JPH03108257A - Battery - Google Patents

Abstract

PURPOSE:To increase the storage performance and discharge performance of a battery by placing a piece of aramid paper between the air intake side of a gas diffusion electrode and the inner surface of a battery container. CONSTITUTION:A piece of aramid paper 11 is placed between a gas diffusion electrode 1 using oxygen as the active material and a battery container 8 having an air intake hole 3. The aramid paper 11 consists of aromatic polyamide and glass fibers or carbon fibers. A microporous film such as polytetrafluoroethylene may be placed between the aramid paper 11 and the gas diffusion electrode 1. An air diffusion porous member such as a nonwoven fabric may be placed between the aramid paper 11 and the battery container 8. Oxygen in the air is selectively permeated into a battery at a good permeable rate, and the penetration of water vapor and carbon dioxide is blocked.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a gas diffusion electrode using oxygen as an active material, an electrolytic solution consisting of an alkaline aqueous solution, and a metal such as zinc, magnesium, aluminum, etc. Name Battery 2, Claims (1) A gas diffusion electrode containing oxygen as an active material, and a battery container having an air intake hole communicating with outside air, wherein the air intake side of the gas diffusion electrode and the inner surface of the battery container are connected to each other. A battery with aramid paper made of aromatic polyamide interposed in between.

(2) The battery according to claim 1, wherein the aramid paper is made of aromatic polyamide and glass fiber.

(3) The battery according to claim 1, wherein the aramid paper is made of aromatic polyamide and carbon fiber.

(4) @ Before the aramid paper has air intake holes 3
The battery according to any one of claims 1, 2, and 3, wherein the inner surface of the battery container is in direct contact with the gas diffusion electrode.

(@ This relates to a battery that includes a negative electrode active material such as nonwoven alcohol, hydrazine, or hydrogen between the aramid paper and the battery container.

BACKGROUND OF THE INVENTION BACKGROUND ART Batteries equipped with gas diffusion electrodes and using oxygen as an active material include air cells, fuel cells, and the like. Especially alkaline aqueous solution,
In batteries that use a neutral salt aqueous solution as the electrolyte,
Water vapor flows in and out from the gas diffusion electrode (oxygen electrode) depending on the internal vapor pressure, causing changes in the concentration and volume of the electrolyte in the battery, which affects various characteristics of the battery. Taking a button-type air battery as an example, the situation will be explained using FIG. 2. In the figure, 1 is an oxygen electrode (air electrode), and 2 is a porous clear water membrane that supports the oxygen electrode 1, which is made of polytetrafluoroethylene (PTFK), which has gas diffusivity but blocks liquid. 3 is an air intake hole from the outside, 4 is a porous body that diffuses air, 6 is a separator, 7 is a negative electrode zinc,
Potassium hydroxide aqueous solution is used as the alkaline electrolyte impregnated and held in these, and its concentration is 30 to 36% by weight. For this reason, when the relative humidity is higher than 47 to 59%, external moisture is taken in, resulting in a decrease in electrolyte concentration and volumetric expansion, resulting in a decrease in discharge performance and leakage of the electrolyte.

On the other hand, when the relative humidity is below the above range, evaporation of the electrolytic solution occurs, resulting in an increase in internal resistance and a decrease in discharge performance. Therefore, since they are easily affected by the environmental atmosphere, problems arise with battery characteristics after long-term storage.This restricts the use of air cells and fuel cells in specific fields, and poses a major challenge in making them more versatile. It had In addition, in the figure, 8 is a negative electrode container containing the negative electrode zinc 7, 9 is an insulating gas scaler), 10
is the positive electrode container.

Problems to be Solved by the Invention Various proposals have been made in the past in order to improve these problems. For example, a substance that reacts with the electrolyte is inserted into a portion around the air hole to prevent the electrolyte from leaking to the outside of the battery. Alternatively, an electrolyte absorbing material such as a nonwoven fabric made of paper or a polymeric material is provided to prevent leakage of the electrolyte to the outside of the battery. Furthermore, proposals have been made to prevent water vapor and carbon dioxide from entering the inside of the battery, even by making the air holes extremely small to limit the amount of oxygen supplied. However, both methods had major problems in preventing liquid leakage and discharge performance, especially in long-term discharge performance. The main causes of this are dilution and volumetric expansion of the alkaline electrolyte due to the entry of water vapor in the air into the battery, and obstruction of discharge resistance due to the formation of carbonates due to the entry of carbon dioxide gas and blockage of the air circulation path. However, when the outside air has low humidity, the loss of moisture in the electrolyte can cause a decline in performance. In order to eliminate this cause, in recent years, methods have been developed to control the amount of permeation of water vapor and carbon dioxide gas, and to supply air to the oxygen plate through a membrane that selectively allows oxygen to pass through, for example, using organopolysiloxane-based membranes. A method has been proposed that uses a film in which a uniformly porous thin film, a thin film of a metal oxide, or an organic compound containing a metal element is integrated with a suitable porous film.

However, to date, it has not been put to practical use because it has not been possible to obtain sufficiently effective oxygen selective permeability, and therefore it has not been possible to obtain satisfactory discharge performance, and it has not been possible to withstand long-term use or storage as a battery. There was a technical issue.

Therefore, the present invention aims to improve the storability and long-term use performance of the above-mentioned battery, as well as to selectively remove oxygen from the atmosphere in order to obtain satisfactory discharge performance under a wide range of discharge conditions from light loads to heavy loads. The purpose of this invention is to provide an effective means to introduce water vapor into the battery at a high speed and prevent water vapor from entering and exiting the battery, and carbon dioxide from the atmosphere from entering the battery for a long period of time.

Means for Solving the Problems In order to achieve the above objects, the present invention provides an air intake system for a gas diffusion electrode of a battery comprising a gas diffusion electrode using oxygen as an active material and a battery container having an air intake hole communicating with outside air. Aramid paper made of aromatic polyamide is interposed between the side and the inner surface of the battery container.

The present invention focuses on the high oxygen selective permeability of aramid paper.

This membrane has the oxygen permeation rate necessary to obtain satisfactory discharge performance under heavy loads, and the permeation blocking ability for water vapor and carbon dioxide to withstand long-term storage and long-term discharge under low humidity or high humidity atmospheres. They discovered that the performance of batteries using this membrane was extremely excellent, and they completed it.

Function: As is clear from the results of the battery test in the Examples described later, the composite membrane with this configuration has a good oxygen permeation rate for batteries and blocks water vapor and carbon dioxide from entering the battery. Both the heavy load discharge performance required of a practical battery and the performance when discharged for a long time in an atmosphere of high humidity or low humidity can be maintained in a satisfactory state.

Examples (Example 1) Aramid paper made of aromatic polyamide and having a thickness of 60 μm was used as an oxygen-selective permeable membrane.

(Example 2) Aramid paper made of aromatic polyamide and glass fiber with a thickness of 180 μm was used as an oxygen-selective permeable membrane.

(Example 3) Aramid paper made of aromatic polyamide and carbon fiber with a thickness of 150 μm was used as an oxygen-selective permeable membrane.

(Comparative Example 1) As an oxygen-selective permeable membrane, an oxygen-enriching membrane was used in which a polydimethylsiloxane membrane was formed to a thickness of 60 μm on a reinforcing polyglopylene nonwoven fabric.

(Comparative Example 2) A porous water-repellent membrane is used, but an oxygen-selective permeable membrane is not used.

In order to fully confirm the effects of the present invention, we prototyped and evaluated batteries using the aramid papers of Examples 1 to 3 and the composite membrane of Comparative Example 1, and batteries that did not use the oxygen-selective permeable membrane. . First, in the case of Comparative Example 2 in which no oxygen selective permeable membrane was used, the configuration was exactly the same as that in FIG. 2. Next, in a battery using an oxygen selective permeable membrane, as shown in Fig. 1, each composite membrane is placed between a porous PTFE membrane 2 and a porous body 4 that disperses and equalizes the flow of oxygen. This is an intervening configuration.

All of the prototype batteries had a diameter of 11.6 mm and a total height of 64 ffllll, and were able to withstand 2.5 ft under a relatively heavy load (76 Ω).
00, the sufficiency of the oxygen uptake rate in the air into the battery was evaluated by continuous discharge at normal humidity (60ΦRH), and relatively; 20C1 high humidity r5 (so%RH) at heavy load (3Ω).
, and continuous discharge at low humidity (20% RH) for a long period of time will cause problems such as the intake of water vapor from the atmosphere into the battery, the evaporation of moisture within the battery, and the intake of carbon dioxide gas during the long-term discharge period. The impact on performance was evaluated.

The details of the prototype battery are shown in Table 1.

Here, in Comparative Example 1, the gas permeation rate ratio of oxygen and oxygen was 1
As described above, the gas permeation rate ratio between oxygen and water vapor is less than 1, and it cannot be said that the membrane has a selective oxygen permeability rate as a membrane for batteries. However, in the examples, it is 3 or more, which shows that the aramid paper of the present invention has excellent oxygen selective permeability.

Table 2 also shows the performance test results of the prototype battery.

In Table 2, the end-of-discharge voltage is 0.9 V in all cases, and the change in weight indicates the increase/decrease before and after the discharge test, and is a numerical value that mainly suggests the amount of moisture taken in or evaporated during discharge.

The present invention can be most clearly explained in detail by comparing the characteristics of these batteries with Comparative Example 2, which does not use a composite membrane.

First, in the heavy load test at 20C1 normal humidity, the discharge time was short;
Since the effects of moisture uptake, evaporation, and carbon dioxide gas are small, there is no need to consider blocking the permeation of moisture and carbon dioxide gas as long as the oxygen supply rate is sufficient for battery performance.

Therefore, under such conditions, excellent characteristics can be obtained even in Comparative Example 2.

On the other hand, in Examples 1 to 3 described above, the same discharge characteristics as Comparative Example 2 were obtained, and the rate at which oxygen permeated through the composite membrane sufficiently followed the rate at which oxygen was consumed in the discharge reaction. It shows that there is. However, it can be seen that Comparative Example 1 is completely insufficient in oxygen permeation rate.

On the other hand, in the case of light load discharge, the discharge time is long, and in addition, when the outside air is high or low humidity, it is necessary to obtain battery characteristics that are superior in preventing the permeation of moisture and carbon dioxide gas, especially moisture, rather than the oxygen supply rate. It is important to note that the battery of Comparative Example 2, which does not have a mechanism to prevent the permeation of moisture and carbon dioxide gas, suffers from depletion and discharge due to depletion of moisture or, conversely, blockage of the air holes due to leakage due to excessive intake of moisture. The voltage drops halfway through, and a capacity equivalent to only a portion of the discharge capacity obtained in the heavy load test is obtained. Furthermore, it goes without saying that liquid leakage during discharge is a fatal problem in practical terms. On the other hand, Examples 1 to 3 showed extremely excellent performance, and in these cases, a capacity almost equal to the discharge capacity in the heavy load test was obtained. These trends are the same whether the test atmosphere is high humidity or low humidity.

This indicates that in Examples 1 to 3, the moisture permeation blocking effect of the aramid paper was sufficiently exhibited.

Taking all the above into account, it can be concluded that a battery using aramid paper has excellent heavy load characteristics and light load characteristics, and can provide an excellent battery that is stable even under changes in the external atmosphere.

In addition, in the above example, the aramid paper of the present invention was installed between the battery container and the porous body for air diffusion, but if the aramid paper of the present invention has sufficient mechanical strength, There is no difference in battery characteristics even if the porous material is removed. Furthermore, in the above examples, the aramid paper of the present invention was placed between the oxygen electrode and the porous membrane that supported the oxygen electrode, but if the oxygen electrode had sufficient strength, the porous membrane could be omitted. Even in that case, the battery characteristics remain unchanged. We also confirmed that an air battery using an aqueous solution of neutral salts such as ammonium chloride or zinc chloride as the electrolyte has the same effect as the battery using an alkaline electrolyte shown in the example. ing.

Effects of the Invention As is clear from the above explanation, the aramid paper of the present invention has excellent practical performance and excellent performance in a wide range from heavy loads to light loads of batteries that use a neutral or alkaline aqueous solution as the electrolyte. It has the advantage of being able to provide leakage resistance and long-term storage.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a button-type zinc-air battery used in the study of Examples 1 to 3 of the present invention and Comparative Example 1, and Figure 2 is a conventional button-type zinc-air battery that does not use an oxygen-selective permeable membrane. It is a sectional view of a battery. 1... Oxygen electrode (air electrode), 2... Water repellent film, 3... Air intake hole, 4... Porous body,
5.6... Separator, 7... Fish cage zinc, 8... Fish cage container, 9... Insulating gasket, 1o... Positive electrode container, 11...Oxygen selective permeable membrane.

Claims (1)

[Scope of Claims] (1) A battery container having a gas diffusion electrode containing oxygen as an active material and an air intake hole communicating with the outside air, and between the air intake side of the gas diffusion electrode and the inner surface of the battery container. , a battery interposed with aramid paper made of aromatic polyamide. (2) The battery according to claim 1, wherein the aramid paper is made of aromatic polyamide and glass fiber. (3) The battery according to claim 1, wherein the aramid paper is made of aromatic polyamide and carbon fiber. (4) The battery according to any one of claims 1, 2, or 3, wherein the aramid paper is in direct contact with the inner surface of the battery container having an air intake hole and the gas diffusion electrode. . (5) The battery according to any one of claims 1, 2, and 3, wherein an air diffusion porous material such as a nonwoven fabric is interposed between the aramid paper and the battery container. (6) Claims 1 and 2 include a microporous membrane made of polytetrafluoroethylene (PTFE) film and supporting an oxygen electrode interposed between the aramid paper and the gas diffusion electrode. or the battery according to any of paragraph 3. (7) An air diffusion porous material such as a nonwoven fabric is interposed between the aramid paper and the battery container, and a film such as polytetrafluoroethylene is interposed between the oxygen selectively permeable composite membrane and the gas diffusion electrode. Claim 1, comprising: a microporous membrane supporting the gas diffusion electrode;
The battery according to any one of paragraphs 2 and 3.