JP2002015748A - Manufacturing method of cylindrical alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the yield of a cylindrical alkaline battery by maintaining the discharge performance without adding a special binder and by improving the strength of the positive electrode pellet. SOLUTION: In the manufacturing method in which after a plastic positive mixture and a separator are inserted in the battery case, an electrolyte is filled and made to be absorbed, and then the gel form negative electrode is filled, the concentration of the alkaline electrolyte for the positive mixture is made higher concentration than the alkaline electrolyte for the filling use. Preferably, the concentration of the electrolyte for the positive mixture is made 45-50 wt.% and the concentration of the electrolyte for the filling use is made 35-40 wt.% and the former is made higher concentration than the latter by 5 wt.% or more.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a method for manufacturing a cylindrical alkaline battery having a structure in which a positive electrode material mixture, a separator and a gelled negative electrode are sequentially inserted into a battery case.

[0002]

2. Description of the Related Art In recent years, the performance and miniaturization of electronic devices such as video cameras and small liquid crystal televisions have been remarkable, and the demand for higher capacity of batteries serving as power supplies for these electronic devices has been increasing. As a battery for such an application, an alkaline dry battery using an alkaline electrolyte such as potassium hydroxide has been increasingly used in place of a manganese dry battery as a battery capable of obtaining a larger capacity. A typical method of manufacturing an alkaline dry battery is a step of forming a positive electrode mixture powder containing manganese dioxide, graphite and an alkaline electrolyte into a cylindrical shape, inserting the obtained positive electrode mixture molded body into a metal battery case, Re-pressurizing the positive electrode mixture molded body to adhere to the battery case, arranging a cylindrical separator inside the positive electrode mixture molded body, injecting an alkaline electrolyte into the cylindrical separator, And a step of filling the cylindrical negative electrode with a gelled negative electrode.

The electrolyte used here is a 35 to 45 wt% aqueous solution of potassium hydroxide, which is mixed with the positive electrode mixture, injected into the cylindrical separator, and included in the gelled negative electrode. In general, the same thing was shared. The amount of the electrolytic solution added to the positive electrode mixture is 1 to 5 wt%, and the binding property of the mixture powder is improved to improve the moldability, and the strength of the positive electrode mixture molded product (hereinafter referred to as positive electrode pellet) is improved. Is the main purpose. Since the positive electrode pellet is formed into a hollow cylindrical shape, cracks and chips are likely to occur in the process of assembling the battery on the production line, especially in the transporting process of the positive electrode pellet, resulting in poor product yield and poor quality. Also causes various variations in characteristic values.

Therefore, it has been proposed to add a fine powder of polyethylene, polytetrafluoroethylene, sodium polyacrylate or the like as a binder in order to improve the binding property of the positive electrode mixture powder and improve the moldability. . However, the addition of such a binder has a problem that the discharge performance is deteriorated by decreasing the filling amount of the active material or increasing the electric resistance.

[0005]

SUMMARY OF THE INVENTION In view of the above, it is an object of the present invention to maintain the discharge performance without adding a special binder, and to improve the yield by improving the strength of the positive electrode pellet. I do. Another object of the present invention is to provide a method of manufacturing a cylindrical alkaline battery capable of shortening a time required for absorbing an electrolytic solution injected into a separator in a battery case.

[0006]

The method of manufacturing a cylindrical battery according to the present invention comprises the steps of: forming a positive electrode mixture powder containing manganese dioxide, graphite and an alkaline electrolyte into a hollow cylindrical shape;
Insert the obtained positive electrode mixture molded body into a metal battery case,
Re-pressurizing the positive electrode mixture molded body to adhere to the battery case, arranging a cylindrical separator inside the positive electrode mixture molded body, injecting an alkaline electrolyte into the cylindrical separator, And a step of filling the gelled negative electrode into the cylindrical separator, and injecting the concentration of the alkaline electrolyte contained in the positive electrode mixture into the separator. The concentration of the alkaline electrolyte is higher than that of the alkaline electrolyte.

The alkaline electrolyte used here is an aqueous solution of potassium hydroxide. The electrolyte contained in the positive electrode mixture has a potassium hydroxide concentration of 40 to 50% by weight. Potassium concentration 35
４５45 wt%, and the concentration of the former is 5 watts higher than that of the latter.
It is preferable that the concentration is at least t% or higher. When the potassium hydroxide concentration of the electrolyte solution contained in the positive electrode mixture is less than 40% by weight, the heavy load discharge performance and the strength of the positive electrode pellet decrease. Also, preparing an electrolytic solution having a concentration exceeding 50 wt% is disadvantageous in mass production. On the other hand, if the concentration of potassium hydroxide in the electrolyte injected into the separator is less than 35% by weight, the heavy-load discharge performance decreases. In addition, 45wt%
If it exceeds, it takes time for absorption into the separator, and the productivity is reduced. More preferably, the concentration of potassium hydroxide in the electrolyte solution contained in the positive electrode mixture is 45 to 50 wt%.

[0008]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention has been made by paying attention to the fact that the strength of a positive electrode pellet is improved by increasing the concentration of potassium hydroxide in an electrolytic solution added to a positive electrode mixture powder. Although the details of the reason for this effect are not clear, it is thought that the higher the concentration of the alkaline electrolyte, the higher the viscosity of the electrolyte, and the more the interfacial tension acts to increase the binding property of the positive electrode mixture powder. It is. On the other hand, a high-concentration alkaline electrolyte having the effect of improving the strength of the positive electrode pellet as described above has a low absorption rate to the separator, and the productivity is reduced.

Therefore, in the present invention, a high concentration electrolyte is used for the positive electrode mixture, and a lower concentration electrolyte is used for the injection solution. As a result, it is possible to simultaneously increase the strength of the positive electrode pellet and shorten the liquid absorption time to the separator. Also, an electrolyte for a positive electrode mixture,
Even if the concentration of the electrolyte for injection is made different, the discharge performance can be maintained by appropriately adjusting the concentrations of both electrolytes. Since the present invention does not add a special binder to the positive electrode mixture as described above, the conventional discharge performance can be maintained. In addition, since the molding pressure is not particularly increased in order to improve the strength of the positive electrode pellet, there is no problem that inconveniences such as abrasion of the molding die and breakage of the molding pin increase.

An embodiment of the present invention will be described below. Figure 1
FIG. 5 is a front view of a cross section of a main part of the alkaline dry battery LR6 according to the present embodiment. Reference numeral 1 denotes a battery case made of steel. A positive electrode mixture 2 is accommodated in the battery case 1. This positive electrode mixture was produced as follows. First, manganese dioxide, graphite, and an alkaline electrolyte were mixed in a weight ratio of 95: 5:
After mixing at a ratio of 2 and sufficiently stirring, the mixture was compression-molded into flakes. The flake-shaped positive electrode mixture was pulverized into granules, which were classified by a sieve, and 14-80 mesh powder was pressed into a hollow cylindrical shape to obtain positive electrode pellets. Four of these positive electrode pellets were inserted into the battery case 1, and the positive electrode pellets were re-formed by a pressing jig and brought into close contact with the inner wall of the battery case 1.

A bottomed cylindrical separator 4 was placed at the center of the positive electrode mixture 2 placed in the battery case as described above, and a predetermined amount of an alkaline electrolyte was injected into the separator. After a lapse of a predetermined time, the separator 4 was filled with the gelled negative electrode 3 composed of an alkaline electrolyte, a gelling agent, and a zinc alloy powder.

Next, after a step is formed in the vicinity of the opening of the battery case 1 by a conventional method, a resin sealing body 5 in which the negative electrode current collector 6, the washer 7 and the negative electrode terminal plate 8 are combined is attached to the opening of the battery case. And the opening end of the battery case 1 was bent inward to complete the sealing step. Thereafter, an outer label made of a heat-shrinkable resin tube was attached.

In the above alkaline dry battery manufacturing process, as shown in Table 1, various concentrations of potassium hydroxide electrolytes for the positive electrode mixture, the liquid injection, and the gelled negative electrode were manufactured. The strength of the positive electrode pellets of those batteries,
Table 1 shows the comparison between the absorption time of the injected electrolyte and the discharge capacity. The strength of the positive electrode pellet was represented by a pressing force when a cylindrical pellet was placed sideways on a table, a jig with a gauge was pressed against the body of the pellet from above, and the pellet was broken. The discharge capacity was represented by an index using the value of Comparative Example 1 as a reference value of 100 as the discharge time up to a final voltage of 0.9 V when the battery was continuously discharged at a current of 500 mA at 20 ° C. Comparative Example 1 is based on a conventional typical formulation.

[0014]

[Table 1]

FIG. 2 is a graph showing the relationship between the concentration of the electrolyte contained in the positive electrode mixture and the strength of the positive electrode pellet.
FIG. 3 is a graph showing the relationship between the concentration of the electrolyte for injection and the liquid absorption time. From FIG. 2, it can be seen that the strength of the conventional positive electrode pellet can be maintained when the concentration of potassium hydroxide in the electrolytic solution is 40 wt% or more.
It is understood that the content is preferably set to 5 wt% or more and 50 wt%. On the other hand, the absorption time of the injected electrolyte solution is not so long as compared with the conventional one if the potassium hydroxide concentration of the electrolyte solution is up to about 45 wt%.
t% or less is preferred. In addition, taking into account the discharge performance, the concentration of the electrolyte for the positive electrode mixture is increased to increase the strength of the positive electrode pellet, and the liquid absorption time is not extended,
In order to maintain the discharge performance, the concentration of the electrolyte for the positive electrode mixture should be 45
It is most preferable that the concentration of the electrolyte for injection is 35 to 40 wt%, and the concentration of the former is 5 wt% or more higher than that of the latter.

[0016]

As described above, according to the present invention, it is possible to improve the yield of a cylindrical alkaline battery by maintaining the conventional discharge performance and improving the strength of the positive electrode pellet.

[Brief description of the drawings]

FIG. 1 is a front view of an alkaline dry battery according to one embodiment of the present invention, in which main parts are cut away.

FIG. 2 is a graph showing the relationship between the concentration of an electrolyte for a positive electrode mixture and the strength of a positive electrode pellet.

FIG. 3 is a graph showing a relationship between a concentration of an electrolyte for injection and a liquid absorption time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Battery case 2 Positive electrode mixture 3 Gelled negative electrode 4 Separator 5 Sealing body 6 Negative current collector 7 Washer 8 Negative terminal plate 9 Exterior label

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yuji Motoya 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. F term (reference) 5H024 AA02 AA14 BB05 BB07 BB08 CC02 CC14 DD09 DD14 FF09 HH08 5H050 AA14 AA19 BA04 CA02 CB13 DA02 DA09 EA12 FA08 GA03 GA10 GA23 HA10

Claims (3)

[Claims] 1. A step of forming a positive electrode mixture powder containing manganese dioxide, graphite and an alkaline electrolyte into a hollow cylindrical shape, inserting the obtained positive electrode mixture molded body into a metal battery case, and pressurizing again. A step of bringing the positive electrode mixture molded body into close contact with the battery case, a step of arranging a cylindrical separator inside the positive electrode mixture molded body, injecting an alkaline electrolyte into the cylindrical separator, and dissolving the electrolytic solution in the positive electrode mixture. An alkaline electrolyte solution comprising a step of absorbing the molded body and the separator, and a step of filling the cylindrical separator with a gelled negative electrode, and injecting the concentration of the alkaline electrolyte contained in the positive electrode mixture into the interior of the separator A method for producing a cylindrical alkaline battery, wherein the concentration is higher than that of the above. 2. The method according to claim 1, wherein the alkaline electrolyte is an aqueous solution of potassium hydroxide, the concentration of potassium hydroxide in the electrolyte contained in the positive electrode mixture is 40 to 50 wt%, and the concentration of hydroxide in the electrolyte to be injected into the separator is increased. Potassium concentration 35-45
The method for producing a cylindrical alkaline battery according to claim 1, wherein the concentration is 5 wt% or more, and the concentration of the former is 5 wt% or more higher than that of the latter. 3. The method for producing a cylindrical alkaline battery according to claim 2, wherein the concentration of potassium hydroxide in the electrolyte solution contained in the positive electrode mixture is 45 to 50 wt%.