Fuel cell

Abstract

To provide technique for uniformizing 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; a fuel gas flow path 40; an oxidant gas flow path 50; and a refrigerant flow path 60. The coolant flow path 6 includes a first flow path 61 and a second flow path 62 that are independent from each other. In the surface of the anode separator 20 facing the cathode separator 20, the surface of the cathode separator 20 facing the anode separator 20, or the surface of another member, when a region existing on an inlet side of the refrigerant flow path 6 is defined as a region A, and a region existing on an outlet side of the refrigerant flow path 6 is defined as a region B, in the region A, a ratio of an area occupied by the first flow path 61 is smaller than a ratio of an area occupied by the second flow path 62. In the region B, a ratio of an area occupied by the first flow path 61 is larger than an area occupied by the second flow path 62.SELECTED DRAWING: Figure 4B

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. To improve fuel cell performance, it is important to increase the power generation efficiency per unit cell. One way to increase the power generation efficiency per unit cell is to make the current density distribution uniform across the surface of the unit cell.

[0003] Patent Document 1 describes that a fuel cell is cooled by passing a cooling medium through a cooling mechanism disposed adjacent to the anode electrode layer or the cathode electrode layer. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-99375 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; 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; a fuel gas flow channel provided between the anode and the anode separator; an oxidant gas flow channel provided between the cathode and the cathode separator; a refrigerant flow path provided in at least one selected from the group consisting of the anode separator, the cathode separator, and a separate member disposed between the anode separator and the cathode separator; Equipped with the refrigerant flow path has a first flow path and a second flow path that are independent of each other, When a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member that is located on the inlet side of the refrigerant flow path is defined as Region A, and a region of the surface of the separate member that is located on the outlet side of the refrigerant flow path is defined as Region B, In the region A, the ratio of the area occupied by the first flow path is smaller than the ratio of the area occupied by the second flow path, In the region B, the proportion of the area occupied by the first flow path is greater than the proportion of the area occupied by the second flow path. fuel cell, to provide. [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 1] 1 is a schematic cross-sectional view of a fuel cell stack according to a first embodiment; [Figure 2] First plan view of the anode separator [Figure 3] First plan view of the cathode separator [Figure 4A] Second plan view of the anode separator [Figure 4B] FIG. 4B is a diagram showing a first region occupied by a first flow path and a second region occupied by a second flow path in FIG. 4A; [Figure 5A] FIG. 2 is a second plan view of the anode separator showing Modification 1 of the refrigerant flow path; [Figure 5B]FIG. 5B is a diagram showing a first region occupied by a first flow path and a second region occupied by a second flow path in FIG. 5A; [Figure 6A] FIG. 2 is a second plan view of the anode separator showing a second modified example of the refrigerant flow path; [Figure 6B] FIG. 6B is a diagram showing a first region occupied by a first flow path and a second region occupied by a second flow path in FIG. 6A; DETAILED DESCRIPTION OF THE INVENTION

[0009] (Findings that formed the basis of this disclosure) At the time the inventors first developed this disclosure, it was believed that improving the power generation efficiency of fuel cells required efficient supply of hydrogen and oxygen to the entire electrode surface where the power generation reaction occurs, while maintaining an appropriate water content in the electrolyte membrane and catalyst layer. Efficient supply of hydrogen and oxygen to the entire electrode surface reduces the activation overvoltage caused by the chemical reaction. Maintaining an appropriate water content in the electrolyte membrane and catalyst layer maintains high proton conductivity and reduces the resistance overvoltage caused by electrical resistance. Meanwhile, cooling is required to sustain power generation, which is an exothermic reaction, for extended periods. In many cases, a refrigerant channel is provided on the side of the separator opposite the electrode surface to control the fuel cell stack at an appropriate temperature. However, because the refrigerant temperature increases from the upstream to downstream sides of the refrigerant channel, the electrode surface located downstream of the refrigerant channel becomes hotter than the electrode surface located upstream of the refrigerant channel. As a result, the electrolyte membrane and catalyst layer dry out downstream of the refrigerant channel, resulting in a decrease in proton conductivity. A decrease in proton conductivity inhibits current flow, resulting in an uneven current density distribution from upstream to downstream.

[0010] Under these circumstances, the inventors focused on the coolant flow path to achieve a uniform current density distribution and came up with the idea of ​​suppressing the decrease in coolant temperature on the downstream side by adjusting the shape of the coolant flow path. If the decrease in coolant temperature on the downstream side can be suppressed, the proton conductivity can be improved, and current can flow more easily on the downstream side. This suppresses the non-uniform current density distribution that occurs from the upstream side to the downstream side.

[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. 1 to 6B.

[0014] [1-1.Configuration] 1 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 so that the anode separator 20 and the cathode separator 30 do not come into contact with each other, 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 prevents the fuel gas (anode gas) and the oxidant gas (cathode gas) from mixing, and electrically separates the anode separator 20 and the cathode separator 30. The frame 19 is insulating, gas permeation resistant, and water vapor permeation resistant. An insulating member can be used as the frame 19. The frame 19 may be, for example, a resin member.

[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 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 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] In this specification, the area defined by the outer edges of the anode 13 and the cathode 16 is referred to as the electrode area 101. More specifically, the electrode area 101 is the area defined by the outer edges of the anode catalyst layer 14 and the cathode catalyst layer 17. The electrode area 101 corresponds to the electrode surface where the power generation reaction occurs.

[0027] A fuel gas flow channel 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 channel 40. In this embodiment, a groove serving as the fuel gas flow channel 40 is provided in a first surface 21 of the anode separator 20. The first surface 21 and 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 of the plate-like member having the largest area. The surface in contact with the anode 13 is the first surface 21, and the surface in contact with the cathode separator 30 is the second surface 22.

[0028] An 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. In this embodiment, a groove serving as the oxidant gas flow field 50 is provided in a first surface 31 of the cathode separator 30. The first surface 31 and the second surface 32 of the cathode separator 30 refer to the two main surfaces of the plate-shaped cathode separator 30. The surface in contact with the cathode 16 is the first surface 31, and the surface in contact with the anode separator 20 is the second surface 32.

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

[0030] The fuel cell 100 further includes a refrigerant channel 60 provided in at least one selected from the group consisting of the anode separator 20, the cathode separator 30, and a separate plate-like member disposed between the anode separator 20 and the cathode separator 30. A refrigerant is supplied to the refrigerant channel 60. In this embodiment, grooves serving as the refrigerant channel 60 are formed in the second surface 22 of the anode separator 20. That is, the fuel gas channel 40 is provided in the first surface 21 of the anode separator 20, and the refrigerant channel 60 is provided in the second surface 22 of the anode separator 20. However, the position where the refrigerant channel 60 is formed is not limited to the second surface 22 of the anode separator 20, as long as it is provided so as to be separated from the oxidant gas channel 50. For example, the grooves of the refrigerant channel 60 may be formed in the second surface 32 of the cathode separator 30. The grooves of the coolant flow channels 60 may be formed so as to span the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30. The grooves of the coolant flow channels 60 may be formed in a separate member arranged between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30. The size of the area defined by the outer edges of the separate member may be the same as the size of the area defined by the outer edges of the anode separator 20 and the cathode separator 30. The coolant flow channels 60 may be arranged between the anode separator 20 and the cathode separator 30 in adjacent fuel cells 100.

[0031] 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. In this embodiment, the inlet 40a of the fuel gas flow path 40, the inlet 50a of the oxidant gas flow path 50, and the inlet 60a of the coolant flow path 60 are located on a first side (upper side in the figure) 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 outlet 60b of the coolant flow path 60 are located on a second side (lower side in the figure) of the membrane electrode assembly 10. With this configuration, the coolant flow direction can be made parallel to the flow directions of the fuel gas and the oxidant gas. Furthermore, moisture generated in the oxidant gas flow path 50 can be easily and efficiently discharged from the oxidant gas outlet 50b.

[0032] Examples of refrigerants are brine, water, antifreeze, etc. The refrigerant may also be water.

[0033] 2 is a first plan view of the anode separator 20. The first plan view of FIG. 2 is a plan view of the first surface 21 of the anode separator 20 that contacts the anode 13. In this embodiment, the fuel gas flow channel 40 is configured so that the fuel gas flows from the first side (upper side in the figure) to the second side (lower side in the figure) of the membrane electrode assembly 10. This configuration makes it easy to configure the fuel gas to flow without resisting gravity.

[0034] In this embodiment, the fuel gas flow path 40 is a serpentine flow path including a plurality of first portions 401 and a plurality of second portions 402. The first portions 401 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 401 may have an arc shape in a plan view. The second portions 402 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.

[0035] In this embodiment, in addition to the fuel gas flow field 40, the first surface 21 of the anode separator 20 is formed with a fuel gas inlet channel 43 that is connected to the fuel gas flow field 40 and introduces fuel gas to the fuel gas flow field 40, and a fuel gas outlet channel 44 that is connected to the fuel gas flow field 40 and discharges the fuel gas that has passed through the fuel gas flow field 40. As shown in FIG. 2 , the fuel gas flow field 40 is located inside the electrode region 101, and the fuel gas inlet channel 43 and the fuel gas outlet channel 44 are located outside the electrode region 101. The fuel gas inlet channel 43 is connected to a fuel gas inlet 40a that is located outside the electrode region 101. The fuel gas outlet channel 44 is connected to a fuel gas outlet 40b that is located outside the electrode region 101.

[0036] 3 is a first plan view of the cathode separator 30. The first plan view of FIG. 3 is a plan view of the first surface 31 of the cathode separator 30 that contacts the cathode 16. In this embodiment, the oxidant gas flow channel 50 is configured so that the oxidant gas flows from the first side (upper side in the figure) of the membrane electrode assembly 10 to the second side (lower side in the figure). This configuration makes it easy to configure the oxidant gas to flow without resisting gravity.

[0037] In this embodiment, the oxidant gas flow field 50 is a serpentine flow field including a plurality of first portions 501 and a plurality of second portions 502. The first portions 501 extend in a direction from a first side (upper side in the figure) of the membrane electrode assembly 10 toward a second side (lower side in the figure). The first portions 501 may have an arc shape in a plan view. The second portions 502 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.

[0038] In this embodiment, in addition to the oxidant gas flow field 50, the first surface 31 of the cathode separator 30 is formed with an oxidant gas inlet channel 53 connected to the oxidant gas flow field 50 and introducing an oxidant gas into the oxidant gas flow field 50, and an oxidant gas outlet channel 54 connected to the oxidant gas flow field 50 and discharging the oxidant gas that has passed through the oxidant gas flow field 50. As shown in FIG. 3 , the oxidant gas flow field 50 is located inside the electrode region 101, and the oxidant gas inlet channel 53 and the oxidant gas outlet channel 54 are located outside the electrode region 101. The oxidant gas inlet channel 53 is connected to an oxidant gas inlet 50a located outside the electrode region 101. The oxidant gas outlet channel 54 is connected to an oxidant gas outlet 50b located outside the electrode region 101.

[0039] 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.

[0040] FIG. 4A is a second plan view of the anode separator 20. The second plan view of FIG. 4A is a plan view of the second surface 22 of the anode separator 20 that contacts the cathode separator 30. In this embodiment, the refrigerant flow channel 60 is configured so that the refrigerant flows from the first side (upper side in the figure) of the membrane electrode assembly 10 to the second side (lower side in the figure). This configuration makes it easy to configure the refrigerant to flow without resisting gravity. Furthermore, since it is easy to strengthen cooling on the upstream side of the oxidant gas flow channel 50, it is easy to suppress an increase in the temperature of the oxidant gas on the upstream side of the oxidant gas flow channel 50.

[0041] In this embodiment, the refrigerant flow path 60 has a first flow path 61 and a second flow path 62. The first flow path 61 and the second flow path 62 are independent of each other. As shown in FIG. 4A , the flow direction of the refrigerant in the first flow path 61 is parallel to the flow direction of the refrigerant in the second flow path 62. The first flow path 61 is a serpentine flow path including a plurality of first portions 611 and a plurality of second portions 612. The second flow path 62 is a serpentine flow path including a plurality of first portions 621 and a plurality of second portions 622. The first portions 611 and the first portions 621 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 611 and the first portions 621 may have an arc shape in a plan view. The second portions 612 and the second portions 622 extend in a direction perpendicular to the direction from the first side to the second side of the membrane electrode assembly 10. This configuration makes it easy to cool the entire electrode surface.

[0042] In this embodiment, the second surface 22 of the anode separator 20 is formed with a refrigerant inlet channel 63 that is connected to the refrigerant flow channel 60 and introduces a refrigerant into the refrigerant flow channel 60, and a refrigerant outlet channel 64 that is connected to the refrigerant flow channel 60 and discharges the refrigerant that has passed through the refrigerant flow channel 60. As shown in FIG. 4A , the refrigerant flow channel 60 is located inside the electrode region 101, and the refrigerant inlet channel 63 and the refrigerant outlet channel 64 are located outside the electrode region 101. The refrigerant inlet channel 63 is connected to a refrigerant inlet 60a that is located outside the electrode region 101. The refrigerant outlet channel 64 is connected to a refrigerant outlet 60b that is located outside the electrode region 101.

[0043] 4A, i.e., from the first side (upper side in the figure) to the second side (lower side in the figure). That is, the flow direction of the coolant in the coolant flow channel 60 is parallel to the flow direction of the oxidant gas in the oxidant gas flow channel 50 and the flow direction of the fuel gas in the fuel gas flow channel 40. With this configuration, a low-temperature coolant flows upstream where the amount of heat generated is large due to the concentration of current density, and therefore the fuel cell 100 can be cooled effectively.

[0044] 4B is a diagram showing a first region 71 occupied by the first flow path 61 and a second region 72 occupied by the second flow path 62 in FIG. 4A. The first region 71 is a region where the electrode region 101 and the first flow path 61 overlap when viewed from a direction perpendicular to the second surface 22 of the anode separator 20 or the second surface 32 of the cathode separator 30. The second region 72 is a region where the electrode region 101 and the second flow path 62 overlap when viewed from a direction perpendicular to the second surface 22 of the anode separator 20 or the second surface 32 of the cathode separator 30. However, for ease of understanding, FIG. 4B shows the first region 71 as a region including the peripheral area of ​​the overlapping portion between the electrode region 101 and the first flow path 61, and the second region 72 as a region including the peripheral area of ​​the overlapping portion between the electrode region 101 and the second flow path 62.

[0045] Of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or the surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, a region located on the inlet 60a side of the refrigerant flow path 60 is defined as Region A, and a region located on the outlet 60b side of the refrigerant flow path 60 is defined as Region B. The surface of the separate member refers to either of the two main surfaces of a plate-like separate member. As shown in FIG. 4B , in this embodiment, the first region 71 is smaller than the second region 72 in Region A, and the first region 71 is larger than the second region 72 in Region B. That is, in this embodiment, the proportion of the area occupied by the first flow path 61 in Region A is smaller than the proportion of the area occupied by the second flow path 62, and the proportion of the area occupied by the first flow path 61 in Region B is larger than the proportion of the area occupied by the second flow path 62. With this configuration, the length of the first flow path 61 can be made shorter than the length of the second flow path 62 on the upstream side of the refrigerant flow path 60, thereby suppressing a temperature rise of the refrigerant flowing through the first flow path 61. Meanwhile, the length of the first flow path 61 can be made longer than the length of the second flow path 62 on the downstream side of the refrigerant flow path 60. Therefore, the low-temperature refrigerant flowing through the first flow path 61, whose temperature rise is suppressed, promotes condensation of water vapor and increases the moisture content. As a result, the proton conductivity of the downstream electrolyte membrane 12, cathode catalyst layer 17, and anode catalyst layer 14 can be improved, making it easier for current to flow downstream. This suppresses non-uniformity in the current density distribution from the upstream side to the downstream side.

[0046] Region A may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 50% of the area from the inlet 60a side of the refrigerant flow channel 60. Region B may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 50% of the area from the outlet 60b side of the refrigerant flow channel 60. In other words, the areas of Region A and Region B may be equal. With this configuration, condensation of water vapor is promoted downstream of the refrigerant flow channel 60, thereby improving the moisture content.

[0047] Region A may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 25% of the area from the inlet 60a side of the refrigerant flow channel 60. Region B may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 75% of the area from the outlet 60b side of the refrigerant flow channel 60. In other words, the area of ​​region A may be smaller than the area of ​​region B. With this configuration, condensation of water vapor is further promoted on the downstream side of the refrigerant flow channel 60, thereby further improving the moisture content.

[0048] The inlet 60a and the outlet 60b of the coolant channel 60 may be located on a center line CL that passes through the center of the second surface 22 of the anode separator 20 or the second surface 32 of the cathode separator 30 and extends in the direction of the coolant flow. In the example shown in FIG. 4A , the inlet 60a and the outlet 60b of the coolant channel 60 are located on a center line CL that passes through the center of the second surface 22 of the anode separator 20 and extends in the direction of the coolant flow. In this case, the inlet 50a of the oxidant gas channel 50 and the inlet 40a of the fuel gas channel 40 may be located symmetrically with respect to the center line CL. The outlet 50b of the oxidant gas channel 50 and the outlet 40b of the fuel gas channel 40 may be located symmetrically with respect to the center line CL.

[0049] 4A, the refrigerant flow path 60 may branch into a first flow path 61 and a second flow path 62 at a branching position 81 downstream of the inlet 60a of the refrigerant flow path 60, and the first flow path 61 and the second flow path 62 may merge at a merging position 82 upstream of the outlet 60b of the refrigerant flow path 60. With this configuration, for example, it is not necessary to provide multiple inlets 60a and outlets 60b of the refrigerant flow path 60, and the fuel cell 100 can be made simpler and more compact.

[0050] 4A, branch position 81 is provided near coolant introduction path 63 and inside electrode region 101. However, the position where branch position 81 is provided is not limited to the example shown in FIG. 4A. For example, branch position 81 may be provided in coolant introduction path 63.

[0051] 4A, the junction position 82 is located near the coolant discharge path 64 and inside the electrode region 101. However, the location of the junction position 82 is not limited to the example shown in Fig. 4A. For example, the junction position 82 may be located in the coolant discharge path 64.

[0052] Generally, the pressure loss ΔP (Pa) caused by the flow in a pipe is expressed by the following equation (1), which is based on the Darcy-Weisbach equation and the equation for the pipe friction factor in laminar flow.

[0053] △P=32μ·L / Dh 2 ·u ···(1)

[0054] In equation (1), Dh is the hydraulic equivalent diameter (m), and the cross-sectional area of ​​the pipe S (m 2 ) and the wetted perimeter (perimeter) length of the pipe A (m), it is expressed as 4S / A. u is the flow velocity (m / s), and the flow rate of the pipe Q (m 3 / s) and cross-sectional area of ​​the pipe S (m 2 ) as Q / S, where μ is the viscosity coefficient (Pa s).

[0055] The value obtained by dividing the flow path length L1 (m) of the first flow path 61 by the square of the hydraulic equivalent diameter Dh1 (m) of the first flow path 61 (L1 / Dh1 2 ) is defined as x1, and the value obtained by dividing the flow path length L2 (m) of the second flow path 62 by the square of the hydraulic equivalent diameter Dh2 (m) of the second flow path 62 (L2 / Dh2 2 ) is defined as x2. In this case, x1 and x2 may satisfy the following formula (2).

[0056] 0.9≦x2 / x1≦1.1 (2)

[0057] As is clear from equation (1), when the pressure loss △P, viscosity coefficient μ, and cross-sectional area S are fixed, the flow rate Q is (L / Dh 2 ) In this embodiment, since the pressure loss ΔP and the viscosity coefficient μ of the first flow path 61 and the second flow path 62 are the same, formula (2) indicates that the variation in the flow rate of the refrigerant flowing through the first path 61 and the second path 62 is suppressed. Therefore, when x1 and x2 satisfy formula (2), the refrigerant can be supplied uniformly over the entire electrode surface, thereby suppressing an increase in proton conductivity due to a local temperature rise and the resulting non-uniformity in the current density distribution, thereby obtaining a more efficient fuel cell 100.

[0058] In this embodiment, the membrane electrode assembly 10 and the fuel cell 100 have a rectangular shape having long and short sides in a plan view. A first side (upper side in the figure) 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 (lower side in the figure) 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 other words, the first side of the membrane electrode assembly 10 may be the side on which one of the pair of short sides of the rectangle is located, and the second side of the membrane electrode assembly 10 may be the side on which the other of the pair of short sides of the rectangle is located. This configuration makes it easy to configure the fuel gas, oxidant gas, and refrigerant to flow without resisting gravity.

[0060] In this embodiment, a fuel gas inlet 40a is provided at one end of the fuel cell 100 in the Z direction. A fuel gas outlet 40b is provided at the other end of the fuel cell 100 in the Z direction. The fuel gas inlet 40a and the fuel gas outlet 40b 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 path 40 from outside the fuel cell stack 200, and allows unconsumed fuel gas, water, and water vapor to be discharged from the fuel gas flow path 40 to outside the fuel cell stack 200.

[0061] In this embodiment, an oxidant gas inlet 50a is provided at one end of the fuel cell 100 in the Z direction. An oxidant gas outlet 50b is provided at the other end of the fuel cell 100 in the Z direction. The oxidant gas inlet 50a and the oxidant gas outlet 50b 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 oxidant gas to be supplied to the oxidant gas flow path 50 from outside the fuel cell stack 200, and allows unconsumed oxidant gas, water, and water vapor to be discharged from the oxidant gas flow path 50 to outside the fuel cell stack 200.

[0062] In this embodiment, a refrigerant inlet 60a is provided at one end of the fuel cell 100 in the Z direction. A refrigerant outlet 60b is provided at the other end of the fuel cell 100 in the Z direction. The refrigerant inlet 60a and the refrigerant outlet 60b 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 from outside the fuel cell stack 200 to the refrigerant flow path 60, and allows the refrigerant to be discharged from the refrigerant flow path 60 to outside the fuel cell stack 200.

[0063] As described above, in this embodiment, the membrane electrode assembly 10 and the fuel cell 100 have a rectangular shape having long and short sides in a plan view. The first portion 401 of the fuel gas flow field 40 may be arranged parallel to a pair of long sides of the rectangle. In this case, the second portion 402 of the fuel gas flow field 40 may be arranged parallel to a pair of short sides of the rectangle. This configuration makes it easier to efficiently promote the electrochemical reaction in the membrane electrode assembly 10.

[0064] The first portion 501 of the oxidant gas flow field 50 may be arranged parallel to a pair of long sides of the rectangle. In this case, the second portion 502 of the oxidant gas flow field 50 may be arranged parallel to a pair of short sides of the rectangle. With this configuration, a temperature gradient can be created along the flow direction of the oxidant gas flow field 50, making it easier to achieve a uniform current density distribution. Furthermore, the length of the oxidant gas flow field 50 can be increased, making it easier to efficiently discharge moisture generated in the oxidant gas flow field 50. Furthermore, it makes it easier to efficiently promote the electrochemical reaction in the membrane electrode assembly 10.

[0065] The first portions 611 and 621 of the coolant flow path 60 may be arranged parallel to a pair of long sides of the rectangle. In this case, the second portions 612 and 622 of the coolant flow path 60 may be arranged parallel to a pair of short sides of the rectangle. With this configuration, a temperature gradient can be easily created along the flow direction of the oxidant gas flow path 50, making it easy to achieve a uniform current density distribution along the flow direction.

[0066] 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 402 of the fuel gas flow path 40, the second portion 502 of the oxidant gas flow path 50, and the second portions 612 and 622 of the coolant flow path 60 are each parallel to the horizontal direction.

[0067] The shape of the refrigerant flow path 60 in the first embodiment is not limited to the shape shown in Figures 4A and 4B. Below, we will explain modified examples of the refrigerant flow path 60. In the modified examples explained below, elements common to the above-mentioned refrigerant flow path 60 will be given the same reference numerals, and explanations thereof may be omitted.

[0068] (Variation 1) 5A is a second plan view of the anode separator 20 illustrating a first modification of the refrigerant flow path 60. In the first modification shown in FIG. 5A, the inlet 60a and the outlet 60b of the refrigerant flow path 60 are positioned on a center line CL that passes through the center of the second surface 22 of the anode separator 20 and extends in the direction of the refrigerant flow, and the first flow path 61 and the second flow path 62 are arranged symmetrically with respect to the center line CL. In this manner, the inlet 60a and the outlet 60b of the refrigerant flow path 60 are positioned on a center line CL that passes through the center of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member arranged between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30 and extends in the direction of the refrigerant flow, and the first flow path 61 and the second flow path 62 may be arranged symmetrically with respect to the center line CL. With this configuration, the coolant can be supplied symmetrically, which prevents the formation of an asymmetric current density distribution, thereby making it possible to obtain a more efficient fuel cell 100.

[0069] 5A, the first flow path 61 may have a first sub-flow path 61a and a second sub-flow path 61b that are independent of each other. The second flow path 62 may have a first sub-flow path 62a and a second sub-flow path 62b that are independent of each other. The first flow path 61 may be disposed between the first sub-flow path 62a and the second sub-flow path 62b of the second flow path 62. This configuration makes it easy to dispose the first flow path 61 and the second flow path 62 symmetrically with respect to the center line CL.

[0070] 5A, the refrigerant flow path 60 may branch into a first flow path 61 and a second flow path 62 at a branching position 81 downstream of the inlet 60a of the refrigerant flow path 60, and the second flow path 62 may branch into a first sub-flow path 62a and a second sub-flow path 62b on either side of the first flow path 61. The first sub-flow path 62a, the first flow path 61, and the second sub-flow path 62b may merge at a merging position 82 upstream of the outlet 60b of the refrigerant flow path 60.

[0071] 5A, the first flow path 61 may branch into a first sub-flow path 61a and a second sub-flow path 61b at a branch position 83 located downstream of the branch position 81 and upstream of the junction position 82. The first sub-flow path 61a and the second sub-flow path 61b may merge at a junction position 84 located downstream of the branch position 83 and upstream of the junction position 82.

[0072] 5B is a diagram showing a first region 71 occupied by the first flow path 61 and a second region 72 occupied by the second flow path 62 in FIG. 5A. As shown in FIG. 5B, also in Modification 1, the proportion of the area occupied by the first flow path 61 in region A is smaller than the proportion of the area occupied by the second flow path 62, and the proportion of the area occupied by the first flow path 61 in region B is larger than the proportion of the area occupied by the second flow path 62.

[0073] Region A may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 50% of the area from the inlet 60a side of the refrigerant flow channel 60. Region B may be a region of the second surface 22 of the anode separator 20 or the second surface 32 of the cathode separator 30, occupying 50% of the area from the outlet 60b side of the refrigerant flow channel 60. In other words, the area of ​​Region A and the area of ​​Region B may be equal.

[0074] Region A may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 25% of the area from the inlet 60a side of the refrigerant flow channel 60. Region B may be a region of the second surface 22 of the anode separator 20 or the second surface 32 of the cathode separator 30, occupying 75% of the area from the outlet 60b side of the refrigerant flow channel 60. In other words, the area of ​​region A may be smaller than the area of ​​region B.

[0075] As shown in FIG. 5B, in the first modification, the branching position 83 and the joining position 84 may be provided in the region B.

[0076] (Variation 2) Fig. 6A is a second plan view of the anode separator 20 showing Modification 2 of the refrigerant flow path 60. Fig. 6B is a diagram showing the first region 71 occupied by the first flow path 61 and the second region 72 occupied by the second flow path 62 in Fig. 6A.

[0077] Of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or the surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, a region having 25% of the area from the inlet 60a side of the refrigerant flow channel 60 is defined as Region C, and a region having 75% of the area from the outlet 60b side of the refrigerant flow channel 60 is defined as Region D. As shown in FIGS. 6A and 6B , in Modification 2, the branch position 81 is provided in Region D. In other words, in Modification 2, the refrigerant flow channel 60 does not branch into the first flow channel 61 and the second flow channel 62 in Region C, but rather branches into the first flow channel 61 and the second flow channel 62 in Region D. This configuration increases the flow rate of the low-temperature refrigerant circulating in Region C. This suppresses an increase in proton conductivity due to a local temperature rise on the upstream side where power generation is concentrated, thereby achieving a more efficient fuel cell 100.

[0078] As shown in Figure 6B, in variant example 2, in region A, the proportion of the area occupied by the first flow path 61 is smaller than the proportion of the area occupied by the second flow path 62, and in region B, the proportion of the area occupied by the first flow path 61 is larger than the proportion of the area occupied by the second flow path 62.

[0079] Region A may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 50% of the area from the inlet 60a side of the refrigerant flow channel 60. Region B may be a region of the second surface 22 of the anode separator 20, the second surface 32 of the cathode separator 30, or a surface of a separate member disposed between the second surface 22 of the anode separator 20 and the second surface 32 of the cathode separator 30, occupying 50% of the area from the outlet 60b side of the refrigerant flow channel 60. In other words, the area of ​​Region A and the area of ​​Region B may be equal.

[0080] As shown in FIGS. 6A and 6B , in Modification 2, the refrigerant flow path 60 in region C is a serpentine flow path including a plurality of first portions 601 and a plurality of second portions 602. The first portions 601 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 601 may have an arc shape in a plan view. The second portions 602 extend in a direction perpendicular to the direction from the first side toward the second side of the membrane electrode assembly 10. This configuration makes it easier to cool the upstream side where power generation is concentrated.

[0081] [1-2. Operation] The operation and function of the fuel cell stack 200 configured as above will be described below with reference to FIGS. 1 to 4B.

[0082] A fuel gas, an oxidant gas, and a coolant are supplied to the fuel gas flow path 40, the oxidant gas flow path 50, and the coolant flow path 60, respectively. The oxidant gas is typically air. The flow direction of the fuel gas in the fuel gas flow path 40 is parallel to the flow direction of the oxidant gas in the oxidant gas flow path 50.

[0083] 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 represented by the following formula (ii):

[0084] H2→2H + +2e - (i) 4H + +O2+2e - →2H2O (ii)

[0085] In this embodiment, in region A located on the inlet 60a side of the refrigerant flow channel 60, the proportion of the area occupied by the first flow channel 61 is smaller than the proportion of the area occupied by the second flow channel 62. In region B located on the outlet 60b side of the refrigerant flow channel 60, the proportion of the area occupied by the first flow channel 61 is larger than the proportion of the area occupied by the second flow channel 62. With this configuration, the length of the first flow channel 61 can be made shorter than the length of the second flow channel 62 on the upstream side of the refrigerant flow channel 60, thereby suppressing a temperature rise of the refrigerant flowing through the first flow channel 61. Meanwhile, the length of the first flow channel 61 can be made longer than the length of the second flow channel 62 on the downstream side of the refrigerant flow channel 60. Therefore, the low-temperature refrigerant flowing through the first flow channel 61, whose temperature rise is suppressed, promotes condensation of water vapor and increases the moisture content. As a result, the proton conductivity of the downstream electrolyte membrane 12, cathode catalyst layer 17, and anode catalyst layer 14 can be improved, making it easier for current to flow downstream. This suppresses the non-uniformity of the current density distribution from the upstream side to the downstream side.

[0086] The flow direction of the fuel gas in the fuel gas flow field 40 is preferably parallel to the flow direction of the oxidant gas in the oxidant gas flow field 50. With this configuration, the electrochemical reaction in the membrane electrode assembly 10 can be easily promoted efficiently.

[0087] The flow direction of the coolant in the coolant flow channel 60 is preferably parallel to the flow direction of the oxidant gas in the oxidant gas flow channel 50. With this configuration, a coolant with a low temperature flows upstream where the amount of heat generated is large due to the concentration of current density, and therefore the fuel cell 100 can be cooled effectively.

[0088] [1-3. Supplementary Notes] The above description of the embodiments discloses the following techniques.

[0089] (Technology 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; a fuel gas flow channel provided between the anode and the anode separator; an oxidant gas flow channel provided between the cathode and the cathode separator; a refrigerant flow path provided in at least one selected from the group consisting of the anode separator, the cathode separator, and a separate member disposed between the anode separator and the cathode separator; Equipped with the refrigerant flow path has a first flow path and a second flow path that are independent of each other, When a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member that is located on the inlet side of the refrigerant flow path is defined as Region A, and a region of the surface of the separate member that is located on the outlet side of the refrigerant flow path is defined as Region B, In the region A, the ratio of the area occupied by the first flow path is smaller than the ratio of the area occupied by the second flow path, In the region B, the proportion of the area occupied by the first flow path is greater than the proportion of the area occupied by the second flow path. fuel cell.

[0090] With this configuration, the non-uniformity of the current density distribution from the upstream side to the downstream side is suppressed.

[0091] (Technology 2) The fuel cell according to Technology 1, wherein the refrigerant flow path branches into the first flow path and the second flow path at a branching position downstream of an inlet of the refrigerant flow path, and the first flow path and the second flow path merge at a merging position upstream of an outlet of the refrigerant flow path. With this configuration, a more simple and compact fuel cell can be obtained.

[0092] (Technology 3) The fuel cell according to Technology 1 or 2, wherein the flow direction of the fuel gas in the fuel gas flow channel is parallel to the flow direction of the oxidant gas in the oxidant gas flow channel. With this configuration, the electrochemical reaction in the membrane electrode assembly 10 can be easily promoted efficiently.

[0093] (Technology 4) The fuel cell according to any one of techniques 1 to 3, wherein the flow direction of the coolant in the coolant channel is parallel to the flow direction of the oxidant gas in the oxidant gas channel. With this configuration, the fuel cell can be cooled effectively.

[0094] (Technology 5) 5. The fuel cell according to any one of techniques 1 to 4, wherein the following formula is satisfied when a value obtained by dividing a flow path length of the first flow path by the square of a hydraulic equivalent diameter of the first flow path is defined as x1, and a value obtained by dividing a flow path length of the second flow path by the square of a hydraulic equivalent diameter of the second flow path is defined as x2. 0.9≦x2 / x1≦1.1 With this configuration, a more efficient fuel cell can be obtained.

[0095] (Technology 6) The fuel cell according to any one of techniques 1 to 5, wherein the inlet of the refrigerant flow path and the outlet of the refrigerant flow path are located on a center line that passes through the center of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member and extends in the direction of flow of the refrigerant, and the first flow path and the second flow path are disposed symmetrically with respect to the center line. With this configuration, a more efficient fuel cell can be obtained.

[0096] (Technology 7) The fuel cell according to technique 6, wherein the first flow path has a first sub-flow path and a second sub-flow path that are independent of each other, the second flow path has a first sub-flow path and a second sub-flow path that are independent of each other, and the first flow path is disposed between the first sub-flow path of the second flow path and the second sub-flow path of the second flow path. This configuration makes it easy to dispose the first flow path and the second flow path symmetrically with respect to the center line.

[0097] (Technology 8) 8. The fuel cell according to any one of claims 1 to 7, wherein the region A is a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member, which occupies 50% of the area from the inlet side of the refrigerant flow channel, and the region B is a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member, which occupies 50% of the area from the outlet side of the refrigerant flow channel. This configuration promotes condensation of water vapor downstream of the refrigerant flow channel, thereby improving the moisture content.

[0098] (Technology 9) The fuel cell according to any one of techniques 1 to 8, wherein the region A is a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member, which occupies 25% of the area from the inlet side of the refrigerant flow channel, and the region B is a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member, which occupies 75% of the area from the outlet side of the refrigerant flow channel. With this configuration, condensation of water vapor is further promoted downstream of the refrigerant flow channel, thereby further improving the moisture content.

[0099] (Technology 10) The fuel cell according to any one of techniques 2 to 8, wherein, of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member, a region having 25% of the area from the inlet side of the refrigerant channel is defined as Region C, and a region having 75% of the area from the outlet side of the refrigerant channel is defined as Region D, the branch position is provided in Region D. With this configuration, a more efficient fuel cell can be obtained.

[0100] (Technology 11) 11. The fuel cell according to any one of techniques 1 to 10, wherein the coolant flow path includes a serpentine flow path. With this configuration, it is easy to cool the entire electrode surface. [Industrial Applicability]

[0101] The technology of the present disclosure is useful for electrochemical devices such as secondary batteries, fuel cells, and hydrogen purification devices. [Explanation of symbols]

[0102] 10 Membrane electrode assembly 101 Electrode area 12 Electrolyte membrane 13 Anode 14 Anode catalyst layer 15 Anode gas diffusion layer 16 cathode 17 Cathode catalyst layer 18 Cathode gas diffusion layer 19 Frame 20 Anode separator 21 Page 1 22 Side 2 30 Cathode separator 31 Page 1 32 2nd page 40 fuel gas flow path 401 Part 1 402 Part 2 40a Fuel gas inlet 40b Fuel gas outlet 43 Fuel gas inlet 44 Fuel gas exhaust passage 50 oxidant gas flow path 501 Part 1 502 Part 2 50a Oxidant gas inlet 50b Oxidant gas outlet 53 Oxidant gas inlet 54 Oxidant gas exhaust channel 60 refrigerant flow path 601 Part 1 602 Part 2 60a Refrigerant inlet 60b Refrigerant outlet 61 First Channel 61a 1st subchannel 61b 2nd sub-channel 62 Second Channel 62a 1st subchannel 62b 2nd sub-channel 611, 621 Part 1 612, 622 2nd part 63 Refrigerant introduction path 64 Refrigerant discharge path 71 First area 72 Second area 81, 83 Junction 82, 84 merging position CL center line A, B, C, D area 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; a fuel gas flow channel provided between the anode and the anode separator; an oxidant gas flow channel provided between the cathode and the cathode separator; a refrigerant flow path provided in at least one selected from the group consisting of the anode separator, the cathode separator, and a separate member disposed between the anode separator and the cathode separator; Equipped with the refrigerant flow path includes a first flow path and a second flow path that are independent of each other; When a region of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member that is located on the inlet side of the refrigerant flow path is defined as Region A, and a region of a surface of the separate member that is located on the outlet side of the refrigerant flow path is defined as Region B, In the region A, the ratio of the area occupied by the first flow path is smaller than the ratio of the area occupied by the second flow path, In the region B, the proportion of the area occupied by the first flow path is greater than the proportion of the area occupied by the second flow path. fuel cell.

2. the refrigerant flow path branches into the first flow path and the second flow path at a branching position downstream of an inlet of the refrigerant flow path, The first flow path and the second flow path join at a joining position upstream of an outlet of the refrigerant flow path. The fuel cell according to claim 1 .

3. 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 1 .

4. a flow direction of the coolant in the coolant flow channel is parallel to a flow direction of the oxidant gas in the oxidant gas flow channel; The fuel cell according to claim 1 .

5. When a value obtained by dividing the flow path length of the first flow path by the square of the hydraulic equivalent diameter of the first flow path is defined as x1, and a value obtained by dividing the flow path length of the second flow path by the square of the hydraulic equivalent diameter of the second flow path is defined as x2, the following formula is satisfied: 0.9≦x2 / x1≦1.1 The fuel cell according to claim 1 .

6. an inlet of the refrigerant flow channel and an outlet of the refrigerant flow channel are located on a center line that passes through a center of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member, and that extends in a flow direction of the refrigerant, The first flow path and the second flow path are arranged symmetrically with respect to the center line. The fuel cell according to claim 1 .

7. the first flow path has a first sub-flow path and a second sub-flow path that are flow paths independent of each other, the second flow path has a first sub-flow path and a second sub-flow path that are independent of each other, The first flow path is disposed between the first sub-flow path of the second flow path and the second sub-flow path of the second flow path. The fuel cell according to claim 6.

8. the region A is a region having an area of ​​50% from an inlet side of the refrigerant flow channel of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member, the region B is a region having an area of ​​50% from the outlet side of the refrigerant flow channel of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member; The fuel cell according to claim 1 .

9. the region A is a region having an area of ​​25% from an inlet side of the refrigerant flow channel of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member, the region B is a region having an area of ​​75% from the outlet side of the refrigerant flow channel of a surface of the anode separator facing the cathode separator, a surface of the cathode separator facing the anode separator, or a surface of the separate member; The fuel cell according to claim 1 .

10. When a region of the surface of the anode separator facing the cathode separator, the surface of the cathode separator facing the anode separator, or the surface of the separate member having 25% of the area from the inlet side of the refrigerant flow channel is defined as Region C, and a region of the surface of the separate member having 75% of the area from the outlet side of the refrigerant flow channel is defined as Region D, The branch position is provided in the region D.

3. The fuel cell according to claim 2.

11. The refrigerant flow path includes a serpentine flow path. The fuel cell according to claim 1 .

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