JPH03201360A - Manufacture of positive electrode mixture for manganese dry cell - Google Patents

Abstract

PURPOSE:To improve discharge performance with the reaction area of a manganese dioxide powder and an electrolyte increased by retaining the electrolyte so far as in fine holes existing on the particle surface of the manganese dioxide powder. CONSTITUTION:Air, retained and fixed on the surface and in the fine holes of a manganese dioxide powder 1, is blown off to the outside to be replaced with an electrolyte 2 by pressure-reduction-treating the manganese dioxide powder 1 in a condition where it is immersed in the electrolyte 2, consequently the contact area of the manganese dioxide powder 1 and the electrolyte 2 can be enlarged. The reaction area of the manganese dioxide powder 1 and the electrolyte 2 in a positive electrode mixture 6 increases by using a slurry-like mixture of the manganese dioxide powder 1 and the electrolyte 2 obtained by the pressure reduction treatment. This permits the improvement of battery discharge performance.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to a method for producing a positive electrode mixture for manganese dry batteries.

<Conventional technology> For manganese batteries, manganese dioxide powder.

An electrolytic solution made by dissolving zinc chloride, ammonium chloride, etc. in water is added to a mixed powder mainly composed of carbon powder, and after mixing these, the mixture is press-molded into a predetermined shape to create a positive electrode mixture. This positive electrode mixture is housed in the negative electrode zinc fn via a paper separator made of paper coated with adhesive.

Conventionally, the above-mentioned positive electrode mixture is made by first dry-mixing powders such as manganese dioxide powder, carbon powder, and ammonium chloride powder, and then wet-mixing them by adding the required amount of electrolyte. - used in membranes.

As manganese dioxide powder, electrolytic manganese dioxide, which is in the X-ray γ form obtained by electrolysis of an aqueous solution of manganese sulfate, is widely used, and chemical manganese dioxide powder, which is a fine powder and has a wide surface area, is also used.

Since this type of manganese dry battery uses an aqueous electrolyte, the amount or absorbency of the electrolyte in the positive electrode mixture is important, and has a large effect on battery performance.

For this reason, the above carbon powder used in the positive electrode mixture is
Acetylene black, which has a large surface area and can hold a large amount of electrolytic waves, is commonly used.

<Problems to be Solved by the Invention> However, according to the research of the present inventor, it has been found that there are the following problems.

That is, on the surface of the above manganese dioxide powder, there are 7 pores (pores) that are deeply embedded inside the particles, and the total surface area is quite large, about 35 rrr/g.
However, when using the method of dry mixing → wet mixing as described above, the electrolyte injected into the positive electrode mixture is only held between the particles of manganese dioxide powder, etc., and the electrolyte is (r) It is not possible to enter into the many pores of the

Since the electrolyte is not retained in these pores, the contact area between the manganese dioxide powder and the electrolyte is limited to a small area, and as a result, the electrochemical reaction area between the two is limited. This is an obstacle to improving the performance of manganese dry batteries.

In particular, when acetylene black powder with a large surface area is used as described above, and a power solution is injected into the mixture of this acetylene black powder and manganese dioxide powder, a considerable amount of the electrolyte is retained on the acetylene black side. This tendency is large because it is stored away.

This invention makes it possible to increase the reaction area between the manganese dioxide powder and the electrolyte by retaining the electrolyte in the pores existing on the particle surface of the manganese dioxide powder, thereby improving the discharge performance. The object of the present invention is to provide a method for producing a positive electrode mixture for manganese batteries.

Means for Solving the Problems> The method for producing a positive electrode mixture for manganese batteries of the present invention involves immersing manganese dioxide powder in an electrolytic solution and treating it under reduced pressure to eliminate air on the surface and in the pores of the manganese dioxide powder. The gist of this method is to replace the electrolyte with the electrolyte, and mix the obtained slurry mixture of manganese dioxide powder and electrolyte together with other positive electrode mixture constituent materials.

As the manganese dioxide powder, for example, electrolytic manganese dioxide 111 or a mixture thereof with chemical manganese dioxide may be used.

Examples of the other positive electrode mixture constituent materials include acetylene black powder. In the case of ammonium chloride-based manganese dry batteries, ammonium chloride may be added together with acetylene black. Further, an additional electrolyte may be added and mixed as necessary.

On the other hand, the electrolytic solution used in the depressurization process may have the same composition as conventional ones, that is, one made by mixing water with zinc chloride, ammonium chloride, etc. in an appropriate ratio.

In the coercive treatment of the present invention, the reduced pressure is 0 to 50 m111 g
It is sufficient to set the pressure to a certain level. Atmospheric pressure is 50mm! If it is higher than Ig, there is a possibility that the air in the pores of the manganese dioxide powder and the electrolyte may not be sufficiently replaced by the vacuum treatment.

Also, 1ljr immersing manganese dioxide powder in electrolytic waves.
The time depends on the degree of depressurization (atmospheric pressure) and the amount of processing;
Approximately 0 minutes is sufficient. If it is less than 2 minutes, there is a risk that the air in the pores of the manganese dioxide powder and the electrolyte will not be replaced sufficiently.On the other hand, if the depressurization treatment is performed for about IO minutes, the replacement of air and the electrolyte will be almost completed. , further depressurization treatment will only complicate the treatment process.

Effect> As described above, by subjecting the manganese dioxide powder to a reduced pressure treatment while immersed in the electrolyte, the air that was retained and fixed on the surface and within the pores of the manganese dioxide powder is released to the outside and is mixed with the electrolyte. As a result of the substitution, the contact area between the manganese dioxide powder and the electrolyte can be significantly increased.

By using the slurry-like mixture of manganese dioxide powder and electrolyte obtained through this reduced-pressure treatment, the reaction area between manganese dioxide powder and electrolyte in the positive electrode mixture is significantly increased, improving the discharge performance of the battery. be able to.

<Example> Examples will be described below.

Add 40 g of zinc chloride and 5 g of ammonium chloride to 1 (1
In 55 ml of electrolyte solution mixed to 0 ml and stirred, 32
100 g of electrolytic manganese dioxide powder containing 93% or more of 5 mesh or less was charged and completely immersed in the electrolytic solution. Then, the electrolytic solution containing this manganese dioxide powder was heated to an atmospheric pressure of 2
It was left in a reduced pressure (vacuum) environment of On+n11g for 3 minutes, and the air contained in the pores 1a of the manganese dioxide powder 1 was replaced with the electrolytic solution 2, as shown in FIG. 1 (^).

Then, 15 parts by weight of acetylene black was added to 155 parts by weight of the slurry of the manganese dioxide powder and electrolyte obtained by the above vacuum treatment, and the mixture was then pressure-molded into a cylindrical shape to prepare a positive electrode mixture.

Then, as shown in FIG. 1 (13), the positive electrode mixture 6 prepared above was press-fitted into the inside of the zinc can 3 via the paper separator 4 and the bottom paper 5. After that, a carbon rod 7 is driven into the center of the positive electrode mixture 6, a top paper 8 is inserted, and a sealing gasket 9 is inserted.
Then, the positive electrode terminal plate 10 was sequentially placed on the opening of the zinc can, and the negative electrode terminal plate 11 was attached to the bottom of the zinc (+i), and the outer periphery of the zinc row F was contracted and tied using a heat-shrinkable resin tube 12, and finally the exterior m13 was installed to produce an R6P cylindrical manganese dry battery (the battery of the present invention).

In addition, an R6P cylindrical manganese dry battery (comparative battery) was produced in the same manner except that manganese dioxide powder that was not subjected to the above-described pressure reduction treatment was used.

For these two batteries, changes over time in open circuit voltage (V) and terminal voltage (V) when continuously discharged with a resistance of 5 Ω at a temperature of 20° C. were investigated.

The results are shown in Figure 2, and while the open circuit voltage is similar for both, there is a large difference in the continuous discharge test.
When the final discharge voltage is 0.9■, the discharge duration of the comparison battery is approximately 105 minutes, while that of the battery of the present invention is 128 minutes. The performance was improved by about 20%.

The above is an example in which the present invention is applied to a cylindrical manganese dry battery, but it goes without saying that the present invention can also be applied in the same manner to the production of a positive electrode mixture used in a stacked manganese dry battery, for example.

<Effects of the Invention> As described above, according to the present invention, the contact area between the electrolyte and the manganese dioxide powder in the positive electrode mixture is significantly increased,
As a result of being able to increase the reaction area, it is possible to improve the discharge performance of the manganese dry battery.

[Brief explanation of drawings]

Figure 1 (A) is an explanatory diagram of the state in which manganese dioxide powder is subjected to vacuum treatment by the method of the present invention, Figure 1 (B) is a cross-sectional view of the battery of the present invention, and Figure 2 is a comparison with the battery of the present invention in Examples. It is a graph showing discharge characteristics with a battery. 1... Manganese dioxide powder, 2... Electrolyte, 3...
- Zinc m, 6... Positive electrode mixture, 7... Carbon rod. @1 Figure (A) Figure (B)

Claims (1)

[Claims] 1. Manganese dioxide powder is immersed in an electrolytic solution and treated under reduced pressure to replace the air on the surface and in the pores of the manganese dioxide powder with the electrolytic solution, resulting in a slurry mixture of the manganese dioxide powder and the electrolytic solution. A method for producing a positive electrode mixture for a manganese dry battery, comprising mixing the above with other positive electrode mixture constituent materials.