JPS58117650A - Manufacture of silver oxide battery - Google Patents

Abstract

PURPOSE:To provide a silver oxide battery having decreased internal resistance and increased discharge capacity by forming silver layer on the particle surface by chemically reducing the surface of secondary particle of silver oxide, and assembling a battery using this particle as a positive active mass, and conducting pre-discharge of a battery. CONSTITUTION:Secondary particle of silver oxide having a particle size of 100-400mum is preferable in this invention. This particle is prepared in such a way that primary particle of silver oxide having a particle size of 1.5-10mum is mixed with water, and after moisture is controlled adequately, the mixture is granulated, and balled if necessary, to form the secondary particle. The chemical reduction of the surface of the silver oxide secondary particle is conducted in such a way that particle is dipped in a solution prepared by dissolving hydrezine acting as a reducing agent in ethyl alcohol. Pre-discharge is conducted at constant load discharge or constant current discharge or ac discharge. By this procedure, a battery having decreased internal resistance is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the manufacturing method of a silver oxide battery using monovalent silver oxide as a positive electrode active material, and aims to provide a silver oxide battery with a low internal resistance and a large amount of tJ emitted. Purpose〇 Finely powdered silver oxide with a particle size of around 6 μm is generally used as the positive electrode active material of silver oxide batteries, but this silver oxide powder has rapid fluidity and is industrially used in the mass cutting method. Since it is difficult to cover the scale with a lid, it has been attempted to improve the fluidity by adding phosphorous graphite. However, since the volume occupied by phosphorous graphite is large, there is a problem that the filling capacity of the active material is reduced accordingly, making it impossible to achieve λh packaging.

Therefore, instead of adding phosphorous graphite to improve fluidity, silver oxide was made into secondary particles and tIt! Although fluidity is improved by forming secondary particles, the conductivity decreases due to the reduction or discontinuation of the addition of graphite, and the internal resistance of the battery increases. The problem is that it increases.

Therefore, attempts have been made to reduce the surface of secondary silver oxide particles to form silver J- on the particle surface and to impart conductivity to the positive electrode active material itself, thereby obtaining a battery with low internal resistance and a single device. However, there is a problem in that when pressure molding is performed to an island density of 4, some of the secondary particles are destroyed, part of the silver path is blocked, and the internal resistance is not sufficiently reduced.

In addition, in order to add four utility poles to the positive electrode, it has been proposed that a preliminary discharge be carried out after battery assembly, and an application has already been filed by Hitoshi Motoidetsu. Materials are also consumed, and this type of battery must have a negative electrode regulation pressure, which leads to a significant decrease in the discharge capacity of the battery as a whole, and it is not always possible to achieve a high capacity.

In light of such circumstances, the inventors of the present invention have carried out extensive research on the surface of silver oxide secondary particles, and as a result, the surface of secondary silver oxide particles is chemically reduced to form a silver layer on the surface of the particle, and the surface of this particle has a #M layer. When performing IIEa assembly using silver oxide secondary particles as the positive electrode active material and pre-discharging after assembly, the internal resistance is small;
Itatsutomo K. discovered that a silver oxide battery with a large discharge capacity could be obtained, and completed the present invention.

In other words, in the present invention, conductivity is imparted to the positive electrode active material itself by reduction of the particle surface, and the conductive path partially destroyed by pressure molding is regenerated by preliminary discharge, so that the loss of electricity due to preliminary discharge is reduced. This is much less than when electrical conductivity is imparted only by discharge. In addition, since the addition of phosphorescent graphite is not particularly required, the filling amount of the positive electrode active material increases accordingly, resulting in a larger discharge capacity.Also, since the silver layer formed by reduction becomes porous due to deoxidation, It has good compatibility with the electrolytic solution, improves the discharge utilization rate, and also facilitates the formation of a conductive path through preliminary discharge, making it possible to impart sufficient conductivity to the positive electrode with a smaller amount of discharged electricity.

In the present invention, the silver oxide secondary particles have a particle size of 100
-400 ams are preferably used, and these are made by adding water to secondary silver oxide particles with a particle size of about 1.5 to 10 ams, mixing them, adjusting the moisture appropriately, and then granulating them, and granulating them if necessary. It is obtained by doing K. The surface of the silver oxide secondary particles is chemically reduced by immersing them in a solution prepared by dissolving hydrazine in ethyl alcohol using, for example, hydrazine as a reducing agent. In that case, the amount of return is 1 to 2
It is preferable to set it to about 1 (weight -1 or less).

The preliminary discharge may be a constant resistance discharge, a constant current discharge, or a discharge voltage using alternating current.

Next, the present invention will be explained with reference to Examples.

Example 1 Silver oxide secondary particles of sea bream with an average particle size of 25θμ were mixed with hydrazine.
% ethyl alcohol solution to reduce the particle surface to a silver oxide content of 98.6%.

Next, this silver oxide secondary particle 277q is @ L /lx
A molded body having a diameter of 9 g and a thickness of 0.69 mm was prepared by pressure molding in Step 2, and this molded body was used as a positive electrode as shown below, and a battery having the configuration as shown in Fig. 1 was assembled into a circle.

That is, the above-mentioned positive electrode (1) is inserted into a positive electrode can (2) into which a part of electrolyte is injected, and a separator (3) made of microporous polyglobylene film and cellophane is placed on the positive electrode (1).
) and an electrolyte absorber (4) made of vinylon-rayon mixed paper were placed.

This positive electrode can (2) is attached to a circular gasket (
5), the negative electrode plate (7) K filled with the negative electrode (6) containing 62q of frozen zinc as an active material and the remaining half of the electrolyte is fitted, and the positive electrode case (2) is fitted. ) To tighten the opening local wall inward, curve it and insert an annular gasket (5
) The electrolyte used was an 85% potassium hydroxide aqueous solution in which saponified lead was dissolved.

The battery assembled in this way has a constant resistance of 0.80 lΩ.
rQAh pre-discharged・In addition, the amount of chemical reduction of this battery! 'i corresponds to 0.96 mb, and the total amount including the amount reduced by preliminary discharge is 1.76 mAh.

Table 1 shows the results of measuring the internal resistance (internal resistance at 20° C., hereinafter the same) of this battery.

Comparative Example 1 Silver oxide secondary particles with an average particle diameter of 250% were mixed with hydrazine.
% ethyl alcohol bath solution, silver oxide content was 97.
The surface of the particles was reduced to silver until the particle size became 2 cm.The silver oxide secondary particles 2771+1 were then pressure-molded in the same manner as in Example 1 to obtain a molded body with a diameter of 9M and a thickness of 0.69m. The amount of reduction from silver oxide to silver in this molded body was 1.76 m
Corresponds to Ah.

Next, a battery was assembled by pressing the molded body as described above with the positive electrode in the same manner as in 1-1 Example 1, and the internal resistance was made constant. The results are shown in Table 1.

Comparative Example 2 Silver oxide secondary particles 28OIf with an average particle size of 250μ were @t
A molded body having a diameter of 9 meters and a thickness of 0.69 m was produced by pressure molding at /3t, and a battery was assembled in the same manner as in Example 1 except that the molded body was used as a positive electrode.

After assembly, the internal resistance of the battery after pre-discharge was adjusted, with a pre-discharge ffT equivalent to 1.76 mAh with a constant resistance of 1Ω.

The results are shown in Table 1.

As shown in Table 1 and Kimi 1, both Igenyari have 1.76mA.
However, when using the method of the present invention, a battery with low internal resistance can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing a silver oxide battery according to the present invention. (1)...Positive electrode Figure 1

Claims (1)

[Claims] 1. A method for producing a silver oxide battery, characterized in that silver oxide secondary particles whose particle surfaces are chemically reduced to form a silver layer on the particle surfaces are used as a positive electrode active material, and a preliminary discharge is performed after battery assembly.