Fuel cell stack

Abstract

To provide a fuel cell stack which can be manufactured at low manufacturing cost.SOLUTION: The fuel cell stack includes a cell unit having a plurality of fuel cells, and a sealing plate provided to face one end surface of both end surfaces of the cell unit. Each of the plurality of fuel cells includes a support frame that supports a membrane electrode gas diffusion layer assembly, and a pair of separators that sandwich the support frame. Each of the plurality of fuel cells is formed with a plurality of through holes constituting manifolds through which a fuel gas, an oxidizing gas, and a cooling medium flow, respectively, when viewed in the stacking direction. No through hole is formed in the sealing plate in a range overlapping the manifold when viewed in the stacking direction. The sealing plate is configured using a base material common to one separator of the pair of separators except for the presence or absence of the plurality of through-holes.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The technology disclosed in this specification relates to a fuel cell stack. [Background technology]

[0002] A fuel cell stack includes a cell section in which a plurality of fuel cells are stacked in a stacking direction. Each of the plurality of fuel cells has a support frame that supports a membrane electrode gas diffusion layer assembly and a pair of separators that sandwich the support frame in the stacking direction. Each of the plurality of fuel cells has a plurality of through-holes. The through-holes of adjacent fuel cells are connected in the stacking direction, thereby forming a manifold within the cell section through which fuel gas, oxidizing gas, and cooling medium flow, respectively. A sealing plate is provided facing one of both end faces of the cell section in the stacking direction, and the sealing plate seals the manifold of the cell section in the stacking direction. This allows the fuel gas, oxidizing gas, and cooling medium to flow back and forth within the cell section in the stacking direction. Patent Documents 1 and 2 disclose examples of this type of fuel cell stack. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-44937 [Patent Document 2] Japanese Patent Publication No. 2022-63506 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable to reduce the manufacturing costs of such fuel cell stacks. The present specification provides a fuel cell stack that can be manufactured at low manufacturing costs. [Means for solving the problem]

[0005] The fuel cell stack disclosed herein may include a cell section having a plurality of fuel cell units stacked in a stacking direction, and a sealing plate provided opposite one of both end faces of the cell unit in the stacking direction. Each of the plurality of fuel cell units may include a support frame supporting a membrane electrode-gas diffusion layer assembly and a pair of separators sandwiching the support frame in the stacking direction. Each of the plurality of fuel cell units has a plurality of through holes formed therein that form manifolds for respectively circulating a fuel gas, an oxidizing gas, and a cooling medium when observed in the stacking direction. When observed in the stacking direction, the sealing plate does not have through holes formed in an area overlapping with the manifold of the cell section. The sealing plate is constructed using a base material that is the same as that of one of the pair of separators, except for the presence or absence of the plurality of through holes.

[0006] The fuel cell stack disclosed in this specification can be manufactured with a small number of parts because the sealing plates are constructed using the same base material as the separators, and therefore the fuel cell stack disclosed in this specification can be said to have a structure that can be manufactured at low manufacturing costs. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 2 is a diagram schematically showing an exploded side view of a fuel cell stack. [Figure 2] FIG. 2 is a diagram schematically showing an exploded perspective view of a fuel cell; [Figure 3] FIG. 2 is a diagram schematically illustrating the configuration of the gas flow surface of the anode-side separator. [Figure 4] FIG. 2 is a diagram schematically illustrating the configuration of a cooling medium flow surface of an anode-side separator. [Figure 5] 3 is a diagram schematically illustrating the configuration of a cooling medium flow surface of a sealing plate. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0008] 1, the fuel cell stack 1 is a power generation device that generates electricity by chemically reacting a fuel gas with an oxidizing gas, and includes an anode end plate 2, an anode terminal 3, a cell section 4 having a plurality of fuel cell units 10 stacked in the stacking direction, a sealing plate 5, a cathode terminal 6, an insulator 7, and a cathode end plate 8. In the fuel cell stack 1 of this embodiment, although not particularly limited, for example, hydrogen gas may be used as the fuel gas and air may be used as the oxidizing gas.

[0009] The anode-side end plate 2 and the cathode-side end plate 8 are fastened in the stacking direction by fastening members (not shown), so that the various components provided between the anode-side end plate 2 and the cathode-side end plate 8 are sandwiched between the anode-side end plate 2 and the cathode-side end plate 8.

[0010] The anode side terminal 3 is a conductor that functions as a current collector for the cell unit 4 and is electrically connected to the anode side end face of the cell unit 4. The cathode side terminal 6 is also a conductor that functions as a current collector for the cell unit 4 and is electrically connected to the cathode side end face of the cell unit 4 via a sealing plate 5. The insulator 7 is provided between the cathode side terminal 6 and the cathode side end plate 8 and is an insulator that electrically insulates the cathode side terminal 6 from the cathode side end plate 8.

[0011] 2, each of the multiple fuel cells 10 constituting the cell section 4 includes an anode-side separator 12, a support frame 14, a cathode-side separator 16, and a membrane electrode and gas diffusion layer assembly (MEGA) 18. The support frame 14 that supports the MEGA 18 is sandwiched between the anode-side separator 12 and the cathode-side separator 16.

[0012] Each of the pair of separators 12, 16 is made of a gas-impermeable conductive material. Each of the pair of separators 12, 16 may include, for example, a metal substrate. The metal substrate is not particularly limited, but may be, for example, a stainless steel (an alloy of iron, chromium, and nickel) substrate. Furthermore, as described below, a surface treatment film for improving corrosion resistance and conductivity may be formed on a portion of the main surface of the metal substrate. The pair of separators 12, 16 may have the same shape or different shapes. That is, the anode-side separator 12 and the cathode-side separator 16 may be a common component or different components.

[0013] The support frame 14 surrounds the outer periphery of the MEGA 18 and supports the MEGA 18. The support frame 14 is made of an airtight and insulating resin material. Although not shown, the MEGA 18 is made by laminating an anode-side gas diffusion layer, an anode electrode, an electrolyte membrane, a cathode electrode, and a cathode-side gas diffusion layer in this order.

[0014] Six through holes 22a-22f are formed in each of the pair of separators 12, 16 and the support frame 14. The six through holes 22a-22f include a first supply hole 22a, a first discharge hole 22b, a second supply hole 22c, a second discharge hole 22d, a third supply hole 22e, and a third discharge hole 22f. Although not particularly limited, the first supply hole 22a is a fuel gas supply hole, the first discharge hole 22b is a fuel gas discharge hole, the second supply hole 22c is an oxidizing gas supply hole, the second discharge hole 22d is an oxidizing gas discharge hole, the third supply hole 22e is a coolant supply hole, and the third discharge hole 22f is a coolant discharge hole. Three through holes 22a, 22c, and 22e are arranged at one of the longitudinal ends of the pair of separators 12, 16 and the support frame 14, and three through holes 22b, 22d, and 22f are arranged at the other end.

[0015] In the cell section 4 of the fuel cell stack 1, each of the multiple fuel cells 10 is arranged parallel to the X and Z directions and stacked along the Y direction. The Y direction corresponds to the stacking direction in FIG. 1 . When the multiple fuel cells 10 are stacked in the stacking direction, the first supply holes 22a formed in the pair of separators 12, 16 and the support frame 14 are connected to each other to form a first supply manifold 24a. Similarly, when the multiple fuel cells 10 are stacked in the stacking direction, the second supply holes 22c and the third supply holes 22e are connected to each other to form a second supply manifold 24c and a third supply manifold 24e. When the multiple fuel cells 10 are stacked in the stacking direction, the first discharge holes 22b, the second discharge holes 22d, and the third discharge holes 22f also form a first discharge manifold 24b, a second discharge manifold 24d, and a third discharge manifold 24f, respectively. That is, six manifolds 24a-24f are formed in the cell section 4 of the fuel cell stack 1 along the stacking direction.

[0016] The raw material gas is supplied from the first supply manifold 24a to each fuel cell 10. In each fuel cell 10, a raw material gas flow passage is formed on one of the main surfaces of the anode side separator 12 that faces the MEGA 18, so that the raw material gas flows between the anode side separator 12 and the MEGA 18. The raw material gas that has passed through each fuel cell 10 passes through the first discharge manifold 24b and is sent out of the fuel cell stack 1.

[0017] The oxidizing gas is supplied from the second supply manifold 24c to each fuel cell 10. In each fuel cell 10, an oxidizing gas flow passage is formed on one of the pair of main surfaces of the cathode side separator 16 that faces the MEGA 18 so that the oxidizing gas flows between the cathode side separator 16 and the MEGA 18. The oxidizing gas that has passed through each fuel cell 10 passes through the second discharge manifold 24d and is discharged to the outside of the fuel cell stack 1.

[0018] The cooling medium is supplied from the third supply manifold 24e to each fuel cell 10. In each fuel cell 10, a cooling medium flow passage is formed in one of a pair of main surfaces of the anode side separator 12 that faces the cathode side separator 16 so that the cooling medium circulates between the anode side separator 12 and the cathode side separator 16. Similarly, a cooling medium flow passage is formed in one of the main surfaces of the cathode side separator 16 that faces the anode side separator 12. The cooling medium that has passed through each fuel cell 10 passes through the third discharge manifold 24f and is sent to the outside of the fuel cell stack 1.

[0019] As shown in FIG. 3 , multiple gas distribution grooves 26 are formed on one main surface of the anode separator 12 (i.e., the surface facing the MEGA 18; hereinafter, also referred to as the “gas distribution surface”). The multiple gas distribution grooves 26 extend from the first supply holes 22a through the power generation region PG to the first discharge holes 22b. Although not particularly limited, the multiple gas distribution grooves 26 spread radially from the first supply holes 22a toward the power generation region PG, extend parallel to each other in the power generation region PG, and converge counter-radially from the power generation region PG toward the first discharge holes 22b. As a result, the raw material gas supplied from the first supply manifold 24a to each fuel cell 10 is guided from the first supply holes 22a along the gas distribution grooves 26 and supplied to the entire power generation region PG. Then, the raw material off-gas and generated water that have passed through the power generation region PG are guided along the gas distribution grooves 26 and sent from the first discharge holes 22b to the first discharge manifold 24b. Thereafter, the raw material off-gas and the produced water are discharged to the outside of the fuel cell stack 1 through the first discharge manifold 24b.

[0020] As shown in FIG. 4, a plurality of cooling medium flow grooves 28 are formed on the other main surface of the anode separator 12 (i.e., the surface facing the cathode separator 16 of the adjacent fuel cell 10; hereinafter, also referred to as the "cooling medium flow surface"). The plurality of cooling medium flow grooves 28 extend from the third supply holes 22e through the back surface of the power generation region PG to the third discharge holes 22f. Although not particularly limited, the plurality of cooling medium flow grooves 28 spread radially from the third supply holes 22e toward the power generation region PG, extend parallel to each other in the power generation region PG, and converge counter-radially from the power generation region PG toward the third discharge holes 22f. As a result, the cooling medium supplied from the third supply manifold 24e to each fuel cell 10 is guided from the third supply holes 22e along the cooling medium flow grooves 28 and supplied to the entire back surface of the power generation region PG. The cooling medium that has passed through the back surface of the power generation region PG is guided along the cooling medium flow grooves 28 and sent from the third discharge holes 22f to the third discharge manifold 24f. The cooling medium then passes through the third discharge manifold 24f and is sent out of the fuel cell stack 1.

[0021] As shown in Figures 3 and 4, a gasket 25 is disposed on each of the gas flow surface and the cooling medium flow surface of the anode-side separator 12, separating the flow paths of the raw material gas, oxidizing gas, and cooling medium. Furthermore, a surface treatment film 27 is applied to the surface of the metal base material 23 in the power generation region PG on each of the gas flow surface and the cooling medium flow surface of the anode-side separator 12. The surface treatment film 27 is not particularly limited, and may be, for example, a laminated film of a titanium film that coats the surface of the metal base material 23 and a carbon film that coats the surface of the titanium film. The titanium film is provided to improve the corrosion resistance of the fuel cell 10. The carbon film is provided to improve the electrical conductivity of the fuel cell 10.

[0022] Although the cathode side separator 16 is not shown in the figure, a plurality of gas flow grooves are formed on the gas flow surface of the cathode side separator 16, extending from the second supply hole 22c through the power generation region PG to the second discharge hole 22d, and a plurality of cooling medium flow grooves are formed on the cooling medium flow surface of the cathode side separator 16, extending from the third supply hole 22e through the back surface of the power generation region PG to the third discharge hole 22f. When the cathode-side separator 16 and the anode-side separator 12 are common components, the cathode-side separator 16 is arranged in the opposite stacking direction to the anode-side separator 12, so that the multiple gas flow grooves 26 (see FIG. 3) formed on the gas flow surface can extend from the second supply hole 22c through the power generation region PG to the second discharge hole 22d, and the multiple cooling medium flow grooves 28 (see FIG. 4) formed on the cooling medium flow surface can extend from the third supply hole 22e through the back surface of the power generation region PG to the third discharge hole 22f.

[0023] Returning to FIG. 1, a sealing plate 5 is provided between the cell unit 4 and the cathode-side terminal 6. The sealing plate 5 is a conductive plate provided in contact with the cathode-side end face of the cell unit 4, i.e., the cooling medium flow surface of the cathode-side separator 16. The sealing plate 5 is formed using either the anode-side separator 12 or the cathode-side separator 16. However, the separator used for the sealing plate 5 differs from the anode-side separator 12 or the cathode-side separator 16 in that it does not have the six through-holes 22a-22f formed therein.

[0024] FIG. 5 shows the cooling medium flow surface of the sealing plate 5. The positions of the six through holes 22a-22f present in the anode-side separator 12 and the cathode-side separator 16 are indicated by dashed lines. As shown in FIG. 5, the six through holes 22a-22f are not formed in the sealing plate 5. Therefore, the sealing plate 5 can seal each of the manifolds 24a, 24b, 24c, 24d, 24e, and 24f formed in the cell unit 4 in the stacking direction. This allows the fuel gas, oxidizing gas, and cooling medium to flow back and forth within the cell unit 4 in the stacking direction.

[0025] The sealing plate 5 is manufactured by omitting the process of forming the six through-holes 22a-22f in the metal substrate 23 from the processes of manufacturing the anode-side separator 12 and the cathode-side separator 16. More specifically, the manufacturing process of the anode-side separator 12 and the cathode-side separator 16 includes a pressing process of pressing the metal substrate 23 to form the gas flow grooves 26 and the coolant flow grooves 25, a punching process of punching the metal substrate 23 to form the six through-holes 22a-22f, and a coating process of applying a surface treatment film 27 to an area of ​​the surface of the metal substrate 23 corresponding to the power generation region PG. The sealing plate 5 is manufactured by omitting the punching process from these processes. As such, the sealing plate 5 is a common component with the anode-side separator 12 or the cathode-side separator 16, except for the presence or absence of the six through-holes 22a-22f. Therefore, the fuel cell stack 1 can be manufactured using a small number of components, and therefore has a structure that can be manufactured at low manufacturing costs. The sealing plate 5 may be a metal base material 23 manufactured without the punching and coating steps.

[0026] Furthermore, the surface treatment film 27 coated on the coolant flow surface of the metal substrate 23 of the sealing plate 5 is present within the power generation region PG, but is not present in the manifold sealing portion, which is the area corresponding to the positions of the six through holes 22a-22f (the area surrounded by dashed lines in FIG. 5 ). Here, consider a case where the surface treatment film 27 is coated on the entire coolant flow surface of the metal substrate 23 of the sealing plate 5. The sealing plate 5 is provided in contact with the cathode-side end face of each of the two end faces of the cell unit 4 in the stacking direction. When the cell unit 4 generates electricity, a large voltage equivalent to the voltage generated by the entire cell unit 4 is applied to the manifold sealing portion of the sealing plate 5 via the liquid (e.g., cooling water, product water) flowing through the manifold. Typically, defects exist in the surface treatment film 27. Therefore, if the surface treatment film 27 is present in the manifold sealing portion, local corrosion originating from the defects may progress, resulting in the formation of corrosion holes in the sealing plate 5. On the other hand, in the sealing plate 5 of this embodiment, the surface treatment film 27 is not present in the manifold sealing portion. Therefore, in the sealing plate 5 of this embodiment, high-speed corrosion originating from defects does not occur, and therefore it is possible to suppress a decrease in reliability due to corrosion.

[0027] Although several specific examples have been described in detail above, these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and alterations of the specific examples exemplified above. The technical elements described in this specification or drawings exhibit technical utility either alone or in combination. [Explanation of symbols]

[0028] 1: fuel cell stack, 2: anode side end plate, 3: anode side terminal, 4: cell section, 5: sealing plate, 6: cathode side terminal, 7: insulator, 8: cathode side end plate, 10: fuel cell, 12: anode side separator, 14: support frame, 16: cathode side separator

Claims

1. A fuel cell stack, a cell section having a plurality of fuel cell units stacked in a stacking direction, each of the plurality of fuel cell units having a support frame supporting a membrane electrode gas diffusion layer assembly and a pair of separators sandwiching the support frame in the stacking direction; a sealing plate provided opposite one of both end faces of the cell portion in the stacking direction, each of the plurality of fuel cell units has a plurality of through holes formed therein that constitute manifolds through which a fuel gas, an oxidizing gas, and a cooling medium flow, respectively, when observed in the stacking direction; When observed in the stacking direction, the sealing plate does not have a through hole formed in an area overlapping with the manifold, A fuel cell stack, wherein the sealing plate is formed using a base material that is common to one of the pair of separators except for the presence or absence of the plurality of through holes.

2. 2. The fuel cell stack according to claim 1, wherein the sealing plate is provided opposite one of both end faces of the cell portion on the cathode side.

3. the sealing plate has a surface treatment film coated on the surface of the base material, the surface treatment film is formed on at least a part of the surface of the substrate that faces the cathode-side end face of the cell portion, 3. The fuel cell stack according to claim 2, wherein, when observed in the stacking direction, the surface treatment film does not cover an area overlapping with the manifold, but covers an area overlapping with the membrane electrode gas diffusion layer assembly.

4. the substrate includes a stainless steel substrate, The fuel cell stack according to claim 3 , wherein the surface treatment film includes a titanium film.

5. 5. The fuel cell stack according to claim 1, wherein the sealing plate is in contact with the separator that constitutes the one end face of the cell portion.

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