JPH0417259A - Battery - Google Patents

Abstract

PURPOSE:To obtain excellent practicability and long-term storage property in a wide range from a heavy load to a light load by interposing compound material, which is obtained by forming a perovskite type compound oxide thin film on the surface of the porous material having fine holes of which hole diameter is less than 0.1mum, between the air intake side of a gas diffusion electrode and the inner surface of a battery container. CONSTITUTION:In a battery comprising a gas diffusion electrode 1, in which oxygen is used as the active material, and a battery container having an air intake hole 3 communicated with the outside air, a perovskite type compound oxide thin film 11 at a thickness of 0.01-1.0mum, which is formed on a fine porous base material 4 having hole diameters less than 0.1mum, is interposed between the air intake side of the gas diffusion electrode 1 and the inner surface of the battery container. This compound material made of the perovskite type compound oxide thin film 11 has oxygen penetrability required for obtaining the sufficient discharge characteristic under the heavy load condition and transmission stopping power against steam and carbon dioxide for enduring long-term hot insulation and long-term discharge under the lower moisture or high moisture condition. Storage property of a battery, in which alkali aqueous solution and neutral salt aqueous solution are used as electrolyte, and performance in a long-term usage are thereby improved, and sufficient discharge performance under the wide discharge condition from light load to heavy load can be obtained.

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, or aluminum, or alcohol, hydrazine, or hydrogen. The present invention relates to a water vapor and carbon dioxide selective barrier composite material that is effective in manufacturing batteries with negative electrode active materials such as .

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 affected the battery's performance characteristics.

Taking a button-type air battery as an example, the situation will be explained using FIG. 2. In the figure, ■ is an oxygen electrode (air electrode), and 2 is a porous water-repellent membrane that supports the oxygen electrode 1 and is made of polytetrafluoroethylene (PTFE), which has gas diffusivity but blocks liquid permeation. 3 is an air intake hole from the outside, 4 is a porous body for air diffusion, 5 and 6 are separators, 7 is a negative electrode zinc, and the alkaline electrolyte impregnated and held in these is a potassium hydroxide aqueous solution, Its concentration is 30-35
It is expressed as 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 the figure, 8 is a negative electrode container containing the negative electrode zinc 7, 9 is an insulating gasket, and 10 is a 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 these are the dilution and volumetric expansion of the alkaline electrolyte due to the entry of water vapor from the air into the battery, and the formation of carbonates due to the entry of carbon dioxide (due to inhibition of the discharge reaction and blockage of the air flow path). Conversely, when the outside air is low humidity, the loss of moisture in the electrolyte causes a decline in performance.In order to eliminate this cause, in recent years, efforts have been made to control the amount of water vapor and carbon dioxide that permeate. ,
A method of supplying air to the oxygen electrode through a membrane that selectively allows oxygen to permeate, such as a polydimethylsiloxane-based homogeneous porous thin film, a metal oxide, or an organic compound containing a metal element. A method using a membrane that integrates a thin film and a suitable porous membrane has been proposed.

However, to date, it has not been possible to obtain a material that has both sufficiently effective water vapor and carbon dioxide blocking ability as well as oxygen permeability, so it cannot withstand long-term use or storage as a battery, so it has not been put into practical use. It wasn't.

Therefore, the present invention improves the storability and long-term use performance of the above-mentioned battery, and also aims to remove atmospheric oxygen from the battery at a sufficient rate 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 for preventing water vapor from entering and exiting the battery and carbon dioxide from the atmosphere from entering the battery over 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. A perovskite composite oxide thin film with a thickness of 0.01 to 1.0 μm is interposed between the side and the inner surface of the battery container on a microporous base material with a pore size of 0.1 μm or less.

The present invention is based on the discovery of the large water vapor and carbon dioxide selective blocking ability of a composite material made of a perovskite type composite oxide thin film.

Furthermore, this composite material has the oxygen permeability necessary to obtain satisfactory discharge performance under heavy loads, and the water vapor and carbon dioxide permeability sufficient to withstand long-term storage and long-term discharge under low humidity or high humidity atmospheres. They found that the performance of batteries using this composite material is extremely excellent, and they have completed it.

Function: As is clear from the results of the battery test in the Examples described below, the composite material with this structure has a good oxygen permeation rate for batteries and blocks water vapor and carbon dioxide from entering the battery. Keep the effects of
This satisfies both the heavy load discharge performance required of a practical battery and the performance when discharging for a long time in an atmosphere of high or low humidity.

Examples Examples 1 to 12 Various perovskite composite oxide thin films with a thickness of 0.3 μm shown in Table 1 were coated on one side of a porous polycarbonate film (6 μm thick) in which micropores with an average pore diameter of 0.015 μm were uniformly distributed. Made using a composite material made using the sputtering method.

Examples 13-24 Average pore size 0. After polishing porous glass (manufactured by Corning) with uniformly distributed micropores of OO4μm to adjust the plate thickness, a 0.3μm thick perovskite composite oxide thin film of various types was fabricated on one side by sputtering. made of composite material.

Comparative Example 1 A composite material in which polydimethylsiloxane and nonwoven fabric were integrated was used.

Comparative Example 2 A fluororesin-based FEP film with a temperature of 25 μm was used.

Comparative example 3 Exactly the same as the conventional model, using only a water-repellent porous membrane.

In order to confirm the effects of the present invention, composite materials made of perovskite type composite oxides of Examples 1 to 24 and Comparative Example 1,
The gas permeation rate of the membrane of No. 2 was evaluated, and furthermore, using these and Comparative Example 3, a battery was prototyped and evaluated.

First, in the case of Comparative Example 3 in which the composite material was not used, the structure was exactly the same as that in FIG. 2. Next, as shown in FIG. 1, the batteries of Examples 1 to 24 and Comparative Example 1.2 include a porous membrane 2 of PTFE and a porous body 4 that disperses and homogenizes the flow of oxygen.
It has a structure in which each composite material is interposed between the two.

The dimensions of the prototype batteries were 11.6 mm in diameter.

It has a total height of 5.4++w, and the sufficiency of the oxygen uptake rate in the air into the battery was evaluated by continuous discharge at 20℃ and normal humidity (60% RH) under a relatively heavy load (620Ω). 20℃, high humidity (90% RH) with light load (3 to Ω)
, and long-term continuous discharge at low humidity (20% RH), the battery performance may be affected by the incorporation of water vapor from the atmosphere into the battery, evaporation of moisture within the battery, and incorporation of carbon dioxide during the long-term discharge period. The degree of influence was evaluated. The details of the composite materials or membranes used in the battery prototype are shown in Table 1.

Here, in Comparative Example 1, the gas permeation rate ratio of oxygen and nitrogen is
Although the oxygen-enriched membrane exhibits a gas permeation rate ratio of 1 or more, the gas permeation rate ratio of oxygen to water vapor is 1 or less and does not have water vapor selective barrier properties.

Furthermore, although Comparative Example 2 is a non-porous membrane with low moisture permeability, it also has low oxygen permeability and cannot be said to have selective barrier properties.

However, in the examples, the water vapor barrier properties were good (and the oxygen permeability was high), so it can be seen that the composite material made of the perovskite-type composite oxide of the present invention has excellent water vapor selective barrier properties. .

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

(Margin below) In Table 2, the end-of-discharge voltage is 0.9V in each case, and the weight change indicates an increase or decrease before and after the discharge test, which mainly suggests the amount of moisture taken in or evaporated during discharge. This is the numerical value.

The present invention can be most clearly explained in detail by comparing the characteristics of these batteries with Comparative Lightweights 1 to 3, which do not use the composite material according to the present invention.

First, in a heavy load test at 20℃ and normal humidity, the discharge time was short.
Since the influence of moisture uptake and evaporation and the influence of carbon dioxide are small, there is no need to consider blocking the permeation of moisture and carbon dioxide 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 3. On the other hand, in all the above-mentioned embodiments,
Discharge characteristics equivalent to those of Comparative Example 3 were obtained, indicating that the rate at which oxygen permeates through the composite material sufficiently follows the rate at which oxygen is consumed in the discharge reaction. However, it can be seen that Comparative Example 2 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 better in preventing the permeation of moisture and carbon dioxide, especially moisture, than in the oxygen supply rate. The battery of Comparative Example 1.3, which does not have a mechanism to prevent moisture and carbon dioxide from permeating, suffers from depletion of moisture,
Alternatively, the voltage may drop during discharge due to blockage of the air holes due to leakage due to excessive intake of water, resulting in a capacity equivalent to only a portion of the discharge capacity obtained in the heavy load test. . Furthermore, it goes without saying that liquid leakage during discharge is a fatal problem in practical terms. On the other hand, the Examples showed extremely excellent performance, and 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 shows that in all of the examples, the water vapor selective barrier effect of the composite material made of the perovskite type composite oxide thin film is fully exhibited.

In addition, exactly the same effect was confirmed for carbon dioxide.

Taking all the above into consideration, composite materials made of perovskite-type composite oxide thin films have excellent water vapor and carbon dioxide selective barrier properties, and when used, they have excellent heavy load characteristics and light load characteristics, and are resistant to changes in the external atmosphere. It can be concluded that a stable and excellent battery can be provided.

However, if the thickness of the perovskite-type composite oxide thin film is less than 0.01 μm, the pores of the porous base material will not be completely filled, and barrier properties against water vapor and the like will not be exhibited. Further, if the film thickness is 1 μm or more, the film is likely to crack, the pores will not be filled, and the barrier properties will be poor. Therefore, the film thickness is preferably 0.01 to 1 μm.

Furthermore, the selectivity is further improved when the film is formed on porous glass mainly composed of SiO2.

This effect was also confirmed in a porous substrate in which only the surface layer of the substrate was a SiO2 layer.

Furthermore, in the above embodiments, the composite material of the present invention was installed between the battery container and the porous body for air diffusion, but if the composite material of the present invention has sufficient mechanical strength, it is possible to There is no difference in battery characteristics even if the porous material is removed. Furthermore, in the above examples, the composite material of the present invention was installed 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 composite material according to the present invention has excellent practical performance in a wide range from heavy loads to light loads of batteries using a neutral or alkaline aqueous solution as an electrolyte. Leak resistance.

It has the effect of being able to be stored for a long time.

[Brief explanation of the drawing]

Figure 1 is a cross-sectional view of a button-type zinc-air battery used to study examples and comparative examples of the present invention, and Figure 2 is a conventional button-type zinc-air battery that does not use a water vapor and carbon dioxide selective barrier composite material. It is a sectional view of a battery. 1... Oxygen electrode (air electrode), 2... Water repellent membrane, 3... Air intake hole, 4... Porous membrane, 5, 6... ...Senokureta, 7...
Negative electrode zinc, 8... Negative electrode container, 9... Insulating gasket, 10... Positive electrode container, 11...
...Water vapor and carbon dioxide selective barrier composite material.

Claims (8)

[Claims] (1) A gas diffusion electrode containing oxygen as an active material and a battery container having an air intake hole communicating with the outside air, wherein a hole diameter of 0.1 μm or less is provided between the air intake side of the gas diffusion electrode and the inner surface of the battery container. A battery in which a composite material in which a perovskite-type composite oxide thin film is formed is interposed on the surface of a porous material having micropores. (2) The battery according to claim 1, wherein the porous material has SiO_2 as a main component. (3) The battery according to claim 1 or 2, wherein the perovskite-type composite oxide comprises at least the elements La, Co, and O. (4) The thickness of the composite oxide is 0.01 to 1.0 μm
A battery according to claim 1, 2 or 3. (5) 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 using the composite material between the air intake side of the gas diffusion electrode and the inner surface of the battery container. A battery according to any one of claims 1 to 4. (6) The battery according to claim 5, wherein the composite material is in direct contact with the inner surface of the battery container having an air intake hole and the gas diffusion electrode. (7) The battery according to claim 5 or 6, wherein an air diffusion porous material such as a nonwoven fabric is interposed between the composite material and the battery container. (8) The method according to any one of claims 5 to 7, wherein a microporous membrane that supports an oxygen electrode made of a porous film is interposed between the composite material and the gas diffusion electrode. battery.