Solid polymer fuel cells

Abstract

To provide a polymer electrolyte fuel cell including a gas passage structure capable of improving liquid water discharge performance.SOLUTION: A polymer electrolyte fuel cell includes a membrane-electrode assembly, a cathode gas diffusion layer. an anode gas diffusion layer, a cathode separator, and an anode separator. A plurality of cathode ribs are provided between the cathode gas diffusion layer and the cathode separator. The cathode ribs each include a first rib provided on a cathode gas diffusion layer side and consisting of a gas permeable material A, and a second rib provided on a cathode separator side and consisting of a gas impermeable material A. The cathode ribs satisfy the relationship of 0.2≤c1 / e1≤0.6 where c1 represents the height of the first rib, and e1 represents the entire height of the cathode rib. A cathode gas passage formed by the cathode ribs adjacent to each other includes a throttle passage structure having at least one throttling part at the inside thereof.SELECTED DRAWING: Figure 16

Description

Technical Field

[0001] The present invention relates to a solid polymer fuel cell, and more particularly to a solid polymer fuel cell having a gas flow path structure excellent in the discharge performance of liquid water.

Background Art

[0002] A solid polymer fuel cell includes a membrane electrode assembly (MEA) in which electrodes (catalyst layers) are joined to both surfaces of an electrolyte membrane made of a solid polymer electrolyte. Also, in a solid polymer fuel cell, a gas diffusion layer is generally disposed outside the catalyst layer. The gas diffusion layer is for supplying a reaction gas and electrons to the catalyst layer, and carbon paper, carbon cloth, etc. are used. Further, a separator having a gas flow path is disposed outside the gas diffusion layer. A solid polymer fuel cell usually has a structure (fuel cell stack) in which a plurality of single cells each composed of such an MEA, a gas diffusion layer, and a separator are stacked.

[0003] Normally, a plurality of ribs are provided on the separator, and the separator is in contact with the gas diffusion layer via the ribs. In this case, electrons are exchanged between the separator and the gas diffusion layer via the ribs. Also, the reaction gas flows in a gas flow path partitioned by adjacent ribs. Further, a cooling water flow path for flowing cooling water is usually provided inside the ribs. Therefore, the temperature of the region where the rib and the gas diffusion layer are in contact is lower than that of the region outside thereof, and liquid water tends to stay in the gas diffusion layer near the contact region. When liquid water stays in the gas diffusion layer, the gas diffusion resistance increases, and the fuel cell performance may deteriorate.

[0004] Therefore, various proposals have been made conventionally to solve this problem. For example, in Patent Document 1, (a) preparing an ink for a gas diffusion layer containing carbon black, vapor grown carbon fiber, and polytetrafluoroethylene (PTFE), (b) applying the ink for a gas diffusion layer to the surface of a PET sheet to form a coating film, (c) After applying a magnetic field in the thickness direction of the coating film for a predetermined time, the coating film is dried. (d) A mask having a predetermined pattern of openings is placed on the surface of the dried coating, and gas diffusion ink is further applied through the mask to form a rib precursor. (e) Press the rib precursor. A gas diffusion layer obtained by this process is disclosed.

[0005] The document states: (A) By this method, a gas diffusion layer can be obtained in which the degree of orientation of the carbon black structure in the region that becomes the gas flow path (second region) (the degree to which the structure is oriented in the direction of film thickness) is greater than that in the region where the ribs are formed (first region), and (B) When the degree of orientation of the structure in the second region increases, more drainage paths are formed in the thickness direction of the gas diffusion layer in the second region, thus improving the drainage performance of the gas diffusion layer. It is stated.

[0006] Patent Document 2 is not intended to improve the liquid water discharge performance, (a) A reaction gas channel comprising a first reaction gas channel formed on the gas diffusion layer side and a second reaction gas channel formed on the separator side, (b) The reaction gas channel has a serpentine channel structure. The fuel cell has been disclosed.

[0007] The document states: (A) By configuring the reaction gas channel with a first reaction gas channel provided in the gas diffusion layer and a second reaction gas channel provided in the separator, it is possible to secure a sufficiently large reaction gas channel cross-sectional area while reducing the amount of separator to be molded, and (B) By providing height-adjusting ribs with low gas diffusivity between gas flow channels with a serpentine flow channel structure, it is possible to prevent hydrogen short-circuiting (the phenomenon of hydrogen flowing into an adjacent gas flow channel). It is stated.

[0008] The gas diffusion layer described in Patent Document 1 has ribs, and the entire rib is made of a mixture of carbon black, vapor-grown carbon fibers, and PTFE, whereas the separator is flat. Therefore, in the fuel cell described in Patent Document 1, it is necessary to place the cooling water channel on the outside of the flat separator, and the thickness of the cell increases by the height of the cooling water channel. This results in a problem in that the mountability of the fuel cell deteriorates.

[0009] On the other hand, Patent Document 2 describes providing a first reaction gas channel on the gas diffusion layer side in order to reduce the amount of separator to be molded. However, this document does not describe or suggest a gas channel structure that can efficiently discharge the liquid water accumulated in the gas diffusion layer, efficiently cool the fuel cell, and without worsening the mountability of the fuel cell. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Japanese Patent Publication No. 2017-168227 [Patent Document 2] Japanese Patent Publication No. 2007-157578 [Overview of the project] [Problems that the invention aims to solve]

[0011] The problem that this invention aims to solve is to provide a polymer electrolyte fuel cell equipped with a gas flow path structure that can efficiently discharge liquid water accumulated in the gas diffusion layer. Another problem that the present invention aims to solve is to provide a polymer electrolyte fuel cell that has high liquid water discharge performance and can efficiently cool the fuel cell. Furthermore, another problem that the present invention aims to solve is to provide a polymer electrolyte fuel cell that has high liquid water discharge performance and cooling efficiency, as well as excellent mountability. [Means for solving the problem]

[0012] To solve the above problems, the solid polymer fuel cell according to the present invention has the following configuration. (1) The solid polymer fuel cell includes a membrane electrode assembly in which a cathode catalyst layer and an anode catalyst layer are joined to both sides of an electrolyte membrane containing a solid polymer electrolyte, a cathode gas diffusion layer disposed outside the cathode catalyst layer, an anode gas diffusion layer disposed outside the anode catalyst layer, a cathode separator disposed outside the cathode gas diffusion layer, and an anode separator disposed outside the anode gas diffusion layer. It is provided with. (2) A plurality of cathode ribs are provided between the cathode gas diffusion layer and the cathode separator. The cathode rib includes a first rib made of a gas-permeable material A provided on the cathode gas diffusion layer side, and a second rib made of a gas-impermeable material A provided on the cathode separator side. It is provided with. (3) The cathode rib satisfies the relationship of the following formula (1). 0.2 ≦ c1 / e1 ≦ 0.6 …(1) However, c1 is the height of the first rib, e1 is the total height of the cathode rib. (4) The cathode gas flow path formed by adjacent cathode ribs has a throttle flow path structure having at least one throttle portion inside.

Effect of the Invention

[0013] By constructing the cathode rib with a first rib made of gas-permeable material A and a second rib made of gas-impermeable material A, and by using a constricted gas flow path structure, the liquid water discharge performance is improved. Furthermore, by further optimizing the structure of the cathode rib and / or cathode gas flow path, it is possible to suppress a decrease in the cooling efficiency of the fuel cell (for example, an increase in the pressure loss of the liquid transfer pump for supplying cooling water), and / or a decrease in the mountability of the fuel cell.

[0014] this is, (a) Because the contact surface between the first rib and the second rib (i.e., the region where liquid water tends to accumulate) is located near the midpoint of the flow path height, the area near the contact surface comes into contact with a gas that has a relatively high flow velocity, and the liquid water accumulated near the contact surface is more easily discharged into the cathode gas flow path, (b) Combining such a cathode rib and throttling channel structure increases the gas flow rate without significantly increasing the pressure loss in the cathode gas channel compared to a gas channel structure without these features, thereby further promoting the discharge of liquid water, and (c) Optimizing the c1 / e1 ratio allows the second rib to be used as a cooling water passage, and a cooling water passage with a relatively large cross-sectional area can be secured without increasing the thickness of the cell. This suppresses an increase in the pressure loss of the liquid transfer pump for supplying cooling water, and also suppresses a decrease in the mountability of the fuel cell. It is thought that... [Brief explanation of the drawing]

[0015] [Figure 1] This is a schematic cross-sectional view of the vicinity of the cathode rib of a polymer electrolyte fuel cell according to the present invention. [Figure 2] These are schematic cross-sectional diagrams of various constricted sections. [Figure 3] This is a schematic diagram of a cathode gas flow path with a throttling flow path structure. [Figure 4]Figure 4(A) is a schematic cross-sectional view of a conventional cathode gas flow path. Figure 4(B) is a schematic cross-sectional view of a cathode gas flow path according to the present invention. Figure 4(C) is a schematic cross-sectional view of a cathode gas flow path formed by circular ribs. [Figure 5] Figure 5(A) is a schematic diagram of a conventional gas submersion flow near a cathode rib. Figure 5(B) is a schematic diagram of a gas submersion flow near a cathode rib according to the present invention.

[0016] [Figure 6] Figure 6(A) is a schematic cross-sectional view of the cathode rib of Comparative Example 1. Figure 6(B) is a schematic cross-sectional view of the cathode rib of Example 1. Figure 6(C) is a schematic cross-sectional view of the cathode rib of Comparative Example 2. [Figure 7] This shows the oxygen diffusion resistance of the cathode ribs in Example 1 and Comparative Examples 1-2, obtained from 3D fluid simulation. [Figure 8] Figure 8(A) shows the oxygen concentration distribution near the cathode rib in Comparative Example 1. Figure 8(B) shows the oxygen concentration distribution near the cathode rib in Example 1. Figure 8(C) shows the oxygen concentration distribution near the cathode rib in Comparative Example 2.

[0017] [Figure 9] This figure shows the relationship between the humidity of the cathode supply gas and the oxygen diffusion resistance of the gas diffusion layer and the flow path. [Figure 10] These are schematic cross-sectional diagrams of the cathode rib and cathode gas channel used to evaluate the velocity distribution within the cathode gas channel. [Figure 11] This figure shows the relationship between the vertical position y of the cathode gas flow path and the normalized flow velocity U / Um in the flow direction within the cathode gas flow path. [Figure 12] This figure shows the relationship between the vertical position y of the cathode gas flow path and the average flow velocity Um needed in the cathode gas flow path to obtain a certain fluid force at that position.

[0018] [Figure 13]This figure shows the relationship between the position y in the height direction of the cathode gas flow path and the pumping loss required to obtain the same fluid force at that position. [Figure 14] This is a schematic cross-sectional view of the cooling water channel used to evaluate the pressure loss ratio. [Figure 15] This figure shows the relationship between c1 / e1 and the pressure loss ratio. [Figure 16] This diagram shows the relationship between the submerged flow ratio and pressure drop or oxygen diffusion resistance. [Modes for carrying out the invention]

[0019] One embodiment of the present invention will be described in detail below. [1. Fuel cell] The polymer electrolyte fuel cell according to the present invention is A membrane electrode assembly comprising an electrolyte membrane containing a solid polymer electrolyte, with a cathode catalyst layer and an anode catalyst layer bonded to both sides, respectively. A cathode gas diffusion layer is disposed outside the cathode catalyst layer, An anode gas diffusion layer is disposed outside the anode catalyst layer, A cathode separator is positioned outside the cathode gas diffusion layer, an anode separator disposed outside the anode gas diffusion layer, It is equipped with.

[0020] [1.1. Membrane electrode assembly] A membrane electrode assembly (MEA) consists of an electrolyte membrane containing a solid polymer electrolyte, with a cathode catalyst layer and an anode catalyst layer bonded to both sides, respectively. The cathode catalyst layer and the anode catalyst layer each consist of a composite of an electrode catalyst and a catalyst layer ionomer. In this invention, the type of solid polymer electrolyte contained in the electrolyte membrane is not particularly limited, and the optimal material can be selected according to the purpose. Similarly, the types of electrode catalysts and catalyst layer ionomers included in the catalyst layer are not particularly limited, and the most suitable materials can be selected according to the purpose.

[0021] [1.2. Cathode gas diffusion layer, anode gas diffusion layer] The cathode gas diffusion layer is located outside the cathode catalyst layer. Similarly, the anode gas diffusion layer is located outside the anode catalyst layer. The cathode gas diffusion layer and the anode gas diffusion layer are for the exchange of electrons with the MEA, or for supplying reaction gases to the MEA, respectively. Furthermore, in this invention, the cathode gas diffusion layer and the anode gas diffusion layer may each constitute part of a rib for partitioning the gas flow path. This point will be described later.

[0022] Other aspects of the materials and structure of the cathode gas diffusion layer and the anode gas diffusion layer are not particularly limited, as long as the conditions described below are met. The cathode gas diffusion layer and the anode gas diffusion layer are, A water-repellent treated substrate, A water-repellent layer formed on the catalyst layer side surface of the substrate and It is preferable that it is equipped with [this feature].

[0023] [1.2.1. Base material] In the present invention, the material of the base material is not particularly limited, as long as it satisfies the conditions described later. Examples of base material include water-repellent treated carbon paper and water-repellent treated carbon cloth. The porosity, thickness, etc., of the substrate are not particularly limited, and the optimal values ​​can be selected according to the purpose.

[0024] [1.2.2. Water-repellent layer] The water-repellent layer is formed on the catalyst layer side of the substrate. The water-repellent layer is intended to promote water drainage. The material of the water-repellent layer is not particularly limited as long as it performs this function. Generally, the water-repellent layer consists of a mixture of conductive particles made of a conductive material and a water-repellent material. Examples of conductive particles include carbon black, carbon fiber, graphite, and activated carbon. Examples of water-repellent materials include polytetrafluoroethylene, polyvinylidene fluoride (PVDF), and polyhexafluoropropylene. Furthermore, the water-repellent layer can also be made of carbon nanotube sheets. The thickness of the water-repellent layer is not particularly limited, and the optimal thickness can be selected according to the purpose.

[0025] [1.3. Cathode separator, anode separator] The cathode separator is positioned outside the cathode gas diffusion layer. The cathode separator is for supplying electrons and oxidizing gas to the cathode catalyst layer. Similarly, the anode separator is positioned outside the anode gas diffusion layer. The anode separator is for extracting electrons from the anode catalyst layer and supplying fuel gas to the anode catalyst layer. Furthermore, in this invention, the cathode separator and anode separator may constitute part of the ribs that partition the gas flow path. This point will be discussed later.

[0026] Other aspects of the materials and structure of the cathode separator and anode separator are not particularly limited, as long as the conditions described below are met. Examples of separator materials include metals and carbon.

[0027] [1.4. Cathode-Ribbed] Figure 1 shows a schematic cross-sectional view of the vicinity of the cathode rib of a polymer electrolyte fuel cell according to the present invention. Note that in Figure 1, the dimensions of each part have been appropriately enlarged or reduced from their actual dimensions for clarity. In Figure 1, the polymer electrolyte fuel cell 10 comprises a cathode catalyst layer 20, a cathode gas diffusion layer 30 located outside the cathode catalyst layer 20, and a cathode separator 40 located outside the cathode gas diffusion layer 30. The cathode gas diffusion layer 30 comprises a substrate 32 and a water-repellent layer 34. The water-repellent layer 34 is formed on the surface of the substrate 32 facing the cathode catalyst layer 20.

[0028] Multiple cathode ribs 50, 50 are provided between the cathode gas diffusion layer 30 and the cathode separator 40. The cathode gas flow path 60 is formed by adjacent cathode ribs 50, 50. In the present invention, the cathode rib 50 is A first rib 52 made of gas-permeable material A is provided on the cathode gas diffusion layer 30 side, A second rib 54 made of gas-impermeable material A is provided on the cathode separator 40 side. It is equipped with.

[0029] [1.4.1. First Rib] The first rib 52 is made of a gas-permeable material A. "Gas-permeable material A" refers to a material that has electronic conductivity and is porous enough to allow oxidizing gas to pass through under the operating conditions of the polymer electrolyte fuel cell 10. The first rib 52 may be made of the same material as the base material 32, or it may be made of a different material from the base material 32, as long as it has predetermined electronic conductivity and gas permeability.

[0030] The first rib 52 may be integrated with the base material 32, as shown in Figure 1, or it may be separate from the base material 32, although this is not shown. In the latter case, the first rib 52 may simply be in contact with the surface of the base material 32, or it may be mechanically or chemically bonded to the surface of the base material 32. Furthermore, the first rib 52 may simply be in contact with the surface of the second rib 54, or it may be mechanically or chemically bonded to the surface of the second rib 54.

[0031] [1.4.2. Second Rib] The second rib 54 is made of a gas-impermeable material A. "Gas-impermeable material A" refers to a material that has electronic conductivity and is dense enough to prevent the permeation of oxidizing gas. The second rib 54 may be made of the same material as the cathode separator 40, or it may be made of a different material from the cathode separator 40, as long as it has the predetermined electronic conductivity and gas impermeability.

[0032] The second rib 54 may be integrated with the cathode separator 40, as shown in Figure 1, or, although not shown, it may be separate from the cathode separator 40. In the latter case, the second rib 54 may simply be in contact with the surface of the cathode separator 40, or it may be mechanically or chemically bonded to the surface of the cathode separator 40.

[0033] Furthermore, a cooling water passage 42 may be provided within the second rib 54. If the interior of the second rib 54 is used as the cooling water passage 42, it becomes unnecessary to form the cooling water passage 42 separately, thus suppressing an increase in the cell thickness. Therefore, it is possible to suppress a deterioration in the mountability of the fuel cell.

[0034] [1.4.3. Height of the first rib] Cathode rib 50 must satisfy the following relationship (1): 0.2 ≤ c1 / e1 ≤ 0.6 …(1) however, c1 is the height of the first rib 52. e1 is the total height of the cathode rib 50.

[0035] Generally, during fuel cell operation, the temperature of the cathode separator 40 is lower than the temperature of the cathode gas diffusion layer 30. Therefore, liquid water tends to accumulate in the first rib 52 near the contact surface of the first rib 52 and the second rib 54. On the other hand, the flow velocity of the gas flowing through the cathode gas channel 60 is fastest at the center of the cathode gas channel 60 and decreases as it moves away from the center. Therefore, if c1 / e1 becomes too small, the contact surface of the first rib 52 and the second rib 54 will move away from the center of the cathode gas channel 60, which may reduce the liquid water discharge performance. Accordingly, c1 / e1 needs to be 0.2 or higher. Preferably, c1 / e1 is 0.25 or higher, and more preferably 0.35 or higher.

[0036] On the other hand, the interior of the second rib 54 is generally used as a cooling water passage 42. In this case, the larger c1 / e1 becomes, the smaller the cross-sectional area of ​​the cooling water passage 42 becomes. When the cross-sectional area of ​​the cooling water passage 42 is relatively small, the pressure of the liquid transfer pump needs to be increased in order to flow a predetermined amount of cooling water through the cooling water passage 42. As a result, the larger c1 / e1 becomes, the greater the pressure loss of the liquid transfer pump. Therefore, c1 / e1 needs to be 0.6 or less. Preferably, c1 / e1 is 0.55 or less.

[0037] [1.4.4. Width of the first and second ribs] The widths of the first rib 52 and the second rib 54 are not particularly limited, and the optimal value can be selected according to the purpose. In Figure 1, the widths of the first rib 52 and the second rib 54 are depicted as being the same, but this is merely an example. The widths of the first rib 52 and the second rib 54 may be different, as long as they do not hinder the gas flow within the cathode gas channel 60. Furthermore, in Figure 1, the widths of the first rib 52 and the second rib 54 are constant regardless of their position in the height direction, and the cross-section of the cathode gas flow path 60 is depicted as rectangular; however, this is merely an example. The widths of the first rib 52 and the second rib 54 may vary along the height direction of the cathode gas flow path 60.

[0038] [1.5. Cathode Gas Flow Path] The cathode gas flow path 60 is formed by adjacent cathode ribs 50, 50. In the present invention, the cathode gas flow path 60 is equipped with a throttling flow path structure. The cathode ribs 50, 50 according to the present invention have excellent liquid water discharge performance on their own, but when combined with the throttling flow path structure, the liquid water discharge performance is further improved.

[0039] Here, "aperture flow channel structure" refers to a structure having at least one aperture section inside the cathode gas flow channel 60. In this case, the shape of the cathode gas flow path 60 other than the aperture is not particularly limited. For example, the cathode gas flow path 60 may have a straight structure in which the flow path extends straight, or it may have a bend or curve in the middle. Furthermore, the cathode gas flow path 60 may have a structure that combines a so-called serpentine structure with an aperture. However, if the cathode gas flow path 60 has an alternating closure structure (a structure in which one end of the gas flow path is alternately closed), the pressure loss when gas flows through the cathode gas flow path 60 will be large. Therefore, it is preferable that the cathode gas flow path 60 has openings at both ends.

[0040] [1.5.1. Aperture Section] A "restricted area" refers to a region within the cathode gas flow path 60 where the cross-sectional area is smaller than the cross-sectional area of ​​the regions before and after it. In the present invention, the shape of the throttling portion is not particularly limited. Examples of throttling portions include narrowed portions, low ceiling portions, and bulging portions. The cathode gas flow path 60 may be provided with one of these throttling portions, or with two or more of them.

[0041] Figure 2 shows schematic cross-sectional diagrams of various constricted sections. Note that in Figure 2, the dimensions of each section have been appropriately enlarged or reduced from their actual dimensions for clarity. Figure 2(A) shows a cathode gas flow path 60 without a constriction. On one side of the cathode catalyst layer 20, a water-repellent layer 34, a substrate 32, and a cathode separator 40 are stacked in this order. The region between adjacent cathode ribs 50, 50 is the cathode gas flow path 60. Figure 2(B) shows the constricted sections 56a, 56a provided in the cathode gas flow path 60. A "constricted section" refers to a region in which the distance between the side walls of adjacent second ribs 54 is narrowed by causing the side walls of the second ribs 54 to protrude toward the cathode gas flow path 60. The constricted sections 54a may be provided on either one of the side walls, or on both.

[0042] Figure 2(C) shows the low ceiling section 56b provided in the cathode gas flow path 60. The "low ceiling section" refers to a region in which the gap between the surface of the substrate 32 and the surface of the cathode separator 40 is narrowed by extending the upper surface of the cathode separator 40 (the surface facing the substrate 32) toward the cathode gas flow path 60. Figure 2(D) shows the bulge 56c provided in the cathode gas flow path 60. The "bulge" refers to a region in which the gap between the surface of the substrate 32 and the surface of the cathode separator 40 is narrowed by extending the upper surface of the cathode separator 40 further toward the substrate 32 than the tip of the second rib 54.

[0043] [1.5.2. Area ratio of the aperture section] The aperture section preferably satisfies the following equation (2). 0.2 ≤ S1 / S0 ≤ 0.8 …(2) however, S0 is the cross-sectional area of ​​the cathode gas flow path 60 in the region without a throttling section. S1 is the cross-sectional area of ​​the cathode gas flow path 60 in the region where the throttling section is located.

[0044] Here, if the cross-sectional area of ​​the aperture is not uniform, "the cross-sectional area S1 of the region where the aperture is located" is the cross-sectional area of ​​the narrowest part of the aperture (S min ) refers to. Furthermore, if the cross-sectional area of ​​the cathode gas flow path 60 in the region without a throttling section is not uniform, then "cross-sectional area S0 in the region without a throttling section" means the maximum cross-sectional area (S) in the region without a throttling section. max ) refers to. "Submerged flow rate" refers to the amount of gas flowing through one cathode gas channel 60 that flows into an adjacent cathode gas channel 60 through the base material 32 or the first rib 52 made of a gas-permeable material of the cathode gas diffusion layer 30.

[0045] If S1 / S0 becomes too small, the pressure loss of the gas passing through the cathode gas flow path 60 may increase. Therefore, S1 / S0 is preferably 0.2 or greater. On the other hand, if S1 / S0 becomes too large, the oxygen transport effect may decrease, and the liquid water discharge performance may also decline. Therefore, S1 / S0 is preferably 0.8 or less.

[0046] [1.5.3. Length of the constricted section in the direction of the flow path] The aperture section preferably satisfies the following equation (3). 1 ≤ d / √S ≤ 3 …(3) however, d is the length of the constricted section in the flow direction. S0 is the cross-sectional area of ​​the cathode gas flow path 60 in the region without a throttling section.

[0047] Here, "length d in the flow direction of the diaphragm" is defined as the cross-sectional area of ​​the cathode gas flow path 60 being (S0 × 0.2 + S min This refers to the length in the flow direction of the region where the ratio is less than or equal to ×0.8. min As mentioned above, this is the minimum cross-sectional area of ​​the aperture. "√S0" corresponds to the length of one side of a square having the same area as the cross-sectional area of ​​the cathode gas channel 60.

[0048] If d / √S0 becomes too small, the oxygen transport effect may decrease, and the liquid discharge performance may also decline. Therefore, d / √S0 is preferably 1 or greater. On the other hand, if d / √S0 becomes too large, the pressure loss of the gas flowing through the cathode gas channel 60 may increase. Therefore, it is preferable that d / √S0 be 3 or less.

[0049] [1.5.4. Position of the aperture] Figure 3 shows a schematic diagram of a cathode gas flow path with a throttling flow path structure. Note that in Figure 3, the dimensions of each part have been appropriately enlarged or reduced from their actual dimensions for clarity. In Figure 3, cathode gas passages A (60A), B (60B), and C (60C) are formed between the second ribs 54, 54. Furthermore, diaphragm sections A (56A), B (56B), C (56C), and D (56D) are formed in cathode gas passages A (60A) to C (60C), respectively.

[0050] [A. Spacing between throttling sections within the same cathode gas flow path] The cathode gas flow path 60 (60A to 60C) preferably satisfies the following equation (4) with respect to the throttling section (56A to 56D). 0.08 ≤ P1 / L ≤ 0.4 …(4) however, P1 is the length (pitch) between the center of the aperture A(56A) located upstream of one cathode gas flow path A(60A) and the center of the aperture B(56B) located downstream of aperture A(56A) that is closest to aperture A(56A). L is the total length of the cathode gas flow path A (60A) (length from the inlet to the outlet).

[0051] P1 / L correlates with the number of throttling sections A(56A) and B(56B) formed within a single cathode gas flow path A(60A). If P1 / L becomes too small, the distance between throttling section A(56A) and throttling section B(56B) becomes excessively short. As a result, the pressure loss of the gas flowing through cathode gas flow path A(60A) may increase. Therefore, a P1 / L of 0.08 or higher is preferable. On the other hand, if P1 / L becomes too large, the distance between the throttling section A (56A) and the throttling section B (56B) becomes excessively long. As a result, the oxygen transport effect is reduced, and the liquid water discharge performance may decrease. Therefore, P1 / L is preferably 0.4 or less.

[0052] Furthermore, if three or more throttling sections are provided in a single cathode gas flow path A (60A), P1 may be the same in all cases, or it may differ depending on the location. In polymer electrolyte fuel cells, the amount of liquid water produced usually differs depending on the location. Therefore, for example, by making P1 relatively shorter in areas where the amount of liquid water produced is relatively high, and relatively longer in areas where the amount of liquid water produced is relatively low, the liquid water discharge performance can be improved without increasing pressure loss.

[0053] [B. Spacing between adjacent throttling sections within the cathode gas flow path] When throttling sections C(56C) and D(56D) are provided in adjacent cathode gas flow paths B(60B) and C(60C), respectively, the positions of throttling sections C(56C) and D(56D) in the x-axis direction (direction of gas flow) are usually not the same. This is because if the positions of throttling sections C(56C) and D(56D) in the x-axis direction are the same, the pressure loss will increase.

[0054] In contrast, when throttling sections C(56C) and D(56D) are provided in adjacent cathode gas flow paths B(60B) and C(60C), respectively, staggering the placement of throttling sections C(56C) and D(56D) may improve the liquid water discharge performance. Here, "providing alternating aperture sections C(56C) and D(56D)" means making the x-axis positions of aperture section C(56C) and aperture section D(56D) non-identical.

[0055] When adjacent cathode gas flow paths A (60A) to C (60C) are each provided with alternating throttling sections (56A to 56B), it is preferable that the cathode flow path 60 (60A to 60C) satisfies the following equation (5) with respect to the throttling sections (56A to 56D). 0.04 ≤ P² / L ≤ 0.2 …(5) however, P2 is the length (pitch) in the gas flow direction from the center of the diaphragm C(56C) provided in the cathode gas flow path B(60B) to the center of the diaphragm D(56D) provided in the cathode gas flow path C(60C) adjacent to the cathode gas flow path B(60B), which is the closest upstream or downstream of the diaphragm C(56C). L is the total length of cathode gas channels B (60B) and C (60C) (length from inlet to outlet).

[0056] If P2 / L becomes too small, the pressure loss of the gas flowing through cathode gas passages B (60B) and C (60C) may increase. Therefore, a P2 / L of 0.04 or higher is preferable. On the other hand, if the P2 / L value becomes too high, the oxygen transport effect may decrease, and the liquid water discharge performance may also decline. Therefore, a P2 / L value of 0.2 or less is preferable.

[0057] Furthermore, when multiple throttling sections are provided in cathode gas flow path B (60B) and cathode gas flow path C (60C), P2 may be the same in all cases, or it may differ depending on the location. In polymer electrolyte fuel cells, the amount of liquid water produced usually differs depending on the location. Therefore, for example, by making P2 relatively shorter in areas where the amount of liquid water produced is relatively high, and relatively longer in areas where the amount of liquid water produced is relatively low, the liquid water discharge performance can be improved without increasing pressure loss. Furthermore, we define P3 = P1 - P2. In this case, P3 may be equal to P2, or P3 may not be equal to P2.

[0058] [1.6. Anode Liv] Multiple anode ribs are provided between the anode gas diffusion layer and the anode separator. In the present invention, the structure of the anode ribs is not particularly limited. For example, the anode ribs may consist only of a gas-impermeable material B or a gas-permeable material B provided on the anode separator side, or they may have the same structure as the cathode rib 50.

[0059] In particular, anodes are A third rib made of gas-permeable material B is provided on the anode gas diffusion layer side, A fourth rib made of gas-impermeable material B is provided on the anode separator side. It is preferable that it is equipped with [this feature].

[0060] In this case, the anode rib is preferably one that satisfies the following relationship (6). 0.2 ≤ c² / e² ≤ 0.6 …(6) however, c2 is the height of the third rib, e2 is the total height of the anode rib.

[0061] Details regarding gas-permeable material B and gas-impermeable material B are the same as those for gas-permeable material A and gas-impermeable material A, so the explanation will be omitted. The details of the third and fourth ribs, and equation (6), are the same as those of the first and second ribs, and equation (1), so their explanation will be omitted.

[0062] [1.7. Structure of the anode gas flow path] The anode gas flow path is formed by adjacent anode ribs. In the present invention, the structure of the anode gas flow path is not particularly limited. The anode gas flow path may have any of the following: a straight structure, a throttled flow path structure, an alternating occlusion structure, and / or a serpentine structure. If the anode gas flow path has a throttled flow path structure, the details thereof are the same as those of the throttled flow path structure of the cathode gas flow path 60, so the explanation is omitted.

[0063] [2. Effect] If the cathode rib is constructed solely from a gas-impermeable material, liquid water tends to accumulate at the contact surface between the cathode rib and the gas diffusion layer. In this case, increasing the cathode gas flow velocity makes it easier to expel the liquid water, but it also increases the pressure loss within the cathode gas flow path. On the other hand, if the entire cathode rib is constructed of a gas-permeable material, the increase in gas diffusion resistance within the cathode gas diffusion layer caused by liquid water can be suppressed. However, if the entire cathode rib is constructed of a gas-permeable material, it becomes impossible to form cooling water channels within the cathode rib, thus increasing the cell thickness.

[0064] In contrast, if the cathode rib is constructed with a first rib made of gas-permeable material A and a second rib made of gas-impermeable material A, and the gas flow path structure is a constricted flow path structure, the liquid water discharge performance is improved. Furthermore, by further optimizing the structure of the cathode rib and / or cathode gas flow path, it is possible to suppress a decrease in the cooling efficiency of the fuel cell (for example, an increase in the pressure loss of the liquid transfer pump for supplying cooling water), and / or a decrease in the mountability of the fuel cell. This is thought to be due to the following reasons.

[0065] [2.1. Position of the contact surface between the first rib and the second rib] In this invention, the cathode rib is composed of a first rib made of a gas-permeable material A and a second rib made of a gas-impermeable material A, and the contact surface between the first rib and the second rib (i.e., the region where liquid water tends to accumulate) is located near the midpoint of the flow path height. Therefore, it is thought that the area near the contact surface comes into contact with a gas with a relatively high flow velocity, and the liquid water accumulated near the contact surface is easily discharged into the gas flow path.

[0066] Figure 4(A) shows a schematic cross-sectional view of a conventional cathode gas flow path. Figure 4(B) shows a schematic cross-sectional view of a cathode gas flow path according to the present invention. Figure 4(C) shows a schematic cross-sectional view of a cathode gas flow path formed by circular ribs. Note that in Figure 4, the dimensions of each part have been appropriately enlarged or reduced from the actual dimensions for ease of viewing.

[0067] In conventional designs, the cathode rib 50' is integrated with the cathode separator 40, as shown in Figure 4(A). As a result, liquid water tends to accumulate in the cathode gas diffusion layer 30 located beneath the cathode rib 50'. This accumulated liquid water beneath the cathode rib 50' creates significant resistance to gas transport to the cathode catalyst layer 20 located beneath the cathode rib 50'. In contrast, the cathode rib 50 according to the present invention, as shown in Figure 4(B), consists of a first rib 52 and a second rib 54, and the position where liquid water accumulates is away from the cathode catalyst layer 20. Therefore, the adverse effect on gas diffusion below the cathode rib 50 is reduced.

[0068] Furthermore, the flow velocity of the gas in the cathode gas channel 60 is not uniform; the flow velocity is highest at the center of the cathode gas channel 60 and decreases as it moves away from the center. Therefore, in the case of a conventional cathode rib 50', as shown in Figure 4(A), the liquid water accumulated below the cathode rib 50' is in contact with the slow-moving gas, making it difficult for the liquid water to be discharged. In contrast, in the case of the cathode rib 50 according to the present invention, the liquid water accumulated below the second rib 54 is in contact with a medium-velocity gas with a faster flow rate. Therefore, it is thought that the discharge of the liquid water will proceed more easily.

[0069] Furthermore, in actual fuel cells, a cathode separator 40' with rounded ribs having the shape shown in Figure 4(C) may be used. In this case, the low-speed range is further extended compared to the cathode separator 40 with angular ribs as shown in Figures 4(A) and 4(B). Therefore, when a flat cathode gas diffusion layer 30 is combined with a cathode separator 40' with rounded ribs, the discharge of liquid water becomes even less likely. In contrast, when the present invention is applied to a cathode separator 40' equipped with rounded ribs, it is believed that liquid water can be discharged more easily compared to the conventional structure.

[0070] [2.2. Combination with aperture flow channel structure] The cathode rib according to the present invention has high liquid water discharge performance because the region where liquid water is stagnant comes into contact with a gas that has a relatively high flow velocity. When such a cathode rib structure is combined with a throttling channel structure, the gas diffusion resistance is reduced without significantly increasing the pressure loss in the cathode gas channel compared to a gas channel structure without these features, and the discharge of liquid water is further promoted.

[0071] Figure 5(A) shows a schematic diagram of the conventional gas submersion flow near the cathode rib. Figure 5(B) shows a schematic diagram of the gas submersion flow near the cathode rib according to the present invention. Note that in Figure 5, the dimensions of each part have been appropriately enlarged or reduced from the actual dimensions for ease of viewing.

[0072] When a throttling channel structure is provided in the cathode gas channel 60, a submerged flow occurs beneath the cathode rib, improving the liquid water discharge performance. However, as shown in Figure 5(A), when a conventional cathode rib 50' is combined with a throttling channel structure, the submerged flow becomes curved, making it difficult for the liquid water to be discharged. In contrast, when the cathode rib 50 according to the present invention is combined with the throttling channel structure, the submerged flow becomes linear, as shown in Figure 5(B). As a result, it is believed that the discharge of liquid water can proceed more easily even when the average flow velocity of the cathode gas is relatively slow.

[0073] [2.3. Pressure loss in the liquid transfer pump] As mentioned above, the closer the c1 / e1 of the cathode rib approaches 0.5, the better the liquid water discharge performance. However, the ribs provided in the separator are often used not only to form gas passages but also as cooling water passages. Therefore, if c1 / e1 becomes too large, the cross-sectional area of ​​the cooling water passage decreases. When the cross-sectional area of ​​the cooling water passage is relatively small, the pressure of the liquid transfer pump needs to be increased in order to flow a predetermined amount of cooling water through the passage. As a result, the larger c1 / e1 becomes, the greater the pressure loss of the liquid transfer pump. On the other hand, if a cooling water channel is provided outside the cathode rib to reduce pressure loss in the liquid transfer pump, the cell thickness increases, reducing the mountability of the fuel cell.

[0074] In contrast, optimizing the c1 / e1 ratio allows the second rib to be used as a cooling water channel. Furthermore, a cooling water channel with a relatively large cross-sectional area can be secured without increasing the cell thickness. Therefore, an increase in the pressure loss of the liquid transfer pump for supplying cooling water can be suppressed. In addition, since there is no need to provide a cooling water channel outside the cathode rib, the reduction in the mountability of the fuel cell is also suppressed. [Examples]

[0075] [1. Oxygen diffusion resistance] [1.1. Test Method] Electrode area: 1cm 2 The oxygen diffusion resistance of the cells was evaluated using simulations and experiments. Figure 6(A) shows a schematic cross-sectional view of the cathode rib of Comparative Example 1. Figure 6(B) shows a schematic cross-sectional view of the cathode rib of Example 1. Figure 6(C) shows a schematic cross-sectional view of the cathode rib of Comparative Example 2. The unit of measurement for each part is "mm".

[0076] The shape of the cathode rib is, (a) The entire cathode rib 50' is made of a gas-impermeable material (Comparative Example 1), (b) The cathode rib 50 consists of a first rib 52 made of a gas-permeable material and a second rib 54 made of a gas-impermeable material, and c1 / e1 = 0.5 (Example 1), or (c) A cathode rib of 50" made entirely of a gas-permeable material (Comparative Example 2) That's what I decided.

[0077] [1.2. Results] [1.2.1. Simulation results of dry performance] Using a three-dimensional fluid simulation, the oxygen diffusion resistance was determined when an unhumidified oxidizing gas was supplied to the cathode of a cell having the shape shown in Figure 6. Figure 7 shows the oxygen diffusion resistance of the cathode ribs for Example 1 and Comparative Examples 1-2 obtained from the three-dimensional fluid simulation. Figure 8(A) shows the oxygen concentration distribution near the cathode rib of Comparative Example 1. Figure 8(B) shows the oxygen concentration distribution near the cathode rib of Example 1. Figure 8(C) shows the oxygen concentration distribution near the cathode rib of Comparative Example 2.

[0078] In Example 1, the oxygen diffusion resistance was significantly reduced compared to Comparative Example 1, and performance comparable to Comparative Example 2 was achieved (see Figure 7). This is because the oxygen diffusion resistance under the cathode rib was reduced (see Figure 8). From Figures 7 and 8, it was found that when the portion of the cathode rib on the gas diffusion layer side is made of a gas-permeable material, the oxygen diffusion resistance becomes equivalent to that when the entire cathode rib is made of a gas-permeable material.

[0079] [1.2.2. Experimental results of wet performance] Cells with the shape shown in Figure 6 were fabricated. Power generation experiments were conducted by supplying air with different humidity levels to the cathode of each cell, and the oxygen diffusion resistance was measured. The humidity of the cathode supply gas was set to 30%, 80%, or 120%. Figure 9 shows the relationship between the humidity of the cathode supply gas and the oxygen diffusion resistance of the gas diffusion layer and the flow path. Here, "oxygen diffusion resistance of the gas diffusion layer and the flow path" refers to the oxygen diffusion resistance of the gas diffusion layer and the flow path excluding the oxygen diffusion resistance of the catalyst layer.

[0080] When the humidity of the cathode supply gas was low to medium (30% or 80%), Example 1 showed higher performance than Comparative Example 1 and comparable performance to Comparative Example 2, similar to the simulation results for dry performance. On the other hand, when the humidity of the cathode supply gas was high (120%), the oxygen diffusion resistance under high humidity conditions in both Comparative Example 1 and Comparative Example 2 increased compared to that under low- and medium humidity conditions. This is thought to be because the effect of liquid water becomes stronger as the humidity of the cathode supply gas increases.

[0081] In contrast, the oxygen diffusion resistance of Example 1 under high humidity conditions was equivalent to that under low to medium humidity conditions, showing almost no change. Furthermore, the oxygen diffusion resistance of Example 1 under high humidity conditions was lower than that of Comparative Example 2, demonstrating significantly superior performance. This is thought to be because the cathode rib is composed of a gas-permeable material and a gas-impermeable material, resulting in improved liquid water discharge performance.

[0082] [2. Examination of the height of the first rib (1): Flow velocity distribution] [2.1. Test Method] Figure 10 shows schematic cross-sectional diagrams of the cathode rib and cathode gas channel used to evaluate the velocity distribution within the cathode gas channel. The width of the cathode gas channel 60 was set to 0.8 mm. The total height e1 of the cathode rib 50 was fixed at 0.6 mm, and the height c1 of the first rib 52 was fixed at 0.3 mm. At this time, assuming that the size of the droplet detaching from the substrate 32 is 100 μm, the distribution of various physical quantities at a position 50 μm away from the side wall of the cathode rib 50, which corresponds to the center of the droplet, was determined by simulation.

[0083] [2.2. Results] [2.2.1. Flow velocity distribution in the direction of the flow path] Figure 11 shows the relationship between the position y in the height direction of the cathode gas flow path and the normalized flow velocity U / Um in the flow direction within the cathode gas flow path. "Normalized flow velocity U / Um" refers to the value obtained by dividing the flow velocity U at each point by the average flow velocity Um within the cathode gas flow path 60 (=U / Um). "Flow direction" refers to the depth direction in Figure 10. From Figure 11, it can be seen that the flow velocity in the flow direction within the cathode gas flow path 60 is maximum at approximately the center of the cathode rib 50, and decreases as one approaches both ends of the cathode rib 50.

[0084] [2.2.2. Fluid forces acting on liquid droplets] Figure 12 shows the relationship between the position y in the height direction of the cathode gas channel and the average flow velocity Um needed in the cathode gas channel to obtain a certain fluid force at that position. The fluid force acting on a droplet generally depends on the square of the flow velocity. At each position in the cathode gas channel 60, the average flow velocity (Um needed) required to obtain a certain magnitude of fluid force is proportional to the square of the reciprocal of U / Um shown in Figure 11. From Figure 12, it can be seen that the Um needed near both ends of the cathode gas channel 60 is several times to more than ten times that near the center of the cathode gas channel 60. This indicates that in order to discharge the liquid water accumulated at the ends of the rib, an average flow velocity several times to more than ten times the average flow velocity required to discharge the liquid water accumulated in the center of the rib is necessary.

[0085] [2.2.3. Pumping Loss] Figure 13 shows the relationship between the position y in the height direction of the cathode gas flow path and the pumping loss required to obtain the same fluid force at that position. Note that the vertical axis of Figure 13 shows the value normalized by the pumping loss at y = 0.3 mm.

[0086] In order to expel the droplets at both ends of the cathode rib 50 using the hydrodynamic force of the cathode gas, the average flow velocity Um needs to be increased (see Figure 12). However, as the average flow velocity Um increases, the pump power required to supply the cathode gas increases, and consequently, the pumping loss also increases (see Figure 13). From Figure 13, for example, in order to keep the pumping loss at y=0.3mm or less than 1.15 times that at y=0.3mm, it is necessary to set y=0.21~0.39mm (i.e., c1 / e1=0.35~0.65).

[0087] [3. Examination of the height of the first rib (2): Pressure loss ratio] [3.1. Test Method] Figure 14 shows a schematic cross-sectional view of the cooling water channel used to evaluate the pressure loss ratio. A cathode separator 40 was placed on the surface of the cathode gas diffusion layer 30. A cathode rib 50' or a second rib 54, which is hollow inside, was integrally formed on the cathode separator 40. A first rib 52 was formed below the second rib 54. The height of the cathode rib 50' was set to e1, and the height of the first rib 52 was set to c1. Furthermore, an anode separator 80 was placed on the surface of the anode gas diffusion layer 70. An anode rib 90 with a hollow interior was integrally formed on the anode separator 80. The height of the anode rib 90 was set to e3.

[0088] Furthermore, the cathode separator 40 and the anode separator 80 were superimposed so that the cavity in the cathode rib 50' or the second rib 54 was connected to the cavity in the anode rib 90. This connected cavity was used as the cooling water flow path 42. The pressure loss of the cooling water pump was determined by simulation when the height c1 of the first rib 52 was changed from zero to e1.

[0089] [3.2. Results] Figure 15 shows the relationship between c1 / e1 and the pressure drop ratio. Note that the "pressure drop ratio" is the value obtained by normalizing the pressure drop of the cooling water flow path 42 with various c1 values ​​by the pressure drop of the cooling water flow path 42 with c1=0. Generally, the ribs of the separator are used as cooling water passages 42. Therefore, if a portion of the ribs is replaced with a gas-permeable material, the cross-sectional area of ​​the cooling water passages 42 decreases (see Figure 14). Despite the decrease in the cross-sectional area of ​​the cooling water passages 42, if the same amount of cooling water is flowed as in a cooling water passage where c1=0, the pressure loss ratio of the liquid transfer pump changes as shown in Figure 15. From Figure 15, (a) The larger c1 / e1 becomes, the larger the pressure loss ratio becomes, and (b) In order to reduce the pressure drop ratio to 2.5 or less, c1 / e1 must be 0.6 or less. You can see that.

[0090] [4. In combination with aperture channel] [4.1. Test Method] The relationship between the flow rate ratio and pressure drop or oxygen diffusion resistance when gas is flowed through cathode gas flow channels equipped with various throttling channel structures with different throttling section structures was determined by simulation. The simulation was performed under dry conditions, free from the influence of liquid water. The "submerged flow rate ratio (%)" refers to the ratio (=q1 × 100 / q0) of the submerged flow rate (q0) of various throttling flow path structures to the submerged flow rate (q0) of a standard throttling flow path structure. The standard throttling flow path structure was designed so that more than 10% of the gas flowed through the cathode gas flow path was submerged.

[0091] The shape of the cathode rib is, (a) The entire cathode rib 50' is made of a gas-impermeable material (Comparative Example 1), or (b) The cathode rib 50 consists of a first rib 52 made of a gas-permeable material and a second rib 54 made of a gas-impermeable material, and c1 / e1 = 0.5 (Example 1) That's what I decided.

[0092] [4.2. Results] Figure 16 shows the relationship between the submerged flow rate ratio and pressure drop or oxygen diffusion resistance. In Comparative Example 1, it was found that as the submerged flow rate ratio increased, the oxygen diffusion resistance decreased, but the pressure drop increased, indicating a trade-off. In contrast, when compared at the same pressure drop, Example 1 showed a significantly lower oxygen diffusion resistance than Comparative Example 1, indicating higher performance per unit of pressure drop. Furthermore, in Example 1, it was found that the oxygen diffusion resistance when the submerged flow rate ratio is 100% is reduced by approximately 20% compared to when the submerged flow rate ratio is zero (i.e., when the cathode gas flow path 60 does not have a throttling flow path structure).

[0093] Large pressure drops in the flow path not only require greater pump power, but also cause a pressure drop downstream of a full-size cell, leading to a decrease in the power generation performance of the fuel cell system. In contrast, when the cathode rib and throttling flow path structure according to the present invention are combined, the oxygen diffusion resistance can be reduced without increasing pressure drops, thus achieving higher performance than conventional technology, at least under conditions where the adverse effects of liquid water are minimal. Regarding drainage, which is necessary under wet conditions where liquid water tends to accumulate, the same effect as in the straight channel experiment can be expected. This is due to the flow velocity distribution within the channel (see Figure 4), and it is unlikely that the drainage performance due to the flow velocity distribution would be worsened by the presence of submerged flow beneath the cathode rib.

[0094] Although embodiments of the present invention have been described in detail above, the present invention is not limited in any way to the above embodiments, and various modifications are possible without departing from the spirit of the present invention. [Industrial applicability]

[0095] The fuel cell system according to the present invention can be used as an on-board power source, a stationary small generator, and the like. [Explanation of symbols]

[0096] 10 Polymer electrolyte fuel cell 20 Cathode catalyst layer 30 Cathode gas diffusion layer 40 Cathode Separators 42 Cooling water flow path 50 cathode rib 52. First Rib 54. Second Rib 60 Cathode gas flow path

Claims

1. A polymer electrolyte fuel cell with the following configuration. (1) The polymer electrolyte fuel cell is A membrane electrode assembly comprising an electrolyte membrane containing a solid polymer electrolyte, with a cathode catalyst layer and an anode catalyst layer bonded to both sides, respectively. A cathode gas diffusion layer is disposed outside the cathode catalyst layer, An anode gas diffusion layer is disposed outside the anode catalyst layer, A cathode separator is positioned outside the cathode gas diffusion layer, an anode separator disposed outside the anode gas diffusion layer, It is equipped with. (2) A plurality of cathode ribs are provided between the cathode gas diffusion layer and the cathode separator. The cathode rib is A first rib made of gas-permeable material A is provided on the cathode gas diffusion layer side, A second rib made of gas-impermeable material A is provided on the cathode separator side. It is equipped with. (3) The cathode rib satisfies the following relationship (1). 0.35≦c 1 / e 1 ≦0.55 (1) however, c 1 The height of the first rib, e 1 This is the total height of the cathode rib. (4) The cathode gas flow path formed by the adjacent cathode ribs is equipped with a throttling flow path structure having at least one throttling section inside.

2. The aforementioned aperture portion is (a) A constricted portion provided in the cathode gas flow path, (b) Low ceiling section provided in the cathode gas flow path, (c) Bulge provided in the cathode gas flow path Includes at least one selected from the group consisting of The polymer electrolyte fuel cell according to claim 1.

3. A polymer electrolyte fuel cell according to claim 1 or 2, satisfying the following formula (2). 0.2≦S 1 / S 0 ≦0.8 …(2) however, S 0 The cross-sectional area of ​​the cathode gas flow path in the region without the throttling portion, S 1 This is the cross-sectional area of ​​the cathode gas flow path in the region where the throttling portion is located.

4. A polymer electrolyte fuel cell according to any one of claims 1 to 3, satisfying the following formula (3). 1≦d / √S 0 ≦3 …(3) however, d is the length of the constricted portion in the flow direction, S 0 This is the cross-sectional area of ​​the cathode gas flow path in the region where the throttling portion is absent.

5. A polymer electrolyte fuel cell according to any one of claims 1 to 4, satisfying the following formula (4). 0.08≦P 1 / L≦0.4 …(4) however, P 1 This is the length (pitch) between the center of a diaphragm A located upstream of a cathode gas flow path A and the center of a diaphragm B located downstream of diaphragm A that is closest to diaphragm A. L is the total length of the cathode gas flow path A (length from the inlet to the outlet).

6. A polymer electrolyte fuel cell according to any one of claims 1 to 5, wherein the constricted portions are provided alternately in adjacent cathode gas flow paths.

7. A polymer electrolyte fuel cell according to claim 6 that satisfies the following formula (5). 0.04≦P 2 / L≦0.2 …(5) however, P 2 This is the length (pitch) in the gas flow direction from the center of the throttling section C provided in the cathode gas flow path B to the center of the throttling section D provided in the cathode gas flow path C adjacent to the cathode gas flow path B, which is the closest upstream or downstream of the throttling section C. L is the total length of the cathode gas flow paths B and C (length from inlet to outlet).

8. A solid polymer fuel cell according to any one of claims 1 to 7, wherein a cooling water channel is provided within the second rib.

9. A polymer electrolyte fuel cell according to any one of claims 1 to 8, further comprising the following configuration. (5) A plurality of anode ribs are provided between the anode gas diffusion layer and the anode separator. The aforementioned anode rib is A third rib made of gas-permeable material B is provided on the anode gas diffusion layer side, A fourth rib made of gas-impermeable material B is provided on the anode separator side. It is equipped with. (6) The anode rib satisfies the following relationship (6). 0.2≦c 2 / e 2 ≦0.6 …(6) however, c 2 The height of the third rib, e 2 This is the total height of the anode rib.

10. The polymer electrolyte fuel cell according to claim 9, wherein the anode gas flow path formed by adjacent anode ribs comprises a straight structure, a constricted flow path structure, an alternating occlusion structure, and / or a serpentine structure.

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