Fuel cell

Abstract

To provide a fuel cell with excellent volumetric efficiency. 【Solution means】The fuel cell 1 includes a fuel cell stack 10 in which a plurality of cells 11 are stacked in the stacking direction, and a case 20 having an accommodation space S in which the fuel cell stack 10 is accommodated. The case 20 has a bottom wall 21 and an opposing side wall 22 having a first gradient θ1 rising from the peripheral edge of the bottom wall 21. The accommodation space S is defined by the bottom wall 21 and the opposing side wall 22. When viewed from the stacking direction, the side edge 18 of the cell 11 has a second gradient θ2 corresponding to the first gradient θ1 of the opposing side wall 22.

Description

Technical Field

[0001] The present disclosure relates to a fuel cell.

Background Art

[0002] A fuel cell is formed by housing a battery stack in which battery cells are stacked in a case. Patent Document 1 discloses a fuel cell including a cell stack and a case that surrounds at least the side surfaces of the cell stack.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] The case of a fuel cell is produced, for example, by casting. In the case of casting, a draft is required to remove the molded body from the mold. However, if the fuel cell case has a draft, a gap may occur between the battery stack formed by stacking rectangular cells and the case, resulting in a decrease in volumetric efficiency. Patent Document 1 proposes a method of reducing the gap between the cell and the case by joining two cases having a draft, but there is a problem from the viewpoint of manufacturing efficiency because a step of joining the cases is required.

[0005] An object of the present disclosure is to provide a fuel cell having excellent volumetric efficiency.

Means for Solving the Problems

[0006] A fuel cell according to an embodiment of the present disclosure includes a fuel cell stack in which a plurality of cells are stacked in a stacking direction, and a case having an accommodation space in which the fuel cell stack is accommodated, The case has a bottom wall and opposing side walls rising from the peripheral edge of the bottom wall and having a first gradient. The accommodation space is defined by the bottom wall and the opposing side walls. When viewed in the stacking direction, the side edge of the cell has a second gradient corresponding to the first gradient of the opposing side wall.

Advantages of the Invention

[0007] According to the present disclosure, a fuel cell with excellent volumetric efficiency can be provided.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Modes for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the drawings, U represents the upward direction, D represents the downward direction, R represents the right direction, L represents the left direction, F represents the front direction, and B represents the rear direction.

[0010] FIG. 1 is a schematic diagram showing a fuel cell 1 according to an embodiment of the present disclosure. As shown in FIG. 1, the fuel cell 1 includes a fuel cell stack 10 and a case 20. In FIG. 1, the fuel cell stack 10 is represented by a dashed line, and the case 20 is represented by a solid line. The fuel cell stack 10 is a laminate in which a plurality of cells 11 (see FIG. 2) are stacked in the stacking direction. The stacking direction is the direction along the front direction or the rear direction in FIG. 1.

[0011] The case 20 includes an upper wall 21, opposing side walls 22, a front wall 23, a rear lid 24, and a lower lid 25. The upper wall 21 is an example of the bottom wall in the present disclosure. The case 20 has an accommodation space S (see FIG. 2) inside, and the fuel cell stack 10 is accommodated in the accommodation space S. The case 20 is made of, for example, aluminum. The fuel cell stack 10 accommodated in the case 20 is supported by a compressive force applied from end plates (not shown) disposed at both ends in the stacking direction.

[0012] FIG. 2 is a diagram showing the configuration of the cell 11 and the case 20 as viewed from the stacking direction of the cell 11. As shown in FIG. 2, the cell 11 includes a frame body 12, a membrane electrode assembly (MEA) 13 disposed at the center, and manifolds disposed on the left and right of the membrane electrode assembly 13 and extending in the stacking direction. The manifolds provided in each cell 11 ensure a flow path through which gas or refrigerant flows along the stacking direction. Specifically, as the manifolds of the cell 11, a hydrogen inlet 14a, a hydrogen outlet 14b, an air inlet 15a, an air outlet 15b, a cooling water inlet 16a, and a cooling water outlet 16b are provided. The membrane electrode assembly 13 is an assembly including a catalyst layer, an electrolyte membrane, and a gas diffusion layer. The fuel cell 1 generates power by supplying hydrogen through the hydrogen inlet 14a and oxygen through the air inlet 15a to the membrane electrode assembly 13 of each cell 11. In this specification, the region A1 where the membrane electrode assembly 13 is disposed in the cell 11 is referred to as a power generation region, and the region A2 where each manifold and other elements are disposed is referred to as a peripheral region. The cell 11 in the present embodiment includes, as elements other than the manifolds disposed in the peripheral region A2, a notch 171 and a hole 172 used for positioning during assembly, a plurality of dimples 173 for evenly distributing gas from the manifolds toward the power generation region A1, and a cell monitor terminal 174 for connecting a connector for voltage measurement. Each cell 11 arranged in the stacking direction is separated from an adjacent cell 11 by a separator (not shown).

[0013] FIG. 3 is a diagram showing an example of the assembly process of the fuel cell 1. The specific configuration of the case 20 will also be described with reference to FIG. 3. As shown in FIG. 3, the fuel cell 1 is formed by a process (1) of housing the fuel cell stack 10 in a molded body 201 with the lower surface and the rear surface open, a process (2) of closing the lower surface with a lower lid 25, and a process (3) of closing the rear surface with a rear lid 24 while compressing the fuel cell stack 10 in the stacking direction. For convenience of illustration, each member in FIG. 3 is drawn with the front and back reversed from the orientation shown in FIG. 1.

[0014] The molded body 201 is integrally molded by casting, and includes an upper wall 21, opposing side walls 22, and a front wall 23 among the parts constituting the case 20. The molded body 201 has a housing space S defined by the upper wall 21 and the opposing side walls 22. A hole 231 for guiding gas or refrigerant to the manifold is provided in the front wall 23. In the assembly process of the fuel cell 1, first, the fuel cell stack 10 is housed in the housing space S of the molded body 201 (step (1)), and the lower lid 25 is closed (step (2)). Next, while compressing the fuel cell stack 10 in the stacking direction toward the front wall 23 via an end plate (not shown), the rear lid 24 is closed and fixed (step (3)). Thereby, the fuel cell 1 in which the fuel cell stack 10 is housed in the housing space S within the case 20 is obtained. As described above, the case 20 is formed from the molded body 201, the lower lid 25, and the rear lid 24.

[0015] In a molded product by casting such as the molded body 201, a draft angle is generated for removing the molded product from the mold during molding. More specifically, the molded body 201 is cast by a lower mold that molds the inner surface facing the housing space S and an upper mold that molds the outer surface on the outside of the case 20. The draft angle is an angle for creating a gap between the mold and the molded body when removing the molded body from the upper mold and the lower mold after molding the molded body 201. As shown in FIG. 2, the case 20 has an upper wall 21 and a pair of left and right opposing side walls 22 rising from the peripheral edge of the upper wall 21, and the opposing side walls 22 have a draft angle θ1 with respect to the upper wall 21. The draft angle θ1 is an angle such that the opposing side walls 22 spread downward from the upper wall 21, and the angle is the angle formed by each of the left and right side walls of the opposing side walls 22 with respect to the normal direction of the upper wall 21. Since the opposing side walls 22 have the draft angle θ1, the outer shape of the housing space S defined by the upper wall 21 and the opposing side walls 22 is substantially trapezoidal. In this specification, the draft angle θ1 of the opposing side walls 22 of the case 20 is also referred to as the first draft angle θ1.

[0016] In the present embodiment, the outer shape of the cell 11 is substantially trapezoidal. As shown in FIG. 2, when viewed from the stacking direction, the side edge 18 of the cell 11 has a gradient θ2. In this specification, the gradient θ2 of the side edge 18 of the cell 11 is also referred to as the second gradient θ2. As shown in FIG. 2, the second gradient θ2 of the side edge 18 of the cell 11 corresponds to the first gradient θ1 of the opposing side wall 22, and typically the angles of the first gradient θ1 and the second gradient θ2 are equal. Note that the angle of the second gradient θ2 is the angle formed by the side edge 18 of the cell 11 with respect to the normal direction of the upper side of the cell 11 (the side facing the upper wall 21 of the case 20).

[0017] According to the fuel cell 1 of the present embodiment shown in FIG. 2, since the side edge 18 of the cell 11 has a second gradient θ2 corresponding to the first gradient θ1 of the opposing side wall 22 of the case 20, the gap between the cell 11 and the case 20 is small. Therefore, in the fuel cell 1, the ratio of the volume of the fuel cell stack 10 in the accommodation space S of the case 20 is large, and the volumetric efficiency is excellent.

[0018] As a comparative example for the present embodiment, the configuration of a conventional fuel cell will be described. FIG. 4 is a diagram showing the configuration of a conventional fuel cell 1A. The fuel cell 1A includes a cell 11A instead of the cell 11 of the fuel cell 1. FIG. 4 shows the cell 11A and the case 20 viewed from the stacking direction. The configuration of the case 20 of the fuel cell 1A is the same as that of the case 20 in the fuel cell 1. As shown in FIG. 4, the outer shape of the cell 11A of the fuel cell 1A is rectangular. That is, the side edge 18A of the cell 11A does not have a gradient. In this case, while the opposing side wall 22 of the case 20 has a first gradient, the side edge 18A of the cell 11A does not have a gradient, so an excess space S1 is generated between the cell 11A and the case 20 on the side of the cell 11A.

[0019] According to the fuel cell 1 of the present embodiment shown in FIG. 2 as described above, since the side edge 18 of the cell 11 has the second gradient θ2 corresponding to the first gradient θ1 of the opposing side wall 22 of the case 20, there is no surplus space as in the fuel cell 1A of FIG. 4. As a result, for example, when using cases 20 of the same size in the fuel cell 1 shown in FIG. 2 and the fuel cell 1A shown in FIG. 4, the fuel cell 1 can have a larger power generation area A1 and can increase the power generation amount. Also, when manufacturing fuel cells with the same power generation amount, the fuel cell 1 can make the case 20 smaller than the fuel cell 1A.

[0020] Also, as shown in FIG. 2, in the fuel cell 1 of the present embodiment, in the cell 11 having a substantially trapezoidal outer shape, the power generation area A1 is rectangular, and the peripheral area A2 is substantially trapezoidal along the gradient of the side edge 18. Specifically, that the power generation area A1 is rectangular may be rephrased as the membrane electrode assembly 13 being rectangular. Since the electrolyte membrane and the gas diffusion layer arranged in the power generation area A1 are obtained by cutting a roll material, if it is rectangular, cutting is easy and it can be used without loss of material. Since the catalyst layer is also formed by coating, if it is rectangular, it is easy to form using a die coater or the like. Therefore, regardless of the shape of the cell 11, if the power generation area A1 is rectangular, the manufacturing efficiency is excellent. In other words, it is preferable to use the non-rectangular area around the side edge 18 of the cell 11 as the peripheral area A2 where the manifold and other accessory elements are arranged.

[0021] In the fuel cell 1 of the present embodiment, both the shape of the accommodation space S and the shape of the cell 11 as viewed from the stacking direction are substantially trapezoidal. When manufacturing a case by casting, the ideal shape of the case is a rectangular parallelepiped. However, as described above, since a draft is required for castings, the shape of the case with a draft as viewed from the stacking direction is typically trapezoidal. Therefore, the case 20 having a trapezoidal accommodation space S is easy to manufacture. By matching the shape of the cell 11 to the trapezoidal accommodation space S, the volume efficiency can be increased.

[0022] In the mounted state where the fuel cell 1 is mounted on a vehicle, a power generation device, or the like, it is preferable that the gas outlet of the flow path of the cell 11 is below the gas inlet. That is, the fuel cell 1 is preferably used in a state where the hydrogen outlet 14b and the air outlet 15b are below the hydrogen inlet 14a and the air inlet 15a as shown in FIG. 2. Not only gas but also water generated by the reaction and condensation of hydrogen and oxygen is discharged from the gas outlet. By providing the gas outlet downward, the water generated in the flow path is easily guided to the gas outlet by gravity, and the drainage efficiency is improved.

[0023] Furthermore, in the state where the fuel cell 1 is mounted on a mounted object, it is preferable that the distance between the side walls of the opposing side walls 22 has a gradient so as to widen downward. That is, the fuel cell 1 is preferably used in an orientation where the upper wall 21 (bottom wall) with a small area is on top and the lower lid 25 with a large area is on the bottom as shown in FIG. 2. As shown in FIG. 2, in the peripheral region A2 of the fuel cell 1, the side on the upper wall 21 is narrow and the side on the lower lid 25 is wide. In the distribution of the gas of the fuel cell, the gas outlet is tend to be designed larger than the gas inlet. Therefore, by designing to mount the fuel cell 1 in a direction where the lower part is wider, it is easy to enlarge the gas outlet at the lower part, and each component can be arranged efficiently.

[0024] Next, another embodiment of the cell in the present disclosure will be described. In the following description, the same reference numerals are given to the components that have already been described, and the description thereof will be omitted as appropriate. FIG. 5 is a plan view of the cell 511 viewed from the stacking direction. As shown in FIG. 5, the cell 511 includes a frame body 12, a membrane electrode assembly 13, and each manifold. The cell 511 has a side edge 518R on one end side (R side, left side of the paper surface) and a side edge 518L on the other end side (L side, right side of the paper surface). The side edge 518R has a second gradient θ21, and the side edge 518L has a second gradient θ22. In the present embodiment, the angle of the second gradient θ21 of the side edge 518R is different from the angle of the second gradient θ22 of the side edge 518L.

[0025] As shown in FIG. 5, a manifold is disposed in a peripheral region A2 including side edges 518R and 518L. The area of each manifold is determined in consideration of various conditions. For example, hydrogen and air need to flow at a flow rate considering the required flow rate and effective utilization rate for power generation. Usually, the manifold for air is designed to be larger than the manifold for hydrogen. Also, in order to evenly distribute the fluid to a large number of stacked cells, the fluid inlet is designed to be small and the outlet is designed to be large. Furthermore, since hydrogen and air are converted into water by power generation, the mass flow rates at the inlet and outlet are different, and it is also considered that the volume flow rates of any fluid at the inlet and outlet are different due to the influence of temperature and pressure. As an example of an advantageous design considering the above, it is conceivable to make the hydrogen inlet small and the air outlet and the cooling water outlet large.

[0026] The manifold provided on the side edge 518L side of the cell 511 shown in FIG. 5 is based on the above design, with the hydrogen inlet 14a being relatively small and the air outlet 15b and the cooling water outlet 16b being relatively large. In the present embodiment, due to the large angle of the second gradient θ22 of the side edge 518L, it is easy to arrange these manifolds with different areas. Specifically, since the hydrogen inlet 14a does not become extremely horizontally long and the manifolds can be arranged well along the vertical direction, an increase in pressure loss can be avoided and the gas can be easily distributed evenly in the power generation region. On the other hand, in the present embodiment, there is no large area difference in the manifold on the side edge 518R side, and the gradient θ21 of the side edge 518R is the minimum gradient corresponding to the first gradient in the case not shown. Thus, by adjusting the second gradient of the side edge of the cell according to the design of the manifold, the manifold can be appropriately arranged.

[0027] In the description of the above embodiment, the case where the second gradients θ21 and θ22 of the side edges 518R and 518L are adjusted according to the design of the manifold has been described. However, the gradient of the side edge of the cell can be appropriately adjusted in consideration of any element arranged in the peripheral region, not limited to the manifold. For example, in order to provide positioning notches or holes (see the notch 171 and the hole 172 in FIG. 2) or cell monitor terminals (see the cell monitor terminal 174 in FIG. 2), the angle of the gradient of the side edge on one end side may be made larger or smaller than that on the other end side. By adjusting the gradient of the side edge, elements can be preferably arranged in the peripheral region.

[0028] Subsequently, another embodiment of the fuel cell of the present disclosure will be described. FIG. 6 is a diagram showing a fuel cell 601 according to another embodiment of the present disclosure, and shows the configuration of the cell 611 and the case 20 as viewed from the stacking direction. FIG. 6 is drawn in the direction in which the fuel cell 601 is mounted on the mounted object. As shown in FIG. 6, the fuel cell 601 has a gradient such that the distance between the side walls of the opposing side walls 22 of the case 20 widens upward, and the upper and lower portions of the case 20 are inverted compared to the fuel cell 1 in FIG. 2. The side edge 618 of the cell 611 has a gradient corresponding to the opposing side walls 22 of the case 20. Also in the cell 611, similar to the cell 11 shown in FIG. 2, the gas outlet is provided below the gas inlet. Specifically, the hydrogen outlet 14b and the air outlet 15b are below the hydrogen inlet 14a and the air inlet 15a. Further, the area of the manifold is designed such that the hydrogen outlet 14b and the air outlet 15b are larger than the hydrogen inlet 14a and the air inlet 15a.

[0029] As described above, the side edge 618 of the cell 611 has a gradient so as to expand upward, and since the manifold at the lower part of the peripheral region is designed to be large, there is a surplus area at the upper part of the peripheral region for arranging elements other than the manifold. As shown in FIG. 6, in the surplus area of the cell 611, there are arranged a positioning notch 171 and a hole 172, a cell monitor terminal 174, and a two-dimensional code 175 printed for cell identification. In the fuel cell 601 having a gradient such that the distance between the side walls of the opposing side walls 22 expands upward in the mounted state as in the present embodiment, it is easy to arrange various elements in the peripheral region of the cell 611. Further, as a method of storing the stack in the case in the fuel cell assembly process, there are a method of placing the case on top of the placed stack and a method of inserting the stack from above the placed case. Since the stack, which is a heavy object, is stored by being suspended, it is preferable to adopt the method of inserting the stack from above the placed case. The fuel cell 601 assumed to be used in the orientation shown in FIG. 6 has the advantage that there is no need to reverse the up and down because the assembly orientation and the use orientation are the same when the stack is inserted from above the placed case.

[0030] As described above, the fuel cell of the present disclosure has been described in detail by exemplifying specific embodiments, but the present disclosure is not limited to the exemplified embodiments.

[0031] In the above-described embodiment, the case where the molded body 201 is manufactured by casting has been described, but the processing method of the case 20 including the molded body 201 is not particularly limited, and forging or press molding may be used. Even in forging and press molding, a draft for removing the molded product from the mold is provided.

[0032] In the above-described embodiment, the case where the first gradient θ1 of the opposing side wall 22 is due to the draft has been described, but the first gradient θ1 is not limited to the draft. For example, the first gradient θ1 may be provided in the case 20 to prevent interference with another adjacent fuel cell 1 or other members when the fuel cell 1 is mounted on a vehicle or the like.

[0033] The angle of the first gradient θ1 may be, for example, not less than 0.5° and not more than 22°, or may be not less than 1.5° and not more than 12°. The draft gradient typically provided in casting is not less than 0.5°. When the gradient is not more than 22°, the difference between the upper side and the lower side of the case does not become excessively large, so that the floor area required for installing the fuel cell can be kept small, and the deterioration of the arrangement efficiency of the components outside the case can be avoided. The gradients of the left and right side walls of the opposing side walls 22 may be the same or different. The thickness of the opposing side walls 22 does not have to be uniform, and may be configured such that the thickness of the side walls gradually decreases or increases from the upper wall 21 toward the lower lid 25. Therefore, the angle formed by the inner surface of the opposing side wall 22 and the angle formed by the outer surface of the opposing side wall 22 may be different from each other with respect to the normal direction of the upper wall 21. The angle of the second gradient θ2 is not particularly limited, but may be, for example, not less than 0.5° and not more than 22°, or may be not less than 1.5° and not more than 12°.

[0034] In the above-described embodiment, the case where the angles of the first gradient θ1 and the second gradient θ2 are equal has been described, but the present disclosure is not limited to such a configuration. That is, even if the angles of the first gradient and the second gradient are different, as long as the side edges of the cell have a gradient in a direction along the gradient of the opposing side wall and the volume efficiency is improved as compared with the case where the side edges do not have a gradient, it can be said that "the second gradient corresponds to the first gradient", and it is included in the scope of the present disclosure.

[0035] The "substantially trapezoidal" in the present disclosure means a shape whose general shape is trapezoidal. Specifically, in addition to the shape of the cell 11 provided with the notch 171 shown in FIG. 2, a shape provided with small irregularities on each side, a shape with chamfered vertices, a shape with a slightly inclined upper side or lower side, etc. can also be referred to as substantially trapezoidal as long as the general shape is trapezoidal.

[0036] In the above-described embodiment, dimples are exemplified as a structure for evenly distributing gas in the power generation area, but the structure for gas distribution is not limited to dimples. For example, a plurality of flow paths leading from the gas inlet to the power generation area may be provided.

[0037] The fuel cell of the present disclosure may be of a single cell type or a bipolar type. The single cell type is a method of forming a fuel cell stack by fabricating single cells in which a frame supporting an MEA is sandwiched between bipolar separators and adhered, and stacking the single cells. The bipolar type is a method of forming a fuel cell stack by fabricating bipolar plates in which a cathode separator and an anode separator are joined, and alternately stacking the bipolar plates and the frame. That is, the cell in the present disclosure is not limited to a single cell having a cell configuration by itself, and may be a cell in a bipolar type in which the cell configuration is completed only after stacking.

[0038] The present disclosure includes the following content. (1) The fuel cell according to an embodiment of the present disclosure is a fuel cell stack in which a plurality of cells are stacked in a stacking direction, and a case having an accommodation space in which the fuel cell stack is accommodated, and is a fuel cell comprising the case has a bottom wall and opposing side walls having a first gradient rising from a peripheral edge of the bottom wall, the accommodation space is defined by the bottom wall and the opposing side walls, when viewed from the stacking direction, a side edge of the cell has a second gradient corresponding to the first gradient of the opposing side wall.

[0039] (2) In the above (1), the cell has a power generation region in which a membrane electrode assembly is disposed and a peripheral region provided with a flow path through which gas or refrigerant flows along the stacking direction, and when viewed from the stacking direction, the power generation region of the cell may be rectangular.

[0040] (3) In the above (1) or (2), an angle of the second gradient of a side edge on one end side of the cell and an angle of the second gradient of a side edge on the other end side of the cell may be different from each other.

[0041] (4) In any one of the above (1) to (3), when viewed from the stacking direction, the shape of the accommodation space and the shape of the cell may be substantially trapezoidal.

[0042] (5) In any one of (1) to (4) above, in the mounted state, the gas outlet of the cell may be located below the gas inlet.

[0043] (6) In (5) above, in the mounted state, the opposing side walls may have a gradient such that the distance between the side walls widens downward.

[0044] (7) In (5) above, in the mounted state, the opposing side walls may have a gradient such that the distance between the side walls widens upward.

[0045] (8) In any one of (1) to (7) above, the angle of the first gradient may be 0.5° or more and 22° or less.

Explanation of Reference Signs

[0046] 1, 1A, 601 Fuel Cell 10 Fuel Cell Stack 11, 11A, 511, 611 Cell 12 Frame 13 Membrane Electrode Assembly 14a Hydrogen Inlet 14b Hydrogen Outlet 15a Air Inlet 15b Air Outlet 16a Cooling Water Inlet 16b Cooling Water Outlet 171 Notch 172 Hole 173 Dimple 174 Cell Monitor Terminal 175 Two - Dimensional Code 18, 18A, 518L, 518R, 618 Side Edge 20 Case 21 Upper Wall (Bottom Wall) 22 Opposing Side Wall 23 Front Wall 231 Hole 24 Rear Cover 25 Lower Cover 201 Formed Body S accommodation space S1 surplus space A1 power generation area A2 peripheral area

Claims

1. A fuel cell comprising a fuel cell stack in which a plurality of cells are stacked in a stacking direction, and a case having an accommodation space in which the fuel cell stack is accommodated, wherein the case has a bottom wall, opposing side walls having a first gradient that rise while inclining in different directions from the peripheral edge of the bottom wall when viewed from the stacking direction, and a lower lid having a larger area than the bottom wall, the accommodation space is defined by the bottom wall and the opposing side walls, and the shape of the accommodation space and the shape of the cell are substantially trapezoidal when viewed from the stacking direction, and the fuel cell, wherein the side edge of the cell has a second gradient corresponding to the first gradient of the opposing side wall when viewed from the stacking direction.

2. The cell has a power generation region in which a membrane electrode assembly is disposed and a peripheral region provided with a flow path through which gas or refrigerant flows along the stacking direction, The fuel cell according to claim 1, wherein the power generation region of the cell is rectangular when viewed from the stacking direction.

3. The fuel cell according to claim 1 or claim 2, wherein an angle of the second gradient of a side edge on one end side of the cell is different from an angle of the second gradient of a side edge on the other end side.

4. The fuel cell according to claim 1 or claim 2, wherein in the mounted state, a gas outlet of the cell is located below a gas inlet.

5. The fuel cell according to claim 4, wherein in the mounted state, the opposing side walls have a gradient such that a distance between the side walls widens downward.

6. The fuel cell according to claim 4, wherein in the mounted state, the opposing side walls have a gradient such that a distance between the side walls widens upward.

7. The fuel cell according to claim 1 or claim 2, wherein an angle of the first gradient is 0.5° or more and 22° or less. ​

Images