JP7521486B2 - Separators for fuel cells - Google Patents

Description

The present invention relates to a separator for a fuel cell.

Patent Document 1 discloses a unit cell that constitutes a fuel cell stack. This unit cell has a membrane electrode assembly (MEA) and a first separator and a second separator that sandwich the MEA.

The MEA has a catalyst coated membrane (CCM) that has an electrolyte membrane and a catalyst layer, and gas diffusion layers (GDLs) provided on both sides of the CCM.

The first separator has multiple first groove channels for oxidizing gas and multiple cooling groove channels for the cooling medium. The first groove channels are linear and are formed on the surface of the first separator that faces the MEA. The unevenness of the first groove channels and the unevenness of the cooling groove channels are inextricably linked.

The second separator has a plurality of second groove channels for fuel gas and a plurality of cooling groove channels for cooling medium. The second groove channels are wavy and formed on the surface of the second separator facing the MEA. The unevenness of the second groove channels and the unevenness of the cooling groove channels are inextricably linked. The amplitude of the second groove channels is set to a size such that they overlap with the multiple convex portions that form the back surface of the multiple first groove channels in the first separator facing the second separator.

When such single cells are stacked, the contact area between the convex portion constituting the second groove flow path in one single cell and the convex portion constituting the back surface of the first groove flow path in the other single cell is increased. This improves the stability of the contact structure between adjacent separators, and therefore the stability of the contact structure between single cells.

JP 2018-78020 A

However, in such a single cell, the fuel gas flowing through the second groove passage is gradually consumed from the upstream side to the downstream side of the passage due to power generation. As a result, the flow rate of the fuel gas decreases on the downstream side of the groove passage, and this tends to reduce the flow rate of the fuel gas that sneaks into the GDL. As a result, there is a risk of a decrease in the amount of power generation on the downstream side of the groove passage.

It should be noted that this problem is not limited to separators having grooves for fuel gas, but also occurs in separators having grooves for oxidizing gas.
An object of the present invention is to provide a separator for a fuel cell that can suppress a decrease in the flow rate of a reactant gas that penetrates into a gas diffusion layer on the downstream side of a groove flow path.

The fuel cell separator for achieving the above object has an abutment surface that abuts against the power generation unit of the fuel cell, and the abutment surface is provided with a plurality of groove channels through which the reactant gas flows, the groove channels extending in a wavy manner in the planar direction of the abutment surface, and when the upstream side and downstream side of the groove channels in the flow direction of the reactant gas are defined as the upstream side and downstream side, the amplitude of the downstream side of the groove channels is larger than the amplitude of the upstream side.

As the reaction gas flows through the groove flow passage of the separator, it gradually penetrates into the power generation section adjacent to the separator, more specifically, into the gas diffusion layer that constitutes the power generation section. Here, with the above configuration, the amplitude of the downstream side of the groove flow passage is greater than the amplitude of the upstream side, so that the pressure loss of the reaction gas downstream of the groove flow passage is greater than the pressure loss of the reaction gas upstream. This promotes the penetration of the reaction gas into the gas diffusion layer downstream of the groove flow passage, compared to when the amplitude of the downstream side of the groove flow passage is the same as the amplitude of the upstream side. Therefore, it is possible to suppress a decrease in the flow rate of the reaction gas penetrating into the gas diffusion layer downstream of the groove flow passage.

FIG. 2 is an exploded perspective view showing a unit cell of the fuel cell. FIG. 2 is a plan view showing an embodiment of a separator for a fuel cell, in which a plurality of groove channels through which a fuel gas flows are arranged side by side. FIG. 4 is a perspective view showing the flow of fuel gas entering a gas diffusion layer from a groove flow path. FIG. 4 is a cross-sectional view showing the flow of fuel gas entering a gas diffusion layer from a groove flow path. FIG. 11 is a plan view showing a modified example of a groove flow path. FIG. 11 is a plan view showing a modified example of a groove flow path. FIG. 11 is a plan view showing a modified example of a groove flow path. FIG. 11 is a plan view showing a modified example of a groove flow path.

Hereinafter, one embodiment of a separator for a fuel cell will be described with reference to FIGS.
<Overall configuration of a single cell in a fuel cell stack>
As shown in FIG. 1, a unit cell of a fuel cell stack has a membrane electrode assembly 10 (hereinafter, MEA 10), a frame member 20 that supports the MEA 10, and a pair of separators 30, 40 that sandwich the MEA 10 and the frame member 20.

The unit cell as a whole has a rectangular plate shape.
In the following description, the stacking direction of the separator 30, the MEA 10, the frame member 20, and the separator 40 is defined as a first direction X.

In addition, the description will be given assuming that a direction perpendicular to the first direction X is a second direction Y, which is a longitudinal direction of the unit cell.
In addition, a direction perpendicular to both the first direction X and the second direction Y is referred to as a third direction Z in the following description.

The single cell has inlet holes 91, 93, and 95 for introducing a reactant gas or a cooling medium into the single cell, and outlet holes 92, 94, and 96 for discharging the reactant gas and the cooling medium in the single cell to the outside. In this embodiment, the inlet hole 91 and the outlet hole 92 are holes through which the fuel gas flows. The inlet hole 93 and the outlet hole 94 are holes through which the cooling medium flows. The inlet hole 95 and the outlet hole 96 are holes through which the oxidizer gas flows. Here, the fuel gas is hydrogen gas. The cooling medium is cooling water. The oxidizer gas is air.

The inlet holes 91, 93, 95 and outlet holes 92, 94, 96 are rectangular in plan view and extend in the second direction Y, penetrating the unit cell in the first direction X. The inlet hole 91 and outlet holes 94, 96 are provided on one side of the unit cell in the second direction Y (the left side in the left-right direction in FIG. 1). The inlet hole 91 and outlet holes 94, 96 are aligned in the third direction Z with a gap between them. The outlet hole 92 and the inlet holes 93, 95 are provided on the other side of the unit cell in the second direction Y (the right side in FIG. 1). The outlet hole 92 and the inlet holes 93, 95 are aligned in the third direction Z with a gap between them.

<MEA10>
As shown in FIG. 1, the MEA 10 has a rectangular shape that is elongated in the second direction Y when viewed in plan.
The MEA 10 has a solid polymer electrolyte membrane (hereinafter, electrolyte membrane) (not shown) and electrodes 11A, 11B provided on both sides of the electrolyte membrane. In this embodiment, the electrode bonded to one side (upper side in the vertical direction in FIG. 1 ) of the electrolyte membrane (not shown) in the first direction X is the cathode electrode 11A. The electrode bonded to the other side (lower side in FIG. 1 ) of the electrolyte membrane in the first direction X is the anode electrode 11B.

The electrodes 11A and 11B each have a catalyst layer (not shown) bonded to the electrolyte membrane, and a gas diffusion layer 12 (hereinafter, GDL 12) bonded to the catalyst layer.
The MEA 10 corresponds to the power generating section of the fuel cell according to the present invention.

<Frame member 20>
As shown in FIG. 1, the frame member 20 has a rectangular frame shape that is long in the second direction Y.
The frame member 20 is formed from, for example, a hard resin material.

The frame member 20 has through holes 21 , 22 , 23 , 24 , 25 , and 26 which form the holes 91 , 92 , 93 , 94 , 95 , and 96 .
The frame member 20 has, in the center, an opening 27 that is rectangular in plan view and long in the second direction Y. The MEA 10 is joined to the edge of the opening 27 from one side in the first direction X (the upper side in FIG. 1 ).

<Separator 30>
As shown in FIG. 1, the separator 30 has a rectangular plate shape that is elongated in the second direction Y when viewed from above.
The separator 30 is formed by press-molding a metal member such as titanium or stainless steel.

The separator 30 is provided on the anode electrode 11B side of the MEA 10. The separator 30 has a first surface 30A including a contact surface 30a (see FIG. 2) that contacts the MEA 10, and a second surface 30B opposite the first surface 30A.

The separator 30 has through holes 31, 32, 33, 34, 35, and 36 that constitute the holes 91, 92, 93, 94, 95, and 96. The through holes 31, 34, and 36 are provided at positions corresponding to the through holes 21, 24, and 26 of the frame member 20 in the third direction Z. The through holes 32, 33, and 35 are provided at positions corresponding to the through holes 22, 23, and 25 of the frame member 20 in the third direction Z.

The separator 30 has a number of groove channels 37 through which the fuel gas flows, and a number of groove channels 38 through which the cooling medium flows. Note that FIG. 1 shows a simplified view of the outer edge of the portion of the separator 30 in which the number of groove channels 37 are formed, and the outer edge of the portion in which the number of groove channels 38 are formed.

<Groove channels 37, 38>
As shown in FIG. 2, the plurality of groove channels 37 are grooves that connect the through holes 31 and 32. The plurality of groove channels 37 are provided on the first surface 30A. In this embodiment, the six grooves 37 are arranged at intervals in the third direction Z. That is, the six grooves 37 are independent of each other.

In the following description, the upstream side and downstream side of the groove passage 37 in the flow direction of the fuel gas will be simply referred to as the upstream side and downstream side.
The groove width, i.e., the cross-sectional area, of the groove 37 is constant throughout the extension direction of the groove 37. The groove widths of the grooves 37 are the same as each other.

The groove flow passage 37 is provided on the contact surface 30a and has a wavy portion 37a that extends in a wavy manner in the surface direction of the contact surface 30a. The wavelength λ of the wavy portion 37a is constant throughout the extension direction of the wavy portion 37a. The amplitude A of the downstream side of the wavy portion 37a is larger than the amplitude A of the upstream side. In detail, the amplitude A of the wavy portion 37a is larger toward the downstream side. The amplitude A of the wavy portion 37a is different for each wave. In addition, in the wavy portion 37a, each valley portion 71 located on one side of the third direction Z (the lower side in the vertical direction in FIG. 2) is located on the axis L along the second direction Y. In this embodiment, each of the six groove flow passages 37 has a wavy portion 37a. Each wavy portion 37a has the same shape.

As shown in FIG. 3, each wavy portion 37a is composed of a plurality of recesses 51 formed on the first surface 30A of the separator 30. Ribs 52 are provided between the recesses 51 as protrusions. The tips of the ribs 52 abut against the GDL 12 of the MEA 10 adjacent to the separator 30.

As shown in FIG. 2, the groove flow passage 37 located on the outermost side in the third direction Z among the multiple groove flow passages 37 is referred to as the outer groove flow passage 37A. The outer groove flow passage 37A has a portion located on the outer side of the outer edge of the contact surface 30a in the third direction Z.

As shown in FIG. 1, the multiple groove channels 38 are grooves that connect the through holes 33 and 34. The multiple groove channels 38 are provided on the second surface 30B. In the groove channels 38, the cooling medium flows in the opposite direction to the fuel gas flowing through the groove channels 37.

As shown in FIG. 3, the groove flow passage 38 is provided on the surface 30b opposite to the abutment surface 30a, and has a wavy portion 38a extending in a wavy manner in the surface direction of the surface 30b. Each wavy portion 38a is composed of a plurality of recesses 61 formed on the second surface 30B of the separator 30. Ribs 62 are provided as protrusions between the recesses 61. The back side of the rib 62 is the recess 51 that constitutes the wavy portion 37a of the groove flow passage 37. Similarly, the back side of the rib 52 is the recess 61 that constitutes the wavy portion 38a of the groove flow passage 38. In other words, the uneven shape that forms the wavy portion 38a of the groove flow passage 38 is inextricably linked to the uneven shape that forms the wavy portion 37a of the groove flow passage 37.

<Separator 40>
As shown in FIG. 1, the separator 40 has a rectangular plate shape that is elongated in the second direction Y when viewed from above.
The separator 40 is formed by press-molding a metal member such as titanium or stainless steel.

The separator 40 is provided on the cathode electrode 11A side of the MEA 10. The separator 40 has a first surface 40A including a contact surface that contacts the MEA 10, and a second surface 40B opposite the first surface 40A.

The separator 40 has through holes 41, 42, 43, 44, 45, and 46 that constitute the holes 91, 92, 93, 94, 95, and 96. The through holes 41, 44, and 46 are provided at positions corresponding to the through holes 21, 24, and 26 of the frame member 20 in the third direction Z. The through holes 42, 43, and 45 are provided at positions corresponding to the through holes 22, 23, and 25 of the frame member 20 in the third direction Z.

As shown in FIG. 1, the separator 40 has a plurality of groove channels 47 through which the oxidant gas flows, and a plurality of groove channels 48 through which the cooling medium flows. Note that FIG. 1 shows a simplified view of the outer edge of the portion of the separator 40 in which the plurality of groove channels 47 are formed, and the outer edge of the portion in which the plurality of groove channels 48 are formed.

The plurality of grooves 47 are grooves that connect the through holes 45 and 46. In the grooves 47, the oxidant gas flows in the opposite direction to the fuel gas flowing in the grooves 37.
The plurality of groove channels 48 are grooves that connect the through holes 43 and the through holes 44. In the groove channels 48, the coolant flows in the same direction as the oxidant gas flowing through the groove channels 47.

Next, the operation of this embodiment will be described.
3 and 4, the flow of fuel gas entering the GDL 12 from the groove flow passage 37 is indicated by arrows.

As shown in FIG. 3, as the fuel gas flows through the groove flow passage 37 of the separator 30, it gradually penetrates into the MEA 10 adjacent to the separator 30, more specifically, into the GDL 12 constituting the MEA 10. Here, according to the configuration of this embodiment, the amplitude A on the downstream side of the wavy portion 37a in the groove flow passage 37 is greater than the amplitude A on the upstream side, so that the pressure loss of the fuel gas on the downstream side of the groove flow passage 37 is greater than the pressure loss of the fuel gas on the upstream side. This promotes the penetration of the fuel gas into the GDL 12 on the downstream side of the groove flow passage 37 compared to when the amplitude A on the downstream side of the wavy portion 37a is the same as the amplitude A on the upstream side.

Next, the effects of this embodiment will be described.
(1) The wavy portion 37a of the groove 37 extends in a wavy manner in the planar direction of the contact surface 30a. The amplitude A of the wavy portion 37a on the downstream side is greater than the amplitude A on the upstream side.

This configuration achieves the above-mentioned effects. Therefore, it is possible to suppress a decrease in the flow rate of fuel gas that sneaks into the GDL 12 downstream of the groove flow passage 37. This also makes it possible to increase the amount of power generated downstream of the groove flow passage 37. Therefore, it is possible to improve the power generation efficiency of the fuel cell.

(2) The amplitude A of the wavy portion 37a is larger on the downstream side.
With this configuration, the pressure loss of the fuel gas increases toward the downstream side of the groove passage 37. As a result, the fuel gas is promoted to penetrate into the GDL 12 toward the downstream side where the flow rate of the fuel gas flowing through the groove passage 37 is smaller. Therefore, a decrease in the flow rate of the fuel gas penetrating into the GDL 12 can be effectively suppressed.

(3) The grooves 37 are independent of each other.
For example, when adjacent grooves 37 are connected to each other, the flow pressure of the fuel gas flowing through each groove 37 is uniformed at the connected portion. Therefore, it is difficult to adjust the pressure loss of the fuel gas for each groove 37 by making the amplitude A different between the upstream and downstream sides of each wavy portion 37a. In this regard, according to the above configuration, each groove 37 is independent from the others. Therefore, by making the amplitude A different between the upstream and downstream sides of each wavy portion 37a, it is possible to easily adjust the pressure loss of the fuel gas for each groove 37.

(4) Each of the grooves 37 has a wavy portion 37a that extends in a wavy manner in the planar direction of the contact surface 30a.
According to this configuration, the pressure loss of the fuel gas on the downstream side is larger than the pressure loss of the fuel gas on the upstream side in each of the groove passages 37. Therefore, the reduction in the flow rate of the fuel gas entering the GDL 12 on the downstream side of the groove passages 37 can be further suppressed.

(5) The outer groove flow passage 37A, which is the groove flow passage 37 located outermost in the third direction Z, which is the arrangement direction of each of the groove flow passages 37, has a portion located outer than the outer edge of the abutment surface 30a in the third direction Z.

As shown in FIG. 4, when there is a difference in the pressure loss of the fuel gas between adjacent groove channels 37, a portion of the fuel gas flowing through the groove channel 37 with the relatively large pressure loss may seep into the GDL 12 and flow to the groove channel 37 with the relatively small pressure loss. In this way, electricity is generated by the fuel gas seeping into the portion of the GDL 12 located between the adjacent groove channels 37.

However, in the outer groove flow passage 37A, there is no groove flow passage 37 outside of the outer groove flow passage 37A in the third direction Z. Therefore, when the entire outer groove flow passage 37A is located inside the abutment surface 30a in the third direction Z, the fuel gas is unlikely to penetrate into the portion of the GDL 12 located outside the outer groove flow passage 37A by taking advantage of the difference in pressure loss of the fuel gas as described above. As a result, this is one of the factors that reduces the power generation efficiency.

In this regard, with the above-mentioned configuration, the proportion of the portion of the GDL 12 that is located outside the outer groove flow passage 37A is reduced. This allows the fuel gas to penetrate a wider range of the GDL 12. This improves the power generation efficiency.

<Example of change>
This embodiment can be modified as follows: This embodiment and the following modifications can be combined with each other to the extent that there is no technical contradiction.

The shapes of the inlet holes 91, 93, 95 and the outlet holes 92, 94, 96 are not limited to a rectangular shape in plan view as illustrated in this embodiment. For example, the shapes of the inlet holes 91, 93, 95 and the outlet holes 92, 94, 96 may be a square shape or an oval shape in plan view.

The flow of the reactant gas in holes 91, 92, 93, 94, 95, and 96 is not limited to that exemplified in this embodiment. For example, hole 96 may be an oxidant gas inlet hole, and hole 95 may be an oxidant gas outlet hole. In addition, hole 94 may be a cooling medium inlet hole, and hole 93 may be a cooling medium outlet hole. In other words, the oxidant gas flowing through groove flow passage 47 and the cooling medium flowing through groove flow passages 38 and 48 may flow in the same direction as the fuel gas flowing through groove flow passage 37.

The number of grooves 37 is not limited to six as exemplified in this embodiment, but may be five or less, or seven or more.
The separator 30 is not limited to one in which each of the wavy portions 37a has the same shape as exemplified in this embodiment. For example, as shown in FIG. 5, the separator 30 may have grooves 37 having wavy portions 37b extending in a wavy manner in the surface direction of the abutting surface 30a and grooves 37 having wavy portions 37a arranged alternately in the third direction Z. Here, the wavelength λ of the wavy portion 37b is constant throughout the extension direction of the wavy portion 37b. In addition, the amplitude A of the wavy portion 37b is smaller toward the downstream side. The amplitude A of the wavy portion 37b on the upstream side is larger than the amplitude A of the wavy portion 37a on the upstream side. The amplitude A of the wavy portion 37b on the downstream side is smaller than the amplitude A of the wavy portion 37a on the downstream side.

With this configuration, there is a difference in the pressure loss of the fuel gas between adjacent groove channels 37. Therefore, on the upstream side, part of the fuel gas flowing through the wavy portion 37b of the groove channel 37, which has a relatively large pressure loss, penetrates the GDL 12 and flows toward the wavy portion 37a of the groove channel 37, which has a relatively small pressure loss. On the downstream side, part of the fuel gas flowing through the wavy portion 37a of the groove channel 37, which has a relatively large pressure loss, penetrates the GDL 12 and flows toward the wavy portion 37b of the groove channel 37, which has a relatively small pressure loss. In this way, power generation is also performed by the fuel gas penetrating the portion of the GDL 12 located between the adjacent groove channels 37. Therefore, the power generation efficiency of the fuel cell can be improved.

The groove width, i.e., the cross-sectional area of the groove 37 does not have to be constant over the entire extension direction of the groove 37 as long as the advantageous effects of the present invention are achieved.
The wavelength λ of the wavy portion 37a of the groove 37 does not have to be constant over the entire extension direction of the wavy portion 37a.

The groove flow passage 37 is not limited to the outer groove flow passage 37A having a portion located outside the outer edge of the abutment surface 30a in the third direction Z, as exemplified in this embodiment. For example, the outer groove flow passage 37A may be located at the same position as the outer edge of the abutment surface 30a in the third direction Z, or may be located inside the outer edge.

- The groove flow channels 37 are not limited to those that each extend in a wavy manner in the surface direction of the abutting surface 30a. In other words, it is not necessary for all of the groove flow channels 37 to have wavy portions 37a that extend in a wavy manner, but it is sufficient that at least one groove flow channel 37 has a wavy portion 37a.

- The groove flow paths 37 are not limited to being independent of each other as illustrated in this embodiment, but may be, for example, adjacent groove flow paths 37 connected to each other by another groove flow path extending in the third direction Z.

- The wavy portion 37a in the groove flow channel 37 is not limited to having a different amplitude A for each wave as illustrated in this embodiment. For example, as shown in FIG. 6, the amplitude A may increase in increments of a certain even number (two in FIG. 6), or the amplitude A may increase in increments of a certain odd number. Also, the amplitude A may increase in stages by combining even and odd numbers.

- The wavy portion 37a in the groove flow passage 37 is not limited to the valley portion 71 located on the axis L along the second direction Y as illustrated in this embodiment. For example, as shown in FIG. 7, the peak portion 72 of the wavy portion 37a may be located on the axis L. Also, as shown in FIG. 8, the wavy portion 37a may extend in a wavy shape centered on the axis L.

The separator for the fuel cell according to the present invention is not limited to the separator 30 joined to the anode electrode 11B side of the MEA 10 as exemplified in this embodiment, but can also be applied to the separator 40 joined to the cathode electrode 11A side.

The separators 30 and 40 are not limited to those formed by press-molding a metal member. For example, the separators 30 and 40 may be formed by cutting or etching.
The material used for the separators 30 and 40 is not limited to titanium or stainless steel, and aluminum or carbon may also be used.

A...Amplitude λ...Wavelength L...Axis X...First direction Y...Second direction Z...Third direction 10...Membrane electrode assembly, MEA
11A: cathode electrode; 11B: anode electrode; 12: gas diffusion layer, GDL
20: Frame member 21: Through hole 22: Through hole 23: Through hole 24: Through hole 25: Through hole 26: Through hole 27: Opening 30: Separator 30A: First surface 30a: Contact surface 30B: Second surface 30b: surface 31: through hole 32: through hole 33: through hole 34: through hole 35: through hole 36: through hole 37: groove flow passage 37A: outer groove flow passage 37a: wavy portion 37b: wavy portion 38: groove flow passage Path 38a... Wave-like portion 40... Separator 40A... First surface 40B... Second surface 41... Through hole 42... Through hole 43... Through hole 44... Through hole 45... Through hole 46... Through hole 47... Groove flow path 48... Groove Flow path 51: Recess 52: Rib 61: recess 62: rib 71: valley 72: peak 91: inlet hole 92: inlet hole 93: inlet hole 94: outlet hole 95: outlet hole 96: outlet hole

Claims (5)

A separator for a fuel cell, the separator having a contact surface that contacts a power generation section of the fuel cell, the contact surface being provided with a plurality of groove flow paths through which reactant gases flow, the separator comprising:
The groove extends in a wavy manner in a surface direction of the contact surface,
When the upstream side and the downstream side in the flow direction of the reaction gas in the groove flow passage are defined as the upstream side and the downstream side,
The amplitude of the downstream side of the groove flow channel is greater than the amplitude of the upstream side of the groove flow channel.
A separator for fuel cells. The amplitude of the groove flow channel is larger on the downstream side.
The separator for a fuel cell according to claim 1 . Each of the groove channels is independent of the others.
The separator for a fuel cell according to claim 1 or 2. Each of the groove channels extends in a wavy manner in a surface direction of the contact surface.
The separator for a fuel cell according to any one of claims 1 to 3. The outer groove channel, which is the groove channel located outermost in the arrangement direction of the groove channels, has a portion located at the same position as an outer edge of the abutment surface or located outside the outer edge in the arrangement direction.
The separator for a fuel cell according to any one of claims 1 to 4.