JPH10172619A - Air zinc battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air zinc battery in which discharge capacity can be enlarged without impairing the reliability of liquid leak resistance. SOLUTION: A negative electrode active material-filled negative electrode case and a positive electrode can 3 having air holes are integrated via an insulation gasket 4, the plate thickness (a) of at least one part of a positive electrode can 3 bottom portion is made to be thinner comparing with the plate thickness (b) of the other part, and an air diffusion layer 11 is disposed in a recessed portion formed thereby. Preferably, the ratio a/b of the plate thickness (a) to the plate thickness (b) is 0.4 to 0.8. Preferably, the inner diameter (c) of the recessed portion is d-1.0mm<=c<=d+0.5mm against the inner diameter (d) of an insulation gasket opening portion.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zinc-air battery used for a small electronic device such as a hearing aid and a pager, and more particularly to an improvement in a positive electrode can.

[0002]

2. Description of the Related Art Zinc-air batteries and fuel cells are known as batteries using electrodes using oxygen as an active material. In recent years, great attention has been given to the effective use of the global environment and resources, and from this viewpoint, these battery systems that use oxygen have attracted attention as clean power sources. For example, a mercury battery has conventionally been used as a battery for a hearing aid. However, a mercury battery using mercury oxide as an active material has been regarded as a problem, and an air zinc battery has been used as a substitute for the mercury battery.

[0003] Zinc air batteries have a higher energy density per volume than other battery systems, and are about five times as large as alkaline manganese batteries, about three times as much as silver oxide batteries, and about twice as much as mercury and lithium batteries. It is much better. Therefore, this zinc-air battery is required to have a small size, require a large current, and to save the trouble of battery replacement, and its use has been spread to a pegger and a portable medical device. With the miniaturization of electronic devices using the zinc-air battery, there is a demand for a reduction in the size of the battery and a prolongation of the operating time so that the user can use the battery.

[0004] Incidentally, in a zinc-air battery, since oxygen taken in from the air outside the battery is used as a positive electrode active material, the discharge capacity is determined by the amount of the negative electrode active material filled in the battery. Therefore, in order to improve the discharge capacity, it is important how the inner volume of the battery can be increased and the negative electrode active material can be filled more.

As a method for improving the discharge capacity of a conventional zinc-air battery, there is a method in which the entire thickness of the negative electrode case or the positive electrode can constituting the battery is made thinner and the entire space is filled with the negative electrode active material. Further, as shown in Japanese Patent Publication No. 5-72072, by eliminating the air diffusion layer disposed in contact with the air hole inside the bottom of the positive electrode can, the space of the storage portion is eliminated, and the negative electrode active material is accordingly reduced. There is a method that can be used for filling space.

However, a zinc-air battery uses a strong alkaline aqueous solution as an electrolytic solution, so it is necessary to secure sufficient leakage resistance while improving the capacity. However, the above-described method for improving the discharge capacity has a disadvantage that the liquid leakage resistance is sacrificed. In the former method, the strength of the component is inevitably reduced by reducing the thickness of the component, and as a result, the sealing strength is reduced and the liquid leakage resistance is also reduced. The latter method has a drawback that the step of eliminating the air diffusion layer eliminates a step at the bottom of the positive electrode can, so that the adhesion strength between the electrode and the positive electrode can is inferior to a conventional structure having a step.

[0007]

DISCLOSURE OF THE INVENTION The present invention has been proposed to solve the above-mentioned problems, and it has been proposed that the discharge capacity be increased without impairing the reliability of leakage resistance. The purpose is to provide.

[0008]

The zinc-air battery according to the present invention comprises a negative electrode case filled with a negative electrode active material and a positive electrode can having an air hole integrated through an insulating gasket. The thickness a of at least a part of the bottom portion is made thinner than the thickness b of the other portion, and an air diffusion layer is disposed in a recess formed by the thickness a.

As described above, in the zinc-air battery according to the present invention, since the plate thickness a of at least a part of the bottom of the positive electrode can is made smaller than the plate thickness b of the other parts, the battery is resistant to liquid leakage. The strength of the component is maintained with the plate thickness of the effective portion as it is, the reliability of leakage resistance is maintained, and the discharge capacity can be improved by increasing the effective internal volume of the battery.

By the way, the ratio of the thickness a to the thickness b, a /
b is preferably 0.4 to 0.8. If this ratio is less than 0.4, the strength of the component is undesirably reduced. On the other hand, when it exceeds 0.8, the effect of improving the discharge capacity is reduced.

The inner diameter c of the recess is d-1.0 mm ≦ c ≦ d + 0.
It is preferably 5 mm. As the inner diameter of the concave portion is larger, an effective air diffusion layer can be secured and the heavy load characteristic can be improved, but the above range is preferable from the viewpoint of liquid leakage resistance.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a zinc-air battery according to the present invention will be described below in detail with reference to the drawings.

As shown in FIG. 1, a zinc-air battery to which the present invention is applied comprises a negative electrode case 1 filled with zinc as a negative electrode active material and a positive electrode can 3 having air holes 2 via an insulating gasket 4. It is something that has been made. That is, in this zinc-air battery, a negative electrode case 1 containing a gelled negative electrode mixture 5 containing powdered zinc, a porous film 6, an electrode 7, a separator 8, and an electrolyte holding layer 9 are laminated in this order. The positive electrode can 3 formed and stored is integrated with the positive electrode can 3. And this zinc-air battery takes in air from the air hole 2 and uses oxygen as an active material. At least one air hole 2 is appropriately provided, and the number, shape, and arrangement thereof are not particularly limited. Before the battery is used, the air hole 2 is sealed with a seal 1.
0 is sealed.

The above-mentioned positive electrode can 3 is, as shown in FIG.
The plate thickness a of the central portion 12 at the bottom is made thinner than the plate thickness b of the outer peripheral portion 13, and the air diffusion layer 11 is disposed in a concave portion 14 formed thereby. This allows
In the positive electrode can 3, the effective internal volume of the battery can be increased by the plate thickness ba, and the filling amount of the negative electrode active material can be increased.

The ratio a / b of the thickness a of the bottom portion of the positive electrode can 3 to the thickness b is preferably 0.4 to 0.8. Although the effective internal volume of the battery can be increased as the plate thickness a of the central portion 12 is smaller, it is not preferable that the ratio is less than 0.4 because the component strength is reduced and the liquid leakage resistance is reduced. On the other hand, if this ratio exceeds 0.8, it is difficult to obtain the desired effects of the present invention.

As shown in FIG. 1, the inner diameter c of the recess 14 is smaller than the inner diameter d of the opening of the insulating gasket 4 by d.
It is preferable that −1.0 mm ≦ c ≦ d + 0.5 mm. As the inner diameter c of the concave portion 14 is larger, an effective air diffusion layer can be secured, and in particular, heavy load characteristics can be improved. However, if the ratio is out of the above range, the liquid leakage resistance is undesirably reduced. The opening of the insulating gasket 4 referred to here is the opening on the side facing the separator 8.

As described above, in the above-described zinc-air battery, the thickness of the portion of the positive electrode can 3 that greatly affects the leakage resistance, such as the swaged sealing portion and the outer peripheral portion 13 at the bottom, is kept large, and the center of the positive electrode can 3 The plate thickness a of the portion is made smaller than the plate thickness b of the outer peripheral portion 13. Therefore, this zinc-air battery can maintain the strength of components, maintain the reliability of liquid leakage resistance, increase the effective internal volume of the battery, and improve the discharge capacity.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below based on experimental results.

First, the thickness a of the central portion 12 of the positive electrode can 3
The ratio of the thickness to the thickness b of the outer peripheral portion 13 was examined.

Embodiment 1 First, as shown in FIGS. 1 and 2, the inner diameter c of the concave portion 14 is 8.0 mm, and the thickness a of the central portion 12 is 0.1 mm.
12 mm, and the thickness b of the outer peripheral portion 13 is 0.20 mm
The positive electrode can 3 is manufactured by pressing a plate material such as steel so that The ratio a / b of the thickness a to the thickness b is
0.6. The air diffusion layer 11 made of a nonwoven fabric is provided in the concave portion 14 inside the central portion 12 of the positive electrode can 3 also serving as the positive electrode terminal.
Is installed. On top of that, a porous polytetrafluoroethylene membrane 6 is punched out to a diameter of 11.0 mm and inserted.

Next, the metal catalyst, the carbon material and the aqueous polytetrafluoroethylene dispersion are sufficiently kneaded. Thereafter, this is applied to a mesh made of nickel, dried and rolled by a press, and a porous film made of polytetrafluoroethylene is pressed on one side to produce an oxygen reduction electrode 7. Then, the oxygen reduction electrode 7 is punched so as to have a diameter of 11.0 mm, and is inserted into the positive electrode can 3 so that the porous film 6 faces the air hole 2.

Subsequently, the separator 8 made of a cellulose film and the electrolyte holding layer 9 made of a non-woven fabric made of a cellulose fiber are punched out to a diameter of 11.0 mm and inserted on the oxygen reduction electrode 7.

Next, as in the case of the positive electrode can 3, nickel-SU
A negative electrode case 1 is prepared by pressing a plate made of a three-layered material of S-copper into a predetermined shape so that the copper surface is on the inside, and the inner diameter d of the opening is 8 in the negative electrode case 1 also serving as a negative electrode terminal. A 0.5 mm insulating gasket 4 is incorporated and integrated. Then, a gelled negative electrode mixture 5 is injected into the integrated body of the negative electrode case 1 and the insulating gasket 4. The gelled negative electrode mixture 5 is a mixture of granular zinc and an aqueous solution of potassium hydroxide aqueous solution with a gelling agent such as carboxymethyl cellulose.

Then, with the opening of the insulating gasket facing the separator 8, the positive electrode can 3 into which the electrolyte holding layer 9 has been inserted is placed over the negative electrode case 1 into which the gel negative electrode mixture 5 has been injected. Negative case 1
Bent mechanically to the side to seal the battery. Finally, a seal 10 is attached to the air hole 2 in the central portion 12 of the positive electrode can 3 to complete the battery.

Examples 2 to 5 The ratio a / b of the thickness a of the positive electrode can 3 to the thickness b of the positive electrode can 3 in Example 1 was set to 0.8, 0.4, 0.3 and 0.2. The positive electrode can 3 was produced by changing each of them. Except for this, a battery was fabricated in the same manner as in Example 1.

Comparative Example 1 As shown in FIG. 3, the plate thickness a of the positive electrode can 3 in Example 1
A battery was fabricated in the same manner as in Example 1, except that the ratio a / b to the plate thickness b was changed to 1.

Battery Characteristics Evaluation The batteries of Examples 1 to 5 and Comparative Example 1 were discharged under a load of 620 Ω, and the discharge capacities were examined. Further, Examples 1 to
The batteries of Example 5 and Comparative Example 1 were subjected to a temperature of 45 ° C. and a relative humidity of 95.
%, And the number of liquid leaks when left for 40 days in an atmosphere was examined. Table 1 shows the results.

[0028]

[Table 1]

From the results shown in Table 1, it can be seen that the batteries of Examples 1 to 5 have improved discharge capacity as compared with the battery of Comparative Example 1. This is because the batteries of the respective embodiments have the central part 1
This is because the effective internal volume of the battery can be increased correspondingly because the plate thickness a of the second is formed thin. Also,
It can be seen that the smaller the ratio a / b of the plate thickness a to the plate thickness b, the higher the discharge capacity. However, when the ratio a / b of the plate thickness a to the plate thickness b is 0.3 or less, the liquid leakage resistance is reduced. This is because when the ratio becomes 0.3 or less, the component strength is reduced. From this, it is understood that the ratio of the plate thickness a to the plate thickness b is preferably 0.4 to 0.8, and within this range, the discharge capacity is improved and the liquid leakage resistance is excellent.

Next, the ratio of the inner diameter c of the concave portion 14 of the positive electrode can 3 to the inner diameter d of the opening of the insulating gasket 4 was examined.

Examples 6 to 14 As shown in Table 2, the inner diameter c of the concave portion 14 of the positive electrode can 3 in the first embodiment was smaller than the inner diameter d of the opening of the insulating gasket 4 by d−2.0 mm ≦ The cathode can 3 was manufactured by changing each such that c ≦ d + 2.0 mm. Except for this, the battery was fabricated in the same manner as in Example 1.

Evaluation of Battery Characteristics The batteries of Examples 6 to 14 were discharged under a load of 100Ω, and the discharge capacities were examined. Examples 6 to 1
The number of leaks when the battery of No. 4 was left for 40 days in an atmosphere at a temperature of 45 ° C. and a relative humidity of 95% was examined. The results are also shown in Table 2.

[0033]

[Table 2]

From the results shown in Table 2, it is understood that the larger the inner diameter c of the concave portion 14 of the positive electrode can 3 is, the more excellent the discharge capacity is, and it is particularly advantageous for the heavy load characteristics. This is because the larger the inner diameter c of the concave portion 14 can secure an effective volume of the air diffusion layer 11. However, when the inner diameter c of the concave portion 14 is larger than the inner diameter d of the insulating gasket 4 by 1.0 mm or more, the leakage resistance is significantly reduced. From this, the inner diameter c of the central portion 12
And the inner diameter d of the insulating gasket 4 is d−2.0.
mm ≦ c ≦ d + 2.0 mm is preferable, and d−1.0 mm
≦ c ≦ d + 0.5 mm is more preferable. It can be seen that in this range, the discharge capacity is improved and the liquid leakage resistance is also excellent.

[0035]

As is clear from the above description, in the zinc-air battery according to the present invention, the plate thickness of the portion effective for liquid leakage resistance is kept as it is, and the plate thickness of at least a part of the positive electrode can is changed to another plate thickness. Since it is thinner than the plate thickness of the part, it is possible to maintain the strength of the parts, maintain the reliability of the liquid leakage resistance, and increase the effective internal volume of the battery to improve the discharge capacity.

[Brief description of the drawings]

FIG. 1 is a sectional view of a zinc-air battery to which the present invention is applied.

FIG. 2 is a sectional view of a positive electrode can of the zinc-air battery.

FIG. 3 is a cross-sectional view of a positive electrode can of a conventional zinc-air battery.

[Explanation of symbols]

1 negative electrode case, 2 air holes, 3 positive electrode can, 4 insulating gasket, 5 negative electrode mixture, 6 porous membrane, 7 electrodes, 8
Separator, 9 electrolyte holding layer, 10 seals, 1
1, air diffusion layer, 12 central part, 13 outer peripheral part, 1
4 recess

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Noriyuki Yamaguchi, Inventor 1-1-1 Shimosugishita, Takakura, Hiwada-cho, Koriyama-shi, Fukushima Prefecture Sony Energy Tech Co., Ltd.

Claims (3)

[Claims] 1. A negative electrode case filled with a negative electrode active material and a positive electrode can having an air hole are integrated via an insulating gasket, and the thickness a of at least a part of the bottom of the positive electrode can is changed to another part. An air-zinc battery characterized in that the air-diffusion layer is disposed in a concave portion formed by making the thickness smaller than the plate thickness b. 2. The ratio a / b of the thickness a to the thickness b is 0.
The zinc-air battery according to claim 1, wherein the ratio is 4 to 0.8. 3. The inner diameter c of the recess is d−1.0 mm ≦ c ≦ d + 0.5 mm with respect to the inner diameter d of the opening of the insulating gasket.
The zinc-air battery according to claim 1, wherein: