WO2015119041A1

WO2015119041A1 - Air electrode and metal air battery

Info

Publication number: WO2015119041A1
Application number: PCT/JP2015/052551
Authority: WO
Inventors: 将史村岡; 忍竹中; 吉田　章人; 宏隆水畑; 友春新井; 俊輔佐多
Original assignee: シャープ株式会社
Priority date: 2014-02-04
Filing date: 2015-01-29
Publication date: 2015-08-13

Abstract

This metal air battery comprises: an electrolytic solution tank for storing an electrolytic solution; a metal electrode that is provided within the electrolytic solution tank and that contains at least an electrode active material; and an air electrode that forms a wall part of a part of the electrolytic solution tank. The air electrode has a collector and an air electrode catalytic layer that contains at least an air electrode catalyst. The metal air battery contains a gelling agent on a first main surface-side of the air electrode opposing the electrolytic solution, or on the air electrode catalytic layer.

Description

Air electrode and metal-air battery

The present invention relates to an air electrode and a metal-air battery.

Since metal-air batteries have high energy density, they are attracting attention as next-generation batteries. The metal-air battery is discharged by using a metal electrode containing an electrode active material and disposed in an electrolyte as an anode and an air electrode as a cathode.
As a typical metal-air battery, a zinc-air battery using metal zinc as an electrode active material can be mentioned. In a zinc-air battery, it is considered that an electrode reaction of the following chemical formula 1 proceeds at the cathode.
(Chemical formula 1): O ₂ + 2H ₂ O + 4e ⁻ → 4OH ⁻
Moreover, it is considered that an electrode reaction (dissolution reaction of metallic zinc) as shown in the following chemical formula 2 proceeds at the anode.
(Chemical formula 2): Zn + 4OH ⁻ → Zn (OH) ₄ ²⁻ + 2e ⁻

When such an electrode reaction proceeds, the electrode active material of the metal electrode is consumed and gradually decreases. When the electrode active material is reduced, the used metal electrode is removed from the electrolytic solution, and a new metal electrode is inserted into the electrolytic solution to perform re-discharge (see, for example, Patent Document 1).
As the electrode reaction progresses, the concentration of metal-containing ions (Zn (OH) ₄ ²⁻ ) in the electrolyte gradually increases, and when saturation is reached, a reaction such as the following chemical formula 3 or chemical formula 4 proceeds. Homogeneous nucleation or heterogeneous nucleation occurs. Then, as the produced nucleus grows, a metal oxide or metal hydroxide precipitate is deposited and accumulated in the electrolytic solution tank as a used active material.
(Chemical formula 3): Zn (OH) ₄ ²⁻ → ZnO + 2OH ⁻ + H ₂ O
(Chemical formula 4): Zn (OH) ₄ ²⁻ → Zn (OH) ₂ + 2OH ⁻

In such a metal-air battery, H ₂ O required for the cathode reaction at the air electrode is mainly supplied from the electrolyte, so that the electrolyte in the electrolyte tank leaks to the outside of the battery through the pores of the air electrode. There is a case. Since alkaline aqueous solution etc. are used for electrolyte solution, if electrolyte solution leaks out of a battery, the safety of a metal air battery will fall.
In order to prevent leakage of the electrolytic solution, a zinc-air battery in which a solidifying agent is incorporated in advance in an electrolytic solution tank before injection of the electrolytic solution is known (for example, see Patent Document 2). In this zinc-air battery, by solidifying the electrolytic solution, the fluidity of the electrolytic solution in the electrolytic solution tank is lowered to prevent leakage of the electrolytic solution.
In addition, in order to prevent leakage of the electrolytic solution, a metal air battery having a porous PTFE membrane outside the air electrode and a metal air battery having an air electrode catalyst layer containing a fluororesin are known ( For example, see Patent Documents 3 and 4).

JP 2005-509262 A Japanese Patent Publication No.58-55625 JP-A-8-7935 JP-A-6-338355

However, in a metal-air battery that solidifies the electrolyte in the electrolyte bath, it is difficult to replace the used metal electrode with a new metal electrode and discharge again. In addition, since the electrolytic solution in the electrolytic solution tank cannot be circulated, the discharge time is shortened.
Further, in a metal-air battery in which the metal electrode is replaced and repeatedly discharged, when the used metal electrode is removed from the electrolytic solution, the electrolytic solution may drip from the extracted metal electrode, which is dangerous.
Furthermore, in metal-air batteries equipped with an air electrode containing fluororesin, the water repellency due to the fluororesin gradually decreases, and the electrolyte may leak through the air electrode. May decrease.
The present invention has been made in view of such circumstances, and provides a metal-air battery that can be repeatedly discharged by exchanging metal electrodes and the like and can prevent leakage of the electrolyte to the outside. provide.

The metal-air battery of the present invention forms an electrolytic solution tank that contains an electrolytic solution, a metal electrode that is provided in the electrolytic solution tank and includes at least an electrode active material, and a part of the wall of the electrolytic solution tank. A metal-air battery including an air electrode, wherein the air electrode includes a current collector and an air electrode catalyst layer including at least an air electrode catalyst, and the first electrode of the air electrode facing the electrolyte solution. One main surface side or the air electrode catalyst layer includes a gelling agent.
Further, the metal-air battery of the present invention includes an electrolytic bath that contains an electrolytic solution, a metal electrode that is provided in the electrolytic bath, and includes at least an electrode active material, and a part of the wall of the electrolytic bath. A metal-air battery including an air electrode to be formed, the air electrode including a current collector and an air electrode catalyst layer including at least an air electrode catalyst, and the air facing the electrolyte solution A gel layer containing at least a gelling agent and water is provided between the first main surface of the pole.
Furthermore, the air electrode of the present invention is an air electrode having a current collector and an air electrode catalyst layer containing at least an air electrode catalyst, wherein the air electrode catalyst layer is part of the surface side of the air electrode or the air electrode catalyst layer. It contains an agent.

According to the present invention, an anode tank is allowed to advance in the metal electrode since the electrolyte tank containing the electrolyte, the metal electrode including at least the electrode active material, and the air electrode are provided in the electrolyte tank. The cathode reaction can proceed at the air electrode. Thereby, an electromotive force can be generated between the metal electrode and the air electrode, and a discharge current can flow.

According to the present invention, since the gelling agent is included in the first main surface side of the air electrode facing the electrolytic solution stored in the electrolytic solution tank, or the air electrode catalyst layer in the air electrode, the electrolysis that has penetrated into the air electrode. Since the liquid and the gelling agent form a gel and suppress the permeation of the electrolytic solution in the air electrode, leakage of the electrolytic solution to the outside can be suppressed.
Moreover, according to the present invention, the gel layer containing the gelling agent and the water contained in the electrolyte is formed on the first main surface side of the air electrode facing the electrolyte contained in the electrolyte bath, It is possible to suppress leakage of the electrolytic solution to the outside.
When a gel layer is formed between the electrolyte solution accommodated in the electrolyte bath and the air electrode, the electrolyte solution contained in the electrolyte bath can be prevented from flowing directly into the pores of the air electrode, Leakage of the electrolyte solution to the outside through the pores of the air electrode can be suppressed. Thereby, the safety and reliability of the metal-air battery can be improved. Moreover, since the rate at which the electrolytic solution permeates the gel layer is slow, an appropriate amount of water can be supplied to the air electrode. Moreover, by forming a gel layer, it is possible to prevent deposits generated from the electrode active material from adhering to the air electrode and hydrogen gas generated by self-corrosion of the metal electrode from flowing into the air electrode. . Thereby, it is possible to suppress a decrease in battery characteristics and output stability.

It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. FIG. 2 is a schematic sectional view of the metal-air battery taken along a broken line AA in FIG. (A) is a schematic sectional drawing of the metal air battery of one Embodiment of this invention, (b) is a schematic sectional drawing of the porous body contained in the metal air battery shown to (a). (A) is a schematic sectional drawing of the metal air battery of one Embodiment of this invention, (b) is a schematic sectional drawing of the porous body contained in the metal air battery shown to (a). (A) is a schematic sectional drawing of the metal air battery of one Embodiment of this invention, (b) is a schematic sectional drawing of the air electrode catalyst layer contained in the metal air battery shown to (a). It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention. It is a schematic sectional drawing of the metal air battery of one Embodiment of this invention.

The metal-air battery of the present invention includes an electrolyte bath that contains an electrolyte, a metal electrode that is provided in the electrolyte bath and includes at least an electrode active material, and an air electrode that forms a part of the wall of the electrolyte bath. The air electrode has a current collector and at least an air electrode catalyst layer, and includes a gelling agent in the first main surface side of the air electrode facing the electrolyte solution or in the air electrode catalyst layer. And
Further, the metal-air battery of the present invention forms an electrolytic solution tank that contains an electrolytic solution, a metal electrode that is provided in the electrolytic solution tank and includes at least an electrode active material, and a part of the wall of the electrolytic solution tank. A metal-air battery including an air electrode, the air electrode including a current collector and an air electrode catalyst layer including at least an air electrode catalyst, an electrolyte, and a first main electrode of the air electrode facing each other. A gel layer containing at least a gelling agent and water is provided between the surface and the surface.
Furthermore, the air electrode of the present invention is an air electrode having a current collector and an air electrode catalyst layer containing at least an air electrode catalyst, wherein a part of the surface side of the air electrode or the air electrode catalyst layer is a gelling agent. It is characterized by including.

In the metal-air battery or air electrode of the present invention, the gelling agent is preferably a water-absorbing polymer, and the gel layer is preferably a polymer hydrogel layer containing a gelling agent and an aqueous dispersion medium.
According to such a configuration, it is possible to suppress an increase in the ion conduction resistance between the anode and the cathode, and it is possible to improve the discharge characteristics of the metal-air battery while preventing external leakage of the electrolytic solution.
In the metal-air battery of the present invention, the gel layer is preferably provided so as to cover the air electrode.
According to such a configuration, the electrolyte contained in the electrolyte bath can be prevented from flowing directly into the pores of the air electrode, and leakage of the electrolyte to the outside through the pores of the air electrode can be prevented. Can be suppressed.

In the metal-air battery of the present invention, it is preferable that the first main surface between the air electrode and the electrolytic solution is formed of a porous body, and the gelling agent is provided in the porous body.
According to such a structure, it can suppress that the shape of a gel layer deform | transforms or peels with the flow of the electrolyte solution in an electrolyte solution tank. This can increase the effect of suppressing leakage of the electrolyte.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. The configurations shown in the drawings and the following description are merely examples, and the scope of the present invention is not limited to those shown in the drawings and the following description.

Configuration of Metal-Air Battery FIGS. 1, 3A, 4A, 5A, 6, 7, and 8 are schematic cross-sectional views of the metal-air battery of this embodiment. FIG. 2 is a schematic cross-sectional view of the metal-air battery taken along broken line AA in FIG. 3B and 4B are schematic cross-sectional views of the porous body 32, respectively, and FIG. 5B is a schematic cross-sectional view of the air electrode catalyst layer.
The metal-air battery 30 of the present embodiment includes an electrolytic solution tank 2 that contains the electrolytic solution 3, a metal electrode 5 that is provided in the electrolytic solution tank 2 and includes at least an electrode active material, and a part of the electrolytic solution tank 2. A metal-air battery including an air electrode 9 that forms a wall, and the air electrode 9 includes a current collector 10 and an air electrode catalyst layer 7 including at least an air electrode catalyst, and the electrolytic solution 3 A gelling agent is included in the first main surface side of the air electrode 9 or the air electrode catalyst layer 7 opposed to the air electrode 9.
Hereinafter, the metal-air battery 30 of this embodiment will be described.

1. Metal-air battery The metal-air battery 30 of the present embodiment is a battery in which the metal electrode 5 containing a metal serving as an electrode active material is a negative electrode (anode) and the air electrode 9 is a positive electrode (cathode). For example, a zinc air battery, a lithium air battery, a sodium air battery, a calcium air battery, a magnesium air battery, an aluminum air battery, and an iron air battery. Further, the metal-air battery 30 of the present embodiment may be a primary battery or a secondary battery. Further, the metal-air battery 30 of the present embodiment may be a battery that can be repeatedly discharged by replacing the metal electrode 5.
The metal-air battery 30 has a metal-air battery body composed of the electrolytic solution tank 2, the air electrode 9 and the like, and a structure that can be attached to and detached from the metal-air battery body, and is composed of a metal electrode 5, a metal electrode terminal 41, and the like. You may comprise from an electrode holder.

2. Cell The cell 4 is a structural unit of the metal-air battery 30 and has an electrode pair that is provided in the electrolyte bath 2 (electrolyte chamber) and includes a metal electrode 5 serving as an anode and an air electrode 9 serving as a cathode. . The cell 4 may have, for example, an electrode pair in which one air electrode 9 and one metal electrode 5 are provided so as to sandwich the electrolytic solution 3, and like the metal-air battery 30 shown in FIG. The two air electrodes 9 may have an electrode pair provided so as to sandwich one metal electrode 5.
The cell 4 may include an electrolytic solution tank 2 or an electrolytic solution chamber, a metal electrode 5 provided in the electrolytic solution tank 2 or the electrolytic solution chamber and serving as an anode, and an air electrode 9 serving as a cathode. .

3. Cell Assembly The cell assembly has a stack structure in which a plurality of cells 4 are stacked. In the cell assembly, a plurality of cells 4 may be provided in one electrolytic solution tank 2, and each cell 4 may have the electrolytic solution tank 2 or the electrolytic solution chamber. The number of cells constituting the cell assembly is not particularly limited, and the number of cells may be determined according to the required power generation capacity. For example, the metal-air battery 30 shown in FIG. 1 has four cells 4a to 4d.
In addition, when the plurality of cells 4 constituting the cell assembly each have the electrolytic solution tank 2, the electrolytic solution tank 2 included in each cell 4 may be provided in the common housing 1, and each cell 4 is disposed in the housing. 1, and the electrolytic solution tank 2 may be provided in the housing 1.
Note that two or three cells 4 may be provided in one casing 1 and a plurality of such casings 1 may be combined to form a cell aggregate.
The electrode pairs of the plurality of cells 4 included in the cell assembly may be connected in series or in parallel. For example, in the metal-air battery 30 shown in FIG. 1, electrode pairs included in four cells 4a to 4d are connected in series.

4). Electrolytic Solution, Gelling Agent, Gel Layer, Electrolytic Solution Tank The electrolytic solution 3 is a liquid having ionic conductivity by dissolving an electrolyte in a solvent. The electrolytic solution 3 is stored in the electrolytic solution tank 2 or circulates in the electrolytic solution tank 2. The type of the electrolytic solution 3 is different depending on the type of the electrode active material contained in the metal electrode 5, but may be an electrolytic solution (aqueous electrolyte solution) using a water solvent.
For example, in the case of a zinc-air battery, an aluminum-air battery, or an iron-air battery, an alkaline aqueous solution such as an aqueous sodium hydroxide solution or an aqueous potassium hydroxide solution can be used as the electrolytic solution. An aqueous sodium chloride solution can be used.

The gel layer 13 is preferably provided between the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the air electrode 9 facing the gel layer 13.
The gel layer 13 is a layer made of a polymer hydrogel containing an aqueous dispersion medium. Moreover, the gel layer 13 contains a gelling agent as a dispersoid. Examples of the aqueous dispersion medium include an aqueous electrolyte solution and water using a water solvent. The gel layer 13 may be in the form of a film or a liquid having a high viscosity.
Further, when the gel layer 13 is a layer made of a polymer hydrogel containing an aqueous dispersion medium containing an aqueous electrolyte solution, the gel layer 13 can contain the same type of electrolyte as the electrolytic solution 3 accommodated in the electrolytic solution tank 2. Thus, the gel layer 13 can have ionic conductivity, and hydroxide ions moving between the anode and the cathode can conduct the ionic conduction in the gel layer 13. Note that the conductivity of hydroxide ions is as high as that of the non-gelled electrolyte solution 3, and a high output can be obtained.

The gelling agent may be contained in the first main surface side of the air electrode 9 facing the electrolytic solution 3 accommodated in the electrolytic solution tank 2 or in the air electrode catalyst layer. In addition, the gel layer 13 may be disposed on the liquid surface of the electrolytic solution 3 in the precipitation tank 18 and the electrolytic tank 20 provided so that the electrolytic solution in the electrolytic solution tank 2 flows in.
The gel layer 13 can be formed, for example, by adding a gelling agent to the electrolytic solution 3 or water. Since the electrolyte solution 3 and water are taken into the three-dimensional network structure by the gelling agent, the gel layer 13 has high water retention. Because of this high water retention, transpiration of the electrolyte and water taken into the gel layer 13 can be kept low, and loss of the electrolyte 3 and water can be reduced.
Moreover, in this embodiment, since the electrolyte solution 3 in the electrolyte solution tank 2 is in contact with the outside air (air) through the gel layer 13, it suppresses deterioration due to transpiration and moisture absorption of the electrolyte solution 3 and reaction with carbon dioxide. And the change in the concentration of the electrolytic solution can be suppressed. In particular, if the concentration of the electrolyte solution around the metal electrode 5 changes, it greatly affects the zinc dissolution reaction and amount, which is not preferable in terms of output stability of the metal-air battery 30. The presence of the gel layer 13 stabilizes the concentration of the electrolytic solution 3 in the electrolytic solution tank 2 and improves the output stability of the metal-air battery 30. Further, the vapor of the electrolytic solution 3 becomes alkaline vapor or sodium chloride-containing vapor and may cause corrosion of other components such as electrical contacts. However, the gel layer 13 prevents other components from evaporating. Corrosion of can be suppressed. Furthermore, since the transpiration of the electrolytic solution 3 can be kept low, the frequency of replenishment of the electrolytic solution 3 can be reduced, and maintenance is easy.

As the gelling agent, a conventionally known water-absorbing polymer can be used, and a material excellent in alkali resistance is preferably used. Examples of the water-absorbing polymer include cross-linked polyacrylate and 2-acrylamido-2-methylpropanesulfonic acid having a sulfo group as a hydrophilic group. Moreover, although the kind of polyacrylate is not specifically limited, For example, polyacrylic acid sodium, polyacrylic acid potassium, polyacrylic acid calcium, and polyacrylic acid magnesium can be mentioned.
Examples of the water-absorbing polymer include starch-based acrylonitrile graft copolymers, acrylic acid graft copolymers, acrylamide graft copolymers, cellulose-based acrylonitrile graft copolymers, carboxymethyl cellulose crosslinked products, Sugar-based hyaluronic acid, polyvinyl alcohol-based polyvinyl alcohol cross-linked product, polyvinyl alcohol water-absorbing gel freeze / thaw elastomer, acrylic acid-based acrylic acid / sodium vinyl alcohol copolymer, cross-linked sodium polyacrylate, acrylamide-based N-substituted acrylamide cross-linked products can be used. These water-absorbing polymers can reduce the amount of water absorption by increasing the crosslinking density, and can be adjusted as appropriate. A crosslinking agent, a polymerization initiator, or the like may be used to adjust the crosslinking density. Examples of the crosslinking agent include N, N 'methylene bisacrylamide and ethylene glycol dimethacrylate, and the polymerization initiator is azobisisobutyronitrile (AIBN), benzoyl peroxide, and persulfate represented by potassium peroxodisulfate. A salt can be illustrated. Furthermore, in order to increase the crosslinking density, hydrogen bonds, ionic bonds, and coordinate bonds between the water-absorbing polymers may be used. For example, if a calcium chloride solution having multivalent ions is used, the carboxyl group of the water-absorbing polymer can be ionically bonded to increase the crosslinking density.

Moreover, in the case of the said bridge | crosslinking-type potassium polyacrylate, it takes in the electrolyte solution from several hundred to about 1000 times the own weight, and gelatinizes. Further, as will be described later, the gel layer 13 can be formed thin or formed into a film, so that the amount of potassium polyacrylate can be small, and the cost can be reduced. Moreover, when using alkaline aqueous solution for the electrolyte solution 3, since the polyacrylic acid potassium is excellent in alkali resistance, material deterioration is so small that it can be disregarded, and even if the gel layer 13 needs to be replaced, the frequency can be reduced. .
For example, a gelling agent is added to the electrolytic solution 3 or water stored in the external container, the electrolytic solution 3 or water in the external container is gelled to form a gel layer 13, and the formed gel layer 13 is used as a solution of the electrolytic solution 3. It can arrange | position on a surface, the air electrode 9, etc.
In addition, when water is used for the aqueous dispersion of the gel layer 13, the water is not limited to pure water, and may include an evaporation inhibitor and the like, and is not particularly limited as long as it does not react with the electrolytic solution.

Further, for example, the gel layer 13 may be formed by applying a gelling agent on the air electrode 9 or the like, and spraying an electrolytic solution or water thereon by spraying or the like. By doing in this way, the gel layer 13 can be formed thinly or can be made into a film form.
Further, for example, after adding a gelling agent to the electrolytic solution stored in the external container, the gelled electrolytic solution is applied on the porous body 32 or the air electrode 9, and the lower side of the porous body 32 or the air electrode 9. The applied gelled electrolytic solution can be moved into the porous body 32 or the air electrode 9 by being sucked from. Thus, the gel layer 13 can be disposed in the porous body 32 or the air electrode 9.
In addition, after the gel layer 13 is formed from the gelling agent and water or an electrolytic solution, the bubbles in the gel layer 13 may be removed by performing a defoaming process by a vacuum process or the like. This is because if the bubbles remain, the resistance increases due to an increase in the conduction distance of hydroxide ions conducted between the anode and the cathode. Further, after the gel layer 13 is placed on the air electrode 9 or the like, the laminate may be pressed. Since the gel layer 13 has adhesiveness, the air electrode 9 and the like can be entangled well, and peeling of the gel layer 13 can be suppressed. Further, since the gel layer 13 is entangled with the air electrode 9, the contact area between the air electrode 9 and the air electrode catalyst is increased, and the ion conduction path is easily connected, so that high output is easily obtained. Further, since the integrated product of the gel layer 13 and the air electrode 9 is obtained, the number of parts is reduced, and the cost can be reduced.

The electrolytic solution tank 2 is an electrolytic cell that stores or distributes the electrolytic solution 3 and has corrosion resistance to the electrolytic solution. Moreover, the electrolytic solution tank 2 can have an electrolytic solution chamber.
The electrolytic solution tank 2 or the electrolytic solution chamber has a structure in which the metal electrode 5 can be installed so that it can be taken out. The electrolyte bath 2 can be provided in the metal-air battery main body. Moreover, the electrolytic solution tank 2 may have a plurality of electrolytic solution chambers.

The metal-air battery 30 may have a mechanism for causing the electrolytic solution 3 in the electrolytic solution tank 2 to flow. As a mechanism for causing the electrolytic solution 3 to flow, for example, the electrolytic solution 3 may be circulated using the pump 25 and the electrolytic solution flow channel 26 to cause the electrolytic solution 3 in the electrolytic solution tank 2 to flow. As a result, the fresh electrolyte 3 can be supplied around the metal electrode 5, so that the battery characteristics can be improved and the discharge capacity can be increased.
Moreover, the metal air battery 30 may be provided with a movable part that can physically move the electrolyte 3 in the electrolyte bath 2 such as a stirrer and a vibrator.
Further, since the electrolyte 3 to be fluidized is not gelled and has high fluidity, even when a porous electrode (for example, an electrode prepared by sintering metal powder) is used as the metal electrode 5, the electrolyte 3 Can penetrate into the pores of the porous electrode. For this reason, it becomes possible to discharge immediately after inserting the metal electrode 5 into the electrolytic solution tank 2. Moreover, since the electrolyte 3 to be flowed has a low viscosity, it is possible to prevent a part of the metal electrode 5 from dropping off when the metal electrode 5 is inserted into or extracted from the electrolyte bath 2.

For example, in the metal-air battery 30 shown in FIG. 1, the electrolytic solution 3 in the precipitation tank 18 is supplied to the cells 4a to 4d by the pump 25, and discharged from the discharge ports 15a to 15d of the cells 4a to 4d. An electrolyte channel 26, a precipitation tank 18, and a pump 25 are provided so that 3 flows into the precipitation tank 18. By circulating the electrolyte 3 with such a configuration, the precipitate 17 can be accumulated in the precipitation tank 18, and accumulation of the precipitate 17 in the electrolyte tank 2 can be suppressed. This can prevent the deposit 17 from adversely affecting the battery reaction. Moreover, since the deposit 17 can be collected in the sedimentation tank 18, it is possible to continue the discharge by the metal-air battery 30 during the collection operation.
Here, in FIG. 1, the electrolyte solution 3 communicates between the cells 4a to 4d via the discharge ports 15a to 15d, but the method of circulating the electrolyte solution 3 is not limited to this. For example, a liquid distributor may be provided above the cells 4a to 4d, and the electrolytic solution 3 may be supplied to each cell 4 so that the liquid droplets are dropped from the liquid distributor. Similarly, the electrolytic solution 3 supplied to each cell 4 is caused to flow into the sedimentation tank 18 so as to drips, and the electrolytic solution is circulated by sending the electrolytic solution 3 to the liquid distributor using the pump 25. May be performed. Thus, by supplying the electrolyte solution 3 to each cell 4 from a liquid distribution part, since the liquid junction (short circuit by electrolyte solution) of each cell 4 can be prevented, an output can be improved.
For example, like the metal-air battery 30 shown in FIG. 7, the gel layer 13e may be disposed on the liquid surface of the electrolytic solution 3 in the precipitation tank 18. As a result, transpiration and moisture absorption of the electrolytic solution 3 and deterioration due to reaction with carbon dioxide can be suppressed, and changes in the electrolyte concentration of the electrolytic solution 3 can be suppressed.

Further, the metal-air battery 30 may be provided so that the electrolyte 3 in the electrolyte bath 2 flows into a means for reducing the metal-containing ion concentration.
Means for reducing the concentration of the metal-containing ion is, for example, the electrolytic cell 20 or the precipitation promoting part. The electrolytic cell 20 can have an electrode pair of electrodes for electrolysis 21 like the metal-air battery 30 shown in FIG. When a voltage is applied to the electrode pair, a precipitation reaction of a metal, a metal compound, or the like can be caused electrochemically, and the metal-containing ion concentration of the electrolytic solution can be reduced.
Further, the precipitation promoting portion is a portion having crystal nucleus particles made of the same kind of material as the precipitate 17, for example. When the electrolytic solution 3 is allowed to flow into such a precipitation promoting part, the precipitate 17 can be crystal-grown on the surface of the crystal nucleus particles, and the metal-containing ion concentration of the electrolytic solution 3 can be reduced.
Thus, by providing means for reducing the concentration of the metal-containing ions, it is possible to repeatedly discharge the metal-air battery 30 without replacing the electrolytic solution 3.

The material of the housing 1 constituting the electrolytic solution tank 2 is not particularly limited as long as the material has corrosion resistance to the electrolytic solution. For example, polyvinyl chloride (PVC), polyvinyl alcohol (PVA), polyvinyl acetate, ABS resin, vinylidene chloride, polyacetal, polyethylene, polypropylene, polyisobutylene, fluorine resin, epoxy resin, etc.

5. Air electrode The air electrode 9 is an electrode which has the air electrode catalyst layer 7 containing an air electrode catalyst, and serves as a cathode. Further, the air electrode 9 may include a porous gas diffusion layer 8 and a porous air electrode catalyst layer 7 provided on the gas diffusion layer 8. Further, the gel layer 13 may be disposed by including a gelling agent in the pores of the air electrode 9.
In the air electrode 9, water supplied from the electrolytic solution 3 and the like, oxygen gas supplied from the atmosphere, and electrons react on the air electrode catalyst to generate hydroxide ions (OH ⁻ ) (cathode reaction). That is, the cathode reaction proceeds at the three-phase interface of the air electrode 9.
The air electrode 9 is provided so that oxygen gas contained in the atmosphere can diffuse into the air electrode 9. For example, the air electrode 9 can be provided so that at least a part of the surface of the air electrode 9 is exposed to the atmosphere. In the metal-air battery 30 shown in FIGS. 1 and 2, a plurality of air flow paths 12 are provided in the housing 1, and oxygen gas contained in the atmosphere can diffuse into the air electrode 9 through the air flow paths 12. Note that water may be supplied to the air electrode 9 through the air flow path 12.
For example, the air electrode 9 has a sheet shape, and the first main surface of the air electrode 9 is on the side of the electrolyte solution 3 accommodated in the electrolyte solution tank 2 in a part of the wall portion of the electrolyte solution tank 2. The air electrode 9 can be disposed so that the surface is on the atmosphere or air flow path side. As a result, water contained in the electrolytic solution 3 accommodated in the electrolytic solution tank 2 can be supplied to the air electrode catalyst layer 7 from the first main surface side, and oxygen gas in the atmosphere is supplied from the second main surface side to the air. It can be supplied to the polar catalyst.

The air electrode catalyst layer 7 preferably includes, for example, an electron conductive material, and may include a conductive porous carrier (electron conductive material) and an air electrode catalyst supported on the porous carrier. This makes it possible to form a three-phase interface in which oxygen gas, water, and electrons coexist on the air electrode catalyst, thereby allowing the cathode reaction to proceed. The air electrode catalyst layer 7 may contain a binder. Further, the porous carrier contained in the air electrode catalyst layer 7 may hold a gelling agent in the pores, and the gel layer 13 may be disposed. The air electrode catalyst layer 7 may contain a gelling agent in advance. The gelling agent absorbs the electrolytic solution 3 penetrating into the air electrode catalyst layer 7 and forms the gel layer 13, so that leakage of the electrolytic solution 3 through the air electrode 9 can be prevented. The air electrode catalyst layer 7 may contain a water repellent resin. Thereby, leakage of the electrolyte solution 3 through the air electrode 9 can be suppressed.

The content of the water-absorbing polymer in the air electrode catalyst layer 7 is not particularly limited, but is preferably 3 wt% or more and 70 wt% or less, more preferably 5 wt% or more and 30 wt% or less. . When the content of the water-absorbing polymer in the air electrode catalyst layer 7 is less than 3 wt%, the gelling agent or gel formed by the water-absorbing polymer absorbing the electrolyte or water is the air electrode catalyst layer 7. There is a possibility that the pores of the porous structure cannot be sufficiently filled, and the electrolytic solution 3 may leak to the outside through the pores of the air electrode catalyst layer 7. Moreover, since the gel cannot sufficiently cover the air electrode catalyst, the three-phase interface is not sufficiently formed, and the discharge characteristics may be deteriorated. On the other hand, when the content of the water-absorbing polymer in the air electrode catalyst layer 7 exceeds 70 wt%, the voids 25 (oxygen gas diffusion paths) are not sufficiently ensured in the pores of the porous structure of the air electrode catalyst layer 7, so that the discharge There is a possibility that the characteristics are significantly deteriorated.
The content of the water-absorbing polymer in the air electrode catalyst layer 7 is, for example, the content (wt%) = {A / (A + B)} × 100 (A: the weight of the water-absorbing polymer in the air electrode catalyst layer 7). B: Weight of the air electrode catalyst and the electron conductive material in the air electrode catalyst layer 7).

The air electrode 9 composed of the air electrode catalyst layer 7 and the gas diffusion layer 8 is produced by applying a porous carrier carrying the air electrode catalyst to the conductive porous substrate (gas diffusion layer 8). May be. For example, the air electrode 9 can be produced by applying carbon carrying an air electrode catalyst to carbon paper or carbon felt. The gas diffusion layer 8 may function as an air electrode current collector. The gas diffusion layer 8 may be composed of carbon fibers and a microporous layer made of carbon black and a water repellent polymer. The water repellent polymer is, for example, polytetrafluoroethylene (PTFE). This water-repellent polymer is provided to prevent leakage of the electrolyte solution 3 and has a gas-liquid separation function. That is, the electrolytic solution 3 is prevented from leaking from the electrolytic solution tank 2, and the supply of oxygen gas to the air electrode catalyst layer 7 is not hindered.
The thickness of the air electrode 9 can be, for example, not less than 300 μm and not more than 3 mm.
Further, the air electrode 9 may be composed of only the air electrode catalyst layer 7. In addition, when the air electrode 9 is comprised only from the air electrode catalyst layer 7, the air electrode catalyst layer 7 is directly connected with the air electrode terminal 40 or an external wiring. The air electrode 9 may have a structure in which the air electrode catalyst layer 7 and the air electrode current collector 10 are laminated. In this case, the air electrode catalyst layer 7 may be disposed on the first main surface side, the air electrode current collector 10 may be disposed on the second main surface side, and the air electrode current collector 10 may be disposed on the first main surface side. The air electrode catalyst layer 7 may be disposed on the second main surface side. Further, the air electrode 9 is preferably formed of a porous body on the first main surface side.
Further, the air electrode 9 can be electrically connected to the air electrode terminal 40. Thereby, the electric charge generated in the air electrode catalyst layer 7 can be taken out to the external circuit.

The metal-air battery 30 includes an air electrode current collector 10 that collects charges generated in the air electrode catalyst layer 7. As a result, the charges generated in the air electrode catalyst layer 7 can be taken out to an external circuit efficiently, that is, with low resistance. The material of the air electrode current collector 10 is not particularly limited as long as it has corrosion resistance with respect to the electrolytic solution 3, and examples thereof include nickel, gold, silver, copper, and stainless steel. Further, the air electrode current collector 10 may be a conductive base material subjected to nickel plating, gold plating, silver plating, or copper plating. For this conductive substrate, iron, nickel, stainless steel, or the like can be used.
Further, the shape of the air electrode current collector 10 may be a shape having a plurality of openings such as a plate shape, a mesh shape, and a punching metal. The plurality of openings of the air electrode current collector 10 may be open to the atmosphere. Thereby, oxygen gas in the atmosphere can be supplied to the air electrode 9 through the opening.
In addition, as a method of joining the air electrode current collector 10 to the porous carrier or the conductive porous substrate (gas diffusion layer 8), a method of pressure bonding by screwing through a frame, or a conductive adhesive And the like.

The air electrode 9 included in one cell may be provided only on one side of the metal electrode 5, or may be provided on both sides of the metal electrode 5 as shown in FIG.
Examples of the porous carrier contained in the air electrode catalyst layer 7 include carbon black such as acetylene black, furnace black, channel black and ketjen black, and conductive carbon particles such as graphite and activated carbon. In addition, carbon fibers such as vapor grown carbon fiber (VGCF), carbon nanotube, carbon nanowire, and the like can be used.
Examples of the air electrode catalyst include fine particles made of platinum, iron, cobalt, nickel, palladium, silver, ruthenium, iridium, molybdenum, manganese, lanthanum, these metal compounds, and alloys containing two or more of these metals. Can be mentioned. This alloy is preferably an alloy containing at least two of platinum, iron, cobalt, and nickel. For example, platinum-iron alloy, platinum-cobalt alloy, iron-cobalt alloy, cobalt-nickel alloy, iron-nickel alloy And iron-cobalt-nickel alloy.

The air electrode catalyst may be in the form of particles or may be supported on an electron conductive material. In particular, by supporting the air electrode catalyst on the electron conductive material, the surface area of the air electrode catalyst can be increased and a large number of three-phase interfaces can be formed. In addition, by supporting the air electrode catalyst on the electron conductive material, the amount of the air electrode catalyst necessary for manufacturing the air electrode 9 can be reduced, and the manufacturing cost of the metal-air battery 30 can be reduced. Furthermore, by carrying the air electrode catalyst on the electron conductive material, the charge generated by the cathode reaction in the air electrode catalyst can be collected efficiently, and the discharge characteristics of the metal-air battery 30 can be enhanced. The electron conductive material is, for example, Pt-supported carbon particles.
The binder contained in the air electrode catalyst layer 7 is, for example, polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF).
Further, the porous carrier contained in the air electrode catalyst layer 7 may be subjected to a surface treatment so that a cationic group exists as a fixed ion on the surface thereof. As a result, hydroxide ions can be conducted on the surface of the porous carrier, so that the hydroxide ions generated on the air electrode catalyst can easily move.
The air electrode catalyst layer 7 may have an anion exchange resin held in the pores of the porous carrier. Thereby, since hydroxide ions can be conducted through the anion exchange resin, the hydroxide ions generated on the air electrode catalyst are easily moved.

The air electrode catalyst layer 7 may be provided so as to be in contact with the electrolytic solution 3 in the electrolytic solution tank 2. Thus, hydroxide ions generated in the air electrode catalyst layer 7 can easily move to the electrolyte solution 3. Further, water necessary for the electrode reaction in the air electrode catalyst layer 7 is easily supplied from the electrolytic solution 3 to the air electrode catalyst layer 7.
If the air electrode catalyst layer 7 is provided so as to be in contact with the electrolytic solution 3 in the electrolytic solution tank 2, the used active material may adhere to and adhere to the air electrode 9 in some cases. In this case, since the used active material has low electrical conductivity, battery resistance is increased, or air diffusion is suppressed by filling the pores of the porous structure of the air electrode 9, so that battery characteristics are deteriorated. There is. In addition, the used active material (precipitate 17) adhering to the air electrode 9 precipitates by nucleation and crystal growth in the electrolyte solution in the vicinity of the metal electrode 5 having a high metal-containing ion concentration. Is considered to adhere to the air electrode 9 having a large surface area.

A gel layer 13 may be provided between the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the air electrode 9. The gel layer 13 may be provided on the air electrode 9. Moreover, this gel layer 13 may consist of what gelatinized electrolyte solution. This can suppress an increase in ion conduction resistance between the anode and the cathode. Further, the gel layer 13 can be provided so as to partition the electrolyte solution 3 in the electrolyte solution tank 2 and the air electrode catalyst layer 7. By providing such a gel layer 13, it is possible to prevent the electrolytic solution 3 in the electrolytic solution tank 2 from directly flowing into the pores of the air electrode 9, and the electrolytic solution through the pores of the air electrode 9. 3 leakage can be suppressed. Moreover, since the rate at which the electrolytic solution 3 permeates the gel layer 13 is slow, an appropriate amount of water can be supplied to the air electrode 9. Further, by providing the gel layer 13, it is possible to prevent the electrolytic solution 3 in the electrolytic solution tank 2 from directly flowing into the air electrode 9, so that a precipitate 17 such as a metal oxide adheres to the air electrode 9. Can be prevented. Further, since the conductivity of the metal-containing ions in the gel layer 13 is also sufficiently low, it is possible to suppress the metal oxide from being deposited on the air electrode 9. Thereby, battery characteristics can be maintained.
Further, hydrogen gas may be generated in the metal electrode 5 due to self-corrosion. When this hydrogen gas reacts at the air electrode 9, the battery performance deteriorates or the output stability is impaired, but the hydrogen gas is covered at the air electrode 9 by covering the air electrode 9 with the gel layer 13 that is difficult for hydrogen gas to permeate. Reaction can be prevented.
For example, the gel layer 13 is provided so as to cover the air electrode catalyst layer 7 between the air electrode catalyst layer 7 and the electrolyte solution 3 accommodated in the electrolyte solution tank 3 as in the metal-air battery 30 shown in FIG. be able to.

The first main surface of the air electrode 9 facing the electrolytic solution 3 accommodated in the electrolytic solution tank 2 may be formed of the porous body 32, and the gelling agent may be included in the pores of the porous body 32. Since the gelling agent is contained in the porous body 32, the gelling agent and water form the gel layer 13 when the electrolytic solution 3 penetrates into the air electrode 9. The gel layer 13 may be composed of a polymer hydrogel layer containing water of an electrolyte aqueous solution. This can suppress an increase in ion conduction resistance between the anode and the cathode. Further, the porous body 32 in which the gel layer 13 is provided in the pores can be provided so as to partition the electrolytic solution 3 in the electrolytic solution tank 2 and the air electrode catalyst layer 7. By providing the porous body 32 in which the gel layer 13 is formed in such pores, the electrolyte solution 3 in the electrolyte bath 2 can be prevented from flowing directly into the pores of the air electrode 9. The leakage of the electrolyte solution through the pores of the air electrode 9 can be suppressed. Moreover, since the water contained in the electrolytic solution 3 in the electrolytic solution tank 2 can be supplied to the air electrode 9 through the gel layer 13 in the pores, an appropriate amount of water is supplied to the air electrode 9. Can do. Furthermore, by providing the gel layer 13 in the pores of the porous body 32, it is possible to prevent the shape of the gel layer 13 from being deformed or peeled off due to the flow of the electrolytic solution 3 in the electrolytic solution tank 2. Can do. This can increase the effect of suppressing leakage of the electrolyte. In addition, by making the thickness of the porous body 32 substantially constant, the distance between the electrolytic solution 3 accommodated in the electrolytic solution tank 2 and the air electrode 9 can be made substantially constant. Thereby, the effect which suppresses the leakage of the electrolyte solution 3 can be made high. Further, since the ion conduction resistance of the gel layer 13 can be made substantially uniform, the reaction rate of the cathode reaction on the electrode surface of the air electrode 9 can be made substantially uniform, and the output of the metal-air battery 30 Characteristics can be improved.

The porous body 32 in which the gel layer 13 is formed in the pores is, for example, the electrolytic solution 3 accommodated in the air electrode catalyst layer 7 and the electrolytic solution tank 2 as in the metal-air battery 30 shown in FIG. Can be provided so as to cover the air electrode catalyst layer 7. FIG. 3B is a schematic cross-sectional view of the porous body 32 included in the metal-air battery 30 shown in FIG. The gel layer 13 is provided in the pores of the porous body 32 as shown in FIG.
As a manufacturing method, first, an electrolytic solution to which a gelling agent is added is applied to the porous material to be the porous body 32, and the gelled electrolytic solution is sucked from the surface opposite to the coating surface to thereby remove the gelled electrolytic solution. Introduce into the pores. And the porous body 32 in which the gel layer 13 was formed in the pore can be formed by installing this porous material on the air electrode catalyst layer 7. Alternatively, a gelling agent is kneaded into the pores of the porous material to be the porous body 32 using a bar coater or the like, and this is placed on the air electrode catalyst layer 7. By doing in this way, when supplying electrolyte solution 3 to electrolyte solution tank 2, gelation of electrolyte solution 3 occurs in a pore, and porous body 32 in which gel layer 13 was formed can be formed. it can.

The porous body 32 is not particularly limited as long as it is porous and has pores. For example, the porous body 32 is composed of a porous material, a foam material, a woven fabric, a nonwoven fabric, a mesh material, or the like.
The material of the porous body 32 is not particularly limited as long as it has corrosion resistance to an electrolytic solution such as an alkali-resistant material. For example, resin materials such as polyethylene, polypropylene, polyvinyl alcohol, and polyolefin, ceramic materials, zeolite, activated carbon, For example, foam metal such as nickel and stainless steel, metal mesh, and the like. The material of the porous body 32 can be an insulating material.
The porous body 32 preferably has a high porosity. Thereby, the volume of the gel layer 13 that the porous body 32 can hold can be increased. Further, the thickness of the porous body 32 is preferably 30 μm or more.

The second porous body 34 may be provided on the first porous body 32 in which the gel layer 13 is formed in the pores. For example, the second porous body 34 sandwiches the first porous body 32 between the second porous body 34 and the air electrode 9 like the metal-air battery 30 shown in FIG. Can be provided. FIG. 4B is a schematic cross-sectional view of the first porous body 32 included in the metal-air battery 30 shown in FIG.
By providing the second porous body 34, the first porous body 32 and the air electrode 9 can be sandwiched between the second porous body 34 and the air electrode current collector 10. The retention performance of the gel layer 13 by the mass 32 can be enhanced. In addition, since the contact between the air electrode 9 and the air electrode current collector 10 is improved, the electrical resistance is reduced and the battery performance can be improved. In order to increase the effect of this sandwiching, when the air electrode current collector 10 and the second porous body 34 have a strength that is difficult to bend compared to the air electrode 9 and the first porous body 32, preferable.
The second porous body 34 can have a plurality of openings. Thus, the gel layer 13 in the porous body 32 can come into contact with the electrolytic solution 3, and water can be supplied to the air electrode 9 through the gel layer 13. Further, the gel layer 13 may be provided in the plurality of openings of the second porous body 34. Furthermore, the gel layer 13 may be disposed so as to be sandwiched between the first porous body 32 and the second porous body 34. This makes it possible to uniformly grow the formation of the gel layer 13 while maintaining the ionic conductivity between the air electrode 9 and the metal electrode 5.

The first porous body 32 or the second porous body 34 is preferably a film having a porous structure. For example, resin materials such as polyethylene, polypropylene, polyvinyl alcohol, polyolefin, and polyamide, ceramic materials, and zeolites , Activated carbon, Ni nickel and stainless steel, kraft paper, synthetic pulp paper, cellophane, glass fiber and so on.
The form of the 1st porous body 32 or the 2nd porous body 34 is a nonwoven fabric, a woven fabric, paper, a porous material, a foam metal, a metal mesh etc., for example.
The average pore diameter of the first porous body 32 and the second porous body 34 is preferably 10 μm or less, and more preferably 5 μm or less. As a result, the negative electrode reaction product (precipitate 24 shown in FIG. 6) in the electrolytic solution tank 2 passes through the first porous body 32 or the second porous body 34 and adheres to the air electrode 9. The long-term stability of the discharge characteristics of the metal-air battery 30 can be improved.

The second porous body 34 may have a function as a charging electrode. In this case, a voltage is applied between the metal electrode 5 and the second porous body 34 to deposit a metal, which is an electrode active material, on the metal electrode 5 to be charged. In this case, the second porous body 34 is made of a conductive material such as a metal plate.
When the metal-air battery 30 is used as a secondary battery, it is conceivable that a voltage is applied between the metal electrode 5 and the air electrode 9 to deposit a metal as an electrode active material on the metal electrode 5. However, when the air electrode 9 is used for both discharging and charging, the deterioration rate of the air electrode 9 is fast. For this reason, if the 2nd porous body 34 has a function as an electrode for charge, the deterioration rate of the air electrode 9 can be slowed and the lifetime characteristic of the metal air battery 30 can be improved. In this case, the material of the porous body 32 can be an insulating material. As a result, leakage current can be prevented from flowing during charging.
Moreover, when using the metal air battery 30 as a secondary battery, it is preferable to circulate the electrolyte solution 3 in the electrolyte tank 2 during charging. Thereby, formation of dendrites can be suppressed and the long-term reliability of the metal-air battery 30 can be improved. Further, when dendrite is formed and the metal electrode 5 deteriorates, the deteriorated metal electrode 5 can be replaced with a new metal electrode 5.
Further, even if dentlite is formed from the metal electrode 5, it is considered that the gel layer 13 becomes a filter, and there is no possibility of being short-circuited with the air electrode 9 through the second porous body 34.

The gel layer 13 may be provided in the pores of the air electrode 9. Further, the gel layer 13 may be provided in the pores of the air electrode catalyst layer 7. This gel layer 13 may consist of what gelatinized electrolyte solution. This can suppress an increase in ion conduction resistance between the anode and the cathode. By providing the gel layer 13 in the pores of the air electrode 9, it is possible to prevent the electrolyte solution 3 in the electrolytic solution tank 2 from directly flowing into the pores of the air electrode 9. It is possible to suppress leakage of the electrolytic solution 3 via the. In addition, since water contained in the electrolyte 3 in the electrolyte bath 2 can be supplied to the air electrode 9 through the gel layer 13 in the pores, many three-phase interfaces formed in the air electrode 9 are formed. The discharge characteristics of the metal-air battery 30 can be improved. Moreover, since the air electrode 9 can hold | maintain the gel layer 13, it can suppress that the shape of the gel layer 13 deform | transforms with the flow of the electrolyte solution in the electrolyte solution tank 2, or peels. This can increase the effect of suppressing leakage of the electrolyte. Further, by providing the gel layer 13 in the pores of the air electrode 9, it is possible to prevent the electrode active material contained in the electrolytic solution 3 and the extremely fine particles of the precipitate 17 from adhering to the air electrode catalyst layer 7.

The metal-air battery 30 having the air electrode 9 in which the gel layer 13 is formed in the pores can be provided, for example, like the metal-air battery 30 shown in FIGS. FIG. 5B is a schematic cross-sectional view of the air electrode catalyst layer 7 included in the metal-air battery 30 shown in FIG. The gel layer 13 is provided in the pores of the air electrode catalyst layer 7 as shown in FIG.
As a manufacturing method, for example, first, an electrolytic solution to which a gelling agent is added is applied on the surface of the air electrode 9 on which the gas diffusion layer 8 and the air electrode catalyst layer 7 are laminated, on the air electrode catalyst layer 7 side, The gelled electrolyte is introduced into the pores of the air electrode catalyst layer 7 by suction from the surface opposite to the coated surface. The air electrode 9 is installed on the side wall of the electrolytic solution tank 2. Alternatively, a gelling agent is kneaded into the pores of the air electrode catalyst layer 7 using a bar coater or the like, and this is installed on the side wall of the electrolytic solution tank 2. By doing in this way, when supplying the electrolyte solution 3 to the electrolyte tank 2, gelation of the electrolyte solution 3 occurs in the pores, and the air electrode catalyst layer 7 in which the gel layer 13 is formed is formed. Can do.

Further, as shown in FIG. 6, the air electrode 9 may have a structure in which an air electrode catalyst layer 7, an air electrode current collector 10, and a water repellent layer 6 are laminated. In this case, the air electrode catalyst layer 7 is disposed on the first main surface side, the water repellent layer 6 is disposed on the second main surface side, and the air electrode current collector 10 is disposed on the air electrode catalyst layer 7 and the water repellent layer 6. It may be arranged between. On the other hand, the air catalyst layer 7 is preferably provided between the air electrode current collector 10 and the water repellent layer 6, and improves the bondability between the water repellent layer 6 and the air electrode current collector 10. The adhesion of the laminated structure of the air electrode 9 can be improved.
The water repellent layer 6 has porosity and a hydrophobic surface. The water repellent layer 6 is provided on the air side or the air flow path side of the air electrode catalyst layer 7. According to such a configuration, oxygen gas can be supplied to the air electrode catalyst layer 7 through the pores of the water repellent layer 6.
Moreover, by disposing the gelling agent in the pores of the air electrode catalyst layer 7, leakage of the electrolyte solution 3 through the pores of the air electrode catalyst layer 7 can be suppressed. When the electrolytic solution 3 oozes from the gel, the water repellent layer 6 can prevent the electrolytic solution 3 from leaking. As a result, the safety of the metal-air battery can be improved.
The water repellent layer 6 may be omitted. For example, the air electrode 9 may be composed of the air electrode catalyst layer 7 and the air electrode current collector 10. Such an air electrode 9 can be formed by pressure-bonding the air electrode catalyst layer 7 and the air electrode current collector 10. By omitting the water repellent layer 6, the manufacturing cost of the metal-air battery 30 can be reduced. Further, by omitting the water repellent layer 6, the metal-air battery 30 can be thinned.

The water repellent layer 6 can include, for example, an electron conductive material such as carbon black and a material having a hydrophobic surface such as a fluororesin. The water repellent layer 6 may not contain an electron conductive material. Further, the water repellent layer 6 may include an electron conductive material coated with a material having a hydrophobic surface.
As a material of the electron conductive substance constituting the water repellent layer 6, a material that can be used for the electron conductive substance contained in the air electrode catalyst layer 7 can be used.
Examples of substances having a hydrophobic surface include polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF), and perfluoro which is a fluorinated resin copolymer. Alkoxy fluororesin (PFA), tetrafluoroethylene / hexafluoropropylene copolymer (FEP), ethylene / tetrafluoroethylene copolymer (ETFE), ethylene / chlorotrifluoroethylene copolymer (ECTFE), etc. Fluorine resin; Fluorine resin such as polyvinylidene fluoride (PVDF) and polytetrafluoroethylene (PTFE); Acrylic resin; Polyolefin resin such as polyethylene and polypropylene; Polyester resin such as polyethylene terephthalate; Polyurethane resin; , And the like water-repellent silicone resin; de resin; polyacetal resin; polycarbonate resins, chlorinated resins such as polyvinyl chloride; polyether resins; polyphenylene-based resin.

The form of the porous water repellent layer 6 may be a particle aggregate, a foam made of the above polymer, a fiber bundle, a woven fiber, a non-woven fiber, or a combination thereof.
Specifically, the water-repellent layer 6 includes “NTF2026A-N06” and “NTF2122A-S06” manufactured by Nitto Denko Corporation, which are porous films made of polytetrafluoroethylene (TEMISH (registered trademark)). Can be used.
The porosity of the porous water repellent layer 6 is preferably 10% or more and 90% or less, and more preferably 20% or more and 80% or less. When the porosity of the water repellent layer 6 exceeds 90%, it is difficult to maintain the structure, and long-term stability may be impaired. On the other hand, when the porosity of the water repellent layer 6 is less than 10%, the diffusion of external air to the air electrode catalyst layer 7 may be hindered, and the discharge characteristics may be deteriorated. The porosity of the water-repellent layer 6 is determined by measuring the volume and weight of the water-repellent layer 6 to determine the specific gravity of the water-repellent layer 6.
Porosity (%) = [1- (specific gravity of water repellent layer / material specific gravity)] × 100
Can be calculated.

The film thickness of the water repellent layer 6 is not particularly limited, but is preferably 50 μm or more and 3 mm or less, and more preferably 100 μm or more and 2 mm or less. When the film thickness of the water repellent layer 6 is less than 50 μm, it is difficult to maintain the structure, and the water repellent layer 6 may peel from the air electrode current collector 10. On the other hand, when the film thickness of the water repellent layer 6 exceeds 3 mm, the diffusion of external air to the air electrode catalyst layer 7 is hindered, so that the discharge characteristics may be significantly lowered.
As a method for forming the water repellent layer 6, for example, an electron conductive substance and a fluororesin can be mixed and stirred, and the resulting mixture can be formed into a sheet by passing it through a pressure roller. Further, the water repellent layer 6 may be formed by screen printing, slurry coating method, hydrothermal synthesis method, CVD method or the like.

6). Metal electrode The metal electrode 5 is an electrode that serves as an anode, and includes a metal that is an electrode active material of the anode. Moreover, the metal electrode 5 is provided in the electrolyte solution tank 2 so that it can be taken out.
The metal electrode 5 may be, for example, a metal plate containing a metal that is an electrode active material. In addition, the metal electrode 5 may include, for example, a metal electrode current collector and an electrode active material layer provided on the metal electrode current collector.
Further, the metal electrode 5 or the electrode active material layer may be porous. Thereby, the reaction surface area can be increased, and the output characteristics of the metal-air battery 30 can be improved. Further, by increasing the reaction surface area, the applied current value per unit surface area can be reduced, and a passive film is hardly formed on the electrode surface. For this reason, it becomes easy to maintain the active surface of the metal electrode 5.
The porous electrode active material layer can be formed by, for example, applying a mixture of metal powder, which is an electrode active material, a conductive material, and a binder onto a metal electrode current collector and performing pressing. The conductive material can be preferably used to leave an electron conduction path even when a non-conductive film is formed on the surface layer of the metal powder that is the electrode active material and the conductivity is lowered, such as acetylene black, furnace black, channel Carbon black such as black and ketjen black, and conductive carbon particles such as graphite and activated carbon can be used. As the binder, polytetrafluoroethylene (PTFE) having excellent chemical resistance can be preferably used.

The electrode active material contained in the metal electrode 5 is a metal that generates a charge in the metal electrode 5 by an anodic reaction and dissolves in the electrolyte as metal-containing ions. For this reason, the electrode active material contained in the metal electrode 5 is gradually consumed as the anode reaction proceeds. When the electrode active material contained in the metal electrode 5 decreases, the charge generated in the metal electrode 5 decreases and the metal electrode 5 is used. By discharging the used metal electrode 5 from the electrolytic solution tank 2 and inserting a new metal electrode 5 into the electrolytic solution tank 2, the discharge by the metal-air battery 30 can be continued.
The charge generated in the metal electrode 5 is output to the outside as a discharge current and then used for the cathode reaction in the air electrode 9.
Further, when the metal electrode 5 is installed in the electrolytic solution, hydrogen gas may be generated due to self-corrosion.

When the gel layer 13 ′ is provided on the liquid surface of the electrolytic solution 3 accommodated in the electrolytic solution tank 2, the metal electrode 5 can be provided in contact with the gel layer 13 ′ on the liquid surface. Moreover, gel layer 13 'can be provided so that the liquid level of the electrolyte solution 3 accommodated in the electrolyte solution tank 2 may be covered. Thus, by providing the gel layer 13 ′ and the metal electrode 5, when the metal electrode 5 is extracted from the electrolytic solution tank 2, the electrolyte solution 3 attached to the surface of the used metal electrode 5 is removed from the gel layer 13 ′. Can be wiped off. As a result, the amount of the electrolytic solution adhering to the surface of the used metal electrode 5 taken out from the electrolytic solution tank 2 can be reduced, and the electrolytic solution can be prevented from dripping from the taken out metal electrode 5. it can. As a result, the electrolyte solution can be prevented from leaking to the outside when the metal electrode 5 is replaced, so that the electrolyte replenishment frequency can be reduced without substantially reducing the amount of the electrolyte solution 3 in the electrolyte bath 2. In addition, the safety of the metal-air battery 30 at the time of replacement work can be improved. Moreover, the safety | security of the conveyance operation | work of the collect | recovered used metal electrode 5 can also be improved. The gel layer 13 ′ may adhere to the metal electrode 5 in a small amount when the metal electrode 5 is replaced. However, when the gel layer 13 ′ is made of water gelled, it can be said that the safety is even higher.
Further, by reducing the amount of the electrolytic solution adhering to the surface of the used metal electrode 5, the corrosion of the recovered metal electrode 5 can be suppressed. Moreover, it can suppress that the collect | recovered metal electrode 5 becomes heavy, and can reduce conveyance expense.
Further, the gel layer 13 ′ can be provided so as to cover substantially all of the liquid surface of the accommodated electrolytic solution 3. Although hydrogen gas may be generated due to self-corrosion of the metal electrode 5, the hydrogen gas permeates through the gel layer 13 ′ over time, so that hydrogen gas is not accumulated in the electrolytic solution tank 2. It is done.
Further, the gel layer 13 ′ can be formed into a film shape. Accordingly, when the metal electrode 5 is extracted from the electrolytic solution tank 2 or inserted into the electrolytic solution tank 2, a part of the metal electrode 5 can be suppressed from being trapped by the gel layer 13 ′ and detached. .

Moreover, by providing the gel layer 13 'on the liquid surface of the electrolytic solution 3 in the electrolytic solution tank 2, it is possible to suppress the transpiration and moisture absorption of the electrolytic solution 3 and the deterioration due to the reaction with carbon dioxide. Loss and a change in the concentration of the electrolytic solution 3 can be suppressed. For example, a high-concentration KOH aqueous solution used for the electrolytic solution 3 absorbs moisture when the environmental humidity is high, but the gelled KOH aqueous solution (gel layer 13) has a small amount of moisture absorption. For this reason, by providing gel layer 13 'on the liquid level of the electrolyte solution 3 in the electrolyte tank 2, the moisture absorption of the electrolyte solution 3 can be suppressed and the change in the concentration of the electrolyte solution 3 can be suppressed. . This effect is significant when the gel layer 13 ′ is a gel of water or a low concentration electrolyte.
Moreover, it can suppress that KOH aqueous solution used for the electrolyte solution 3 reacts with the carbon dioxide in air | atmosphere, and precipitates as carbonate. Thereby, deterioration or concentration change of the electrolytic solution 3 can be prevented. Thus, by the gel layer 13 ′, the electrolytic solution 3 is hardly affected by the atmosphere, and the output of the metal-air battery 30 can be stabilized.
Further, by providing the gel layer 13 ′ on the liquid surface, the fluctuation of the liquid surface of the electrolytic solution 3 due to vibration can be reduced. As a result, leakage of the electrolytic solution 3 due to the fluctuation of the liquid surface of the electrolytic solution 3 can be suppressed, and the safety of the metal-air battery 30 can be improved.

Further, by providing the gel layer 13 ′ on the liquid surface of the electrolytic solution 3 in the electrolytic solution tank 2, it is possible to suppress the formation of a meniscus between the liquid surface of the electrolytic solution 3 and the metal electrode 5. it can. Thereby, it can suppress that the metal electrode 5 partially thins and the intensity | strength of the metal electrode 5 falls, can suppress corrosion of other components, such as an electrical contact, Furthermore, the electrolyte solution 3 Loss can be suppressed. When the gel layer 13 ′ is not provided on the liquid surface of the electrolytic solution 3, the electrolytic solution 3 has extremely high hydrophilicity. Therefore, a concave meniscus is formed on the liquid surface, and the electrolytic solution spreads along the surface of the metal electrode 5. . For this reason, an end portion of the meniscus is formed at a portion where the metal electrode 5 and the liquid surface of the electrolyte solution 3 are in contact with each other. The electrolyte solution at the meniscus end portion and the electrolyte solution further spreading on the surface of the metal electrode 5 are formed. The oxygen gas in the air is easily dissolved, and the self-corrosion of the metal electrode 5 is likely to proceed. For this reason, only the part which contacts the liquid level of the electrolyte solution of the metal electrode 5 tends to be thinned, and the strength tends to decrease. Further, the electrolytic solution 3 that spreads through the metal electrode 5 causes corrosion or loss of the electrolytic solution 3 when it reaches other parts such as terminals. By providing the gel layer 13 ′ on the liquid surface, it is possible to suppress the formation of such a meniscus or the spread of the electrolytic solution 3 on the surface of the metal electrode 5 due to the high water retention of the gel layer 13 ′.

The gel layer 13 ′ provided on the liquid surface of the electrolytic solution 3 does not bear ionic conduction, and thus is not limited to a gelled electrolyte solution, and may be a gelled water, for example. The water is not limited to pure water, and may include an evaporation inhibitor and the like, and is not particularly limited as long as it does not react with the electrolytic solution.
In general, a high-concentration KOH aqueous solution used for an electrolytic solution has a high density of 1.3 to 1.5. On the other hand, since water and electrolyte solution gelled expand by gelation, the density is low. For this reason, the gel layer 13 floats on the liquid surface and can be held and fixed on the liquid surface.
The gel layer 13 ′ on the liquid surface of the electrolytic solution 3 is formed by, for example, adding a gelling agent to the electrolytic solution 3 or water stored in the external container to gel the electrolytic solution 3 or water in the external container to form the gel layer 13 ′. It can be formed by floating the formed gel layer 13 ′ on the liquid surface of the electrolytic solution 3.
Note that when the metal electrode 5 is inserted into the electrolytic solution tank 2, the gel layer 13 'may adhere to the surface of the metal electrode 5, but the gel layer 13' immediately becomes a metal due to the buoyancy of the gel layer 13 '. It peels off from the electrode 5 and floats on the liquid surface. Moreover, if gel layer 13 'is what gelatinized electrolyte solution, even if gel layer 13' adheres to the metal electrode 5, since ion conduction is not prevented, it can discharge.
Further, the end of the gel layer 13 ′ may be fixed to the housing 1. As a result, it is possible to prevent the installation location of the gel layer 13 ′ from changing when the metal electrode 5 is replaced.

The gel layer 13 ′ provided on the liquid surface of the electrolytic solution 3 accommodated in the electrolytic solution tank 2 contains the gel layer 13 ′ in the electrolytic solution tank 2, for example, like the metal-air battery 30 shown in FIG. 7. It can be provided so as to float on the liquid surface of the electrolytic solution 3.
Moreover, you may provide the gel layers 13 and 13 'on both the liquid level of the electrolyte solution 3 and the air electrode 9, like the metal air battery 30 shown in FIG. The gel layer 13 may be provided both on the liquid surface of the electrolytic solution 3 and in the porous body 32, or both on the liquid surface of the electrolytic solution 3 and in the air electrode 9.
Thereby, both leakage of the electrolyte solution through the pores of the air electrode 9 and leakage of the electrolyte solution when the metal electrode 5 is replaced can be suppressed.
Moreover, like the metal-air battery 30 shown in FIGS. 7 and 8, the liquid level can be adjusted so that the discharge port 15 of the electrolytic solution 3 is maintained at a position lower than the position of the gel layer 13 ′. Accordingly, it is possible to suppress the gel layer 13 ′ from flowing into the discharge port 15 even when the electrolytic solution 3 is circulated.

When the concentration of the metal-containing ions generated in the electrolytic solution 3 by the anodic reaction exceeds the saturation concentration, the metal-containing ions may be deposited in the electrolytic solution 3 as fine particles of metal oxide or metal hydroxide (precipitate 17). . Further, when the concentration of the metal-containing ions reaches the passive film forming concentration, the metal-containing ions may be deposited on the surface of the metal electrode 5 as a passive film of metal oxide or metal hydroxide. Therefore, the precipitate 17 may be deposited as fine particles floating in the electrolytic solution or settling on the bottom of the electrolytic solution tank 2, or may be deposited as a passive film attached on the surface of the metal electrode 5.

If the precipitate 17 is deposited as fine particles and the fine particles are excessively present in the electrolyte solution 3, the fine particles of the precipitate 17 adhere to the pores of the porous air electrode 9, thereby preventing oxygen gas diffusion. As a result of the fine particles of the precipitates 17 adhering to the pores of the porous body 32 and the air electrode catalyst layer 9, the ion conduction path of OH ⁻ ions is hindered, resulting in a decrease in the output of the metal-air battery 30. . For this reason, when the fine particles of the precipitate 17 accumulate in the electrolytic solution, it is necessary to remove the fine particles from the electrolytic solution 3.
When the precipitate 17 is deposited as a passive film, and this passive film covers most of the surface of the metal electrode 5, the anode reaction on the surface of the metal electrode 5 is inhibited, and the output of the metal-air battery 30 decreases. For this reason, it is possible to continue the discharge by the metal-air battery 30 by removing the metal electrode 5 covered with the passive film from the electrolyte bath 2 and inserting a new metal electrode 5 into the electrolyte bath 2. .

For example, in the case of a zinc-air battery, the electrode active material is metallic zinc, and zinc hydroxide or zinc oxide is deposited in the electrolytic solution. In the case of an aluminum air battery, the electrode active material is metallic aluminum, and aluminum hydroxide is deposited in the electrolytic solution. In the case of an iron-air battery, the electrode active material is metallic iron, and iron oxide hydroxide or iron oxide is deposited in the electrolytic solution. In the case of a magnesium air battery, the electrode active material is metallic magnesium, and magnesium hydroxide is deposited in the electrolyte.
In the case of lithium-air batteries, sodium-air batteries, and calcium-air batteries, the electrode active materials are metallic lithium, metallic sodium, and metallic calcium, respectively, and oxides and hydroxides of these metals are contained in the electrolyte. Precipitate. In the case of a lithium air battery, a sodium air battery, or a calcium air battery, a solid electrolyte membrane may be provided between the metal electrode 5 and the electrolytic solution. Thereby, it can suppress that an electrode active material is corroded by electrolyte solution. In this case, the electrode active material is dissolved in the electrolytic solution after ion conduction through the solid electrolyte membrane.
In addition, an electrode active material is not limited to these examples, What is necessary is just a metal air battery. Moreover, although the electrode active material contained in the metal electrode 5 mentioned the metal which consists of a kind of metal element in said example, the electrode active material contained in the metal electrode 5 may be an alloy.

The metal electrode current collector has conductivity. Further, the shape of the metal electrode current collector is preferably a plate shape, a shape provided with a hole penetrating in the thickness direction of the plate, an expanded metal or a mesh. In addition, the metal electrode current collector can be formed of, for example, a metal having corrosion resistance against the electrolytic solution. The material of the metal electrode current collector is, for example, nickel, gold, silver, copper, stainless steel or the like. The metal electrode current collector may be a nickel-plated, gold-plated, silver-plated, or copper-plated conductive substrate. For this conductive substrate, iron, nickel, stainless steel, or the like can be used.
As a result, the charge generated in the metal electrode 5 by the anode reaction can be collected by the metal electrode current collector, and the generated charge can be output to an external circuit. The electrode active material layer may be fixed on the main surface of the metal electrode current collector, for example, by pressing metal particles or lumps that are electrode active materials against the surface of the metal electrode current collector. A metal may be deposited on the current collector by plating or the like. Regarding the shape of the metal electrode current collector, the plate shape is preferable from the viewpoint of conductivity when the electrode active material is deposited by plating, and when the metal particles or lump is fixed, the particles or lump is dropped. From the viewpoint of preventing this, a plate provided with a through hole, or an expanded metal or mesh is preferable.

The metal electrode 5 can constitute a metal electrode holder together with the metal electrode support. The metal electrode holder is provided so that the metal electrode 5 can be inserted into the electrolytic solution tank 2 and the used metal electrode 5 can be extracted from the electrolytic solution tank 2. As a result, the electrode active material can be supplied to the metal-air battery 30.
A metal electrode support body can be provided so that it may become a lid | cover of the electrode insertion port provided in the metal air battery main body. Thus, the metal electrode 5 can be inserted into the electrolytic solution tank 2 and the electrode insertion port can be covered, and the reaction between the components in the atmosphere and the electrolytic solution 3 can be suppressed.

Discharge test 1
As Example 1, a zinc-air battery having four cells 4 such as the metal-air battery 30 shown in FIG. 1 was produced and a discharge test was performed. In addition, as for the produced zinc air battery, the side surface of each cell is not couple | bonded. Moreover, the air flow path 12 was not provided, but the opening of the air electrode current collector 10 was opened to the atmosphere.
A porous electrode was used as the zinc electrode which is the metal electrode 5. Porous formation is often attempted to increase the reaction surface area. By increasing the reaction surface area, the applied current value per unit area can be reduced, so that it is difficult to form a passive film on the electrode surface, and it is easy to maintain an active surface.

The zinc electrode is a SUS304 support (70 x 50 mm, thickness 1 mm) (metal electrode current collector) coated with a mixture of zinc powder and PTFE dispersion as a binder. Electrode active material layer) was formed (the area of the porous electrode was 50 × 50 mm and the thickness was 20 mm). The zinc electrode was inserted into the electrolyte bath 2 after forming the zinc-air battery body.
An air electrode current collector 10 having a plurality of openings, an air electrode 9 (having a gas diffusion layer 8 and an air electrode catalyst layer 7), and a gel layer 13 are formed in this order. The air electrode current collector 10 was fixed to the opposite side wall portions of the electrolytic solution tank 2 also serving as the casing 1 to form a single cell main body.
The size of the air electrode 9 is 50 × 50 mm, the thickness is about 300 μm, the depth of the electrolytic solution tank 2 is 80 mm, and the material of the electrolytic solution tank 2 (housing 1) is made of ABS.

The material of the air electrode current collector 10 was an iron plate plated with Ni. The air electrode current collector 10 is provided with a plurality of openings having a diameter of 1 mm, and the opening ratio is 50%. The thickness of the air electrode current collector 10 is 1 mm. For the gas diffusion layer 8, 35BC manufactured by SGL was used. 35BC consists of carbon fiber and a microporous layer, and the microporous layer is a layer made of carbon black and water repellent resin (PTFE). The water-repellent resin is necessary for preventing leakage of the electrolytic solution, and functions as gas-liquid separation. That is, the electrolytic solution is prevented from leaking from the electrolytic solution tank 2, and the supply of oxygen to the air electrode catalyst layer 7 is not hindered. The air electrode catalyst layer 7 contains Tanaka Kikinzoku Pt-supported carbon and water-repellent resin (PTFE). In order to increase the reaction surface area, Pt is supported as fine particles on carbon having a large surface area. Similar to the gas diffusion layer, the water repellent resin (PTFE) contained in the air electrode catalyst layer 7 is also mixed to prevent leakage of the electrolyte. The catalyst loading was 0.5 mg / cm ² and the thickness of the air electrode catalyst layer 7 was about 30 μm.

The surface of the air electrode catalyst layer 7 on the metal electrode 5 side is covered with the gel layer 13 as shown in FIG. The gel layer 13 is coated with potassium polyacrylate (Aldrich # 435325, powder) on the air electrode catalyst layer 7 using cotton, and a 7 mol / cm ³ KOH electrolyte solution is sprayed thereon. Scattered and formed. At this time, the spray amount of the electrolyte was about 10 times the weight of polyacrylic acid. After leaving the air electrode 9 for 3 days, the air bubbles in the gel layer 13 are evacuated and degassed, and then the air electrode catalyst layer 7 and the gel layer 13 which are porous are entangled with each other by pressing well. Was made. The thickness of the gel layer 13 was about 2 mm.

Four unit cell bodies formed as described above were wired in series to form a zinc-air battery body. As the electrolytic solution 3, a 7 mol / dm ³ KOH aqueous solution was used and flowed from the bottom to the top of each cell 4a to 4d as shown in FIG. 1 at a flow rate of 400 mL / min. And the zinc electrode was inserted in the electrolyte chamber of each cell 4, respectively, and the zinc air battery was completed. The reaction part (50 × 50 mm) of the zinc electrode faces the air electrode 9 and is inserted substantially in parallel.

Also, when inserting the zinc electrode, the zinc powder was not removed. Immediately after the zinc electrode was inserted, an electromotive force was generated (the open circuit voltage of the single cell 4 was about 1.6 V), and the battery was in a dischargeable state. The start-up property of the zinc-air battery was good. The zinc electrode was not in contact with the gel layer 13 and was in the electrolytic solution 3. The electrolyte solution discharged from each cell 4 enters the precipitation tank 18 as shown in FIG. 1, and zinc oxide (precipitate 17) deposited in the electrolyte solution is naturally precipitated and collected.

In a single cell, since the zinc electrode faces both sides of the air electrode 9, the area contributing to the reaction is 25 cm ² × 2 and 50 cm ² (the part of the zinc electrode not facing the air electrode 9 is Not to contribute to the reaction). The load current during discharge was 1.5 A (the current per unit area of the zinc electrode was equivalent to 30 mA / cm ² ), and a constant current load test (discharge test) was performed. The discharge voltage was stable at 4.80V (about 1.20V per single cell), and power generation was possible for 4 hours.
After the discharge test, the zinc oxide in the precipitation tank 18 was recovered, the electrolyte solution and the zinc electrode were replaced with new ones, and a repeated discharge test was performed. The discharge test once a day was repeated for 30 days, but no leakage of the electrolyte solution through the pores of the air electrode 9 was confirmed. Further, when all the discharge tests were completed, the air electrode 9 was taken out and compared with the weight before the discharge test. As a result, the weight change was negligible.

Next, as Comparative Example 1, a zinc-air battery not provided with the gel layer 13 was produced and a discharge test was performed. In the zinc-air battery of Comparative Example 1, the gel layer 13 is not provided. Other configurations and test methods are the same as those of the zinc-air battery of Example 1 unless there is a contradiction.
In the zinc-air battery of Comparative Example 1, leakage of the electrolyte solution through the air electrode 9 was confirmed during the fourth discharge. Further, when the air electrode 9 was taken out after discharge, zinc oxide was fixed and adhered on the surface (a ZnO diffraction peak was detected from XRD). When the weight of the air electrode 9 taken out was measured, it increased from the weight of the air electrode 9 before power generation, and about 5% by weight of zinc dissolved in the electrolytic solution by the discharge reaction was fixed and adhered to the air electrode 9. It was.
Furthermore, in the zinc-air battery of Comparative Example 1, the discharge voltage was as low as 4.59 V (about 1.15 V per single cell). There are two possible causes for this.
One is that the zinc-air battery of Comparative Example 1 has a higher impedance, and it is assumed that the zinc oxide adhesion to the air electrode 9 has an effect. The other was due to the influence of hydrogen gas, and in both Example 1 and Comparative Example 1, generation of hydrogen gas was confirmed from the zinc electrode. In Comparative Example 1, hydrogen gas dissolved in the electrolyte solution or adhered to the air electrode 9 It is presumed that the hydrogen gas reacted at the air electrode 9 and the voltage was lower than that in Example 1 (the hydrogen gas was oxidized and the air was reduced at the air electrode 9 to constitute an internal battery, and this caused the voltage. In Example 1, it is presumed that the gel layer 13 serves as a filter and there is almost no influence of the hydrogen gas generated by the zinc electrode).

Next, as Comparative Example 2, a zinc-air battery in which the electrolyte in the electrolyte bath 2 was all gelled with a gelling agent was produced, and a discharge test was performed. In Comparative Example 2, the electrolytic solution is not circulated. Other configurations and test methods are the same as those of the zinc-air battery of Example 1 unless there is a contradiction.
In the zinc-air battery of Comparative Example 2, liquid leakage through the air electrode 9 was not confirmed for 30 days as in Example 1, and zinc oxide adhesion to the air electrode 9 was not confirmed.
However, it took time until a part of the zinc powder dropped off when the zinc electrode was inserted into the electrolyte bath 2 and the voltage increased slowly and became dischargeable. Furthermore, the zinc electrode was pulled out from the electrolytic solution tank 2 after the discharge, but the gelled electrolytic solution gathered together with zinc powder contained in the zinc electrode, zinc passivation formed on the zinc electrode, etc., and part of the zinc electrode Dropped out. These zinc powders and the like trapped in the gelled electrolyte are difficult to recover. If a part of the zinc electrode falls off, not all the zinc contained in the zinc electrode can be used for discharge, and this dropping is a factor that lowers the energy density of the zinc-air battery.

The discharge voltage of the zinc-air battery of Comparative Example 2 was as low as 4.61 V (about 1.15 V per single cell). This is because the gelled electrolyte has a higher impedance because it has lower ionic conductivity than the non-gelled electrolyte. It is presumed that such a difference was caused because the thickness of the gelled electrolyte existing between the anode and the cathode was larger than that in Example 1.
Further, in the zinc-air battery of Comparative Example 2, since the electrolyte solution that gelled after the discharge could not be easily replaced, a second discharge was attempted without replacing the electrolyte solution. In the second discharge, the battery characteristics were remarkably deteriorated and could not be discharged. This is because the electrolyte solution is not circulated, so that the homogeneous nucleation reaction that generates nuclei by collision of zinc-containing ions with each other hardly proceeds. This is presumably because the zinc-containing ion concentration in the gelled electrolyte solution was excessively increased. Thereby, in the discharge after the 2nd time, since the melt | dissolution reaction of zinc is suppressed, it is thought that a battery characteristic falls.
Further, unlike Example 1 in which zinc oxide is concentrated in the precipitation tank 18, in Comparative Example 2, zinc oxide only has to be deposited and accumulated in the gelled electrolyte. This is presumed to be a factor that further decreases the ionic conductivity. Furthermore, since zinc oxide is a semiconductor, it slightly passes electricity and causes a short circuit between the zinc electrode and the air electrode 9, which is unsafe.

Table 1 shows the measurement results of Example 1, Comparative Example 1, and Comparative Example 2 in the discharge test 1.
Leakage of the electrolyte solution through the air electrode was confirmed in the zinc-air battery of Comparative Example 1, but was not confirmed in the zinc-air battery of Example 1. From this, it was found that by providing the gel layer 13 on the air electrode 9, leakage of the electrolyte solution through the air electrode can be suppressed. The zinc-air battery of Example 1 was found to have a higher discharge voltage than the zinc-air batteries of Comparative Examples 1 and 2. The reason for this is that in the zinc-air battery of Example 1, the ion conduction resistance between the anode and the cathode is low, and there is almost no precipitation of zinc oxide on the air electrode.

Discharge test 2
As Example 2, a zinc-air battery having four cells 4 such as the metal-air battery 30 shown in FIG. 7 was produced and a discharge test was performed. In the zinc-air battery of Example 2, the gel layer 13 is not provided on the air electrode 9, but the gel layer 13 ′ is provided on the surface of the electrolytic solution stored in the electrolytic solution tank 2. The gel layer 13 was also provided on the liquid surface of the precipitation tank 18. Moreover, the electrolytic cell 20 was provided so that the electrolytic solution in the electrolytic solution tank 2 could flow. In addition, as for the produced zinc air battery, the side surface of each cell is not couple | bonded. Moreover, the air flow path 12 was not provided and the opening of the air electrode current collector 10 was opened to the atmosphere. Other configurations and test methods are the same as those of the zinc-air battery of Example 1 unless there is a contradiction.

The gel layer 13 ′ was formed by floating a solution prepared by adding a gelling agent to water outside the cell on the liquid surface of the electrolyte (covered with the gel layer 13 ′).
Further, in the discharge test using the metal-air battery 30 of Example 2, the electrolytic solution was not exchanged after the end of each discharge, and the electrolytic reaction was promoted by applying a voltage to the electrolysis electrode 21 of the electrolytic cell 20, The zinc-containing ion concentration of the electrolyte was reduced. In addition, the zinc electrode was replaced with a new one after the end of each discharge.

In the zinc-air battery of Example 2, the discharge voltage was 4.69 V (1.17 V per unit cell), and the discharge voltage was higher than those of Comparative Example 1 and Comparative Example 2 described above. This is because the gel layer 13 'is provided on the liquid surface to suppress the transpiration and moisture absorption of the electrolytic solution, and the reaction between the carbon dioxide in the atmosphere and the electrolytic solution is suppressed, thereby changing the concentration of the electrolytic solution. This is probably because it was small.
In the zinc-air battery of Example 2, leakage of the electrolyte solution through the air electrode 9 was confirmed during the fourth discharge. Further, in the zinc-air battery of Example 2, no meniscus was observed between the surface of the electrolytic solution accommodated in the electrolytic solution tank 2 and the zinc electrode. This suggests that thinning due to self-corrosion of the zinc electrode or strength reduction is unlikely to occur.

In the zinc-air battery of Example 2, when replacing the zinc electrode after completion of each discharge, the electrolyte did not drip from the used zinc electrode as in Comparative Example 1, and the replacement work was safe. It was safe to transport used zinc electrodes after collection. From this, it was found that the amount of the electrolyte remaining on the surface of the zinc electrode can be reduced by providing the gel layer 13 ′ on the surface of the electrolyte 3 accommodated in the electrolyte bath 2. Thereby, corrosion of the zinc electrode can be suppressed. Further, it is possible to prevent the used zinc electrode from becoming heavy due to the remaining electrolytic solution, and it is possible to reduce transportation costs and the like. Furthermore, since the electrolytic solution in the electrolytic solution tank 2 is hardly reduced, the replenishment frequency of the electrolytic solution can be reduced.
The measurement results of Example 2 in the discharge test 2 are shown in Table 2. For comparison, the measurement results of Comparative Examples 1 and 2 are also shown.

1, 1a, 1b, 1c, 1d:

Case

2, 2a, 2b, 2c, 2d: Electrolyte tank 3:

Electrolyte

4, 4a, 4b, 4c, 4d:

Cell

5, 5a, 5b, 5c, 5d: Metal electrode 6:

Water repellent layer

7, 7a, 7b, 7c, 7d: Air

electrode catalyst layer

8, 8a, 8b, 8c, 8d:

Gas diffusion layer

9, 9a, 9b, 9c, 9d:

Air electrode

10, 10a, 10b, 10c, 10d: air electrode

current collectors

12, 12a, 12b, 12c, 12d:

air flow paths

13, 13 ′, 13a, 13a ′, 13b, 13b ′, 13c, 13c ′, 13d, 13d ′, 13e :

Gel layer

15, 15a, 15b, 15c, 15d: Discharge port 17: Precipitate (used active material) 18: Precipitation tank 20: Electrolysis tank 21: Electrode for electrolysis 24: Precipitation 2 : Pump 26: electrolyte flow path 30: metal-air battery 32: porous body 34: second porous body 40: air electrode terminal 41: metal terminal

Claims

An electrolytic bath containing the electrolytic solution;
A metal electrode provided in the electrolyte bath and containing at least an electrode active material;
A metal-air battery comprising an air electrode that forms part of the wall of the electrolyte bath,
The air electrode has a current collector and an air electrode catalyst layer containing at least an air electrode catalyst,
A metal-air battery comprising a gelling agent in the first main surface side of the air electrode facing the electrolytic solution or in the air electrode catalyst layer.
2. The metal-air battery according to claim 1, wherein the air electrode is formed of a porous body on a first main surface facing the electrolyte solution.
The metal-air battery according to claim 2, wherein the current collector is provided between the porous body and the air electrode catalyst layer.
The air electrode catalyst layer includes an electron conductive material having pores,
The metal according to any one of claims 1 to 3, wherein the air electrode catalyst is supported on the electron conductive material, and the gelling agent is held in the pores of the electron conductive material. Air battery.
The air electrode has two or more porous bodies formed between the electrolyte and the current collector,
The metal-air battery according to any one of claims 1 to 4, wherein a gel layer containing at least the gelling agent and water is sandwiched between the porous bodies.
The metal-air battery according to any one of claims 1 to 5, further comprising a water-repellent layer containing a water-repellent resin on a second main surface located opposite to the first main surface of the air electrode.
The metal-air battery according to claim 6, wherein the air electrode catalyst layer is provided between the current collector and the water repellent layer.
The metal-air battery according to any one of claims 1 to 7, wherein the gelling agent is a water-absorbing polymer.
An electrolytic bath containing the electrolytic solution;
A metal electrode provided in the electrolyte bath and containing at least an electrode active material;
A metal-air battery comprising an air electrode that forms part of the wall of the electrolyte bath,
The air electrode has a current collector and an air electrode catalyst layer including at least an air electrode catalyst,
A metal-air battery comprising a gel layer containing at least a gelling agent and water between the electrolytic solution and the facing air electrode.
An air electrode having a current collector and an air electrode catalyst layer including at least an air electrode catalyst,
A part of the surface side of the air electrode or the air electrode catalyst layer contains a gelling agent.
The shape of the air electrode is a sheet having a first main surface and a second main surface,
The air electrode according to claim 10, wherein the gelling agent is contained at least on the first main surface side.
The air electrode according to claim 11, wherein a gel layer containing at least the gelling agent and water is formed on the first main surface.
The second main surface has a water-repellent layer containing at least a water-repellent layer resin,
The air electrode according to claim 11 or 12, wherein the air electrode catalyst layer is provided so as to be sandwiched between the current collector and the water repellent layer.
The air electrode catalyst layer includes an electron conductive material having pores,
The air according to any one of claims 10 to 13, wherein the air electrode catalyst is supported on the electron conductive material, and the gelling agent is held in the pores of the electron conductive material. very.
The air electrode according to any one of claims 10 to 14, wherein the gelling agent is a water-absorbing polymer.