JPS60240056A - Alkaline-manganese cell - Google Patents

Abstract

PURPOSE:To increase the conductivity between a positive-electrode can and the positive-electrode black mix, decrease the carbon content of the positive-electrode black mix in response to that, increase the discharge capacity, reduce the internal resistance, and increase the short-circuit current by forming a conductive film on the inner surface by forming a conductive film on the inner surface of the positive-electrode can. CONSTITUTION:A conductive film 2 is formed on the inner surface of a positive- electrode can 1, and the positive-electrode black mix 3 is in contact with this conductive film 2. This conductive film 2 improves the electrical contact between the positive-electrode black mix 3 and the positive-electrode can 1 and keeps the conductivity between them high. For the conductive film 2, a film dispersed with a carbon series as a conductive component in vinyl acetate resin as a binder, for example, is used. For the positive-electrode black mix 3, manganese dioxide as an active material and carbon as a conductive agent are mixed in a wt% range of 9/1-32/1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an alkaline manganese battery that uses manganese dioxide as a positive electrode active material, zinc as a negative electrode active material, and an alkaline aqueous solution as an electrolyte.

As is well known, this type of alkaline manganese battery generally uses a positive electrode mixture of manganese dioxide as an active material and carbon as a conductive agent. This carbon (graphite, etc.) has the effect of increasing the conductivity between manganese dioxide particles and the conductivity of manganese dioxide and the positive electrode can. This can reduce the internal resistance of the battery and increase the short circuit current. However, mixing carbon into the positive electrode mixture reduces the amount of manganese dioxide as an active material within the limited volume of the positive electrode mixture, reducing the discharge capacity of the battery.

Therefore, the carbon content is adjusted depending on the intended use of the battery, with batteries placing emphasis on high-load performance having a higher content, and batteries placing emphasis on tIi capacitance lowering the content. However, if the carbon content is less than 10% by weight based on the solid content of the positive electrode mixture, the internal resistance will become extremely large and the basic performance of the battery will not be met.
In manganese batteries, 10% or more of carbon is contained in the positive electrode mixture.

As is clear from the above explanation, in this type of alkaline manganese battery, the amount of manganese dioxide as an active material can be increased without decreasing the amount of manganese dioxide (maintaining the discharge vessel as large as possible), and increasing the conductivity on the positive electrode side. A major technical challenge is to improve performance by reducing internal resistance and increasing short-circuit current.

This invention was made in view of the above technical problem,
The purpose is to maintain a high capacity of manganese dioxide as an active material, and to realize an alkaline manganese battery with low internal resistance and high short-circuit current.

In order to achieve the above object, the present invention sets the content of carbon as a conductive agent to 3 to 1% relative to the solid content of the positive electrode mixture.
0% by weight, and a conductive film is formed on the inner surface of the positive electrode can that is in contact with this positive electrode mixture.

Hereinafter, embodiments of the present invention will be described in detail based on the drawings.

1 and 2 show the structure of a cylindrical alkaline manganese battery according to the invention. A positive electrode mixture 3 formed into a donut shape by mixing manganese dioxide (electrolytic manganese dioxide: EMD) and carbon (graphite, etc.) is first loaded into a bottomed cylindrical positive electrode can 1 that also serves as a battery case. A cylindrical leverator 4 made of a boria[l-pyrene nonwoven fabric or the like is disposed within the hollow portion of the positive electrode mixture 3, and is impregnated with an alkaline electrolyte of KOH or NaOH. Further, the separator 4 is filled with a gel-like negative electrode mixture 5 which is mainly composed of zinc powder and mixed with an alkaline electrolyte. A current collector rod 9 is inserted into the center of this negative electrode mixture 5. Then, the negative electrode terminal plate 8 is fitted into the upper opening of the positive electrode can 1 through the seal gasket 7, and the open edge of the positive electrode can 1 is curled inward to form the inside of the battery. Sealed.

In the battery according to the present invention, as shown in FIG.
A conductive film 2 is formed on the inner surface of the positive electrode can 1, and the positive electrode mixture 3 comes into contact with this conductive film 2. This conductive film 2 improves electrical contact between the positive electrode mixture 3 and the positive electrode can 1, and maintains high electrical conductivity therebetween.

As the conductive film 2, a film in which, for example, vinyl acetate resin is used as a binder and carbonaceous material 3- is dispersed therein as a conductive component is used.

Moreover, as mentioned above, the positive electrode mixture 3 in this invention is
A mixture is used in which manganese dioxide as an active material and carbon as a conductive agent are mixed in a weight ratio in the range of 9/1 to 32/1. In other words, the carbon content is set in the range of 3 to 10% by weight based on the solid content of the positive electrode mixture 3.

If the carbon content is 10% or more, the capacity of manganese dioxide will be significantly reduced, resulting in a large decrease in discharge capacity, which is not preferable. Furthermore, if the carbon content is 3% or less, the conductivity in the positive electrode mixture 3 will be too low even with the conductivity improvement effect of the conductive film 2, resulting in an increase in internal resistance and a short circuit current. The decrease becomes noticeable.

As described above, in this invention, by forming the conductive film 2 on the inner surface of the positive electrode can 1, the conductivity between the positive electrode can 1 and the positive electrode mixture 3 is increased, and the positive electrode mixture 3 is increased by that amount. The carbon content is reduced, the discharge capacity R is increased, and the internal resistance is reduced to increase the short circuit current. The table below is an experimental summary showing the effects of this invention. In this experiment, the ratio of manganese dioxide and carbon (graphite powder with an average particle size of 157 (J)) was varied in six steps from 7/1 to 65/1, and the above-mentioned conductive coating was applied to the inner surface of the positive electrode can. Formed (
This is a discharge test for a total of 12 types of LR6 type alkaline manganese batteries, including A) and non-forming batteries (B). The test data includes short circuit current and 10Ω load/0.
Continuous discharge time at 9v final voltage.

−7− From this experimental data, the following can be determined. If the carbon content is increased, the conductivity of the positive electrode mixture will be increased, and the short circuit current will be increased. However, when the carbon content m is increased to 10% or more, there is not much difference in short circuit current between the battery (A) with a conductive coating and the battery (B) without it. When the carbon content is reduced to 10% or more, the effect of the conductive film becomes significant. The short circuit current of the battery (A) of the present invention with a carbon content of 10% is 14. OA, which is approximately the same as the short circuit current of 13.9 A of the conventional battery (B) with a carbon content of 12.5%.

Therefore, the battery of the present invention has a higher discharge capacity due to the lower carbon content.

In addition, the continuous discharge time under a 10Ω load is longer in the battery with a conductive film (A>) than in the battery without it (B). However, if the carbon content is increased by 10% or more, (b), when it is 13% or less, the performance improvement effect of the conductive coating becomes slight.

As explained in detail above, according to the present invention, it is possible to maintain a large capacity of manganese dioxide within a limited volume, increase discharge capacity, increase short circuit current, and sufficiently reduce internal resistance. A miniaturized alkaline manganese battery can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an example of an alkaline manganese battery to which the present invention is applied, and FIG. 2 is an enlarged sectional view of the main part of FIG. 1... Positive electrode can 2... Conductive coating 3.
...Positive electrode mixture 4...Separator 5...
... Negative electrode mixture 7 ... Sealing gasket 8.
... Negative terminal plate 9 ... Current collector rod Patent applicant Tomito Denki Kagaku Co., Ltd. Agent Patent attorney - Kensukeichi Shiro 〇 - 8 - Figure 1 Figure 2

Claims (1)

[Claims] (1) In an alkaline manganese battery that uses a positive electrode mixture consisting of manganese dioxide as an active material and carbon as a conductive agent, the carbon content is set in the range of 3 to 10% by weight based on the solid content of the positive electrode mixture. In addition, an alkaline manganese battery characterized in that a conductive film is formed on the inner surface of the positive electrode can that is in contact with the positive electrode mixture.