JPS6261275A - Air cell - Google Patents

Abstract

PURPOSE:To produce an air cell with sufficient discharge capacity by using an air electrode having a three-layered structure and specifying the total air transmittance of the air cell. CONSTITUTION:An air electrode 14 has a three-layered structure which consists of a water-repellent layer 14a, a catalyst layer 14b and a current-collecting layer 14c. During assembly of the air cell of this invention, the water-repellent layer 14a is installed facing the air diffusion layer. The total air transmittance of the air electrode 14 consisting of three layers is adjusted to 1,000-1,500,000sec/100cc.in<2>. When the above total air transmittance is less than the lower limit, an electrolyte is liable to be diluted or evaporated to dryness in the air cell 14 because the air electrode 14 transmits oxygen gas and a great amount of steam in the air although increased discharge capacity is achieved. In contrast, when the above total air transmittance exceeds the upper limit, only insufficient oxygen gas is incorporated for achieving the oxygen gas reduction point of the catalyst layer although steam is prevented from flowing into the cell and its liquid leakage resistance is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to an air battery with excellent electrolyte leakage resistance.

[Technical backbone of the invention and its problems] Various structures are known for air batteries that use oxygen in the air as a polar active material, but a typical one is a button-shaped structure. Furthermore, since lead is currently widely used as the negative electrode active material, a button-type zinc-air battery will be described below.

A conventional button-type zinc-air battery generally has a structure as shown in FIG. That is, in the figure, the bottom part of the 11-day electrode case 1 has air holes 2 formed at the bottom, an air diffusion layer 3, and an air electrode 4 consisting of a porous catalyst layer having an ability to reduce oxygen gas and a current collector layer. , and a separator 5 made of, for example, a nonwoven fabric made of polypropylene are stacked and housed in this order. On the other hand, the cap 7, which also serves as a negative electrode terminal, is fitted into the opening of the positive electrode case 1 via the gasket 6, and the periphery of the opening of the I1 electrode case 1 is bent inward to seal the entire battery. There is.

A space defined by the positive electrode case 1 and the cap 7 is filled with a negative electrode mixture 8.

As this negative electrode mixture, a mixture of salivary lead powder, an alkaline electrolyte such as a KOH aqueous solution, and an alkali-resistant gelling agent is generally used.

In such a button-type zinc-air battery, oxygen gas in the air is introduced into the air diffusion layer 3 through the two air holes 2, and then is activated (ionized) by contacting the air electrode 4. It will be done.

In such conventional button-type air lead-acid batteries, for example, a porous molded body of activated carbon is generally used as the air electrode 4. However, in a button-type zinc-air battery with such a structure, the air electrode 4 allows water vapor that is inevitably introduced into the battery to pass along with oxygen in the air, and as a result, the negative electrode The water vapor reaching the mixture 8 causes the electrolyte to swell and increase. As a result, during long-term use or storage of the battery, the electrolyte in the negative electrode mixture 8 leaks from the battery, resulting in contamination of the equipment or deterioration of the functionality of the equipment. Furthermore, on the contrary, as the moisture in the electrolyte inside the battery is completely dissipated to the outside of the air, the electrolyte dries and solidifies, causing problems such as deterioration of battery characteristics. There's a problem.

Therefore, recently, a structure has been proposed in which a water-repellent film, such as a porous thin film made of Funto resin, is pressed onto the surface of the air electrode 4 facing the air diffusion layer 3, that is, the lower surface in the figure. It is in practical use in alkaline/air batteries. However, although such a thin film is effective in preventing electrolyte leakage, it is not sufficient to prevent moisture (water vapor) from entering the air. Therefore, the problems described above still exist.

[Object 1 of the Invention] The present invention solves the above-mentioned conventional problems, and effectively prevents water vapor from entering the battery or dissipating water from the electrolyte. As a result, changes in the concentration of the electrolyte are prevented. Another object of the present invention is to provide an air battery in which electrolyte leakage does not occur and the discharge cell 1 changes little during long-term discharge.

[Summary of the Invention] In order to solve the above-mentioned [Objective 1], as a result of intensive studies focusing on the structure of the air electrode, the present inventors first developed an air electrode with a water-repellent layer, a catalyst layer, and a current collector. Furthermore, by limiting the air permeability of the air electrode of this three-layer structure to a predetermined range described below, we confirmed the effect and made this report. He has completed his invention.

That is, the air battery of the present invention includes at least a water-repellent layer,
An air battery comprising an air electrode having a structure in which a catalyst layer and a current collector layer are laminated, and the total air permeability of the air electrode is within the Gurley number range of 1,000 to 1,5.
00,000sec/1oocc@in2.

As described above, the air battery of the present invention is characterized by the limited structure of the air electrode and its physical properties, and there are no limitations on other components.

The air electrode of the air battery of the present invention will be explained in detail below.

Figure 1 shows a three-layer structure as an example, with an air electrode 1
4 is a water-repellent 11 layer 14d, a catalyst layer +4b, and a current collector layer! It has a 3-layer structure in which 4c is laminated and integrated. When assembling the battery, the battery is housed with the water-repellent layer 14a facing the air diffusion layer.

Suitable materials for the water-repellent layer include thin films such as porous polytetrafluoroethylene (PTFE), porous polyethylene, and porous polypropylene.
The catalyst layer is preferably one in which a catalyst capable of reducing oxygen, such as platinum, palladium, silver, or manganese oxide, is supported on, for example, activated carbon. Suitable materials for the current collector layer include porous solid bodies such as Ni cement, Ni expanded metal, N]bunched metal, and Ni-plated steel wire mesh.

This three-layer air electrode is constructed by laminating the base layers described in I-1 and then pressurizing the entire structure to bring the valley layers into pressure contact, or by interposing an adhesive layer made of, for example, fluorine resin powder between each layer. By pressurizing the entire body, it is manufactured as a body structure.

The total air permeability of the thus obtained three-layer integrated air electrode is 1.000 to 1 in terms of Curley number.
There is peace of mind that it is specified at 500,000sec/1ooccs in2. Gurley number is 1,000sec/IQO
When cca in2 is less than 2, that is, when the air permeability is larger than the range of the present invention, the discharge capacity, which is one of the characteristics of the air electrode itself, becomes large;

Since water vapor in the air is allowed to permeate through the oxygen gas, it is easy for the electrolyte to swell or dry up as described above inside the battery, and as a result, the performance of the battery fluctuates widely. This may cause inconveniences such as leakage of the electrolyte to the outside, or inhibition of the power generation function of the entire battery.

Also, conversely, the Gurley number is 1,500,000sec/1
When the air permeability exceeds 00cc・1n2f, that is, when the air permeability is smaller than the range of the present invention, the inflow of water vapor into the battery is prevented, the battery performance is stabilized, and the leakage resistance P1 is also improved. However, on the other hand, it is not preferable because sufficient oxygen gas cannot be taken in until it reaches the oxygen scum reduction action point in the catalyst layer, making it impossible to obtain sufficient flow resistance to drive applied equipment such as hearing aids.

In order for the air electrode of the present invention to have a Gurley number in the range I, first, each layer constituting the air electrode,
In particular, the air permeability of the wood-repellent bamboo layer and the catalyst layer, which are the lower layers, is controlled, and secondly, the BuJ method for crimping or adhering each layer is appropriately selected. What is necessary is just to select a pressure etc. suitably.

Note that among the constituent layers of the air electrode, if the pore diameter of the water-repellent Ni layer, such as a porous PTFE layer, is too large, -1
Even if the other conditions mentioned above are controlled, it is difficult to keep the air permeability (Gurley number) of the air electrode as a whole within the range described above, and the electrolyte inside the battery is also likely to leak. This is not desirable. Considering these points, the maximum pore diameter of the wood-repellent bamboo layer should be set to 0.3 or less, or even 0.3 or less.
It is preferable to set the number to two or less. Also, the porosity is 9
5% or more.

It is preferably set to 60% or more, more preferably 50% or less.

In addition, the layer structure of the air electrode in the present invention is 1-3 mentioned above.
Not limited to those with a layered structure, for example, those with a catalyst layer and quadruple layer in the wrong order, or those with water repellency +11
4 in which layers - catalyst layer - current collector layer - catalyst layer are stacked in this order.
A layered structure is also effective.

[Embodiments of the Invention] Hereinafter, embodiments of the present invention will be described with respect to a button-type zinc-air battery.

Porous P with maximum pore diameter of 0.15 pm and thickness of 200 μm
TFE membrane.

A catalyst layer with a thickness of 400 μm and a porous aggregate layer made of Ni elements are laminated in this order, and an appropriate pressure (usually 50~look/cm) is applied to the whole.
An air electrode made of one layer of 4% S was fabricated. The catalyst layer used was one obtained by kneading yIi (active) R with an average particle diameter of 8 μm and a PTFE binder. This air'11
The air permeability of the f-pole 1-tal is 7,000 sec/1oocce in2 and 20,00 in Gurley number, respectively.
0sec/100Octin2 and 1,000,00
There was 0sec/100cc* in2.

In this way, #\I leaked air electrode is shown in Fig. 2 button-shaped air [11! Air electrode 4 and sepa E of lead battery
/- By storing it instead of 5, the row diameter is 11, 5m.
An air battery with a height of 5.4 mm and a height of 5.4 mm was manufactured by lOO4P4 (7).In addition, in this button type zinc-air battery,
As the negative electrode mixture 8, a mixture of lll1 lead powder, He'Y+l aqueous solution, and carboxymethyl cellulose was used.

Such a button type air zinc 'i1! The ponds were divided into two groups of 50 ponds each, and the following evaluation tests were conducted for each group.

(1) Discharge capacity fi at heavy temperature 25°C1 external load 620Ω
l was measured and the average value was determined.

(2) Leakage resistance special feature 1 The number of batteries that leaked when stored in an atmosphere at a temperature of 45° C. and a relative humidity of 90% for 711 days was investigated.

The ten results are summarized in the table.

For comparison, the Gurley number of 1-tal of the air electrode was set to 850 sec/100 cce 1n2 (Comparative Example 1) and 3,000,000 sec/100 c
A button-type zinc-air battery was manufactured in the same manner as in Example 5, except that the value was 112 (comparative example 2), and the same evaluation test was conducted. .

In this example, a button-type zinc-air battery was explained using a side plate, but the effect is not limited to this, and exactly the same effect can be obtained with other shapes of zinc-air batteries such as square and cylindrical shapes. It goes without saying that it will be rejected. Furthermore, similar effects can be obtained not only for air batteries based on air/zinc, but also for other types of air batteries such as air/aluminum and air/iron.

[Effects of the Invention] As is clear from the explanation in 1 below, the air battery of the present invention has, firstly, an air electrode having a three-layer structure, and secondly, the air 'ir' and the poles 1 and -. Since the air-permeable gourd of the barrel is limited to the range number r mentioned above, sufficient h
In other words, it is sufficient to drive the equipment (not only can the flow be taken out, but also has excellent leakage resistance).
1, and its commercial value is extremely large.

[Brief explanation of the drawing]

Figure 1 shows 3 cells used in an air battery according to an embodiment of the present invention.
FIG. 2 is a longitudinal cross-sectional view showing the structure of a conventional button-type zinc-air flowproof structure. 4.14...Air electrode, +4a...Water repellent layer, 14b...Catalyst layer, 14c...
...Current collector layer.

Claims (1)

[Claims] 1. An air battery comprising an air electrode having a structure in which at least a water repellent layer, a catalyst layer, and a current collector layer are laminated, and the total air permeability of the air electrode is , 1,000 to 1,500,000sec/100c in Gurley number
An air battery characterized by being c.in^2. 2. The air battery according to claim 1, wherein the air electrode has a total air permeability of 5,000 to 1,200,000 in Gurley number. 3. The air battery according to claim 1 or 2, wherein the water-repellent layer has a maximum pore diameter of 0.3 μm or less.