fuel cell

Abstract

To provide a fuel cell that can suppress the occurrence of gas leaks. [Solution] A fuel cell having an electrode body between a pair of separators, comprising a gasket disposed on the side of the separator opposite to the side on which the electrode body is arranged, and a convex member disposed on the side of one of the pair of separators opposite to the side on which the electrode body is arranged, wherein the convex member is positioned closer to the outer peripheral edge of the separator than the gasket, and the height of the convex member is smaller than the height of the gasket.

Description

[Technical Field]

[0001] This disclosure relates to fuel cell cells. [Background technology]

[0002] Patent Document 1 discloses a fuel cell having two separators, a frame member and a membrane electrode assembly disposed between them, and a gasket is provided between the first fuel cell cell and the second fuel cell cell to prevent leakage of reaction gas. Patent Document 2 discloses a short-circuit prevention structure for a fuel cell cell in which a gasket and an insulator are provided on one side of the separator, with the gasket located in the peripheral region of the gasket. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2018-181604 [Patent Document 2] Japanese Patent Publication No. 2011-129267 [Overview of the project] [Problems that the invention aims to solve]

[0004] When two separators, a frame member, and a membrane electrode assembly are joined together by a heated press to form a fuel cell, the fuel cell becomes warped. Therefore, when multiple fuel cell cells are stacked to form a fuel cell (sometimes called a fuel cell stack), the amount of compression of the gasket placed as a sealing material between adjacent fuel cell cells decreases, which can lead to gas leakage. In particular, as the stacking direction of the fuel cell cells, the pitch of the fuel cell cells widens from one end (the side where compression force is applied) to the other end, so the amount of compression of the gasket decreases at the other end, making gas leakage more likely.

[0005] In light of the above issues, this disclosure aims to provide a fuel cell cell that can suppress the occurrence of gas leaks.

Means for Solving the Problem

[0006] The present application relates to a fuel cell having an electrode body between a pair of separators, comprising a gasket disposed on a surface of the separator opposite to the surface on which the electrode body is disposed, and a convex member disposed on a surface of one of the pair of separators opposite to the surface on which the electrode body is disposed. The convex member is disposed closer to the outer peripheral edge of the separator than the gasket, and the height of the convex member is smaller than the height of the gasket. A fuel cell is disclosed.

[0007] The convex member may be disposed on the same surface of one of the separators as the surface on which the gasket is disposed.

[0008] The convex member may be disposed on a surface of one of the separators opposite to the surface on which the gasket is disposed.

[0009] The convex member may be made of the same material as the gasket.

Advantages of the Invention

[0010] According to the present disclosure, since the reduction in the compression amount of the gasket due to the convex member is small, gas leakage can be suppressed.

Brief Description of the Drawings

[0011] [Figure 1] FIG. 1 is an exploded perspective view of a fuel cell 10. [Figure 2] FIG. 2 is a plan view of the fuel cell 10. [Figure 3] FIG. 3 is a conceptual diagram for explaining the layer structure of the power generation unit 11 of the fuel cell 10. [Figure 4] FIG. 4 is a conceptual diagram for explaining the layer structure of the outer peripheral portion 21 of the fuel cell 10. [Figure 5] FIG. 5 is another exemplary embodiment regarding the arrangement of the convex member 46. [Figure 6] FIG. 6 is another exemplary embodiment regarding the arrangement of the convex member 46. [Figure 7] FIG. 7 is a conceptual diagram for explaining the structure of the fuel cell stack 50.

BEST MODE FOR CARRYING OUT THE INVENTION

[0012] 1. Fuel Cell FIGS. 1 to 4 show diagrams for explaining 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 cells 10 are stacked to form a fuel cell. FIG. 1 is an exploded perspective view of the fuel cell 10, and FIG. 2 is a plan view of the combustion cell 10. Further, FIG. 3 is a diagram for explaining the layer structure in the power generation part 11 of the fuel cell 10, and FIG. 4 is a diagram for explaining the layer structure in the outer peripheral part 21 (the part where the convex member 46 is arranged) of the fuel cell 10. Each figure represents each direction of the three-dimensional orthogonal coordinate system by an arrow. Here, in the in-plane direction of the fuel cell which is flat as a whole, the x direction is the direction from the inlet side to the outlet side of the fluid, and the y direction is the direction orthogonal to the x direction. The z direction is the stacking direction of each member of the fuel cell having a stacked structure.

[0013] 1.1. Power Generation Part The power generation part 11 is a part that contributes to power generation, for example, in the part surrounded by a dotted line in FIG. 2, and as shown in FIG. 3 representing the layer structure (a part of the A-A cross section) in the power generation part 11, a plurality of layers are stacked. In the power generation section 11 of the fuel cell cell 10, one side of the electrolyte membrane 12 is the cathode (oxygen supply side), and the other side is the anode (hydrogen supply side). The cathode consists of a cathode catalyst layer 13, a cathode diffusion layer 14, and a cathode separator 15 stacked in that order from the electrolyte membrane 12 side. The anode, on the other hand, consists of an anode catalyst layer 16, an anode diffusion layer 17, and an anode separator 18 stacked in that order from the electrolyte membrane 12 side. The stacked structure 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 cell 10 in the power generation section 11 is typically about 1.3 mm. The cathode separator 15 and the anode separator 18 form a pair of separators, and the membrane electrode assembly is placed between them. Each layer can be configured in a known way, for example, as follows:

[0014] 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 composed of a fluorine-based ion exchange membrane, and carbon-fluorine polymers can be used, specifically perfluoroalkylsulfonic acid polymers (Nafion®), etc. 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.

[0015] 1.1b. Cathode catalyst layer The cathode catalyst layer 13 is a layer containing a catalyst metal in the form of the catalyst metal being supported on a carrier. For example, the catalyst metal can be Pt, Pd, Rh, or alloys containing these. The carrier can be a carbon carrier, more specifically carbon particles consisting of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0016] 1.1c. Anode catalyst layer The anode catalyst layer 16, like the cathode catalyst layer 13, is a layer containing a catalyst metal in the form of the catalyst metal supported on a support. For example, the catalyst metal can be Pt, Pd, Rh, or alloys containing these. The support can be a carbon support, more specifically carbon particles consisting of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0017] 1.1d. Cathode Diffusion Layer The cathode diffusion layer 14 can be made of, for example, a conductive porous material. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal). A microporous layer (MPL) may be provided in the cathode diffusion layer as needed. The MPL is a thin film coating applied to the cathode catalyst layer 13 side of the cathode diffusion layer 14. The MPL has the function of regulating moisture by being water-repellent or hydrophilic as needed. Typical MPLs consist mainly of a water-repellent resin such as polytetrafluoroethylene (PTFE) and a conductive material such as carbon black.

[0018] 1.1e. Anode Diffusion Layer The anode diffusion layer 17 can be made of, for example, a conductive porous material. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal).

[0019] 1.1f. Cathode Separator The cathode separator 15 forms a pair of separators with the anode separator 18, and is a member that supplies the reaction gas (air in this form) to the cathode diffusion layer 14. It has a plurality of grooves 15a on the surface facing the cathode diffusion layer 14, and these grooves function as reaction gas flow paths. The shape of the grooves is not particularly limited as long as the reaction gas can be appropriately supplied to the cathode diffusion layer 14. Examples include a type in which a plate-like member is formed into a wave shape as in this embodiment. At that time, the plate thickness is typically 0.1 mm to 0.2 mm, and the height of the unevenness is typically about 0.5 mm. When it is wave-shaped, grooves 15b are formed on the opposite side across the cathode separator 15 between adjacent grooves 15a, and these function as cooling water flow paths.

[0020] Also, as can be seen from FIG. 1, in the cathode separator 15, at a position extending from the power generation unit 11 to the outside, at a portion that is one end side of the grooves 15a and grooves 15b, there is an air inlet hole A in , a cooling water inlet hole W in , a hydrogen outlet hole H out are provided, and at a portion that is the other end side of the grooves 15a and grooves 15b, there are an air outlet hole A out , a cooling water outlet hole W out , a hydrogen inlet hole H in are provided. Here, the groove 15a communicates with the air inlet hole A in , the air outlet hole Aout, and the groove 15b communicates with the cooling water inlet hole W in , the cooling water outlet hole W out .

[0021] The material constituting the cathode separator 15 may be any material that can be used as a separator of a fuel cell, and may be a gas-impermeable conductive material. Examples of such materials include dense carbon obtained by compressing carbon to make it gas-impermeable, and a press-molded metal plate, etc.

[0022] 1.1 g. Anode separator The anode separator 18, together with the cathode separator 15, forms a pair of separators and is a component that supplies reaction gas (hydrogen) to the anode diffusion layer 17. It has a plurality of grooves 18a on the surface facing the anode diffusion layer 17, and these grooves function as reaction gas channels. The shape of the grooves is not particularly limited as long as the reaction gas can be properly supplied to the anode diffusion layer 17, and examples include a plate-shaped component formed in a corrugated shape, as in this embodiment. In that 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, a groove 18b is formed on the opposite side of the adjacent groove 18a, with an anode separator 18 in between, and this functions as a cooling water channel.

[0023] Furthermore, as can be seen in Figure 1, the anode separator 18 has an air inlet hole A at one end of grooves 18a and 18b, located at a position that extends outward from the power generation unit 11. in , cooling water inlet hole W in , hydrogen outlet hole H out An air outlet hole A is provided at the other end of groove 18a and groove 18b. out , cooling water outlet hole W out , hydrogen inlet H in A groove 18a is provided. Here, the groove 18a is the hydrogen inlet hole H in , hydrogen outlet hole H out It is connected to the cooling water inlet hole W, and groove 18b is connected to the cooling water inlet hole W. in , cooling water outlet hole W out It is connected to [the other device].

[0024] The material constituting the anode separator 18 may be any material that can be used as a separator in a fuel cell cell, and may be a gas-impermeable conductive material. Examples of such materials include dense carbon that has been compressed to be gas-impermeable, and press-formed metal plates.

[0025] 1.1h. Power generation by the power generation unit As is well known, the fuel cell cell 10 described above generates electricity as follows. When hydrogen is supplied from the groove 18a of the anode separator 18, the hydrogen passes through the anode diffusion layer 17 and is converted into protons (H) in the anode catalyst layer 16. + ) and electrons (e - The protons are broken down into electrons and electrons, and the protons pass through the electrolyte membrane 12, while the electrons pass through conductive wires leading to the outside, each reaching the cathode catalyst layer 13. Here, oxygen (air) is supplied to the cathode catalyst layer 13 from the groove 15a of 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 and reaches the groove 15a of the cathode separator 15, where it is discharged. In other words, the fuel cell cell 10 utilizes the flow of electrons through conductive wires connecting the anode catalyst layer 16 to the outside as electric current.

[0026] 1.2. Outer perimeter The outer periphery 21 is the outer periphery of the fuel cell cell 10, located outside the power generation unit 11 enclosed by a dotted line in Figure 2. Although it does not contribute to power generation, it is responsible for supplying various fluids to the power generation unit, collecting fluids from the power generation unit, and sealing. The outer periphery 21 is made up of multiple layers stacked together, as shown in Figure 4, which illustrates the layer structure (BB cross-section) of the outer periphery 21. Specifically, in this embodiment, the outer periphery 21 has the following configuration.

[0027] 1.2a. Resin sheet In the outer periphery 21, a resin sheet 23 is placed between a pair of separators, the cathode separator 15 and the anode separator 18, and the resin sheet 23 seals the inside of the fuel cell cell 10. As can be seen from Figure 1, the resin sheet 23 is arranged to surround the membrane electrode assembly. The resin sheet 23 functions as a sealing member that seals the space between the cathode separator 15 and the anode separator 18 on the outer periphery 21 of the fuel cell cell 10. The resin sheet 23 comprises a base material 24, an adhesive layer 25 positioned on one side of the base material 24 (the side facing the cathode separator), and an adhesive layer 26 positioned on the other side of the base material 24 (the side facing the anode separator). The adhesive layer 25 adheres to the cathode separator 15, and the adhesive layer 26 adheres to the anode separator 18, thereby sealing the inside of the power generation unit 11.

[0028] The base material 24 is formed from a thermoplastic resin material that has electrical insulation and airtightness and a relatively high melting point. Examples of such materials include polyethylene naphthalate, polyphenylene ether, and polyphenylene sulfide. The thickness of the base material 24 is not particularly limited, but is between 0.05 mm and 0.25 mm. The adhesive layers 25 and 26 are composed of adhesive and tack.

[0029] 1.2b. Gasket In the outer periphery 21, a gasket 40 is placed on one of the separators of the fuel cell cell 10 (cathode separator 15 in this embodiment). The gasket 40 is placed on the side of the separator opposite to the side where the membrane electrode assembly and resin sheet are placed (i.e., the side facing the adjacent fuel cell cells 10 that are stacked), and functions as a sealing material between adjacent fuel cell cells 10 when multiple fuel cell cells 10 are stacked.

[0030] The cross-sectional shape of the gasket 40 is not particularly limited as long as it is suitable for use as a gasket, but examples include those having a trapezoidal cross-section as in this embodiment. In this case, the longer lower base faces the separator. Other cross-sectional shapes include, for example, a square, a triangle, a semicircle, a semiellipse, etc.

[0031] Therefore, the gasket 40 is a frame-shaped sheet member arranged along the outer circumference 21, as shown in Figures 1 and 2 (shown with hatching in Figure 2). Since the gasket 40 should have sealing properties and flexibility, it is preferable that it be made of an elastic material. The specific material of the elastic material is not particularly limited, but examples include ethylene propylene rubber, fluorocarbon rubber, and silicone rubber.

[0032] 1.2c.Convex member In the outer periphery 21, a convex member 46 is positioned on one or both separators of the fuel cell cell 10 (in this embodiment, only the cathode separator 15, on the same surface as the gasket 40). The convex member 46 is positioned on the side of the separator opposite to the side on which the membrane electrode assembly or resin sheet is positioned (i.e., the side facing the adjacent stacked fuel cell cell 10), and in the area where the convex member 46 is positioned, the reduction in gasket compression amount due to the warping force of the fuel cell cell 10 is reduced, thereby suppressing gas leakage.

[0033] The convex member 46 is positioned closer to the edge of the separator (outside) than the gasket 40. The distance between the gasket 40 and the convex member 46 is not particularly limited, but the distance between the gasket 40 and the convex member 46 shown as G in Figure 4 is greater than 0, and as shown as W in Figure 4. G It is preferable that the width of the gasket is less than or equal to the width indicated.

[0034] Furthermore, it is preferable that the convex members 46 are arranged at least at the four corners of the separator in a plan view, as shown in Figure 2. Since the warping of the fuel cell cell 10 that occurs during the manufacturing of the fuel cell cell 10 is greater at these four corners, the effect of arranging the convex members 46 can be further enhanced. However, from the viewpoint that it is sufficient to include the four corners, the convex members 46 may also be arranged in an annular shape along the outer edge of the fuel cell cell 10, as shown in Figure 5.

[0035] Furthermore, as shown in Figure 6, the convex member 46 may be positioned on the side of the separator opposite to the gasket 40 (the side facing the resin sheet 23), provided that it is on the edge (outside) side of the separator than the gasket 40 as described above. In this embodiment, the convex member 46 is positioned at the widened end between a pair of separators. Here, it is positioned between the resin sheet 23 and the cathode separator 15, and between the resin sheet 23 and the anode separator 18.

[0036] Figure 4 shows H T The height of the convex member 46 shown is H in Figure 4. G The height shall be smaller than the height of gasket 40 shown. The height difference is not particularly limited, but H T is H G It is preferable that it be more than half of that. Also, Figure 4 shows W T The width of the convex member 46 shown is not particularly limited, but the width W of the gasket 40 G It is preferable that it be of a similar degree.

[0037] The cross-sectional shape of the convex member 46 (viewpoint in Figure 4) is preferably rectangular, with one of its long sides forming the apex surface 46a, and the apex surface is preferably flat and wide. This allows a reaction force to be obtained even with a small amount of compression of the convex member 46.

[0038] The material constituting the convex member 46 is not particularly limited, but it can be the same material as the gasket.

[0039] 1.3. Warping of fuel cell cells As described above, the fuel cell cell 10 has a pair of separators (cathode separator 15 and anode separator 18), a membrane electrode assembly for the power generation section 11, a resin sheet 23 for the outer periphery 21, and a gasket 40 and a convex member 46. Here, the fuel cell cell 10 is formed by laminating the materials that make up the fuel cell cell 10 and then joining them by heating and pressing. As a result, it has a curved shape with the cathode side facing upward (convex).

[0040] 2.Fuel cell 2.1.Overall structure The fuel cell (sometimes called a "fuel cell stack") 50 is a component made up of multiple fuel cell cells 10 (approximately 50 to 400 cells) stacked on top of each other, and collects current from multiple fuel cell cells 10. Figure 7 shows an overview of its configuration. The fuel cell stack 50 comprises a stack case 51, an end plate 52, multiple fuel cell cells 10, a current collector plate 54, and a biasing member 55.

[0041] The stack case 51 is a housing that houses multiple stacked fuel cell cells 10, current collector plates 54, and biasing members 55 inside. In this embodiment, the stack case 51 is a rectangular cylinder with one end open and the other end closed, and a plate-like piece protrudes along the edge of the opening on the opposite side of the opening, forming a flange 51a.

[0042] The end plate 52 is a plate-shaped component that closes the opening of the stack case 51. The end plate 52 is fixed to the stack case 51 by bolts and nuts, etc., so as to cover the overlapping portion of the flange 51a of the stack case 51.

[0043] The fuel cell cell 10 is as described above. Multiple such fuel cell cells 10 are stacked on top of each other. In this configuration, the anode separator 18 of an adjacent fuel cell cell 10 is positioned so that it overlaps with the cathode separator 15 of one fuel cell cell 10. The groove 15b of the cathode separator 15 and the groove 18b of the anode separator 18 then overlap to form a cooling water channel.

[0044] The current collector plate 54 is a component that collects current from the stacked fuel cell cells 10. Therefore, the current collector plate 54 is positioned at one end and the other end in the stacking direction of the stacked fuel cell cells 10, with one end being the positive electrode and the other being the negative electrode. Terminals (not shown) are connected to the current collector plate 54, allowing for electrical connection to the outside.

[0045] The biasing member 55 is housed inside the stack case 51 and applies a pressing force to the stack of fuel cell cells 10 in the stacking direction. Examples of biasing members include disc springs.

[0046] In such a fuel cell 50, as described above, the fuel cell cells 10 warp, and when multiple such fuel cell cells 10 are stacked, the spacing between the fuel cell cells 10 tends to widen (the cell pitch widens, the gasket clearance widens) from the compressed side (end plate side) toward the opposite side. In particular, the amount of gasket compression becomes insufficient in the widened area, increasing the risk of gas leakage. In response to this, by providing the convex member 46, the combined spring constant of the gasket and the convex member becomes larger than the spring constant of the gasket alone. As a result, the decrease in gasket compression amount in response to the warping reaction force of the same fuel cell is reduced, the amount the gasket clearance widens is reduced, and the occurrence of gas leakage can be suppressed. [Explanation of symbols]

[0047] 10...Fuel cell, 11...Power generation unit, 15...Cathode separator, 18...Anode separator, 21...Outer periphery, 23...Resin sheet, 40...Gasket, 46...Convex member, 50...Fuel cell

Claims

1. A fuel cell having an electrode body between a pair of separators, A gasket is disposed on the side of the separator opposite to the side on which the electrode body is arranged, The pair of separators includes a convex member disposed on the side of one of the separators opposite to the side on which the electrode body is arranged, The convex member is positioned closer to the outer peripheral edge of the separator than the gasket, and the height of the convex member is smaller than the height of the gasket. Fuel cell.

2. The fuel cell according to claim 1, wherein the convex member is located on the same surface of the one separator on which the gasket is placed.

3. The fuel cell cell according to claim 1, wherein the convex member is located on the side of the one separator opposite to the side on which the gasket is located.

4. The fuel cell cell according to any one of claims 1 to 3, wherein the convex member is made of the same material as the gasket.

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