JPH0896830A - Manufacture of alkaline secondary battery - Google Patents

Abstract

PURPOSE: To accurately pour a specified amount of an alkaline electrolyte in a short time by pouring the electrolyte by dividing into the number of specified times in a metal case in which an electrode group is put and conducting the final pouring while the centrifugal force is applied in the direction of the bottom of the metal case. CONSTITUTION: In the manufacture of an alkaline secondary battery, an alkaline electrolyte is poured in a metal case in which an electrode group is put by dividing the amount of the electrolyte to be poured into at least two times. The final pouring is conducted in such a way that the metal case is fixed to a holding means, the alkaline electrolyte is put into a funnel, a turn table is rotated, thereby, the funnel and the holding means are inclined in the direction apart from the turn table, centrifugal force is applied to the electrolyte in the direction of the bottom of the metal case, and the electrolyte is poured in the metal case. Thereby, the alkaline electrolyte is accurately poured in a short time.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing an alkaline secondary battery provided with a paste type electrode, and more particularly to a method of manufacturing an alkaline secondary battery having an improved electrolyte injection step.

[0002]

2. Description of the Related Art A prismatic nickel-hydrogen secondary battery, which is an example of an alkaline secondary battery, is manufactured by the following method.
First, a nickel salt solution is impregnated into a sintered substrate produced by molding and sintering carbonyl nickel powder,
By forming this, a sintered nickel positive electrode is manufactured. Further, a sheet containing a hydrogen storage alloy as an active material, a conductive powder made of, for example, carbon black, and polytetrafluoroethylene is produced, and the sheet is pressed onto a nickel net to produce a dry negative electrode. Between the positive electrode and the negative electrode, a separator made of, for example, a non-woven fabric made of polyolefin fiber having a hydrophilic functional group is interposed, and a plurality of the laminates are stacked to form an electrode group. After the electrode group is housed in a rectangular metal case, for example, an alkaline electrolyte containing potassium hydroxide as a main component is injected. Then, the secondary battery is manufactured by sealing the opening of the metal case with a sealing lid having a safety valve mechanism.

As a method of injecting the alkaline electrolyte into the secondary battery that does not contain the electrolyte, the following methods have been conventionally known. (1) After accommodating the entire amount of the alkaline electrolyte in the funnel, a metal case accommodating the electrode group is arranged below the funnel. Then, a centrifugal force is applied to the alkaline electrolyte in the funnel in a direction toward the metal case to inject the electrolyte into the metal case. (2) A method in which the alkaline electrolyte is divided into two or more parts and injected into the metal case accommodating the electrode group by a constant-rate discharge pump.

By the way, in recent years, the demand for higher capacity of the secondary battery is increasing. Therefore, in the secondary battery, the amount of the active material is increased by using the pasted nickel positive electrode or the pasted hydrogen storage alloy negative electrode instead of the sintered nickel positive electrode or the dry hydrogen storage alloy negative electrode. Is being done. These paste-type electrodes are prepared by preparing a paste containing an active material and a binder, filling the conductive substrate with the paste, and then drying and rolling the paste. Moreover, the volume of the electrode group housed in the metal case is increased.

However, since the paste type electrode absorbs the alkaline electrolyte more easily than the sintered type positive electrode and the dry type negative electrode, the secondary battery provided with the electrode group having the paste type electrode has a charge / discharge cycle. There is a risk that the alkaline electrolyte contained in the separator will move to the paste-type electrode with the progress of the above, and the electrolyte in the separator will be depleted. Therefore, the secondary battery including the electrode group including the paste-type electrode needs to have a larger amount of electrolytic solution than the secondary battery including the electrode group including the sintering-type positive electrode and the dry-type negative electrode. . Further, when the volume of the electrode group housed in the metal case is increased, the void volume in the metal case is reduced, so that the electrode group housed in the metal case becomes difficult to absorb the electrolytic solution.

Therefore, as in the method (1) described above, centrifugal force is applied to the alkaline electrolyte in the funnel to inject the entire amount of the electrolyte at once into the metal case containing the electrode group having the paste type electrode. However, since the electrolytic solution permeation rate of the electrode group is slow, there is a problem that the alkaline electrolytic solution does not permeate into the electrode group and the electrolytic solution overflows from the metal case. As a result, there is a problem in that the amount of the electrolytic solution accommodated in the metal case is reduced and the cycle life of the secondary battery is reduced. Further, when the alkaline electrolyte overflows from the metal case and adheres to the inner surface of the opening of the metal case, the inner surface becomes dirty, which makes it difficult to attach the sealing lid to the inner surface with good airtightness. there were.

Further, as in the method (2) described above, the alkaline discharge solution is divided into two or more times in a metal case containing an electrode group having an electrode group having the above-mentioned paste type electrode, and the constant amount discharge pump is provided. When the injection is performed by the method described above, since the electrolyte solution permeation rate of the electrode group is slow, the number of divisions is significantly increased. Therefore, it takes a long time to inject the electrolytic solution, and the production efficiency of the secondary battery is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made to solve the conventional problems, and it is possible to inject a predetermined amount of an alkaline electrolyte solution into an alkaline secondary battery containing no electrolyte solution accurately and in a short time. The present invention is intended to provide a method for manufacturing an alkaline secondary battery.

[0009]

SUMMARY OF THE INVENTION The present invention is directed to an electrode group housed in a metal case and made by interposing a separator between a positive electrode and a negative electrode, and an alkaline electrolyte housed in the metal case. In the method for manufacturing an alkaline secondary battery, wherein one or both of the positive electrode and the negative electrode have a structure in which a conductive substrate is filled with a paste containing an active material and a hydrophilic binder, In the alkaline secondary battery, the alkaline electrolyte is injected into the metal case, in which the alkaline electrolyte is stored, divided into two or more times, and the final injection is performed while applying a centrifugal force that acts in the bottom direction of the metal case. It is a manufacturing method.

The final injection, which is performed while applying a centrifugal force that acts toward the bottom of the metal case, means the injection performed by the following method. An apparatus provided with a funnel tiltably supported on a rotary table and a holding means arranged below the funnel and for holding the metal case accommodating the electrode group is used, wherein the holding means is After mounting the metal case, the funnel contains an alkaline electrolyte.
When the rotary table is rotated in this state, the funnel and the holding means are tilted in a direction away from the rotary table, and the funnel and the holding means are oriented in a substantially horizontal direction. At this time, a centrifugal force toward the bottom of the metal case is applied to the electrolyte solution in the funnel, so that the electrolyte solution is injected into the metal case.

The final injection is preferably performed in a state where the alkaline electrolyte has permeated 80% by volume or more of the voids in the positive electrode and the voids in the negative electrode. If the ratio of the voids permeated with the alkaline electrolyte to the voids in the positive electrode and the voids in the negative electrode is less than 80% by volume, the alkaline electrolyte may overflow from the metal case. More preferably, the final injection is performed in a state where the alkaline electrolyte has permeated into all the voids in the positive electrode and the negative electrode.

In order to improve the ratio of the voids in which the alkaline electrolyte has permeated to the voids in the positive electrode and the voids in the negative electrode, a process of leaving the inside of the metal case under a reduced pressure immediately before the final injection step Is preferably performed. After such processing, the inside of the metal case is returned to normal pressure and the final injection is performed into the metal case.

In an injection step other than the final injection step, for example, a method of performing the injection while applying a centrifugal force that acts in the bottom direction of the metal case, a vacuum in the metal case, and a negative pressure is applied to the metal case to perform alkaline electrolysis. A method of injecting a liquid or a method of injecting an alkaline electrolyte into the metal case with a constant-rate discharge pump can be used. Among them, the method of using the centrifugal force has a higher accuracy than the method of using a negative pressure, and a predetermined amount of the alkaline electrolyte in the metal case in a shorter time than the method of injecting using the constant amount discharge pump. It is preferable because it can be injected.

From the viewpoint of finishing the electrolyte injection work in a short time and improving the production efficiency of the secondary battery, it is preferable to inject the alkaline electrolyte twice or three times, and more preferably. It is twice.

When the alkaline electrolyte is injected into the prismatic alkaline secondary battery not containing the electrolyte in two divided doses, the first injection amount may be 40% by volume to 85% by volume of the total injection amount. preferable. This is due to the following reasons. When the amount of the first injection is less than 40% by volume of the total amount of injection, the ratio of the voids permeated with the alkaline electrolyte to the voids in the positive electrode and the negative electrode is 80.
It may be less than volume%. On the other hand, if the injection amount of the first injection exceeds 85% by volume of the total injection amount, the air in the voids of the positive electrode and the negative electrode is difficult to be released to the outside even if the metal case is left after the injection. It may be difficult to penetrate the electrolyte solution therein. The first injection amount is more preferably 60% by volume to 80% by volume of the total injection amount. When the alkaline electrolyte is injected into the cylindrical alkaline secondary battery that does not contain the electrolyte in two divided injections, the first injection amount is preferably 40 times the total injection amount for the same reason as described above. Volume% to 70 volume%,
More preferably, it is 50% to 60% by volume of the total injection amount.

A prismatic nickel-hydrogen secondary battery, which is an example of an alkaline secondary battery manufactured by the method according to the present invention, will be described below with reference to FIG. An electrode group 2 is housed in a bottomed rectangular metal case 1 that also serves as a negative electrode terminal. The electrode group 2 is formed by alternately stacking a hydrogen storage alloy negative electrode 3 and a nickel positive electrode 5 wrapped with a bag-shaped separator 4. The negative electrode 3 is the metal case 1
Is in electrical contact with the inner surface of the. The alkaline electrolyte is contained in the metal case 1. A sealing lid 6 that also has an explosion-proof function and a positive electrode terminal is arranged in the upper opening of the metal case 1. The sealing lid 6 has a rectangular sealing plate 8 having a gas vent hole 7 in the center, an elastic valve body 9 made of, for example, synthetic rubber, and a hat-shaped terminal cap having a gas vent hole (not shown). It is composed of 10 and. The elastic valve body 9 is mounted on the sealing plate 8 so as to cover the gas vent hole 7. The terminal cap 10
Is arranged so as to surround the elastic valve body 9 and is fixed to the sealing plate 8 by welding. The insulating gasket 11 in the shape of a bottomed rectangular tube with a rectangular hole at the bottom is
It is arranged between the inner surface of the open end of the metal case 1 and the sealing plate 8, and the sealing lid 6 is airtightly fixed to the metal case 1 by caulking. The positive electrode lead 12 has one end connected to the nickel positive electrode 5 and the other end connected to the lower surface of the sealing plate 8.

For the negative electrode 3, a paste containing a hydrogen storage alloy powder as an active material, a binder, a conductive material powder and water is prepared, and the paste is applied to a conductive substrate and dried,
It is manufactured by roller pressing.

The hydrogen storage alloy is not particularly limited as long as it can store hydrogen electrochemically generated in the electrolytic solution and can easily release the stored hydrogen during discharge. . For example, LaNi ₅ , MmNi
₅ (Mm means a misch metal that is a mixture of lanthanum-based elements such as La, Ce, Pr, Nd, and Sm), LnNi ₅ (Ln; lanthanum-enriched misch metal), and one of these Nis. Parts are Al, Mn, Co,
Examples thereof include multi-element type elements substituted with elements such as Ti, Cu, Zn, Zr, Cr and B, or TiNi type elements and TiFe type elements. Among them, the general formula LnNi _x M
n _y A _z (where A is at least one metal selected from Al and Co, and the atomic ratios x, y, z have a total value of 4.
It is desirable to use a hydrogen storage alloy represented by 8 ≦ x + y + z ≦ 5.4).

Examples of the binder include carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, sodium polyacrylate, polyvinyl alcohol and polytetrafluoroethylene.

Examples of the conductive material powder include carbon black. Examples of the conductive substrate include those having a two-dimensional structure such as punched metal, expanded metal, and wire mesh, and those having a three-dimensional structure such as foam metal and mesh-like sintered metal fiber.

For the positive electrode 5, for example, a conductive material and a binder are added to nickel hydroxide powder which is an active material, and these are kneaded in the presence of water to prepare a paste. It is manufactured by filling it into a glass plate, drying it, and pressing it with a roller.

Examples of the conductive material include cobalt compounds such as cobalt oxide and cobalt hydroxide. Examples of the binder include carboxymethyl cellulose, methyl cellulose, hydroxypropyl methyl cellulose, sodium polyacrylate, polyvinyl alcohol, and polytetrafluoroethylene.

Examples of the conductive substrate include a porous substrate having a three-dimensional structure such as a nickel fiber sintered body, a felt-like nickel porous body and a sponge-like nickel porous body.

Examples of the separator 4 include a nonwoven fabric made of polyolefin fiber such as polyethylene fiber or polypropylene fiber to which a hydrophilic functional group is added, or a nonwoven fabric made of polyamide fiber.

Examples of the electrolyte include potassium hydroxide solution, mixed solution of sodium hydroxide and lithium hydroxide, mixed solution of potassium hydroxide and lithium hydroxide, potassium hydroxide, lithium hydroxide and sodium hydroxide. A mixed solution or the like can be used.

[0026]

According to the method for producing an alkaline secondary battery of the present invention, a separator is provided between a positive electrode and a negative electrode, and one or both of the positive electrode and the negative electrode are formed on a conductive substrate. By first injecting the alkaline electrolyte into the metal case containing the electrode group having a structure filled with the paste containing the active material in two or more times, the electrolyte is first permeated into the separator. When permeated into the separator, the air in the voids inside the positive electrode and the negative electrode when the metal case is left is released to the outside, and the electrolytic solution permeated into the separator therein is the above-mentioned. Since it moves from the separator to the void, the electrolytic solution permeates into the void in the positive electrode and the void in the negative electrode. In this state, when the final injection is performed while applying a centrifugal force that acts in the bottom direction of the metal case, the alkaline electrolyte is absorbed by the separator, so that a predetermined amount of the alkaline electrolyte is accurately added to the electrode group, And it can penetrate quickly. As a result, the cycle life of the secondary battery can be improved. Further, since it is possible to prevent the alkaline electrolyte from overflowing from the metal case, it is possible to prevent the electrolyte solution from adhering to the inner surface of the upper opening of the metal case, The sealing performance can be improved and the reliability of the secondary battery can be improved.

Further, by performing a treatment in which the pressure inside the metal case is reduced and allowed to stand just before the final injection step, the air in the voids in the positive electrode and the voids in the negative electrode is swiftly and surely discharged to the outside. Since it can be released, the alkaline electrolyte can penetrate into more voids in the positive electrode and the negative electrode. As a result, when the final injection is performed after this treatment, the alkaline electrolyte can be quickly absorbed by the separator, and therefore a predetermined amount of the alkaline electrolyte is more accurately applied to the electrode group.
And it can be penetrated in a shorter time.

[0028]

Embodiments of the present invention will now be described in detail with reference to the drawings. Examples 1 to 6 First, a nickel substrate having a three-dimensional net-like structure was pressed at its ends so that a current collector terminal attachment portion was formed. 90 parts by weight of nickel hydroxide powder and 1 cobalt oxide as a conductive agent
0 part by weight was added, and 0.175% by weight of sodium polyacrylate and 30% by weight of water as a binder were added to this mixture and kneaded to prepare a paste. After the paste was filled in the nickel substrate except the collector terminal mounting portion, it was dried, rolled, and a lead tab was welded. A positive electrode was produced by cutting this into a size of 39.2 × 11.1 mm by a punching press.

On the other hand, LmNi _4.0 Co _0.4 Mn _0.3 Al
100 parts by weight of hydrogen storage alloy powder having a composition of _0.3 ,
A paste was prepared by kneading 0.5 parts by weight of a polyacrylate as a binder, 1 part by weight of carbon as an electrically conductive powder and 50 parts by weight of water, and the paste was applied to a punched metal, dried and rolled. Then, 39.2 by punching press
A negative electrode was produced by cutting into a size of 12.1 mm.

Next, the positive electrode is sandwiched between separators made of a polyolefin fibrous nonwoven fabric to which a hydrophilic functional group is added, four sheets of this laminate and five sheets of the above negative electrode are prepared, and these are alternately stacked to form an electrode group. It was made. The electrode group was housed in a bottomed rectangular tubular metal case having a body portion of 13.8 × 6.8 mm.

Next, 1.23 ml of an alkaline electrolytic solution consisting of 7N potassium hydroxide and 1N lithium hydroxide is divided into two at a division ratio as shown in Table 1 below, and the electrolytic solution is injected into the metal case. First, the electrolytic solution for one time was injected into the metal case for 20 seconds while applying a centrifugal force acting toward the bottom of the metal case. The metal case for 3 minutes,
Alternatively, after leaving it for 10 minutes, the remaining electrolytic solution was injected into the metal case for 20 seconds while applying a centrifugal force acting toward the bottom of the metal case. The degree of penetration of the electrolytic solution into the electrode group at this time was observed, and the results are also shown in Table 1 below. Further, the ratio of the voids permeated with the alkaline electrolyte to the voids in the positive electrode and the voids in the negative electrode after the standing step was measured, and the results are also shown in Table 1 below. Comparative Example The total amount of the electrolytic solution (1.23 m) having the same composition as in Examples 1 to 6 was placed in a metal case containing an electrode group similar to Examples 1 to 6.
l) was injected all at once while applying a centrifugal force acting toward the bottom of the metal case. The degree of penetration of the electrolytic solution into the electrode group at this time is also shown in Table 1 below.

[0032]

[Table 1]

As is apparent from Table 1, Examples 1 to 6 in which the electrolytic solution is divided into two or more portions and injected, and the final injection is performed while applying a centrifugal force acting toward the bottom of the metal case, It can be seen that a predetermined amount of the alkaline electrolyte has penetrated into the electrode group without overflowing the electrolytic solution from the metal case.
On the other hand, in the comparative example in which the total amount of the electrolytic solution is injected into the metal case while applying the centrifugal force that acts toward the bottom of the metal case at a time, it can be seen that the alkaline electrolytic solution overflows from the metal case. Example 7 An electrode group including a positive electrode, a negative electrode, and a separator similar to those in Examples 1 to 6 was housed in a metal case similar to Examples 1 to 6.
Alkaline electrolyte having the same composition as in Examples 1 to 6 1.23 m
40% by volume of 1 was injected into the metal case for 20 seconds while applying a centrifugal force acting toward the bottom of the metal case.
After leaving the metal case for 3 minutes, the pressure inside the metal case was reduced to 500 mmHg and left. After the alkaline electrolyte was infiltrated into 95% by volume of the voids in the positive electrode and the voids in the negative electrode, the pressure inside the metal case was returned to normal pressure.
Subsequently, the remaining electrolytic solution was injected into the metal case for 20 seconds while applying a centrifugal force acting toward the bottom of the metal case. When the degree of permeation of the electrolytic solution into the electrode group at this time was observed, the total amount of electrolytic solution was permeated into the electrode group.

The prismatic nickel-hydrogen secondary battery shown in FIG. 1 was assembled from the metal cases of Examples 1 to 7 in which a predetermined amount of the alkaline electrolyte had been injected as described above, in the following procedure. First, after the tip of the positive electrode lead 12 protruding from the positive electrode 5 in each metal case 1 is connected to the lower surface of the sealing lid 6, the sealing lid 6 is placed in the upper opening of the metal case 1. . Subsequently, the upper end of the metal case 1 was curled inward by caulking and fixing, and the sealing lid 6 was attached to the upper opening of the metal case 1 with good airtightness to manufacture the secondary battery.

Further, 1.23 ml of the electrolytic solution having the same composition as in Examples 1 to 7 was injected into the metal case accommodating the electrode groups similar to those in Examples 1 to 7 by the fixed amount discharge pump in 8 divided portions. However, it took 20 minutes to complete the injection of the electrolytic solution. In addition, although the example applied to the nickel-hydrogen secondary battery was described in the above-mentioned embodiment, the present invention can be similarly applied to the nickel-cadmium secondary battery.

[0036]

As described above in detail, according to the method for manufacturing an alkaline secondary battery of the present invention, the alkaline electrolytic solution can be injected into the alkaline secondary battery containing no electrolytic solution accurately and in a short time. Therefore, the cycle life of the secondary battery can be improved, the airtightness of the secondary battery can be improved, and the reliability of the secondary battery can be improved.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a prismatic nickel-hydrogen secondary battery that is an example of an alkaline secondary battery manufactured by a method according to the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Metal case, 2 ... Electrode group, 3 ... Negative electrode, 4 ... Separator, 5 ... Positive electrode, 6 ... Sealing lid.

Claims (2)

[Claims] 1. An electrode group housed in a metal case, the electrode group being manufactured by interposing a separator between a positive electrode and a negative electrode, and an alkaline electrolyte housed in the metal case. In the method for manufacturing an alkaline secondary battery having a structure in which one or both of the negative electrodes are filled with a paste containing an active material, the alkaline electrolyte is divided into two or more times in the metal case in which the electrode group is housed. And a final injection is performed while applying a centrifugal force that acts toward the bottom of the metal case. 2. The method of manufacturing an alkaline secondary battery according to claim 1, wherein a process of reducing the pressure inside the metal case and leaving the metal case left is performed immediately before the final injection step.