Fuel cell stack

Abstract

We provide fuel cell stacks. [Solution] Each of the multiple fuel cell cells comprises a resin frame having an opening, a membrane electrode assembly disposed in the opening, and first and second separators facing each other via the frame and membrane electrode assembly. The fuel cell stack has a first manifold hole extending in the stacking direction. The frame has an inner edge that defines the first manifold hole. The first separator has an inner edge that defines the first manifold hole, a flat portion disposed along the inner edge of the first separator, an uneven portion that forms a plurality of gas passages extending from the flat portion toward the membrane electrode assembly, and a boundary line between the flat portion and the uneven portion. When a specific line is defined by moving the boundary line toward the inner edge of the first separator by the height dimension of the plurality of gas passages, the inner edge of the frame is located on the side further away from the first manifold hole than the specific line in a direction parallel to the surface of the frame.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a fuel cell stack.

[0002] Patent Document 1 discloses a fuel cell stack. This fuel cell stack has a structure in which a membrane electrode assembly is surrounded by a resin frame. Also, it has a structure in which the membrane electrode assembly together with the frame is sandwiched between both separators of the cathode and anode. By laminating the manifold holes of the frame and the manifold holes of both separators, a manifold hole extending along the stacking direction is formed. A plurality of gas passages extending toward the membrane electrode assembly are arranged on the inner peripheral surface of the manifold hole.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] There may be a case where water droplets remaining on the inner peripheral surface of the manifold hole spread wetly so as to cover all of the plurality of gas passages. If the wetly spreading water droplets freeze and all of the gas passages are blocked, it may be impossible to supply or exhaust the reaction gas to the membrane electrode assembly at startup, and power generation may not be possible.

Means for Solving the Problems

[0005] The fuel cell stack disclosed herein is a fuel cell stack comprising a plurality of fuel cell cells stacked on top of each other. Each of the plurality of fuel cell cells comprises a resin frame having an opening, a membrane electrode assembly disposed in the opening, and a first separator and a second separator facing each other via the frame and the membrane electrode assembly. The fuel cell stack has a first manifold hole formed along the stacking direction. The frame has an inner edge that defines the first manifold hole. The first separator has a first separator inner edge that defines the first manifold hole, a flat portion disposed along the first separator inner edge and disposed on the opposing surface facing the second separator, an uneven portion that forms a plurality of gas passages extending from the flat portion toward the membrane electrode assembly, and a boundary line between the flat portion and the uneven portion, which is disposed along the first separator inner edge and on the outside of the first separator inner edge. When a specific line is defined by shifting the boundary line by the height dimension of multiple gas passages toward the inner edge of the first separator, the inner edge of the frame is located on the side of the specific line that is further away from the first manifold hole in a direction parallel to the surface of the frame.

[0006] When the inner edge of the frame protrudes toward the first manifold hole beyond the boundary line between the flat and uneven portions of the first separator, the flat portion and the frame are arranged in a structure facing each other in the stacking direction. A groove is formed between the frame and the flat portion, extending along the inner edge of the frame. The inventors have found that when the amount of protrusion of the inner edge of the frame from the boundary line is equal to or greater than the height dimension of the gas passage in the stacking direction, water droplets tend to spread easily along the groove. This is because water droplets move mainly according to capillary pressure. When the amount of protrusion of the inner edge of the frame from the boundary line is equal to or greater than the height dimension of the gas passage, the height of the side wall of the groove formed by the frame reaches a height sufficient to exert capillary pressure. When capillary pressure is exerted in the groove, the ease with which water droplets spread becomes the same in the groove and in the gas passage. As a result, there is a risk that all of the multiple gas passages may be blocked by water droplets as they spread along the groove.

[0007] Therefore, in the above structure, the inner edge of the frame is located on the side further away from the first manifold hole than the specific line. Consequently, the amount of protrusion of the inner edge of the frame from the boundary line is smaller than the height dimension of the gas passage. As a result, even when a groove is formed between the frame and the flat part, capillary pressure cannot be sufficiently exerted in the groove. Consequently, water droplets can spread more easily through the gas passage than through the groove. Because water droplets can be preferentially moved to the gas passage, it is possible to suppress the spreading of water droplets along the groove. This prevents a situation in which all of the multiple gas passages become blocked by water droplets. [Brief explanation of the drawing]

[0008] [Figure 1] This is an exploded view of fuel cell cell 1. [Figure 2] This is an enlarged top view of the first manifold hole M1o. [Figure 3] This is a partial side view of the inner circumferential surface of the first manifold hole M1o. [Figure 4] This is a partial cross-sectional view along line IV-IV in Figure 2. [Figure 5] This is a partial cross-sectional view of the comparative fuel cell cell 101. [Figure 6] This is a partial cross-sectional view of the vicinity of the first manifold hole M1o in Example 2. [Figure 7] This is a partial cross-sectional view of the vicinity of the first manifold hole M1o in Example 3. [Modes for carrying out the invention]

[0009] In a direction parallel to the surface of the frame, the inner edge of the frame may be located on the side away from the first manifold hole than the boundary line.

[0010] With the above configuration, the inner edge of the frame does not protrude beyond the boundary line, so no groove is formed between the frame and the flat part. Therefore, it is possible to prevent water droplets from wetting and spreading along the groove.

[0011] The second separator may have an inner edge that defines the first manifold hole. In a direction parallel to the surface of the second separator, the inner edge of the second separator may be located on the side away from the first manifold hole than the boundary line.

[0012] With the above configuration, the second separator does not face the flat portion of the first separator in the stacking direction. Therefore, no groove is formed between the second separator and the flat portion. Consequently, it is possible to prevent water droplets from wetting and spreading along the groove.

[0013] The first manifold hole may also be a discharge hole for discharging the reactive gas introduced into the membrane electrode assembly.

[0014] The amount of water droplets is greater at the reactive gas outlet than at the reactive gas inlet. This is because the water droplets from the reaction are included. With the above configuration, the amount of residual water droplets can be reduced at the outlet where a large amount of water droplets are generated. This makes it possible to more effectively suppress the situation in which the gas passage is blocked due to the freezing of water droplets.

[0015] The water contact angles of the first and second separators may be smaller than the water contact angles of the frame.

[0016] According to the above configuration, the inner wall surfaces of the first and second separators can be made more hydrophilic than the inner wall surface of the frame. [Examples]

[0017] (Outline configuration of fuel cell cell 1) Figure 1 is an explanatory diagram showing an exploded view of a fuel cell cell 1 in one embodiment of the present invention. The fuel cell cell 1 is a solid polymer fuel cell that generates electricity by receiving hydrogen and oxygen. The fuel cell cell 1 mainly comprises a first separator 10, a second separator 20, a frame 30, and a membrane electrode assembly 40.

[0018] The frame body 30 is a frame-shaped resin member that surrounds the entire periphery of the membrane electrode assembly 40. In this embodiment, for example, polyethylene naphthalate (PEN) is used as the resin member. However, as the resin member, various other resin members such as polypropylene, polyethylene, polyethylene terephthalate, polyphenylene sulfide, and rubber materials can also be used.

[0019] The frame body 30 has an opening 35 in its central region for surrounding and housing the membrane electrode assembly 40. The membrane electrode assembly 40 is disposed in the opening 35. In FIG. 1, the membrane electrode assembly 40 is shown as a gray filling. Also, the structure of the membrane electrode assembly 40 will be described later. Further, the frame body 30 has manifold holes 61i, 61o, 62i, 62o, 63 on the left and right sides (±x direction sides) of the opening 35.

[0020] The first separator 10 and the second separator 20 face each other through the frame body 30 and the membrane electrode assembly 40. The first separator 10 and the second separator 20 have conductivity. The first separator 10 and the second separator 20 may be formed, for example, by press-molding a metal plate made of stainless steel, titanium, or an alloy thereof, or may be formed of a carbon resin composite material or the like. In this embodiment, the first separator 10 and the second separator 20 are formed of a carbon resin composite material.

[0021] In this embodiment, the first separator 10 is the cathode-side separator, and the second separator 20 is the anode-side separator. The first separator 10 has manifold holes 11i, 11o, 12i,​​​The stacking of manifold holes 11i, 61i, and 21i forms a first manifold hole M1i used for supplying reaction gas (air). The stacking of manifold holes 11o, 61o, and 21o forms a first manifold hole M1o used for discharging reaction gas (air). The stacking of manifold holes 12i, 62i, and 22i forms a second manifold hole M2i used for supplying reaction gas (hydrogen). The stacking of manifold holes 12o, 62o, and 22o forms a second manifold hole M2o used for discharging reaction gas (hydrogen). The stacking of manifold holes 13, 63, and 23 forms a cooling water manifold hole Mw that forms a cooling water channel. The specific configuration of the cooling water channel is not directly related to the gist of the technology described herein, so a detailed explanation is omitted. The first manifold holes M1i and M1o, the second manifold holes M2i and M2o, and the cooling water manifold hole Mw extend along the stacking direction (z-direction).

[0023] The first separator 10 is provided with a flow path 15 that extends from the first manifold hole M1i to M1o. This flow path 15 is formed by the uneven surface 10p on the lower surface of the first separator 10 (i.e., the surface facing the frame 30). The details of the uneven surface 10p will be described later. The reaction gas (air) that flows into the first manifold hole M1i passes through the membrane electrode assembly 40 via the flow path 15 and is discharged from the first manifold hole M1o (see Figure 1, arrow Y1).

[0024] Similarly, the second separator 20 is provided with a flow path 25 leading from the second manifold hole M2i to M2o. This flow path 25 is formed by the uneven surface 20p on the upper surface of the second separator 20 (i.e., the surface facing the frame 30). The reaction gas (hydrogen) flowing into the second manifold hole M2i passes through the membrane electrode assembly 40 via the flow path 25 and is discharged from the second manifold hole M2o (see Figure 1, arrow Y2).

[0025] Furthermore, gaskets 51, 52, and 53 are positioned on the upper surface of the first separator 10. The gaskets 51, 52, and 53 are made of, for example, silicone rubber. Gasket 51 is positioned to surround each of the manifold holes 11i and 11o. When multiple fuel cell cells 1 are stacked, the gasket 51 ensures the sealing of the first manifold holes M1i and M1o. Similarly, gasket 52 is positioned to surround each of the manifold holes 12i and 12o. When multiple fuel cell cells 1 are stacked, the gasket 52 ensures the sealing of the second manifold holes M2i and M2o. Gasket 53 is positioned to surround the outer circumference of the first separator 10.

[0026] (Structure of the first manifold hole M1o) Figure 2 shows an enlarged top view of the first manifold hole M1o in the fuel cell cell 1. The first manifold hole M1o is an air exhaust manifold hole located in the lower left of the fuel cell cell 1 in Figure 1. Figure 3 shows a partial side view of the inner surface of the first manifold hole M1o as seen from the direction of arrow Y11 in Figure 2. Although Figure 3 is a side view, hatching is used to make the opening 15a easier to see.

[0027] The flow path 15 comprises a plurality of first gas passages 15g. As shown in Figure 3, the plurality of first gas passages 15g are formed between the frame 30 and the first separator 10. That is, on the lower surface 10b of the first separator 10, uneven surfaces 10p are arranged in the y direction. The lower surfaces of the uneven surfaces 10p are in contact with the upper surface of the frame 30, thereby forming the first gas passages 15g between adjacent uneven surfaces 10p. Therefore, in the first gas passages 15g, the side walls are formed by the uneven surfaces 10p, the upper inner wall is formed by the lower surface 10b of the first separator 10, and the lower inner wall is formed by the upper surface 30u of the frame 30. The first gas passages 15g have a gas passage height Dc in the z direction. The gas passage height Dc is the distance between the lower surface 10b of the first separator 10 and the upper surface 30u of the frame 30.

[0028] As shown in Figure 2, the multiple first gas passages 15g extend from the first manifold hole M1o to the membrane electrode assembly 40. The terminal openings of the multiple first gas passages 15g are located within the first region R1 on the inner circumferential surface of the first manifold hole M1o. Therefore, as shown in Figure 3, within the first region R1, the openings 15a of the first gas passages 15g are exposed on the inner circumferential surface of the first manifold hole M1o.

[0029] Figure 4 shows a partial cross-sectional view along the line IV-IV in Figure 2. Figure 4 is a cross-sectional view passing through the central axis C1 of the first manifold hole M1o and the first gas passage 15g. Figure 4 shows a fuel cell stack in which two fuel cell cells 1 are stacked. In actual fuel cell stacks, three or more fuel cell cells 1 are stacked. The membrane electrode assembly 40 comprises an oxygen electrode 41, a hydrogen electrode 42, and an electrolyte membrane 43. The electrolyte membrane 43 is a proton-conducting ion exchange membrane formed from a solid polymer material. The oxygen electrode 41 comprises a first catalyst layer 44 and a first gas diffusion layer 45. The hydrogen electrode 42 comprises a second catalyst layer 46 and a second gas diffusion layer 47. The first catalyst layer 44 and the second catalyst layer 46 are porous layers in which carbon particles or metal oxides supporting a catalyst are linked together with resin. The first gas diffusion layer 45 and the second gas diffusion layer 47 are conductive members that have water permeability and gas permeability. Since a well-known structure can be applied to the membrane electrode assembly 40, a detailed explanation will be omitted.

[0030] A flange-shaped outer peripheral region PA is formed on the outer periphery of the membrane electrode assembly 40 by the oxygen electrode 41. Within the outer peripheral region PA, an adhesive layer 49 is placed on the lower surface 41b of the oxygen electrode 41. The adhesive layer 49 is a layer formed of adhesive. Examples of adhesives include UV-curable adhesives and hot melt adhesives. The lower surface 41b of the oxygen electrode 41 is fixed to the upper surface 30u of the frame 30 by the adhesive layer 49.

[0031] The frame 30 has a three-layer structure in which a first resin layer 31, a core layer 33, and a second resin layer 32 are laminated in the thickness direction. The core layer 33 is a structural member that has gas sealing and insulating properties. The first resin layer 31 is a layer that adheres to the first separator 10. The second resin layer 32 is a layer that adheres to the second separator 20.

[0032] The first resin layer 31 and the second resin layer 32 may have a lower melting point than the core layer 33. Specifically, the first resin layer 31 and the second resin layer 32 may be thermoplastic resins such as acid-modified olefins and polyesters. The multilayer frame 30 can be formed by various methods. For example, it may be formed by co-extrusion molding.

[0033] The frame 30 is provided with an inner frame edge 30w. The inner frame edge 30w is a part of the inner wall of the first manifold hole M1o and defines the first manifold hole M1o.

[0034] The first separator 10 comprises a first separator inner edge 10w, an uneven portion 10p, a flat portion 10f, and a boundary line BL. The first separator inner edge 10w is a part that constitutes a portion of the inner wall of the first manifold hole M1o and defines the first manifold hole M1o. The uneven portion 10p is a portion that protrudes downward from the lower surface 10b of the first separator 10. In the cross-sectional view of Figure 4, for clarity, the uneven portion 10p that exists in the depth direction of the paper is shown as a solid gray color. Also, as shown in Figure 2, a plurality of first gas passages 15g extending from the flat portion 10f toward the membrane electrode assembly 40 are formed by the uneven portion 10p.

[0035] The flat portion 10f is a region near the inner edge 10w of the first separator, where the uneven portion 10p is not located. The flat portion 10f is also located on the opposing surface (i.e., the lower surface 10b) facing the second separator 20. As shown in Figure 2, the flat portion 10f is located along the inner edge 10w of the first separator. The flat portion 10f is also a necessary part for punching out the manifold hole 11o. Since the cut surface is composed of the flat portion 10f, it is possible to improve the accuracy and machinability of the cut surface.

[0036] A boundary line BL is formed between the flat portion 10f and the uneven portion 10p. As shown in Figure 2, the boundary line BL is positioned along the inner edge 10w of the first separator and outside the inner edge 10w of the first separator. A first gas passage 15g is formed on the side of the boundary line BL that is away from the first manifold hole M1o (+x direction side). On the other hand, a groove region CR is formed on the side of the boundary line BL that is closer to the first manifold hole M1o (-x direction side).

[0037] As shown in Figure 4, the groove region CR is a region formed between the flat portion 10f and the surface facing the flat portion 10f (i.e., the upper surface 30u of the frame 30). The groove region CR has a groove region height Dm in the z direction. The groove region height Dm is equivalent to the gas passage height Dc.

[0038] As shown in Figure 2, the groove region CR is arranged along the inner edge 10w of the first separator. In other words, the groove region CR functions as a region that commonly connects multiple first gas passages 15g along the inner edge 10w of the first separator.

[0039] Here, as shown in Figure 4, a specific line SL is defined. The specific line SL is a line obtained by shifting the boundary line BL parallel to the inner edge 10w of the first separator (-x direction) by the gas passage height Dc. The inner edge 30w of the frame is located on the side further away from the first manifold hole M1o (+x direction) than the specific line SL (see arrow Y21).

[0040] The second separator 20 has a second separator inner edge 20w. The second separator inner edge 20w is a part of the inner wall of the first manifold hole M1o and defines the first manifold hole M1o. The second separator inner edge 20w is located on the side (+x direction side) away from the first manifold hole M1o than the boundary line BL.

[0041] The water contact angles of the first separator 10 and the second separator 20 are smaller than the water contact angles of the frame 30. For example, the water contact angles of the first separator 10 and the second separator 20 may be less than 90°, and the water contact angle of the frame 30 may be greater than 90°. That is, the inner edges 10w of the first separator and 20w of the second separator are more hydrophilic than the inner edge 30w of the frame. This is because the frame 30 has water-repellent properties due to the inherent properties of the resin material described above. Also, the first separator 10 and the second separator 20 have hydrophilic properties due to the inherent properties of the conductive material described above. Note that the hydrophilicity referred to here is the hydrophilicity under the power generation environment of a fuel cell (an environment where water droplets are present in a high-temperature, high-humidity state).

[0042] (assignment) The problem will be explained using the comparative fuel cell cell 101 shown in Figure 5. The comparative fuel cell cell 101 (Figure 5) has a different positional relationship to the inner edge 30w of the frame compared to the fuel cell cell 1 (Figure 4) of this embodiment. Specifically, the inner edge 30w of the frame is located closer to the first manifold hole M1o than the specific line SL (-x direction side) (see arrow Y20). That is, in the comparative example, the amount of protrusion PR0 of the inner edge 30w of the frame from the boundary line BL is greater than or equal to the gas passage height Dc. The other structures of the comparative fuel cell cell 101 are the same as those of the fuel cell cell 1 of this embodiment, so their explanation will be omitted.

[0043] In the comparative fuel cell cell 101, a groove region CR is formed between the upper surface 30u of the frame 30 and the flat portion 10f of the first separator 10. As shown in Figure 2, the groove region CR connects multiple first gas passages 15g in common along the inner edge 10w of the first separator. In this case, water droplets remaining on the inner surface of the first manifold hole M1o may spread and wet along the groove region CR. If the water droplets spread throughout the entire first region R1, all of the multiple first gas passages 15g will be covered with water droplets. If the water droplets freeze in this state, all of the first gas passages 15g will be blocked. As a result, it may not be possible to draw in or exhaust reaction gas to the membrane electrode assembly during startup, and power generation may not be possible.

[0044] (Solution and effect) The inventors have found that when the amount of protrusion of the inner edge 30w of the frame from the boundary line BL is equal to or greater than the gas passage height Dc of the first gas passage 15g, water droplets tend to spread easily along the groove region CR. This is because water droplets move mainly according to capillary pressure. Furthermore, when the amount of protrusion of the inner edge 30w of the frame from the boundary line BL is equal to or greater than the gas passage height Dc, the height in the x-direction of the side wall of the groove region CR formed by the upper surface 30u of the inner edge 30w of the frame reaches a height sufficient to exert capillary pressure. When sufficient capillary pressure is exerted in the groove region CR, the ease with which water droplets spread becomes the same in the groove region CR and the first gas passage 15g. As a result, there is a risk that all of the multiple first gas passages 15g may be blocked by water droplets as they spread along the groove region CR.

[0045] Therefore, in the technology of this embodiment, the inner edge 30w of the frame is located on the +x side of the specific line SL (see Figure 4). In other words, in this embodiment, the amount of protrusion PR1 of the inner edge 30w of the frame from the boundary line BL is smaller than the gas passage height Dc. Consequently, the height of the side wall of the groove region CR in the x direction does not reach a height sufficient to exert capillary pressure. As a result, water droplets can be wetted and spread more easily in the first gas passage 15g than in the groove region CR. Since water droplets can be preferentially moved to the first gas passage 15g, it is possible to suppress the wetting and spreading of water droplets along the groove region CR. It is possible to prevent a situation in which all of the multiple first gas passages 15g are blocked by water droplets.

[0046] In this embodiment, the fuel cell cell 1 (Figure 4) has a structure in which the inner edge 10w of the first separator protrudes toward the central axis C1 more than the inner edge 30w of the frame. This allows a relatively hydrophilic material to be exposed on the inner surface of the first manifold hole M1o in the first region R1 (the region where the opening 15a of the first gas passage 15g is located). Due to this hydrophilicity, water droplets adhering to the inner surface of the first manifold hole M1o in the first region R1 can be made to connect with each other. As the volume of the water droplets increases, they can be easily discharged by gravity and gas flow. Since the amount of water droplets remaining on the inner surface of the first manifold hole M1o can be reduced, it is possible to suppress the blockage of the first gas passage 15g due to the freezing of water droplets. This makes it possible to improve the starting performance of the fuel cell cell 1 at sub-zero temperatures.

[0047] The amount of water droplets is greater at the first manifold hole M1o, which is the discharge hole for reactive gas, compared to the first manifold hole M1i, which is the introduction hole for reactive gas. This is because it contains water droplets after the reaction. In the fuel cell cell 1 of this embodiment, a hydrophilic member (first separator inner edge 10w) is made to protrude from the inner circumferential surface of the first manifold hole M1o on the discharge side. This has the effect of reducing the amount of residual water droplets at the inner circumferential surface of the first manifold hole M1o on the discharge side, where a large amount of water droplets are generated, and thus it is possible to suppress the blockage of the first gas passage 15g.

[0048] (Modified version of Example 1) The structure of the discharge-side first manifold port M1o described above is also applicable to the introduction-side first manifold port M1i. That is, it may have a structure in which the inner edge 30w of the frame is located further away from the first manifold port M1i than the specific line SL. Similarly, the structures of the air-side first manifold ports M1o and M1i are also applicable to the hydrogen-side second manifold ports M2o and M2i.

[0049] The structure in which the inner edge 30w of the frame is located on the side further away from the first manifold hole M1o than the specific line SL does not need to be formed around the entire circumference of the inner surface of the first manifold hole M1o, but only needs to be formed in at least the first region R1 (Figure 2). The regions other than the first region R1 are regions far from the first gas passage 15g. This is because even if water droplets wet and spread in these distant regions, there is little risk of blocking the first gas passage 15g.

[0050] The structure in which the inner edge 30w of the frame is located further away from the first manifold hole M1o than the specific line SL does not need to be formed in the entire area of ​​the first region R1 (Figure 2), but only in at least a portion of it. This prevents the first gas passage 15g from being completely blocked by the freezing of water droplets. With at least a portion of the first gas passage 15g open, it becomes possible to start the fuel cell cell 1. [Examples]

[0051] In Example 2 (Figure 6), the positional relationship of the inner edge 30w of the frame is different from that of Example 1 (Figure 4). Specifically, the inner edge 30w of the frame is located on the side away from the first manifold hole M1o (+x direction side) from the boundary line BL (see arrow Y31). The other structures of Example 2 are the same as those of Example 1. The parts common to Example 1 and Example 2 will not be explained.

[0052] The inner edge 20w of the second separator is located on the side (+x direction side) away from the first manifold hole M1o than the boundary line BL (see arrow Y32). In other words, in the fuel cell cell 1 of Embodiment 2, the inner edge 30w of the frame and the inner edge 20w of the second separator are positioned further back (+x direction side) than the flat portion 10f of the first separator 10. Therefore, the surface facing the flat portion 10f is the first separator 10 of the adjacent fuel cell cell 1. As a result, the groove region height Dm of the groove region CR is equivalent to the cell pitch between the fuel cell cells 1. In other words, the groove region height Dm can be maximized.

[0053] (effect) In the technique of Example 2, the capillary pressure generated in the groove region CR can be minimized by maximizing the groove region height Dm. This is because capillary pressure generally decreases as the width of the groove (i.e., the groove region height Dm) increases. As a result, water droplets can be wetted more easily in the first gas passage 15g than in the groove region CR. Since water droplets can be preferentially moved to the first gas passage 15g, it is possible to suppress the water droplets from wetting along the groove region CR. [Examples]

[0054] The fuel cell cell 301 of Example 3 (Figure 7) differs from the fuel cell cell 1 of Example 1 (Figure 4) in how the single cell is divided. Specifically, the second separator 20 is exposed on the upper surface on the +z direction side of the fuel cell cell 301, and the membrane electrode assembly 40 is exposed on the lower surface on the -z direction side. Parts common to Example 1 (Figure 4) and Example 3 (Figure 7) are given the same reference numerals, and their explanation is omitted.

[0055] The first gas passage 15g of the fuel cell cell 301 is formed between the opposing first separator 10 and second separator 20. The first gas passage 15g has a gas passage height Dc in the z direction. The first gas passage 15g communicates with the membrane electrode assembly 40 via a communication hole 10h. Gas discharged from the oxygen electrode 41 is exhausted into the first gas passage 15g through the communication hole 10h (see dotted arrow YG).

[0056] The inner edge 30w of the frame is located on the side (+x direction) away from the first manifold hole M1o than the boundary line BL (see arrow Y41). Similarly, the inner edge 20w of the second separator is located on the side (+x direction) away from the first manifold hole M1o than the boundary line BL (see arrow Y42). Therefore, the surface facing the flat portion 10f is the first separator 10 of the adjacent fuel cell cell 301. As a result, the groove region height Dm of the groove region CR is equivalent to the cell pitch between the fuel cell cells 301. By maximizing the groove region height Dm, the capillary pressure generated in the groove region CR can be minimized. This makes it possible to suppress water droplets from wetting and spreading along the groove region CR.

[0057] Although embodiments have been described in detail above, these are merely illustrative and do not limit the scope of the claims. The technologies described in the claims include various modifications and changes to the specific examples illustrated above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technologies illustrated in this specification or drawings achieve multiple objectives simultaneously, and achieving even one of these objectives constitutes technical usefulness in itself.

[0058] (modified version) The technology described herein is applicable to both air-cooled and water-cooled fuel cells.

[0059] In this embodiment, the shapes of the first manifold holes M1i and M1o, the second manifold holes M2i and M2o, and the cooling water manifold hole Mw are rectangular in the figure, but the manifold holes may also be triangular, polygonal, or have irregularly shaped openings. [Explanation of symbols]

[0060] 1: Fuel cell cell 10: First separator 10w: Inner edge of first separator 10f: Flat section 10p: Uneven section 15g: First gas passage 20: Second separator 30: Frame 30w: Inner edge of frame 40: Membrane electrode assembly C1: Central axis M1i and M1o: First manifold hole BL: Boundary line SL: Specific line

Claims

1. A fuel cell stack in which multiple fuel cell cells are stacked, Each of the plurality of fuel cell cells is A resin frame with an opening, A membrane electrode assembly disposed in the aforementioned opening, A first separator and a second separator facing each other via the frame and the membrane electrode assembly, It is equipped with, The fuel cell stack has a first manifold hole that extends along the stacking direction. The frame has an inner edge that defines the first manifold hole, The first separator is, The inner edge of the first separator defining the first manifold hole, A flat portion arranged along the inner edge of the first separator, the flat portion arranged on the opposing surface facing the second separator, The flat portion extends toward the film electrode assembly and forms a plurality of uneven portions which form a plurality of gas passages, The boundary line between the flat portion and the uneven portion, the boundary line being located along the inner edge of the first separator and on the outside of the inner edge of the first separator, It has, When a specific line is defined by moving the boundary line toward the inner edge of the first separator by the height dimension of the plurality of gas passages, the inner edge of the frame is located on the side of the specific line that is further away from the first manifold hole in a direction parallel to the surface of the frame. Fuel cell stack.

2. The fuel cell stack according to claim 1, wherein, in a direction parallel to the surface of the frame, the inner edge of the frame is located on the side further away from the first manifold hole than the boundary line.

3. The second separator has an inner edge that defines the first manifold hole, The fuel cell stack according to claim 1, wherein, in a direction parallel to the surface of the second separator, the inner edge of the second separator is located on the side further away from the first manifold hole than the boundary line.

4. The fuel cell stack according to claim 1, wherein the first manifold hole is an exhaust hole for discharging the reactive gas introduced into the membrane electrode assembly.

5. The fuel cell stack according to any one of claims 1 to 4, wherein the water contact angles of the first separator and the second separator are smaller than the water contact angle of the frame.

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