JP7673464B2 - Fuel cell and method for manufacturing the same - Google Patents

Description

The present invention relates to a fuel cell and a method for manufacturing a fuel cell.

Patent Document 1 discloses a fuel cell stack having a solid electrolyte cell in which an air electrode current collector made of a porous sintered metal plate with reinforcing expanded metal is joined to a separator by spot welding.

JP 2003-263994 A

Welding is a low-cost joining method because it has relatively low electrical resistance after joining, is highly robust, and does not require additional materials. However, when welding a separator and a porous metal, there is a problem that welding defects such as so-called blowholes are likely to occur due to the expansion of air in the holes or the generation of gas due to foreign matter adhering to the interface. If a blowhole occurs, the anode gas flow path and cathode gas flow path defined by the separator will become connected, causing the problem that the anode gas and cathode gas cannot be separated.

The present invention aims to provide a fuel cell and a method for manufacturing the fuel cell that can prevent communication between the anode gas flow path and the cathode gas flow path while using welding to join the porous metal body serving as the electrode support layer to the separator.

According to an aspect of the present invention, a fuel cell is provided in which a plurality of power generation cells, each having a solid electrolyte plate, an anode electrode disposed on one surface of the solid electrolyte plate, and a cathode electrode disposed on the other surface of the solid electrolyte plate, are stacked in the thickness direction via a first interconnector and a second interconnector. The anode electrode and the cathode electrode have a support layer formed of a metal porous body, and the first interconnector has a corrugated plate shape having a plurality of first ribs that are parallel to each other and protrude toward the support layer of the anode electrode in the thickness direction and extend in a direction perpendicular to the thickness direction, and the tops of the first ribs are welded to the support layer of the anode electrode to form a first reactant gas flow path between adjacent first ribs. The second interconnector has a corrugated plate shape having a plurality of second ribs that are parallel to each other and protrude toward the support layer of the anode electrode in the thickness direction and extend in a direction perpendicular to the thickness direction. Furthermore, the opening of the first rib when the first interconnector is viewed from the opposite side to the support layer of the anode electrode is sealed by joining the second rib , and another power generation cell is joined to the surface of the second interconnector opposite to the first interconnector.

According to the above aspect, it is possible to prevent the anode gas flow path and the cathode gas flow path from communicating with each other while using welding to join the porous metal body serving as the electrode support layer to the separator.

FIG. 1 is a perspective view of a power generation unit according to a first embodiment. FIG. 2 is an exploded perspective view of the power generation unit according to the first embodiment. FIG. 3 is a cross-sectional view of the power generation units in a stacked state. FIG. 4 is a plan view showing a straight flow path. FIG. 5 is an exploded perspective view of a joint portion of two interconnectors when the flow paths are linear. FIG. 6 is a diagram showing a schematic diagram of the relationship between the welded portion and the joint portion. FIG. 7 is a plan view showing staggered flow channels. FIG. 8 is an exploded perspective view of a joint portion of two interconnectors when the flow paths are staggered. FIG. 9 is a cross-sectional view of a power generation unit according to the second embodiment. FIG. 10 is a cross-sectional view in the case where the second interconnector is a flat plate. FIG. 11 is a cross-sectional view of a power generation unit according to the third embodiment.

The following describes an embodiment of the present invention with reference to the attached drawings.

[First embodiment]
In the following description, the direction along the thickness of the power generation unit 1 (z-axis direction in the figure) is referred to as the thickness direction, the longitudinal direction of the power generation unit 1 (y-axis direction) is referred to as the longitudinal direction, and the direction perpendicular to the thickness direction and longitudinal direction (x-axis direction) is referred to as the width direction.

Figure 1 is a perspective view of a power generation unit 1 constituting a power generation module of a fuel cell according to this embodiment. Figure 2 is an exploded view of the power generation unit 1. Figure 3 is a cross-sectional view perpendicular to the longitudinal direction and thickness direction, showing two power generation units 1 (a first unit and a second unit) stacked together.

The power generation unit 1 consists of a power generation cell 2, a first interconnector 4 joined to one side of the power generation cell 2, and a second interconnector 3 joined to the other side of the power generation cell 2.

The power generation cell 2 is composed of a solid electrolyte plate 2A, an anode electrode 2C arranged on one side of the solid electrolyte plate 2A, and a cathode electrode 2B arranged on the other side of the solid electrolyte plate 2A. The cathode electrode 2B and the anode electrode 2C each have a support layer formed of a metal porous body. Hereinafter, the support layer of the cathode electrode 2B is also referred to as the cathode support layer, and the support layer of the anode electrode 2C is also referred to as the anode support layer.

The first interconnector 4 has a number of first ribs 4A that protrude in the thickness direction and extend in a direction (longitudinal direction) perpendicular to the thickness direction and are parallel to each other. The top of each first rib 4A is welded to the anode support layer. This forms a first reactant gas flow path 8 between adjacent first ribs 4A, through which the anode gas flows. In the following description, the portion where the first rib 4A and the anode support layer are welded is also referred to as the first welded portion 6.

The second interconnector 3 has multiple second ribs 3A that protrude in the thickness direction and extend in a direction (longitudinal direction) perpendicular to the thickness direction. The second interconnector 3 has a portion between adjacent second ribs 3A welded to the cathode support layer. This forms a second reactant gas flow path 9 through which the cathode gas flows between adjacent second ribs 3A. In the following description, the portion where the second rib 3A and the cathode support layer are welded is also referred to as the second welded portion 5.

The power generation unit 1, which is composed of the power generation cell 2, the first interconnector 4, and the second interconnector 3, is a unit, and the power generation module is formed by stacking these unit units in the thickness direction.

When two units (first unit and second unit) are joined, the second interconnector 3 of the second unit is joined to the first interconnector 4 of the first unit. In the joined state, the opening of the first rib 4A of the first unit is sealed by the second rib 3A of the second unit. The joining here is performed, for example, by metal solid-phase diffusion, which involves heating and warming the first rib 4A and the second rib 3A while they are in contact with each other. Alternatively, a method may be used in which the contact area with a large electrical resistance is locally heated by passing electricity between the first rib 4A and the second rib 3A while they are in contact with each other. In the following description, the part where the first rib 4A and the second rib 3A are joined is also referred to as the joint 7.

The width of the first rib 4A increases as it moves away from the first welded portion 6, and the width of the second rib 3A increases as it moves away from the joint portion 7. The maximum width of the first rib 4A is equal to or less than the minimum width of the second rib 3A, and the inclination angle of the inclined surface from the flat portion 4B of the first rib 4A toward the first welded portion 6 is smaller than the inclination angle of the inclined surface from the flat portion 3B of the second rib 3A toward the joint portion 7. This causes the inclined surface of the second rib 3A to abut against the inclined surface of the first rib 4A, making it easier to control the contact position between the first rib 4A and the second rib 3A. In addition, the amount of forming by bending the interconnectors 3 and 4 is reduced, preventing damage during processing. Next, the flow path shape of each interconnector 3 and 4 will be described.

Figure 4 (A) is a plan view of the first interconnector 4, and Figure 4 (B) is a plan view of the second interconnector 3. As shown in the figure, the first rib 4A and the second rib 3A are both linear and extend in the longitudinal direction. In other words, the first reactant gas flow path 8 and the second reactant gas flow path 9 are linear flow paths.

Figure 5 is an exploded perspective view of the first interconnector 4 and the second interconnector 3 joined as shown in Figure 3. The first welded portion 6 extends linearly in the flow path direction along the top (here, the top surface) of the first interconnector 4. The joint portion 7 is composed of two straight portions 7A parallel to the first welded portion 6, and a curved portion 7B connecting the ends of the two straight portions 7A. This is because both the first rib 4A and the second rib 3A have closed ends.

Figure 6 is a schematic diagram showing the positional relationship between the first welded portion 6 and the joint portion 7 when viewed from the thickness direction. As shown in Figure 6, the first welded portion 6 is surrounded by the joint portion 7. In other words, when the first interconnector 4 is viewed from the side opposite the anode support layer, the opening of the first rib 4A is sealed by the joining of the second interconnector 3. The effect of this will be explained by returning to Figure 3.

As described above, when the anode electrode 2C (anode support layer) made of a porous metal is welded to the first interconnector 4, there is a risk of weld defects such as blowholes occurring. For example, if a blowhole occurs near the first welded portion 6 of the first rib 4A, the first reactant gas flow path 8 will communicate with the inside of the first rib 4A (S in FIG. 3) through the blowhole. However, if the opening of the first rib 4A is sealed by the second rib 3A as in this embodiment, the reactant gas flowing through the first reactant gas flow path 8 can be prevented from leaking to the outside.

In this embodiment, the first rib 4A and the second rib 3A are described as being linear, but the same applies when the respective ribs 4A and 3A are formed in a staggered pattern, as shown in Figures 7 and 8.

As described above, in this embodiment, a fuel cell is provided in which a plurality of power generation cells 2 each having a solid electrolyte plate 2A, an anode electrode 2C arranged on one side of the solid electrolyte plate 2A, and a cathode electrode 2B arranged on the other side of the solid electrolyte plate 2A are stacked in the thickness direction via a first interconnector 4 and a second interconnector 3. At least one of the anode electrode 2C or the cathode electrode 2B has a support layer formed of a metal porous body, and the first interconnector 4 has a plurality of first ribs 4A that protrude in the thickness direction and extend in a direction perpendicular to the thickness direction and are parallel to each other, and the tops of the first ribs 4A are welded to the support layer to form a first reaction gas flow path 8 between adjacent first ribs 4A. When the first interconnector 4 is viewed from the opposite side to the support layer, the opening of the first rib 4A is sealed by joining the second interconnector 3. Another power generation cell 2 is joined to the surface of the second interconnector 3 opposite to the first interconnector 4. As a result, even if a welding defect such as a blowhole occurs near the weld (first weld 6) between the first interconnector 4 and the support layer, causing the reaction gas to leak from the first reaction gas flow path 8 into the space S inside the first rib 4A, the opening of the first rib 4A is sealed by the second interconnector 3, so the reaction gas will not leak to the outside.

In this embodiment, the second interconnector 3 has a plurality of groove-shaped second ribs 3A protruding in the thickness direction, and the second ribs 3A seal the openings of the first rib 4A. The cross section of the first rib 4A perpendicular to the longitudinal direction is wider as it moves away from the welded portion (first welded portion 6) with the support layer, and the cross section of the second rib 3A perpendicular to the longitudinal direction is wider as it moves away from the joint portion 7 with the first rib 4A, the maximum width of the first rib 4A is equal to or less than the minimum width of the second rib 3A, and the inclination angle of the inclined surface from the flat portion 4B of the first rib 4A to the first welded portion 6 is smaller than the inclination angle of the inclined surface from the flat portion 3B of the second rib 3A to the joint portion 7. This makes it easier to control the contact position between the first rib 4A and the second rib 3A. In addition, the amount of forming by bending the interconnectors 3 and 4 is suppressed, so that damage during processing can be prevented.

In this embodiment, the first interconnector 4 and the second interconnector 3 are joined by metal solid-state diffusion or local heating by passing an electric current. These joining methods allow the first interconnector 4 and the second interconnector 3 to be firmly joined without damaging the area around the joint.

[Second embodiment]
9 is a cross-sectional view perpendicular to the longitudinal direction and the thickness direction, showing a state in which the power generation units 1 according to the second embodiment are stacked. The difference from FIG. 3 is that the inclined surfaces of the first rib 4A and the second rib 3A are provided with communication holes 10 and 11.

The inclined surface of the first rib 4A is provided with a communication hole 11, so that the first reactant gas flow path 8 communicates with the space S inside the first rib 4A. As described in the first embodiment, the opening of the first rib 4A is sealed by the second rib 3A. Therefore, not only the first reactant gas flow path 8 but also the space S inside the first rib 4A becomes a flow path through which the first reactant gas flows. This increases the flow path area for the first reactant gas compared to the first embodiment, and reduces pressure loss.

By providing the inclined surface of the second rib 3A with the communication hole 10, the second reactant gas flow path 9 communicates with the space T defined by the adjacent second rib 3A and the flat portion 4B of the first interconnector 4. In addition, the contact portion between the first rib 4A and the second rib 3A is joined. Therefore, not only the second reactant gas flow path 9 but also the space T becomes a flow path through which the second reactant gas flows. As a result, the flow path area for the second reactant gas is larger than in the first embodiment, and pressure loss is reduced.

In the first and second embodiments, the second interconnector 3 is described as having a second rib 3A, but the second interconnector 3 may be a flat plate.

Figure 10 is a cross-sectional view of the vicinity of the joint between the first interconnector 4 and the second interconnector 3 when the second interconnector 3 is a flat plate.

When the second interconnector 3 is a flat plate, a first weld 6 is provided at every other contact portion between the first interconnector 4 and the anode support layer arranged in the width direction. The second weld 5 is provided at a position facing the opening of the first rib 4A where the first weld 6 is not provided. The joint 7 is provided at the contact portion between the flat portion 4B of the first interconnector 4 and the second interconnector 3. In addition, a communication hole 11 is provided on the inclined surface of the first rib 4A having the first weld 6.

As a result, not only the first reaction gas flow path 8 between adjacent first ribs 4A, but also the inside of the first rib 4A including the first welded portion 6 becomes a flow path for the first reaction gas. Even if a blowhole occurs near the first welded portion 6, the opening of the first rib 4A including the first welded portion 6 is sealed by the joint 7, so the first reaction gas will not leak to the outside.

The second reactant gas flow path 9 is defined by the inside of the first rib 4A, which does not have the first welded portion 6, and the second interconnector 3. A communication hole 10 is provided on the surface of the second interconnector 3 that faces the second reactant gas flow path 9. Since there is no first welded portion 6 on the first rib 4A in the portion where the second reactant gas flow path 9 and the first reactant gas flow path 8 are adjacent to each other, blowholes and the like do not occur. Therefore, the first reactant gas and the second reactant gas do not mix.

As described above, in this embodiment, the inclined surface of the first rib 4A is provided with a communication hole 11 that connects the space between adjacent first ribs 4A (first reaction gas flow path 8) to the space S inside the first rib 4A. This increases the flow path area for the first reaction gas, thereby reducing the pressure loss of the first reaction gas.

In this embodiment, the inclined surface of the second rib 3A is provided with a communication hole 10 that connects the space T between adjacent second ribs 3A to the space inside the second rib 3A (second reaction gas flow path 9). This increases the flow path area for the second reaction gas, thereby reducing the pressure loss of the second reaction gas.

[Third embodiment]
In the first embodiment, a configuration in which the cathode electrode 2B and the anode electrode 2C each have a support layer has been described, but the scope of the present invention is not limited to this, and a configuration in which only one of the electrodes has a support layer will be described in the present embodiment.

Figure 11 is a cross-sectional view perpendicular to the longitudinal and thickness directions, showing the state in which the first and second units in this embodiment are stacked. The difference from Figure 3 is that the second interconnector 3 and the cathode electrode 2B are not joined by welding. This is because the cathode electrode 2B does not have a support layer of a metal porous body, and therefore cannot be welded to the second interconnector 3. For the joining here, a joining method using a joining material such as contact paste is used.

In the first embodiment, the anode electrode 2C and the first interconnector 4 are welded, and the cathode electrode 2B and the second interconnector 3 are welded. When the second interconnector 3 is joined to the first interconnector 4, the welding machine cannot access the contact portion between the second interconnector 3 and the cathode electrode 2B. For this reason, the unit is made by welding the first interconnector 4 to the anode electrode 2C and the second interconnector 3 to the cathode electrode 2B.

In contrast, in the present embodiment, when the second interconnector 3 and the cathode electrode 2B are joined using a contact paste or the like, the second interconnector 3 can be joined even in a state where it is joined to the first interconnector 4. In other words, the first interconnector 4 can be welded to the anode electrode 2C of the power generation cell 2, and the second interconnector 3 can be joined to the first interconnector 4 to form a unit.

Conversely, only the cathode electrode 2B may have a support layer. In this case, the cathode electrode 2B and the second interconnector 3 are welded, and the first interconnector 4 and the anode electrode 2C are joined by contact paste or the like.

As with the configuration of the first embodiment, the configuration of this embodiment described above can prevent the first reaction gas from leaking to the outside even if a blowhole or the like occurs near the first welded portion 6.

It goes without saying that the present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of the technical ideas described in the claims.

1 Power generation unit, 2 Power generation cell, 3 Second interconnector, 4 First interconnector, 5 Second welded portion, 6 First welded portion, 7 Joint portion, 8 First reactant gas flow path, 9 Second reactant gas flow path

Claims (7)

A fuel cell in which a plurality of power generation cells, each having a solid electrolyte plate, an anode electrode disposed on one surface of the solid electrolyte plate, and a cathode electrode disposed on the other surface of the solid electrolyte plate, are stacked in a thickness direction via a first interconnector and a second interconnector,
the anode electrode and the cathode electrode each have a support layer formed of a metal porous body;
the first interconnector has a corrugated plate shape having a plurality of first ribs that are parallel to each other and protrude toward a support layer of the anode electrode in the thickness direction and extend in a direction perpendicular to the thickness direction, and tops of the first ribs are welded to the support layer of the anode electrode to form a first reactant gas flow path between adjacent first ribs;
the second interconnector has a corrugated plate shape having a plurality of second ribs that protrude toward a support layer side of the anode electrode in the thickness direction and extend in a direction perpendicular to the thickness direction and are parallel to each other;
an opening of the first rib when the first interconnector is viewed from a side opposite to the support layer of the anode electrode is sealed by being joined to the second rib ;
A fuel cell, characterized in that another of the power generating cells is joined to a surface of the second interconnector opposite to the first interconnector. 2. The fuel cell according to claim 1,
A fuel cell, wherein a communication hole is provided on the inclined surface of the first rib, the communication hole communicating a space between adjacent first ribs with a space inside the first rib. 2. The fuel cell according to claim 1 ,
A fuel cell, wherein a communication hole is provided on the inclined surface of the second rib, the communication hole communicating the space between adjacent second ribs with the space inside the second rib. 4. The fuel cell according to claim 2 ,
A cross section of the first rib perpendicular to the longitudinal direction of the first rib has a width that increases as the cross section moves away from the welded portion with the support layer,
A cross section of the second rib perpendicular to the longitudinal direction has a width that increases as the cross section moves away from the joint portion with the first rib,
The maximum width of the first rib is equal to or smaller than the minimum width of the second rib,
A fuel cell, wherein an inclination angle of an inclined surface extending from the flat portion of the first rib toward the welded portion is smaller than an inclination angle of an inclined surface extending from the flat portion of the second rib toward the joint portion. A method for manufacturing a fuel cell in which a plurality of power generation cells, each having a solid electrolyte plate, an anode electrode disposed on one surface of the solid electrolyte plate, and a cathode electrode disposed on the other surface of the solid electrolyte plate, are stacked in a thickness direction via a first interconnector and a second interconnector,
forming a support layer made of a metal porous body on the anode electrode and the cathode electrode;
the first interconnector is formed in a corrugated plate shape having a plurality of first ribs that protrude in the thickness direction toward a support layer of the anode electrode and extend in a direction perpendicular to the thickness direction and are parallel to each other;
a first reactant gas flow passage is formed between adjacent first ribs by welding a top of the first rib to a support layer of the anode electrode ;
the second interconnector is formed in a corrugated plate shape having a plurality of second ribs that protrude in the thickness direction toward a support layer of the anode electrode and extend in a direction perpendicular to the thickness direction and are parallel to each other;
an opening of the first rib when the first interconnector is viewed from a side opposite to the support layer of the anode electrode is sealed by joining the second rib ;
A method for manufacturing a fuel cell, comprising joining another of the power generating cells to a surface of the second interconnector opposite to the first interconnector. 6. The method for producing a fuel cell according to claim 5 ,
The first interconnector and the second interconnector are joined by metallic solid phase diffusion. 6. The method for producing a fuel cell according to claim 5 ,
The first interconnector and the second interconnector are joined by local heating caused by electrical current passing therethrough.

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