JP3395440B2 - Air electrode current collecting material for air battery and air battery provided with the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current collecting material for a gas diffusion electrode using oxygen as an active material, and a battery equipped with the current collecting material.

[0002]

2. Description of the Related Art Conventionally, stainless steel wire, nickel wire or stainless steel has been plated with nickel for the current collecting material of the gas diffusion electrode (air electrode), which is the positive electrode of an air battery, from the viewpoint of conductivity and stability of the electrolytic solution. A wire net made of plain weave is used as a substrate. Then, using these metal nets as core materials, carbon black as a catalyst powder supporting platinum or manganese oxide, carbon black is added as a conductive material to a mixed powder of activated carbon, and a water-soluble fluororesin dispersion is kneaded as a binder. The gas diffusion electrode is constructed by filling the above-mentioned material.

[0003]

However, when the above conventional current collecting material is incorporated into a battery as a gas diffusion electrode, a thin oxide film is formed on the surface due to the oxidizing action of oxygen, and alkali used as an electrolyte is not used. During storage of the battery, it may penetrate into a metal surface having a relatively high wettability and accelerate the oxidation action of the surface. When this surface oxidation progresses, the electrical contact state deteriorates, causing the discharge voltage to drop due to an increase in internal resistance, and the discharge capacity after storage decreases. In particular, in discharging by a large current, the increase in internal resistance becomes a big problem.

For this reason, it has been considered to use a metal net used as a substrate of a current collecting material coated with graphite conductive resin. The current collector material coated with the graphite conductive resin has a lower initial internal resistance than that of the battery not coated with the graphite conductive coating when it is configured as a battery, and exhibits stable internal resistance during storage. However, in order to take out a large current, it is necessary to further lower the internal resistance, to show a stable internal resistance during storage, and to obtain a battery excellent in heavy load discharge characteristics.

The present invention solves such a problem, and provides a battery excellent in heavy load discharge while lowering the internal resistance of the battery and suppressing an increase in the internal resistance.

[0006]

In order to solve these problems, an air electrode current collecting material for an air battery according to the present invention is a conductive coating material containing metal powder, graphite in a metal net, expanded metal or punching metal. Is applied, and this is used for an air electrode current collector to form an air battery. The metal wire of the metal net is made of stainless wire, nickel wire, or wire containing at least one of nickel-plated stainless steel, and the expanded metal or punching metal is stainless steel, nickel, or nickel-plated stainless steel. It consists of any one of the above.

Further, the conductive coating material contains one of graphite and metal powder nickel, silver or a mixture of nickel and silver as a conductive substance, and as a binder, among vinyl chloride, epoxy resin, polyamide imide and water glass. A paint containing at least one.

[0008]

Function: The electrical resistivity of graphite is relatively low at 1375 × 10 ⁻⁶ Ωcm, and the electrical resistivity is 6.8.
Nickel that is 4 × 10 ⁻⁶ Ωcm (20 ° C.), 1.59
By mixing silver having a density of × 10 ^-6 Ωcm (20 ° C) or a mixture thereof, the resistivity can be remarkably lowered.

Further, the water repellency of graphite is very high, and when a conductive paint containing graphite is applied to a metal net, the water repellency of the graphite makes it difficult for the electrolyte to permeate the surface of the metal net during storage of the battery, resulting in surface oxidation. Therefore, the electrical contact state is kept good and the internal resistance of the battery does not increase.

From the above, when a current collecting material in which a conductive coating containing metal powder and graphite is applied to a metal net is used, the internal resistance of the battery is lowered, and a heavy load discharge suppressing an increase in internal resistance due to storage is used. A battery having excellent characteristics can be obtained.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a sectional view of the structure of a cylindrical zinc-air battery to which the present invention is applied. In the figure, 4 is a cylindrical air electrode having a three-layer structure including a catalyst layer, 1 is a catalyst layer from the inside, 2 is a current collector layer, and 3 is a water-repellent fluororesin porous membrane layer.

The air electrode is obtained by pressing the catalyst layer sheet onto a current collector net coated with a conductive paint containing metal powder and graphite by pressing. This catalyst layer sheet was prepared by mixing 3 kg of activated carbon, 4 kg of manganese oxide, 1.5 kg of carbon black and 0.7 kg of fluororesin powder, kneading the mixture with ethyl alcohol, and extruding it into a flat belt shape. It is rolled into a 0.6 mm sheet by passing through two rollers heated to about 60 ° C. Next, a dispersion of fluororesin fine powder is applied to the rolled back side of the catalyst layer sheet and dried.

By coating this fluororesin dispersion liquid, it is possible to prevent the electrolytic solution from penetrating the electrode and forming a liquid film on this surface to interfere with the supply of oxygen gas. Finally, a water-repellent fluororesin porous membrane having gas permeability is press-bonded to the side coated with the fluororesin fine powder dispersion liquid, so that the catalyst layer 1, the current collector layer 2 and the fluororesin porous membrane layer 3 are separated from each other. Become 3
A flat plate air electrode 4 having a layered structure is prepared. The flat plate-made air electrode 4 thus formed is curved so that the catalyst layer 1 is on the inner side, and a part of both ends of the catalyst layer 1 and the fluororesin porous membrane layer 3 are overlapped to form a tubular shape.

Then, the catalyst layer 1 and the fluororesin porous membrane layer 3 at the overlapped portions are removed, and the exposed current collector layer 2 is spot-welded to form a synthetic rubber-based joint on the joint which is not liquid-tight. Fill the adhesive and repair it liquid-tightly. Through the above steps, the cylindrical air electrode 4 having a three-layer structure is completed. 5
Is a cellophane separator, and 6 is a gelled zinc negative electrode. The gelled zinc negative electrode 6 was prepared as follows. 40 wt% potassium hydroxide aqueous solution (containing 3 wt% zinc oxide)
Gelation is carried out by adding 3% by weight of sodium polyacrylate and 1% by weight of carboxymethyl cellulose. Next, zinc powder in a weight ratio twice that of the gel electrolyte was added and mixed to form a gel zinc negative electrode 6. 7 is an air diffusion paper, 8 is a positive electrode can, and 9 is an insulating tube. 10 is an air intake hole, 11 is a hermetic seal to be peeled off before using the battery, 1
2 is a plate and 13 is a positive electrode cap. Reference numerals 13 and 14 denote metal caps. A cylindrical air electrode is sandwiched between the caps 13 and 14 for pressure bonding, and spot welding is performed with a positive electrode can to collect current. Reference numeral 15 is an organic sealant, 16 is a resin sealing body, 17 is a negative electrode terminal cap, and 18 is a negative electrode current collector.

The cylindrical air zinc battery of the present invention produced by the above-mentioned method, and the one in which the conductive paint containing only graphite as a conductive substance is applied to the metal net and the one in which the conductive paint is not applied are gas diffusion electrodes. The cylindrical air zinc battery of the comparative example used as the battery was prepared. 1-No. It was set to 7. The internal resistance of the battery immediately after assembling these batteries and 60
Measurement of battery internal resistance after 10 days and 20 days of storage in a sealed state at ℃ and 3.9Ω immediately after assembly
Discharge capacity (0.9V cut) when discharged under heavy load
Battery type No. The battery of No. 7 is shown as an index in Table 1 (Table 1).

[0017]

[Table 1]

In Table 1, the battery type No. 1 is wire diameter 1
A 40 mesh net made of 60 μm stainless wire is plated with nickel about 3 μm, and nickel powder and graphite powder are used as conductive substances, and a conductive paint that is an epoxy resin is applied as a binder, and the resulting current collector is dried. It is the battery used. Similarly, the battery type No. No. 2 is a battery using silver as a metal powder of a conductive material instead of nickel. 3 to No. Battery type N up to 5
o. It is a battery in which the binder of No. 2 was used in place of that shown in (Table 1). Battery type No. No. 6 is a battery using only graphite powder as a conductive substance, and battery type No. Reference numeral 7 is a battery using a current collector that is plated only with nickel and is not coated with a conductive paint. As is clear from (Table 1),
Battery type No. 1 to No. The batteries up to 5 are battery type No.
Even when compared with the battery in which the conductive paint of No. 7 is not used, the battery type No. It can be seen that the internal resistance at the beginning is low and the internal resistance after storage is also low, compared with the battery using only graphite of 6.

The discharge capacity index at the right end of Table 1 is the discharge capacity when the battery just assembled was discharged at 3.9Ω (0.
Battery type No. 7 is an index when 7 is 100. As can be seen from this table, by keeping the internal resistance of the battery low, the heavy load discharge capacity increases in proportion to it. It is considered that the reduction of the internal resistance when the battery voltage is cut by 0.9 V reduces the IR polarization component at the time of discharging, and as a result, the discharge capacity is increased. Also, after storing at 60 ° C. for 20 days (sealed state), discharging was performed by the same method, but battery type No. 1
To No. The discharge capacity of No. 6 was almost the same as that immediately after assembling, but no. 7 was about 30% lower.

From the above, it is possible to suppress the internal resistance of the battery to a low level and increase the discharge capacity during heavy load discharge by applying a conductive coating material using metal powder and graphite powder as the conductive material to the current collector. Moreover, the electrical contact state after storage was maintained, and the increase in internal resistance of the battery after storage could be suppressed to a small level.

In this embodiment, a wire made of stainless steel plated with nickel is used as the metal wire of the metal net as the substrate of the current collector. However, the same effect can be obtained when a stainless wire or a nickel wire is used.

In this embodiment, the metal net is used as the substrate of the current collector, but the same effect can be obtained when expanded metal or punching metal is used.

[0023]

As is apparent from the above, according to the present invention, by using a metal net, an expanded metal or a punching metal with an electrically conductive coating material containing metal powder and graphite, The internal resistance of the battery can be reduced and the increase in internal resistance due to storage can be suppressed,
A battery excellent in heavy load discharge can be provided.

[Brief description of drawings]

FIG. 1 is a structural cross-sectional view of a cylindrical zinc-air battery according to an embodiment of the present invention.

FIG. 2 is an enlarged structural sectional view of a portion A in FIG.

[Explanation of symbols]

1 catalyst layer 2 Current collector layer 3 Water repellent fluororesin porous membrane layer 4 air poles 5 cellophane separator 6 Gel-like zinc negative electrode 7 Air diffusion paper 8 positive electrode can 9 Insulation tube 10 Air intake hole 11 hermetic seal 12 dish paper 13 Positive electrode cap 14 Metal cap 15 Organic sealant 16 Resin sealing body 17 Negative electrode terminal cap 18 Negative electrode current collector

Front page continuation (72) Inventor Shigeo Kobayashi 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd. (56) References JP-A-1-122561 (JP, A) JP-A-2-281560 (JP , A) JP 1-167956 (JP, A) JP 6-267594 (JP, A) JP 60-1770 (JP, A) JP 47-26639 (JP, A) Actual development Sho 58-53371 (JP, U) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 4/66 H01M 4/74 H01M 12/06

Claims (10)

(57) [Claims] 1. An air electrode current collecting material for an air battery, characterized in that a metal net, expanded metal, or punching metal is coated with a conductive coating material containing metal powder and graphite. 2. The air electrode current collecting material for an air battery according to claim 1, wherein the metal wire of the metal net is a wire including at least one of a stainless wire, a nickel wire, and a wire obtained by plating stainless with nickel. 3. The air electrode current collector material for an air battery according to claim 1, wherein the expanded metal or punching metal is made of stainless steel, nickel, or stainless steel plated with nickel. 4. The air electrode current collecting material for an air battery according to claim 1, wherein the metal powder is any one of nickel, silver or a mixture of nickel and silver. 5. The air electrode assembly for an air battery according to claim 1, wherein the conductive paint contains metal powder and graphite, and contains as a binder at least one of vinyl chloride, epoxy resin, polyamide imide and water glass. Electrical materials. 6. An air comprising an air electrode current collecting material for an air battery, which is obtained by applying a conductive coating material containing metal powder and graphite on a metal net, expanded metal, or punching metal, as a positive electrode current collector. battery. 7. The air battery according to claim 6, wherein the metal wire of the metal net is a wire including at least one of a stainless wire, a nickel wire, and a stainless-plated wire. 8. The air battery according to claim 6, wherein the expanded metal or punching metal is made of stainless steel, nickel, or stainless steel plated with nickel. 9. The air battery according to claim 6, wherein the metal powder is one of nickel, silver or a mixture of nickel and silver. 10. The air battery according to claim 6, wherein the conductive paint contains metal powder and graphite, and contains as a binder at least one of vinyl chloride, epoxy resin, polyamide imide and water glass.