Fuel cell unit

Abstract

A fuel cell unit that generates electricity by reaction of a reaction gas has: a membrane electrode assembly having an electrolyte membrane and a catalyst layer; a gas diffusion layer that is laminated to the membrane electrode assembly and is composed of a metal porous body; and a separator that is laminated to the gas diffusion layer, is parallel to a surface direction of the membrane electrode assembly, and has a groove on a surface on the separator side for the passage of the reaction gas.

Description

[0001] This application claims priority based on Japanese Patent Application No. 2024-207840, filed on November 29, 2024, the entire disclosure of which is incorporated herein by reference. Technical Field

[0002] This disclosure relates to fuel cell cells. Background Technology

[0003] Various techniques regarding the layer structure of fuel cell cells have been proposed. For example, Japanese Patent Application Publication No. 2002-289223 discloses a technique of providing multiple grooves on the catalyst layer side of the separator. The multiple grooves are used as flow paths for the reactant gases. In order to supply reactant gases to the catalyst layer more efficiently, the inventors of this application have studied the use of a gas diffusion layer composed of porous materials between the catalyst layer and the separator. Summary of the Invention

[0004] In fuel cell cells using separators with flow paths and gas diffusion layers, when the gas diffusion layer is thinned to reduce the size of the fuel cell cell, the cross-sectional area of ​​the reactant gas flowing in the gas diffusion layer in the flow direction becomes smaller, and the pressure loss of the reactant gas increases. As a result, the reactant gas is difficult to spread throughout the entire surface of the catalyst layer, which may reduce the power generation efficiency.

[0005] means for solving problems

[0006] This disclosure can be implemented in the following ways.

[0007] According to one aspect of this disclosure, a fuel cell unit that generates electricity through the reaction of reactant gases is provided. The fuel cell unit comprises: a membrane electrode assembly having an electrolyte membrane and a catalyst layer; a gas diffusion layer, stacked on the membrane electrode assembly and composed of a porous metal body; and a separator, stacked on the gas diffusion layer, parallel to the surface direction of the membrane electrode assembly and being plate-shaped, wherein the gas diffusion layer has grooves on the surface of the separator side for the flow of the reactant gases. Attached Figure Description

[0008] Figure 1 This is a plan view of a fuel cell cell in one embodiment of this disclosure.

[0009] Figure 2 It means along Figure 1 A diagram of the cross-section cut by line II-II.

[0010] Figure 3 This is a cross-sectional view of a comparative example fuel cell cell.

[0011] Figure 4This is a diagram illustrating the fuel cell unit of the second embodiment.

[0012] Figure 5 This is a diagram illustrating the fuel cell unit of the third embodiment. Detailed Implementation

[0013] A. First implementation method:

[0014] A1. Structure of fuel cell unit 100:

[0015] Figure 1 This is a plan view of a fuel cell cell 100 in one embodiment of the present disclosure. Figure 1 This shows the fuel cell unit 100 as viewed from the cathode-side partition 141 side, described later. The fuel cell unit 100 has a rectangular shape when viewed in the thickness direction. The fuel cell unit 100 generates electricity through the reaction of reactant gases. In this embodiment, the reactant gases are hydrogen as fuel gas and air as oxidant gas. The fuel cell unit 100 is a multi-layered stack, for example, used as a power source for driving electric vehicles.

[0016] An oxidant gas manifold 11a, 11b, a refrigerant manifold 12a, 12b, and a fuel gas manifold 13a, 13b are formed in a fuel cell cell 100. Oxidant gas manifold 11a supplies oxidant gas to the fuel cell cell 100. Oxidant gas manifold 11b discharges oxidant gas from the fuel cell cell 100. Refrigerant manifold 12a supplies coolant to the fuel cell cell 100. Refrigerant manifold 12b discharges refrigerant from the fuel cell cell 100. Fuel gas manifold 13a supplies fuel gas to the fuel cell cell 100. Fuel gas manifold 13b discharges fuel gas from the fuel cell cell 100. Reactant gases travel from the supply manifolds 11a, 13a to the discharge manifolds 11b, 13b via a tank GR.

[0017] Figure 2 It means along Figure 1 A cross-sectional view of the section cut along line II-II. The fuel cell cell 100 includes a membrane electrode assembly 110, hydrophobic layers 121 and 122, gas diffusion layers 131 and 132, a cathode-side separator 141, and an anode-side separator 142. Furthermore, in the following text, one side of the cathode-side separator 141 is sometimes referred to as the "cathode side," and one side of the anode-side separator 142 is sometimes referred to as the "anode side."

[0018] <Structure of membrane electrode assembly 110>

[0019] The membrane electrode assembly 110 has a flat, plate-like shape when viewed in the thickness direction TD. The membrane electrode assembly 110 includes an electrolyte membrane 111, a cathode-side catalyst layer 112, and an anode-side catalyst layer 113. The electrolyte membrane 111 transports protons generated on the anode side to the cathode side. The electrolyte membrane 111 is a solid polymer membrane, such as a proton-conducting ion-exchange membrane composed of a fluorinated resin like a perfluorosulfonic acid polymer. The cathode-side catalyst layer 112 is stacked on one side of the electrolyte membrane 111. The cathode-side catalyst layer 112 catalyzes the reduction reaction of the oxidant gas. The anode-side catalyst layer 113 catalyzes the oxidation reaction of the fuel gas. The cathode-side catalyst layer 112 and the anode-side catalyst layer 113 are composed of carbon particles, for example, loaded with a catalyst metal such as platinum. The anode-side catalyst layer 113 is stacked on the other side of the electrolyte membrane 111.

[0020] Furthermore, the term "layering" in this disclosure refers not only to the state in which components are in direct contact with each other and overlap, but also to the state in which other components are sandwiched between components. Additionally, in this disclosure, the cathode-side catalyst layer 112 and the anode-side catalyst layer 113 are also collectively referred to as "catalyst layers".

[0021] <Structure of hydrophobic layers 121 and 122>

[0022] Hydrophobic layers 121 and 122 have a plate-like appearance when viewed in the thickness direction TD. Hydrophobic layers 121 and 122 are stacked on the opposite sides of the catalyst layers 112 and 113 that are in contact with the electrolyte membrane 111. Hydrophobic layers 121 and 122 discharge water generated by the reduction reaction of the oxidant gas to the gas diffusion layers 131 and 132. Furthermore, hydrophobic layers 121 and 122 transfer electrons from the membrane electrode assembly 110 to the gas diffusion layers 131 and 132. Hydrophobic layers 121 and 122 contain conductive carbon particles and a hydrophobic agent. The hydrophobic agent is, for example, a fluorinated resin such as polytetrafluoroethylene.

[0023] <Structure of gas diffusion layers 131 and 132>

[0024] Gas diffusion layers 131 and 132 are respectively stacked on the opposite sides of the hydrophobic layers 121 and 122 that are in contact with the membrane electrode assembly 110. The thickness of the gas diffusion layers 131 and 132 is, for example, 0.2 mm to 0.5 mm. The gas diffusion layers 131 and 132 uniformly supply the reactant gas to the membrane electrode assembly 110, promoting power generation. In addition, the gas diffusion layers 131 and 132 transfer electrons from the hydrophobic layers 121 and 122 to the cathode-side separator 141 and the anode-side separator 142, respectively.

[0025] The gas diffusion layers 131 and 132 in this disclosure are composed of a porous metal body. The porous metal body is manufactured, for example, by foaming metals such as aluminum, nickel, titanium, or stainless steel. The porous metal body has multiple small pores. The small pores are interconnected. Reactive gases can flow through the small pores. Multiple grooves GR are formed in the surface of the gas diffusion layer 131 that contacts the cathode-side partition 141 and in the surface of the gas diffusion layer 132 that contacts the anode-side partition 142. The grooves GR are formed, for example, by machining, laser processing, etc. Reactive gases flow through the grooves GR. More specifically, oxidant gas flows in the space defined by the grooves GR and the cathode-side partition 141. Additionally, fuel gas flows in the space defined by the grooves GR and the anode-side partition 142. Figure 1 As shown, the various cells GR are arranged parallel to each other along the length of the fuel cell unit 100. Therefore, Figure 2 It can also be described as a cross-section cut in a direction perpendicular to the flow direction of the reacting gas.

[0026] like Figure 2 As shown, in this embodiment, each groove GR is formed into a rectangle in the cross-section of the gas diffusion layers 131 and 132 cut along a direction perpendicular to the direction of the reactant gas flow. In other words, the gas diffusion layer 131 has a structure with alternating continuous protrusions 135 and recesses 136. The protrusions 135 protrude toward the cathode-side partition 141 or the anode-side partition 142 and are in contact with the cathode-side partition 141 or the anode-side partition 142. The surface of the protrusions 135 that are in contact with the cathode-side partition 141 or the anode-side partition 142 is parallel to the cathode-side partition 141 and the anode-side partition 142. It can also be said that the protrusions 135 constitute the side surface of each groove GR. The recesses 136 are recessed toward the membrane electrode assembly 110. It can also be said that the recesses 136 constitute the bottom surface of each groove GR. The width of the protrusions 135 is, for example, 0.2 mm to 0.8 mm. The width of the recesses 136 is, for example, 0.2 mm to 0.8 mm. The height of the protrusion 135 is, for example, 0.2mm to 0.8mm.

[0027] <Structure of cathode-side partition 141 and anode-side partition 142>

[0028] In the following text, without distinguishing between the cathode-side partition 141 and the anode-side partition 142, both the cathode-side partition 141 and the anode-side partition 142 are collectively referred to as "partitions". Partitions 141 and 142 have a flat, plate-like shape. Partitions 141 and 142 are parallel to the surface direction of the membrane electrode assembly 110. Partitions 141 and 142 are respectively stacked on the opposite side of the gas diffusion layers 131 and 132 that are in contact with the hydrophobic layers 121 and 122. The thickness of partitions 141 and 142 is, for example, 0.05 mm to 0.2 mm. Electrons are transferred from the gas diffusion layers 131 and 132 to the partitions 141 and 142. The surfaces of partitions 141 and 142 on the gas diffusion layer 131 and 132 side are in contact with the protrusion 135. That is, the load applied to partitions 141 and 142 is also applied to the protrusion 135.

[0029] A2. Comparison with the comparative example fuel cell cell 500:

[0030] Figure 3 This is a cross-sectional view of a comparative example fuel cell cell 500. Figure 3 and Figure 2 Similarly, this shows the cross-section of the fuel cell cell 500 cut in a direction perpendicular to the direction of the reactant gas flow. Additionally, in Figure 3 Only the structure on the cathode side is shown; the structure on the anode side is omitted. The structure on the anode side in the comparative example is the same as the structure on the cathode side. The structures of the gas diffusion layer 531 and the separator 541 in the comparative example fuel cell unit 500 differ from those in the above-described embodiment. Other structures are the same as those in the fuel cell unit 100 of the embodiment; therefore, the same reference numerals are used, and descriptions are omitted.

[0031] When viewed in the thickness direction TD, the gas diffusion layer 531 has a flat appearance. The surface of the gas diffusion layer 531 is flat. That is, unlike the gas diffusion layers 131 and 132 in the embodiments, the gas diffusion layer 531 does not have grooves.

[0032] The partition 541 is manufactured by repeatedly bending a flat plate. The partition 541 has multiple grooves 500GR. The reactant gas flows in the grooves 500GR. More specifically, the reactant gas flows in the space defined by the grooves 500GR and the gas diffusion layer 531.

[0033] In the comparative example, the tank 500GR is located on the partition 541, making it difficult to construct a thin fuel cell cell while ensuring the depth of the tank 500GR and the thickness of the gas diffusion layer 531. Furthermore, the distance from the reactant gas to the membrane electrode assembly 110 is relatively long. Therefore, the reactant gas cannot be adequately supplied to the membrane electrode assembly 110, potentially reducing the power generation efficiency in the fuel cell cell 500.

[0034] In contrast, Figure 2 In the fuel cell cell 100 of the illustrated embodiment, the channel GR for the flow of reactant gas is provided in the gas diffusion layers 131 and 132. Therefore, compared with the comparative example where the channel GR is provided in the separator 541, the fuel cell cell 100 can be constructed thinner while ensuring the depth of the channel GR and the thickness of the gas diffusion layers 131 and 132. In addition, the path of the reactant gas to the membrane electrode assembly 110 can be shortened. As a result, the power generation efficiency of the fuel cell cell 100 can be improved.

[0035] The fuel cell unit 100 according to the first embodiment described above includes: separators 141 and 142 parallel to the surface direction of the membrane electrode assembly 110; and a gas diffusion layer 131 having grooves GR on the surface of the separators 141 and 142 for the flow of reactant gas. Therefore, compared to a structure where grooves 500GR are provided on the separator 541, the overall thickness of the fuel cell unit 100 can be reduced while ensuring the thickness of the gas diffusion layers 131 and 132. Specifically, when grooves 500GR are provided on the separator 541, the grooves 500GR are provided by bending the separator 541, which is thinner than the gas diffusion layers 131 and 132. Therefore, it is difficult to form a thin cell while ensuring the grooves 500GR. In contrast, when grooves GR are provided on the gas diffusion layer 131, the grooves GR are provided by machining the gas diffusion layer 131. Therefore, compared to a structure where the separator 541 is bent to form the channel 500GR, the overall thickness of the fuel cell cell 100 can be reduced. This allows for a thinner fuel cell cell 100 while suppressing pressure loss in the gas diffusion layers 131 and 132. Furthermore, the distance between the channel GR and the catalyst layers 112 and 113 can be shortened, improving the supply efficiency of the reactant gases.

[0036] Furthermore, according to the fuel cell cell 100 of the first embodiment, grooves GR are provided in the gas diffusion layers 131 and 132. Therefore, compared with the structure in which grooves 500GR are provided on the separator 541, it is possible to make the spacing between the grooves GR relatively narrow while ensuring the contact area between the separators 141 and 142 and the gas diffusion layers 131 and 132. Specifically, when grooves 500GR are provided on the separator 541, the grooves 500GR are formed by stamping or the like. In this case, when it is desired to narrow the spacing between adjacent grooves 500GR, the separators 541 between adjacent grooves 500GR become sharp, and the contact area between the separators 541 and the gas diffusion layer 531 becomes smaller. As a result, local pressure is applied to the gas diffusion layer 531, which may reduce power generation performance and durability.

[0037] In contrast, as with the fuel cell cell 100 of the first embodiment, when grooves GR are provided on the gas diffusion layers 131, 132, the grooves GR are formed by machining or laser processing of a porous metal body. That is, the spacing of the grooves GR can be made narrower while keeping the protrusions 135 flat. As a result, the spacing of the grooves GR can be made narrower while maintaining the contact area between the separators 141, 142 and the gas diffusion layers 131, 132.

[0038] Furthermore, in the fuel cell cell 100 according to the first embodiment, the gas diffusion layers 131 and 132 are composed of a porous metal body. Therefore, compared to a structure using a porous body made of a material other than a metal, such as carbon, as the gas diffusion layer, the rigidity of the gas diffusion layers 131 and 132 can be improved. Thus, even when a relatively strong pressure TD in the thickness direction is applied to the gas diffusion layers 131 and 132, damage to the gas diffusion layers 131 and 132 can be suppressed. In addition, since the electrical resistance of metallic materials is generally lower than that of carbon, the conductivity can be improved compared to a structure where the gas diffusion layers 131 and 132 are formed of carbon.

[0039] Furthermore, in the fuel cell cell 100 according to the first embodiment, the groove GR is formed as a rectangle in the cross-section of the gas diffusion layers 131 and 132, which are cut in a direction perpendicular to the direction of reaction gas flow. Therefore, compared with structures such as grooves being sinusoidal, the contact area with the separators 141 and 142 can be increased while ensuring the cross-sectional area of ​​the groove GR. As a result, even if pressure is applied in the thickness direction TD of the fuel cell cell 100, local pressure on the gas diffusion layers 131 and 132 can be suppressed, and damage to the fuel cell cell 100 and reduction in power generation performance can be suppressed.

[0040] B. Second implementation method:

[0041] Figure 4 This is a diagram illustrating the fuel cell cell 100b of the second embodiment. Figure 4 and Figure 2 Similarly, this shows the cross-section of the fuel cell cell 100b cut in a direction perpendicular to the direction of the reactant gas flow. Additionally, in Figure 4 The anode side is omitted, and only the cathode side is shown. The structure of the gas diffusion layer 131b of the fuel cell cell 100b in the second embodiment differs from that of the fuel cell cell 100 in the first embodiment. Other structures are the same as those in the fuel cell cell 100 of the first embodiment, so their description is omitted.

[0042] exist Figure 4The right side schematically shows the pore size distribution of the gas diffusion layer 131b. In this embodiment, the gas diffusion layer 131b has a pore size distribution such that, in the thickness direction TD, the pore size on the side farther away from the membrane electrode assembly 110 is smaller. In other words, the gas diffusion layer 131b has two portions located at different positions along the thickness direction TD of the gas diffusion layer 131b. Each of the two portions has a pore. One portion has a pore with a smaller diameter than the other portion, wherein the one portion is farther from the membrane electrode assembly 110 than the other portion. Such a gas diffusion layer 131b is formed, for example, by sequentially stacking a first layer composed of metal powder with pores having relatively large diameters, a second layer composed of metal powder with pores having smaller diameters than the first layer, and a third layer composed of metal powder with pores having smaller diameters than the second layer. The gas diffusion layer 131b is not limited to the above method and can be manufactured by any method. The pore size distribution can be determined, for example, by mercury intrusion porosimetry.

[0043] Furthermore, not only the gas diffusion layer 131b on the cathode side, but also the gas diffusion layer 132 on the anode side may have the structure described above. Alternatively, only the gas diffusion layer 132 on the anode side may have the structure described above.

[0044] According to the fuel cell cell 100b of the second embodiment described above, the gas diffusion layer 131b has two portions located at different positions along the thickness direction TD of the gas diffusion layer 131b. Each portion has a pore. One portion has a pore with a smaller diameter than the other portion, and the other portion is farther from the membrane electrode assembly 110. Therefore, water present in the gas diffusion layer 131b can be easily drained from the side closer to the membrane electrode assembly 110 to the side farther away from the membrane electrode assembly 110. The gas diffusion layer 131b is typically composed of a hydrophilic porous metal. More specifically, in the portions of the gas diffusion layer 131b with smaller pore diameters, the adsorption force on water is stronger due to the closer distance between the metal particles. Thus, water can be attracted to the side of the gas diffusion layer 131b farther from the membrane electrode assembly 110, improving the drainage performance of the gas diffusion layer 131b.

[0045] C. Third implementation method:

[0046] Figure 5 This is a diagram illustrating the fuel cell cell 100c of the third embodiment. Figure 5 and Figure 2 Similarly, this shows the cross-section of the fuel cell cell 100c cut in a direction perpendicular to the direction of the reactant gas flow. Additionally, in Figure 5The anode side is omitted, and only the cathode side is shown. The structure of the gas diffusion layer 131c of the fuel cell cell 100c in the third embodiment differs from that of the fuel cell cell 100 in the first embodiment. Other structures are the same as those of the fuel cell cell 100 in the first embodiment, so their description is omitted.

[0047] like Figure 5 As shown, the gas diffusion layer 131c has a through-flow path FP that extends in the thickness direction TD and allows the reactant gas to flow through. In this embodiment, the through-flow path FP is provided in both the protrusion 135 and the recess 136. The through-flow path FP is a through hole provided in the thickness direction TD of the gas diffusion layer 131c. The reactant gas is supplied to the membrane electrode assembly 110 side via the through-flow path FP.

[0048] Furthermore, not only the gas diffusion layer 131c on the cathode side, but also the gas diffusion layer 132 on the anode side can have the structure described above. Alternatively, only the gas diffusion layer 132 on the anode side may have the structure described above. Moreover, the fuel cell unit 100c according to the third embodiment can be used in combination with the fuel cell unit 100b of the second embodiment.

[0049] According to the fuel cell cell 100c of the third embodiment described above, the gas diffusion layer 131c has a through flow path FP that extends in the thickness direction TD and allows the reactant gas to flow through it. Therefore, the reactant gas can be supplied to the membrane electrode assembly 110 side via the through flow path FP. As a result, even in the presence of water in the gas diffusion layer 131c, the path of the reactant gas can be ensured, and the reduction in the supply efficiency of the reactant gas can be suppressed.

[0050] D. Other implementation methods:

[0051] (D1) In the above embodiment, the plurality of grooves GR are formed in a rectangular shape in the cross-section of the gas diffusion layers 131, 132 cut in a direction perpendicular to the direction of the reaction gas flow, but this disclosure is not limited thereto. The plurality of grooves GR can be of any shape. Even so, since the grooves GR are provided on the gas diffusion layers 131, 132, the overall thickness of the fuel cell cell 100 can be reduced while ensuring the thickness of the gas diffusion layers 131, 132, compared with the structure in which grooves are provided on the partitions 141, 142.

[0052] (D2) In the above embodiments, the hydrophobic layers 121 and 122 in the fuel cell cells 100, 100b and 100c may also be omitted.

[0053] (D3) In the above embodiments, as Figure 1As shown, multiple grooves GR are arranged parallel to each other along the length direction of the fuel cell cell 100, but this disclosure is not limited thereto. When viewed in the thickness direction TD of the fuel cell cell 100, the multiple grooves GR can be arranged in any shape. For example, the multiple grooves GR can be arranged in a meandering manner. Alternatively, a structure with only one groove GR may be used instead of multiple grooves GR. In such a structure, the single groove GR can also form a so-called serpentine flow path that meanders back and forth in the region between the manifolds 11a, 13a on the supply side of the reactant gas and the manifolds 11b, 13b on the discharge side of the reactant gas.

[0054] (D4) In the above embodiments, the portions of the separators 141 and 142 that contact the protrusion 135 may be thicker than the other portions. With such a structure, when a load in the thickness direction TD is applied to the fuel cell cells 100, 100b, and 100c, the rigidity of the portions of the separators 141 and 142 to which the local load is applied can be improved.

[0055] (D5) In the above embodiments, fuel cell cells 100, 100b, and 100c can also be used as water electrolysis cells.

[0056] (D6) In the first embodiment described above, grooves GR are provided in both the gas diffusion layer 131 on the cathode side and the gas diffusion layer 132 on the anode side, but this disclosure is not limited to this. Grooves GR may also be provided in only one of the gas diffusion layers 131 and 132.

[0057] (D7) In the second embodiment described above, the porosity of the gas diffusion layer 131b on the side furthest from the membrane electrode assembly 110 in the thickness direction TD may be less than that on the side closer to the membrane electrode assembly 110. The porosity can be measured, for example, by Archimedes' method, mercury porosimetry, or similar methods.

[0058] (D8) In the third embodiment described above, the through flow path FP is provided in both the protrusion 135 and the recess 136, but this disclosure is not limited to this. The through flow path FP may also be provided in only one of the protrusion 135 and the recess 136.

[0059] This disclosure is not limited to the embodiments described above, and can be implemented in various structures without departing from its spirit. For example, in order to solve some or all of the above-described problems, or to achieve some or all of the above-described effects, the technical features in the embodiments can be appropriately replaced or combined. In addition, if a technical feature is not described as an essential technical feature in this specification, it can be appropriately deleted. For example, this disclosure can also be implemented by the following description.

[0060] (1) According to one aspect of the present disclosure, a fuel cell unit for generating electricity through the reaction of reactant gases is provided. The fuel cell unit comprises: a membrane electrode assembly having an electrolyte membrane and a catalyst layer; a gas diffusion layer stacked on the membrane electrode assembly and composed of a porous metal body; and a separator stacked on the gas diffusion layer, parallel to the surface direction of the membrane electrode assembly and being plate-shaped, wherein the gas diffusion layer has grooves on the surface of the separator side for the flow of the reactant gases.

[0061] The fuel cell unit of this method includes: a separator, which is parallel to the surface direction of the membrane electrode assembly and is flat; and a gas diffusion layer, which has grooves on the surface of the separator side for the flow of reactant gases. Therefore, compared with a structure that provides grooves on the separator, the overall thickness of the fuel cell unit can be reduced while ensuring the thickness of the gas diffusion layer. This restricts the movement of reactant gases in the thickness direction. Therefore, the fuel cell unit can be made thinner while suppressing pressure loss in the gas diffusion layer.

[0062] (2) In the fuel cell cell of the above manner, the groove may also be formed as a rectangle in the cross section of the gas diffusion layer cut in a direction perpendicular to the direction of the flow of the reaction gas.

[0063] In this fuel cell design, the channel is formed in a rectangular cross-section within the gas diffusion layer, which is cut perpendicular to the direction of the reactant gas flow. Therefore, compared to structures with a sinusoidal channel shape, the contact area between the gas diffusion layer and the separator can be increased while ensuring the cross-sectional area of ​​the channel. Consequently, even when pressure is applied along the thickness direction of the fuel cell cell, localized pressure on the gas diffusion layer can be suppressed, thus preventing damage to the fuel cell cell and a decrease in power generation performance.

[0064] (3) In the fuel cell cell of the above manner, the gas diffusion layer may also have two parts located at different positions in the thickness direction of the gas diffusion layer and each having a small hole, and the other part, which is farther away from the membrane electrode assembly than one part, has the small hole with a smaller diameter than the one part.

[0065] According to this method, the fuel cell cell has two portions of a gas diffusion layer located at different positions along its thickness and each having a small pore. The other portion, farther from the membrane electrode assembly than one portion, has pores with a smaller diameter. Therefore, water present in the gas diffusion layer, which is typically composed of a hydrophilic porous metal, can be easily drained from the side closer to the membrane electrode assembly to the side farther away. More specifically, because the metal particles are closer together in the smaller pore sizes of the gas diffusion layer, the water adsorption force is stronger. This attracts water to the side of the gas diffusion layer away from the membrane electrode assembly, improving the drainage performance of the gas diffusion layer.

[0066] (4) In the fuel cell cell of the above manner, the gas diffusion layer may also have a through flow path that extends through the thickness direction and allows the reaction gas to flow.

[0067] According to this method, the gas diffusion layer of the fuel cell has a through-flow path that extends in the thickness direction and allows the reactant gas to flow. Therefore, the reactant gas can be supplied to the membrane electrode assembly side via the through-flow path. Thus, even in the presence of water in the gas diffusion layer, the path of the reactant gas can be ensured, and the reduction in reactant gas supply efficiency can be suppressed.

Claims

1. A fuel cell unit that generates electricity through the reaction of reactant gases, wherein, have: A membrane electrode assembly having an electrolyte membrane and a catalyst layer; A gas diffusion layer, stacked on the membrane electrode assembly, is composed of a porous metal body; and A separator, stacked on the gas diffusion layer, is parallel to the surface direction of the membrane electrode assembly and is flat. The gas diffusion layer has grooves on the side of the partition plate for the flow of the reactant gas.

2. The fuel cell unit according to claim 1, wherein, The groove is formed in a rectangular shape in the cross-section of the gas diffusion layer cut in a direction perpendicular to the direction of the flow of the reactant gas.

3. The fuel cell unit according to claim 1, wherein, The gas diffusion layer has two portions located at different positions in the thickness direction of the gas diffusion layer and each having a small hole, and the other portion, which is farther away from the membrane electrode assembly than one portion, has a small hole with a smaller diameter than the first portion.

4. The fuel cell unit according to any one of claims 1 to 3, wherein, The gas diffusion layer has a through flow path that extends in the thickness direction and allows the reactant gas to flow through.

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