JP2000294261A - Fuel cell stack - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance gas diffusiblity by gradually reducing the number of gas passage grooves as they come closer toward an gas outlet side from a gas inlet side, and causing a turbulent flow at the part where the number of the gas passage grooves is reduced. SOLUTION: First gas passage grooves 44a-44f in communication with a fuel gas inlet 36a and second gas passage grooves 50a-50d in communication with a fuel gas outlet 36b are provided on the surface 14a of a first separator 14, and first and second assembling parts 46, 48 are provided at a position where the first gas passage grooves 44a-44f meet the second passage grooves 50a-50d.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell stack in which a plurality of unit fuel cells each having an electrolyte sandwiched between an anode and a cathode are stacked with a separator interposed therebetween.

[0002]

2. Description of the Related Art For example, a solid polymer fuel cell is a unit fuel comprising an electrolyte comprising a polymer ion exchange membrane (cation exchange membrane) and an anode electrode and a cathode electrode provided on both sides of an electrolyte. It is constituted by sandwiching the battery cells by the separator. This polymer electrolyte fuel cell is usually used as a fuel cell stack by stacking a predetermined number of unit fuel cells and separators.

In this type of fuel cell, a fuel gas, for example, hydrogen gas, supplied to an anode electrode is hydrogen-ionized on a catalyst electrode and moves to a cathode electrode via a moderately humidified electrolyte. I do. The electrons generated during that time are taken out to an external circuit and used as DC electric energy. Since an oxidant gas, for example, oxygen gas or air is supplied to the cathode side electrode, the hydrogen ions, the electrons, and the oxygen gas react with each other to generate water at the cathode side electrode.

In order to supply a fuel gas and an oxidizing gas to the anode electrode and the cathode electrode, respectively, a conductive porous layer such as a porous carbon paper is usually provided on the catalyst electrode layer (electrode surface). Are sandwiched by the separators, and one or a plurality of gas passages having a uniform width are provided on the surfaces of the separators facing each other.

[0005] In this case, condensed water or water produced by the reaction may exist in the gas flow path in a liquid (water) state. If the water accumulates in the porous layer, the diffusivity of the fuel gas and the oxidizing gas into the catalyst electrode layer is reduced, and the cell performance may be significantly deteriorated.

Accordingly, for example, Japanese Patent Application Laid-Open No. 6-267564 describes
As disclosed in Japanese Unexamined Patent Publication, a fuel distribution plate having a fuel flow path for supplying fuel to the anode and an oxidant distribution plate having an oxidant flow path for supplying oxidant to the cathode are provided. A fuel cell has been known in which at least one of the depth and width of the oxidant flow path of the oxidant distribution plate is gradually reduced from the upstream flow area to the downstream flow area of the oxidant. I have.

[0007]

However, in order to supply the fuel gas and the oxidizing gas to the electrode surfaces sufficiently, the gas flow path is provided meandering or circling in the surface direction of the separator. . For this reason, the gas flow path is considerably elongated in the plane of the separator, and in the above-described conventional technology, the depth of the upstream flow path area of the oxidizing agent flow path is increased, so that the separator itself is considerably thick. It will be something.
As a result, it has been pointed out that the size of the entire fuel cell cannot be easily reduced. Moreover, there is a problem that the processing operation for gradually decreasing the depth from the upstream to the downstream of the gas flow path becomes extremely complicated.

An object of the present invention is to solve such a problem, and an object of the present invention is to provide a fuel cell stack capable of ensuring good gas diffusibility and drainage and effectively reducing the size. .

[0009]

In a fuel cell stack according to a first aspect of the present invention, a fluid passage for flowing a fluid containing at least one of a fuel gas and an oxidizing gas is provided in a plane of a separator. The fluid passage includes first and second gas flow grooves in which the number of grooves decreases from the gas inlet side to the gas outlet, and a plurality of the first and second gas flow grooves merge together. An assembly is provided. For this reason, when the fluid is consumed in the plane of the separator, the number of grooves decreases from the first gas passage groove to the second gas passage groove, so that the number of reactive molecules per unit area on the gas outlet side becomes smaller. The reaction can be made uniform within the electrode surface without being reduced as compared with the inlet side.

[0010] In addition, an aggregation portion is provided at a confluence of the plurality of first and second gas flow grooves. Therefore, turbulence is generated in the fluid at the collecting portion, and it becomes possible to improve the gas diffusibility of the fuel gas and / or the oxidizing gas to the electrode surface.

Further, the fuel gas and / or the oxidizing gas discharged from the plurality of first gas flow grooves are combined at the collecting portion, and then distributed to the plurality of second gas flow grooves.
For this reason, the distribution of gas between the plurality of second gas passage grooves is performed uniformly.

Further, in the fuel cell stack according to the second aspect, the number of the second gas passage grooves is set to two or more.
Even if one of the second gas passage grooves is closed due to condensation of the generated water or the like, the fluid can flow through another second gas passage groove. As a result, it is possible to prevent an increase in concentration overvoltage due to insufficient gas supply in the plane of the separator, and to stably obtain a cell voltage.

Further, in the fuel cell stack according to the third aspect, the flow direction of the first gas flow channel and the flow direction of the second gas flow channel are reversed through the collecting portion. For this reason, in the surface of the separator, the fluid passage can be arranged without any gap from the power generation surface, and the power generation performance can be effectively maintained.

[0014]

FIG. 1 is an exploded perspective view of a main part of a fuel cell stack 10 according to a first embodiment of the present invention.
FIG. 2 is a schematic longitudinal sectional view of the fuel cell stack 10.

The fuel cell stack 10 includes a unit fuel cell 12 and first and second separators 14 and 16 sandwiching the unit fuel cell 12, and a plurality of these units are stacked as needed. I have. The fuel cell stack 10 has a rectangular parallelepiped shape as a whole. For example, the short side direction (the direction of arrow A) is directed in the direction of gravity,
The long side direction (arrow B direction) is arranged to be oriented in the horizontal direction.

The unit fuel cell 12 has a solid polymer electrolyte membrane 18, an anode 20 and a cathode 22 disposed with the electrolyte membrane 18 interposed therebetween. The cathode-side electrode 22 has first and second gas diffusion layers 24 and 26 made of, for example, porous carbon paper as a porous layer.
Is arranged.

First and second gaskets 28, 30 are provided on both sides of the unit fuel cell 12, and the first gasket 28 is large for accommodating the anode 20 and the first gas diffusion layer 24. While having an opening 32, the second gasket 30 has a large opening 34 for accommodating the cathode-side electrode 22 and the second gas diffusion layer 26. Unit fuel cell 12 and first and second units
The gaskets 28, 30 are sandwiched between the first and second separators 14, 16.

As shown in FIGS. 1 and 3, in the first separator 14, a surface 14a facing the anode 20 and a surface 14b on the opposite side are set in a rectangular shape. And the short side 35b is arranged to be directed in the direction of gravity. The ratio between the long side 35a and the short side 35b is set to, for example, about 1.5 to 3: 1.

A fuel gas inlet 36a for passing a fuel gas such as hydrogen gas, and an oxidizing gas such as oxygen gas or air are passed through the first separator 14 on the upper side of both edges on the short side 35b side. And an oxidizing gas inlet 38a. A cooling medium inlet 40a for allowing a cooling medium such as pure water, ethylene glycol, or oil to pass therethrough is provided substantially at the center of both ends of the first separator 14 on the short side 35b side.
And a cooling medium outlet 40b, and a fuel gas outlet 36b and an oxidizing gas outlet 38b are provided at the lower part of both ends on the short side 35b side of the first separator 14 at a fuel gas inlet 36a and an oxidizing gas inlet. 38a is provided at a diagonal position.

A fuel gas passage (fluid passage) 42 communicating with the fuel gas inlet 36a and the fuel gas outlet 36b is formed on the surface 14a of the first separator 14. The fuel gas flow channel 42 includes a plurality of, for example, six (2 m) first gas flow channels 44a to 44f, and one end of the first gas flow channels 44a to 44f has a fuel gas inlet 36a. Communicate with

The first gas flow grooves 44a-44f extend in the horizontal direction (arrow B direction) from the fuel gas inlet 36a toward the oxidizing gas inlet 38a, and then extend downward (arrow A).
), And further extends horizontally from the cooling medium inlet 40a toward the cooling medium outlet 40b. In the vicinity of the cooling medium outlet 40b, three (m) first gas passage grooves 44a to 44c join the first collecting portion 46, and the remaining three (m) first gas passage grooves 44d to 44d. 44f
Merges into the second collecting part 48.

Two (n) second gas flow grooves 50a, 50b and 50c, 50d communicate with the first and second collecting portions 46, 48, respectively.
a to 50d extend in the horizontal direction and communicate with the fuel gas outlet 36b. The flow path cross-sectional areas of the first and second collecting portions 46 and 48 are respectively equal to the second gas flow path grooves 50a, 50b and 5
It is set to be equal to the total flow path cross-sectional area of 0c and 50d.

As shown in FIG.
Cooling medium flow paths (fluid passages) 52a to 52d are provided on the surface 14b opposite to 4a so as to communicate with the cooling medium inlet 40a and the cooling medium outlet 40b. Cooling medium channel 52
a to 52d are one main flow channel 54a, 54d communicating with the cooling medium inlet 40a and the cooling medium outlet 40b, respectively.
b, and a plurality of, for example, four branch flow grooves 56 provided between the main flow grooves 54a and 54b.

As shown in FIG. 1, the second separator 16 is formed in a rectangular shape, and a fuel gas inlet 58a and an oxidizing gas inlet are provided at upper ends of both short edges of the second separator 16. A cooling medium inlet 62a and a cooling medium outlet 62b are formed through the center of both ends of the cooling medium 60a. Second separator 1
The fuel gas outlet 58b
The oxidizing gas outlet 60b is formed so as to penetrate the fuel gas inlet 58a and the oxidizing gas inlet 60a in a diagonal position.

The cathode electrode 22 of the second separator 16
As shown in FIG. 2, an oxidizing gas passage (fluid passage) 64 that connects the oxidizing gas inlet 60a and the oxidizing gas outlet 60b is formed on the surface 16a facing the oxidizing gas. In the oxidizing gas passage 64, similarly to the fuel gas passage 42, the first gas passage grooves 66 a to 66 f and the second gas passage grooves 68 a to 68 d
Are formed to communicate with each other via first and second collecting portions (not shown), and detailed description thereof will be omitted.

As shown in FIG. 1, a cooling medium inlet 62 is provided on a surface 16b of the second separator 16 opposite to the surface 16a.
a and a cooling medium passage 70 communicating the cooling medium outlet 62b.
a to 70d are formed. Cooling medium passages 70a to 70d
Are configured in the same manner as the cooling medium channels 52a to 52d provided in the first separator 14, the same components are denoted by the same reference characters, and detailed description thereof will be omitted.

The operation of the fuel cell stack 10 according to the first embodiment configured as described above will be described below.

A fuel gas (for example, a gas containing hydrogen obtained by reforming a hydrocarbon) is supplied into the fuel cell stack 10, and air (or oxygen gas) is supplied as an oxidant gas. Is introduced from the fuel gas inlet 36 a of the first separator 14 into the fuel gas flow channel 42. As shown in FIG. 3, the fuel gas supplied to the fuel gas flow channel 42 is introduced into the first gas flow channel grooves 44 a to 44 f and extends in the long side direction (the direction of the arrow B) of the surface 14 a of the first separator 14. It moves in the direction of gravity while meandering along.

At this time, the hydrogen gas in the fuel gas is supplied to the anode 20 of the unit fuel cell 12 through the first gas diffusion layer 24. The unused fuel gas is first introduced into the first and second collecting portions 46 and 48 through the first gas flow grooves 44a to 44f, and then distributed to the second gas flow grooves 50a to 50d. The fuel gas is supplied to the anode 20 while moving in the direction of arrow B, while the remaining fuel gas is exhausted from the fuel gas outlet 36b.

In this case, in the first embodiment, six (2 m) first gas passage grooves 44a to 44m are provided at the fuel gas inlet 36a.
44f communicate with each other, and the first gas passage grooves 44a to 44f are provided with four (2n) second gas passage grooves 50a to 50d on the way.
And then to the fuel gas outlet 36b. Accordingly, in the surface 14a of the first separator 14, the number of grooves is reduced from the fuel gas inlet 36a toward the fuel gas outlet 36b, thereby preventing a decrease in the number of molecules per unit area due to gas consumption. The gas flow velocity on the 36b side can be increased. For this reason, the reaction water generated near the fuel gas outlet 36b can be effectively discharged to the fuel gas outlet 36b by increasing the gas flow rate, and drainage can be improved.

The first and second collecting portions 46 and 48 are provided at the junction of the first gas flow grooves 44a to 44f and the second gas flow grooves 50a to 50d. As a result, the first gas passage grooves 44a to 44c and 44d to 44d
Since the fuel gas supplied along f is once introduced into the first and second collecting portions 46 and 48, a turbulent gas flow is induced in the first and second collecting portions 46 and 48, and the fuel gas is supplied. The effect is obtained that the hydrogen gas in the gas can be effectively diffused and supplied to the anode 20. In addition, after the fuel gas discharged from the three first gas passage grooves 44a to 44c is combined at the first collecting part 46, the fuel gas is distributed to the two second gas passage grooves 50a and 50b. Therefore, there is an advantage that the fuel gas is uniformly distributed between the two second gas flow grooves 50a and 50b. The same applies to the other two second gas passage grooves 50c and 50d.

Further, the first and second collecting parts 46, 48
Are provided with two flow grooves (the second gas flow grooves 50, respectively).
a, 50b and 50c, 54d) are in communication. Therefore, even if one of the flow grooves is closed due to dew condensation or the like of the produced water, a smooth flow of the fuel gas is allowed through the other flow groove. Thereby, in the surface 14a of the first separator 14, an increase in concentration overvoltage due to insufficient gas supply can be prevented, and there is an advantage that the fuel cell stack 10 can be operated stably.

Here, the first and second collecting parts 46 and 48
The flow path cross-sectional area of the second gas flow path groove 50a, which is a distribution part,
The total flow path cross-sectional area of each of 50b, 50c, and 50d is set to be equal. For this reason, the first and second
The fuel gas can be smoothly sent out from the collecting portions 46 and 48 to the second gas passage grooves 50a to 50d.

Further, the first gas passage grooves 44a to 44a
The flow directions of f and the second gas flow grooves 50a to 50d are reversed via the first and second collecting portions 46 and 48. Therefore, there is an effect that the flow path can be arranged in the surface 14a of the first separator 14 without any gap from the power generation surface.

In the second separator 16, the air supplied from the oxidizing gas inlet 60a to the oxidizing gas flow path 64 moves in the gravity direction while meandering horizontally along the surface 16a. At this time, the oxygen gas in the air is supplied from the second gas diffusion layer 26 to the cathode 22 in the same manner as the fuel gas supplied to the fuel gas flow path 42, while the unused air is supplied to the oxidant gas outlet. Discharged from 60b.

Further, a cooling medium is supplied to the fuel cell stack 10, and the cooling medium is supplied to cooling medium inlets 40 a and 62 a of the first and second separators 14 and 16. As shown in FIG. 4, the cooling medium supplied to the cooling medium inlet 40a of the first separator 14 is introduced into each of the main flow grooves 54a that form the cooling medium flow paths 52a to 52d, and flows along the main flow grooves 54a. Flows upward, horizontally and downward. The cooling medium is introduced into the plurality of branch flow grooves 56 branched from the respective main flow grooves 54a, and flows in the horizontal direction over substantially the entire surface 14b along the branch flow grooves 56. The cooling medium is discharged from the cooling medium outlet 40b through the main channel groove 54b where the channel groove 56 joins.

On the other hand, as shown in FIG. 1, the cooling medium supplied to the cooling medium inlet 62a of the second separator 16 moves linearly over substantially the entire surface 16b through the cooling medium passages 70a to 70d. Thereafter, the air is discharged from the cooling medium outlet 62b.

FIG. 5 is an explanatory front view of one surface of a first separator 80 constituting a fuel cell stack according to a second embodiment of the present invention, and FIG. 6 is a third embodiment of the present invention. First separator 9 constituting a fuel cell stack according to the present invention
FIG. 7 is an explanatory front view of one surface of a zero. Note that the first
Of the fuel cell stack 10 according to the first embodiment.
The same components as those of the separator 14 are denoted by the same reference numerals, and a detailed description thereof will be omitted.

As shown in FIG. 5, the fuel gas inlet 36 is provided on the surface 80a of the first separator 80 according to the second embodiment.
a, and second gas passage grooves 50a-50d communicating with the fuel gas outlet 36b.
And the first gas flow channel grooves 44a to 44a
First and second gathering portions 82 and 84 are formed at the confluence of the 44f and the second gas passage grooves 50a to 50d.

The first collecting portion 82 is formed with the first gas passage groove 44c.
Communicate with the first gas passage grooves 44b and 44a
Has a first triangular portion 86 whose flow path cross-sectional area gradually increases toward a portion where the flow path communicates (downward), and a second gas flow is provided below the first triangular portion 86. Road groove 50
A second triangular portion 88 is provided in which the cross-sectional area of the flow channel gradually decreases toward a and 50b. The second collecting unit 84 is configured similarly to the first collecting unit 82 described above, and the same components are denoted by the same reference numerals, and
Detailed description is omitted.

The first separator 80 thus configured
Then, when the fuel gas supplied to the first gas flow grooves 44a to 44f is introduced into the first and second collecting parts 82 and 84, the fuel gas which joins the first and second collecting parts 82 and 84 Increases, the cross-sectional area of the flow path increases. On the other hand, as the fuel gas is distributed from the first and second collecting portions 82 and 84 to the second gas flow grooves 50a to 50d, the flow path cross-sectional areas of the first and second collecting portions 82 and 84 decrease. I have.

As a result, the fuel gas is uniformly and smoothly gathered from the first gas passage grooves 44a to 44f into the first and second gathering portions 82, 84, and the first and second gathering portions 82, 84 are formed.
The gas is smoothly and uniformly distributed from the collecting portions 82 and 84 to the second gas flow grooves 50a to 50d. For this reason, there is an effect that the flow of the fuel gas is efficiently performed.

As shown in FIG. 6, the surface 90a of the first separator 90 according to the third embodiment has the first gas flow channel 4
First and second collecting portions 92 and 94 are provided corresponding to the confluence of the 4a to 44f and the second gas flow grooves 50a to 50d. The first and second collecting portions 92 and 94 have a substantially triangular shape, and the cross-sectional area of the flow path increases as the first gas flow grooves 44a to 44f merge (downward).

For this reason, in the third embodiment, the fuel gas is smoothly and uniformly merged into the first and second collecting portions 92 and 94 through the first gas flow grooves 44a to 44f. The same effect as that of the embodiment can be obtained.

By the way, in the first to third embodiments,
First gas flow channel grooves 44a to 44a constituting fuel gas flow channel 42
4f and the second gas passage grooves 50a to 50d are configured to reverse the flow direction, but as shown in FIGS. 7 and 8, the fuel gas passages 10 having the same flow direction
0, 110 may be used.

As shown in FIG. 7, in the fuel gas flow path 100, the first gas flow grooves 102a to 102c and the second gas flow grooves 104a and 104b join at the collecting portion 106. The collecting portion 106 includes the first gas passage grooves 102a to 102a.
102c once merged, the sides become narrower in the same flow direction, and the second gas flow grooves 104a, 104
b is configured to distribute fuel gas.

As shown in FIG. 8, in the fuel gas flow channel 110, an aggregating portion 116 is provided at a confluence of the first gas flow channels 112a to 112c and the second gas flow channels 114a and 114b. First gas channel grooves 112b, 11
2c and the second gas channel grooves 114a and 114b are arranged on the same straight line.

The fuel gas flow path 10 thus configured
At 0 and 110, three (m) first gas passage grooves 102a to 102c and 112a to 112c are respectively two (n) second gas passage grooves 104a and 104b.
And 114a, 114b are once collected into a single collecting unit 106, 116. For this reason, turbulence can be generated in the fuel gas, and the diffusivity of the reaction gas to the electrode surface can be effectively improved. In addition, each of the three first gas passage grooves 102a-102
c, after the fuel gas discharged from 112a to 112c is merged at the collecting portions 106 and 116, two fuel gas
The gas is distributed to the gas flow grooves 104a, 104b, 114a, and 114b. Therefore, there is an advantage that the fuel gas is uniformly distributed between the two second gas flow grooves 104a, 104b, 114a, and 114b.

In the above description, the case where three flow grooves are narrowed down to two flow grooves basically has been described. However, the case where narrowing down from three to two in the separator surface is performed in two stages. There is. This will be described with reference to FIG. 9. First gas flow grooves 120 a to 120 i are provided on the inlet side, respectively, and the first gas flow grooves 120 a to 120 c are connected to the second gas flow grooves 1.
22a, 122b, and the first gas flow channel 120
d to 120f are narrowed to the second gas flow grooves 122c and 122d, and the first gas flow grooves 120g to 120i are narrowed to the second gas flow grooves 122e and 122f.

Further, the second gas passage grooves 122a-122
c is narrowed to the third gas flow grooves 124a and 124b, and the second gas flow grooves 122d to 122f are narrowed to the third gas flow grooves 124c and 124d.

The number of grooves may be reduced from three to two, besides four, three or two, or six, four or three. Is adopted. As a result, it is possible to freely adjust the pressure loss in the separator surface, thereby improving the water discharge performance and the degree of freedom in designing the fluid distribution in the stack.

[0052]

In the fuel cell stack according to the present invention, the fluid passage through which the fluid containing the fuel gas and / or the oxidizing gas flows has m first gas passage grooves on the gas inlet side, and The outlet side has n (m> n) second gas flow grooves, and an aggregation portion is provided at a confluence of the entire first and second gas flow grooves. Therefore, when the fluid flowing from the gas inlet side to the gas outlet side is consumed, the gas flow velocity is effectively prevented from decreasing, and gas turbulence is generated in the collecting part, and gas diffusion to the electrode surface is performed. Performance can be improved. In addition, since a decrease in flow velocity is prevented,
The water dischargeability is effectively improved, and it is possible to prevent a decrease in power generation performance due to condensation of water on the electrode reaction surface. Further, after the fuel gas and / or the oxidizing gas discharged from the plurality of first gas flow grooves are combined at the collecting portion, the fuel gas and / or the oxidizing gas are distributed to the plurality of second gas flow grooves. The distribution of gas between the second gas passage grooves is performed uniformly.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a main part of a fuel cell stack according to a first embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional explanatory view of the fuel cell stack.

FIG. 3 is an explanatory front view of one surface of a first separator constituting the fuel cell stack.

FIG. 4 is an explanatory front view of the other surface of the first separator.

FIG. 5 is an explanatory front view of one surface of a first separator constituting a fuel cell stack according to a second embodiment of the present invention.

FIG. 6 is an explanatory front view of one surface of a first separator constituting a fuel cell stack according to a third embodiment of the present invention.

FIG. 7 is a partial explanatory view of a fuel gas flow path when the flow directions are the same.

FIG. 8 is a partial explanatory view of another fuel gas flow path when the flow directions are the same.

FIG. 9 is an explanatory diagram in the case where the number of flow channel grooves is reduced from three to two in two stages.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10 ... Fuel cell stack 12 ... Unit fuel cell cell 14, 16 ... Separator 14a, 14b, 16a, 16b, 80a, 90a ... Surface 18 ... Electrolyte membrane 20 ... Anode side electrode 22 ... Cathode side electrode 24, 26 ... Diffusion layer 36a , 58a ... fuel gas inlet 36b, 58b ...
Fuel gas outlets 38a, 60a ... Oxidant gas inlets 38b, 60b ...
Oxidant gas outlets 40a, 62a, ... Cooling medium inlets 40b, 62b ...
Cooling medium outlets 42, 100, 110 ... fuel gas flow paths 44a to 44f, 50a to 50d, 66a to 66f, 6
8a-68d, 102a, 102b, 112a-112
c, 114a, 114b ... gas flow grooves 46, 48, 82, 84, 92, 94, 106, 116
... Collecting parts 52a to 52d, 70a to 70d... Cooling medium flow path 64. Oxidizing gas flow path 80, 90.

Claims (3)

[Claims] 1. A fuel cell stack in which a plurality of unit fuel cells each comprising an electrolyte sandwiched between an anode electrode and a cathode electrode are stacked with a separator interposed therebetween. A fluid passage is provided for flowing a fluid containing at least one of a fuel gas supplied to the anode electrode and an oxidizing gas supplied to the cathode electrode, and the fluid passage is provided on the gas inlet side. M (m is a natural number) first gas flow grooves formed in the gas outlet; n (n is a natural number, m> n) second gas flow grooves formed on the gas outlet side; An aggregation portion provided at a confluence of the gas flow channel and the second gas flow channel and integrally communicating the m first gas flow channels and the n second gas flow channels. A fuel cell stack comprising: 2. The fuel cell stack according to claim 1, wherein the number of the second gas passage grooves is two or more. 3. The fuel cell stack according to claim 1, wherein the flow direction of the first gas flow channel and the flow direction of the second gas flow channel are reversed via the collecting portion. And a fuel cell stack.