JP2000149955A - Alkaline dry battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve productivity, to reduce the degradation of discharge duration due to storage and to reduce the degradation of battery capacity by using at least one kind of poly-N-vinylacetoamide and polyethyleneimine as a binder of a positive electrode. SOLUTION: At least, one kind of poly-N-vinylacetoamide and polyethyleneimine is used as a binder of a positive electrode for binding a positive electrode active material and the like. Because the binding property of the binder to manganese dioxide or the like for the positive electrode active material and the like can thereby be improved, the strength of the positive electrode can be enhanced without increasing the content of the binder in a positive electrode material. That is, because the poly-N-vinylacetoamide or polyethyleneimine has a high binding action, the strength of the positive electrode can be enhanced without increasing the content of the binder in the positive electrode material. Therefore, the crack and breakage of the positive electrode can be reduced in manufacturing processes.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alkaline dry battery, and more particularly, to enhancing the binding action of a binder for a positive electrode to improve productivity and suppressing a decrease in discharge duration time due to storage. The present invention relates to an alkaline dry battery in which a decrease in discharge duration due to the battery is small and a decrease in battery capacity is small.

[0002]

2. Description of the Related Art Generally, a cathode material of an alkaline dry battery mainly comprises manganese dioxide as a cathode active material and graphite as a conductive additive, and contains a binder for imparting a binding property. , Water or electrolyte. The reason that the binder is contained in the positive electrode material is that the binder binds the positive electrode materials together, and the positive electrode of the alkaline dry battery absorbs the electrolytic solution after molding or generates a small amount of gas, so that the binding force between the positive electrode materials is reduced. The reason for this is that the conductivity is reduced due to loosening and the discharge duration is reduced, so that the reduction in the discharge duration is suppressed, and the productivity is improved by reducing cracking and chipping of the positive electrode during the manufacturing process. It is.

[0003] When the content of the binder in the positive electrode material is increased, the strength of the positive electrode can be increased, the productivity can be improved, and the reduction in the discharge duration time due to storage can be suppressed. On the other hand, there is a problem that the filling amount of the positive electrode active material decreases and the battery capacity decreases.

As the binder, an organic material having alkali resistance, for example, polyethylene, polytetrafluoroethylene (PTFE), sodium polyacrylate (S
Various organic substances such as PA), polyvinyl alcohol (PVA), and styrene butadiene rubber (SBR) have been used, but there is no definitive substance, and only by selecting a binder, the discharge duration decreases due to storage and the battery capacity decreases. The decline could not be resolved at once.

[0005]

As described above, when the content of the binder in the positive electrode material is increased, the strength of the positive electrode is increased, the productivity can be improved, and the discharge duration time during storage can be reduced. Although the decrease can be suppressed, when the content of the binder in the positive electrode material is increased, the filling amount of the positive electrode active material is reduced, and the battery capacity is reduced.

Accordingly, the present invention solves the above-mentioned problems in the prior art, enhances the binding action of the binder, and increases the strength of the positive electrode without increasing the content of the binder in the positive electrode material. It is another object of the present invention to provide an alkaline dry battery that improves productivity and suppresses a decrease in the discharge duration due to storage, reduces the decrease in the discharge duration due to storage, and reduces the battery capacity.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, as a binder for a positive electrode for binding a positive electrode active material and the like, poly-N
-When at least one of vinylacetamide or polyethyleneimine is used, it is possible to improve the binding property between the binder and the positive electrode active material such as manganese dioxide, without increasing the content of the binder in the positive electrode material, The inventors have found that the strength of the positive electrode can be increased and the above-mentioned problems can be solved, and have completed the present invention.

That is, the above-mentioned poly-N-vinylacetamide and polyethyleneimine have a larger binding effect than the conventionally used polyethylene and the like, so that the content of the binder in the cathode material can be increased without increasing the content of the binder. As a result, cracking and chipping of the positive electrode during the manufacturing process are reduced and productivity is improved, and when the battery is stored, swelling of the positive electrode due to the electrolytic solution is reduced. A decrease in conductivity is suppressed, and a decrease in discharge duration time due to storage is suppressed.
In addition, since it is not necessary to increase the content of the binder, the positive electrode active material can be sufficiently filled, and a decrease in battery capacity can be prevented.

[0009]

DETAILED DESCRIPTION OF THE INVENTION In the present invention, poly-N-vinylacetamide and polyethyleneimine may be used alone or in combination. The amount of the binder composed of at least one of poly-N-vinylacetamide and polyethyleneimine may be the same as the conventional one. For example, the binder may be contained in the positive electrode material at about 0.3 to 1.5% by weight. In particular, 0.
A good binding action can be exhibited even with a relatively small content of about 3 to 0.7% by weight.

In the present invention, for example, manganese dioxide or the like is used as the positive electrode active material, and graphite, acetylene black, ketchen black or the like is used as the conductive additive.

The production of the positive electrode is generally performed through the following steps. That is, FIG.
As shown in (1), first, an active material (a positive electrode active material), a conductive auxiliary, a binder, and water or an electrolytic solution are mixed. Then, in order to improve the productivity in the next molding step, 10 to 10 are mixed.
Granulate to about 0 mesh. However, this granulation step is not an essential step and can be omitted. Next, the positive electrode material is formed into a cylindrical shape, and the formed body is inserted into a positive electrode can. Then, when the molded body is inserted into the positive electrode can, or after the molded body is inserted into the positive electrode can, a pressing step is performed to increase the adhesion between the molded body of the positive electrode material and the positive electrode can by applying pressure, and the positive electrode is formed. Is done.

[0012]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 89 parts by weight of electrolytic manganese dioxide, 5 parts by weight of graphite and a concentration of 3
1 part by weight of an aqueous solution of poly-N-vinylacetamide (solid content concentration: 50% by weight) was added to 99 parts by weight of a main positive electrode material containing an electrolyte composed of an aqueous solution of 5% by weight of potassium hydroxide, followed by stirring and mixing. After the obtained mixture was pressed and pulverized, the mixture was granulated to a size of 50 mesh pass, and the obtained granulated powder was heated at 140 ° C. for 5 minutes. Next, after being formed into a cylindrical shape by a press machine, four of the formed bodies were inserted into a positive electrode can so as to be stacked, and the above-mentioned formed body was pressed on the positive electrode can by further pressurization to form a positive electrode. Using this positive electrode, a known separator, an electrolytic solution, a zinc paste and the like, an AA alkaline battery having the structure shown in FIG. 2 was produced.

Now, the alkaline dry battery shown in FIG. 2 will be described. The positive electrode 1 is formed by using poly-N-vinylacetamide as a binder as described above, and after granulating, heating the positive electrode material into a cylindrical shape. Four cylindrical forming bodies are stacked, inserted into the positive electrode can 2 with terminals, and pressurized from above to press-bond the molded body of the positive electrode material to the inner surface of the positive electrode can 2.

A separator 3 is disposed between the positive electrode 1 and the negative electrode 4 made of a zinc paste. The zinc paste is made of a zinc powder and a potassium hydroxide aqueous solution to which a gelling agent is added to form a gelled alkaline electrolyte. The tip end side of the negative electrode current collector 5 is inserted into the negative electrode 4 made of this zinc paste, and the opening of the positive electrode can 2 has the head of the negative electrode current collector 5, a sealing body 6, a metal washer 7, The positive electrode can 2 is sealed with a resin washer 8, an insulating cap 9, a negative electrode terminal plate 10, and the like.

The battery manufactured as described above was subjected to the measurement of the discharge duration described later, and a part of the battery was heated at 80 ° C.
For 5 days and 8 days, and used for measurement of the discharge duration described later.

Example 2 As in Example 1, 1 part by weight of an aqueous solution of polyethyleneimine (solid content: 50% by weight) was added as a binder to 99 parts by weight of a main positive electrode material containing electrolytic manganese dioxide, graphite and an electrolytic solution. And mixed. After granulating the obtained mixture to a size of a 50 mesh pass, the mixture is formed into a cylindrical shape by a press machine, and the obtained cylindrical forming bodies are stacked in a stack of four pieces, inserted into a positive electrode can, and pressed to form the positive electrode. AA alkaline battery was prepared in the same manner as in Example 1 except that the molded body of the material was pressed into a positive electrode can to form a positive electrode, and the positive electrode was used. The prepared battery was subjected to the measurement of the discharge duration described below, and a part of the battery was stored at 80 ° C. for 5 days and 8 days.
It was used for measurement of the discharge duration described later.

Comparative Example 1 An AA alkaline battery was prepared in the same manner as in Example 1 except that polyethylene powder was used as a binder according to the prior art. The prepared battery was subjected to the following discharge duration, and a part of the battery was stored at 80 ° C. for 5 days and 8 days, and was subjected to the following discharge duration measurement.

The batteries of Examples 1 and 2 and the battery of Comparative Example 1 were discharged at 20 ° C. and a resistance of 2Ω, and the duration of discharge until the terminal voltage of the battery dropped to 0.9 V was measured. Table 1 shows the results. The measurement of the discharge duration was performed in Examples 1 to 3.
2 and the battery of Comparative Example 1, the battery immediately after production and the battery after storage at 80 ° C. for 5 days (Table 1 shows “80 ° C.
This was performed for the battery after storage for 5 days) and the battery after storage at 80 ° C for 8 days (displayed as “after storage for 8 days at 80 ° C” in Table 1). As described above, the degree of swelling of the positive electrode when stored at 80 ° C for 5 days is the same level as when stored at 20 ° C for 3 years, and the degree of swelling of the positive electrode when stored at 80 ° C for 8 days is 20 ° C. It is said to be at the same level as when stored for 5 years.

[0020]

[Table 1]

As shown in Table 1, the batteries of Example 1 using poly-N-vinylacetamide as a binder and the batteries of Example 2 using polyethyleneimine were comparative examples using polyethylene as a binder according to the prior art. 1
The discharge duration after storage was longer and the decrease in discharge duration due to storage was smaller than that of the battery of Example 1. Further, the batteries of Examples 1 and 2 had a discharge duration immediately after manufacture equal to or longer than that of the battery of Comparative Example 1, and the battery capacity was reduced by using poly-N-vinylacetamide or polyethyleneimine as a binder. No decrease was observed. In particular, the battery of Example 1 using poly-N-vinylacetamide as a binder had a long discharge duration immediately after production and a long discharge duration after storage.

As described above, the fact that the battery of the present invention has a small decrease in the discharge duration time due to storage means that the binding action of the binder is large, and therefore the strength of the positive electrode is high and the positive electrode is cracked during the manufacturing process. Although the defect rate was small and the productivity was high, the defect rate at the time of manufacturing the positive electrode was actually examined. In the case of Comparative Example 1, the defect rate was 1000 ppm, whereas in Example 1, the defect rate was 1000 ppm. Is 80ppm
In the case of Example 2, the defective rate was 100 ppm, and the productivity was excellent.

In the above embodiment, poly-
Although the case where N-vinylacetamide or polyethyleneimine is used alone is exemplified, poly-N-vinylacetamide and polyethyleneimine may be used in combination. Further, the poly-N-vinylacetamide and polyethyleneimine may be used in combination with a conventionally used binder such as polytetrafluoroethylene, sodium polyacrylate, polyvinyl alcohol, and styrene-butadiene rubber as long as the effects are not impaired. it can.

[0024]

As described above, according to the present invention, the binding effect of the binder is enhanced, the strength of the positive electrode is increased without increasing the content of the binder in the positive electrode material, and the productivity is improved. In addition, it was possible to provide an alkaline dry battery in which a decrease in discharge duration due to storage was suppressed, and a decrease in discharge duration due to storage was small, and a decrease in battery capacity was small.

[Brief description of the drawings]

FIG. 1 is a manufacturing process diagram of a positive electrode of an alkaline dry battery.

FIG. 2 is a partial cross-sectional view showing an example of the alkaline dry battery of the present invention.

[Explanation of symbols]

 1 positive electrode 3 separator 4 negative electrode

Claims (1)

[Claims] 1. An alkaline dry battery using at least one of poly-N-vinylacetamide and polyethyleneimine as a binder for a positive electrode.