alkali is a known and generally used production method. However, in this method, a sufficient filling amount of the active material cannot be obtained by one filling operation, and therefore these operations must be repeated in order to obtain the required filling amount of the active material. Repeating such an operation requires a great deal of time, which causes a problem of reducing productivity.

Therefore, as described in JP-A-62-58566, a molten salt impregnating solution such as a high temperature high-concentration nickel nitrate aqueous solution is used as the impregnating solution in order to increase the efficiency of the active material filling and to simplify the manufacturing process. Obtaining the required amount of active material is being carried out.

[0004]

However, when the method as described above is used, the impregnating solution naturally becomes more corrosive, and the substrate is eroded to melt the nickel constituting the substrate. Will become weak and will cause capacity deterioration when cycled. Therefore, in order to prevent the corrosion of the nickel sintered substrate, it is desirable to reduce the number of times and the time for immersing the substrate in the acidic nickel salt impregnating solution as much as possible, and obtain the required amount of active material.

According to the present invention, in the production of a nickel hydroxide electrode by repeating the active material filling operation of converting a nickel salt into an active material in an alkali, the time required for this operation is significantly reduced, and corrosion of the substrate is prevented. The purpose is to improve the filling efficiency.

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 is characterized in that an alkali is held on a nickel sintered substrate before the nickel sintered plate is immersed in an acidic nickel salt-impregnated aqueous solution. The method is characterized by having one step and a second step of making the alkali concentration on the core side higher than the alkali concentration on the substrate surface side.

[0007]

The inventor has found the following problems in the process of manufacturing the electrode. Clogging on the surface of the substrate It is known that in the process of manufacturing the electrode, the expansion of the filling amount slows as nickel hydroxide is generated by the neutralization reaction of the acidic nickel salt and the alkaline aqueous solution in the pores of the nickel sintered substrate. Has been. This is because the volume ratio of the active material in the pores of the nickel sintered substrate increases, in other words, the amount of nickel salt that can be impregnated into the substrate decreases.

Taking this into consideration, it is considered desirable to form nickel hydroxide from the deep part of the holes of the nickel sintered plate in order to most efficiently fill the active material. .. This is because if the active material is concentrated near the surface of the nickel sintered plate, the surface will be clogged and the subsequent filling operation will not be performed smoothly. Decrease in filling efficiency Normally, when performing the cycle of impregnation with acidic nickel salt and alkali treatment, after performing alkali treatment, it is washed thoroughly with water to remove the alkali content. 1 conversion per cycle
It is inefficient and inefficient.

Therefore, part of the alkali is removed by washing with water after the alkali treatment, and impregnation is performed while part of the alkali is retained in the substrate, so that nickel hydroxide can be absorbed even when impregnated with the acidic nickel salt. If the conversion is allowed to take place, there will be two conversions to nickel hydroxide per cycle. However, when converting to nickel hydroxide, nickel hydroxide produced in the reaction field with a high concentration of acidic nickel salt tends to have a lower bulk density than that produced in the reaction field with a high alkali concentration (clogging. Hard to become nickel hydroxide).

As described above, even if the impregnation is simply carried out while the alkali is retained in the substrate, the conversion into nickel hydroxide is performed twice per cycle, but nickel hydroxide having a low bulk density is formed near the surface. As a result, the surface of the substrate is clogged, and the extension of the impregnated amount becomes small.
Therefore, when the active material is filled by the method of the present invention,
It becomes as follows.

After the impregnation with the acidic nickel salt and the alkali treatment, a part of the alkali content is removed by washing with water, and a part of the alkali content is retained, and the substrate is immersed in water for several tens of seconds, whereby the moisture content in the substrate is increased. To dilute the alkali content on the surface to make the alkali concentration in the center of the substrate (near the core) higher than the alkali concentration on the surface of the electrode plate. As a result, when this substrate is subsequently impregnated with acidic nickel, conversion to nickel hydroxide in the impregnation solution occurs preferentially in the center of the substrate, preventing clogging on the substrate surface. You can Also, conversion to nickel hydroxide
At the time of the operation of impregnation into acidic nickel salt and alkali treatment,
Since this occurs at the time of impregnation with the acidic nickel salt, the impregnation liquid can be efficiently filled without using a high-concentration nickel nitrate aqueous solution or the like.

[0012]

【Example】

[Example] Carbonyl nickel, the amount of paste and water are mixed to form a slurry, and the slurry is applied to both surfaces of a core body (iron material is nickel-plated). Then, in a reducing atmosphere,
Sintering was performed to obtain porous nickel having a porosity of 80%.

This sintered substrate was immersed in a molten salt of nickel nitrate having a specific gravity of 1.75 at 80 ° C. for 30 minutes and then dried at 80 ° C. for 30 minutes to retain nickel nitrate in the substrate. After that, it was immersed in a chemical conversion soda solution having a concentration of 25% at 80 ° C. for 30 minutes, converted into nickel hydroxide, washed with water for 10 minutes to partially remove the alkali content, and then immersed in water containing no alkali content for 30 seconds. .. This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

The electrode plate thus manufactured is hereinafter referred to as an electrode plate a. [Comparative Example 1] A sintered substrate similar to that used in the above example was immersed in a molten salt of nickel nitrate having a specific gravity of 1.75 at 80 ° C for 30 minutes, and then dried at 80 ° C for 30 minutes. The nickel nitrate was retained. After that, it was dipped in a chemical conversion soda solution having a concentration of 25% at 80 ° C. for 30 minutes to be converted into nickel hydroxide, which was thoroughly washed with water to remove the alkali content.
This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

The electrode plate thus produced is referred to below as electrode plate x
Called ₁ . Comparative Example 2 The same sintered plate as that used in the above example was used.
After being immersed in a molten salt of nickel nitrate having a specific gravity of 1.75 at 0 ° C. for 30 minutes, it was dried at 80 ° C. for 30 minutes to hold nickel nitrate in the substrate. After that, it was dipped in a chemical conversion soda solution having a concentration of 25% at 80 ° C. for 30 minutes to be converted into nickel hydroxide, and washed with water for 10 minutes to partially remove the alkali content. This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

The electrode plate produced as described above is hereinafter referred to as electrode plate x
Called ₂ . [Experiment 1] The electrode plate a of the present invention and the electrode plate x _{1 of the} comparative example,
The change in the filling amount of the active material in each filling operation of the active material during the production of x ₂ was measured, and the result is shown in FIG. In addition, FIG. 1 shows the amount of the active material filled at the time of the fifth filling operation of the electrode plate x ₁ as 100.

The measurement method is as follows:
The operation of immersing the nickel substrate and converting nickel nitrate into the active material
After measuring, wash, dry and weigh.
Decided As is clear from FIG. 1, charging of the electrode plate a of the embodiment
The filling efficiency is the highest and close to 100% in the third filling operation.
In the fourth time, the filling amount was 100% or more. On the other hand, electrode plate x
₂Has a slow expansion of the filling amount, and the filling amount after the fifth treatment is 1
It was less than 00%. [Experiment 2] Next, each electrode plate a, x₁, X₂About
Then, the cross section of the electrode plate was observed by SEM.

As a result of observation, the electrode plate x ₂ was clogged on the surface. Therefore, it is considered that the filling efficiency was low as shown in the above results. The electrode plate x ₁ was not clogged, but a portion where the active material was not filled was found in the central portion (near the core) of the substrate. Regarding the electrode plate a, uniform filling of the active material was observed. [Experiment 3] Further, the electrode plate capacities were measured for these electrode plates a, x ₁ and x _{2 with} the same filling amount of the active material, and the electrode plate utilization rate was obtained. The charging / discharging conditions at the time of measuring the electrode plate capacity were such that a nickel plate was used as a counter electrode in an alkaline solution, charged at 0.2C for 8 hours, and then discharged at 1 / 3C.

The electrode plate utilization ratio is obtained by comparing the measured electrode plate capacity with
It was calculated from the following formula using the theoretical capacity calculated from the amount of the filled active material. Electrode plate utilization factor = (measured value / theoretical capacity) × 100 As a result of the measurement, no difference in electrode plate utilization factor was observed.

[0020]

As described above, according to the present invention, before the nickel sintered substrate is dipped in the acidic nickel salt-impregnated aqueous solution, the alkali is retained on the nickel sintered substrate and the alkali concentration on the core side is adjusted to the substrate surface side. By increasing the concentration relative to the alkali concentration, the filling efficiency of the filling operation of the active material could be improved.

[Brief description of drawings]

FIG. 1 is a graph showing the relationship between the number of filling operations of an active material and the filling amount of the active material.

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[Procedure amendment]

[Submission date] November 16, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be corrected] Claim 1

[Correction method] Change

[Correction content]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0004

[Correction method] Change

[Correction content]

[0004]

However, when the method as described above is used, the impregnating solution naturally becomes more corrosive, and the substrate is eroded to melt the nickel constituting the substrate. Becomes fragile and causes capacity deterioration when charging and discharging are repeated, which causes a problem. Therefore, in order to prevent the corrosion of the nickel sintered substrate, it is desirable to reduce the number of times and the time for immersing the substrate in the acidic nickel salt impregnating solution as much as possible, and obtain the required amount of active material.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

[0006]

In order to achieve the above-mentioned object, the invention of claim 1 comprises a first step of holding an alkali on a nickel sintered substrate and an alkali on the surface side of the substrate.
The second step of making the concentration thinner than the alkali concentration on the core side of the substrate, and immersing the substrate in an acidic nickel salt-impregnated aqueous solution.
It is characterized by having a third step of soaking .

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0012

[Correction method] Change

[Correction content]

[0012]

[Example] [Example] Carbonyl nickel, the amount of paste and water are mixed to form a slurry, which is applied to both surfaces of a core body (iron material is nickel-plated). Then, in a reducing atmosphere,
Sintering was performed to obtain a porous nickel sintered substrate having a porosity of 80%.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

This sintered substrate was immersed in a nickel nitrate aqueous solution having a specific gravity of 1.75 at 80 ° C. for 30 minutes and then dried at 80 ° C. for 30 minutes to retain nickel nitrate in the substrate. Then 80 ° C., is converted to nickel hydroxide immersed in caustic soda solution of 25% strength 30 minutes, after partially removing the alkali components subjected to washing 10 minutes, was immersed for 30 seconds free water alkalinity .. This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

[Procedure correction 6]

[Document name to be amended] Statement

[Correction target item name] 0014

[Correction method] Change

[Correction content]

The electrode plate thus manufactured is hereinafter referred to as an electrode plate a. [Comparative Example 1] A sintered substrate similar to that used in the above example was immersed in a nickel nitrate aqueous solution having a specific gravity of 1.75 at 80 ° C for 30 minutes, and then dried at 80 ° C for 30 minutes to form nitric acid in the substrate. Hold nickel. Then 80 ° C., 25% strength caustic
It was immersed in a soda solution for 30 minutes to convert it to nickel hydroxide, and it was thoroughly washed with water to remove the alkali content.
This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

[Procedure Amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction content]

The electrode plate thus produced is referred to below as electrode plate x
Called ₁ . Comparative Example 2 80 ° C. The same sintered board as that used in Example was immersed for 30 minutes in an aqueous solution of nickel nitrate having a specific gravity of 1.75, and dried for 30 minutes at 80 ° C., in the substrate The nickel nitrate was retained. Then 80 ° C., 25% strength caustic
It was immersed in a soda solution for 30 minutes to convert it into nickel hydroxide and washed with water for 10 minutes to remove a part of the alkali content. This series of operations was used as an active material filling operation, and this operation was repeated 5 times to prepare an electrode plate.

[Procedure Amendment 8]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

As a measuring method,causticD in soda solution
The operation of immersing the nickel substrate and converting nickel nitrate into the active material
After measuring, wash, dry and weigh.
Decided As is clear from FIG. 1, charging of the electrode plate a of the embodiment
The filling efficiency is the highest and close to 100% in the third filling operation.
In the fourth time, the filling amount was 100% or more. On the other hand, electrode plate x
₂Has a slow expansion of the filling amount, and the filling amount after the fifth treatment is 1
It was less than 00%. [Experiment 2] Next, each electrode plate a, x₁, X₂About
Then, the cross section of the electrode plate was observed by SEM.

[Procedure Amendment 9]

[Document name to be amended] Statement

[Name of item to be corrected] 0019

[Correction method] Change

[Correction content]

The electrode plate utilization ratio is obtained by comparing the measured electrode plate capacity with
It was calculated from the following formula using the theoretical capacity calculated from the amount of the filled active material. Electrode plate utilization factor = (measured value / theoretical capacity) × 100 As a result of the measurement, no difference in electrode plate utilization factor was observed. In the example, the first immersion in the nickel nitrate aqueous solution
Before dipping, make sure that the substrate is
Kel sintered substrate impregnated with nickel nitrate, then caustic saw
It is dipped into a nickel solution to convert it to nickel hydroxide, and
The substrate was immersed in a nickel nitrate aqueous solution with Lucari remaining.
Although it is immersed, alkali remains on the sintered substrate in advance.
First immersion in aqueous nickel nitrate solution
The first immersion in the nickel nitrate aqueous solution.
At this time, it can be made into an active material.

[Procedure Amendment 10]

[Document name to be amended] Statement

[Correction target item name] 0020

[Correction method] Change

[Correction content]

[0020]

As described above, according to the present invention, the alkali is held on the porous nickel sintered substrate and the alkali on the surface side of the substrate is maintained.
In the condition that the reconcentration is lower than the alkali concentration on the core side ,
By immersion in sexual aqueous nickel salt solution, could it to improve the charging efficiency of the filling operation of an active material.

Claims (1)

[Claims] 1. A first step of retaining an alkali on a nickel sintered substrate before immersing the nickel sintered plate in an acidic nickel salt-impregnated aqueous solution, and the alkali concentration on the core side relative to the alkali concentration on the substrate surface side. A method for producing a nickel hydroxide electrode for an alkaline storage battery, which comprises a second step of deepening the thickness of the battery.