JPS5887781A - Preparation of button-shaped air-zinc cell - Google Patents

Abstract

PURPOSE:To attempt both increased capacity and improved the preservation characteristic of a button-shaped air-zinc cell, by controlling the charging rate of negative-electrode activating substance and electrolytic solution within the range of 75-85%. CONSTITUTION:A cell in constitution of the charging rate of 80% possesses a higher discharge capacity index in comparison with the cells having some other charging rates. A cell which satisfies the condition of volume ratio; the volume of negative electrode activating substance/volume of electrolytic solution 1/2 holds a little charged amount of absolute zinc and a cell having the rate of 1/1 holds a little amount of electrolytic solution and possesses a low flat-voltage due to electrolytic solution rate controlling reaction, and a stable discharge curve can not be obtained. However, it was seen that the capacity reduction in a cell having a charging rate of 90% is not due to the causes in case of the cells having other charging rates but due to some other causes. Therefore, when the charging rate is 75-85% and the volume of charged zinc/volume of electrolytic solution is 1/1.3-1/1.7, can be achieved a high volume is permitted, and a superior liquid-leakproofness can be achieved.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a button-type air-zinc battery, and its purpose is to increase the capacity and improve storage characteristics.

That is, in recent years, as the population ages, the field of medical devices has been attracting attention. Under these circumstances, the demand for hearing aids as a countermeasure for hearing loss is rapidly increasing, and along with this, the demand for power batteries is also increasing.

Conventionally, mercury batteries have been relatively commonly used as a power source for hearing aids.

In the case of mercury batteries, their advantages include low cost per capacity and stable voltage. However, on the other hand, it is relatively heavy as a power source for hearing aids, for example, a power source with a diameter of 11.6 mm x
It has a height of 2.6 plates and is approximately 3.0y-, and the battery capacity is low, so the battery needs to be replaced every two weeks.
thing. θ, and the positive electrode active material used in mercury batteries itself may cause pollution.

A button type air-zinc battery is a battery that has received attention in response to these problems.

A feature of this battery is that since oxygen in the air is used as the active material of the positive electrode, it is possible to increase the internal volume of the negative electrode reservoir, thereby increasing the capacity of the battery. Also, the discharge voltage is relatively stable. It has the advantages of being low-pollution and lightweight.

However, in a sealed battery such as a mercury battery, there is no change in internal volume within the battery, and no problem of swelling occurs. However, in a type of battery that takes in oxygen as the positive electrode active material from an external source, the volume on the negative electrode side is 10~
Increases by 2o%. Therefore, as the discharge progresses, the volume gradually expands, liberating the electrolyte, and further compressing the air electrode, which eventually leaks from the air intake hole of the positive electrode.

The present invention improves the storage characteristics of such a button-type air-zinc battery. Hereinafter, an example of the present invention will be described.
This will be explained using a button type air-zinc battery as an example.

FIG. 1 shows a half-sectional view of the button-type air-zinc battery in this example. In the figure, 1 is a positive electrode case, and 2 is an air intake hole made in the positive electrode case. The hole has a diameter of 0.5 mm. 2-4
It has been opened. 3 is a cellulose-based porous paper placed in the air chamber, which absorbs the electrolyte coming out from the air electrode. 4 is a water-repellent film based on fluorocarbon resin that prevents liquid leakage. 5 is an air electrode using a nickel porous body as a current collector, 6 is a separator, and 7 is an alkaline electrolyte-containing material. 8 is a gasket made of nylon resin and is coupled to the sealing plate 9. 10 is a zinc negative electrode that is a feature of the present invention. That is, the internal volume of the sealing plate coupled with the gasket No. 8 was 230 μβ, and the frozen zinc powder and the alkaline electrolyte were filled therein. At this time, the filling ratio of the amount of zinc powder and the amount of electrolyte to the internal volume of the sealing plate is preferably 76 to 85 inches. The reason for this is that, as shown in Figure 2, when the filling rate in the sealing plate is 76 inches or less, there is no effect on the battery voltage, but the internal resistance increases significantly and its variation becomes extremely large12. It is particularly susceptible to high rate discharge. Further, regarding the internal resistance value, almost no difference was observed when the filling rate was 75 inches or more.

On the other hand, if the filling rate is 96% or more, leakage will occur immediately after battery assembly. Further, in a battery with a filling factor of 86 or more, no liquid leakage is observed immediately after discharge, but when the discharge depth reaches 70 or more after discharge, liquid leakage is observed from the positive electrode plate. It has been found that this degree increases as the filling rate of the negative electrode into the sealing plate increases. Therefore, the filling rate into the sealing plate is 7
6 to 85 inches are the most excellent in terms of battery characteristics and leakage resistance.

Note that the filling rate was calculated as follows.

Filling rate = Volume of zinc powder + Volume of mercury used for freezing + Anno vh'
)＠, Amount of dissolved solution: Internal volume of the sealing plate x 100 On the other hand, in order to increase the capacity of the battery, it is necessary to efficiently fill the limited sealing plate with the negative electrode active material and alkaline electrolyte. . Moreover, considering the reaction of zinc, a large amount of electrolyte is required, and the volume ratio of zinc to the amount of electrolyte becomes large. Therefore, we performed an experiment using a two-way arrangement to determine the volume ratio of the negative electrode active material and electrolyte in the sealing plate, and found that for every 1 volume of the negative electrode active material, the electrolyte was
．． It has been found that a value of 3 to 1.7 is most suitable.

In other words, when the ratio is 1.3 or less, when the battery is discharged, the discharge curve loses the ゛V-flatness (°), especially during high-rate discharge.Also, at the end of discharge, the electrolyte becomes rate-limiting, resulting in a two-stage curve. .

On the other hand, if the ratio of the electrolytic solution is set to 1.7 or more, the filling amount of curved lead will decrease, and free electrolytic solution will exist in the sealing plate.
A leakage phenomenon occurs when the positive electrode group and the negative electrode group are sealed together. In addition, as the depth of discharge increases, the electrolyte is pushed by the swelling of the negative electrode, causing leakage.

Therefore, here, the filling rate to the inner volume of the sealing plate is 80%, and the amount of zinc is 6Bom9. The volume ratio of the negative electrode active material and the electric Wr solution is 1
It was set to 1,6. The electrolyte used was 10M KOH.
Zinc oxide was used in this method.

Next, the effects of the present invention will be described. Structure of the present invention [mu]
In other words, by changing the filling rate and volume ratio with a configuration in which the filling rate to the inner volume of the sealing plate is 80 and the volume ratio of the negative electrode active material to the electrolyte is 1:1.5, Table 1 These A~ The batteries shown in Figure 1 were prototyped using various constructions, and their characteristics were evaluated.

Table 2 shows the internal resistance values after battery assembly and aging at a temperature of 46° C. for 16 hours.

Table 2 As a result, for configurations C and D with a filling rate of 70%, the internal resistance was 3.3 to 5. o8Ω, and it can be said that not only is the value high, but its variation is also extremely large.

When the filling factor of A, F, G, H, and I becomes 8Q or higher in the configuration, the value is low and the fluctuation is small and stable.

The reason for this is thought to be that the adhesion of the elements constituting the battery is affected by the filling rate.

Table 3 shows the capacity index with the configuration of A as 100 when discharging with a 620Ω resistor. In addition, the final voltage is 1.1
v.

Table 3 As a result, in configurations C and D with a filling factor of 70, only a lower value was obtained than in configuration A because the internal resistance was high. This is a result of the absolute amount of zinc being small as the filling rate is low.

E', A, F, G with a filling rate of 80%,
At H and I, the discharge capacity index is higher than at other filling rates.

Among these, those with negative electrode active material volume/electrolyte volume = 1/2 have a small amount of absolute zinc to be filled, and those with 1/1 have little electrolyte discharge, resulting in a rate-limiting reaction of the electrolyte, resulting in a low flat voltage.
A stable discharge curve cannot be obtained.

However, at a filling rate of 9oφ, it became clear that the capacity reduction was not due to Harada like the other filling rates, but was due to other causes.

i.e. as mentioned before Zn+-02-Zn.

From the discharge reaction, 02 is absorbed from the outside air, and as the discharge progresses, the volume on the negative electrode side expands, which presses the catalyst layer, and furthermore pushes the electrolyte on the negative electrode side. There is no function of 02, and 02 is rarely supplied.

As a result, the battery becomes suffocated, gas is generated from the positive electrode due to the potential of the negative electrode, and this eventually causes leakage from the air holes.

This tendency becomes larger as the discharge rate becomes higher.

Therefore, the discharge capacity index also becomes low. Judging overall,
At a filling rate of 70%, there is a problem in terms of capacity, and at a filling rate of 90%, the capacity is low and leakage is likely to occur.

Table 4 shows the number of leaks immediately after assembly (12 samples each).

Table 4 As a result, 7 to 9 leaks were observed immediately when the filling rate was 90% or higher. Moreover, as mentioned above, 180Ω, 300Ω
When high-rate discharge of Ω occurred, even batteries that did not immediately leak leaked from the air holes.

By the way, in mercury batteries and silver batteries, even when the filling rate of the sealing plate reaches 90%, no liquid leakage is observed immediately after discharge, during discharge, or after discharge, which is a problem peculiar to button-type air-zinc batteries. No tendency was observed when the filling rate to the sealing plate was 76 to 85%.

Further, similar results were obtained when the volume ratio of zinc to electrolyte was 1/1.3 to 1/L7.

That is, when the ratio is 1/1, the amount of electrolyte is smaller than the amount of zinc to be filled, so the reaction of zinc becomes rate-limiting to the electrolyte, the discharge curve becomes a two-step curve, and the flatness of the battery voltage is lost. Further, in case of 1/2, the absolute amount of zinc filled is small and the amount of electrolyte is large, so the discharge capacity is small.

Therefore, as shown in the present invention, when the filling rate is 76 to 85 cm and the volume of zinc to be filled/volume of electrolyte is 1/L3 to 1/L7, it is possible to have a high capacity and excellent leakage resistance. .

[Brief explanation of drawings]

FIG. 1 is a partial sectional view of a button-type air-zinc battery, and FIG. 2 is a diagram showing the relationship between the filling rate of the negative electrode into the sealing plate and the internal resistance. 1...Positive electrode case, 2...Air intake hole,
3... Porous paper, 4... Water repellent membrane, 5...
...Air electrode, 6. River... Separator, 7...
Liquid-containing agent, 8... Gasket, 9... Sealing plate, 10... Negative electrode active material. Name of agent: Patent attorney Toshio Nakao (1st person)
Figure 2 @ Goku/l Kei, 0 light r die rate (Kari) to B provisional circle

Claims (1)

[Scope of Claims] (11) Internal volume of a negative electrode storage container that uses oxygen as the positive electrode active material, frozen zinc powder as the negative electrode active material, and alkaline aqueous solution as the electrolyte, and stores the negative electrode active material and the electrolyte. A method for manufacturing a button-type air-zinc battery, characterized in that the filling rate of the negative electrode active material and electrolyte is regulated to 75. to 86 cm. (2) A negative electrode stored in the negative electrode storage container. Volume of active material 1
2. The method for manufacturing a button-type zinc-air battery according to claim 1, wherein the electrolyte volume is regulated to a range of 1.3 to 1.7.