JPH0567465A - Sealed-type alkaline storage battery and its manufacture - Google Patents

Abstract

PURPOSE:To suppress migration without lowering an oxygen gas absorbing function and raising a manufacturing cost, and improve a cycle property remarkably. CONSTITUTION:A separator impregnated with an alkaline electrolytic liquid is set between a negative electrode 2 having cadmium oxide as an active material and a positive electrode 1. Boric acid or at least one salt of boric acid is added to a battery and at the same time a high molecular compound having hydroxy group which carries out cross-linking reaction with the boric acid of the salt of boric acid exists in the surface and/or inside of the negative electrode.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed alkaline storage battery and a manufacturing method thereof, and more particularly to a non-sintered cadmium electrode plate used in the battery and a manufacturing method thereof.

[0002]

2. Description of the Related Art Currently, lead batteries and nickel-cadmium batteries are mainly used as secondary batteries.
Generally, nickel-cadmium storage batteries have excellent characteristics such as high rate discharge and long charging / discharging cycle life compared to lead storage batteries, and thus are widely used from small consumer products to space applications. ing. In recent years, as the performance of these devices has increased, the nickel-cadmium storage battery has been required to have longer-term reliability than ever before.

Here, the following may be considered as the cause of the life of the nickel-cadmium storage battery. Gas is generated inside the battery due to overcharging and the internal pressure of the battery rises. As a result, the safety valve is activated and the electrolyte inside is released to the outside, causing dryout. A cause of short-circuiting with the positive electrode due to the progress of so-called migration, in which cadmium is re-precipitated and accumulated in the pores of the separator by repeating the dissolution-precipitation reaction of the negative electrode active material by charging and discharging.

As for the life, the gas generated in the battery is accumulated by being placed under severe conditions such as overcharging and overdischarging more than necessary, or the chargeable capacity of the negative electrode is positive. The reason is that the negative electrode is fully charged earlier than the positive electrode at the time of charging and the hydrogen gas that cannot be consumed in the battery is generated from the negative electrode, which is so-called negative electrode control. However, since the control of the negative electrode is solved by setting the dischargeable capacity of the negative electrode larger than the dischargeable capacity of the positive electrode by an appropriate amount, this phenomenon is unlikely to occur under normal use conditions.

As a result, in the present situation, the main cause is that the charge / discharge cycle is reduced. In particular, in recent years, in a battery using a paste-type negative electrode, which is becoming mainstream because it can easily achieve high energy density and low cost, migration is more likely to occur than in a conventionally used sintered negative electrode. Remarkably occurs. this is,
In the sintering method, the active material is held in a matrix of sintered metal, whereas in the paste method, the matrix is not provided, so an organic material such as a paste is used to bind the active material. Due to. Such an organic material oxidizes or decomposes as the charging / discharging cycle progresses, so that it no longer fulfills its original function of fixing the active material in the electrode plate, which causes migration. .. Then, in particular, when the packing density of the active material is increased in order to achieve high capacity, the fluctuation of the active material volume during charge / discharge becomes large, and the migration is accelerated.

Therefore, in order to prevent such a short circuit due to migration, the following method has been proposed. A method of increasing the thickness of the separator or reducing the pores of the separator. A method of adding quaternary ammonium to an electrolytic solution as disclosed in JP-A-50-91728. As disclosed in JP-A-56-32744, a method of adding an alkali metal salt of silicic acid to an electrolytic solution (however, in this publication, a sintered negative electrode is used). As disclosed in JP-A-2-90461, a method in which a negative electrode is negatively decomposed in a nickel solution to form a porous nickel layer on the surface, and a magnesium compound is further added.

[0007]

However, each of the above methods has the following problems. Problem of Method When the thickness of the separator is increased, the volume occupied by the separator in the battery increases, and the volume occupied by the electrode decreases. Therefore, the total amount of active material is reduced, and the energy density of the battery is reduced. On the other hand, if the thickness is increased within a practical range, the cycle characteristics cannot be significantly improved.

If the pores of the separator are reduced,
Since gas permeation is prevented, oxygen gas generated from the positive electrode does not reach the negative electrode after the battery is fully charged, and oxygen gas cannot be consumed in the negative electrode. As a result, the battery internal pressure increases and the battery performance decreases. Problem in the method of 1) When quaternary ammonium is added, oxygen gas cannot be absorbed efficiently, and the pressure inside the battery also increases and the battery performance deteriorates. In the method of adding a silicate, a sufficient effect cannot be obtained by the paste method and the active material is changed into an inactive plate crystal, so that a battery dominated by the negative electrode is likely to be obtained. As a result, the capacity and operating voltage are reduced. Problems in the method of (1), the manufacturing process becomes complicated, and the electric power equipment for performing the electroplating is required, so that the manufacturing cost rises.

The present invention has been made in consideration of the present situation, and it is possible to solve the problems described in (1) to (3) and to suppress migration and dramatically improve cycle characteristics, and a sealed alkaline storage battery. The purpose is to provide a manufacturing method.

[0010]

In order to achieve the above object, the present invention uses the following means. In a sealed alkaline storage battery having a structure in which a separator impregnated with an alkaline electrolyte is arranged between a negative electrode containing cadmium oxide as a main active material and a positive electrode, boric acid is provided on the surface and / or inside of the negative electrode. Alternatively, there is a cross-linking reaction product formed by a cross-linking reaction between a borate and a polymer compound having a hydroxyl group. A step of preparing a plate by holding a paste containing cadmium oxide as a main active material on an active material holder, and a surface having a hydroxyl group that causes a cross-linking reaction with boric acid or borate on the surface of the plate. The method is characterized by including a step of allowing a molecular compound to exist and a step of cross-linking the polymer compound with boric acid or borate. A cadmium oxide that is a main active material, and a paste containing a polymer compound having a hydroxyl group that causes a cross-linking reaction with boric acid or borate, a step of holding an active material holder to prepare an electrode plate, The method is characterized by comprising a step of causing a cross-linking reaction with the polymer compound and boric acid or borate. A step of preparing a paste containing a cadmium oxide which is a main active material, boric acid or a borate, and a polymer compound having a hydroxyl group which causes a crosslinking reaction with the boric acid or the borate, and the paste. And a step of producing an electrode plate by holding it on an active material holder. A step of producing a plate by holding a paste containing cadmium oxide as a main active material on an active material holder, and boric acid or borate, and boric acid or borate on the surface of the plate. And a step of allowing a polymer compound having a hydroxyl group that causes a crosslinking reaction to be present.

[0011]

In the experiments conducted by the present inventors, it was found that the migration of cadmium largely depends on the surface condition of the negative electrode. Specifically, for example, it was confirmed that by forming a thin film of a polymer compound on the surface of the negative electrode, it is possible to effectively prevent cadmium from moving to the separator. This is because the thin film formed on the negative electrode surface prevents the diffusion of the intermediate to the separator in the process of diffusing and depositing the intermediate of cadmium which is generated by the charge / discharge reaction and is soluble in the electrolytic solution. Considering such a fact, it is considered that the migration of cadmium can be sufficiently suppressed by applying the conventionally used PVA or the like to the surface of the negative electrode. However, the thin film made of PVA or the like may be oxidized by oxygen gas generated during charging, or may be destroyed due to a temperature rise during charging / discharging of the battery. Therefore, it is difficult to maintain the above effects for a long period of time.

However, in the above constitution, the polymer compound existing on the surface and / or inside of the negative electrode causes a cross-linking reaction with boric acid or borate in the battery. According to the experiments conducted by the present inventors, it was confirmed that the cross-linking reaction product produced by the cross-linking reaction between boric acid and the like and the polymer compound is extremely excellent in decomposition resistance. Therefore, with the above structure, the cross-linking reaction product formed on the surface and / or inside the negative electrode is not easily destroyed even when the battery is charged / discharged, and thus the effect of suppressing migration can be maintained for a long time. ..
As a result, the charge / discharge cycle life of the battery can be dramatically improved.

The polymer compound having a hydroxyl group that causes a cross-linking reaction with boric acid or borate is not limited to PVA, and the same effect can be obtained by using an ethylene-vinyl copolymer. However, sizing agents such as methyl cellulose, carboxymethyl cellulose and hydroxyprocellulose do not cause a crosslinking reaction with boric acid and the like, and thus are not included in the present invention.

Further, the sealed alkaline storage battery having the above-mentioned structure can be manufactured by the following manufacturing methods.

[0015]

【Example】

(First Embodiment) An embodiment of the present invention will be described below with reference to FIGS. [Embodiment] FIG. 1 shows a sealed nickel according to an example of the present invention.
FIG. 1 is a cross-sectional view of a cadmium storage battery, in which a known nickel positive electrode 1, a negative electrode 2 mainly containing cadmium oxide, and a separator 3 interposed between the positive and negative electrodes 1 and 2 are spirally wound. It has been turned. The electrode group 4 is arranged in an outer casing 6 which also serves as a negative electrode terminal.
The negative electrode 2 and the negative electrode 2 are connected by a negative electrode conductive tab 5. A sealing body 8 is attached to the upper opening of the outer casing 6 via a packing 7, and a coil spring 9 is provided inside the sealing body 8. The coil spring 9 is configured to be pressed in the direction of arrow A when the internal pressure inside the battery is abnormally increased, and the gas inside is released into the atmosphere. Further, the sealing body 8 and the positive electrode 1 are connected by a positive electrode conductive tab 10.

Here, the sealed nickel-cadmium storage battery having the above structure was manufactured as follows. First, 800 g of cadmium oxide as an active material, 200 g of cadmium metal as a precharge active material, 10 g of hydroxypropylcellulose as a paste, 10 g of nylon fiber as a reinforcing agent, and a 5% sodium phosphate aqueous solution 4
00g was kneaded to prepare a paste. Next, this paste is applied to both surfaces of nickel-plated punching metal (thickness: 0.08 mm) as an active material holder,
An electrode plate was produced by applying a coating having a thickness of 0.3 mm, drying, and cutting into a predetermined size. Then, the electrode plate was hydrated by immersing it in an aqueous sodium hydroxide solution having a specific gravity of 1.23 and a temperature of 30 ° C. for 2 hours to change the cadmium oxide to cadmium hydroxide. After that, a 5% aqueous solution of polyvinyl alcohol (PVA), which is a polymer compound, was applied to the surface of this electrode plate to form a polymer compound layer, thereby preparing a cadmium negative electrode. The ratio of the polymer compound layer in the last step is set to be about 4 mg per 1 g of the active material.

After that, the cadmium negative electrode and a known nickel positive electrode are wound around a separator to form an electrode group, and then the electrode group is inserted into a battery can. Finally, an aqueous potassium hydroxide solution having a specific gravity of 1.3 containing 0.1 mol / l orthoboric acid was poured into the battery can, and the battery can was further sealed to produce a battery having a nominal capacity of 1.5 AH. did.

The battery thus manufactured is hereinafter referred to as (A) battery. [Comparative Example 1] A battery was produced in the same manner as in the above-described example except that the polymer compound layer was not formed on the surface of the electrode plate. The battery thus manufactured is hereinafter referred to as a (W ₁ ) battery. [Comparative Example 2] A battery was produced in the same manner as in the above-described example except that orthoboric acid was not added to the electrolytic solution (the electrolytic solution was composed of potassium hydroxide only).

The battery thus produced is
₂ ) Called battery. [Comparative Example 3] A battery was produced in the same manner as in the above-described example except that the polymer compound layer was not formed on the surface of the electrode plate and orthoboric acid was not added to the electrolytic solution. The battery thus manufactured is hereinafter referred to as a (W ₃ ) battery. [Experiment 1] (A) battery of the present invention and (W ₁ ) of a comparative example
Since the cycle characteristics were examined in the cell ~ (W ₃₎ batteries, and the results are shown in Figure 2. The experimental condition is 150m
1.5A after charging for 16 hours with A (0.1C) current
The condition is that the battery is discharged with the current (1C) until the battery voltage reaches 0.8V.

As is apparent from FIG. 2, (A) of the present invention.
The battery is a comparative example (W₁) Battery ~ (W ₃) Compared to batteries,
It can be seen that the cycle characteristics are remarkably improved. [Experiment 2] The (A) battery of the present invention and the comparative example (W)₁)
Battery ~ (W₃) 50 and 100 cycles with batteries
After the lapse of time, measure the amount of cadmium contained in the separator.
Therefore, the result is shown in FIG. The experiment is for each cycle
The battery separator, remove the separator from each battery and
Was immersed in hydrochloric acid and heated to dissolve cadmium
Then, the amount of metal cadmium was measured by atomic absorption spectrometry.

As is apparent from FIG. 3, (A) of the present invention.
It is recognized that the amount of cadmium in the separator used in the battery is significantly reduced as compared with the amount of cadmium in the separator used in the (W ₁ ) battery to the (W ₃ ) battery of Comparative Example. Further, when the separator of each battery was visually observed, the separator used in the battery (A) of the present invention showed almost no stain due to the adhesion of cadmium, but the separators (W ₁ ) to (W ₃ ) of the comparative example were observed. ) Cadmium contamination was confirmed in the separator used in the battery.

From the above experimental results, in the batteries (W ₁ ) to (W ₃ ) of the comparative examples, migration due to cadmium occurs, so that the cadmium penetrates the separator to short-circuit the positive electrode and the negative electrode, and the cycle characteristics are improved. descend. On the other hand, in the battery (A) of the present invention, since migration due to cadmium is suppressed, it is possible to prevent cadmium from penetrating the separator and short-circuiting the positive electrode and the negative electrode, and as a result, cycle characteristics are improved. It is expected to improve. [Other Matters] Although the addition amount of boric acid (orthoboric acid) was set to 0.1 mol / l in the above-mentioned examples, the present invention is not limited to this and may be in the range of 0.01 to 0.5 mol / l. The same effect as in the above embodiment is obtained. In addition to orthoboric acid, experiments have confirmed that oxides such as boron trioxide and borates such as borax have similar effects. When a conductive powder such as acetylene black or nickel is added to the polyvinyl alcohol layer when producing the cadmium negative electrode used in the battery (A) of the present invention, not only cycle characteristics but also oxygen gas absorption characteristics are improved. You can When PVA is present on the surface of the negative electrode as in the above example, a method of applying to the surface of the separator in contact with the negative electrode can be adopted in addition to the above-mentioned application to the surface of the negative electrode. Also has the same effect.

(Second Embodiment) [Example] First, 90 parts by weight of cadmium oxide, 10 parts by weight of metal cadmium, 0.5 part by weight of acrylic short fibers, 0.8 part by weight of PVA, and 5% phosphoric acid. A paste was prepared by kneading 40 parts by weight of an aqueous sodium solution and 0.2 parts by weight of boric acid. Next, this paste was applied to both sides of a nickel-plated punching metal, dried, and then cut into a predetermined size to prepare a cadmium negative electrode.

Thereafter, the above-mentioned cadmium negative electrode and a known nickel positive electrode are wound around a separator to produce an electrode group, which is then inserted into a battery can. Finally, an alkaline electrolyte solution (aqueous solution of potassium hydroxide having a specific gravity of 1.3) was poured into the battery can, and the battery can was further sealed to manufacture a battery having a nominal capacity of 1.5 AH. The battery thus manufactured is hereinafter referred to as (B) battery.

The main differences between the battery (B) and the battery (A) shown in the first embodiment are as shown in Table 1 below.

[0026]

[Table 1]

Comparative Example A battery was manufactured in the same manner as in the above-mentioned example except that boric acid was not added to the paste. The battery thus manufactured is hereinafter referred to as (X) battery. .. [Experiment 1] The cycle characteristics of the battery (B) of the present invention and the battery (X) of the comparative example were examined. The results are shown in FIG. The experimental condition is that the battery is charged with a current of 1.5 A (1 C) for 90 minutes and then discharged with a current of 1.5 A (1 C) until the battery voltage reaches 1.0 V.

As is apparent from FIG. 4, (B) of the present invention.
It is recognized that the battery has markedly improved cycle characteristics as compared with the battery (X) of the comparative example. [Experiment 2] In the battery (B) of the present invention and the battery (X) of the comparative example, the amount of cadmium contained in the separator was measured after 100 cycles, and the results are shown in Table 2. The experiment was conducted in the same manner as the experiment 2 of the first embodiment.

[0029]

[Table 2]

As is clear from Table 2, (B) of the present invention
It is recognized that the amount of cadmium in the separator used in the battery is significantly reduced as compared with the amount of cadmium in the separator used in the battery (X) of the comparative example. Therefore, in the battery (B) of the present invention, since migration due to cadmium is suppressed, it is considered that the cycle characteristics are improved as shown in Experiment 1 above. [Other Matters] In the above embodiment, the addition amount of boric acid was set to 0.
02 parts by weight, but not limited to this
If it is in the range of 0.01 to 1 part by weight, the same effect as that of the above-mentioned embodiment can be obtained. Moreover, it has been confirmed by experiments that the same effect as described above can be obtained by using borate instead of boric acid.

(Third Example) [Example 1] A battery having a nominal capacity of 1.5 AH was produced in the same manner as the example of the second example except that a cadmium negative electrode was produced as follows. .. The battery thus manufactured is hereinafter referred to as a (C ₁ ) battery.

First, the same paste as in Example 1 of the second embodiment was prepared except that boric acid was not contained, the paste was applied to both surfaces of nickel-plated punching metal, and further dried. , The electrode plate was produced. Next, this electrode plate was immersed in an aqueous sodium hydroxide solution having a specific gravity of 1.23 and a temperature of 30 ° C. for 1 hour for hydration treatment, and then washed with water to remove alkali. Then, this electrode plate was added to 0.5 mol / l
After immersing in the boric acid aqueous solution for 1 minute, it is completely dried in air at 80 ° C. Finally, this electrode plate was cut into a predetermined size to prepare a cadmium negative electrode. The amount of boric acid taken into the cadmium negative electrode was 1.4 mg per 1 g of the active material. Example 2 A battery was produced in the same manner as in Example 1 except that chemical conversion treatment was applied instead of hydration treatment. The conditions for the chemical conversion treatment are as follows: in an aqueous solution of potassium hydroxide, after charging for 15 hours at a current of 0.1 C based on the capacity of the electrode plate,
The condition is that the battery is completely discharged with a current of 0.2C. The amount of boric acid taken into the cadmium negative electrode was 1.4 mg per 1 g of the active material.

The battery prepared in this manner is described below (C
₂ ) Called battery. The main differences between the (C ₁ ) battery and the (C ₂ ) battery and the (A) battery shown in the first embodiment are as shown in Table 3 below.

[0034]

[Table 3]

[Comparative Examples 1 and 2] Batteries were prepared in the same manner as in Examples 1 and 2 except that they were not immersed in an aqueous boric acid solution. The batteries thus manufactured are hereinafter referred to as (Y ₁ ) battery and (Y ₂ ) battery, respectively. [Experiment 1] The cycle characteristics of the (C ₁ ) battery and (C ₂ ) battery of the present invention and the (Y ₁ ) battery and (Y ₂ ) battery of the comparative example were examined. The results are shown in FIG. .. In addition, the experimental condition was that the charging voltage passed a peak voltage at a current of 1.5 A (1 C) and was charged until the voltage dropped below 10 mV peak voltage, and then the battery voltage was 1.0 V at a current of 1.5 A (1 C).
The condition is that the discharge is performed until.

As is apparent from FIG. 5, the (C ₁ ) battery and the (C ₂ ) battery of the present invention are the (Y ₁ ) battery of the comparative example,
It is recognized that the cycle characteristics are remarkably improved as compared with the (Y ₂ ) battery. [Experiment 2] In the (C ₁ ) battery and (C ₂ ) battery of the present invention and the (Y ₁ ) battery and (Y ₂ ) battery of Comparative Example, 10
The amount of cadmium contained in the separator was measured after the lapse of 0 cycle, and the results are shown in Table 4. The experiment is
The experiment was carried out in the same manner as Experiment 2 of the first embodiment.

[0037]

[Table 4]

As is clear from Table 4, the amount of cadmium in the separator used in the (C ₁ ) battery and the (C ₂ ) battery of the present invention was the same as that in the comparative (Y ₁ ) battery and (Y ₂ ) battery. Compared to the amount of cadmium in the separator used,
It is recognized that the number has decreased significantly. Therefore, in the (C ₁ ) battery and the (C ₂ ) battery of the present invention, the migration due to cadmium is suppressed, and it is considered that the cycle characteristics are improved as shown in Experiment 1 above. [Other Matters] The amount of boric acid added to the electrode plate depends on the amount of active material 1
Although the effect can be seen by adding 0.2 mg per g, if the amount of boric acid brought into the electrode plate increases, the concentration of the battery electrolyte will decrease. Therefore, the amount of boric acid added is preferably about 10 mg per 1 g of the active material.

Fourth Example [Example 1] A battery was produced in the same manner as in the second example except that a cadmium negative electrode was produced as follows. However, the nominal capacity is 1.0 AH. The battery thus manufactured is hereinafter referred to as a (D ₁ ) battery.

First, 80 parts by weight of cadmium oxide, 20 parts by weight of metal cadmium, and 1 part by weight of short nylon fiber,
1 part by weight of hydroxypropyl cellulose and 40 parts by weight of a 5% sodium phosphate aqueous solution were kneaded to prepare a paste. Next, this paste was applied to both sides of a nickel-plated punching metal and dried to prepare an electrode plate. Then, a 10% PVA aqueous solution was applied to the surface of this electrode plate and further dried to form a PVA thin film on the surface of the electrode plate. Then, the electrode plate is immersed in a sodium hydroxide aqueous solution having a specific gravity of 1.28 for 1 hour to perform a hydration treatment. Finally, the electrode plate was immersed for 30 minutes in a solution of boric acid dissolved in an aqueous solution of sodium hydroxide having a specific gravity of 1.28 for 30 minutes, washed with water and dried to prepare a cadmium negative electrode. [Example 2] A battery was produced in the same manner as in Example 1 except that the cadmium negative electrode was produced as follows.

The battery thus prepared is
₂ ) Called battery. First, an electrode plate before applying the PVA aqueous solution in the above example was prepared, and the film forming solution was applied to the surface of the electrode plate. This film forming solution was prepared by mixing 100 parts by weight of a 10% PVA aqueous solution and 100 parts by weight of a 3% boric acid aqueous solution. Since this solution thickens and gels when left standing after mixing, it was rapidly applied while being heated to 60 ° C. so that it could be applied uniformly to the surface of the electrode plate. Then, after that, the electrode plate was dried to produce a cadmium negative electrode.

The main differences between the (D ₁ ) battery and the (D ₂ ) battery and the (A) battery shown in the first embodiment are as shown in Table 5 below.

[0043]

[Table 5]

Comparative Example 1 A battery was manufactured in the same manner as in Example 2 except that boric acid was not added to the film forming solution. The battery thus manufactured is hereinafter referred to as a (Z ₁ ) battery. [Comparative Example 2] A battery was produced in the same manner as in Example 2 except that nothing was applied to the surface of the electrode plate.

The battery thus produced is described below (Z
₂ ) Called battery. [Experiment 1] The cycle characteristics of the (D ₁ ) battery and (D ₂ ) battery of the present invention and the (Z ₁ ) battery and (Z ₂ ) battery of the comparative example were examined. The results are shown in FIG. .. The experimental conditions were as follows: the charging voltage passed the peak voltage at a current of 1.0 A (1 C) and then charged until it dropped below 10 mV peak voltage, and then the battery voltage was 1.0 V at a current of 1.0 A (1 C).
The condition is that the discharge is performed until.

As is apparent from FIG. 6, the (D ₁ ) battery and the (D ₂ ) battery of the present invention are the (Z ₁ ) battery of the comparative example,
It is recognized that the cycle characteristics are remarkably improved as compared with the (Z ₂ ) battery. In addition, when the (Z ₁ ) battery and the (Z ₂ ) battery of Comparative Examples were disassembled at the end of their life and investigated, an internal short circuit occurred due to the progress of migration in all the batteries. [Experiment 2] The amount of cadmium contained in the separator in each of the (D ₁ ) battery and (D ₂ ) battery of the present invention and the (Z ₁ ) battery and (Z ₂ ) battery of Comparative Example was measured [every 100 cycles. The measurement was performed up to 400 cycles], and the results are shown in FIG. 7. The experiment was conducted in the same manner as the experiment 2 of the first embodiment.

As is apparent from FIG. 7, the amount of cadmium in the separator used in the (D ₁ ) battery and the (D ₂ ) battery of the present invention was the same as that in the comparative (Z ₁ ) battery and the (Z ₂ ) battery. Compared to the amount of cadmium in the separator used,
It is recognized that the number has decreased significantly. Therefore, in the (D ₁ ) battery and the (D ₂ ) battery of the present invention, since the migration due to cadmium is suppressed, it is considered that the cycle characteristics are improved as shown in Experiment 1 above.

In the comparative (Z ₂ ) battery in which the PVA film was not formed on the surface, the amount of cadmium increased from the beginning of the cycle, but in the comparative (Z ₁ ) battery, it was about 200 cycles. Until the increase in the amount of cadmium is suppressed. This is because the PVA film is formed in the (Z ₁ ) battery. However, even in the case of the (Z ₁ ) battery, the amount of cadmium increases remarkably after 200 cycles. It is considered that this is because the PVA film is destroyed after 200 cycles. [Other Matters] In Example 1, the case where the negative electrode is treated with an aqueous solution of boric acid or the like after the hydration treatment is described, but the same effect as above can be obtained by treating with boric acid or the like before the hydration treatment. There is. This also applies to the case where the chemical conversion treatment is performed instead of the hydration treatment. In Example 1, immersion in a sodium hydroxide solution in which boric acid is dissolved to cause a crosslinking reaction is followed by washing with water, and this washing with water removes excess boric acid that did not participate in the crosslinking reaction. It is possible to prevent the conductivity of the electrolytic solution from being lowered due to the mixture of boric acid inside the battery. In Example 2, when the amount of boric acid in the film-forming solution was too large, PVA gelated as described above, the film-forming solution could not be uniformly applied to the surface of the electrode plate, and excess boric acid was contained in the electrolytic solution. And elutes into the electrolyte to lower the electric conductivity of the electrolytic solution. On the other hand, if the amount of boric acid in the film-forming solution is too small, the strength of the film decreases and the effect of suppressing migration cannot be sufficiently exerted. Therefore, it is necessary to add boric acid within the range where such an adverse effect does not occur. In Example 2, the viscosity of the film-forming solution and the presence or absence of gelation during boric acid addition depend on the degree of polymerization of PVA, the degree of saponification, the concentration of the aqueous solution, etc. Should be decided. When producing the batteries shown in Comparative Example 1 and Comparative Example 2,
Even when the negative electrode was hydrated, the same experimental results as in Comparative Example 1 and Comparative Example 2 were obtained.

[0049]

As described above, according to the present invention, since a thin film having extremely excellent decomposition resistance exists on the surface of the negative electrode, it is possible to suppress the migration of cadmium for a long period of time. As a result, there is an excellent effect that the charge / discharge cycle life of the battery can be dramatically improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a sealed nickel-cadmium storage battery according to an example of the present invention.

FIG. 2 shows the battery (A) of the present invention and the battery (W ₁ ) of the comparative example.
(W ₃₎ is a graph showing the cycle characteristics of the battery.

FIG. 3 shows the battery (A) of the present invention and the battery (W ₁ ) of the comparative example.
(W ₃₎ in the battery, is a graph showing the relationship between the amount of cadmium number of charge and discharge cycles and the separator.

FIG. 4 is a graph showing cycle characteristics of the battery (B) of the present invention and the battery (X) of the comparative example.

FIG. 5 is a graph showing cycle characteristics of the (C ₁ ) battery and (C ₂ ) battery of the present invention and the (Y ₁ ) battery and (Y ₂ ) battery of Comparative Example.

FIG. 6 is a graph showing cycle characteristics of the (D ₁ ) battery and the (D ₂ ) battery of the present invention and the (Z ₁ ) battery and the (Z ₂ ) battery of the comparative example.

FIG. 7 shows the relationship between the number of charge / discharge cycles and the amount of cadmium in the separator in the (D ₁ ) battery and (D ₂ ) battery of the present invention and the (Z ₁ ) battery and (Z ₂ ) battery of Comparative Example. It is a graph shown.

[Explanation of symbols]

 1 Nickel positive electrode 2 Cadmium negative electrode 3 Separator

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[Procedure amendment]

[Submission date] March 6, 1992

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction content]

The polymer compound having a hydroxyl group that causes a cross-linking reaction with boric acid or borate is not limited to PVA, and the same effect can be obtained by using an ethylene-vinyl alcohol copolymer. However, sizing agents such as methyl cellulose, carboxymethyl cellulose and hydroxyprocellulose do not cause a crosslinking reaction with boric acid and the like, and thus are not included in the present invention.

Claims (5)

[Claims] 1. A sealed alkaline storage battery having a structure in which a separator impregnated with an alkaline electrolyte is arranged between a negative electrode containing cadmium oxide as a main active material and a positive electrode, and the surface of the negative electrode and / or A sealed alkaline storage battery, characterized in that a cross-linking reaction product formed by a cross-linking reaction between boric acid or borate and a polymer compound having a hydroxyl group is present inside. 2. A step of preparing an electrode plate by holding a paste containing cadmium oxide as a main active material on an active material support, and a cross-linking reaction with boric acid or borate on the surface of the electrode plate. A method for producing a sealed alkaline storage battery, comprising: a step of allowing a polymer compound having a hydroxyl group to be formed to be present; and a step of cross-linking the polymer compound and boric acid or borate. 3. An active material holder is made to hold | maintain the paste containing the cadmium oxide which is a main active material, and boric acid or borate, and the high molecular compound which has a hydroxyl group which produces a crosslinking reaction, and an electrode plate is hold | maintained. A method for producing a sealed alkaline storage battery, comprising: a step of producing the polymer compound; and a step of crosslinking the polymer compound with boric acid or borate. 4. A step of producing a paste containing cadmium oxide as a main active material, boric acid or borate, and a polymer compound having a hydroxyl group that causes a crosslinking reaction with the boric acid or borate. And a step of holding the paste on an active material holder to produce an electrode plate, a method for producing a sealed alkaline storage battery. 5. A step of preparing an electrode plate by holding a paste containing cadmium oxide as a main active material on an active material holder, and boric acid or borate on the surface of the electrode plate, and the boron A step of allowing a polymer compound having a hydroxyl group that causes a crosslinking reaction with an acid or a borate to be present, and a method for producing a sealed alkaline storage battery.