Single cell of fuel cell

Abstract

A single cell of a fuel cell is provided with a frame-shaped holding plate to which the outer edge of a membrane electrode gas diffusion layer assembly is bonded, and a pair of separators. Holes penetrating the holding plate and the separators in the thickness direction are formed in the holding plate and the separators. The separator is joined to the holding plate by an adhesive. A plurality of ribs are formed on the separator. A concave-convex surface is formed on a portion between the hole and the membrane electrode gas diffusion layer assembly on the tip surface of the plurality of ribs in the protruding direction, and on a portion between the hole and the membrane electrode gas diffusion layer assembly on a contact surface of the holding plate that is in contact with the tip surface.

Description

TECHNICAL FIELD

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

[0002] A cell stack of a fuel cell is formed by stacking unit cells along a thickness direction. As shown in Japanese Patent Application Publication No. 2019-192327, a unit cell is provided with a holding plate and a pair of separators. The holding plate is formed in a frame shape of a quadrangle. The outer edge of a membrane electrode gas diffusion layer joint body is joined to the holding plate. The pair of separators sandwiches the holding plate and the membrane electrode gas diffusion layer joint body from both sides in the thickness direction. The separators are joined to the holding plate by an adhesive or the like.

[0003] A flow path for a fuel gas such as hydrogen to flow is formed between the separator on the anode side among both sides in the thickness direction of the membrane electrode gas diffusion layer joint body and the gas diffusion layer on the anode side of the membrane electrode gas diffusion layer joint body. In addition, a flow path for an oxidizing gas such as air to flow is formed between the separator on the cathode side among both sides in the thickness direction of the membrane electrode gas diffusion layer joint body and the gas diffusion layer on the cathode side of the membrane electrode gas diffusion layer joint body. A plurality of holes that pass through the holding plate and the separators along the thickness direction are formed in the holding plate and the separators. As such holes, there are holes that supply and discharge the fuel gas to and from the flow path for the fuel gas to flow, and holes that supply and discharge the oxidizing gas to and from the flow path for the oxidizing gas to flow.

[0004] A plurality of ribs that project toward the holding plate and the membrane electrode gas diffusion layer joint body are formed in the separators. The ribs are juxtaposed with each other. The flow path is formed between the plurality of ribs in the separators. A slit for connecting the hole in the holding plate and the flow path is formed between the hole in the holding plate and the membrane electrode gas diffusion layer. In the unit cell of the fuel cell, the fuel gas is supplied to the anode side of the membrane electrode gas diffusion layer joint body via the hole, the slit, and the flow path. In addition, the oxidizing gas is supplied to the cathode side of the membrane electrode gas diffusion layer joint body in the unit cell of the fuel cell via the hole, the slit, and the flow path. Furthermore, power generation is performed based on the reaction of the fuel gas and the oxidizing gas in the membrane electrode gas diffusion layer joint body. SUMMARY

[0005] PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] In the above-described unit cell, the separators are joined to the holding plate by an adhesive or the like. Therefore, the portions between the hole and the membrane electrode gas diffusion layer joint body on the surface of the holding plate side of the separator and the portions between the hole and the membrane electrode gas diffusion layer joint body on the contact surface of the holding plate with the above-described surface of the separator are also joined to each other by an adhesive or the like. However, in the joining of these portions to each other, the contact area is reduced due to the slit, and thus the joining strength can be reduced.

[0007] Solutions for solving the problems

[0008] A single cell of a fuel cell according to an aspect of the present disclosure includes: a frame-shaped holding plate to which an outer edge of a membrane electrode gas diffusion layer assembly is joined; and a pair of separators that sandwich the holding plate and the membrane electrode gas diffusion layer assembly from both sides in a thickness direction, a flow path for gas flow being formed between the separators and the membrane electrode gas diffusion layer assembly, a hole being formed in the holding plate and the separators that penetrates the holding plate and the separators along the thickness direction, the hole supplying and discharging gas to and from the flow path, wherein the separators are joined to the holding plate by an adhesive, a plurality of ribs are formed in the separators that project toward the holding plate and the membrane electrode gas diffusion layer assembly, the ribs are parallel to each other and extend to the hole, the flow path is formed between the plurality of ribs in the separators, and a concave-convex surface is formed at a position between the hole and the membrane electrode gas diffusion layer assembly of a top surface of the plurality of ribs in the separators in a projecting direction and a position between the hole and the membrane electrode gas diffusion layer assembly of a contact surface of the holding plate that contacts the top surface. BRIEF DESCRIPTION OF DRAWINGS

[0009] Figure 1 FIG. 1 is an exploded perspective view showing a single cell of a fuel cell.

[0010] Figure 2 FIG. 2 is a cross-sectional view showing a single cell of the fuel cell. Figure 1 FIG. 3 is a cross-sectional view showing a cell stack in which single cells of the fuel cell are stacked.

[0011] Figure 3 FIG. 4 is a diagram showing ribs and flow paths of separators in the single cell of the fuel cell. Figure 1 FIG. 5 is a cross-sectional view showing a position and an extending direction of a convex portion formed on a plurality of ribs in a separator.

[0012] Figure 4 FIG. 6 is a cross-sectional view showing a position and an extending direction of a convex portion formed on a plurality of ribs in a separator. Figure 1 FIG. 7 is a cross-sectional view showing a position and an extending direction of a convex portion formed on a plurality of ribs in a separator.

[0013] Figure 5 FIG. 8 is a perspective view showing a position at which ribs in a separator converge with each other. Figure 4 FIG. 9 is a perspective view showing a position at which ribs in a separator converge with each other.

[0014] Figure 6 FIG. 10 is a top view showing another example of a position and an extending direction of a convex portion formed on a plurality of ribs in a separator.

[0015] Figure 7 FIG. 11 is a top view showing another example of a position and an extending direction of a convex portion formed on a plurality of ribs in a separator.

[0016] Figure 8 FIG. 12 is a top view showing another example of a position and an extending direction of a convex portion formed on a plurality of ribs in a separator.

[0017] Figure 9 is a plan view showing the position and extending direction of the protrusions formed on the plurality of ribs in the separator.

[0018] Figure 10 is a plan view showing the position and extending direction of the protrusions formed on the plurality of ribs in the separator. DETAILED DESCRIPTION

[0019] Hereinafter, referring to the drawings, Figures 1-5 An embodiment of a single cell of a fuel cell will be described.

[0020] Figure 1 A single cell 11 for forming a cell stack of a fuel cell is shown. The single cell 11 is provided with a holding plate 12, a membrane electrode gas diffusion layer joint body 13, and a pair of separators 14. The holding plate 12 is formed in a frame shape of a rectangular shape by resin. The outer edge of the membrane electrode gas diffusion layer joint body 13 is joined to the holding plate 12. Further, the holding plate 12 and the membrane electrode gas diffusion layer joint body 13 are sandwiched by the separators 14 disposed on both sides in the thickness direction thereof.

[0021] A cell stack of a fuel cell is formed by stacking the single cell 11 described above in the thickness direction. The holding plate 12 and the separators 14 of the single cell 11 are formed with a plurality of holes 16 in a manner that they are penetrated in the thickness direction. Of the plurality of holes 16, three are located at one end in the long side direction of the single cell 11, and the other three are located at the other end in the long side direction of the single cell 11. The plurality of holes 16 are grouped into two by one hole at one end and one hole at the other end in the long side direction of the single cell 11. The holes 16 of each group are used for the flow of fluid such as fuel gas of hydrogen, oxidizing gas of air, and coolant such as cooling water.

[0022] The separator 14 is provided with a main body 15 formed in a plate shape of a rectangular shape by a metal such as stainless steel, titanium, and aluminum. A plurality of ribs 19 are formed in the main body 15 in a manner that they are juxtaposed and extend in the long side direction. A sealing member 17 is disposed between the main body 15 of the separator 14 and the holding plate 12. The sealing member 17 can be disposed on both the front and back surfaces in the thickness direction of the holding plate 12, respectively. The main body 15 of the separator 14 is joined to the holding plate 12 in a state that the sealing member 17 is sandwiched therebetween by an adhesive.

[0023] The seal member 17 disposed on the surface side of the holding plate 12 surrounds the two sets of holes 16 on one of the two diagonal lines of the holding plate 12 and the separator 14 and the anode side of the membrane-electrode gas diffusion layer assembly 13. The seal member 17 also surrounds the plurality of ribs 19 in the separator 14 on the anode side. Further, flow paths 18 for the flow of fuel gas are formed between the plurality of ribs 19 in the separator 14. The fuel gas can flow to the flow paths 18 via the two sets of holes 16. In other words, the two sets of holes 16 can supply and discharge the fuel gas to and from the flow paths 18.

[0024] The seal member 17 disposed on the back side of the holding plate 12 surrounds the two sets of holes 16 on the other of the two diagonal lines of the holding plate 12 and the separator 14 and the cathode side of the membrane-electrode gas diffusion layer assembly 13. The seal member 17 also surrounds the plurality of ribs 19 in the separator 14 on the cathode side. Further, flow paths 18 for the flow of oxidizing gas are formed between the plurality of ribs 19 in the separator 14. The oxidizing gas can flow to the flow paths 18 via the two sets of holes 16. In other words, the two sets of holes 16 can supply and discharge the oxidizing gas to and from the flow paths 18.

[0025] In the cell stack of the unit cell 11, the fuel gas flows to the anode side of the membrane-electrode gas diffusion layer assembly 13, and the oxidizing gas flows to the cathode side of the membrane-electrode gas diffusion layer assembly 13. In this way, when the fuel gas and the oxidizing gas flow to the anode side and the cathode side of the membrane-electrode gas diffusion layer assembly 13, power generation is performed based on the reaction of these fuel gas and oxidizing gas in the membrane-electrode gas diffusion layer assembly 13.

[0026] <Details of the ribs 19 in the separator 14>

[0027] As shown in FIG. 1, the membrane-electrode gas diffusion layer assembly 13 of the unit cell 11 has an electrolyte layer 20, a cathode electrode layer 21, an anode electrode layer 22, and a gas diffusion layer 23. The electrolyte layer 20 is formed of, for example, a solid polymer film. The cathode electrode layer 21 is joined to one side (the upper side in FIG. 1) of the thickness direction of the electrolyte layer 20. The anode electrode layer 22 is joined to the other side (the lower side in FIG. 1) of the thickness direction of the electrolyte layer 20. The surface of the cathode electrode layer 21 on the opposite side of the electrolyte layer 20 is covered with the gas diffusion layer 23. The surface of the anode electrode layer 22 on the opposite side of the electrolyte layer 20 is covered with a gas diffusion layer 23 different from the above-described gas diffusion layer 23. Figure 2 Figure 1 Figure 1

[0028] ​​​The separator 14 is located on both the cathode and anode sides of the membrane electrode gas diffusion layer assembly 13. Multiple ribs 19 in the cathode-side separator 14 are formed by bending the body 15 in a manner that protrudes towards the cathode-side gas diffusion layer 23. These ribs 19 are in contact with the cathode-side gas diffusion layer 23. The top surface 19a of the rib 19 in the protruding direction from the body 15 is parallel to the cathode-side gas diffusion layer 23. Flow paths 18 for the flow of oxidizing gas are formed between the multiple ribs 19 in the separator 14 and between the separator 14 and the gas diffusion layer 23.

[0029] Multiple ribs 19 in the anode-side separator 14 are formed by bending the body 15 in a manner that protrudes toward the gas diffusion layer 23 on the anode side. These ribs 19 are in contact with the gas diffusion layer 23 on the anode side. The top surface 19a of the rib 19 in the protruding direction from the body 15 is parallel to the gas diffusion layer 23 on the anode side. A flow path 18 for fuel gas flow is formed between the multiple ribs 19 in the separator 14 and between the separator 14 and the gas diffusion layer 23.

[0030] like Figure 3 As shown, the multiple ribs 19 arranged side by side are formed in a manner that converges towards each other as they approach the hole 16 of the main body 15 in the separator 14. Furthermore, the flow paths 18 between these ribs 19 are connected to the hole 16, thus reaching the hole 16. The parallel portions of the multiple ribs 19, more specifically, the top surfaces 19a of these portions, contact the gas diffusion layer 23 of the membrane electrode gas diffusion layer assembly 13 as described above. Additionally, the portions of the multiple ribs 19 that converge towards each other as they approach the hole 16, more specifically, the top surfaces 19a of these portions, are... Figure 4 It contacts the retaining plate 12 as shown. The retaining plate 12 has a contact surface 12a that contacts the aforementioned top surface 19a.

[0031] The top surface 19a of the rib 19 and the contact surface 12a of the retaining plate 12 are joined together by an adhesive. Therefore, the portion of the top surface 19a of the rib 19 located between the hole 16 and the membrane electrode gas diffusion layer connector 13, and the portion of the contact surface 12a of the retaining plate 12 that contacts the top surface 19a of the rib 19 located between the hole 16 and the membrane electrode gas diffusion layer connector 13, are joined together by an adhesive. More specifically, a protrusion 24 is formed, for example, by laser processing, at the portion of the top surface 19a in the protruding direction of the plurality of ribs 19 located between the hole 16 and the membrane electrode gas diffusion layer connector 13. Furthermore, a recess 25 is formed in the portion of the contact surface 12a of the retaining plate 12 that contacts the top surface 19a located between the hole 16 and the membrane electrode gas diffusion layer connector 13 to accommodate the protrusion 24. These protrusions 24 and recesses 25 form a convex-concave surface. This convex-concave surface is also included in the internal joining of the aforementioned portions.

[0032] As Figure 5 shown, the protrusions 24 extend in a direction intersecting the extending direction of the ribs 19. The protrusions 24 formed at the top end surface 19a of a prescribed rib 19 and the protrusions 24 formed at the top end surface 19a of another rib 19 located next to the prescribed rib 19 are located on the same straight line. Further, a plurality of protrusions 24 are formed at prescribed intervals along the extending direction of one rib 19. As Figure 3 shown by the thick dotted line, the farther apart the plurality of protrusions 24 are from the hole 16, the shorter the interval between the protrusions 24 becomes. At positions in the holding plate 12 corresponding to each of the protrusions 24 of each of the ribs 19, recesses 25 for receiving the protrusions 24 are formed.

[0033] Effects of the single cell 11 of the fuel cell in the present embodiment

[0034] (1) The portions of the top end surface 19a of the ribs 19 located between the hole 16 and the membrane electrode gas diffusion layer joint body 13 and the portions of the contact surface 12a of the holding plate 12 contacting the top end surface 19a of the ribs 19 located between the hole 16 and the membrane electrode gas diffusion layer joint body 13 are joined to each other by an adhesive. However, in the joining of these portions to each other, due to the relationship that the plurality of ribs 19 are formed protruding from the main body 15 of the partition 14, the adhesive area of the joined portions to each other tends to decrease. As a result, the joining strength of the portions to each other can decrease. In order to deal with such a situation, the concavo-convex surface is formed at the portions joined to each other. By forming the concavo-convex surface at the portions joined to each other, the contact area in the portions can be increased accordingly. As a result, the decrease in the joining strength of the portions to each other accompanying the decrease in the contact area of the joined portions to each other can be suppressed.

[0035] (2) The partition 14 is formed of metal, and the holding plate 12 is formed of resin. Therefore, it is easy to form the protrusions 24 at the top end surface 19a of the ribs 19 in the partition 14 by laser processing or the like, and it is easy to form the recesses 25 at the contact surface 12a of the holding plate 12 contacting the top end surface 19a. Thus, it is easy to form the concavo-convex surface based on the protrusions 24 and the recesses 25 at the portions of the top end surface 19a of the ribs 19 located between the hole 16 and the membrane electrode gas diffusion layer joint body 13 and the portions of the contact surface 12a of the holding plate 12 contacting the top end surface 19a located between the hole 16 and the membrane electrode gas diffusion layer joint body 13.

[0036] (3) In a case where formation of the protrusions 24 is intended to be achieved by a mold used for forming the partition 14, the cost of the mold increases. However, since the protrusions 24 are formed by laser processing, the increase in the cost of the mold as described above can be suppressed. In addition, if the protrusions 24 are formed by laser processing, the protrusions 24 are not necessarily limited to protruding in a circular arc shape, and are highly likely to become a complex protruding shape. In this case, the shape of the concave-convex surface constituted by the protrusions 24 and the recesses 25 also becomes complex, and thus the joining at the concave-convex surface becomes more robust by the anchoring effect.

[0037] (4) The protrusions 24 extend in a direction intersecting the extending direction of the ribs 19. In addition, the protrusions 24 formed at the top end surface 19a of a prescribed rib 19 and the protrusions 24 formed at the top end surface 19a of another rib 19 located next to the above-described rib 19 are located on the same straight line. Therefore, the formation of these protrusions 24 by laser processing becomes easy. That is, when the protrusions 24 are formed by laser processing, the movement of the laser head of the laser processing can be set to be linear, and thus the formation of the protrusions 24 becomes easy.

[0038] (5) The plurality of ribs 19 arranged in parallel are formed in a manner that the closer to the hole 16, the more the ribs 19 converge to each other. Therefore, the proportion of the top end surface 19a of the rib 19 per unit area in the holding plate 12 becomes smaller the farther from the hole 16. As a result, the joining strength of the top end surface 19a of the rib 19 and the contact surface 12a of the holding plate 12 at the site where they join each other between the above-described hole 16 and the membrane-electrode gas diffusion layer assembly 13 becomes lower the farther from the hole 16. However, the plurality of protrusions 24 in the rib 19 are closer to each other the farther from the hole 16. The joining strength at the above-described site where they join each other is increased by the concave-convex surface formed by the protrusions 24 and the recesses 25. Therefore, the joining strength of the site where they join each other is lower the farther from the hole 16, and this condition is suppressed by the concave-convex surface formed by the above-described protrusions 24 and the above-described recesses 25.

[0039] In addition, the above-described embodiment can be changed, for example, as follows. The above-described embodiment and the following changed examples can be implemented in combination with each other within a range where there is no technical contradiction.

[0040] The protrusions 24 can also be arranged as shown in Figure 6 , Figure 7 .

[0041] As shown in Figures 8-10 , the protrusions 24 can also extend in a manner inclined with respect to the extending direction of the ribs 19.

[0042] As shown in Figure 9 and Figure 10As shown, the prescribed protrusions 24 formed in the plurality of ribs 19 can also extend in a direction different from the other protrusions 24. In this case, the parallel movement of the partition 14 and the holding plate 12 in a plurality of directions can be effectively suppressed by the protrusions 24 extending in different directions and the recesses 25 that accommodate these protrusions 24.

[0043] The protrusions 24 do not necessarily need to extend in a direction intersecting the extending direction of the ribs 19.

[0044] The protrusions 24 do not necessarily need to be formed by laser processing, and can be formed by a mold for forming the partition 14, for example.

[0045] The material forming the partition 14 can also be appropriately changed.

[0046] The positional relationship of the protrusions 24 and the recesses 25 can also be reversed.

Claims

1. A unit cell of a fuel cell, comprising: a frame-shaped holding plate to which outer edges of a membrane electrode gas diffusion layer assembly are joined; and a pair of separators sandwiching the holding plate and the membrane electrode gas diffusion layer assembly from both sides in a thickness direction, a flow path for gas to flow being formed between the separators and the membrane electrode gas diffusion layer assembly, and a hole being formed in the holding plate and the separators to pass through the holding plate and the separators in the thickness direction, the hole supplying and discharging gas to and from the flow path, wherein the separators are joined to the holding plate by an adhesive, a plurality of ribs are formed in the separators to project toward the holding plate and the membrane electrode gas diffusion layer assembly, the ribs are juxtaposed with each other and extend to the hole, the flow path is formed between the plurality of ribs in the separators, a top end surface of the plurality of ribs in the projecting direction is formed with a concavo-convex surface at a position between the hole and the membrane electrode gas diffusion layer assembly, and a contact surface of the holding plate that contacts the top end surface is formed with a concavo-convex surface at a position between the hole and the membrane electrode gas diffusion layer assembly.

2. The unit cell of the fuel cell according to claim 1, wherein the separators are formed of metal, and the holding plate is formed of resin, a protrusion is formed at a position of the top end surface of the plurality of ribs in the projecting direction between the hole and the membrane electrode gas diffusion layer assembly, a recess that accommodates the protrusion is formed at a position of the contact surface of the holding plate that contacts the top end surface between the hole and the membrane electrode gas diffusion layer assembly, and the concavo-convex surface is formed by the protrusion and the recess.

3. The unit cell of the fuel cell according to claim 2, wherein the protrusion is formed by laser processing.

4. The unit cell of the fuel cell according to claim 3, wherein the protrusion extends in a direction intersecting an extending direction of the ribs, and the protrusion formed at a top end surface of a prescribed rib and the protrusion formed at a top end surface of another rib located beside the rib are located on the same straight line.

5. The unit cell of the fuel cell according to claim 3, wherein the protrusion extends in a direction intersecting an extending direction of the ribs, and a prescribed one of the protrusions formed in the plurality of ribs extends in a direction different from that of the other protrusions.

6. The unit cell of the fuel cell according to any one of claims 2 to 5, wherein the plurality of ribs that are juxtaposed are formed in such a manner that the closer they are to the hole, the more they converge toward each other, the protrusions are a plurality of protrusions formed at prescribed intervals in the extending direction of the ribs, and the more the plurality of protrusions are away from the hole, the shorter the intervals between the protrusions. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

Images