Fuel cell unit

Abstract

A fuel cell having an electrode body between a pair of separators, the fuel cell having: a gasket disposed on a surface of the separator on the opposite side from a surface on which the electrode body is disposed; and a convex member disposed on a surface of one of the pair of separators, the surface being on the opposite side from a surface on which the electrode body is disposed, the convex member being disposed closer to the outer peripheral edge side of the separator than the gasket, and the height of the convex member being smaller than the height of the gasket.

Description

TECHNICAL FIELD

[0001] The present disclosure relates to a fuel cell unit. BACKGROUND

[0002] Japanese Patent Application Publication No. 2018-181604 discloses a fuel cell unit having two separators, and a frame member and a membrane electrode assembly disposed therebetween, a gasket that prevents leakage of a reaction gas is provided between a first fuel cell unit and a second fuel cell unit.

[0003] Japanese Patent Application Publication No. 2011-129267 discloses a short-circuit prevention structure of a fuel cell unit in which an insulator is provided in a gasket and a gasket peripheral portion region in one of the separators.

[0004] When two separators and a frame member and a membrane electrode assembly disposed therebetween are joined by heating and pressing to form a fuel cell unit, the fuel cell unit becomes in a warped state. Therefore, if a plurality of fuel cell units are stacked to form a fuel cell (sometimes referred to as a fuel cell stack), the compression amount of the gasket disposed as a sealing material between adjacent fuel cell units is lost, and gas leakage can occur. In particular, in the stacking direction of the fuel cell units, the pitch of the fuel cell units expands from one end side (a side to which an additional compression force is applied) to the other end side, so at the other end side, the compression amount of the gasket is lost, and gas leakage is likely to occur. SUMMARY

[0005] In view of the above problem, an object of the present disclosure is to provide a fuel cell unit in which gas leakage is inhibited.

[0006] The present disclosure discloses a fuel cell unit having an electrode body between a pair of separators, in which a gasket is disposed at a face of one of the pair of separators that is opposite a face of the electrode body disposed at one side, and a convex member is disposed at a face of one of the pair of separators that is opposite the face of the electrode body disposed at one side, the convex member is disposed at a position that is closer to an outer peripheral edge of the separator than the gasket, and the height of the convex member is smaller than the height of the gasket.

[0007] The convex member can be disposed at the same face of one of the separators as the face at which the gasket is disposed.

[0008] The convex member can be disposed at a face of one of the separators that is opposite the face at which the gasket is disposed.

[0009] The convex member can be the same material as the gasket.

[0010] According to the present disclosure, the compression amount loss of the gasket is reduced by the convex member, so gas leakage can be inhibited.

[0011] Features, advantages, and technical and industrial significance of exemplary embodiments of the application will be described hereinafter with reference to the accompanying drawings. Like reference numerals in different drawings denote the same element. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 is an exploded perspective view of the fuel cell unit 10.

[0013] Figure 2 is a view obtained by viewing the fuel cell unit 10 from above.

[0014] Figure 3 is a conceptual view for explaining the layer structure of the fuel cell unit 10 at the power generation section 11.

[0015] Figure 4 is a conceptual view for explaining the layer structure of the fuel cell unit 10 at the outer peripheral section 21.

[0016] Figure 5 is another example of the configuration of the protruding member 46.

[0017] Figure 6 is another example of the configuration of the protruding member 46.

[0018] Figure 7 is a conceptual view for explaining the configuration of the fuel cell stack 50. DETAILED DESCRIPTION

[0019] 1. Fuel cell unit

[0020] Figures 1-4 A view for explaining the fuel cell unit 10 according to one embodiment is shown in FIG. 1. The fuel cell unit 10 is a unit element for generating electricity by supplying hydrogen and oxygen (air), and a plurality of such fuel cell units 10 are stacked to configure a fuel cell.

[0021] Figure 1 is an exploded perspective view of the fuel cell unit 10, Figure 2 is a view obtained by viewing the fuel cell unit 10 from above. In addition, Figure 3 is a view for explaining the layer structure of the fuel cell unit 10 at the power generation section 11, Figure 4 is a view for explaining the layer structure of the fuel cell unit 10 at the outer peripheral section 21 (a section where the protruding member 46 is disposed).

[0022] In each of the drawings, each direction of a three-dimensional orthogonal coordinate system is indicated by an arrow. Here, in the in-plane direction of the fuel cell unit which is a flat plate as a whole, the x direction is a direction from the inlet side of the fluid toward the outlet side, and the y direction is a direction orthogonal to the x direction. The z direction is a stacking direction of each member of the fuel cell unit in the stacked configuration.

[0023] 1.1. Power generation section

[0024] The power generation section 11 is, for example, a portion enclosed by a broken line in FIG. 1, and is a portion that contributes to power generation, as indicated by a dotted line in FIG. 1. Figure 2 The power generation section 11 is, for example, a portion enclosed by a broken line in FIG. 1, and is a portion that contributes to power generation, as indicated by a dotted line in FIG. 1. Figure 3 The power generation section 11 is formed by laminating a plurality of layers, as indicated by a layer structure of the power generation section 11 (a portion of an A-A cross section) in FIG. 1.

[0025] In the power generation section 11 of the fuel cell unit 10, a cathode (oxygen supply side) and an anode (hydrogen supply side) are separated by an electrolyte membrane 12. The cathode has, in order from the electrolyte membrane 12 side, a cathode catalyst layer 13, a cathode diffusion layer 14, and a cathode separator 15. On the other hand, the anode has, in order from the electrolyte membrane 12 side, an anode catalyst layer 16, an anode diffusion layer 17, and an anode separator 18. Furthermore, the laminate formed by the electrolyte membrane 12, the cathode catalyst layer 13, the cathode diffusion layer 14, the anode catalyst layer 16, and the anode diffusion layer 17 is sometimes referred to as a membrane electrode assembly. Typically, the thickness of the membrane electrode assembly is about 0.4 mm, and typically, the thickness of the fuel cell unit 10 in the power generation section 11 is about 1.3 mm. A pair of separators is formed by the cathode separator 15 and the anode separator 18, and the membrane electrode assembly is disposed between the pair of separators.

[0026] Each layer can be configured as known, for example, as follows.

[0027] 1.1a. Electrolyte membrane

[0028] The electrolyte membrane 12 is a solid polymer film that exhibits good proton conductivity in a humidified state. For example, it is formed of a fluorine-based ion exchange membrane, and for example, a carbon-fluorine-based polymer can be used, and specifically, a perfluoroalkyl sulfonic acid-based polymer (Nafion (registered trademark)), and the like can be given.

[0029] The thickness of the electrolyte membrane 12 is not particularly limited, and is 100 μm or less, preferably 50 μm or less, and more preferably 10 μm or less.

[0030] 1.1b. Cathode catalyst layer

[0031] The cathode catalyst layer 13 is a layer that contains a catalyst metal in a state in which the catalyst metal is supported on a carrier. As the catalyst metal, for example, Pt, Pd, Rh, or an alloy containing the same can be given. As the carrier, a carbon carrier can be given, and in more detail, a carbon particle formed of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like can be given.

[0032] 1.1c. Anode catalyst layer

[0033] As with the cathode catalyst layer 13, the anode catalyst layer 16 is also a layer containing a catalyst metal in a state where the catalyst metal is supported on a carrier. As the catalyst metal, for example, Pt, Pd, Rh, or an alloy containing the same can be cited. As the carrier, a carbon carrier can be cited, and more specifically, a carbon particle composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, artificial graphite, and the like can be cited.

[0034] 1.1d. Cathode diffusion layer

[0035] The cathode diffusion layer 14 can be composed of a porous body having electrical conductivity, for example. As a more specific example, a carbon porous body (carbon paper, carbon cloth, glassy carbon, and the like), a metal porous body (metal mesh, foamed metal), and the like can be cited.

[0036] An MPL (microporous layer) can also be provided in the cathode diffusion layer as needed. The MPL is a coated thin film applied to the cathode catalyst layer 13 side in the cathode diffusion layer 14. The MPL has a function of adjusting moisture as needed, having hydrophobicity, hydrophilicity. As the MPL, a typical structure is one in which a hydrophobic resin such as polytetrafluoroethylene (PTFE) and an electrically conductive material such as carbon black are used as main components.

[0037] 1.1e. Anode diffusion layer

[0038] The anode diffusion layer 17 can be composed of a porous body having electrical conductivity, for example. As a more specific example, a carbon porous body (carbon paper, carbon cloth, glassy carbon, and the like), a metal porous body (metal mesh, foamed metal), and the like can be cited.

[0039] 1.1f. Cathode separator

[0040] The cathode separator 15 is a member that constitutes a pair of separators with the anode separator 18 and supplies a reaction gas (air in the present 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 a reaction gas flow path. The shape of the grooves is not particularly limited as long as the reaction gas can be supplied to the cathode diffusion layer 14 as appropriate, and a type in which a plate-like member is formed in a wavy shape as in the present embodiment can be cited. At this time, typically, the plate thickness is 0.1 to 0.2 mm, and typically, the height of the concave-convex is about 0.5 mm.

[0041] In the case of being wavy, a groove 15b is formed on the opposite side from the cathode separator 15 between the adjacent grooves 15a, which functions as a cooling water flow path.

[0042] In addition, according to Figure 1 It is known that, in the cathode separator 15, an air inlet hole A inCooling water inlet hole W in Hydrogen outlet hole H out An air outlet hole A is provided at the other end of the grooves 15a and 15b. out Cooling water outlet hole W out Hydrogen inlet hole H in Here, slot 15a is connected to air inlet hole A. in Air outlet hole A out Connecting slot 15b with cooling water inlet hole W in Cooling water outlet hole W out Connected.

[0043] The material constituting the cathode separator 15 can be any material suitable for use as a separator in a fuel cell unit, and can be an impermeable conductive material. Examples of such materials include dense carbon formed by compressing carbon to make it impermeable, and stamped metal sheets.

[0044] 1.1g. Anode separator

[0045] The anode separator 18, together with the cathode separator 15, forms a pair of separators and supplies the reactant gas (hydrogen) to the anode diffusion layer 17. It has multiple grooves 18a on the surface opposite the anode diffusion layer 17, which function as flow paths for the reactant gas. The shape of the grooves is not particularly limited, as long as they can adequately supply the reactant gas to the anode diffusion layer 17; for example, the plate-shaped component can be formed in a wavy shape, as in this embodiment. Typically, the plate thickness is 0.1 mm to 0.2 mm, and the height of the unevenness is approximately 0.4 mm.

[0046] In the case of a wavy shape, in this configuration, a groove 18b is formed on the opposite side between adjacent grooves 18a, with an anode baffle 18 spaced apart, which functions as a cooling water flow path.

[0047] In addition, according to Figure 1 It can be seen that an air inlet hole A is provided on the anode partition 18 at the position extending from the power generation section 11 to the outside, at one end of the groove 18a and groove 18b. in Cooling water inlet hole W in Hydrogen outlet hole H out An air outlet hole A is provided at the other end of the grooves 18a and 18b. out Cooling water outlet hole W out Hydrogen inlet hole H in Here, groove 18a is connected to hydrogen inlet hole H. in Hydrogen outlet hole H out Connecting slot 18b with cooling water inlet hole W in Cooling water outlet hole W out Connected.

[0048] The material constituting the anode separator 18 can be any material suitable for use as a separator in a fuel cell unit, and can be an impermeable conductive material. Examples of such materials include dense carbon formed by compressing carbon to make it impermeable, and stamped metal sheets.

[0049] 1.1h. Power generation of the power generation department

[0050] As is known, the fuel cell unit 10 described above generates electricity in the following manner.

[0051] If hydrogen is supplied from the groove 18a of the anode partition 18, the hydrogen passes through the anode diffusion layer 17 and decomposes into protons (H) in the anode catalyst layer 16. + ) and electrons (e － Protons pass through the electrolyte membrane 12, and electrons pass through the conductive wires connected to the outside, reaching the cathode catalyst layer 13 respectively. Here, oxygen (air) is supplied to the cathode catalyst layer 13 from the tank 15a of the cathode separator 15 via the cathode diffusion layer 14. In the cathode catalyst layer 13, water (H2O) is generated through protons, electrons, and oxygen. The generated water passes through the cathode diffusion layer 14 to the tank 15a of the cathode separator 15 and is discharged.

[0052] That is, in the fuel cell unit 10, the flow of electrons from the anode catalyst layer 16 through conductive wires connected to the outside is utilized as an electric current.

[0053] 1.2.Peripheral part

[0054] Peripheral part 21 is Figure 2 The outer side of the power generation section 11, surrounded by dotted lines, is the outer periphery of the fuel cell unit 10. This part, while not dedicated to power generation, is responsible for supplying various fluids to the power generation section, collecting fluids from the power generation section, and sealing the area. The outer periphery 21 is as follows... Figure 4 The outer peripheral portion 21 is composed of multiple layers stacked as shown in the layered structure (BB section). Specifically, in this embodiment, the outer peripheral portion 21 has the following structure.

[0055] 1.2a. Resin sheet

[0056] In the outer periphery 21, a resin sheet 23 is disposed between a pair of partitions, namely the cathode partition 15 and the anode partition 18, and the interior of the fuel cell unit 10 is sealed by the resin sheet 23. Figure 1 It can be seen that the resin sheet 23 is configured to surround the membrane electrode assembly.

[0057] The resin sheet 23 functions as a sealing component that closes and seals the cathode separator 15 and the anode separator 18 on the outer periphery 21 of the fuel cell unit 10.

[0058] The resin sheet 23 includes: a substrate 24; an adhesive layer 25 disposed on one side of the substrate 24 (the side facing the cathode separator); and an adhesive layer 26 disposed on the other side of the substrate 24 (the side facing the anode separator). The adhesive layer 25 is bonded to the cathode separator 15, and the adhesive layer 26 is bonded to the anode separator 18, thereby enclosing and sealing the power generation section 11.

[0059] The substrate 24 is formed of 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 substrate 24 is not particularly limited, but it is 0.05 mm or more and 0.25 mm or less.

[0060] Adhesive layer 25 and adhesive layer 26 are composed of adhesive and adhesive agent.

[0061] 1.2b. Washers

[0062] On the outer periphery 21, a gasket 40 is disposed on a partition (in this embodiment, cathode partition 15) of the fuel cell unit 10. The gasket 40 is disposed on the side of the partition opposite to the side where the membrane electrode assembly and resin sheet are disposed (i.e., the side opposite to the stacked adjacent fuel cell units 10), and functions as a sealing material between adjacent fuel cell units 10 when multiple fuel cell units 10 are stacked.

[0063] The cross-sectional shape of washer 40 is not particularly limited as long as it can be used as a washer; for example, a cross-sectional shape with a trapezoidal cross-section as in this embodiment can be used. In this case, the longer lower base becomes the partition side. Other cross-sectional shapes include quadrilaterals, triangles, semicircles, and semi-ellipses.

[0064] Therefore, washer 40 is as follows Figure 1 , Figure 2 ( Figure 2 (Shown in shaded area) This indicates a frame-shaped sheet component arranged along the outer periphery 21. The gasket 40 preferably has sealing properties and is flexible, and is therefore preferably made of an elastomer. The specific material of the elastomer is not particularly limited, and examples include ethylene propylene rubber, fluoropolymers, and silicone rubber.

[0065] 1.2c.Protruding parts

[0066] On the outer periphery 21, a protruding member 46 is provided on one or two partitions of the fuel cell unit 10 (in this embodiment, only the cathode partition 15, the same surface as the gasket 40). The protruding member 46 is provided on the side of the partition opposite to the side where the membrane electrode assembly and resin sheet are disposed (i.e., the side opposite to the stacked adjacent fuel cell unit 10). At the location where the protruding member 46 is provided, the gasket compression loss is reduced relative to the warping force of the fuel cell unit 10, and gas leakage is suppressed.

[0067] The protruding member 46 is positioned on the side (outer side) closer to the edge of the partition than the washer 40. The distance between the washer 40 and the protruding member 46 is not particularly limited. Figure 4 The spacing between the washer 40 and the protruding member 46, indicated by G, is larger than 0, preferably. Figure 4 W in Chinese G The width of the washer shown is below.

[0068] In addition, such as Figure 2 As shown, the protruding members 46 are preferably disposed at least at the four corners of the partition in a top view. Since the warpage of the fuel cell unit 10 during manufacturing is greater at these four corners, the effect of disposing of the protruding members 46 can be further improved. However, from the viewpoint that including the four corners is sufficient, it is also possible to... Figure 5 The protrusion 46 is thus arranged in a ring shape along the outer periphery of the fuel cell unit 10.

[0069] In addition, such as Figure 6 As shown, the protruding member 46 can also be disposed on the side of the partition plate opposite to the washer 40 (the side opposite to the resin sheet 23) with the edge side (outer side) of the partition plate closer to the gasket 40 than described above. In this embodiment, the protruding member 46 is disposed at the end where the gap between the pair of partition plates widens. Here, it is disposed between the resin sheet 23 and the cathode partition plate 15, and between the resin sheet 23 and the anode partition plate 18.

[0070] Figure 4 H in Chinese T The height ratio of the convex member 46 shown is... Figure 4 H in Chinese G The height of the washer 40 shown is small. The height difference is not particularly limited, but H is preferred. T For H G More than half.

[0071] in addition, Figure 4 W in Chinese T The width of the convex member 46 shown is not particularly limited, but is preferably the same as the width W of the washer 40. G They are of equal degree.

[0072] The cross-sectional shape of the convex component 46 ( Figure 4The top face 46a (with a rectangular shape) is preferably rectangular, with one of its long sides forming the top face 46a, which is preferably a wide plane. Thus, even a small amount of compression of the convex member 46 can produce a reaction force.

[0073] The material constituting the protruding part 46 is not particularly limited and can be the same material as the washer.

[0074] 1.3. Warping of fuel cell units

[0075] As previously shown, the fuel cell unit 10 is configured such that a membrane electrode assembly is disposed between a pair of separators (cathode separator 15 and anode separator 18) for the power generation section 11, a resin sheet 23 is disposed on the outer periphery 21, and a gasket 40 and a protruding member 46 are disposed thereon. Here, the fuel cell unit 10 is configured such that the materials constituting the fuel cell unit 10 are laminated and then joined by heating and stamping. Therefore, the cathode side has an upward (convex) warped shape.

[0076] 2. Fuel Cell

[0077] 2.1. Overall Structure

[0078] The fuel cell (sometimes also called a "fuel cell stack") 50 is a component consisting of multiple stacked fuel cell units 10 (about 50 to 400 pieces) and collects electricity from multiple fuel cell units 10. Figure 7 The outline of the structure is shown in the figure. The fuel cell stack 50 includes a stack housing 51, an end plate 52, multiple fuel cell units 10, a current collector 54, and a force-applying component 55.

[0079] The housing 51 is a shell that houses the multiple overlapping fuel cell units 10, current collectors 54, and force-applying components 55 inside it. In this embodiment, the housing 51 is a quadrilateral cylindrical shape with one end open and the other end closed, and plate-like sheets extend along the edge of the opening to the side opposite to the opening, forming a flange 51a.

[0080] The end plate 52 is a plate-shaped component that seals the opening of the housing 51. The end plate 52 is fixed to the housing 51 by bolts and nuts, etc., covering the portion of the housing 51 that overlaps with the flange 51a of the housing 51.

[0081] The fuel cell unit 10 is as described above. Multiple such fuel cell units 10 are overlapped. In this case, for the cathode separator 15 of one fuel cell unit 10, the anode separator 18 of the adjacent fuel cell unit 10 is arranged overlappingly on the cathode separator 15. Thus, 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.

[0082] The current collector 54 is a component that collects electricity from the stacked fuel cell unit 10. Therefore, the current collector 54 is disposed at each end of the stacked structure of the fuel cell unit 10 in the stacking direction, one end being the positive electrode and the other end being the negative electrode. Terminals (not shown) are connected to the current collector 54 and are configured to be electrically connected to an external source.

[0083] The force-applying component 55 is housed inside the housing 51 and applies pressure to the stack of the fuel cell unit 10 in its stacking direction. For example, a disc spring can be used as the force-applying component.

[0084] In such a fuel cell 50, as described above, due to warping of the fuel cell unit 10, when multiple such fuel cell units 10 are stacked, the spacing between the fuel cell units 10 gradually widens from the side under compression (end plate side) towards the opposite side (the unit spacing increases, and the gasket gap increases). In particular, in the widened portion, the gasket compression is insufficient, increasing concerns about gas leakage. To address this, by providing the convex member 46, the combined spring constant of the gasket and the convex member is greater than the spring constant of the gasket alone. As a result, relative to the warping reaction force of the same fuel cell unit, the gasket compression loss is reduced, the increase in gasket gap is smaller, and the occurrence of gas leakage can be suppressed.

Claims

1. A fuel cell unit having an electrode body between a pair of separators, wherein the fuel cell unit has: a gasket disposed at a surface of the separator on an opposite side from a surface of the separator on which the electrode body is disposed; and a convex member disposed at a surface of one of the pair of separators on an opposite side from a surface of the separator on which the electrode body is disposed, the convex member is disposed at a position closer to an outer peripheral edge of the separator than the gasket, and the height of the convex member is smaller than the height of the gasket.

2. The fuel cell unit according to claim 1, wherein the convex member is disposed at the same surface of the one separator as the surface on which the gasket is disposed.

3. The fuel cell unit according to claim 1, wherein the convex member is disposed at a surface of the one separator on an opposite side from the surface on which the gasket is disposed.

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

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