JP2001015132A - Fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To keep the internal resistance of a fuel cell sufficiently low. SOLUTION: This fuel cell 10 is made by layering a plurality of unit cells 20 each equipped with an electrolyte film 21, an anode 22 and a cathode 23, between which the electrolyte film 21 is sandwiched, and separators 30 disposed on both sides of these electrodes. The fuel cell 10 is further equipped with peripheral members 27 on peripheral parts of the layered members and conducting members 28 each between neighboring unit cells. The conducting member 28 is provided along contact surfaces between the separator 30 and the peripheral member 27, and formed so that its end parts make contact with surfaces of two gas diffusion electrodes disposed on both sides of the separator 30. In the fuel cell 10, the conducting members 28 secure conductivity between neighboring unit cells.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a fuel cell,
More specifically, the present invention relates to a fuel cell having a plurality of single cells stacked and receiving an supply of a fuel gas and an oxidizing gas to obtain an electromotive force by an electrochemical reaction.

[0002]

2. Description of the Related Art A gas separator for a fuel cell is a member constituting a fuel cell stack formed by laminating a plurality of single cells, and has sufficient gas impermeability so that each of adjacent single cells can be formed. The supplied fuel gas and oxidizing gas are prevented from being mixed. As described above, the gas separator for a fuel cell constituting each unit cell is desirably formed of a member having higher conductivity in order to suppress the internal resistance of the fuel cell. Conventionally, the gas separator is manufactured using a carbon material or a metal material. It has been. Generally, since a metal material has excellent strength, if a gas separator for a fuel cell is manufactured from a metal material, a thinner gas separator can be manufactured as compared with a case where a carbon material is used. As described above, if the gas separator can be formed thinner, the whole fuel cell can be further reduced in size. In addition, since a metal gas separator can be manufactured by a simple method of pressing a metal plate, the manufacturing process can be simplified and shortened to improve productivity and suppress an increase in manufacturing cost. .

[0003]

However, when a fuel cell is constructed using a gas separator formed of a metal material, the surface of the gas separator is oxidized in an operating environment of the fuel cell to form an oxide film. Such an oxide film does not have sufficient conductivity, and the formation of the oxide film increases the contact resistance between the gas separator and a member adjacent to the gas separator, lowers the conductivity, and reduces the inside of the fuel cell. There was a possibility that the resistance would increase. If a gas separator is manufactured using a noble metal such as platinum, gold, rhodium, and iridium which is difficult to oxidize, such inconvenience can be suppressed. However, using a rare and expensive noble metal as a resource increases the manufacturing cost. This hinders the spread of fuel cells and is difficult to adopt.

As a configuration for suppressing the internal resistance of a fuel cell, there has been proposed a configuration in which a conductive seal member is provided around a gas separator (for example, Japanese Patent Application Laid-Open No. 10-1998).
247504). According to such a configuration, the conductivity is also realized by the seal member disposed around the gas separator, so that the internal resistance of the fuel cell can be further reduced. However, even when the conductive seal member is provided, the metal gas separator is oxidized in the operating environment of the fuel cell to form an oxide film on the surface, and the conductivity between the gas separator and the seal member is reduced. It cannot be suppressed that the internal resistance of the fuel cell gradually increases and the internal resistance of the fuel cell gradually increases.

[0005] The fuel cell of the present invention has been made to solve the above-mentioned problems and has an object to suppress the internal resistance of the fuel cell sufficiently low, and has the following configuration.

[0006]

The fuel cell according to the present invention comprises a plurality of unit cells each having an electrolyte layer and a pair of electrodes provided to face each other with the electrolyte layer interposed therebetween. A fuel cell that receives a supply of gas to each unit cell and obtains an electromotive force by an electrochemical reaction using the gas, and is formed of a conductive material and between two adjacent unit cells. A conducting means for connecting between two adjacent electrodes belonging to each of the two adjacent single cells, and a conductive means disposed between the two adjacent single cells and each of the two single cells; Forming a gas flow path through which the gas passes between the electrodes provided on the surface thereof, and a separator formed separately from the conducting means,
The gist is to provide.

[0007] The fuel cell of the present invention configured as described above is formed by laminating a plurality of unit cells each having an electrolyte layer and a pair of electrodes provided to face each other with the electrolyte layer interposed therebetween. By connecting the two adjacent electrodes belonging to each of the two unit cells that are adjacent to each other by a conductive means formed of a conductive material, the conductivity between the two adjacent unit cells is ensured. I have. Note that the two electrodes connected by the conducting means are an anode provided in one of two adjacent single cells and a cathode provided in the other, and these electrodes are arranged between the two adjacent single cells. They are adjacent to each other via a provided separator.

According to such a fuel cell, the conductivity between adjacent single cells is ensured by the conducting means, so that the internal resistance of the fuel cell can be sufficiently suppressed. For example, when forming a separator provided between two adjacent single cells with a metal material, even if the metal loses conductivity with oxidation, the conductivity between the single cells is ensured by the conductive member. Therefore, the internal resistance of the fuel cell does not become too large. When the conductivity between adjacent single cells is sufficiently ensured by the conducting means,
Since there is no need to ensure conductivity between the separator and the electrode, the separator can be made of a material having no conductivity, and the degree of freedom in selecting a material forming the separator is improved.

In the fuel cell according to the present invention, the conduction means is provided at an outer peripheral portion of a region where the gas flow path is formed between the separator and the electrode, and the gas is supplied to the gas flow path. It may work as a seal member for preventing leakage from the outside.

In such a case, it is not necessary to further provide a sealing member for preventing gas from leaking out, in addition to the conducting means, so that an increase in the number of parts of the fuel cell is suppressed and the structure is simplified. can do.

Further, the fuel cell according to the present invention has a cooling medium passage provided outside the region where the gas passage is formed and the region related to the electrochemical reaction and through which a predetermined cooling medium passes. Furthermore, the separator may include a heat exchanging portion that protrudes into the cooling medium flow path and that can exchange heat with the cooling medium passing through the cooling medium flow path.

[0012] In such a fuel cell, the cooling medium passing through the cooling medium flow path provided outside the area where the gas flow path is formed and the area related to the electrochemical reaction, and the heat provided by the separator. Since heat is exchanged with the exchange unit, heat generated by the electrochemical reaction is transmitted to the cooling medium via the separator and the heat exchange unit provided in the separator. Therefore, in order to keep the inside of the fuel cell within a predetermined temperature range, the flow path of the cooling medium provided in a direction parallel to the stacking surface of the fuel cell can be reduced or made unnecessary. Therefore, a member for providing such a flow path is not required, and the configuration of the fuel cell can be simplified and the entire fuel cell can be reduced in size. Further, when a cooling medium flow path provided in a direction parallel to the stacking surface of the fuel cell is not required, a structure for preventing gas leakage and a structure for preventing cooling medium leakage inside the fuel cell. Can be separated from each other, and the degree of freedom in designing each structure can be improved in accordance with the fluid for which the sealing property is to be realized.

[0013] In such a fuel cell, the separator is so formed as not to cause a short circuit with another separator provided in the fuel cell via the cooling medium passing through the cooling medium flow path. At least a part of the surface may be covered with an insulating material.

With such a configuration, since a short circuit does not occur through the cooling medium passing through the cooling medium flow path, the degree of freedom in selecting the cooling medium is improved. That is, since the cooling medium itself may have conductivity, it is possible to use a fluid containing a component that gives conductivity to the fluid, such as a component that further enhances thermal conductivity.

[0015] In the fuel cell of the present invention, the separator may be formed of an insulating material. Even in such a case, by providing the conduction means, the conductivity between the single cells can be sufficiently ensured. In addition, even when the cooling medium flow path is provided and the above-described heat exchange section is provided in the separator, a short circuit does not occur through the cooling medium, and the freedom of selecting the cooling medium can be secured.

In the fuel cell according to the present invention, the separator may be formed of a material having excellent thermal conductivity. With the above-mentioned cooling medium flow path, in the case where the above-mentioned heat exchange part is provided in the separator, by forming the separator from a material having excellent thermal conductivity, the temperature distribution state in each unit cell is made more uniform. Thus, the performance of the fuel cell can be ensured. As described above, when the conductivity between adjacent unit cells is sufficiently ensured by the conductive member, the separator does not need to have conductivity. A material having excellent thermal conductivity can be selected without considering the above.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In order to further clarify the structure and operation of the present invention described above, embodiments of the present invention will be described below based on examples. The fuel cell of this embodiment is a polymer electrolyte fuel cell. The polymer electrolyte fuel cell includes a membrane made of a polymer having good conductivity in a wet state as an electrolyte layer. In such a fuel cell, a fuel gas containing hydrogen is supplied to the anode side, and an oxidizing gas containing oxygen is supplied to the cathode side, and the following electrochemical reaction proceeds.

[0018] _{^{H 2 → 2H + + 2e -}} ... (1) (1/2) O 2 + 2H + + 2e - → H 2 O ... (2) H 2 + (1/2) O 2 → H 2 O ... (3 )

Equation (1) is the reaction at the anode, (2)
The equation shows the reaction at the cathode, and the reaction shown in equation (3) proceeds in the whole fuel cell. As described above, the fuel cell directly converts chemical energy of the fuel supplied to the fuel cell into electric energy, and is known as a device having extremely high energy efficiency.

FIG. 1 is an explanatory diagram schematically showing a state of a fuel cell 10 according to a first embodiment of the present invention. The state of the cross section is shown. The present embodiment is characterized by a structure for ensuring sufficient conductivity inside the fuel cell. First, an overall configuration of the fuel cell 10 will be described with reference to FIG. As shown in FIG.
Is formed as a stack structure in which a plurality of single cells 20 are stacked. The single cell 20 includes an electrolyte membrane 21, an anode 22, a cathode 23, and a separator 30.

The anode 22 and the cathode 23 are gas diffusion electrodes having a sandwich structure sandwiching the electrolyte membrane 21 from both sides. The separator 30 forms a flow path for the fuel gas and the oxidizing gas between the anode 22 and the cathode 23 while further sandwiching the sandwich structure from both sides. Between the anode 22 and the separator 30, a fuel gas passage 24P in a single cell is formed, and between the cathode 23 and the separator 30, an oxidizing gas passage 25P in a single cell is formed. Thus, one single cell 2
0 has one separator 30 at each end thereof, and each separator 30 is shared by two adjacent single cells 20, and a fuel gas flow path is provided between adjacent single cells 20. 24P and oxidizing gas channel 25
P is separated.

Here, the electrolyte membrane 21 is a proton-conductive ion exchange membrane formed of a solid polymer material, for example, a fluororesin. In this example, a Nafion membrane (manufactured by DuPont) was used. As shown in FIG. 1, a catalyst layer 26 is provided on both surfaces of the surface of the electrolyte membrane 21. The catalyst layer 26 is formed by applying platinum, which is a catalyst for promoting the electrochemical reaction described above, or an alloy composed of platinum and another metal onto the electrolyte membrane 21.

The anode 22 and the cathode 23 are both formed of a carbon cloth woven with carbon fiber yarn. In the present embodiment, the anode 22 and the cathode 23 are formed of carbon cloth, but a configuration formed of carbon paper or carbon felt made of carbon fiber is also suitable.

The separator 30 is formed of a metal plate made of aluminum. A concave-convex structure having a predetermined shape is formed on both surfaces of the separator 30. This concavo-convex structure allows the anode 2
2 or the cathode 23, the above-described fuel gas flow path 24P in the single cell or the oxidizing gas flow path 25P in the single cell is formed. In the present embodiment, the separator 30 is formed by bonding two metal plates having the above-mentioned predetermined uneven structure formed by press molding.
In the case where the separator is manufactured by separately press-molding the two metal plates and then bonding them together, the shapes of the uneven structures formed on the respective surfaces of the separator are not affected by each other. Design flexibility can be improved. Further, since the two metal plates only need to have a thickness capable of forming the concave-convex structure formed on one surface of the separator, the separator 30 formed by laminating the two can be made thinner. Become. As described above, the separator formed by laminating two metal plates has various advantages. In addition, the separator 30 is manufactured by pressing one metal plate so as to have a predetermined uneven structure on both sides. You can also do
Further, the separator 30 may be manufactured by casting or forging.

FIG. 2 shows the structure of the separator 30. FIG. 2 shows the separator 30 as viewed from the stacking direction of the fuel cell 10. The separator 30 is shown in FIG.
As shown in FIG. 5, the surface is divided into a flow path forming portion 32 in which the above-described uneven structure is formed and an outer edge portion 34 as a peripheral region thereof. . The flow path forming section 32 is an area in the fuel cell 10 that is in contact with the gas diffusion electrode described above and forms the gas flow path in the single cell described above with the gas diffusion electrode. The flow path forming portion 32 provided in the separator 30 shown in FIG. 2 has an uneven structure in which convex portions having a rectangular cross section are regularly arranged. However, the uneven structure may have another shape. It is sufficient that a gas flow path in a single cell can be formed between them. The outer edge portion 34 is a flat plate-shaped region, and has four holes at predetermined positions. In the fuel cell, a fuel gas supply manifold, a fuel gas discharge manifold, an oxidizing gas supply manifold, and an oxidizing gas discharge manifold penetrate through this hole. The outer edge 24 contacts (adheres) an outer peripheral member 27 or a conductive member 28 described later in the fuel cell.
Area.

The stack structure is formed by laminating the separator 30, the anode 22, the electrolyte membrane 21, the cathode 23, and the separator 30 in this order. In such a stack structure, the outer peripheral portion (stack) of each member is formed. In the area corresponding to the side of the outer wall of the structure), the outer peripheral member 2
7 are provided. The outer peripheral member 27 is formed of an insulating resin, and is disposed on an outer peripheral portion of each of the laminated members, thereby preventing a short circuit from occurring inside the fuel cell and preventing a short circuit from occurring inside the fuel cell. It prevents gas from leaking out. A predetermined adhesive is applied to a region where each member constituting the stack structure and the outer peripheral member 27 are in contact with each other, and the sealing property of the fuel gas and the oxidizing gas is substantially reduced by this adhesive. Is secured. Further, instead of the adhesive, a conductive member 28 is provided in a part of the region where the separator 30 and the outer peripheral member 27 are in contact with each other.
Are arranged. The conductive member 28 has a structure corresponding to a main part of the present invention, and will be described later in detail.

Further, inside the fuel cell 10, a gas manifold, which is a flow path for fuel gas and oxidizing gas, is formed through the separators 30 and the outer peripheral member 27 in the stacking direction of the single cells 20. . FIG. 3 is an explanatory diagram schematically showing a state of a flow path of the fuel gas and the oxidizing gas formed in the fuel cell 10, and shows a state viewed from the same direction as the cross section shown in FIG. Fuel cell 10
Inside, a fuel gas supply manifold 40, a fuel gas discharge manifold 44, an oxidizing gas supply manifold 42, and an oxidizing gas discharge manifold 46 are provided. Although only the fuel gas supply manifold 40 and the oxidizing gas supply manifold 42 appear in the cross section shown in FIG.
In the actual fuel cell 10, four gas manifolds are formed as described above. Fuel gas supply manifold 4
0 and the oxidizing gas supply manifold 42 are respectively
This is a structure for distributing fuel gas or oxidizing gas to each unit cell 20. The fuel gas discharge manifold and the oxidizing gas discharge manifold are each a single cell 2
This is a structure for collecting fuel gas or oxidizing gas discharged from zero.

These gas manifolds are provided with holes penetrating in the stacking direction of the unit cells 20 at predetermined positions of the outer peripheral member 27 and the separator 30 which overlap each other when stacked in the fuel cell. It can be formed by realizing a sufficient gas sealing property between the holes provided in these members. Alternatively, the fuel cell 10
In the above, the gas manifold may be formed by fitting a tubular member in parallel to the lamination direction. When the gas manifold is formed in this way, the outer periphery of the gas manifold may be insulated. For example, the surface of a tubular member fitted into the fuel cell 10 to form a gas manifold may be coated with a non-conductive resin, or the tubular member may be formed of a non-conductive resin. .

As described above, each of the manifolds is provided so as to penetrate the inside of the fuel cell 10 in the stacking direction of the unit cells 20, and each of the manifolds is provided in the unit cell provided in each unit cell. It communicates with the gas flow path. That is, a fuel gas supply branch 41 that allows the fuel gas supply manifold 40 to communicate with the fuel gas flow path 24P in the single cell,
An oxidizing gas supply branch 43 for communicating the oxidizing gas supply manifold 42 with the oxidizing gas flow path 25P in the single cell; a fuel gas discharge manifold 44;
There is provided a fuel gas discharge branch 45 for communicating P and an oxidizing gas discharge branch 47 for connecting the oxidizing gas discharge manifold 46 and the oxidizing gas flow path 25P in the single cell. As described above, the flow path that allows the gas manifold to communicate with the gas flow path inside the single cell is provided, for example, by providing a concave portion of a predetermined shape on the contact surface of the outer peripheral member 27 with the separator 30, that is, the surface on which the separator 30 is fitted. The recess can be formed by the surface of the separator 30 fitted in the outer peripheral member 27 and the concave portion (see the fuel gas supply branch 41 shown in FIG. 1).

The fuel gas supplied from outside to the fuel cell 10 is distributed to each unit cell 20 via the fuel gas supply branch 41 while passing through the fuel gas supply manifold 40. In each single cell 20, the fuel gas flow path 24P in the single cell
Are passed through the fuel cell and subjected to an electrochemical reaction, gathered in the fuel gas discharge manifold 44 via the fuel gas discharge branch 45, and guided outside. Similarly, the oxidizing gas supplied from the outside to the fuel cell 10 is supplied to the oxidizing gas supply manifold 42.
And is distributed to each single cell 20 via the oxidizing gas supply branch 43. In each single cell 20, it is subjected to an electrochemical reaction while passing through the oxidizing gas flow path 25P in the single cell,
The oxidized gas is discharged to the oxidizing gas discharge manifold 46 via the oxidizing gas discharge branch 47 and is guided to the outside.

In the fuel cell 10 shown in FIG. 1, the fuel gas supply manifold 40 and the oxidizing gas supply manifold 42 are arranged near each other, but these gas manifolds are arranged at different positions. It is good. The above-mentioned four gas manifolds provided in the fuel cell 10 have a shape corresponding to the shape of the gas flow path in the single cell, that is, the shape of the concavo-convex structure provided on the surface of the separator 30 to form the gas flow path in the single cell. It can be provided at any position where gas can be exchanged with the gas flow path in the single cell. By providing such a gas manifold near the outer wall side surface in the fuel cell in parallel with the stacking direction of the single cells 20, it is possible to arrange the gas manifold without affecting a region related to an electrochemical reaction in the fuel cell 10.

Next, the conductive member 2 corresponding to the main part of the present invention
8 will be described. As described above, the conductive member 28 is provided in a part of the region where the separator 30 and the outer peripheral member 27 are in contact, but is provided along the contact surface between the separator 30 and the outer peripheral member 27. The two gas diffusion electrodes provided on both sides of the separator 30 are formed such that their ends are in contact with the surfaces thereof. That is, both ends of the conductive member 28 are in contact with the surfaces of the two gas diffusion electrodes facing each other with the separator 30 interposed therebetween. Therefore, in the fuel cell 10 of this embodiment having the stack structure shown in FIG. 1, the two gas diffusion electrodes facing each other with the separator 30 interposed therebetween are electrically connected by the conductive member 28, and The conductivity between the cells 20 is ensured by the conduction member 28.

The conductive member 28 is formed of a conductive resin (for example, a resin containing carbon black). Such a conductive member 28 can be provided by preparing a conductive resin in a paste form and applying the conductive resin to a region where the separator 30 and the outer peripheral member 27 are in contact with each other in the same manner as the adhesive described above. Therefore, in the fuel cell 10 of the present embodiment,
In a region where the conductive member 28 is provided, the conductive member 28
Thus, gas sealing properties are ensured, and in other areas, gas sealing properties are ensured by the adhesive described above.

FIG. 4 is an explanatory view showing the appearance of a stack structure constituting the fuel cell 10. As shown in FIG. A fuel cell 10 formed by laminating the above-described members in a predetermined order
Has a predetermined number of single cells 20 connected in series to ensure a desired output. Terminals 36A, 3 are provided at both ends where the unit cells 20 are stacked.
Current collector plates 36 and 37 having 7A are provided, and the fuel cell 10 can output to the outside via the above-mentioned two terminals. Further outside the current collector plates 36 and 37, insulating plates 38 and 39 having no conductivity and an end plate 4
8,49 are provided. The fuel cell 10 further includes:
A pressing mechanism (not shown) is provided, and the pressing mechanism applies a pressing force to the stack structure via the end plates 48 and 49 in the stacking direction to maintain the structure. Although not shown in FIG. 4, at the end of the fuel cell 10, a structure for connecting to a fuel gas supply / discharge device and an oxidizing gas supply / discharge device is provided.
Gas can be supplied to and exhausted from each of the gas manifolds described above.

According to the fuel cell 10 of the first embodiment configured as described above, two gas diffusion electrodes adjacent to each other with the separator 30 interposed therebetween are electrically connected by the conducting member 28. The conductivity between the adjacent single cells 20 can be sufficiently ensured, and the internal resistance in the fuel cell 10 can be sufficiently suppressed. In the fuel cell 10 of the present embodiment, the separator 30 is formed of aluminum as described above, but aluminum is easily oxidized, and an oxide film having low conductivity is formed on the surface. Here, each fuel cell 10 of the present embodiment is
Since the electrical conductivity between zero is sufficiently ensured by the conductive member 28, even if an oxide film is formed on the surface of the separator 30, the internal resistance of the fuel cell 10 can be sufficiently suppressed. That is, even if the contact resistance between the separator 30 and the gas diffusion electrode adjacent thereto increases due to the formation of the oxide film on the surface of the separator 30, the conductivity between the adjacent single cells 20 is maintained. , Can be sufficiently ensured by the conducting member 28.

In the above embodiment, the conductive member 28 is formed of a conductive resin. However, if the conductive member 28 is formed of a material capable of realizing sufficient adhesiveness as described above, the conductive member 28 Therefore, the use of the conductive member 28 eliminates the need for an adhesive, which is conventionally required, and suppresses an increase in the number of parts. Further, if the material constituting the conductive member 28 can be prepared in a paste form such as a conductive resin, the conductive member 28 is applied to a desired position of a predetermined member,
A conducting member 28 can be provided.

The conductive member 28 may be made of a conductive material other than the above-described conductive resin.
It suffices if it has sufficient conductivity and sufficient corrosion resistance under the operating environment of the fuel cell, and can ensure conductivity between adjacent single cells. As described above, by connecting the adjacent gas diffusion electrodes via the separator 30, a predetermined effect of suppressing an increase in the internal resistance of the fuel cell can be obtained. For example, conductive rubber, conductive ceramic, or the like can be used. Examples of the ceramic having conductivity include nitrides such as titanium nitride and chromium nitride, and oxides such as tin oxide, tungsten oxide, indium oxide, and ITO (composite oxide of indium and tin). . Alternatively, a metal having conductivity even when oxidized, such as nickel or titanium, may be used, as long as it has acceptable corrosion resistance when incorporated into a fuel cell. The conduction member 28
When formed of a solid material such as a conductive ceramic, this material is formed into a desired shape as a conductive member, and this is formed as a conductive member together with other members constituting the stack structure in a predetermined order. May be stacked to form a fuel cell.

In the embodiment described above, in each unit cell 20, the conducting member 28 is provided in a part of the area where the separator 30 and the outer peripheral member 27 are in contact. As long as sufficient conductivity can be realized, the area of the area where the conductive member 28 is provided can be arbitrarily determined. For example, the conductive member 28 may be provided on the entire outer periphery of the separator. In this case, if the material forming the conductive member 28 is a material capable of sufficiently achieving the sealing property, the above-mentioned adhesive can be eliminated, and the number of parts can be reduced to simplify the configuration of the fuel cell 10. Can be

Although the separator 30 is made of aluminum in the above embodiment, the separator 3 is made of another metal.
0 may be configured. In such a case,
The above-described effect of reducing the internal resistance of the fuel cell is obtained, and even if the metal constituting the separator is a metal whose conductivity is reduced by oxidation, the inconvenience due to the gradually increasing internal resistance of the fuel cell is suppressed. be able to.
In addition, stainless steel is generally provided with a film having a low-conductivity passivation layer on its surface, but also when a fuel cell is configured using a separator manufactured using such a metal,
By providing the conductive member 28, conductivity between the single cells can be secured, and the internal resistance of the fuel cell can be sufficiently suppressed.

Alternatively, if sufficient conductivity can be ensured by the conductive member 28, the metal separator 30
Can be formed by coating with a material having no conductivity. Some metal materials are excellent in strength and cost, but have insufficient corrosion resistance as a material constituting a separator incorporated in a fuel cell. When forming a separator with such a metal material, if it is necessary to ensure the conductivity of the separator, it is necessary to coat the separator with a rare precious metal to ensure the corrosion resistance of the metal separator. The conductive member 28
As a result, it is possible to cover the separator 30 with a material having no conductivity to ensure corrosion resistance. For covering the separator 30, for example, a resin material such as an epoxy resin having an excellent bondability with a metal and a phenol resin having an excellent heat resistance can be used. As described above, when the separator 30 is manufactured from a metal material having an advantage of being excellent in strength and moldability and capable of simplifying the manufacturing process, it is not necessary to use a noble metal or the like in order to secure corrosion resistance. Degree of freedom can be improved.

Further, the separator 30 may be formed of a material other than metal. In particular, when sufficient conductivity can be ensured by the conductive member 28, the separator 30 may be formed of a material having no conductivity. Is also good. A nonmetallic material such as a resin can be used, and may be appropriately selected in consideration of strength, workability, corrosion resistance, and the like.

In the first embodiment, the conductive member 28
Is formed along the contact surface between the separator 30 and the outer peripheral member 27 at the outer peripheral portion of the region related to the electrochemical reaction in the fuel cell, but connects the gas diffusion electrodes adjacent to each other with the separator 30 interposed therebetween. If so, conductive members may be provided in different areas.

In the above-described embodiment, the case where the separator is formed of a metal whose surface gradually loses conductivity has been described. However, the separator can maintain sufficient conductivity under the conditions in the fuel cell. Even
Like the conductive member 28 described above, by further providing a member that connects adjacent gas diffusion electrodes with a separator interposed therebetween to ensure conductivity between adjacent single cells, the internal resistance of the fuel cell can be further reduced. can do.

Although the description has been omitted in the above embodiment,
A flow path through which the cooling water passes is formed inside the fuel cell 10. When an electromotive force is generated by the above-described electrochemical reaction in a fuel cell, heat is generated because a part of the chemical energy of the fuel is released as heat without being converted into electric energy. Therefore, in order to keep the operating temperature of the fuel cell in a desired temperature range, a flow path through which the cooling water passes is usually provided inside the fuel cell, and excess heat is taken out through the cooling water.

FIG. 5 is an explanatory diagram showing a configuration of a fuel cell 10A which is a modification of the fuel cell 10, and shows a cross section viewed from the same direction as FIG. This fuel cell 10A
Has substantially the same configuration as the fuel cell 10 shown in FIG. 1, and common members are denoted by the same reference numerals and detailed description thereof will be omitted. As described above, the fuel cell 1 shown in FIG.
0, the description of the flow path of the cooling water is omitted, but FIG. 5 illustrates the flow path of the cooling water, and the fuel cell 10A includes a spacer 50 for forming the flow path of the cooling water. .
The spacer 50 is a plate-shaped member, and forms a cooling water passage 51A with the adjacent separator 30A. Also in the fuel cell 10A including such a spacer 50,
As in the above-described embodiment, by providing the conductive member 28A for connecting the gas diffusion electrodes, it is possible to suppress an increase in the internal resistance of the fuel cell. Hereinafter, the configuration of the fuel cell 10A will be described.

The separator 30A is a metal separator similar to the separator 30 shown in FIG. 1 and has a concave and convex structure having a predetermined shape on its surface. A gas passage 24P or an oxidizing gas passage 25P is formed. The separator 30A shown in FIG. 5 is formed by pressing a metal plate so as to have a predetermined uneven shape on both surfaces thereof, but has a predetermined uneven shape on the surface like the separator 30. It may be manufactured by a different method such as laminating two thin plates.

Although not shown in FIG. 5, a catalyst is provided between the electrolyte membrane 21 and each gas diffusion electrode (anode 22 or cathode 23) similarly to the fuel cell 10 shown in FIG. A layer 26 is provided.

The spacer 50 is a metal member similar to the separator 30A, and is formed in a flat plate shape as described above. The spacer 50 is provided at a position sandwiched between two separators 30A for each of a predetermined number of the unit cells 20 stacked. Here, the flow of the cooling water in the fuel cell 10A will be described.

FIG. 6 is an explanatory diagram schematically showing the state of the flow path of the cooling water in the fuel cell 10A, and shows a state viewed from the same direction as FIG. Although not shown in the cross section of the fuel cell 10A shown in FIG.
Is provided with a cooling water supply manifold 52 and a cooling water discharge manifold 53 provided to penetrate in the laminating direction. The cooling water supplied from the outside of the fuel cell 10A is distributed to each cooling water passage 51A while passing through the cooling water supply manifold 52. The cooling water passing through the cooling water passage 51A provided inside the fuel cell 10A is
The temperature rises by performing heat exchange between the fuel cell 10A and the fuel cell 10A, and is collected in the cooling water discharge manifold 53 and guided to the outside of the fuel cell 10A. As described above, the spacers 50 that form the cooling water passages 51A together with the separators 30A are provided for each of the predetermined number of the unit cells 20 that are stacked. Is the fuel cell 1
So that the internal temperature of 0A is maintained in the desired temperature range,
What is necessary is just to set according to the cooling efficiency by cooling water, etc. In FIG. 6, every time ten unit cells 20 are stacked, the spacer 5
0 is to be provided.

The conductive member 28A is provided on the outer periphery of the separator 30A. The conductive member 28A is formed of a conductive material similarly to the conductive member 28 in the fuel cell 10 described above.
As in the case of the outer peripheral member 27 in FIG.
A is held. The conductive member 28A provided at the position where the spacer 50 is provided further includes a spacer 5A.
0 is fitted in the outer periphery. Similarly to the conductive member 28 provided in the fuel cell 10, each conductive member 28A is in contact with the gas diffusion electrodes provided in each of the adjacent single cells 20 at both ends. That is, adjacent gas diffusion electrodes with the separator 30A interposed therebetween, or adjacent gas diffusion electrodes with the two separators 30A sandwiching the spacer 50 interposed therebetween, are connected to each other to be conductive.

In the fuel cell 10A, the conductive member 28
An outer peripheral member (not shown) formed of an insulating member and securing insulation at the outer peripheral portion of the fuel cell is disposed further outside A. The cooling water supply manifold 52 and the cooling water discharge manifold 53, and the fuel gas supply manifold 4 described in the above-described embodiment.
The fuel gas discharge manifold 44, the oxidizing gas supply manifold 42, and the oxidizing gas discharge manifold 46 are provided through the outer peripheral member. As mentioned above,
Conductivity is ensured between the adjacent single cells 20 by the conductive member 28A, but a short circuit inside the fuel cell 10A is prevented by the outer peripheral member provided on the outer peripheral portion of the conductive member 28A. The flow path connecting the gas manifold to each single cell gas flow path and the flow path connecting the cooling water manifold to each cooling water path 51A are connected to the conductive member 28.
A is provided so as to penetrate through the flow path A, but sufficient insulation between these flow paths and the conductive member 28A is ensured to prevent a short circuit from occurring.

When the conductive member 28A is formed of a solid member such as a conductive ceramic, the contact surface between the conductive member 28A and the separator 30A or the conductive member 28A
A predetermined adhesive may be applied to the contact surface between the spacer A and the spacer 50 to ensure sufficient sealing performance and prevent leakage of fuel gas, oxidizing gas, or cooling water. In addition, the gas sealing property in a region where the conductive member 28A and the gas diffusion electrode are in contact with each other may be realized by the above-described outer peripheral member disposed further outside the conductive member 28A. In order to further reduce the contact resistance with 28A, a conductive paste or the like may be applied between them to secure a contact area between them.

In the fuel cell 10A shown in FIG.
All the used separators have the same shape as the separator 30A.
However, the shape of the concavo-convex structure formed on the surface may be different between the separator forming the gas passage in the single cell on both sides and the separator forming the cooling water passage 51A on one side. That is, the shape of the concavo-convex structure provided on the side where the gas flow path in the single cell is formed is such that the diffusivity of the gas in the gas flow path in the single cell is further enhanced, and the concavo-convex structure provided on the side where the cooling water passage 51A is formed. May be set in consideration of, for example, resistance when cooling water passes through the inside.

As in the fuel cell 10A constructed as described above, even when spacers are stacked in addition to the separator, a short-circuit member for connecting adjacent gas diffusion electrodes with these interposed therebetween is provided. Thus, the effect of suppressing an increase in the internal resistance of the fuel cell can be obtained, similarly to the fuel cell 10 of the above-described embodiment. The fuel cell 1
At 0A, the conductive member 28A is fitted with the separator 30A and the spacer 50, and a structure for realizing sealing properties of gas and cooling water is further provided. However, the conductive member 28A is formed of a material having a predetermined adhesiveness. Forming
The conductive member 28 </ b> A may realize the sealing property together with the conductivity. For example, the fuel cell 1 shown in FIG.
Similarly to the case of No. 0, the conductive member may be formed by using a conductive paste instead of the adhesive for realizing the sealing property.

In the fuel cell 10A, the spacer 50 is provided every time a predetermined number of unit cells are stacked, thereby forming the cooling water passage 51A in the fuel cell 10A. The fuel cell can be cooled using the separator without providing a flow path of the cooling water on a plane perpendicular to the laminating direction inside. An example in which such a cooling method is applied to a fuel cell having a conducting member will be described below as a second embodiment.

FIG. 7 is an explanatory view schematically showing a cross section of the fuel cell 110 of the second embodiment. The fuel cell 110 shown in FIG. 7 has a structure similar to that of the fuel cell 10A shown in FIG. 5, and common members are denoted by the same reference numerals. Similar to the fuel cell 10A, the fuel cell 110 is formed by stacking single cells 20 each having an electrolyte membrane 21 and an anode 22 and a cathode 23 sandwiching the electrolyte membrane 21 from both sides. A conductive member 28A for connection is provided. Further, the fuel cell 110
As in the fuel cell of the above-described embodiment, the fuel cell includes a separator 130 having a predetermined uneven structure on the surface and forming a gas passage in a single cell by the uneven structure. The fuel cell 110 of the present embodiment includes the conductive member 28A as described above, and a part of the tip of the separator 130 provided in the fuel cell 110 has a flow of cooling water formed on the outer peripheral portion of the stack structure. It is characterized by protruding into the road.

In the fuel cell 110, the fuel cell 1 described above is used.
Similarly to the case of FIG. 0A, an insulating outer peripheral member 127 is provided further outside the conductive member 28A.
7 is formed in parallel with the stacking direction of the stack structure,
A cooling water manifold 152 through which cooling water passes is provided. The fuel cell 110 has the same stack structure as the fuel cell 10 of the first embodiment shown in FIG. 4, but is supplied from a predetermined cooling water supply device connected to one end of such a stack structure. The cooled water is led to a cooling water manifold 152, and the cooling water manifold
2 flows parallel to the stacking direction toward the other end of the stack structure. Meanwhile, the cooling water is supplied to each separator 13.
Heat exchange is performed with the structure protruding into the cooling water manifold 152 from zero.

A part of the outer periphery of the separator 130 has an elongated shape to form a cooling fin 135. The cooling fin 135 projects into the cooling water manifold 152 as described above, and Manifold 1
The heat can be exchanged between the cooling water passing through the inside of the cooling fin 52 and the cooling fin 135. The separator 130 is formed of a metal material similarly to the separator included in the fuel cell of the above-described embodiment, and has excellent thermal conductivity.
The heat generated by the electrochemical reaction inside the fuel cell is transmitted from inside the separator 130 to the cooling fins 135, and is discharged to the outside via the cooling water.

Here, the shape of the cooling fins 135 only needs to have a contact area that allows heat exchange with the cooling water passing through the cooling water manifold 152 with sufficient efficiency. Further, by providing the cooling fins 135, the flow of the cooling water passing through the inside of the cooling water manifold 152 is obstructed to some extent. By providing such cooling fins 135, the inside of the fuel cell 110 can be effectively cooled. Further, the cooling fins 135 have sufficient thermal conductivity and are formed by a member prepared separately from the separator 130, and then assembled to the separator 130 so as to be able to exchange heat sufficiently with the separator 130 to form an integral unit. Is also good. If the cooling fins 135 are formed of a member different from the plate-shaped separator 130 and then assembled later, the degree of freedom of the shape of the cooling fins 135 is improved.

In the fuel cell 110 including the separator 130 provided with the cooling fins 135 as described above, in order to keep the internal temperature within a desired temperature range, for example, a temperature sensor may be provided inside the fuel cell 110 or the fuel cell 110 may be provided. 110
The internal temperature of the fuel cell 110 may be measured by measuring the temperature of the cooling water discharged from the fuel cell 110, and the flow rate of the cooling water supplied to the fuel cell 110 may be controlled according to the result.

The conducting member 2 provided in the fuel cell 110
8A is sufficient as long as conductivity between adjacent gas diffusion electrodes can be ensured via a separator, similarly to the above-described embodiment.
Various materials can be selected. If sufficient conductivity can be secured between adjacent single cells, the conductive member 2
The range in which 8A is provided can be set arbitrarily. Here, if the conductive member 28A is formed of a material having a sufficient adhesiveness, the conductive member 28A is disposed between the conductive member 28A and the separator 130.
There is no need to further provide a structure for ensuring gas sealability. In such a case, the conductive member 28 is provided on the entire outer edge portion of the separator 130 including the vicinity of the region where the cooling fins 135 are provided, so that an adhesive for ensuring the sealing property is not required. Can be.

According to the fuel cell 110 of the second embodiment configured as described above, the following effects can be obtained in addition to the effects already described by providing the conductive member 28A. That is, since heat exchange is performed between the cooling water passing through the cooling water manifold 152 and the separator 130, excess heat generated by the electrochemical reaction and transmitted to the separator 130 passes through the cooling water manifold 152. The cooling water is discharged through the cooling water to be cooled, thereby reducing or eliminating the cooling water flow path (corresponding to the cooling water passage 51A provided in the fuel cell 10A described above) provided in the direction parallel to the stacking surface of the fuel cell. be able to. As described above, since the cooling water flow path provided in the direction parallel to the stacking surface of the fuel cell can be reduced or unnecessary, the above-described spacer provided for providing such a flow path can be reduced or eliminated. It can be. Therefore, the number of parts for manufacturing the fuel cell can be reduced, and the entire fuel cell can be downsized. Cooling water manifold 152
By performing heat exchange between the cooling water passing through the inside and the separator 130, the inside of the fuel cell 110 can be sufficiently cooled, and the flow path of the cooling water provided in a direction parallel to the stacking surface of the fuel cell is reduced. When the cooling water is not required, it is only necessary to provide a flow path in the stacking direction as the cooling water flow path, so that the configuration of the cooling water flow path can be simplified.
Further, a seal structure for preventing leakage of cooling water is not required in the peripheral portion of each unit cell, so that the configuration of the entire fuel cell can be simplified.

If the conducting member 28A is provided as in the fuel cell 110 of the second embodiment, and if the conductivity between the adjacent single cells can be sufficiently ensured by the conducting member 28A, as described in the first embodiment. Alternatively, the separator 130 may be covered with a non-insulating material. When cooling the inside of the fuel cell using the heat transfer of the separator, it is desirable to configure the separator with a material having high thermal conductivity such as aluminum and copper. Some do not have sufficient corrosion resistance under the operating conditions of the fuel cell. When cooling the fuel cell using the heat transfer of the separator, the conductive member 28
If the conductivity is sufficiently ensured by A, the separator can be covered with a material such as a resin that does not have conductivity but has excellent corrosion resistance so that corrosion resistance can be realized.
The degree of freedom in selecting the material for forming the separator can be ensured.

Further, if the surface of the separator is coated with a material having no conductivity, the degree of freedom in selecting a fluid usable as cooling water also in the case of cooling the fuel cell utilizing the heat transfer of the separator. Can be increased. As the cooling water to be passed through the cooling water manifold 152 described above, in addition to literally using water, various cooling media (fluids)
It is conceivable to use. For example, if a fluid having a higher heat exchange efficiency than water is used, the cooling efficiency can be further improved. Further, it is also useful to use a liquid to which a component for improving the rust-preventing property of a member constituting a flow path is added, such as a liquid used as an engine coolant in a normal gasoline engine. When the separator has conductivity, if it is not sufficiently insulated from the separator, a short circuit may occur through the fluid. By coating the surface of the separator with a material having no conductivity, short-circuiting can be prevented regardless of the type of fluid used for cooling.

In order to prevent such a short circuit, it is not necessary to cover the entire separator 130, but it is only necessary to cover an area necessary for preventing the short circuit. FIGS. 8 and 9 are schematic diagrams illustrating examples of regions to be coated on the separator 130 in order to prevent a short circuit from occurring when the fluid used for cooling has conductivity.
As shown in FIG. 8, if the coating layer 160 is provided on the separator 130 in a region in contact with the fluid used for cooling, a short circuit does not occur through the fluid used for cooling. Further, as shown in FIG.
Above, the coating layer 160 may be provided in a region that is in contact with an adjacent member (the gas diffusion electrode and the conductive member 28A) that forms the stack structure.

In the above description, the surface of the separator 130 is coated with a non-conductive material. However, the separator 130 itself may be formed of a non-conductive material. In such a case,
By providing the conductive member 28A, it is possible to sufficiently secure conductivity between the single cells, and by configuring the separator 130 with a material having sufficient thermal conductivity, the heat transfer of the separator is utilized. The inside can be cooled. Even in the case where the entire separator 130 is formed of a material having no conductivity, an effect that a short circuit does not occur even when cooling is performed using a fluid having conductivity can be obtained.

Although only one cooling water manifold 152 is described in the fuel cell 110 of the second embodiment shown in FIG. 7, a plurality of such cooling water manifolds are provided, and May be provided with a predetermined number of cooling fins so that they can exchange heat with the cooling water in each cooling water manifold.
With such a configuration, the cooling efficiency can be further improved, and the occurrence of uneven cooling in each unit cell 20 can be suppressed.

The embodiments of the present invention have been described above.
The present invention is not limited to such embodiments at all, and it goes without saying that the present invention can be implemented in various modes without departing from the gist of the present invention.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram schematically showing a cross section of a fuel cell 10. FIG.

FIG. 2 is a plan view illustrating a configuration of a separator 30.

FIG. 3 is an explanatory diagram schematically showing a state of a flow path of a fuel gas and an oxidizing gas provided in a fuel cell 10;

FIG. 4 is an explanatory diagram showing an appearance of a stack structure constituting the fuel cell 10.

FIG. 5 is an explanatory diagram showing a state of a cross section of a fuel cell 10A.

FIG. 6 is an explanatory diagram schematically showing a state of a flow path of a cooling water in a fuel cell 10A.

FIG. 7 is an explanatory diagram schematically showing a cross section of a fuel cell 110 according to a second embodiment.

FIG. 8 is a schematic diagram showing a region to be coated on a separator 130.

FIG. 9 is a schematic diagram showing a region to be coated on a separator 130.

[Explanation of symbols]

 10, 10A: Fuel cell 20: Single cell 21: Electrolyte membrane 22: Anode 23: Cathode 24: Outer edge 24P: Fuel gas channel in a single cell 25P: Oxidized gas channel in a single cell 26: Catalyst layer 27: Peripheral member 28, 28A Conductive member 30, 30A Separator 32 Flow path forming part 34 Outer edge part 36, 37 Current collector plate 36A, 37A Terminal 38, 39 Insulating plate 40 Fuel gas supply manifold 41 Fuel gas supply Fork 42 ... Oxidizing gas supply manifold 43 ... Oxidizing gas supply branch 44 ... Fuel gas discharge manifold 45 ... Fuel gas discharge branch 46 ... Oxidizing gas discharge manifold 47 ... Oxidizing gas discharge branch 48,49 ... End plate 50 ... Spacer 51A: cooling water channel 52: cooling water supply manifold 53: cooling water discharge manifold 110: fuel cell 1 27 ... outer peripheral member 130 ... separator 135 ... cooling fin 152 ... cooling water manifold 160 ... coating layer

Claims (6)

[Claims] 1. A single cell comprising an electrolyte layer and a pair of electrodes provided to face each other with the electrolyte layer interposed therebetween, and a gas is supplied to each of the single cells to utilize the gas. A fuel cell for obtaining an electromotive force by an electrochemical reaction, comprising a material having conductivity, disposed between two adjacent single cells, and belonging to each of the two adjacent single cells. A conductive means for connecting between two adjacent electrodes; a gas flow path disposed between the two adjacent single cells and passing the gas between the electrodes provided in each of the two single cells. And a separator formed on the surface thereof and separately from the conducting means. 2. The method according to claim 1, wherein the conduction unit is disposed on an outer peripheral portion of a region where the gas flow path is formed between the separator and the electrode, and the gas leaks out of the gas flow path to the outside. 2. The fuel cell according to claim 1, wherein the fuel cell functions as a seal member for preventing the occurrence of the fuel cell. 3. The fuel cell according to claim 1, wherein the cooling medium is provided outside a region where the gas flow path is formed and a region related to the electrochemical reaction, and a predetermined cooling medium passes through the inside. A fuel cell further comprising a medium flow path, wherein the separator protrudes into the cooling medium flow path and includes a heat exchange unit capable of exchanging heat with the cooling medium passing through the cooling medium flow path. 4. The fuel cell according to claim 1, wherein the separator is formed of an insulating material. 5. The fuel cell according to claim 3, wherein the separator is short-circuited with another separator provided in the fuel cell via the cooling medium passing through the cooling medium flow path. A fuel cell, characterized in that at least a part of its surface is coated with an insulating material so as not to occur. 6. The fuel cell according to claim 3, wherein the separator is formed of a material having excellent thermal conductivity.