JPH02148569A - Alkali battery - Google Patents

Abstract

PURPOSE:To reduce diversity in battery capacity by making bulk density and grain size of spherical amalgam zinc powder to be used for a negative electrode those prescribed so as to improve weighing accuracy thereof. CONSTITUTION:Amalgam zinc powder has its bulk density in the range 5 to 4.5g/cc and its grain size in the range 40 to 150Mesh while a difference of the upper limit value and the lower limit value of grain size is in the range of 40Mesh. Weighing of the amalgam zinc powder to be used for one battery is so performed that the amalgam zinc powder dropping of itself from the bottom of a hopper is cut by rubbing with a weighing plate having a hole of fixed volume in order to measure the volume to be filled in this hole. The amalgam zinc powder is cut by rubbing causing no unevenness on its upper layer surface part always flatwise at the hopper bottom part so that weighing diversity is suppressed. Thereby, a negative electrode having correct volume is secured so that diversity in battery capacity can be suppressed.

Description

[Detailed Description of the Invention] (Field of Industrial Application) The present invention relates to an alkaline battery that improves the accuracy of weighing negative electrode zinc during battery assembly and makes it possible to obtain electric capacity with less variation. .

(Prior Art) Alkaline batteries using zinc powder as a negative electrode are classified into silver oxide batteries, alkaline manganese batteries, mercury batteries, air batteries, and the like.

Generally, the above-mentioned alkaline batteries are designed so that the capacity of the positive electrode is larger than that of the negative electrode. This is because after the battery life has expired, if the above-mentioned capacity relationship were reversed, the water in the electrolyte would decompose due to the hydrogen overvoltage, hydrogen gas would be generated, and the battery would swell and explode. This is to prevent this from occurring, as it may pose a danger.

In order to maintain the above-mentioned capacity relationship, it is necessary to take into consideration the capacitance variations between positive and negative types, that is, the ff1ffi variations at both extremes due to the process, and design so that the volume 1 distributions at the two extremes do not overlap beyond a certain probability. Here, the free space is dominated by the negative electrode capacity in any case, and therefore, suppressing negative electrode capacity variations is a common problem related to all alkaline batteries.

Conventionally, negative electrode zinc powder has been weighed by mass weighing using a scale ff1lffi that includes parts such as a hopper, a weighing plate, and a nozzle.

The specific structure of this machine is to reciprocate the zinc powder that naturally falls from the bottom of the hopper in parallel with a scale plate with a certain volume of holes, fill the holes with zinc powder, and scrape the zinc powder with the bottom of the hopper. After that, zinc powder on a scale plate is allowed to fall naturally into the negative electrode container through a hole provided at a separate location and a nozzle connected below the hole.

However, up until now, common atomized zinc in the form of a flattened or rod-like structure has been used. In Japanese Patent Application Laid-open No. 62-31951, 4
There is also a description of using substantially spherical zinc particles of 8 to ao+esh.

[Problem to be solved by the invention]

However, because the conventional weighing method uses flattened or rod-shaped zinc powder, there are large variations in weighing. For this reason, the center value of the positive electrode capacity had to be set considerably larger than the specified battery capacity, and as more positive electrode active material was incorporated into the battery than the original specified capacity, the following problems arose. . First, since a large space is required for the positive electrode, there is no margin in the specified dimensions, making battery design difficult. Second, the cost of the battery increases as the amount of positive electrode active material increases.

This effect is particularly significant in expensive silver oxide batteries.

Next, since the battery capacity is controlled by the negative electrode container, variations in the weight of the zinc powder lead to variations in the capacity of the battery, which poses a problem in quality characteristic values.

In the future, as batteries become smaller and thinner, the accuracy of weighing zinc powder will become an increasingly important factor than ever before.

The present invention is intended to improve the above-mentioned problems, and aims to improve the weighing accuracy of the negative electrode zinc chloride powder, achieve a battery capacity with less variation, and a compact size with plenty of room in the specified dimensions. The purpose is to provide a thin alkaline battery.

[Means to solve the problem]

In order to solve these problems, the present invention uses spherical zinc chloride powder, has a bulk density of 3.5 to 4.5 g/cc, and has a
An alkaline battery characterized by using a negative electrode that is weighed by mass weighing using zinc chloride powder that has a particle size of ~150 Mesh and is classified into a particle size range in which the difference between the upper limit and the lower limit is within 40 Hcsh. be.

[For production]

In the present invention, by using the above-described zinc powder, the fluidity of the zinc powder itself becomes good, and a constant amount of zinc powder can be constantly supplied from the hopper to the scale plate. In addition, since the upper surface of the zinc powder in the measuring hole of the weighing plate does not become uneven and is always ground flat at the bottom of the hopper, variations in weighing can be suppressed and alkaline batteries with a uniform electrical capacity can be supplied. It is possible.

〔Example〕

A silver oxide battery according to an embodiment of the present invention will be explained based on the drawings.

In the figure, 1 is a positive electrode whose main active material is silver oxide, 2 is a positive electrode case made of iron plated with nickel, and 3 is 80-1 according to the present invention.
20) A negative electrode made of spherical zinc oxide powder 8 with a bulk density of 4.0 g/CC classified into 1 esh, a liquid holding material that holds 1 to 10 heavy electrolytes, and 7 is an insulating backing.

This invention battery A and the conventional battery density 3.3g
/CC flat or rod-shaped particle size distribution 80-120M
The variation in battery capacity of conventional battery B using esh's zinc chloride powder as the negative electrode is shown in detail by comparing it with a silver oxide battery (5R5123W) with a diameter of 5.8 m and a height of 1.25 mm.

This table shows the average value and variation σ of the battery capacity when 5R512SW is continuously discharged to 240Ω at 20°C.

Next, Table 1 shows the relationship between the weight variation (σ) of the spherical zinc powder 8, the bulk density (g/cc), and the particle size (Mesh).

Separator 6 made of a graft polymer film of Ren is shown in Table 1 Weighing variation (σ) (IAIl) Table 2 Weighing variation (σ) From Table 1, when the bulk density becomes less than 3.59/CC, the weighing variation suddenly worsens. The zinc chloride powder having a bulk density of 3.0 g/CC cannot be said to be spherical, but rather has a rod shape.

Moreover, when the bulk density exceeds 4.59/CC, the shape becomes closer to a cube than a sphere, resulting in poor fluidity and large variations in weighing. Next, in terms of particle size, +40)! esh
-150MeS
In h, the powder is too fine, causing scattering and clogging, and poor fluidity and poor balance.

Next, Table 2 shows the relationship between the weighing variation (σ) and the particle size.

From Table 2, it can be seen that when the mesh width exceeds 40, the square cut surface becomes uneven and the weight variation suddenly becomes large.

(Effect of the invention) From the above results, it is clear that the battery A of the present invention is different from the conventional battery B.
Compared to conventional battery B, the weight variation of zinc chloride powder is smaller.
175 or less, which is about 2% or less of the battery capacity, making it possible to obtain an alkaline battery with very little variation in battery capacity. Further, the present invention can be carried out using a conventional weighing method without any need for improvement.

As described above, according to the present invention, an alkaline battery with excellent weighing accuracy and small variation in electric capacity can be obtained without changing the weighing ratio.

[Brief explanation of the drawing]

The drawing is a sectional view of a silver oxide battery 5R5123W using a negative electrode in an example of the present invention. DESCRIPTION OF SYMBOLS 1...Positive electrode, 3...Negative electrode, 5...Separator, 8...Zinc chloride powder.

Claims (1)

[Claims] In an alkaline battery using spherical zinc oxide powder (8) for the negative electrode (3), the spherical zinc oxide powder (8) has a bulk density of 3.5 to 4.5 g/
cc, the particle size is within the range of 40 to 150 Mesh, and the difference between the upper limit and the lower limit of the particle size is within the range of 40 Mesh.