Separator for fuel cell and fuel cell

Abstract

The present invention provides a separator capable of suppressing accumulation of generated water in a flow path near a hydrogen outlet. A fuel cell separator has a recess recessed toward a flow path side in an edge region surrounding the flow path, in which a bypass flow path communicating with a part of the hydrogen flow path in the vicinity of a hydrogen outlet hole is formed in the edge region, and the recess is connected to the bypass flow path.

Description

Technical Field

[0001] This invention relates to a fuel cell and a separator for a fuel cell unit. Background Technology

[0002] Patent document 1 discloses a separator for a fuel cell with protrusions formed in the edge region.

[0003] Patent Document 1: Japanese Patent Application Publication No. 2019-186052 Summary of the Invention

[0004] Sometimes, generated water flows back from the hydrogen outlet manifold of the separator into the flow path, and this generated water accumulates in the flow path near the hydrogen outlet. This generated water may contain, for example, Fe dissolved from the separator, thus promoting the degradation of the electrolyte membrane.

[0005] In view of the above problems, the object of the present invention is to provide a baffle that can suppress the accumulation of generated water in the flow path near the hydrogen outlet.

[0006] This application discloses a separator for a fuel cell, which has a recessed portion in the edge region surrounding the flow path that is recessed towards the flow path side. A bypass flow path is formed in the edge region that communicates with a portion of the hydrogen flow path near the hydrogen outlet orifice, and the recess is connected to the bypass flow path.

[0007] This application discloses a fuel cell, which is composed of multiple fuel cell units having the above-mentioned fuel cell separators and electrolyte layers stacked together, wherein the fuel cell units are configured with a bypass flow path at the bottom.

[0008] Invention Effects

[0009] According to the present invention, the generated water flowing through the flow path can pass through the edge region with a recess and return from the edge region to the hydrogen outlet hole via the bypass flow path, thereby reducing the impact of generated water accumulation in the flow path on the electrolyte membrane. Attached Figure Description

[0010] Figure 1 This is an exploded perspective view of fuel cell unit 10.

[0011] Figure 2 This is a top-down view of the fuel cell unit 10.

[0012] Figure 3 This is a conceptual diagram illustrating the layer structure in the power generation section 11 of the fuel cell unit 10.

[0013] Figure 4 This is a diagram showing the vicinity of bypass flow path 27 in edge region 20. Detailed Implementation

[0014] Figures 1-3A diagram illustrating the basic structure of a fuel cell unit 10 according to one embodiment is shown. The fuel cell unit 10 is a unit that generates electricity by supplying hydrogen and oxygen (air), and multiple such fuel cell units 10 are stacked together to form a fuel cell.

[0015] Figure 1 This is an exploded perspective view of fuel cell unit 10. Figure 2 This is a diagram showing the fuel cell unit 10 viewed from above (in...). Figure 2 In the diagram, the hydrogen flow path formed on the anode partition 18 is indicated by dashed lines. Furthermore, Figure 3 This is a diagram illustrating the layer structure of the power generation section 11 in the fuel cell unit 10.

[0016] 1. Power Generation Department

[0017] The power generation section 11 is the part that helps generate electricity, such as... Figure 3 As shown, the layered structure in the power generation unit 11 is formed by stacking multiple layers. Figure 2 (Part of the AA section).

[0018] In the power generation section 11 of the fuel cell unit 10, an electrolyte membrane 12 separates a cathode (oxygen supply side) from an anode (hydrogen supply side). The cathode, from the electrolyte membrane 12 side, comprises a cathode catalyst layer 13, a cathode diffusion layer 14, and a cathode separator 15, stacked sequentially. Conversely, the anode, from the electrolyte membrane 12 side, comprises an anode catalyst layer 16, an anode diffusion layer 17, and an anode separator 18, stacked sequentially. The laminate consisting of the electrolyte membrane 12, cathode catalyst layer 13, cathode diffusion layer 14, anode catalyst layer 16, and anode diffusion layer 17 is sometimes referred to as a membrane electrode assembly (MEA). The MEA is typically about 0.4 mm thick, and the fuel cell unit 10 in the power generation section 11 is typically about 1.3 mm thick.

[0019] Each layer can be constructed as is commonly known, for example as follows.

[0020] 1.1. Electrolyte membrane

[0021] The electrolyte membrane 12 is a solid polymer film that exhibits good proton conductivity in a wetted state. For example, it can be made of fluorine-based ion exchange membranes, or carbon-fluorine based polymers, specifically, perfluoroalkyl sulfonic acid polymers (Nafion (registered trademark)).

[0022] The thickness of the electrolyte membrane 12 is not particularly limited, but it is preferably 100 μm or less, more preferably 50 μm or less, and even more preferably 10 μm or less.

[0023] 1.2. Cathode catalyst layer

[0024] The cathode catalyst layer 13 is a layer containing a catalyst metal in the form of a catalyst metal supported on a carrier. Examples of catalyst metals include Pt, Pd, Rh, or alloys containing these. Examples of carriers include carbon carriers, and more specifically, carbon particles composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0025] 1.3. Anode catalyst layer

[0026] The anode catalyst layer 16, like the cathode catalyst layer 13, is a layer containing a catalyst metal in the form of a catalyst metal supported on a carrier. Examples of catalyst metals include Pt, Pd, Rh, or alloys containing these. Examples of carriers include carbon carriers, and more specifically, carbon particles composed of glassy carbon, carbon black, activated carbon, coke, natural graphite, and artificial graphite.

[0027] 1.4. Cathode Diffusion Layer

[0028] The cathode diffusion layer 14 can be made of a porous material with electrical conductivity, for example. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal).

[0029] As needed, an MPL (microporous layer) can be provided in the cathode diffusion layer. The MPL is a coating film applied to the side of the cathode catalyst layer 13 in the cathode diffusion layer 14. The MPL can have the function of adjusting the moisture content by being hydrophobic or hydrophilic as needed. As an MPL, it is usually composed of hydrophobic resins such as polytetrafluoroethylene (PTFE) and conductive materials such as carbon black as the main components.

[0030] 1.5. Anode Diffusion Layer

[0031] The anode diffusion layer 17 can be made of a porous material with electrical conductivity, for example. More specific examples include carbon porous materials (carbon paper, carbon cloth, glassy carbon, etc.) and metal porous materials (metal mesh, foamed metal).

[0032] 1.6. Cathode separator

[0033] The cathode separator 15 is a component that supplies reactant gas (air in this embodiment) to the cathode diffusion layer 14. It has multiple grooves 15a on its surface opposite the cathode diffusion layer 14, which function as flow paths for the reactant gas. The shape of the grooves is not particularly limited as long as they allow for adequate supply of reactant gas to the cathode diffusion layer 14; for example, the plate-like component can be formed in a wavy 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 unevenness is typically around 0.5 mm.

[0034] In the case of a wavy shape, a cathode partition 15 is spaced between adjacent grooves 15a, and a groove 15b is formed on the opposite side, which serves as a cooling water flow path.

[0035] The material constituting the cathode separator 15 can be any material suitable for use as a separator in a fuel cell unit, or it can be a gas-impermeable conductive material. Examples of such materials include stamped stainless steel or other metal sheets.

[0036] 1.7. Anode separator

[0037] The anode partition 18 is a component that supplies the reactant gas (hydrogen) to the anode diffusion layer 17. It has multiple grooves 18a on its 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 allow for adequate supply of the reactant gas to the anode diffusion layer 17; for example, the plate-like component can be formed in a wavy 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 unevenness is typically around 0.4 mm.

[0038] In the case of a wavy shape, in this configuration, a groove 18b is formed on the opposite side between adjacent grooves 18a, separated by an anode baffle 18, which serves as a cooling water flow path.

[0039] The material constituting the anode separator 18 can be any material suitable for use as a separator in a fuel cell unit, or it can be a gas-impermeable conductive material. Examples of such materials include stamped stainless steel or other metal sheets.

[0040] 1.8. Power generation based on the power generation department

[0041] As is known, the power generation section 11 of the fuel cell unit 10 described above generates electricity as follows.

[0042] If hydrogen is supplied from the tank 18a of the anode partition 18, the hydrogen decomposes into protons (H+) in the anode catalyst layer 16 through the anode diffusion layer 17. + ) 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, in the cathode catalyst layer 13, oxygen (air) is supplied 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 from 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 then discharged.

[0043] That is, in the fuel cell unit 10, the flow of electrons through conductive wires connected from the anode catalyst layer 16 to the outside is used as the current.

[0044] 2. Edge area

[0045] The edge region 20 is located outside the power generation section 11 and is the area that constitutes the outer periphery of the fuel cell unit 10. Although it does not participate in power generation, it is a part for supplying various fluids to the power generation section 11, collecting and discharging fluids from the power generation section, or for sealing.

[0046] 2.1. Seals

[0047] In the edge region 20, a resin sheet 23 is disposed between the cathode separator 15 and the anode separator 18 (reference). Figure 1 The interior of the fuel cell unit 10 is sealed by the resin sheet 23, and the anode side and cathode side are separated in the edge region 20.

[0048] from Figure 1 It is understood that the resin sheet 23 is configured to surround the membrane electrode assembly. That is, the resin sheet 23 is sandwiched between the cathode separator 15 and the anode separator 18 in the edge region 20 of the fuel cell unit 10 and its inner side is sealed.

[0049] The resin sheet 23 includes a substrate, an adhesive layer disposed on one side of the substrate (the side facing the cathode separator), and an adhesive layer disposed on the other side of the substrate (the side facing the anode separator). It is bonded to the cathode separator 15 and the anode separator 18 respectively by the adhesive layers, thereby sealing the power generation section 11 and separating the cathode side and the anode side in the edge region 20.

[0050] 2.2. Inlet / Outlet

[0051] like Figure 1 , Figure 2 As shown, in the edge region 20, an end side (in) is provided across the power generation unit 11. Figure 2 An air inlet hole A is provided on the left side. in Cooling water inlet hole W in Hydrogen outlet hole H out An air outlet hole A is provided on the other end side. out Cooling water outlet hole W out Hydrogen inlet hole H in .

[0052] Additionally, the groove 15a of the cathode separator 15 is connected to the air inlet hole A via the resin sheet 23. in Air outlet hole A out Connecting slot 15b with cooling water inlet hole W in Cooling water outlet hole W out Connected. On the other hand, the groove 18a of the anode separator 18 is connected to the hydrogen inlet hole H through the resin sheet 23. in Hydrogen outlet hole H outConnecting slot 18b with cooling water inlet hole W in Cooling water outlet hole W out Connected.

[0053] 2.3.Inflow channel part

[0054] An air inlet hole A is formed on the cathode partition 15. in The air flow path of the tank 15a of the power generation unit 11 has an inflow path section, and a hydrogen inlet hole H is formed on the anode partition 18. in The hydrogen inflow path 21 is the inflow path of the tank 18a of the power generation section 11. Figure 2 This indicates the inflow path 21 of the anode partition 18.

[0055] like Figure 2 As shown, a flow path is provided in the inflow flow path section (in Figure 2 (The middle is the hydrogen flow path), to flow from the inlet hole (in) Figure 2 The middle part is the hydrogen inlet hole H. in The fluid is supplied to the power generation unit 11 by extending towards the power generation unit 11. Figure 2 (The gas in the middle is hydrogen).

[0056] 2.4. Outflow channel part

[0057] An air outlet hole A is formed on the cathode separator 15. out The outflow path of the air flow path of the tank 15a of the power generation unit 11 is provided on the anode partition 18, and a hydrogen outlet hole H is formed therethrough. out The outflow path section 22 of the hydrogen flow path of the tank 18a of the power generation section 11. Figure 2 This refers to the outflow path 22 of the anode partition 18.

[0058] like Figure 2 As shown, a flow path (in) is provided in the outflow path section. Figure 2 (The middle is the hydrogen flow path), so that it flows from the power generation unit 11 toward the outlet hole (in Figure 2 The middle is the hydrogen outlet hole H. out The system is configured to collect fluids, discharging fluids from the power generation unit 11 (in...). Figure 2 (The middle part contains hydrogen gas and water produced).

[0059] 2.5. Structure of partitions in the edge area

[0060] In this configuration, the partition in the edge region 20 has the following structure. Figure 4 The middle shows the Figure 2 The part represented by B (hydrogen outlet hole H in edge region 20) outA diagram illustrating the structure of the anode separator 18 is shown nearby. The anode separator 18 will be described here, but the cathode separator 15 can be considered in the same way.

[0061] In this invention, a plurality of recesses 25 are disposed on the surface of the hydrogen flow path side in the edge region 20 of the anode separator 18. These recesses 25 prevent so-called lateral flow.

[0062] Furthermore, in this invention, in the edge region 20 of the anode separator 18, at the hydrogen outlet hole H... out A bypass flow path 27, which is partly connected to the hydrogen flow path, is formed nearby. Figure 4 (Indicated by a thick straight arrow), the recess 25 connects to the bypass flow path 27. More specifically, in this embodiment, as... Figure 4 As shown, a branch flow path 27a is provided, connecting the hydrogen flow path closest to the recess 25 to two recesses 25 that are spaced apart. A bypass main flow path 27b is provided, spanning the two spaced recesses 25 where the branch flow path 27a is provided, thereby forming a bypass flow path 27. The bypass main flow path 27b can connect to the recess 25 by crossing the recess 25 along its length.

[0063] Through this bypass flow path 27, the generated water flowing into the hydrogen flow path (e.g., after power generation stops, it can pass through the hydrogen outlet hole H) out The generated water (which flows backwards to the hydrogen flow path) returns from the edge region 20 to the hydrogen outlet orifice H via the bypass flow path 27. out This reduces the impact of water accumulation in the hydrogen flow path on the electrolyte membrane.

[0064] Furthermore, as described above, the fuel cell is manufactured by stacking multiple fuel cell units 10. However, when the fuel cell is installed, it is preferable that the fuel cell is configured such that the bypass flow path 27 is below the hydrogen flow path. This makes the guidance of generated water to the bypass flow path 27 smoother.

[0065] Symbol Explanation

[0066] 10-Fuel cell unit, 11-Power generation section, 15-Cathode separator, 18-Anode separator, 20-Edge region, 21-Inflow path section, 22-Outflow path section, 23-Resin sheet, 25-Recess, 27-Bypass path.

Claims

1. A separator for a fuel cell, having a recessed portion in the edge region surrounding a flow path that is recessed towards the flow path side. The fuel cell separator is characterized in that a bypass flow path is formed in the edge region, which is connected to a portion of the hydrogen flow path near the hydrogen outlet orifice, and the recess is connected to the bypass flow path.

2. A fuel cell comprising a plurality of fuel cell units having a separator and an electrolyte layer as described in claim 1, stacked together. The fuel cell is characterized in that the fuel cell unit is configured such that the bypass flow path is at the bottom.

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