JP2000048827A - Alkaline battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve a strong load discharge characteristic after being preserved at a high temperature by providing a metallic positive electrode case forming a conductive coating film on the inside surface, a positive electrode mix making contact with the conductive coating film in it and a negative electrode arranged so as to face opposite to the positive electrode mix, including nickel oxyhydroxide as an active material in the positive electrode mix. SOLUTION: A positive electrode mix contains manganese dioxide and nickel oxyhydroxide, and the compounding ratio is set to 20 to 90 wt.% in the manganese dioxide and 80 to 10 wt.% in the nickel oxyhydroxide. The positive electrode mix preferably contains graphite of 3 to 8 pts.wt. with respect to 100 pts.wt. of an active material. A battery forming a conductive coating film in a positive electrode case and using the positive electrode mix by mixing the nickel oxyhydroxide with the manganese dioxide, is improved in 1,000 mA continuous discharge performance of an initial degree more than a battery of not mixing the nickel oxyhydroxide. However, a battery having no conductive coating film formed inside the positive electrode case even if the nickel oxyhydroxide is mixed, drastically is degraded in performance after being preserved at 60 deg.C for a month.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in an alkaline battery in which a positive electrode mixture mainly composed of manganese dioxide and a carbon agent is housed in a metal positive electrode case in close contact.

[0002]

2. Description of the Related Art In an alkaline manganese battery, a cylindrical positive electrode mixture is disposed in close contact with a positive electrode case in a positive electrode case also serving as a positive electrode terminal, and a gel negative electrode is disposed at the center of the mixture through a separator. Having a structure. In recent years, equipment using these batteries has a large load, and batteries used are required to have excellent performance in heavy load discharge. Therefore,
It has been studied to produce a battery excellent in heavy load discharge performance by mixing nickel oxyhydroxide in the positive electrode mixture.

[0003]

However, nickel oxyhydroxide has lower storage stability than manganese dioxide. In particular, when stored at a high temperature, nickel oxyhydroxide has a large self-discharge, so that a battery containing nickel oxyhydroxide after storage has a lower heavy load discharge performance than a conventional battery. If the positive electrode case and the positive electrode mixture are in direct contact, a thin oxide film is formed on the surface of the positive electrode case by the oxidizing action of manganese dioxide, nickel oxyhydroxide, etc. during storage of the battery. The electrical contact state with the mixture deteriorates, and the storage performance of the battery decreases. In particular, nickel oxyhydroxide has a higher potential and a greater reducing effect than manganese dioxide, and therefore has a higher oxidation rate on the surface of the positive electrode case than a battery containing no nickel oxyhydroxide.

As described above, a battery to which nickel oxyhydroxide is added does not contain nickel oxyhydroxide due to a decrease in the amount of a dischargeable positive electrode active material and an increase in resistance between a positive electrode case and a positive electrode mixture. There was a problem that the heavy load discharge characteristics after storage at high temperature were inferior to batteries. The present invention
In view of the above problems, an object of the present invention is to provide an alkaline battery having improved high-load discharge characteristics after high-temperature storage.

[0005]

According to the present invention, there is provided an alkaline battery comprising: a metal positive electrode case having a conductive film formed on an inner surface thereof;
A positive electrode mixture accommodated in the positive electrode case and in contact with the conductive film, and a negative electrode disposed to face the positive electrode mixture with a separator interposed therebetween, wherein the positive electrode mixture has at least oxy as an active material. It is characterized by containing nickel hydroxide. Here, the positive electrode mixture contains manganese dioxide and nickel oxyhydroxide, and the compounding ratio is 20 to 90 wt% of manganese dioxide, nickel oxyhydroxide 8
It is preferably 0 to 10 wt%. Further, it is preferable that the positive electrode mixture contains 3 to 8 parts by weight of graphite based on 100 parts by weight of the active material.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, nickel oxyhydroxide is added to a positive electrode mixture to form a conductive coating inside a positive electrode case in order to improve the heavy load discharge characteristics of a battery. To compensate for the self-discharge of nickel oxyhydroxide and maintain the high-load discharge performance of the battery after storage at high temperatures,
It is conceivable to increase the proportion of nickel oxyhydroxide in the positive electrode mixture. However, nickel oxyhydroxide is more expensive than manganese dioxide.
Battery unit price increases. Therefore, it is necessary to suppress the reduction of nickel oxyhydroxide in order to suppress the nickel oxyhydroxide to an appropriate ratio, suppress the self-discharge, and maintain the heavy load discharge characteristics.

According to the present invention, a conductive coating is formed inside the positive electrode case in order to suppress the reduction of nickel oxyhydroxide. In addition, when a conductive film is formed on the inside of the positive electrode case, it is possible to suppress the formation of an oxide film on the inner wall surface of the positive electrode case by nickel oxyhydroxide or manganese dioxide having oxidizing power. The effect of suppressing an increase in resistance between the positive electrode mixtures can also be expected. Therefore, by adopting the above configuration, the storage characteristics of the battery can be improved, and the heavy load discharge performance after high-temperature storage can be improved.

The conductive film formed on the positive electrode case preferably has no oxide film formed by nickel oxyhydroxide and manganese dioxide at the interface between the positive electrode mixture and the conductive film, and is preferably made of expanded graphite, artificial graphite and flake reinforced. Examples include conductive carbon such as graphite. The mixing ratio of manganese dioxide and nickel oxyhydroxide in the positive electrode mixture is preferably 20 to 90% by weight of manganese dioxide and 80 to 10% by weight of nickel oxyhydroxide because of excellent initial and high-temperature storage discharge characteristics. It is. In particular, manganese dioxide is 50 to 90 wt% and nickel oxyhydroxide is 50 to 1%.
It is effective to restrict the amount to 0 wt%.

The carbon material to be added to the positive electrode mixture is suitably graphite or the like, and its content is preferably 3 to 8 parts by weight based on 100 parts by weight of the positive electrode active material. If the amount of graphite is less than 3 parts by weight, the conductivity of the positive electrode mixture is reduced, and the discharge time is shortened. Further, the strength of the positive electrode mixture also decreases. If the amount of graphite is more than 8 parts by weight,
Since the amount of the active material is relatively reduced, the discharge time is shortened.

[0010]

FIG. 1 is a front view of a part of an alkaline battery in a cross section according to an embodiment of the present invention. This battery is manufactured as follows. Reference numeral 1 denotes a positive electrode case made of nickel-plated steel. As shown in FIG. 2, a conductive coating 2 is formed on the inner surface of the positive electrode case 1. Inside the positive electrode case 1, a plurality of short-cylindrical positive electrode mixture moldings mainly composed of manganese dioxide and graphite are inserted, and the inner surface of the case 1 is brought into close contact with the inner surface of the case 1 by repressurizing the inside of the case. You. After inserting the separator 4 and the insulating cap 5 inside the positive electrode mixture 3 filled in the case in this way, the gelled zinc negative electrode 6 is injected inside the separator. The gelled negative electrode 6 is made of sodium polyacrylate as a gelling agent, an alkaline electrolyte, and zinc powder as a negative electrode active material. Next, the negative electrode current collector 10 integrated with the resin sealing plate 7, the bottom plate 8 also serving as the negative electrode terminal, and the insulating washer 9 is inserted into the gelled negative electrode 6, and the opening end of the positive electrode case 1 is closed with the sealing plate 7. The opening of the positive electrode case 1 is brought into close contact with the peripheral portion of the bottom plate 8 by crimping through the end portion. Next, the outer label 11 is coated on the outer surface of the positive electrode case 1. Thus, an alkaline battery is completed.

Example 1 Manganese dioxide, nickel oxyhydroxide and expanded graphite powder were blended at the weight ratio shown in Table 1, and 100 parts by weight of the active material was added to the electrolyte 1
After mixing the parts by weight, the mixture was granulated and pressed to prepare a positive electrode mixture. As the electrolyte, a 41 wt% aqueous solution of potassium hydroxide was used.

[0012]

[Table 1]

A coating for a conductive film containing conductive carbon as a main material was applied to the inside of the positive electrode case 1 and then dried to form a conductive film 2. The thickness of the conductive film was 5 μm. Then, using the positive electrode mixture and the positive electrode case prepared as described above, AA size alkaline batteries Nos. 1 to 7 shown in FIG. 1 were prepared. Example 1 As a comparative example, Example 1 was repeated except that the conductive film 2 was not formed inside the positive electrode case 1.
As in the case of the alkaline battery No. Nos. 8 to 13 were produced.

Each of the above batteries was initially discharged and stored at 60 ° C. for one month, then continuously discharged at room temperature at a constant current of 1000 mA, and the duration until the voltage reached a final voltage of 0.9 V was measured. . Table 1 shows the average value of 10 batteries. In addition, the battery No. which did not contain nickel oxyhydroxide and did not form a conductive coating inside the positive electrode case. The initial duration of 8 is shown as 100.

As is clear from Table 1, batteries using a positive electrode mixture in which a conductive film was formed on the positive electrode case and nickel oxyhydroxide was mixed with manganese dioxide (Nos. 2 to 7)
In the case of No. 1, the initial 1000 mA continuous discharge performance was improved compared to the battery (No. 1) in which nickel oxyhydroxide was not mixed.
However, even when nickel oxyhydroxide was mixed, a battery (No. 9 to No. 9) in which a conductive film was not formed inside the positive electrode case.
No. 13) shows a remarkable deterioration in performance after storage at 60 ° C. for one month, and a battery (N
o. 8), the discharge performance was reduced. The battery in which the conductive coating was formed on the positive electrode case was able to suppress the self-discharge of nickel oxyhydroxide, and had good high-load discharge performance after high-temperature storage. In particular, when the ratio of nickel oxyhydroxide in the positive electrode active material was 20 to 80 wt%, a battery having excellent discharge characteristics was obtained.

Example 2 Manganese dioxide 50 wt%,
A positive electrode mixture was prepared in the same manner as in Example 1 except that graphite was mixed at a weight ratio shown in Table 2 with respect to 100 parts by weight of the active material containing 50 wt% of nickel oxyhydroxide. Then, in the same manner as in Example 1, the alkaline battery No. Nos. 14 to 17 were produced. Table 2 shows the durations of these batteries measured under the same conditions as described above.

[0017]

[Table 2]

From Table 2, it was found that the battery obtained by adding 3 to 8 parts by weight of graphite to 100 parts by weight of the positive electrode active material had excellent discharge characteristics, and exhibited excellent discharge characteristics even after storage at high temperatures.

[0019]

As described above, according to the present invention, it is possible to provide an alkaline battery having excellent heavy load discharge characteristics even after storage at a high temperature.

[Brief description of the drawings]

FIG. 1 is a front view showing a cross section of a part of an alkaline battery according to an embodiment of the present invention.

FIG. 2 is an enlarged view of a main part of the battery.

[Description of Signs] 1 Positive electrode case 2 Conductive coating 3 Positive electrode mixture 4 Separator 5 Insulating cap 6 Gelled negative electrode 7 Resin sealing body 8 Bottom plate 9 Insulating washer 10 Negative current collector 11 Outer label

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Shigeto Noya 1006 Kadoma Kadoma, Osaka Prefecture Inside Matsushita Electric Industrial Co., Ltd. F-term (reference) 5H003 AA02 AA03 BB04 BB15 BC01 BD04 5H011 AA02 AA09 CC06 DD03 DD17 FF03 GG02 HH02 5H015 AA02 AA09 CC02 DD01 EE05 EE06 HH01 5H024 AA03 AA14 CC02 CC07 CC14 CC19 DD02 EE03 FE06

Claims (3)

[Claims] 1. A metal positive electrode case having a conductive film formed on an inner surface thereof, a positive electrode mixture accommodated in the positive electrode case and in contact with the conductive film, and a positive electrode mixture facing a positive electrode mixture via a separator. An alkaline battery comprising: a negative electrode arranged in such a manner that the positive electrode mixture contains at least nickel oxyhydroxide as an active material. 2. The positive electrode mixture contains manganese dioxide and nickel oxyhydroxide, the mixing ratio of which is 20 to 90% by weight of manganese dioxide and 80 to 10% of nickel oxyhydroxide.
The alkaline battery according to claim 1, wherein the content is wt%. 3. The alkaline battery according to claim 1, wherein the positive electrode mixture contains 3 to 8 parts by weight of graphite with respect to 100 parts by weight of the active material.