JPS60241646A - Alkali-manganese cell - Google Patents

Abstract

PURPOSE:To reduce the inner resistance of cell while to increase the shortcircuit current by containing specific amount of graphite powder having specific grain size as conductive agent into active substance or manganese dioxide. CONSTITUTION:Graphite powder having average grain size of 2-20mum is employed as carbon to be mixed as conductive agent into active substance or manganese dioxide. The content of carbon is made to be 3-8wt% against solid state component to produce positive pole black mix. which is employed in alkali.manganese cell. Consequently, the capacity of manganese dioxide in limited volume is maintained high to increase the discharge capacity resulting in a cell having sufficiently low inner resistance and increased shortcircuit current.

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 increases the conductivity between manganese dioxide particles, and
It acts to increase 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, when carbon is mixed into the positive electrode mixture, m of manganese dioxide as an active material is reduced by that amount within the limited volume of the positive electrode mixture.
The discharge capacity of the battery decreases. Therefore, the carbon content is determined by WAv depending on the purpose of use of the battery, and the content is increased for batteries that place emphasis on high load performance, while it is lower for batteries that emphasize discharge @ rate.

Conventionally, the average particle size of the carbon was 25 to 50I.
Graphite powder having a relatively large particle size of about U is used, and carbon is mixed as an S-type agent in an amount of at least 10% by weight based on the solid content of the positive electrode mixture. For carbon with a relatively large particle size, if the content is less than 10%, the internal resistance will become extremely large and the basic performance of the battery will not be met.
% 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 conductivity of the positive electrode side is improved and the internal A major technical challenge is to improve performance by reducing resistance and increasing short-circuit current.

This invention was made in view of the above technical problem,
The purpose of this is to maintain a large capacity of manganese dioxide as an active material, and also to have a low internal resistance and short circuit 1! The aim is to realize an alkaline manganese battery with a large flow rate.

In order to achieve the above object, the present inventors conducted experiments by varying the particle size and spacing of carbon included in the positive electrode mixture, and as a result, compared to the conventional one with an average particle size in the range of 2 to 20 m. By using graphite powder with a small particle size and reducing the carbon content to 3 to 8%, which is lower than before, it was possible to realize an alkaline manganese battery with good performance.

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

This invention is not limited to the geometric configuration of the battery;
Of course, the present invention can be applied to batteries having the same structure as conventional ones. As an embodiment of the present invention, the drawings show the structure of a cylindrical alkaline manganese battery.

In a bottomed cylindrical positive electrode can 1 that also serves as a battery case, a positive electrode mixture 3 formed into a donut shape by mixing manganese dioxide (electrolytic manganese dioxide: FMD), carbon, graphite powder, etc. is first stagnated. .

A cylindrical separator 4 made of polypropylene nonwoven fabric or the like is arranged in the hollow part of the positive electrode mixture 3, and this
An alkaline electrolyte of OI-1 or NaOH is impregnated. Furthermore, 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 or the like. A current collector rod 9 is inserted into the center of this negative electrode mixture 5. A negative terminal plate 8 is fitted into the upper opening of the positive electrode can 1 via a sealing gasket 7, and the inside of the battery is sealed by curling the opening edge of the positive electrode can 1 inward.

As mentioned above, this invention is based on an alkali solution having the structure shown in the figure.
In a manganese battery, the carbon contained in the positive electrode mixture 3 is graphite powder with an average particle size in the range of 2 to 20 ttp, and the carbon content m is 3% relative to the solid content of the positive electrode mixture 3.
It is characterized by having a content in the range of 8% by weight.

Furthermore, if a conductive film is formed on the inner surface of the positive electrode can 1 with which the positive electrode fiber 3 contacts, the battery performance can be further improved as described later.

By making the average particle size of carbon smaller than 20 m, the contact between the carbon particles and the manganese dioxide particles is improved, and the current collection efficiency for manganese dioxide can be made sufficiently high with a small amount of carbon. As a result, even if the carbon content is 8% or less, the internal resistance can be lowered and the short circuit current can be increased.Moreover, the amount of manganese dioxide as an active material is increased by the amount of carbon content, and the amount of manganese dioxide as an active material is increased. Capacity increases. However, the carbon content is 3%
If the carbon content is smaller, the conductivity on the positive electrode side will be greatly reduced, so the carbon content is preferably in the range of 3 to 8%.

Furthermore, if the average particle size of carbon is smaller than 2 m, the bulk density of carbon will be extremely reduced, resulting in poor filling properties, reduced molding density, and as a result, reduced discharge capacity.

Therefore, the average particle size of carbon is appropriately in the range of 2 to 20 ttpt.

The table below shows experimental results showing the effects of this invention.

In Experimental Example (2), the carbon content (m) was varied in six steps in the range of 12.5 to 1.5%, and the average particle size of carbon was 5μ (A) and 30m (B). This is a discharge test on 12 types of LRG type Ashika Ringan batteries in total h1. The test data are the short circuit current, the continuous discharge time at a 5Ω load and a final voltage of 0.9V, and the continuous discharge time at a 10Ω load and a final voltage of 0.9V.

Experimental example (2) is a case in which a conductive film is formed on the inner surface of the positive electrode can 1, and the other conditions are exactly the same as in experimental example I. The following is understood from this experimental data. Increasing the carbon content improves the conductivity of the positive electrode mixture, resulting in an increase in short-circuit current. Comparing the short-circuit current of a battery with a small carbon particle size (A>) and a battery with a large carbon particle size (B), the short-circuit current increases with the smaller carbon particle size because the current collection efficiency increases.However, when the carbon content is 10% or more When there is a large amount, there is almost no difference in the effective current between the two.Carbon content ff18.0%.

In the cases of 6.0% and 3.0%, the short-circuit current of the battery with small carbon particle size (A> is clearly larger than that of battery (B). This effect is clearly demonstrated by the experimental example in which a conductive film was formed. It is more noticeable in H.

Furthermore, when looking at the continuous discharge time under 5Ω and 10Ω loads, when the carbon content is 10% or more, there is only a slight difference between the battery <A) with a small carbon particle size and the battery (B) with a large carbon particle size. However, the carbon content is 8.0%
, 6.0% and 3.0%, battery (A) with small carbon particle size clearly has better results than battery (B)1. This effect also reflects the experimental example (■). is more noticeable.

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]

The figure is a sectional view of a cylindrical battery as an example of an alkaline manganese battery to which the present invention is applied. 1...Positive electrode can 3...Positive electrode mixture 4...
... Separator 5 ... Negative electrode mixture 7 ...
... Sealing gasket 8 ... Negative terminal plate 9.
...Collector rod patent applicant Fuji Electrochemical Co., Ltd. Agent Patent attorney - Kensuke Shiro

Claims (2)

[Claims] (1) In an alkaline manganese battery using a positive electrode mixture of manganese dioxide as an active material and carbon as a conductive agent, the carbon has an average particle size of 2 to 2011I
An alkaline manganese battery comprising graphite powder in the range of &, wherein the carbon content is in the range of 3 to 8% by weight based on the solid content of the positive electrode mixture. (2) Claim 1, 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.
Alkaline manganese battery as described in section.