JP2000268888A - Air battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an air battery equipped with excellent load characteristics. SOLUTION: This air battery includes a current collector 5 and catalyst layer 6 in lamination and uses the oxygen in the air as positive electrode active material, wherein the catalyst layer 6 contains a carbon material adsorbing positive electrode active material, and the specific surface area per unit weight of carbon material should range between 900 and 1500 m2/g, while the mean particle size of the carbon material should preferably be 8 to 60 μm. It is also preferable that the carbon material is formed by baking wood powder.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an air battery having an air electrode utilizing oxygen in air for a positive electrode reaction.

[0002]

2. Description of the Related Art As a battery, there is a so-called air battery which is a primary battery having an air electrode utilizing oxygen in air for a positive electrode reaction. Since the air battery uses oxygen as the positive electrode active material, it does not need to be filled with a powder such as manganese dioxide, and has a feature that the air electrode can be thinned. As described above, in the air battery, since the thickness of the air electrode serving as the positive electrode can be reduced, the volume of the negative electrode can be increased accordingly. Therefore, the air battery
The battery has a very large discharge capacity per volume and achieves a high energy density.

[0003] An air battery comprises a battery can having at least one or more air holes, an air electrode having a porous electrode material, and a gelled negative electrode mixture comprising a negative electrode active material and an electrolytic solution. Are stored via a separator. In this air battery, external air flows in from an air hole formed in the battery can, and oxygen contained in the flowed-in air is adsorbed on the porous electrode material to cause a positive electrode reaction.

Meanwhile, the air electrode is formed by kneading a catalyst material having an oxygen reducing ability, a carbon material, and a binder to form a paste, applying the paste to a current collector such as a nickel net, and then drying the paste. It is formed by disposing a water-repellent film on one main surface. In the air electrode thus formed, the layer applied to the current collector serves as a catalyst layer, and a positive electrode reaction using oxygen in the air occurs in the catalyst layer.

[0005]

However, in the above-described air battery, since the air electrode contains a large amount of a binder which is an insulator, the internal resistance is increased, and as a result, the load characteristics are reduced. There was a problem that it was not excellent. In other words, at present, sufficient characteristics have not been obtained with the conventional air battery.

Accordingly, an object of the present invention is to provide an air battery exhibiting excellent load characteristics.

[0007]

According to the present invention, there is provided an air battery having a catalyst layer laminated with a current collector, wherein oxygen in the air is used as a positive electrode active material. the catalyst layer contains a carbon material that adsorbs the positive electrode active material, the specific surface area per unit weight of the carbon material characterized in that it is a 900m ² / g~1500m ² / g.

In the air battery according to the present invention having the above-described structure, a sufficient amount of oxygen is adsorbed on the carbon material by defining the specific surface area of the carbon material contained in the catalyst layer to a predetermined value. Can be done. Then, in this air battery, load characteristics according to the amount of oxygen adsorbed on the carbon material are exhibited.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of an air battery according to the present invention will be described in detail with reference to the drawings.

As shown in FIG. 1, an air battery shown as an embodiment has a cathode can 2 having at least one air hole 1 and an air cathode 3 utilizing oxygen in the air for a cathode reaction and a cathode mixture. 4 is provided. In this air battery, the air electrode 3 is formed of a current collector 5, a catalyst layer 6, and a water-repellent film 7, is formed in a hollow cylindrical shape, and is housed inside the positive electrode can 2 via a diffusion paper 9. . The negative electrode mixture is filled via a separator 8 into a space defined by the inner peripheral surface of the air electrode 3 formed in a cylindrical shape. That is, the separator 8 is disposed on the inner peripheral surface of the air electrode 3 so as to be in contact therewith, and the space surrounded by the separator 8 is filled with the negative electrode mixture 4.

Here, as the current collector 5, a conductive metal net, expanded metal, punched metal, or the like is used. For example, stainless steel, nickel, or stainless steel or iron plated with nickel is used. .

The catalyst layer 6 is a layer that adsorbs oxygen as a positive electrode active material and causes a positive electrode reaction using the oxygen. The catalyst layer 6 is formed by kneading a composite catalyst obtained by adhering a metal compound having an oxygen reduction catalytic ability to a carbon material having a predetermined specific surface area together with a binder to form a paste. It is formed by applying to the body 5.

[0013] In the catalyst layer 6, the specific surface area of the carbon material is 900m ² / g~1600m ² / g, more preferably 1000m ² / g~1500m ² / g.
The specific surface area of the carbon material is a so-called N ₂ -BET.
It is a value measured according to the method. In order to produce such a carbon material, a material such as wood powder is fired and further activated. In particular, at this time, the specific surface area of the carbon material can be controlled by controlling the firing conditions.

Further, the carbon material has an average particle size of 8 μm.
To 60 μm, more preferably 10 μm to
More preferably, it is 50 μm. The average particle size of the carbon material is a value measured according to a so-called laser scattering method.

Further, as the metal compound to be attached to the carbon material in the catalyst layer 6, a conventionally known material can be used. For example, as the metal compound, a noble metal such as a platinum group element or silver having a high oxygen reduction catalytic activity, a manganese oxide, or the like can be used.

Further, as the binder, conventionally known materials can be used. For example, as the binder, a fluororesin binder such as polytetrafluoroethylene can be used. The fluororesin binder is preferably used in the form of an aqueous dispersion by the action of a surfactant. Then, the binder is mixed at a predetermined ratio with the composite catalyst composed of the carbon material and the metal compound. At this time, the ratio between the binder and the composite material is
It can be appropriately selected according to the purpose of use.

As a method of uniformly kneading the binder and the composite material, for example, when a fluororesin binder is used,
The composite catalyst may be dispersed in an aqueous dispersion of a fluororesin binder using water, alcohol, or the like to form a paste. Then, the paste obtained by kneading the binder and the composite material is applied in the form of a current collector 5 by a transfer roller method, and then dried.

On the other hand, as the water repellent film 7, a fluororesin porous film having gas permeability and water repellency is used. The water-repellent film 7 is a film provided to prevent liquid leakage of the negative electrode mixture 4 and allow oxygen to pass therethrough.

In this air battery, a metal sealing member 10 is provided at one end 3a of the air electrode 3 to prevent the negative electrode mixture 4 from leaking. This sealing member 1
0 is formed by bending a metal flat plate having a predetermined thickness.

Further, a metal ring member 14 having a substantially U-shaped cross section is disposed at the other end 3b of the air electrode 3, and a gasket 15 is disposed so as to adhere to the ring member 14. Has been established. In addition, this gasket 1
5 is provided with a negative electrode terminal plate 17 penetrated by a nail-shaped negative electrode current collector 16 and electrically connected to the base end of the negative electrode current collector 16. Then, the other end 3 b of the air electrode 3 is sealed by the ring member 14 and the gasket 15.

Furthermore, in this air battery, the air electrode 3 has one end 3a sealed by a sealing member 10,
The other end 3b is the ring member 14 and the gasket 1
5 is disposed in the positive electrode can 2 while being sealed.
Here, the gasket 15 has an outer diameter substantially equal to the inner diameter of the positive electrode can 2 and is fitted so as to be in contact with the inner peripheral surface of the positive electrode can 2. In addition, this gasket 15
Is formed using, for example, an insulating resin, so that leakage between the positive electrode can 2 and the negative electrode terminal plate 17 can be prevented.

Further, in this air battery, an exterior film 18 is wound around the outer peripheral surface of the positive electrode can 2. The exterior film 18 is provided with an inflow hole 19 into which external air flows in a position corresponding to the air hole 1, so that air can be supplied to the air electrode 3. Generally, a label printed with a company name, a precautionary statement, and the like is attached to the outermost shell of the air battery. Accordingly, the exterior film 18 can have such printability.
In such a case, it is preferable to use a film that is easy to print and has a smooth surface as the exterior film 10, and particularly, an ester resin, an imide resin, an amide resin, a silicone resin, a urethane resin, Acrylic resins, styrene resins, vinyl resins, olefin resins, cellulose resins, polycarbonates, polyacetals, and copolymers containing these are preferably used.

In the air battery configured as described above, external air flows in from the inflow hole 19 and is supplied to the air electrode 3. And in this air battery, the air electrode 3
As a result, a positive electrode reaction utilizing oxygen in the air occurs. At this time, the oxygen in the air is adsorbed by the carbon material in the catalyst layer 6 and causes a positive electrode reaction by the oxygen reduction catalytic action of the metal compound in the catalyst layer 6.

[0024] At this time, in the air battery described above, the specific surface area of the carbon material is a 900m ² / g~1600m ² / g, more preferably, 1000m ² / g~1500m ² /
g, the amount of oxygen adsorbed per unit weight of the carbon material is large. That is, in the above-described air battery, the amount of adsorbed oxygen can be increased without increasing the volume of the catalyst layer 6.

Thus, in this air battery, the positive electrode reaction occurs efficiently, and the discharge characteristics under heavy load are excellent. Also, in this air battery, as described above, by defining the specific surface area of the carbon material,
Excellent discharge characteristics can be exhibited even after long-term storage. In contrast, the specific surface area of the carbon material is 9
If it is less than 00 m ² / g, the discharge envoy under heavy load will not show an excellent value. Also, when the specific surface area of the carbon material exceeds 1600 m ² / g, the discharge characteristics under heavy load are not excellent.

In the above-described air battery, the carbon material has an average particle diameter of 8 μm to 60 μm, and more preferably 10 μm
It is preferably from 50 μm to 50 μm. By defining the average particle size of the carbon material in this manner, more excellent discharge characteristics are exhibited.

By the way, in the embodiment described above, FIG.
As described above, a cylindrical air battery is illustrated, but the present invention is not limited to such a configuration. That is, the air battery according to the present invention may be a so-called button-type air battery.

[0028]

EXAMPLES Specific examples of the air battery according to the present invention and comparative examples for comparison with this example were produced, and the characteristics of these examples and comparative examples were evaluated.

Example 1 An air electrode is manufactured as follows. First, a paste for forming a catalyst layer is prepared.

Β-manganese oxide powder (MnO ₂ )
Activated carbon (specific surface area 1154 m ² / g, average particle size 32.6
μm) and a mixture of carbon black (hereinafter, AC + C
Abbreviated as B. ) And polytetrafluoroethylene (hereinafter referred to as P) having a solid content of 60% as a water-repellent fluororesin binder.
Abbreviated as TFE. ) And MnO ₂ : AC + CB: P
It mixed so that TFE = 2: 2: 1. Thus, a paste for forming a catalyst layer was prepared. In addition, this activated carbon was formed by baking wood flour.

Next, this paste is made of a sheet-shaped nickel-plated stainless steel (SUS30).
4) It was applied on a net to a thickness of 0.5 mm and dried to prepare a catalyst layer sheet. Then, a porous PTFE film having a thickness of 0.1 mm was pressure-bonded to one main surface of the catalyst layer sheet to produce an air electrode sheet.

Next, a button-type battery having a diameter of 23 mm and a height of 3 mm was manufactured using the air electrode sheet thus manufactured. As shown in FIG. 2, this button-type battery includes a positive electrode case 30 in which nickel is plated on iron, an air hole 31 formed in the positive electrode case 30, an air diffusion material 32 for diffusing air, and an air electrode sheet. Air electrode 33, air diffusing material 32 and air electrode 33 punched to a diameter of 22.5 mm
And a separator 35 made of a microporous polypropylene film, an electrolyte holding material 36 made of a natural pulp material, a gasket 37 made of nylon, a copper / stainless steel / nickel A negative electrode cup 38 made of a clad material, a gelled negative electrode mixture 39 made of a mixture of zinc alloy particles, a gelling agent and a potassium hydroxide solution, and an air hole seal 40 are assembled in the same manner as a conventional button-type air battery. Thus, the air battery of Example 1 is manufactured.

Example 2 In Example 2, an activated carbon having a specific surface area of 1420 m ² / g and an average particle size of 32.6 μm was used.
In the same manner as in the above, an air battery was produced.

Example 3 In Example 3, an activated carbon having a specific surface area of 1027 m ² / g and an average particle size of 18.8 μm was used.
In the same manner as in the above, an air battery was produced.

Example 4 In Example 4, an activated carbon having a specific surface area of 1280 m ² / g and an average particle size of 54.8 μm was used.
In the same manner as in the above, an air battery was produced.

Example 5 In Example 5, an air battery was fabricated in the same manner as in Example 1, except that activated carbon having a specific surface area of 1485 m ² / g and an average particle size of 8.1 μm was used.

Example 6 Example 6 was repeated except that activated carbon having a specific surface area of 1471 m ² / g and an average particle size of 62.3 μm was used.
In the same manner as in the above, an air battery was produced.

Example 7 In Example 7, an air battery was fabricated in the same manner as in Example 1, except that activated carbon having a specific surface area of 967 m ² / g and an average particle size of 26.3 μm was used.

Example 8 In Example 8, air was produced in the same manner as in Example 1 except that the specific surface area was 1,428 m ² / g, the average particle size was 12.6 μm, and activated carbon obtained by firing coconut shells was used. A battery was manufactured.

Example 9 In Example 9, an air cell was manufactured in the same manner as in Example 1 except that the specific surface area was 1496 m ² / g, the average particle size was 38.22 μm, and activated carbon obtained by calcining phenol was used. Was prepared.

Comparative Example 1 In Comparative Example 1, an air battery was manufactured in the same manner as in Example 1 except that activated carbon having a specific surface area of 1627 m ² / g and an average particle size of 22.14 μm was used.

Comparative Example 2 In Comparative Example 2, an air battery was manufactured in the same manner as in Example 1 except that the specific surface area was 896 m ² / g, the average particle size was 35.36 μm, and activated carbon obtained by firing PAN was used. Was prepared.

Comparative Example 3 In Comparative Example 3, an air battery was produced in the same manner as in Example 1 except that the specific surface area was 1753 m ² / g, the average particle size was 28.54 μm, and activated carbon made of coal was used. .

COMPARATIVE EXAMPLE 4 Comparative Example 4 was carried out in the same manner as in Example 1 except that the specific surface area was 1685 m ² / g, the average particle size was 6.0 μm, and activated carbon obtained by firing a coconut shell was used. A battery was manufactured.

Evaluation of Characteristics These Examples 1 to 9 and Comparative Examples 1 to 4
, A heavy load closed circuit voltage characteristic test, an internal resistance value characteristic test, and a heavy load discharge characteristic test were performed before storage and after long-term storage (stored at 60 ° C. for 40 days).

<Heavy Load Closed Circuit Voltage Characteristics Test> Ten minutes after opening the air hole seal, a load resistance of 20Ω was connected for 5 seconds, and the closed circuit voltage (CCV, unit [V]) at that time was measured. . According to this test, the higher the battery voltage, the better.

<Internal Resistance Value Characteristic Test> 10 minutes after opening the air hole seal, an AC current of 1 μA and 1 kHz was applied to the battery, and the AC resistance (Ri, unit [mΩ]) at this time was applied.
Was measured. According to this test, the smaller the resistance value, the better.

<Heavy Load Discharge Characteristics Test> Ten minutes after opening the air hole seal, a 42 Ω load resistance was connected to the battery.
Discharge capacity until the battery voltage falls below 0.9 V (unit [m
Ah]). According to this test, the larger the numerical value, the larger the discharge capacity, which is preferable.

Together with the results of the heavy load closed circuit voltage characteristic test, internal resistance value characteristic test and heavy load discharge characteristic test,
Table 1 shows various physical properties of the activated carbon used.

[0050]

[Table 1]

As is clear from Table 1, the specific surface area of the activated carbon was 900 as shown in Comparative Examples 1 to 4.
Air batteries outside the range of １1600 m ² / g did not show good results in at least one of the heavy load closed circuit voltage characteristic test, internal resistance value characteristic test, and heavy load discharge characteristic test. . On the other hand, as shown in Examples 1 to 9, the activated carbon has a specific surface area of 900 to 1
The air battery having the range of 600 m ² / g has good results in all of the heavy load closed circuit voltage characteristic test, the internal resistance value characteristic test, and the heavy load discharge characteristic test.

From the results shown in Table 1, the average particle size was 8
It can be seen that the best results are obtained when activated carbon in the range of μm to 60 μm and the raw material is wood flour is used.

[0053]

Effect of the Invention] As described above in detail, the air cell according to the present invention, the specific surface area per unit weight of the carbon material is specified within a range of 900m ² / g~1500m ² / g And excellent load characteristics.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing one configuration example of an air battery according to the present invention.

FIG. 2 is a sectional view of a main part of the button-type air battery manufactured in the example.

[Explanation of symbols]

1 air hole, 2 positive electrode can, 3 air electrode, 4 negative electrode mixture,
Reference Signs List 5 current collector, 6 catalyst layer, 7 water-repellent film, 8 separator, 10 sealing member, 11 first annular portion, 12 second annular portion, 13 bottom portion, 14 ring member, 15 gasket, 16 negative electrode current collector Body, 17 negative electrode terminal plate, 18 exterior film, 19 inflow hole

Claims (3)

[Claims] 1. An air battery having a catalyst layer laminated with a current collector and using oxygen in air as a positive electrode active material, wherein the catalyst layer contains a carbon material that adsorbs the positive electrode active material, Specific surface area per unit weight of the carbon material is 900 m ²
/ G to 1600 m ² / g. 2. The carbon material has an average particle size of 8 μm to 60 μm.
The air battery according to claim 1, wherein the diameter of the air battery is μm. 3. The air battery according to claim 1, wherein the carbon material is obtained by firing wood powder.