JP6990532B2 - Air electrode and metal-air battery - Google Patents

Description

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

Since the air electrode (positive electrode) needs to take in air, the current collector of the air electrode is preferably formed of a porous material. Conventionally, for example, a wire mesh, a punching metal foil, a foamed metal, or the like has been used as a current collector for the air electrode (positive electrode) of a metal-air battery (see Patent Documents 1 and 2 below). Then, the catalyst layer is superposed on the current collector to form an air electrode.

When the catalyst layer is a sheet, in order to bring the catalyst layer and the current collector into close contact with each other, a conductive adhesive is interposed between the catalyst layer and the current collector, or the catalyst layer is formed from both sides of the current collector. It is necessary to hold it by the rivet effect.

Japanese Unexamined Patent Publication No. 2016-146257 Japanese Unexamined Patent Publication No. 2016-192380

However, in the structure in which the conductive adhesive is applied to bring the current collector and the catalyst layer into close contact with each other, the conductive adhesive cannot be appropriately applied to the surface of the porous current collector. Therefore, it takes time and effort to apply the conductive adhesive, and there is a problem that the current collector and the catalyst layer cannot be firmly fixed.

Further, in the structure in which the current collector and the catalyst layer are brought into close contact with each other by sandwiching the catalyst layer from both sides of the current collector, a wasteful cost is required by providing the catalyst layer on the surface that does not contribute to the battery reaction. Further, by sandwiching both sides of the current collector with the catalyst layer, the effect of taking in air by using the current collector as a porous material is reduced, and a good battery reaction cannot be obtained.

The present invention has been made in view of this point, and uses a current collector capable of easily adhering the catalyst layer, an air electrode using the current collector, and the air electrode as compared with the conventional case. The purpose is to provide a metal-air battery that has been used.

The air electrode of the present invention has a current collector in which a metal wire rod and a thermoplastic resin wire rod are woven , and a catalyst layer directly fused to one surface of the current collector. It is characterized by.

Further, the air electrode of the present invention is directly fused to one surface of the current collector formed in a mesh shape by using a metal wire and a thermoplastic resin wire. It is characterized by having a catalyst layer .

In the present invention, the wire is woven in a plurality of different directions by a weaving machine, and the wire woven in one or more directions is the thermoplastic resin, or the thermoplastic resin wire and the metal wire are mixed. Therefore, it is preferable that the wire rod woven in the remaining direction is the metal, or the wire rod of the metal and the wire rod of the thermoplastic resin are mixed.

In the present invention, it is preferable that the vertical wire and the horizontal wire are woven by a loom, the vertical wire is the thermoplastic resin, and the horizontal wire is the metal.

In the present invention, the wire diameter of the metal is preferably 150 μm or more. Further, in the present invention, the current collector is preferably 30 mesh or more.

Further, the metal-air battery of the present invention is characterized by having an air electrode described above and a metal electrode arranged to face the air electrode.

According to the current collector of the present invention, the catalyst layer can be easily brought into close contact without using a conductive adhesive and without sandwiching the catalyst layer from both sides.

Further, according to the air electrode of the present invention, the catalyst layer can be directly fused and held to the current collector.

It is a partial plan view of the current collector of this embodiment. It is sectional drawing of the air electrode of this embodiment. It is sectional drawing of the metal-air battery of this embodiment. It is a photograph which shows the state of the surface of the current collector of the part which faced a catalyst layer, and the part which did not face a catalyst layer. It is a schematic diagram of FIG. It is a graph which shows the relationship between the number of meshes and a voltage.

Hereinafter, an embodiment of the present invention (hereinafter, abbreviated as “the present embodiment”) will be described in detail. The present invention is not limited to the following embodiments, and can be variously modified and implemented within the scope of the gist thereof.

(Current collector)
FIG. 1 is a partial plan view of the current collector of the present embodiment. As shown in FIG. 1, the current collector 1 is formed by weaving a metal wire 2 and a thermoplastic resin wire 3. Further, the current collector 1 of the present embodiment is formed in a mesh shape (net structure) by using a metal wire rod 2 and a thermoplastic resin wire rod 3. Therefore, the current collector 1 is provided with a large number of through holes 1a.

The current collector 1 of the present embodiment is formed in a mesh shape by weaving a wire rod in the vertical direction (Y direction) and a wire rod in the horizontal direction (X direction) by, for example, an automatic loom. Here, the vertical direction and the horizontal direction are in a substantially orthogonal relationship. The current collector 1 is not limited to the biaxial weaving, and may be a multiaxial weaving having a triaxial weaving or more. However, in the following, a biaxial weaving structure will be used as a representative.

As shown in FIG. 1, it is preferable that the wire rod in the vertical direction (Y direction) is the wire rod 3 of the thermoplastic resin, and the wire rod in the horizontal direction (X direction) is the wire rod 2 of metal.

The material of the metal used for the current collector 1 is not limited, and known materials can be applied. For example, stainless steel, nickel, copper, aluminum, tungsten, titanium, silver, and gold can be applied. You can select one or more types from the above. Of these, stainless steel, nickel, copper, and aluminum are preferably selected from the viewpoint of rust prevention and production cost. Further, it is preferable that the surface of the metal wire 2 is plated. For example, tin plating or nickel plating can be selected.

The material of the thermoplastic resin used for the current collector 1 is not limited, and known materials can be applied. For example, polyethylene (PE), polypropylene (PP), and polyamide (PA). ), Polycarbonate (PC), Polyacetal (POM), Polyphenylene sulfide (PPS), Vinylidene chloride (PVDC), Polyethylene terephthalate (PET), Ethylene tetrafluoride (PTFE), Vinyl chloride (PVC), Vinyl acetate (PVAC), One or more can be selected from polyvinyl alcohol (PVA), polystyrene (PS), ABS, polyurethane (PUR) and the like. Of these, polyethylene, polyamide, and polyethylene terephthalate are preferably selected from the viewpoint of versatility and adhesion.

Conventionally, for example, a wire mesh in which the wires 2 and 3 in the vertical and horizontal directions shown in FIG. 1 are made of metal has been used as a current collector. However, in the configuration of the current collector, for example, it is necessary to sandwich the sheet-shaped catalyst layer from both sides of the current collector and hold the catalyst layer by the rivet effect. Alternatively, when a current collector made of a punching metal foil or a foamed metal is used, for example, it is necessary to apply a conductive adhesive to the surface of the current collector and then hold the catalyst layer. As described above, conventionally, it has been difficult to directly hold the catalyst layer on one side of the current collector.

On the other hand, in the current collector 1 of the present embodiment, a wire rod made of a thermoplastic resin and a wire rod made of metal are woven. Specifically, the wire is woven in a plurality of different directions by a loom, and the wire woven in one or more directions is composed of a thermoplastic resin or a mixture of a thermoplastic resin wire and a metal wire. To. Further, the wire rod woven in the remaining direction is made of metal or a mixture of a metal wire rod and a thermoplastic resin wire rod. Preferably, the wire rod 3 in the vertical direction (Y direction) and the wire rod 2 in the horizontal direction (X direction) are woven by a loom, the wire rod 2 in the horizontal direction is made of metal, and the wire rod 3 in the vertical direction is made of a thermoplastic resin. did. Thereby, for example, by arranging the sheet-shaped catalyst layer only on one side of the current collector 1 and heat-pressing, the thermoplastic resin and the catalyst layer can be heat-sealed and brought into close contact with each other.

As described above, according to the current collector 1 of the present embodiment, in holding the catalyst layer, a conductive adhesive is not required as in the conventional case, and it is not necessary to sandwich both sides of the current collector with the catalyst layers. .. Therefore, the current collector 1 and the catalyst layer can be easily brought into close contact with each other as compared with the conventional case.

In the present embodiment, a form in which a metal wire and a thermoplastic resin wire are randomly arranged is also one of the present embodiments. As the current collector, for example, in the case of biaxial weaving, it is preferable that the metal wire is arranged not only in the horizontal direction (X direction) but also in the vertical direction (Y direction). However, in order to ensure smooth weaving by an automatic weaving machine, in biaxial weaving, all the wire rods 3 in the vertical direction (Y direction) are made of thermoplastic resin, and all the wire rods 2 in the horizontal direction (X direction) are made of metal. Is preferable.

Further, in the present embodiment, the wire diameter of the metal is preferably 150 μm or more. By setting the wire diameter of the metal to 150 μm or more, deformation of the current collector and the air electrode can be suppressed, and the current collector 1 can be appropriately kept in a sheet shape. That is, it is known that if the wire diameter of the metal is too small, the degree of deformation (curl) becomes large when the air electrode is placed on the current collector and hot-pressed. Therefore, in order to suppress deformation, it is necessary to secure a certain amount of metal wire diameter. By the experiment described later, the wire diameter of the metal was set to 150 μm or more. As a result, the current collector 1 can be easily handled and can be appropriately used as an air electrode. The wire diameter of the metal is preferably 350 μm or less. This makes it easier for the automatic loom to weave the metal wire and the thermoplastic resin wire. Further, since the current collector 1 can maintain an appropriate flexibility, the contact area between the sheet-shaped catalyst layer and the metal of the current collector 1 can be maintained at an appropriate size. In the present embodiment, the wire diameter of the metal is more preferably 160 μm or more and 320 μm or less, and further preferably 250 μm or more and 320 μm or less.

The wire diameter of the thermoplastic resin is not particularly limited as long as it can be fused with the catalyst layer, but for example, the wire diameter of the thermoplastic resin is 100 μm or more and 400 μm or less.

Further, the current collector 1 is preferably 30 mesh or more. Here, "30 meshes" means that the number of meshes per inch is 30. In this way, by setting the number of meshes to 30 or more, the current collecting effect can be improved. As shown in the experimental results described later, when the current density is 0.025 A / cm ² , it is evaluated at a voltage of 1 V or more. That is, by having a voltage of 1 V or more, it functions appropriately as a current collector 1, and the performance of a metal-air battery using the current collector 1 as an air electrode can be effectively improved. By setting the mesh to 30 mesh or more, it is possible to obtain a voltage of 1 V or more when the current density is 0.025 A / cm ² .

In the present embodiment, it is preferable that at least one of the conditions that the wire diameter of the metal is 150 μm or more and that the current collector 1 is 30 mesh or more is satisfied, but both conditions are satisfied. Is more preferable. Further, these conditions are preferably applied not only to the biaxial weaving structure but also to the multiaxial weaving structure having three or more axes.

(Air pole)
FIG. 2 is a cross-sectional view of the air electrode of the present embodiment. As shown in FIG. 2, the air electrode (positive electrode) 10 includes a current collector 1 and a catalyst layer 11 formed on one surface 1b of the current collector 1.

The air electrode 10 in the present embodiment is obtained by hot-pressing the current collector 1 and the catalyst layer 11. In the present embodiment, the thermoplastic resin of the current collector 1 and the catalyst layer 11 can be directly fused by the heat press. As a result, the current collector 1 and the catalyst layer 11 can be easily brought into close contact with each other. Here, the adhesion between the current collector 1 and the catalyst layer 11 in the present embodiment that has been hot-pressed is substantially the same as that of a conventional air electrode that holds the catalyst layer on a punching metal foil or foamed metal via a conductive adhesive. It turned out to be the adhesion of.

Further, in the present embodiment, the heat treatment temperature when the current collector 1 and the catalyst layer 11 are hot-pressed is appropriately determined by the softening point of the thermoplastic resin and the binder resin contained in the catalyst layer 11, the glass transition point, and the like. It will be adjusted. However, the heat treatment temperature is preferably adjusted to about 200 ° C. or lower. By preventing the heat treatment temperature from becoming too high, it is possible to prevent deformation and suppress deterioration of the characteristics of the current collector.

In FIG. 2, the catalyst layer 11 is formed over the entire area of one surface 1b of the current collector 1, but the area of the catalyst layer 11 may be smaller than the area of the current collector 1. For example, the catalyst layer 11 is formed in a substantially central portion excluding the outer periphery of one surface 1b of the current collector 1.

The material of the catalyst layer 11 is not particularly limited, but is formed of, for example, a mixture of a catalyst that promotes the reaction and a binder resin. As the catalyst, a carbon material such as carbon or a metal material such as copper or aluminum can be used. Further, it is preferable to use a thermoplastic resin such as polytetrafluoroethylene (PTFE) or polyethylene as the binder resin.

(Metal-air battery)
FIG. 3 is a cross-sectional view of the metal-air battery of the present embodiment. As shown in FIG. 3, the metal-air battery 20 includes, for example, a pair of air poles 10 arranged on both sides and a metal pole 21 arranged inside the air pole 10. The air pole 10 and the metal pole 21 are fixedly supported by the case 22. The air pole 10 is arranged so as to be exposed on the side surface of the case 22, for example, on the outside of the case 22 and inside the case 22. As a result, the air electrode 10 is arranged in a state of being exposed to air. Further, the metal pole 21 is arranged in the case 22, and the air pole 10 and the metal pole 21 are arranged to face each other in the case 22. Then, when the electrolytic solution 23 is supplied into the case 22, power generation is started.

The material of the metal electrode 21 is not particularly limited, and examples thereof include magnesium, aluminum, zinc, and iron. Particularly preferred is magnesium. Further, in FIG. 3, a plurality of air electrodes 10 are arranged, but one may be used. The air electrode 10 is arranged on the side where the catalyst layer 11 shown in FIG. 2 is in contact with the electrolytic solution 23 and on the side where the current collector 1 is in contact with the outside (air).

Hereinafter, the present embodiment will be described in detail with reference to Examples. The present embodiment is not limited to the following examples.

(Observation of adhesion after hot pressing)
In the experiment, a sheet-shaped catalyst layer was hot-pressed and brought into close contact with the surface of the current collector shown in FIG. 1, in which the horizontal wire was formed of metal and the vertical wire was made of thermoplastic resin. At this time, the area of the catalyst layer was smaller than that of the current collector. The conditions for hot pressing were 170 ° C. for 1 minute.

Subsequently, the catalyst layer was peeled off from the current collector, and the state of the portion facing the catalyst layer and the portion not facing the catalyst layer was examined.

FIG. 4 is a photograph showing the state of the surface of the current collector between the portion facing the catalyst layer and the portion not facing the catalyst layer. FIG. 5 is a schematic diagram of FIG.

As shown in FIGS. 4 and 5, it was found that the catalyst layer remained attached to the wire rod made of the thermoplastic resin in the portion facing the catalyst layer. As a result, it was found that the thermoplastic resin and the catalyst layer were heat-sealed and adhered to each other. On the other hand, it was found that the wire rod made of thermoplastic resin remained as it was in the portion not facing the catalyst layer.

(Performance evaluation of current collector)
In the experiment, a sheet-shaped catalyst layer was hot-pressed and brought into close contact with the surface of the current collector shown in FIG. 1, in which the horizontal wire was formed of metal and the vertical wire was made of thermoplastic resin. The conditions for hot pressing were 170 ° C. for 1 minute.

The current collecting method was performed by pressing a copper plate against the current collector. In the experiment, the current collector shown in Table 1 was used.

In the experiment, a current-voltage characteristic test was performed, and the relationship between the number of meshes and the voltage was measured when the current density was 0.025 A / cm ² . The voltage was measured twice for each current collector, and the average value was obtained. The experimental results are shown in FIG. In addition, Table 2 summarizes the relationship between the number of meshes and the voltage.

FIG. 6 is a graph showing the relationship between the number of meshes and the voltage. When the current density is 0.025 A / cm ² , the voltage is required to be 1 V or more in order to function as a current collector.

As shown in FIG. 6, it was found that when the number of meshes was less than 30, the voltage was less than 1V. Based on the above, in this embodiment, it is set that 30 mesh or more is preferable.

According to the current collector of the present invention, the catalyst layer can be directly fused and brought into close contact with each other. The electrode in which the catalyst layer is brought into close contact with the current collector of the present invention can be used as an air electrode of a metal-air battery.

1 Current collectors 2, 3 Wires 10 Air poles 11 Catalyst layer 20 Metal-air batteries 21 Metal poles 22 Case 23 Electrolyte

Claims (7)

An air electrode characterized by having a current collector in which a metal wire and a thermoplastic resin wire are woven, and a catalyst layer directly fused to one surface of the current collector. It is characterized by having a current collector formed in a mesh shape using a metal wire and a thermoplastic resin wire, and a catalyst layer directly fused to one surface of the current collector. The air pole to be. The current collector is made by weaving wires in a plurality of different directions by a weaving machine, and the wires woven in one or more directions are a thermoplastic resin or a mixture of the thermoplastic resin wire and the metal wire. The first or second aspect of the invention, wherein the wire woven in the remaining direction is a mixture of the metal or the metal wire and the thermoplastic resin wire. Air pole. The current collector is characterized in that a vertical wire and a horizontal wire are woven by a weaving machine, the vertical wire is the thermoplastic resin, and the horizontal wire is the metal. The air electrode according to claim 1 or 2. The air electrode according to any one of claims 1 to 4, wherein the wire diameter of the metal is 150 μm or more. The air electrode according to any one of claims 1 to 5, wherein the current collector is 30 mesh or more. A metal-air battery comprising the air electrode according to any one of claims 1 to 6 and a metal electrode arranged to face the air electrode.

Images