Fuel cell

Abstract

To provide a technique for achieving a uniform current density distribution in a fuel cell.SOLUTION: A fuel cell 100 of the present disclosure includes an anode separator 20, a cathode separator 30, a membrane electrode assembly 10 including an anode 13, a cathode 16 and an electrolyte membrane 12, an oxidant gas passage 50 partitioned by a plurality of first ribs 51, a fuel gas passage 40, and a coolant passage 60 provided so as to be separated from the oxidant gas passage 50. When areas corresponding to an upstream area and a downstream area of the coolant passage 60 on a surface of the cathode 16 facing the cathode separator 30 are defined as a first cathode area 16a and a second cathode area 16b, respectively, a ratio of a contact area between the second cathode area 16b and the first ribs 51 occupied in the second cathode area 16b is greater than a ratio of a contact area between the first cathode area 16a and the first ribs 51 occupied in the first cathode area 16a.SELECTED DRAWING: Figure 1B

Description

[Technical Field]

[0001] The present disclosure relates to fuel cells. [Background technology]

[0002] Further improvements in fuel cell performance are required to effectively utilize hydrogen, one of the next-generation energy sources. In order to improve fuel cell performance, it is important to increase the power generated per unit cell. One method for increasing the power generated per unit cell is to uniformly distribute the current density in the in-plane direction of the unit cell.

[0003] Patent Document 1 describes that the cross-sectional area of ​​the oxidant gas flow channel increases from the end to the center of the separator. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-174648 Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present disclosure is to provide a technique for achieving uniform current density distribution in a fuel cell. [Means for solving the problem]

[0006] The present disclosure provides: an anode separator; a cathode separator; and a membrane electrode assembly including an anode, a cathode, and an electrolyte membrane, the membrane electrode assembly being disposed between the anode separator and the cathode separator; an oxidant gas flow path provided between the cathode and the cathode separator and partitioned by a plurality of first ribs; a fuel gas flow channel provided between the anode and the anode separator and partitioned by a plurality of second ribs; a coolant flow channel provided so as to be separated from the oxidant gas flow channel by the cathode separator; Equipped with When a region of the cathode surface facing the cathode separator that corresponds to the upstream region of the refrigerant flow path is defined as a first cathode region, and a region of the cathode surface that corresponds to the downstream region of the refrigerant flow path is defined as a second cathode region, the area of ​​the first cathode region is equal to the area of ​​the second cathode region; a ratio of a contact area between the second cathode region and the plurality of first ribs to an area of ​​the second cathode region is larger than a ratio of a contact area between the first cathode region and the plurality of first ribs to an area of ​​the first cathode region; A fuel cell is provided. [Effects of the Invention]

[0007] According to the present disclosure, it is possible to achieve a more uniform current density distribution in a fuel cell. [Brief explanation of the drawings]

[0008] [Figure 1A] 1 is a schematic cross-sectional view of a fuel cell stack according to a first embodiment; [Figure 1B] Enlarged view of part of Figure 1A [Figure 2] First plan view of the anode separator [Figure 3] Top view of the cathode separator [Figure 4] Second plan view of the anode separator [Figure 5] FIG. 2 is a second plan view of the anode separator showing another shape of the refrigerant flow path; DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) At the time the inventors conceived this disclosure, it was believed that improving the power generation efficiency of fuel cells required efficient supply of hydrogen and oxygen across the entire electrode surface and maintaining an appropriate water content in the electrolyte membrane and catalyst layer to maintain high proton conductivity and uniform current distribution. Meanwhile, cooling is required to sustain power generation, which is an exothermic reaction, for extended periods. In many cases, a fuel cell stack was controlled at an appropriate temperature by providing a coolant channel on the side of the separator opposite the electrode surface. However, because the coolant temperature increases from the upstream to downstream sides of the coolant channel, the electrode surface downstream of the coolant channel becomes hotter than the electrode surface upstream of the coolant channel. As a result, the amount of saturated water vapor in the gas channel downstream of the coolant channel increases, reducing the relative humidity and lowering the water content of the electrolyte membrane and catalyst layer below the appropriate level, resulting in non-uniform current distribution. One solution would be to increase the amount of water vapor in the gas channel, but this could lead to excess water in the coolant channel upstream, where the coolant temperature is lower, or to gas clogging due to condensation in the gas channel, resulting in non-uniform current distribution. There is a trade-off between a deficiency in the moisture content on the downstream side of the coolant flow path and an excess in the moisture content on the upstream side of the coolant flow path.

[0010] Under these circumstances, the inventors focused on the refrigerant flow channels and came up with the idea of ​​controlling the moisture content of the electrolyte membrane and catalyst layer by increasing or decreasing the contact area of ​​the ribs of the gas flow channels with the gas diffusion layer. By controlling the moisture content of the catalyst layer according to the flow direction of the refrigerant flow channels, it is possible to improve proton conductivity and make the current density distribution in the in-plane direction of the membrane electrode assembly uniform.

[0011] Hereinafter, embodiments will be described in detail with reference to the drawings. However, unnecessary detailed description may be omitted. For example, detailed description of already well-known matters or redundant description of substantially the same configuration may be omitted.

[0012] The accompanying drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter recited in the claims.

[0013] (Embodiment 1) Hereinafter, the first embodiment will be described with reference to FIGS.

[0014] [1-1.Configuration] 1A is a schematic cross-sectional view of a fuel cell stack 200 according to Embodiment 1. The fuel cell stack 200 includes a plurality of fuel cells 100 stacked one on top of the other.

[0015] The fuel cell 100 includes a membrane electrode assembly 10, an anode separator 20, and a cathode separator 30. The membrane electrode assembly 10 is disposed between the anode separator 20 and the cathode separator 30. The fuel cell 100 is, for example, a polymer electrolyte fuel cell.

[0016] The membrane electrode assembly 10 can also be used in other electrochemical devices, such as a hydrogen purification device for purifying hydrogen.

[0017] The membrane electrode assembly 10 includes an anode 13, an electrolyte membrane 12, and a cathode 16. The anode 13 is bonded to one surface of the electrolyte membrane 12. The cathode 16 is bonded to the other surface of the electrolyte membrane 12.

[0018] The membrane electrode assembly 10 may include a frame 19. The frame 19 is disposed around the membrane electrode assembly 10 and fixes the membrane electrode assembly 10 between the anode separator 20 and the cathode separator 30. The frame 19 maintains airtightness around the membrane electrode assembly 10. The frame 19 serves to prevent the fuel gas and the oxidant gas from mixing and to electrically separate the anode separator 20 and the cathode separator 30. An insulating member can be used as the frame 19. The frame 19 is typically made of resin.

[0019] The electrolyte membrane 12 is disposed between the anode 13 and the cathode 16. The electrolyte membrane 12 is made of a polymer material having proton conductivity. For example, the electrolyte membrane 12 is a membrane made of a perfluorocarbon sulfonic acid-based polymer material having sulfonic acid groups, or a hydrocarbon-based polymer material.

[0020] The anode 13 includes an anode catalyst layer 14 and an anode gas diffusion layer 15. The anode catalyst layer 14 is disposed between the electrolyte membrane 12 and the anode gas diffusion layer 15. The cathode 16 includes a cathode catalyst layer 17 and a cathode gas diffusion layer 18. The cathode catalyst layer 17 is disposed between the electrolyte membrane 12 and the cathode gas diffusion layer 18.

[0021] The anode catalyst layer 14 has a function of promoting an electrochemical reaction that dissociates hydrogen molecules into protons. The anode catalyst layer 14 includes an electrode catalyst and a polymer electrolyte. The anode catalyst layer 14 may include, as the electrode catalyst, carbon particles carrying catalyst particles and a polymer electrolyte.

[0022] The anode gas diffusion layer 15 has the function of supplying fuel gas (anode gas) to the anode catalyst layer 14 and the function of receiving electrons from the anode catalyst layer 14. The anode gas diffusion layer 15 is made of a gas-permeable and electrically conductive material. The anode gas diffusion layer 15 has, as its main material, for example, an electrically conductive porous body. An example of the porous body is a carbon fiber aggregate such as carbon paper.

[0023] The cathode catalyst layer 17 has a function of promoting an electrochemical reaction that produces water from protons and oxygen. The cathode catalyst layer 17 includes an electrode catalyst and a polymer electrolyte. The cathode catalyst layer 17 may include, as the electrode catalyst, carbon particles carrying catalyst particles and a polymer electrolyte. The carbon particles may be mesoporous carbon particles. The cathode catalyst layer 17 may further include conductive fibers.

[0024] The cathode gas diffusion layer 18 has the function of supplying an oxidant gas (cathode gas) to the cathode catalyst layer 17 and the function of transferring electrons to the cathode catalyst layer 17. The cathode gas diffusion layer 18 is made of a gas-permeable and electrically conductive material. The cathode gas diffusion layer 18 contains, for example, an electrically conductive porous body as its main material. An example of the porous body is a carbon fiber aggregate such as carbon paper.

[0025] An example of the fuel gas is a hydrogen-containing gas. The hydrogen-containing gas may be a gas produced from hydrocarbons by steam reforming, or may be pure hydrogen gas with a hydrogen concentration of 99% or more. An example of the oxidant gas is air.

[0026] The fuel cell 100 includes an oxidant gas flow path 50 , a fuel gas flow path 40 , and a coolant flow path 60 .

[0027] The oxidant gas flow field 50 is provided between the cathode 16 and the cathode separator 30. An oxidant gas is supplied to the cathode 16 through the oxidant gas flow field 50. FIG. 1B is an enlarged view of a portion IB in FIG. 1A. As shown in FIG. 1B, in this embodiment, the oxidant gas flow field 50 is partitioned by a plurality of first ribs 51. Grooves serving as the oxidant gas flow fields 50 are formed between the first ribs 51. The grooves serving as the oxidant gas flow fields 50 are provided in the cathode separator 30. However, the oxidant gas flow fields 50 may be formed by a member separate from the cathode separator 30.

[0028] The fuel gas flow field 40 is provided between the anode 13 and the anode separator 20. Fuel gas is supplied to the anode 13 through the fuel gas flow field 40. As shown in FIG. 1B , in this embodiment, the fuel gas flow field 40 is partitioned by a plurality of second ribs 41. Grooves serving as the fuel gas flow field 40 are formed between the second ribs 41. The grooves serving as the fuel gas flow field 40 are provided in the anode separator 20. However, the fuel gas flow field 40 may be formed of a member separate from the anode separator 20.

[0029] The anode separator 20 and the cathode separator 30 are each made of a conductive material such as carbon or metal, and may be provided with a corrosion-resistant coating such as resin or plating to prevent corrosion.

[0030] The coolant flow channel 60 is separated from the oxidant gas flow channel 50 by the cathode separator 30. A coolant such as brine or water is supplied to the coolant flow channel 60. As shown in FIG. 1B , in this embodiment, the coolant flow channel 60 is partitioned by a plurality of third ribs 61. Grooves serving as the coolant flow channel 60 are formed between the third ribs 61. The grooves serving as the coolant flow channel 60 are provided in the anode separator 20. That is, the fuel gas flow channel 40 is provided on the first surface 21 of the anode separator 20, and the coolant flow channel 60 is provided on the second surface 22 of the anode separator 20. The first surface 21 and the second surface 22 of the anode separator 20 refer to the two main surfaces of the plate-like anode separator 20. In this specification, the term "main surface" refers to the surface having the largest area of ​​the plate-like member. The surface that contacts the anode 13 is the first surface 21, and the surface that contacts the cathode separator 30 is the second surface 22.

[0031] The coolant flow channel 60 may be formed by a member separate from the anode separator 20. The coolant flow channel 60 may be disposed between the anode separator 20 and the cathode separator 30 of adjacent fuel cells 100.

[0032] In the example shown in FIG. 1B, coolant flow path 60 is configured so that the coolant flows in the direction shown by the white arrow, that is, from the upstream side at the bottom of the figure to the downstream side at the top of the figure.

[0033] 1B, the refrigerant flow path 60 includes an upstream region 6a and a downstream region 6b. In this embodiment, the upstream region 6a of the refrigerant flow path 60 is a region of the refrigerant flow path 60 that is close to an inlet 60a of the refrigerant flow path 60, which will be described later, and the downstream region 6b of the refrigerant flow path 60 is a region of the refrigerant flow path 60 that is close to an outlet 60b of the refrigerant flow path 60, which will be described later.

[0034] Of the surface of the cathode 16 facing the cathode separator 30, a region corresponding to the upstream region 6a of the refrigerant flow path 60 is defined as the first cathode region 16a, and a region corresponding to the downstream region 6b of the refrigerant flow path 60 is defined as the second cathode region 16b. The area of ​​the first cathode region 16a is equal to the area of ​​the second cathode region 16b. In this embodiment, the proportion of the contact area between the second cathode region 16b and the multiple first ribs 51 in the area of ​​the second cathode region 16b is larger than the proportion of the contact area between the first cathode region 16a and the multiple first ribs 51 in the area of ​​the first cathode region 16a.

[0035] Because the temperature downstream of the refrigerant flow channel 60 is higher than the temperature upstream of the refrigerant flow channel 60, the amount of saturated water vapor increases in the oxidant gas flow channel 50 adjacent to the downstream side of the refrigerant flow channel 60, causing a decrease in relative humidity. When the relative humidity in the oxidant gas flow channel 50 decreases, the moisture content decreases downstream of the refrigerant flow channel 60. However, if the proportion of the contact area between the second cathode region 16b and the multiple first ribs 51 in the area of ​​the second cathode region 16b is larger than the proportion of the contact area between the first cathode region 16a and the multiple first ribs 51 in the area of ​​the first cathode region 16a, the amount of moisture discharged from the cathode catalyst layer 17 to the oxidant gas flow channel 50 via the cathode gas diffusion layer 18 decreases in the downstream region 6b of the refrigerant flow channel 60. In other words, the amount of moisture remaining in the cathode gas diffusion layer 18 increases. This increases the moisture content in the downstream region 6b of the refrigerant flow channel 60, thereby improving the proton conductivity of the electrolyte membrane 12, the cathode catalyst layer 17, and the anode catalyst layer 14. This makes it possible to uniformize the current density distribution in the in-plane direction of the membrane electrode assembly 10, thereby realizing a highly efficient fuel cell 100.

[0036] In this embodiment, the surface of the cathode 16 facing the cathode separator 30 specifically refers to the surface of the cathode gas diffusion layer 18 facing the cathode separator 30 .

[0037] The proportion of the contact area between the cathode 16 surface facing the cathode separator 30 and the plurality of first ribs 51 may increase stepwise from the upstream region 6a to the downstream region 6b of the refrigerant flow channel 60.

[0038] As long as the proportion of the contact area between the second cathode region 16b and the plurality of first ribs 51 in the area of ​​the second cathode region 16b is greater than the proportion of the contact area between the first cathode region 16a and the plurality of first ribs 51 in the area of ​​the first cathode region 16a, the proportion of the contact area between the second cathode region 16b and the plurality of first ribs 51 in the area of ​​the second cathode region 16b and the proportion of the contact area between the first cathode region 16a and the plurality of first ribs 51 in the area of ​​the first cathode region 16a are not particularly limited. The proportion of the contact area between the second cathode region 16b and the plurality of first ribs 51 in the area of ​​the second cathode region 16b may be 10% or more and 90% or less. The proportion of the contact area between the first cathode region 16a and the plurality of first ribs 51 in the area of ​​the first cathode region 16a may be 10% or more and 90% or less.

[0039] Of the surface of the anode 13 that contacts the anode separator 20, the region corresponding to the upstream region 6a of the refrigerant flow path 60 is defined as the first anode region 13a, and the region corresponding to the downstream region 6b of the refrigerant flow path 60 is defined as the second anode region 13b. The area of ​​the first anode region 13a is equal to the area of ​​the second anode region 13b. In the present embodiment, the proportion of the contact area between the second anode region 13b and the multiple second ribs 41 in the area of ​​the second anode region 13b may be greater than the proportion of the contact area between the first anode region 13a and the multiple second ribs 41 in the area of ​​the first anode region 13a.

[0040] In the fuel cell 100, moisture is constantly exchanged between the anode 13 and the cathode 16 via the electrolyte membrane 12. Therefore, the discharge of moisture into the oxidant gas flow field 50 is affected not only by the structure of the oxidant gas flow field 50 on the cathode 16 side but also by the structure of the fuel gas flow field 40 on the anode 13 side. If the proportion of the contact area between the second anode region 13b and the plurality of second ribs 41 in the area of ​​the second anode region 13b is larger than the proportion of the contact area between the first anode region 13a and the plurality of second ribs 41 in the area of ​​the first anode region 13a, the moisture content in the downstream region 6b of the refrigerant flow field 60 increases, thereby further improving the proton conductivity of the electrolyte membrane 12, the cathode catalyst layer 17, and the anode catalyst layer 14. This makes it possible to more uniformly distribute current density in the in-plane direction of the membrane electrode assembly 10.

[0041] In this embodiment, the surface of the anode 13 facing the anode separator 20 specifically refers to the surface of the anode gas diffusion layer 15 facing the anode separator 20 .

[0042] The proportion of the contact area between the anode 13 surface facing the anode separator 20 and the plurality of second ribs 41 may increase stepwise from the upstream region 6a to the downstream region 6b of the refrigerant flow channel 60.

[0043] When the proportion of the contact area between second anode region 13b and the plurality of second ribs 41 in the area of ​​second anode region 13b is larger than the proportion of the contact area between first anode region 13a and the plurality of second ribs 41 in the area of ​​first anode region 13a, the proportion of the contact area between second anode region 13b and the plurality of second ribs 41 in the area of ​​second anode region 13b may be 10% or more and 90% or less. The proportion of the contact area between first anode region 13a and the plurality of second ribs 41 in the area of ​​first anode region 13a may be 10% or more and 90% or less.

[0044] When the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr1 of the first rib 51 located downstream of the refrigerant flow path 60 may be larger than the width Wr1 of the first rib 51 located upstream of the refrigerant flow path 60.

[0045] As shown in Figure 1B, when the width Wr1 of the first rib 51 located downstream of the refrigerant flow path 60 is larger than the width Wr1 of the first rib 51 located upstream of the refrigerant flow path 60, it is easy to achieve a larger proportion of the contact area between the second cathode region 16b and the multiple first ribs 51 in the area of ​​the second cathode region 16b than the proportion of the contact area between the first cathode region 16a and the multiple first ribs 51 in the area of ​​the first cathode region 16a.

[0046] In this embodiment, the upstream side of the refrigerant flow path 60 means the side closer to the inlet 60a of the refrigerant flow path 60, which will be described later, and the downstream side of the refrigerant flow path 60 means the side closer to the outlet 60b of the refrigerant flow path 60, which will be described later.

[0047] The ratio of the width Wr1 of the first rib 51 located on the upstream side of the refrigerant flow channel 60 to the width Wr1 of the first rib 51 located on the downstream side may be 0.2 or more and 1.0 or less.

[0048] 1B, when the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr1 of the first rib 51 located on the upstream side of the refrigerant flow path 60 may be constant. The width Wr1 of the first rib 51 located on the downstream side of the refrigerant flow path 60 may be constant.

[0049] Although not shown in the figure, when the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr1 of the first rib 51 may increase stepwise from the upstream side to the downstream side of the refrigerant flow path 60.

[0050] When the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr2 of the second rib 41 located downstream of the refrigerant flow path 60 may be larger than the width Wr2 of the second rib 41 located upstream of the refrigerant flow path 60.

[0051] As shown in FIG. 1B, when the width Wr2 of the second rib 41 located downstream of the refrigerant flow path 60 is larger than the width Wr2 of the second rib 41 located upstream of the refrigerant flow path 60, it is easy to achieve a larger proportion of the contact area between the second anode region 13b and the multiple second ribs 41 in the area of ​​the second anode region 13b than the proportion of the contact area between the first anode region 13a and the multiple second ribs 41 in the area of ​​the first anode region 13a.

[0052] The ratio of the width Wr2 of the second rib 41 located on the upstream side of the refrigerant flow channel 60 to the width Wr2 of the second rib 41 located on the upstream side may be 0.2 or more and 1.0 or less.

[0053] 1B, when the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr2 of the second rib 41 located on the upstream side of the refrigerant flow path 60 may be constant. The width Wr2 of the second rib 41 located on the downstream side of the refrigerant flow path 60 may be constant.

[0054] Although not shown in the figure, when the fuel cell 100 is viewed from a direction perpendicular to the thickness direction of the membrane electrode assembly 10, the width Wr2 of the second rib 41 may increase stepwise from the upstream side to the downstream side of the refrigerant flow path 60.

[0055] The fuel gas flow channel 40 and the oxidant gas flow channel 50 are configured so that the fuel gas and the oxidant gas flow, respectively, from the first side to the second side of the membrane electrode assembly 10. The coolant flow channel 60 may be configured so that the coolant flows from the first side to the second side of the membrane electrode assembly 10, or from the second side to the first side of the membrane electrode assembly 10. When the coolant flow channel 60 is configured so that the coolant flows from the second side to the first side of the membrane electrode assembly 10, the flow of the fuel gas is opposite to the flow of the coolant, and the flow of the oxidant gas is opposite to the flow of the coolant. With this configuration, cooling of the fuel gas flow channel 40 and the downstream side of the oxidant gas flow channel 50 corresponding to the upstream side of the coolant flow channel 60 is strengthened, resulting in a significant decrease in the moisture content downstream of the oxidant gas flow channel 50 corresponding to the downstream side of the coolant flow channel 60. However, with the fuel cell 100, the moisture content of the cathode catalyst layer 17 downstream of the coolant flow channel 60 can be increased.

[0056] 1B, the first side of the membrane electrode assembly 10 is the upper side in the drawing, and the second side is the lower side in the drawing. The refrigerant flow path 60 is configured so that the refrigerant flows from the upstream side (lower side in the drawing) corresponding to the second side of the membrane electrode assembly 10 toward the downstream side (upper side in the drawing) corresponding to the first side.

[0057] The fuel gas flow path 40 has an inlet 40a and an outlet 40b. The oxidant gas flow path 50 has an inlet 50a and an outlet 50b. The coolant flow path 60 has an inlet 60a and an outlet 60b. The inlet 40a of the fuel gas flow path 40, the inlet 50a of the oxidant gas flow path 50, and the outlet 60b of the coolant flow path 60 are located on a first side of the membrane electrode assembly 10. The outlet 40b of the fuel gas flow path 40, the outlet 50b of the oxidant gas flow path 50, and the inlet 60a of the coolant flow path 60 are located on a second side of the membrane electrode assembly 10. With this configuration, the coolant flow can be made to face the flows of the fuel gas and the oxidant gas.

[0058] In this embodiment, the membrane electrode assembly 10 and the fuel cell 100 have a rectangular shape in a plan view. A first side of the membrane electrode assembly 10 and the fuel cell 100 is the side on which one of a pair of sides positioned in a direction perpendicular to the thickness direction of the membrane electrode assembly 10 is located. A second side of the fuel cell 100 is the side on which the other of the pair of sides positioned in a direction perpendicular to the thickness direction of the membrane electrode assembly 10 is located. In the example of FIG. 1 , the X direction is the thickness direction of the membrane electrode assembly 10. The Y direction and the Z direction are each perpendicular to the thickness direction of the membrane electrode assembly 10.

[0059] The Z direction is, for example, a direction parallel to the vertical direction. The X direction is, for example, a direction parallel to the horizontal direction. The Y direction is, for example, a direction parallel to the horizontal direction and perpendicular to the thickness direction of the membrane electrode assembly 10. The first side of the membrane electrode assembly 10 and the fuel cell 100 may be the upper side in the vertical direction. The second side of the membrane electrode assembly 10 and the fuel cell 100 may be the lower side in the vertical direction. In this case, the fuel gas and the oxidant gas flow from the upper side to the lower side in the vertical direction, and the coolant flows from the lower side to the upper side in the vertical direction.

[0060] In this embodiment, an inlet 40a of the fuel gas flow channel 40 is provided at one end of the fuel cell 100 in the Z direction. An outlet 40b of the fuel gas flow channel 40 is provided at the other end of the fuel cell 100 in the Z direction. The inlet 40a and outlet 40b of the fuel gas flow channel 40 penetrate the anode separator 20 and the cathode separator 30 in the thickness direction. The inlets 40a of adjacent fuel cells 100 are connected to each other. The outlets 40b of adjacent fuel cells 100 are connected to each other. This allows fuel gas to be supplied to the fuel gas flow channel 40 from outside the fuel cell stack 200, and allows unconsumed fuel gas to be discharged from the fuel gas flow channel 40 to outside the fuel cell stack 200.

[0061] In this embodiment, an inlet 50a of the oxidant gas flow channel 50 is provided at one end of the fuel cell 100 in the Z direction. An outlet 50b of the oxidant gas flow channel 50 is provided at the other end of the fuel cell 100 in the Z direction. The inlet 50a and outlet 50b of the oxidant gas flow channel 50 penetrate the anode separator 20 and the cathode separator 30 in the thickness direction. The inlets 50a of adjacent fuel cells 100 are connected to each other. The outlets 50b of adjacent fuel cells 100 are connected to each other. This allows the oxidant gas to be supplied to the oxidant gas flow channel 50 from outside the fuel cell stack 200, and allows unconsumed oxidant gas and water vapor to be discharged from the oxidant gas flow channel 50 to outside the fuel cell stack 200.

[0062] In this embodiment, an outlet 60b of the refrigerant flow path 60 is provided at one end of the fuel cell 100 in the Z direction. An inlet 60a of the refrigerant flow path 60 is provided at the other end of the fuel cell 100 in the Z direction. The inlet 60a and outlet 60b of the refrigerant flow path 60 penetrate the anode separator 20 and the cathode separator 30 in the thickness direction. The inlets 60a of adjacent fuel cells 100 are connected to each other. The outlets 60b of adjacent fuel cells 100 are connected to each other. This allows a refrigerant to be supplied to the refrigerant flow path 60 from outside the fuel cell stack 200, and allows the refrigerant to be discharged from the refrigerant flow path 60 to outside the fuel cell stack 200.

[0063] FIG. 2 is a plan view of the cathode separator 30. The plan view shown in FIG. 2 is a plan view of the surface that contacts the cathode 16. The two regions surrounded by dashed lines in FIG. 2 represent the first cathode region 16a and the second cathode region 16b of the cathode 16 projected in the X direction. As shown in FIG. 2, the proportion of the contact area between the second cathode region 16b and the multiple first ribs 51 in the area of ​​the second cathode region 16b is larger than the proportion of the contact area between the first cathode region 16a and the multiple first ribs 51 in the area of ​​the first cathode region 16a.

[0064] As shown in FIG. 2, the width of the first rib 51 located on the downstream side of the refrigerant flow path 60 may be greater than the width of the first rib 51 located on the upstream side of the refrigerant flow path 60.

[0065] At least one of the fuel gas flow field 40 and the oxidant gas flow field 50 may be a serpentine flow field. The serpentine flow field has a group of multiple flow fields arranged in parallel to one another.

[0066] In this embodiment, the oxidant gas flow field 50 is a serpentine flow field including a plurality of first portions 53 and a plurality of second portions 54. The first portions 53 extend in a direction from the first side (upper side in the figure) of the membrane electrode assembly 10 to the second side (lower side in the figure). The first portions 53 may have an arc shape in a plan view. The second portions 54 extend in a direction perpendicular to the direction from the first side to the second side of the membrane electrode assembly 10. With this configuration, the oxidant gas can be supplied to every corner of the cathode 16.

[0067] FIG. 3 is a first plan view of the anode separator 20. The first plan view shown in FIG. 3 is a plan view of the surface 20p that contacts the anode 13. The two regions surrounded by dashed lines in FIG. 3 represent the first anode region 13a and the second anode region 13b of the anode 13 projected in the X direction. As shown in FIG. 3, the proportion of the contact area between the second anode region 13b and the multiple second ribs 41 in the area of ​​the second anode region 13b may be larger than the proportion of the contact area between the first anode region 13a and the multiple second ribs 41 in the area of ​​the first anode region 13a.

[0068] As shown in FIG. 3, the width of the second rib 41 located on the downstream side of the refrigerant flow path 60 may be greater than the width of the second rib 41 located on the upstream side of the refrigerant flow path 60.

[0069] In this embodiment, the fuel gas flow path 40 is a serpentine flow path including a plurality of first portions 43 and a plurality of second portions 44. The first portions 43 extend in a direction from the first side (upper side in the figure) of the membrane electrode assembly 10 toward the second side (lower side in the figure). The first portions 43 may have an arc shape in a plan view. The second portions 44 extend in a direction perpendicular to the direction from the first side to the second side of the membrane electrode assembly 10. With this configuration, the fuel gas can be supplied to every corner of the anode 13.

[0070] 2 and 3, the flow direction of the fuel gas in the fuel gas flow field 40 is parallel to the flow direction of the oxidant gas in the oxidant gas flow field 50. This configuration makes it easier for the electrochemical reaction in the membrane electrode assembly 10 to proceed efficiently.

[0071] 2 and 3, when the fuel cell 100 is viewed in a direction parallel to the thickness direction of the membrane electrode assembly 10, the flow direction of the fuel gas in the second portion 44 of the fuel gas flow field 40 is opposite to the flow direction of the oxidant gas in the second portion 54 of the oxidant gas flow field 50. This configuration makes it easier to efficiently promote the electrochemical reaction in the membrane electrode assembly 10.

[0072] The fuel cell stack 200 is installed such that the Z direction is parallel to the vertical direction, for example. In this case, the second portion 44 of the fuel gas flow field 40 and the second portion 54 of the oxidant gas flow field 50 are both parallel to the horizontal direction.

[0073] FIG. 4 is a second plan view of the anode separator 20. The second plan view shown in FIG. 4 is a plan view of the surface 20q opposite to the surface 20p (FIG. 2) that contacts the anode 13. The surface 20q contacts the cathode separator 30. As shown in FIG. 4, the width of the third rib 61 located on the downstream side of the refrigerant flow channel 60 may be the same as the width of the third rib 61 located on the upstream side of the refrigerant flow channel 60. However, the arrangement of the third rib 61 is not limited to the example shown in FIG. 4. For example, the width of the third rib 61 may increase stepwise from the upstream side to the downstream side of the refrigerant flow channel 60, or the width of the third rib 61 may decrease stepwise from the upstream side to the downstream side of the refrigerant flow channel 60.

[0074] In this embodiment, the refrigerant flow path 60 is a serpentine flow path including a plurality of first portions 63 and a plurality of second portions 64. The first portions 63 extend in a direction from the second side (the lower side in the figure) of the membrane electrode assembly 10 toward the first side (the upper side in the figure). The first portions 63 may have an arc shape in a plan view. The second portions 64 extend in a direction perpendicular to the direction from the second side toward the first side of the membrane electrode assembly 10. With this configuration, the membrane electrode assembly 10 can be uniformly cooled and the efficiency of exhaust heat recovery can be improved.

[0075] 5 is a second plan view of the anode separator 20 showing another shape of the refrigerant flow path 60. In the example shown in Fig. 5, the refrigerant flow path 60 is not serpentine, but has multiple portions extending in a direction from the second side (the lower side in the figure) of the membrane electrode assembly 10 toward the first side (the upper side in the figure). With this configuration, the pressure loss in the refrigerant flow path 60 can be reduced, allowing the refrigerant to flow smoothly through the refrigerant flow path 60.

[0076] [1-2. Operation] The operation and function of the fuel cell stack 200 configured as above will be described below with reference to FIG. 1A.

[0077] A fuel gas, an oxidant gas, and a coolant are supplied to the fuel gas flow passage 40, the oxidant gas flow passage 50, and the coolant flow passage 60, respectively. The oxidant gas is typically air.

[0078] At the anode 13, hydrogen (H2) is converted into protons (H + ) and electrons (e - ) The protons move from the anode 13 to the cathode 16 by conduction through the electrolyte membrane 12. The electrons move from the anode 13 to the cathode 16 through an external circuit. At the cathode 16, water (H2O) is produced by an electrochemical reaction of the protons, oxygen (O2), and electrons, as expressed by the following formula (2):

[0079] H2→2H + +2e - (1) 4H + +O2+2e - →2H2O(2)

[0080] In this embodiment, the proportion of the contact area between the second cathode region 16b and the plurality of first ribs 51 in the area of ​​the second cathode region 16b is larger than the proportion of the contact area between the first cathode region 16a and the plurality of first ribs 51 in the area of ​​the first cathode region 16a. Therefore, in the downstream region 6b of the refrigerant channel 60, the amount of moisture discharged from the cathode catalyst layer 17 to the oxidant gas channel 50 via the cathode gas diffusion layer 18 is reduced. In other words, the amount of moisture remaining in the cathode gas diffusion layer 18 increases. This increases the moisture content in the downstream region 6b of the refrigerant channel 60, thereby improving the proton conductivity of the electrolyte membrane 12, the cathode catalyst layer 17, and the anode catalyst layer 14. Therefore, the current density distribution in the in-plane direction of the membrane electrode assembly 10 can be made uniform, and a highly efficient fuel cell 100 can be realized.

[0081] In the present embodiment, the proportion of the contact area between the second anode region 13b and the plurality of second ribs 41 in the area of ​​the second anode region 13b may be larger than the proportion of the contact area between the first anode region 13a and the plurality of second ribs 41 in the area of ​​the first anode region 13a. In the fuel cell 100, moisture is constantly exchanged between the anode 13 and the cathode 16 via the electrolyte membrane 12, and therefore the discharge of moisture into the oxidant gas flow field 50 is affected not only by the structure of the oxidant gas flow field 50 on the cathode 16 side but also by the structure of the fuel gas flow field 40 on the anode 13 side. When the proportion of the contact area between the second anode region 13b and the plurality of second ribs 41 in the area of ​​the second anode region 13b is larger than the proportion of the contact area between the first anode region 13a and the plurality of second ribs 41 in the area of ​​the first anode region 13a, the moisture content in the downstream region 6b of the refrigerant flow channel 60 increases further, thereby further improving the proton conductivity of the electrolyte membrane 12, the cathode catalyst layer 17, and the anode catalyst layer 14. This makes it possible to make the current density distribution in the surface direction of the membrane electrode assembly 10 more uniform.

[0082] In this embodiment, the coolant flows from the second side (lower side) to the first side (upper side), opposite to the fuel gas flow direction and the oxidant gas flow direction. This configuration enhances cooling of the downstream sides of the fuel gas flow channel 40 and the oxidant gas flow channel 50, thereby increasing the humidity of the fuel gas and the oxidant gas downstream. Increasing the humidity of the oxidant gas downstream increases the moisture content of the cathode gas diffusion layer 18 facing the downstream side of the oxidant gas flow channel 50, thereby improving the proton conductivity of the cathode catalyst layer 17. This increases the current density downstream of the oxidant gas flow channel 50, thereby uniforming the current density distribution in the in-plane direction of the membrane electrode assembly 10. Uniformizing the current density distribution improves the power generation of the fuel cell 100.

[0083] [1-3. Supplementary Notes] The above description of the embodiments discloses the following techniques.

[0084] (Technology 1) an anode separator; a cathode separator; and a membrane electrode assembly including an anode, a cathode, and an electrolyte membrane, the membrane electrode assembly being disposed between the anode separator and the cathode separator; an oxidant gas flow path provided between the cathode and the cathode separator and partitioned by a plurality of first ribs; a fuel gas flow channel provided between the anode and the anode separator and partitioned by a plurality of second ribs; a coolant flow channel provided so as to be separated from the oxidant gas flow channel by the cathode separator; Equipped with When a region of the cathode surface facing the cathode separator that corresponds to the upstream region of the refrigerant flow path is defined as a first cathode region, and a region of the cathode surface that corresponds to the downstream region of the refrigerant flow path is defined as a second cathode region, the area of ​​the first cathode region is equal to the area of ​​the second cathode region; a ratio of a contact area between the second cathode region and the plurality of first ribs to an area of ​​the second cathode region is larger than a ratio of a contact area between the first cathode region and the plurality of first ribs to an area of ​​the first cathode region; fuel cell.

[0085] With this configuration, the current density distribution in the plane direction of the membrane electrode assembly can be made uniform, and a highly efficient fuel cell can be realized.

[0086] (Technology 2) A fuel cell according to Technology 1, wherein, of the surface of the anode facing the anode separator, a region corresponding to the upstream region of the refrigerant channel is defined as a first anode region, and a region corresponding to the downstream region of the refrigerant channel is defined as a second anode region, the area of ​​the first anode region and the area of ​​the second anode region are equal, and the proportion of the contact area between the second anode region and the plurality of second ribs in the area of ​​the second anode region is greater than the proportion of the contact area between the first anode region and the plurality of second ribs in the area of ​​the first anode region. With this configuration, it is possible to make the current density distribution in the surface direction of the electrode assembly more uniform.

[0087] (Technology 3) The fuel cell according to Technology 1 or 2, wherein the fuel gas flow channel and the oxidant gas flow channel are configured so that the fuel gas and the oxidant gas flow, respectively, flow from a first side to a second side of the membrane electrode assembly, and the coolant flow channel is configured so that the coolant flows from the second side to the first side of the membrane electrode assembly. Such a configuration makes it easy to uniformize the current density distribution in the in-plane direction of the membrane electrode assembly.

[0088] (Technology 4) The fuel cell according to Technology 3, wherein the inlet of the fuel gas flow channel, the inlet of the oxidant gas flow channel, and the outlet of the coolant flow channel are located on the first side of the membrane electrode assembly, and the outlet of the fuel gas flow channel, the outlet of the oxidant gas flow channel, and the inlet of the coolant flow channel are located on the second side of the membrane electrode assembly. With this configuration, the flow of the coolant can be made to oppose the flows of the fuel gas and the oxidant gas.

[0089] (Technology 5) The fuel cell according to claim 3 or 4, wherein the flow direction of the fuel gas in the fuel gas flow field is parallel to the flow direction of the oxidant gas in the oxidant gas flow field. With this configuration, the electrochemical reaction in the membrane electrode assembly can be easily promoted efficiently.

[0090] (Technology 6) 6. The fuel cell according to any one of claims 1 to 5, wherein at least one of the fuel gas flow channel and the oxidant gas flow channel is a serpentine flow channel, and the serpentine flow channel has a plurality of flow channel groups arranged in parallel to each other. With this configuration, it is easy to efficiently proceed with the electrochemical reaction in the membrane electrode assembly. [Industrial Applicability]

[0091] The technology of the present disclosure is useful for electrochemical devices such as secondary batteries, fuel cells, and hydrogen purification devices. [Explanation of symbols]

[0092] 10 Membrane electrode assembly 12 Electrolyte membrane 13 Anode 13a First anode region 13b Second anode region 14 Anode catalyst layer 15 Anode gas diffusion layer 16 cathode 16a First cathode region 16b Second cathode region 17 Cathode catalyst layer 18 Cathode gas diffusion layer 19 Frame 20 Anode separator 30 Cathode separator 40 fuel gas flow path 41 Second Rib 50 oxidant gas flow path 51 First Rib 60 refrigerant flow path 61 Third Rib 6a Upstream area 6b Downstream area Entrance to 40a, 50a, 60a 40b,50b,60b exit 43,53,63 Part 1 44,54,64 2nd part 100 fuel cell 200 fuel cell stack

Claims

1. an anode separator; a cathode separator; a membrane electrode assembly including an anode, a cathode, and an electrolyte membrane, the membrane electrode assembly being disposed between the anode separator and the cathode separator; an oxidant gas flow path provided between the cathode and the cathode separator and partitioned by a plurality of first ribs; a fuel gas flow channel provided between the anode and the anode separator and partitioned by a plurality of second ribs; a coolant flow channel provided so as to be separated from the oxidant gas flow channel by the cathode separator; Equipped with When a region of the surface of the cathode facing the cathode separator, which corresponds to the upstream region of the refrigerant flow path, is defined as a first cathode region, and a region of the surface of the cathode facing the cathode separator, which corresponds to the downstream region of the refrigerant flow path, is defined as a second cathode region, the area of ​​the first cathode region is equal to the area of ​​the second cathode region; a ratio of a contact area between the second cathode region and the plurality of first ribs to an area of ​​the second cathode region is larger than a ratio of a contact area between the first cathode region and the plurality of first ribs to an area of ​​the first cathode region; fuel cell.

2. When a region of the anode surface facing the anode separator, which corresponds to the upstream region of the refrigerant flow path, is defined as a first anode region, and a region of the anode surface facing the anode separator, which corresponds to the downstream region of the refrigerant flow path, is defined as a second anode region, the area of ​​the first anode region is equal to the area of ​​the second anode region, a ratio of a contact area between the second anode region and the plurality of second ribs to an area of ​​the second anode region is larger than a ratio of a contact area between the first anode region and the plurality of second ribs to an area of ​​the first anode region; The fuel cell according to claim 1 .

3. the fuel gas flow channel and the oxidant gas flow channel are configured so that the fuel gas and the oxidant gas flow channel flow from a first side to a second side of the membrane electrode assembly, respectively; the refrigerant flow path is configured so that the refrigerant flows from the second side to the first side of the membrane electrode assembly. The fuel cell according to claim 1 .

4. an inlet of the fuel gas flow channel, an inlet of the oxidant gas flow channel, and an outlet of the coolant flow channel are located on the first side of the membrane electrode assembly, an outlet of the fuel gas flow channel, an outlet of the oxidant gas flow channel, and an inlet of the coolant flow channel are located on the second side of the membrane electrode assembly; The fuel cell according to claim 3 .

5. a flow direction of the fuel gas in the fuel gas flow field is parallel to a flow direction of the oxidant gas in the oxidant gas flow field; The fuel cell according to claim 3 .

6. at least one of the fuel gas flow path and the oxidant gas flow path is a serpentine flow path, The serpentine flow path has a plurality of flow path groups arranged in parallel to each other. The fuel cell according to claim 1 .

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