fuel cell stack

Abstract

A fuel cell stack capable of suppressing misalignment between fuel cell units is provided. [Solution] A fuel cell stack comprising at least a plurality of fuel cell cells and an inter-cell sealing material sandwiched between the plurality of fuel cell cells, wherein the plurality of fuel cell cells have ribs that contact the inter-cell sealing material, and the ribs are shaped so that opposing ribs of adjacent fuel cell cells interdigitate with each other across the inter-cell sealing material.

Description

[Technical Field]

[0001] The present disclosure relates to a fuel cell stack in which a plurality of fuel cells are stacked. [Background technology]

[0002] Patent Document 1 discloses a fuel cell stack in which adhesive sheets are arranged between fuel cell cells in a structure in which fuel cell cells are stacked. Patent Document 2 discloses a fuel cell separator in which ribs for gas flow paths are provided with irregularities. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-135771 [Patent Document 2] Japanese Patent Application Laid-Open No. 2017-111985 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventionally, prevention of misalignment between fuel cells has relied solely on the frictional force between the fuel cells and the adhesive sheet, and misalignment occurs between the fuel cells when a strong force is applied.

[0005] In view of the above problems, an object of the present disclosure is to provide a fuel cell stack that can suppress the occurrence of misalignment between fuel cells. [Means for solving the problem]

[0006] The present application discloses a fuel cell stack comprising at least a plurality of fuel cell cells and an inter-cell sealing material sandwiched between the plurality of fuel cell cells, wherein the plurality of fuel cell cells have ribs that contact the inter-cell sealing material, and the ribs are shaped so that opposing ribs of adjacent fuel cell cells interdigitate with each other across the inter-cell sealing material.

[0007] The ribs may have inclined surfaces, and opposing ribs may be configured to engage with each other at their inclined surfaces. [Effects of the Invention]

[0008] According to the present disclosure, the interlocking structure is added to the frictional force between the fuel cell and the inter-cell seal, making it possible to suppress displacement of the fuel cell even when a stronger force is applied. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an exploded perspective view of a fuel cell 10. FIG. [Figure 2] FIG. 2 is a plan view of the fuel cell 10. As shown in FIG. [Figure 3] FIG. 3 is a conceptual diagram illustrating the layer structure of the power generation section 11 of the fuel cell 10. As shown in FIG. [Figure 4] FIG. 4 is a conceptual diagram illustrating the layer structure in the outer peripheral portion 21 of the fuel cell 10. As shown in FIG. [Figure 5] FIG. 5 is a diagram illustrating another example of the rib. [Figure 6] FIG. 6 is a conceptual diagram illustrating the structure of the fuel cell stack 50. As shown in FIG. [Figure 7] FIG. 7 is a diagram illustrating the outer periphery of the stacked structure of the fuel cell units 10 in the fuel cell stack 50. In FIG. DETAILED DESCRIPTION OF THE INVENTION

[0010] 1. Fuel cell 1 to 4 show diagrams illustrating a fuel cell 10 according to one embodiment. The fuel cell 10 is a unit element for generating electricity by supplying hydrogen and oxygen (air), and a plurality of such fuel cell 10 are stacked to form a fuel cell stack. Fig. 1 is an exploded perspective view of the fuel cell 10, and Fig. 2 is a plan view of the fuel cell 10. Fig. 3 is a diagram illustrating the layer structure of the power generation section 11 of the fuel cell 10, and Fig. 4 is a diagram illustrating the layer structure of the outer peripheral section 21 of the fuel cell 10. In each figure, arrows indicate the directions of a three-dimensional Cartesian coordinate system. Here, the x direction is the in-plane direction of the overall flat fuel cell, with the direction from the fluid inlet to the outlet and the y direction perpendicular to the x direction. The z direction is the stacking direction of the components of the stacked fuel cell.

[0011] 1.1.Power Generation Unit The power generation section 11 is a section that contributes to power generation, for example, in the area surrounded by a dotted line in FIG. 2, and is formed by laminating multiple layers, as shown in FIG. 3, which shows the layer structure of the power generation section 11 (part of the AA cross section). In the power generation section 11 of the fuel cell 10, one side of the electrolyte membrane 12 is a cathode (oxygen supply side) and the other side is an anode (hydrogen supply side). The cathode has a cathode catalyst layer 13, a cathode diffusion layer 14, and a cathode separator 15 stacked in this order from the electrolyte membrane 12 side. On the other hand, the anode has an anode catalyst layer 16, an anode diffusion layer 17, and an anode separator 18 stacked in this order from the electrolyte membrane 12 side. The stack of the electrolyte membrane 12, cathode catalyst layer 13, cathode diffusion layer 14, anode catalyst layer 16, and anode diffusion layer 17 is sometimes called a membrane electrode assembly. The thickness of the membrane electrode assembly is typically about 0.4 mm, and the thickness of the fuel cell 10 in the power generation section 11 is typically about 1.3 mm. Each layer can be constructed as known in the art, for example as follows.

[0012] 1.1a. Electrolyte membrane The electrolyte membrane 12 is a solid polymer thin film that exhibits good proton conductivity in a wet state. For example, it is made of a fluorine-based ion exchange membrane, and for example, a carbon-fluorine-based polymer, such as a perfluoroalkylsulfonic acid-based polymer (Nafion (registered trademark)), can be used. The thickness of the electrolyte membrane 12 is not particularly limited, but is 100 μm or less, preferably 50 μm or less, and more preferably 10 μm or less.

[0013] 1.1b. Cathode catalyst layer The cathode catalyst layer 13 is a layer containing a catalyst metal supported on a carrier. Examples of the catalyst metal include Pt, Pd, Rh, and alloys containing these. Examples of the carrier include carbon carriers, more specifically, carbon particles made of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, etc.

[0014] 1.1c. Anode catalyst layer Like the cathode catalyst layer 13, the anode catalyst layer 16 is a layer containing a catalyst metal supported on a carrier. Examples of the catalyst metal include Pt, Pd, Rh, and alloys containing these. Examples of the carrier include carbon carriers, more specifically, carbon particles made of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, etc.

[0015] 1.1d. Cathode diffusion layer The cathode diffusion layer 14 can be made of, for example, a conductive porous material. More specific examples include porous carbon materials (carbon paper, carbon cloth, glassy carbon, etc.) and porous metal materials (metal mesh, metal foam). The cathode diffusion layer may be provided with an MPL (microporous layer) if necessary. The MPL is a thin coating applied to the cathode catalyst layer 13 side of the cathode diffusion layer 14. The MPL has water-repellent or hydrophilic properties as needed to regulate moisture. MPLs are typically made primarily of a water-repellent resin such as polytetrafluoroethylene (PTFE) and a conductive material such as carbon black.

[0016] 1.1e. Anode diffusion layer The anode diffusion layer 17 can be made of, for example, a conductive porous material. More specific examples include porous carbon materials (carbon paper, carbon cloth, glassy carbon, etc.) and porous metal materials (metal mesh, metal foam).

[0017] 1.1f. Cathode separator The cathode separator 15 is a member that supplies a reactant gas (air in this embodiment) to the cathode diffusion layer 14, and has a plurality of grooves 15a on the surface facing the cathode diffusion layer 14, which function as reactant gas flow paths. The shape of the grooves is not particularly limited as long as it can appropriately supply the reactant gas to the cathode diffusion layer 14, and examples include a plate-like member formed into a corrugated shape, as in this embodiment. In this case, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the irregularities is typically about 0.5 mm. In the case of a wavy shape, grooves 15b are formed between adjacent grooves 15a on the opposite side of the cathode separator 15, and these function as cooling water flow paths.

[0018] As can be seen from FIG. 1, the cathode separator 15 has an air inlet hole A at a position extending outward from the power generating section 11 and at one end of the grooves 15a and 15b. in , cooling water inlet hole W in , hydrogen outlet hole H out and an air outlet hole A is provided at the other end of the groove 15a and the groove 15b. out , cooling water outlet hole W out , hydrogen inlet hole H in Here, the groove 15a is the air inlet hole Ain , air outlet hole A out The groove 15b is connected to the cooling water inlet hole W in , cooling water outlet hole W out It is connected to.

[0019] The material constituting the cathode separator 15 may be any material that can be used as a separator for a fuel cell, and may be a gas-impermeable conductive material. Examples of such materials include dense carbon made by compressing carbon to make it gas-impermeable, and a press-molded metal plate.

[0020] 1.1g. Anode separator The anode separator 18 is a member that supplies a reactant gas (hydrogen) to the anode diffusion layer 17, and has a plurality of grooves 18a on the surface facing the anode diffusion layer 17, which function as reactant gas flow paths. The shape of the grooves is not particularly limited as long as they can properly supply the reactant gas to the anode diffusion layer 17, and examples include a type in which a plate-like member is formed into a corrugated shape, as in this embodiment. In this case, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the irregularities is typically about 0.4 mm. In the case of a wavy shape, in this embodiment, grooves 18b are formed between adjacent grooves 18a on the opposite side of the anode separator 18, and these function as cooling water flow paths.

[0021] As can be seen from FIG. 1, the anode separator 18 has an air inlet hole A at a position extending outward from the power generation section 11 and at one end of the grooves 18a and 18b. in , cooling water inlet hole W in , hydrogen outlet hole H out and an air outlet hole A is provided at the other end of the groove 18a and the groove 18b. out , cooling water outlet hole W out , hydrogen inlet hole H in Here, the groove 18a is provided with a hydrogen inlet hole H in , hydrogen outlet hole H out The groove 18b is connected to the cooling water inlet hole W in , cooling water outlet hole W out It is connected to.

[0022] The material constituting the anode separator 18 may be any material that can be used as a separator for a fuel cell, and may be a gas-impermeable conductive material. Examples of such materials include dense carbon made by compressing carbon to make it gas-impermeable, and a press-molded metal plate.

[0023] 1.1h. Power generation by the power generation unit As is well known, power generation is performed by the fuel cell 10 described above as follows. When hydrogen is supplied from the grooves 18a of the anode separator 18, the hydrogen passes through the anode diffusion layer 17 and is converted into protons (H + ) and electrons (e - ), the protons pass through the electrolyte membrane 12, and the electrons pass through conductive wires connected to the outside, and each reaches the cathode catalyst layer 13. Here, oxygen (air) is supplied to the cathode catalyst layer 13 from the grooves 15a in the cathode separator 15 via the cathode diffusion layer 14, and water (H2O) is generated in the cathode catalyst layer 13 by the protons, electrons, and oxygen. The generated water passes through the cathode diffusion layer 14, reaches the grooves 15a in the cathode separator 15, and is discharged. That is, in the fuel cell 10, the flow of electrons passing through the conductive wire connecting the anode catalyst layer 16 to the outside is used as an electric current.

[0024] 1.2.Outer periphery The outer peripheral portion 21 is located outside the power generation portion 11 enclosed by the dotted line in Fig. 2, and is the outer peripheral portion of the fuel cell 10. It does not contribute to power generation, but is a portion that supplies various fluids to the power generation portion, collects fluids from the power generation portion, and provides sealing. The outer peripheral portion 21 is formed by laminating multiple layers, as shown in Fig. 4, which shows the layer structure (BB cross section) of the outer peripheral portion 21. Specifically, in this embodiment, the outer peripheral portion 21 has the following configuration.

[0025] In the outer peripheral portion 21, a resin sheet 23 is disposed between the cathode separator 15 and the anode separator 18, and the inside of the fuel cell 10 is sealed by the resin sheet 23. As can be seen from Figure 1, the resin sheet 23 is disposed so as to surround the membrane electrode assembly. The resin sheet 23 functions as a sealing member that seals the gap between the cathode separator 15 and the anode separator 18 at the outer periphery 21 of the fuel cell 10 . The resin sheet 23 includes a base material 24, an adhesive layer 25 disposed on one surface (the surface on the cathode separator side) of the base material 24, and an adhesive layer 26 disposed on the other surface (the surface on the anode separator side) of the base material 24. The adhesive layer 25 is adhered to the cathode separator 15, and the adhesive layer 26 is adhered to the anode separator 18, thereby sealing the inside of the power generation section 11.

[0026] The substrate 24 is made of a thermoplastic resin material that is electrically insulating and airtight and has a relatively high melting point. Examples of such materials include polyethylene naphthalate, polyphenylene ether, and polyphenylene sulfide. The thickness of the substrate 24 is not particularly limited, but is preferably 0.05 mm or more and 0.25 mm or less. The adhesive layers 25 and 26 are made of an adhesive and a pressure sensitive adhesive.

[0027] Furthermore, ribs 30 and 31, which are protrusions that protrude in the z direction, are provided on the outer periphery 21 of the cathode separator 15 and the anode separator 18, respectively. The form of the ribs 30 and 31 is not particularly limited as long as they are protrusions, but for example, in the case where the cathode separator 15 and the anode separator 18 are formed by corrugating plates as described above, the ribs 30 and 31 can also be protrusions based on the concave and convex portions that form the grooves 15a and grooves 18a.

[0028] In the present disclosure, the ribs 30 and 31 are provided with engaging portions 30a and 31a on the surfaces of the ribs 30 and 31 opposite to the side on which the resin sheet 23 is arranged, i.e., on the surfaces that face the adjacent fuel cell 10 when multiple fuel cell units 10 are stacked to form a fuel cell stack. In this embodiment, the engaging portions 30a and 31a are engaging protrusions that protrude in the z direction. The engaging portions 30a and 31a are configured so that their vertices are positioned differently when the fuel cell 10 is viewed from above (as viewed from the z direction, as viewed from the arrow C in FIG. 4). As a result, as will be described later, when an adjacent fuel cell 10 moves relatively in the y direction, the engaging portions 30a and 31a engage with each other so as to mesh with each other via the inter-cell sealing material 40, thereby preventing misalignment in the y direction.

[0029] The shape of the engaging portions 30a and 31a is not particularly limited, and when they are protrusions, they may be rectangular, triangular, other polygonal, semicircular, semi-elliptical, etc. Among these, in this embodiment, the engaging portions 30a and 31a of the adjacent interlocking fuel cell units 10 are trapezoidal, with the interlocking surfaces provided with inclined surfaces 30b and 31b inclined with respect to the y direction. These inclined surfaces 30b and 31b make it easy to generate a reaction force against misalignment in the y direction.

[0030] FIG. 5 shows an example in which the tops of the ribs 30 and 31 are all made into engaging portions 30a and 30b, which are inclined surfaces.

[0031] In the outer circumferential portion 21, an inter-cell sealant 40 is further laminated on one of the separators (cathode separator 15 in this embodiment) of the fuel cell 10. Therefore, the inter-cell sealant 40 is laminated so as to contact the tops of the ribs 30, particularly the engagement portions 30a.

[0032] Therefore, the inter-cell sealant 40 is a frame-shaped sheet member arranged along the outer periphery 21, as shown in Figures 1 and 2 (shown by hatching in Figure 2). The inter-cell sealant 40 is preferably made of an elastic material, as it should have sealing properties as well as flexibility. The specific material of the elastic material is not particularly limited, but examples include ethylene propylene rubber, fluorine-based rubber, and silicone-based rubber.

[0033] As will be described later, when multiple fuel cell cells 10 are stacked in a fuel cell stack, misalignment is likely to occur due to dimensional tolerances and lamination tolerances when the separators come into contact with each other, and the ribs may not interlock as intended. In contrast, by using the inter-cell sealant 40, the dimensional tolerances and lamination tolerances can be absorbed by the inter-cell sealant 40, allowing for more effective interlocking between the cells and suppressing relative movement of the fuel cell cells.

[0034] 2. Fuel cell stack 2.1.Overall structure The fuel cell stack 50 is a member formed by stacking a plurality of the above-described fuel cell units 10 (approximately 50 to 400 units), and collects electricity from the plurality of fuel cell units 10. An outline of the configuration is shown in Figure 6. The fuel cell stack 50 includes a stack case 51, end plates 52, a plurality of fuel cell units 10, current collector plates 54, and biasing members 55.

[0035] The stack case 51 is a housing that houses a plurality of stacked fuel cell units 10, current collector plates 54, and biasing members 55. In this embodiment, the stack case 51 is a rectangular cylinder that is open at one end and closed at the other end, and has a plate-like piece that protrudes along the edge of the opening to the opposite side of the opening, forming a flange 51a.

[0036] The end plate 52 is a plate-shaped member that closes the opening of the stack case 51. The end plate 52 is fixed to the stack case 51 with bolts, nuts, etc. at the portion where it overlaps with the flange 51a of the stack case 51 so as to cover the stack case 51.

[0037] The fuel cell 10 is as described above. A plurality of such fuel cells 10 are stacked. At this time, the anode separator 18 of one fuel cell 10 is arranged so as to overlap the cathode separator 15 of the adjacent fuel cell 10. The grooves 15b of the cathode separator 15 and the grooves 18b of the anode separator 18 overlap to form a cooling water flow path.

[0038] The current collector plate 54 is a member that collects current from the stacked fuel cell cells 10. Therefore, the current collector plate 54 is disposed at each end in the stacking direction of the stack of fuel cell cells 10, one serving as a positive electrode and the other as a negative electrode. Terminals (not shown) are connected to this current collector plate 54, and it is configured so that it can be electrically connected to the outside.

[0039] The biasing member 55 is housed inside the stack case 51 and applies a pressing force in the stacking direction to the stack of fuel cells 10. An example of the biasing member is a disc spring.

[0040] 2.2.Laminated structure in the outer periphery Figure 7 shows the stack structure of the fuel cell stack 50, focusing on the outer periphery 21 of the fuel cell 10. Figure 7 shows the fuel cell 10 from the perspective of Figure 4, and shows that these are stacked (two adjacent fuel cell 10 in Figure 7).

[0041] 7, in the outer peripheral portion 21 of the stacked fuel cells 10 in the fuel cell stack 50, adjacent fuel cells 10 are stacked with the inter-cell sealant 40 sandwiched between them. At this time, the engagement portion 30a of the rib 30 of one adjacent fuel cell 10 and the engagement portion 31a of the rib 31 of the other adjacent fuel cell 10 bite into the inter-cell sealant 40 from the opposite side of the inter-cell sealant 40, and are positioned so that the ribs 30 and 31 partially overlap when viewed from the y direction. This allows the opposing ribs 30 and 31 to engage with each other via the inter-cell sealant 40 between the adjacent fuel cells 10. For example, referring to Figure 7, when the fuel cell 10 on the upper side of the paper moves in the direction of arrow D, the engaging portion 31a of the rib 31 at the area surrounded by the dotted ellipse in Figure 7 moves in the same direction as arrow D, and engages with the engaging portion 30a of the rib 30 provided on the fuel cell 10 on the lower side of the paper via the inter-cell sealing material 40, preventing further movement of the fuel cell 10 on the upper side of the paper. Therefore, according to this embodiment, in addition to the suppression of movement due to frictional forces between the fuel cell and the inter-cell seal, the above-mentioned interlocking structure also hinders movement, making it possible to suppress misalignment of the fuel cell even when a strong force is applied to the fuel cell. In addition, the portion shown in Figure 7 is effective against movement in the direction indicated by arrow D, but for movement in the opposite direction and in other directions, the meshing applied to the movement direction occurs in other portions not shown in Figure 7, appropriately suppressing misalignment of the fuel cell cells.

[0042] At this time, the opposing engaging portions 30a and 31a mesh with each other at the inclined surfaces 30b and 31b, which tends to generate a reaction force against the movement direction, thereby more effectively suppressing the occurrence of the misalignment. Furthermore, when multiple fuel cell cells 10 are stacked in a fuel cell stack, contact between the separators is prone to misalignment due to dimensional tolerances and stacking tolerances. By using the inter-cell sealant 40 in this manner, the dimensional tolerances and stacking tolerances can be absorbed by the inter-cell sealant 40, and relative movement between the cells can be more effectively suppressed. [Explanation of symbols]

[0043] 10... fuel cell, 11... power generation section, 15... cathode separator, 18... anode separator, 21... outer periphery, 23... resin sheet, 30, 31... ribs, 30a, 31a... engagement section, 40... inter-cell seal material, 50... fuel cell stack

Claims

1. A fuel cell stack including at least a plurality of fuel cell units and an inter-cell sealant sandwiched between the plurality of fuel cell units, the plurality of fuel cell units have ribs that contact the inter-cell sealant, The ribs are shaped so that the ribs facing each other in adjacent fuel cell units with the inter-cell seal material interposed therebetween can mesh with each other. Fuel cell stack.

2. 2. The fuel cell stack according to claim 1, wherein the rib has an inclined surface, and the opposing ribs are structured so as to engage with each other at the inclined surface.

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