JP5098305B2 - Fuel cell separator and fuel cell - Google Patents

Description

  The present invention relates to a fuel cell separator and a fuel cell, and more particularly to a power generation gas distribution region of a fuel cell separator.

  A solid polymer fuel cell is composed of a polymer electrolyte membrane, a catalyst layer, and a gas diffusion electrode using a fuel gas containing hydrogen and an oxidant gas containing oxygen as a power generation gas, and is referred to as MEA (Membrane Electrode Assembly). Electricity and heat are generated by supplying the membrane-electrode assembly to an electrochemical reaction.

  In the fuel cell, the MEA is sandwiched between a pair of conductive separators composed of an anode separator and a cathode separator. In the gas flow region corresponding to the gas diffusion electrode of the MEA on the surface in contact with the MEA of the anode separator, a plurality of flow channel grooves through which the fuel gas flows are formed. Similarly, a plurality of flow channel grooves through which an oxidant gas flows are formed in the gas flow region corresponding to the gas diffusion electrode of the MEA on the surface in contact with the MEA of the cathode separator. The plurality of flow channel grooves are configured to connect the power generation gas supply hole and the power generation gas discharge hole provided in each separator to supply the power generation gas as uniformly as possible to the gas diffusion electrode surface of the MEA. ing.

  For this reason, when the fuel gas is supplied to the anode separator and the oxidant gas is supplied to the cathode separator, the power generation gas flows into the gas diffusion electrode constituting the MEA while flowing through the channel groove group in the power generation gas flow region. It is supplied and consumed by electrochemical reactions, generating electricity and heat.

  In order to generate power with MEA, the polymer electrolyte membrane needs to be in a sufficiently wet state, so at least the fuel gas of the power generation gas is supplied to the fuel cell together with water or water vapor and used for power generation. It is discharged from the fuel cell together with the fuel gas that has not been used. During power generation, water is generated by an electrochemical reaction on the cathode side, and this generated water is also discharged from the fuel cell together with an oxidant gas that has not been used for power generation.

  These moisture is partly condensed and discharged from the fuel cell in the form of liquid water, but this condensed water blocks a part of the flow channel and impedes gas flow. A phenomenon called flatting may occur, which makes the power generation performance uniform. Therefore, various ideas have been made to prevent flatting.

  For example, a separator in which a plurality of flow channel grooves are formed in a serpentine shape is a basic design concept, and a folded portion of the flow channel grooves is a lattice-shaped groove (see, for example, Patent Document 1).

  With this configuration, even if condensed water condenses in the middle of the channel groove and closes the channel groove, it is diverted again in the lattice groove portion, so that a uniform gas supply is possible again downstream of the lattice groove portion. Become.

  However, in the configuration of the above conventional separator, the contact area with the MEA in the grid-like groove portion is smaller than that of other flow channel grooves, so that the contact resistance increases, and a current density distribution occurs in the MEA plane. There is a possibility that the output performance is deteriorated and the local MEA is deteriorated. In view of this, a separator has been devised to reduce the difference in contact area (see, for example, Patent Document 2).

FIG. 8 is a front view of a conventional fuel cell separator. A power generation gas supply hole 1 is provided at the upper end of the fuel cell separator, and a power generation gas discharge hole 2 is provided at the lower end. The power generation gas flow region of the fuel cell separator is a flow path for power generation gas supplied to the gas diffusion electrode, and a flow channel groove 4 formed by the straight rib 3 is connected to the power generation gas supply hole 1. In addition, it is connected to the power generation gas discharge hole 2. Further, a recessed portion 6 in which a plurality of island-like protrusions 5 are erected from the bottom surface is provided in the folded portion of the flow channel groove 4. The rib 3 and the island-shaped protrusion 5 are in contact with the gas diffusion electrode of the MEA, and the separator also plays a role of collecting electricity generated by the gas diffusion electrode. In order to increase the contact area between the separator and the MEA, the recess 6 has a substantially triangular shape.
Japanese Patent Laid-Open No. 10-106594 JP 2000-164230 A

  However, in the conventional fuel cell separator, it is difficult to say that the difference in contact resistance due to the difference in contact area between the folded portion and the other portions is sufficiently reduced, and the contact resistance is made as uniform as possible. There is room for improvement.

  The present invention has been made in view of such circumstances, and suppresses the fluttering caused by condensed water in the flow channel groove, improves the uniformity of contact resistance, and improves the current density distribution in the MEA plane. It aims at providing the separator for fuel cells and the cell for fuel cells which can suppress generation | occurrence | production decline of output performance by generation | occurrence | production, and local degradation of MEA.

  In order to solve the above problems, the present invention provides a flow path formed by connecting a channel groove group formed by a plurality of linear ribs and a recess having a plurality of island-like protrusions standing from the bottom surface. And the island-shaped protrusion has a height higher than that of the linear rib.

  As a result, when the fuel cell is assembled with the MEA sandwiched, the contact pressure on the MEA can be increased by the protrusions by the ribs and the island-shaped protrusions that contact the MEA.

  Further, in the fuel cell of the present invention, the separator is one of a pair of separators that sandwich the MEA, and a gap that sandwiches the membrane electrode assembly of the pair of separators in the protrusion is narrow. is there.

  As a result, the projecting portion is more strongly in contact with the MEA than the other portions, so the contact resistance per unit area of the contact portion is reduced, and even if the contact area with the MEA is reduced, the contact resistance distribution is reduced. It is possible to design an optimal shape that suppresses the increase.

  According to the fuel cell separator and the fuel cell of the present invention, the uniformity of contact resistance is improved, the output performance is reduced due to the current density distribution in the MEA plane, and the local MEA is degraded. Can be suppressed.

  The first invention has a channel formed by connecting a channel groove group formed by a plurality of linear ribs and a recess portion in which a plurality of island-shaped protrusions are erected from the bottom surface. By forming a fuel cell separator characterized in that the protrusion is higher in height than the linear rib, when the fuel cell is assembled with the MEA sandwiched, the rib and the island-shaped protrusion contact the MEA. The contact pressure against the MEA can be increased by the protrusion.

  According to a second invention, in addition to the first invention, a flow path formed by connecting the flow path groove group and the recess is a serpentine-like fuel cell separator.

  In the third invention, in addition to the first or second invention, the island-shaped protrusions far from the end portions of the ribs connected to the recessed portions are higher than the island-shaped protrusions close to the end portions. By increasing the height, it is possible to prevent the MEA from being bent at the level difference between the rib and the island-shaped protrusion when the MEA is sandwiched.

  In addition to the third aspect, the fourth aspect of the invention increases in height as the upper surface of the island-shaped protrusion that is substantially parallel to the bottom surface of the depression is away from the end of the rib connected to the depression. By inclining in this way, it is possible to prevent the load from concentrating on the MEA at the edge portion of the upper surface of the island-shaped protrusion.

  In a fifth aspect of the present invention, the separator according to any one of the first to fourth aspects is any one of a pair of separators sandwiching the MEA, and the membrane electrode assembly of the pair of separators is sandwiched at the protrusions. Since the gap is narrow, it is possible to suppress the protrusion from coming into strong contact with the MEA as compared with the other portions and increasing the distribution of contact resistance.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to the embodiments. In addition, about the part same as a prior art example, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

(Embodiment 1)
FIG. 1 is an exploded view schematically showing an exploded view of a fuel battery cell according to Embodiment 1 of the present invention.

  As shown in FIG. 1, the fuel battery cell 10 includes an MEA 13 having a pair of gas diffusion electrodes 11 sandwiching a polymer electrolyte membrane 12 having a catalyst layer (not shown) on both surfaces, and a pair of anode separators 20. And a cathode-side separator 30.

  The anode-side separator 20, the cathode-side separator 30 and the MEA 13 have a fuel gas supply hole 14 for introducing a fuel gas containing hydrogen from the outside, and a fuel gas for discharging a fuel gas not used for power generation to the outside. An exhaust hole 15, an oxidant gas supply hole 16 for introducing an oxidant gas containing oxygen from the outside, and an oxidant gas discharge hole 17 for discharging an oxidant gas that has not been used for power generation to the outside. The fuel cell in the vicinity of the outer periphery is provided so as to penetrate when assembled.

  A fuel gas supply hole 14 and a fuel gas discharge hole 15 are connected to the surface of the anode-side separator 20 in contact with the gas diffusion electrode 11 so that the fuel gas is uniformly distributed to the gas diffusion electrode 11 to flow therethrough. A flow region 21 (a region surrounded by a two-dot broken line in the anode-side separator 20 in FIG. 1 is actually shown in FIG. 1 because it is in a non-visible surface and is indicated by a dotted line). The configuration of the fuel gas flow region 21 will be described in detail later.

  Further, an oxidant gas supply hole 16 and an oxidant gas discharge hole 17 are connected to the surface of the cathode-side separator 30 in contact with the gas diffusion electrode 11, so that the oxidant gas flows uniformly through the gas diffusion electrode 11. An agent gas flow region 31 (a region surrounded by a two-dot broken line in the cathode-side separator 30 in FIG. 1) is formed. The configuration of the oxidant gas flow region 31 will be described in detail later.

  Further, the MEA 13 is sandwiched by the anode-side separator or the cathode-side separator around the fuel gas supply hole 14, the fuel gas discharge hole 15, the oxidant gas supply hole 16, the oxidant gas discharge hole 17, and the gas diffusion electrode 11. When the fastening pressure is applied, the power generation gas (fuel gas and oxidant gas) enters the power generation gas flow region (the fuel gas flow region 21 or the oxidant gas flow region 31) on one predetermined surface. The seal portion 18 is provided so as not to leak to the other surface or the outside.

  In order to keep the temperature of the fuel cell 10 at an appropriate temperature, at least one of the anode-side separator 20 and the cathode-side separator 30 is provided with a structure through which a cooling fluid flows on the surface not in contact with the MEA 13. Here, a detailed description of the cooling fluid flow structure is omitted.

  Next, the configuration of the fuel gas flow region 21 and the oxidant gas flow region 31 disposed in the anode side separator 20 and the cathode side separator 30 will be described in detail with reference to the drawings.

  2 is a front view of the anode-side separator according to the first embodiment, FIG. 3 is a front view of the cathode-side separator according to the first embodiment, FIG. 4 is a fuel cell, and a cross section taken along the line AA in FIG. It is sectional drawing cut | disconnected by.

  As shown in FIG. 2, in the fuel gas flow region 21, a flow channel group in which a plurality of flow channels 23 partitioned by linear ribs 22 are gathered is supplied with fuel gas via at least one recess 24. It is formed by connecting the hole 14 and the fuel gas discharge hole 15. That is, as shown in FIG. 2, the channel group 23a connects the fuel gas supply hole 14 and the recess 24a, and another channel group 23b is connected to the recess 24b so that the recess 24a is folded back 180 degrees. This is repeated and connected to the fuel gas discharge hole.

  Further, as shown in FIG. 4, the cross section of the flow channel groove 23 and the straight rib 22 has a uniform pitch, a uniform width, and a uniform step, and the gas diffusion electrode 11 of the MEA 13 and the straight rib. The upper surface of 22 is in contact with the same contact pressure.

  Further, the recess 24 has a bottom surface that is flush with the bottom surface of the flow channel 23, and has a substantially triangular shape from the boundary between the recess 24 and the flow channel group and the outer periphery of the fuel gas flow region 21. It has a shape. In other words, the linear rib 22 can be made longer than the hollow portion having a substantially rectangular shape.

  Further, from the bottom surface of the recess 24, a plurality of island-like protrusions 25 arranged in an island shape are on the extension line of the linear rib 22 with a pitch equal to the pitch of the linear rib 22 and the width of the linear rib 22. It is erected with a uniform width. Further, the height H <b> 1 of the island-shaped protrusion 25 is formed higher than the height h <b> 1 of the linear rib 22. In the anode-side separator according to the first embodiment, all the island-shaped protrusions 25 have the same shape.

  With this configuration, even if the fuel gas is supplied to the anode separator 20 together with moisture (water or water vapor), it is blocked by the water supplied by a part of the channel groove 23 or the condensed water condensed with water vapor, so that an effective flow channel Even if the number of grooves is reduced, it is possible to return to the original number of flow channel grooves again downstream of the next depression 24, so that the effective area of the fuel gas flow area is prevented from decreasing. Is possible.

  As shown in FIG. 3, the cathode-side separator 30 has substantially the same configuration and shape as the anode-side separator 20, but in the first embodiment, air is used as the oxidant gas, so that it is larger than the fuel gas. Therefore, the number of flow channel grooves 33 constituting one flow channel group is larger than that of the anode-side separator 20, and the overall flow rate of the gas is increased. It differs from the anode side separator 20 in that the flow path length is shorter than the anode side separator 20. That is, the number of turn portions (recess portions 34) of the flow channel 33 is also smaller than that of the recess portions 24 of the anode separator 20. This also takes into account the fact that the water generated during power generation is discharged on the cathode side, so that it is necessary to drain condensed water together with air that was not used for power generation.

  The linear ribs 32 and the island-shaped protrusions 35 of the cathode-side separator 30 of the first embodiment correspond to the linear ribs 22 and the island-shaped protrusions 25 of the anode-side separator 20 when the fuel cell is assembled. Designed to take into account.

  However, from the viewpoint of the contact area between the gas diffusion electrode 11 and the contact areas of the anode-side separator 20 and the cathode-side separator 30, the contact area is reduced by discontinuous the flow channel, and the discontinuous shape If only, it will lead to an increase in contact resistance due to a decrease in contact area.

  However, when the MEA 13 is sandwiched between the anode-side separator 20 and the cathode-side separator 30 and the entire stacked surface of the fuel cells is fastened with a substantially uniform fastening force by a fastening structure (not shown), the gas diffusion electrode 11 of the MEA 13 The island-shaped protrusion 25 can be brought into contact with the anode-side separator 20 with a contact pressure higher than that of the linear rib 22. Similarly, in the cathode-side separator 30, the contact pressure at the island-shaped protrusion can be made higher than the contact pressure at the rib.

  FIG. 5 shows the contact resistance when a carbon cylinder, which is the material of the anode side separator 20 and the cathode side separator, is brought into contact with the gas diffusion electrode 11 used in Embodiment 1 while changing the contact pressure. The experimental result which measured change is shown.

  As shown in FIG. 5, the contact resistance decreases by increasing the contact pressure, and when the contact pressure is increased to a certain degree (where the contact pressure is about 6 kgf / cm 2 in FIG. 5), the decrease in the contact resistance is moderate. become.

  In general, a fuel cell is applied with a pressure that is substantially uniform and reduces the contact resistance between the gas diffusion electrode and the separator across the entire stack surface of the fuel cell (the surface corresponding to the main surface of the MEA). As shown, the fastening structure is not shown.

  On the other hand, increasing the fastening pressure and reducing the contact resistance involves increasing the cost of the material by increasing the strength of the fastening structure and compressing resistance, etc., so the contact pressure between the gas diffusion electrode and the rib Is the anode side separator and cathode side when fastened so that the contact pressure becomes a strength close to the bending point (where the contact pressure in FIG. 5 is about 6 kgf / cm 2) where the contact resistance decreases gradually. The gap distance with the separator is designed.

  Therefore, the contact area generated when the ribs are discontinuous by making the height of the island-shaped protrusions higher than the height of the ribs to increase the contact pressure and reduce the contact resistance when fastened. It is possible to suppress an increase in contact resistance due to a decrease in. Although it is difficult to compensate for the decrease in the contact area by improving the contact pressure, the increase in contact resistance is suppressed to improve in-plane uniformity, and the current density distribution in the MEA plane is generated. It is possible to suppress the occurrence of degradation in output performance and local MEA degradation.

  In the first embodiment, all the turn parts of the flow path group have a non-continuous configuration including the depressions and the island-shaped protrusions. However, a continuous flow path is partially formed as a serpentine-shaped flow path groove. The same effect can be obtained also in this case.

(Embodiment 2)
FIG. 6 is a diagram showing a fuel cell separator according to Embodiment 2 of the present invention, in which (a) is a front view of the main part of the fuel cell separator, and (b) and (c) are respectively in (a). It is sectional drawing of the principal part of a BB line cross section and CC line cross section.

  As shown in FIG. 6, the fuel cell separator of the present embodiment is different from the fuel cell separator of the first embodiment in that the height of the island-shaped protrusions gradually increases as the distance from the rib increases. It is different. That is, as shown in FIGS. 6B and 6C, when viewed from the cross section taken along line BB, if the height of the rib 41 is h1, the height of the island-shaped protrusions 42 is in the order of h2, h3, h4, h5. Further, even when viewed in the cross section along the line CC, the height of the island-like protrusions 42 is higher in the order of H2 and H3 than h1.

  With this configuration, when the MEA is sandwiched and assembled as a fuel cell and a fastening pressure is applied, the MEA can be prevented from bending due to the difference in height between the rib and the island-shaped protrusion. For this reason, the occurrence of peeling between the polymer electrolyte membrane, the gas diffusion electrode, and the catalyst layer due to bending of the MEA, and the cross leak between the anode side and the cathode side due to breakage of the polymer electrolyte membrane is suppressed, and the reliability is high. A fuel battery cell can be provided.

(Embodiment 3)
FIG. 7 is a diagram showing a fuel cell separator according to Embodiment 3 of the present invention, in which (a) is a front view of the main part of the fuel cell separator, and (b) is a DD line in (a). It is sectional drawing of the principal part of a cross section.

  As shown in FIG. 7, the fuel cell separator of the present embodiment and the fuel cell separator shown in the second embodiment and the height of the island-shaped protrusions are increased as the distance from the end of the rib increases. It is different in that it is inclined to.

  With this configuration, when the MEA is sandwiched and assembled as a fuel cell, and the fastening pressure is applied, compared to the fuel cell separator of the second embodiment described above, the MEA has a difference in height between the rib and the island-shaped protrusion. Since bending can be suppressed, a highly reliable fuel cell can be provided.

  The fuel cell separator according to the present invention can improve the uniformity of contact resistance, improve the output performance due to the occurrence of current density distribution in the MEA plane, and improve the occurrence of local MEA degradation. It can be applied to a polymer fuel cell.

1 is an exploded view schematically showing a fuel battery cell according to Embodiment 1 of the present invention. Front view of anode separator of same embodiment Front view of cathode side separator of same embodiment Sectional drawing of the principal part of the fuel cell of the embodiment The figure which shows the experimental result which shows the relationship between the contact pressure and contact resistance of the gas diffusion layer and the carbon material (A) Front view of main part of separator for fuel cell according to Embodiment 2 of the present invention (b) Cross-sectional view of main part taken along line BB in FIG. 6 (a) (c) In FIG. 6 (a) Sectional drawing of the principal part of a CC line cross section (A) Front view of main part of separator for fuel cell according to Embodiment 3 of the present invention (b) Cross-sectional view of main part taken along line DD in FIG. 7 (a) Front view of a conventional fuel cell separator

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Fuel cell 11 Gas diffusion electrode 12 Polymer electrolyte membrane 13 MEA
DESCRIPTION OF SYMBOLS 14 Fuel gas supply hole 15 Fuel gas discharge hole 16 Oxidant gas supply hole 17 Oxidant gas discharge hole 20 Anode side separator 21 Fuel gas flow area 22, 32, 41 Rib 23, 33 Channel groove 24, 34 Depression 25 , 35, 42 Island-shaped protrusions h1 Rib height h2, h3, h4, h5, H1, H2, H3 Height of protrusion

Claims (5)

  A channel groove group formed by a plurality of linear ribs and a recess formed by connecting a plurality of island-shaped protrusions from the bottom are connected to each other, and the island protrusions are the linear ribs. A fuel cell separator characterized by having a height higher than that of the fuel cell.   2. The fuel cell separator according to claim 1, wherein a flow path formed by connecting the flow path groove group and the recess is a serpentine shape.   The plurality of island-shaped protrusions are higher in height than the island-shaped protrusions that are separated from the end portions of the linear ribs that are connected to the recessed portions, as compared to the island-shaped protrusions that are close to the end portions. The fuel cell separator according to claim 1 or 2.   The island-shaped protrusions are inclined so that an upper surface substantially parallel to a bottom surface of the recess portion becomes higher as the distance from an end portion of the linear rib connected to the recess portion increases. The fuel cell separator according to claim 3.   5. A fuel cell comprising a pair of separators sandwiching a membrane electrode assembly, wherein the separator is any one of a pair of separators, and the pair of island-shaped protrusions causes the pair of separators. A fuel cell, wherein a gap for sandwiching the membrane electrode assembly of the separator is narrower than a gap for sandwiching the membrane electrode assembly in a portion not having the island-shaped protrusions.