JPH0745273A - Button-shaped silver oxide battery - Google Patents

Abstract

PURPOSE:To improve mechanical strength of a compound by setting a molded compound external diameter of a positive electrode, pressure-molded in a tablet shape, to the molded external diameter or more after constituting a battery seal. CONSTITUTION:A compound, formed with a silver layer by reducing a surface of silver oxide grains, is pressure molded into a tablet shape, to obtain a positive electrode, and after it is inserted into a positive case 1, it is contracted about 0 to 0.1mm in a diametric direction. Thus by increasing molding density of a positive electrode compound 2 at sealing time, mechanical strength of the compound is improved. Accordingly, a battery excellent in a fluid leakage resistance characteristic with high positive electrode capacity is obtained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improved silver oxide battery, and more particularly to a method for constructing a positive electrode.

[0002]

2. Description of the Related Art In recent years, the demand for button type silver oxide batteries is increasing as a power source for cordless and portable devices. Currently, these devices are becoming more sophisticated, and the batteries that are the power sources thereof are also required to have higher capacities. One of the important points is the filling capacity of the positive electrode mixture. Conventionally, when a battery is crimped and sealed, a positive electrode ring as a base is removed to improve the filling volume, or a silver oxide mixture containing carbon as a conductive material is used as a positive electrode mixture. As described in Japanese Patent Laid-Open Publication No. 2003-242242, a mixture having a good filling property in which silver oxide particles are surface-reduced has been used.

[0003]

However, there is a limit to the further increase in capacity even if the above-mentioned method is carried out alone. A method of combining the two is conceivable. However, the mixture obtained by surface-reducing silver oxide particles has less strength at the time of sealing than the mixture using the mixture containing carbon as a conductive material, and therefore has a large deformation and is resistant to liquid leakage. There is a problem that performance is deteriorated.

[0004]

[Means for Solving the Problems] In order to solve these problems, in the present invention, as a result of intensive studies, the surface of silver oxide particles was reduced, and a mixture having a silver layer was pressure-molded into a tablet. Used as a positive electrode, the outer diameter of the mixture is made 0 to 0.10 mm larger than the outer diameter of the mixture measured after the battery is sealed to increase the molding density of the positive electrode mixture at the time of sealing. It has improved mechanical strength.

[0005]

By using this structure, the filling amount of the positive electrode mixture and the strength of the positive electrode mixture can be improved, and as a result, the button type silver oxide battery having a high positive electrode filling capacity and an excellent leakage resistance performance. Is what you can get.

[0006]

Embodiments of the present invention will be described below with reference to the drawings. In the examples, a silver oxide battery SR626 having a diameter of 6.8 mm and a height of 2.6 mm was used. FIG. 1 is a sectional view of SR626. In FIG. 1, 1 is a positive electrode case and 2 is a positive electrode active material. 3 is a separator layer, 4 is a negative electrode active material, 5
Is a sealing plate which also serves as a negative electrode terminal, and 6 is an insulating packing.

Regarding the battery of this embodiment and the battery of the conventional example,
The results of examining the positive electrode filling capacity are shown in (Table 1).

[0008]

[Table 1]

Battery A in Table 1 is the battery of the present invention. The manufacturing process is as follows. First, the surface is selectively reduced with hydrazine dissolved in an organic solvent, and the positive electrode mixture is formed by pressing the silver oxide with the silver layer formed into tablets into the positive electrode case, and the outer circumference of the positive electrode case is Direction, and the positive electrode case and the positive electrode mixture are brought into close contact with each other to form a positive electrode. Here, the reduction rate was 3% by weight. On the other hand, a sealing plate also serving as a negative electrode terminal and an insulating packing are fitted with a sealing agent interposed, and then a negative electrode active material mainly containing zinc and an alkaline electrolyte are weighed and added to obtain a negative electrode. After that, a separator punched out in a circular shape is placed on the positive electrode, and after fitting the negative electrode, the end of the positive electrode case is caulked to form a battery. Battery B is a battery of a conventional example, and the positive electrode mixture obtained by pressure-molding silver oxide having a silver layer formed by selectively reducing the surface is inserted into the positive electrode case together with the positive electrode ring and then re-added. The positive electrode was formed by pressure molding. The condition was that constant current discharge of 1 mA was performed at room temperature with zinc as the counter electrode, and the average value and standard deviation value of 50 measured values were shown. From Table 1, it can be seen that the battery A of the present invention has a larger positive electrode capacity than the conventional battery B without the positive electrode ring.

Next, for the battery A of the present invention, the outer diameter Φα of the positive electrode mixture was changed, and the outer diameter Φ of the mixture was measured after sealing the battery.
The results of examining the relationship between the difference Z (Φα-Φβ) from β and the liquid leakage resistance are shown in (Table 2).

[0011]

[Table 2]

If the positive electrode ring is simply removed by the conventional technique of inserting the molded positive electrode mixture into the positive electrode case, Z
<0. In addition, as a reference, the results of the same experiment performed with a mixture using carbon as the conductive material of the positive electrode are listed as Battery C. Note that 50 batteries were prepared for each, and the determination was performed by a color reaction of cresol red every 5 days in an environment of 45 ° C. and 90%. The numbers in the table indicate the number of days when the first one leaked. From Table 2, in the battery A of the present invention, 0 ≦ Z ≦
The leakage resistance is stable in the range of 0.10 mm. If Z <0, which is simply the area excluding the positive electrode ring as in the prior art, deformation occurs when the positive electrode mixture is sealed, and Z>
At 0.10, the liquid mixture cracks when the case is squeezed, so the liquid leakage resistance decreases. On the other hand, in the battery C, the stable region is −0.02 ≦ Z ≦ 0.03.

It is considered that the molding compound containing carbon as a conductive material has strength against the circular surface of the tablet in the force in the vertical direction, but delamination peculiar to carbon is likely to occur in the force in the horizontal direction.

Further, the results of examining the closed-circuit voltage characteristics by changing the surface reduction rate of silver oxide are shown in (Table 3).

[0015]

[Table 3]

The closed-circuit voltage characteristic is a typical condition for use in timepieces, the minimum voltage for 5 seconds is measured at −10 degrees Celsius and a load of 2 k ohms, and the average value and standard deviation value of 50 measured values are measured. showed that. From Table 3, a stable closed-circuit voltage characteristic is obtained at a reduction rate of 1% or more, but it is considered that a reduction rate of about 1 to 5% is appropriate because the smaller the reduction rate, the higher the capacity.

Further, the thickness of the case to be squeezed is 0.1 to
The results of confirming the occurrence of cracks in the mixture by changing Z in the range of 0.25 mm and Z from 0 to 0.10 mm are shown in (Table 4).

[0018]

[Table 4]

From Table 4, it has been found that the plate thickness is preferably 0.2 mm or less, because when the plate thickness becomes large, the force is exerted on the mixture and the mixture is easily broken.

In this embodiment, the positive electrode case was brought into close contact with the positive electrode active material pellets before fitting with the negative electrode, but the same effect was obtained even after the negative electrode was fitted.

[0021]

As described above, by using the constitution of the present invention, it is possible to obtain a silver oxide battery having a high positive electrode capacity and an excellent liquid leakage resistance.

[Brief description of drawings]

FIG. 1 is a sectional view of a battery according to an embodiment of the present invention.

[Explanation of symbols]

 1 Positive Case 2 Positive Electrode Active Material 3 Separator Layer 4 Negative Electrode Active Material 5 Sealing Plate 6 Insulating Packing

Claims (5)

[Claims] 1. A positive electrode is prepared by pressure-molding a mixture having a silver metal layer on the surface of silver oxide particles in a tablet shape, and the outer diameter Φα of the mixture is the outer diameter Φβ of the mixture after the battery is sealed.
Button-shaped silver oxide battery characterized by being equal to or larger than. 2. The relationship between the molding mixture outer diameter Φα and the molding mixture outer diameter Φβ measured after sealing the battery is 0 mm ≦ Φα−Φβ ≦ 0.
The button type silver oxide battery according to claim 1, which is 10 mm. 3. A button-type silver oxide battery according to claim 1, wherein silver oxide whose surface is reduced by 1 to 5% by weight is used. 4. The button-type silver oxide battery according to claim 1, wherein a reducing agent containing hydrazine as a main component is used and silver oxide whose surface is reduced is used. 5. The button type silver oxide battery according to claim 1, wherein the positive electrode case containing the positive electrode mixture has a plate thickness of 0.1 to 0.2 mm.