JP2017174563A - Fuel cell - Google Patents

Abstract

Provided is a fuel cell that efficiently and uniformly diffuses gas in a fuel cell. A fuel cell having catalyst layers (42, 52) on both sides of a solid polymer electrolyte membrane (31) and gas diffusion layers (43, 53) and separators (41, 51) outside the catalyst layers (42, 52). On the gas diffusion layers 43 and 53 side of the separators 41 and 51, manifolds 45 and 55 on the gas introduction side to the separators 41 and 51 are provided, and manifolds 46 and 56 on the gas discharge side from one side. A gas flow path formed by repeating the convex portions 44a and 54a contacting the gas diffusion layer and the concave portions 44b and 54b separating from the gas diffusion layers 43 and 53 over the other side where the gas diffusion layer is provided. 44 and 54 are provided, and the gas flow paths 44 and 54 communicate with each other through the gas diffusion layers 43 and 53 where the adjacent concave portions 44b and 54b are in contact with the convex portions 44a and 54a. Is formed. [Selection] Figure 1

Description

  The present invention relates to a fuel cell in which a solid polymer membrane is disposed between an anode (fuel electrode) and a cathode (air electrode).

  As a fuel cell, there is a polymer electrolyte fuel cell in which a fuel gas containing hydrogen is supplied to an anode and an oxidizing gas containing oxygen is supplied to a cathode to obtain an electromotive force by an electrochemical reaction occurring at both electrodes. Such a fuel cell has a basic structure in which a solid polymer membrane as an electrolyte membrane is disposed between an anode (fuel electrode) and a cathode (air electrode). A fuel gas containing hydrogen is supplied to the anode to supply hydrogen. A device that generates electricity by an electrochemical reaction that decomposes into hydrogen ions and electrons, supplies an oxidant gas containing oxygen to the cathode, and generates oxygen from oxygen ions and hydrogen ions generated by oxygen receiving the electrons. . In general, a separator, a gas diffusion layer, a catalyst layer, an electrolyte membrane, a catalyst layer, a gas diffusion layer, and a separator are sequentially stacked.

  The gas diffusion layer has high gas diffusibility for diffusing the gas supplied from the separator to the catalyst, high drainage for discharging liquid water generated by the electrochemical reaction out of the system, and the generated current. A high conductivity for extraction is required, and a gas diffusion electrode base material (hereinafter referred to as an electrode base material) made of carbon fiber or the like is widely used. The separator also has a function of separating the gas, a role as a current collector for electrically connecting adjacent cells, a role as a cell structure member, supplying a gas introduced from outside the system to the gas diffusion layer, and It has a function as a passage for discharging surplus gas and generated water to the outside of the system, and is generally produced by compression molding of a carbon composite material or press molding of a conductive resin plate material and a metal plate material.

  In such a fuel cell, the gas supplied from the separator needs to diffuse efficiently and uniformly into the catalyst. In addition, there is a problem that the gas diffusibility and drainage of the convex part of the uneven channel are low.

  Further, in the fuel cell, the gas diffusibility is lowered due to flooding in which condensed water generated by an electrochemical reaction is clogged in the gas diffusion layer (GDL) or plugging in which condensed water is not discharged from the gas flow path, and the battery performance is lowered. There is also a problem.

  In view of this, a technique has been proposed in which a partition member is provided in an outlet manifold communicating with the flow path of the separator, and gas is uniformly supplied to each fuel cell (see Patent Document 1).

  In addition, in order to prevent water retention in the electrode substrate and at the same time increase the contact area with the catalyst layer surface and reduce the contact resistance, a conductive microporous layer (MPL) on the catalyst layer side of the gas diffusion layer The technique which coats is proposed (refer patent document 2).

  In addition, by applying the MPL described above in a pattern on the separator side of the gas diffusion layer, the gas permeability is reduced, the gas is efficiently introduced into the catalyst, and the contact resistance with the separator is reduced. There is also a technique (see Patent Document 3).

  In recent years, a technique for reducing the cost of fuel cells has been proposed, and as one of them, a technique for providing a gas flow path normally provided in a separator in a gas diffusion layer has been proposed (Patent Documents 4, 5, 6).

JP 2009-176610 A JP 2003-303595 A International Publication No. 2013/099720 JP 2006-339089 A JP-A-2005-294121 JP 2011-233537 A

However, there is still a demand for improving the basic performance that the gas supplied from the separator diffuses efficiently and uniformly into the catalyst.
In view of the above-described problems, an object of the present invention is to provide a fuel cell that efficiently and uniformly diffuses gas in the fuel cell.

  A first aspect of the present invention that achieves the above object is a fuel cell having a catalyst layer on both sides of a solid polymer electrolyte membrane, and a gas diffusion layer and a separator provided outside the catalyst layer, wherein the separator The gas diffusion layer is in contact with the gas diffusion layer from one side where a gas introduction side manifold to the separator is provided to the other side where a gas discharge side manifold is provided. A gas flow path formed by repeating a convex portion and a concave portion that is separated from the gas diffusion layer is provided, and the gas flow channel includes the gas diffusion layer in which the adjacent concave portion is in contact with the convex portion. The fuel cell is formed by communicating with each other.

  In this aspect, since the convex portions and concave portions of the separator are extended in the direction intersecting the gas flow direction, and the convex portions and concave portions are provided intermittently in the gas flow direction, diffusion of gas to the electrode catalyst layer is promoted. Moreover, there is an effect that it becomes uniform.

In the second aspect of the present invention, the concave portion and the convex portion extend from one side of the direction intersecting the gas flow direction from the one side to the other side to the opposite side. The fuel cell according to the first aspect is provided.
In this embodiment, the diffusion of gas to the electrode catalyst layer becomes more uniform.

  According to a third aspect of the present invention, the gas diffusion layer is composed of a first layer on the catalyst layer side and a second layer on the separator side, and the first layer is water repellent compared to the second layer. The fuel cell according to the first or second aspect, wherein the second layer is more hydrophilic than the first layer.

  In such an embodiment, the condensed water of water vapor generated by the electrochemical reaction can be prevented from staying in the vicinity of the electrode catalyst layer, and the movement of the condensed water to the hydrophilic gas diffusion layer can be promoted.

According to a fourth aspect of the present invention, in the fuel cell according to the third aspect, the gas diffusion layer is provided with a plurality of spaces between the first layer and the second layer. is there.
In this aspect, the flow resistance of the gas in the gas diffusion layer is further reduced.

  A fifth aspect of the present invention is the fuel cell according to any one of the first to fourth aspects, wherein hydrophilic spacers are provided at both ends in the extending direction of the convex portion and the concave portion.

  In such an embodiment, the condensed water that has reached the separator is collected in the hydrophilic spacer and discharged out of the cell through the hydrophilic spacer.

  In the fuel cell of the present invention, the gas flow path of the separator is extended in the direction intersecting the gas flow direction and intermittently provided in the gas flow direction, so that the diffusion of the gas to the electrode catalyst layer is promoted and uniform. The effect of becoming.

1 is a schematic configuration diagram of a fuel cell according to Embodiment 1 of the present invention. 1 is a perspective view showing a schematic configuration of a fuel cell according to Embodiment 1 of the present invention. 1 is an exploded perspective view showing a schematic configuration of a fuel cell according to Embodiment 1 of the present invention. It is a schematic block diagram of the fuel cell which concerns on Embodiment 2 of this invention. It is a schematic block diagram of the fuel cell which concerns on the modification of this invention. It is a schematic plan view which shows the interface of the gas diffusion layer of the modification of this invention.

Hereinafter, the present invention will be described based on embodiments.
(Embodiment 1)
A fuel cell 11 that is a polymer electrolyte fuel cell of the present embodiment has a cell structure schematically shown in FIG. As shown in FIG. 1, the cell 30 of the fuel cell 11 includes an anode 40 that is a fuel electrode and a cathode 50 that is an air electrode with an electrolyte membrane 31 interposed therebetween, and a pair of separators 41 outside the anode 40 and the cathode 50. And 51 are provided. Hydrogen is supplied to the separator 41 on the anode 40 side, and air is supplied to the separator 51 on the cathode 50 side.

  The anode 40 and the cathode 50 include electrode catalyst layers 42 and 52 that are in contact with the electrolyte membrane 31 and gas diffusion layers 43 and 53 on the opposite side of the electrode catalyst layers 42 and 52 from the electrolyte membrane 31. And 53 are joined or brought into contact with separators 41 and 51.

  Examples of the electrolyte membrane 31 include hydrocarbon electrolyte resins such as polyether ketone, polyether ether ketone, and polyether sulfone in addition to fluorine-based electrolyte membranes such as perfluorocarbon sulfonic acid resin membranes represented by Nafion (trade name). Commonly used ones such as hydrocarbon electrolyte membranes into which ion exchange groups such as sulfonic acid groups, phosphoric acid groups, and carboxyl groups are introduced can be used.

  In addition, the electrode catalyst layers 42 and 52 usually contain an electrode catalyst having an catalytic activity for the electrode reaction in the anode 40 and the cathode 50 and an electrolyte material. As the electrode catalyst, one in which a catalyst component is supported on conductive particles is usually used. The catalyst component is not particularly limited as long as it has catalytic activity for the oxidation reaction of the fuel at the fuel electrode or the reduction reaction of the oxidant at the oxidant electrode, and is generally used for polymer fuel cells. What is used for can be used. For example, platinum or an alloy of platinum and a metal such as ruthenium, iron, nickel, manganese, cobalt, copper, and the like can be given. As the conductive particles as the catalyst carrier, carbon particles such as carbon black, conductive carbon materials such as carbon fibers, and metal materials such as metal particles and metal fibers can also be used.

  For the gas diffusion layers 43 and 53, a gas diffusion electrode substrate made of a conventionally known carbon fiber or the like is used. The gas diffusion layers 43 and 53 have a high gas diffusibility for diffusing the gas supplied from the separators 41 and 51 to the electrode catalyst layers 42 and 52, and liquid water generated by the electrochemical reaction is out of the system. High drainage for discharging and high conductivity for taking out the generated current are required, but any gas diffusion electrode substrate that is usually used can be used as long as it has these functions.

  Separators 41 and 51 are provided outside the anode 40 and the cathode 50 thus provided. As the separators 41 and 51, commonly used metal plates, conductive carbon plates, or the like are used, and gas flow paths 44 and 54 are provided on the gas diffusion layers 43 and 53 side. Specifically, the gas flow paths 44 and 54 are spaced from the surfaces of the convex portions 44a and 54a that are in contact with the surfaces of the gas diffusion layers 43 and 53 and the surfaces of the gas diffusion layers 43 and 53, respectively. The gas flow paths 44 and 54 are formed in the repeated direction by alternately and repeatedly providing the concave portions 44b and 54b for providing the. That is, the gaps in the adjacent recesses 44b and 54b communicate with each other via the gas diffusion layers 43 and 53 that are in contact with the protrusions 44a and 54a between them, and the gas flow paths 44 and 54 are in the recesses 44b and 54b. And the gas diffusion layers 43 and 53 are formed. The separators 41 and 51 having the convex portions 44a and 54a and the concave portions 44b and 54b are generally formed by press molding, but the forming method is not limited to this. Further, in the present embodiment, the convex portions 44a and 54a and the concave portions 44b and 54b are defined by the direction in which the convex portions 44a and 54a and the concave portions 44b and 54b repeat, that is, the direction of the gas flow paths 44 and 54 (the vertical direction in FIG. ) Extending in a direction orthogonal to () a direction orthogonal to the paper surface of FIG. 1, and extending from one side in the direction intersecting the gas flow direction to the other side opposite to each other. May be provided. In addition, on the upper and lower sides of the separators 41 and 51, introduction-side manifolds 45 and 55 and discharge-side manifolds 46 and 56 communicating with the gas flow paths 44 and 54, respectively, are provided. These detailed structures will be described later.

  In this way, a laminated body in which the anode 40 and the cathode 50 and the separators 41 and 51 are laminated with the electrolyte membrane 31 interposed therebetween is used as a set of cells 30, and a plurality of sets are stacked to form a fuel cell stack.

  FIG. 3 is an exploded perspective view of a part of the fuel cell stack 60. As shown in the figure, at the four corners of the fuel cell stack 60, there are provided flow paths penetrating in the stack direction. Although not shown in detail, an introduction flow path 61 through which hydrogen is introduced communicates with the introduction side manifold 45 of the separator 41 on the anode 40 side, and a discharge flow path 62 communicates with the discharge side manifold 46. It is configured. Further, the introduction side flow passage 63 through which air is introduced communicates with the introduction side manifold 55 of the separator 51 on the cathode 50 side, and the discharge side flow passage 64 communicates with the discharge side manifold 56. . Thus, hydrogen is supplied to the separator 41 on the anode 40 side of each cell 30 of the fuel cell stack, and air is supplied to the separator 51 on the cathode 50 side.

  Here, as shown mainly in FIGS. 2 and 3, the gas flow paths 44 and 54 provided in the separators 41 and 51 extend from one side 41a where the introduction-side manifolds 45 and 55 of the separators 41 and 51 are provided. The discharge side manifolds 46 and 56 are provided intermittently in the gas flow direction across the other side 41b. That is, the gas flow paths 44 and 54 each including a concave portion and a convex portion are provided at regular intervals in the gas flow direction. The gas flow paths 44 and 54 are continuously extended from one side 41c and 51c in the direction orthogonal to the gas flow direction to the other side 41d and 51d. , 54 end portions on the side sides 41c and 51c side and end portions of the side sides 41d and 51d are sealed by a sealing member of the fuel cell stack 60. In addition, although the space between each gas flow path 44 and 54 between the separator 41 and the separator 51 of the stack for fuel cells becomes a flow path through which cooling water flows, description is abbreviate | omitted.

  With the above-described configuration, the gas introduced from the inlet-side manifolds 45 and 55 of the separators 41 and 51 diffuses from the first concave portions 44b and 54b to the gas diffusion layers 43 and 53 that are in contact with the convex portions 44a and 54a. The gas diffused in the layers 43 and 53 sequentially enters the adjacent concave portions 44b and 54b, and further reaches the discharge side manifolds 46 and 56 while entering the gas diffusion layers 43 and 53 that are in contact with the convex portions 44a and 54a. (See FIG. 1). That is, the recesses 44b and 54b provided intermittently over the gas flow direction communicate with each other only through the gas diffusion layers 43 and 53 in contact with the projections 44a and 54a.

  As described above, the recesses 44b and 54b forming part of the gas flow paths 44 and 54 are extended in a direction intersecting the gas flow direction, and are provided intermittently alternately with the projections 44a and 54a in the gas flow direction. The gas diffuses from the recesses 44b and 54b to the gas diffusion layers 43 and 53 in contact with the projections 44a and 54a, and returns from the gas diffusion layers 43 and 53 to the voids in the recesses 44b and 54b. , 54b is diffused into the gas diffusion layers 43 and 53, so that the diffusion of the gas to the electrode catalyst layers 42 and 52 is promoted and uniform. There is also an advantage that discharge of the generated water is promoted. Compared with the case where the separators 41 and 51 are not provided with the convex portions 44a and 54a and the concave portions 44b and 54b, the concave portions 44b and 54b reduce the pressure loss, and the power generation efficiency is improved. Further, the water discharged to the separators 41 and 51 spreads on the separators 41 and 51, does not obstruct the gas flow, and is on both sides in the extending direction of the convex portions 44a and 54a and the concave portions 44b and 54b of the separators 41 and 51. It is discharged out of the cell through a hydrophilic spacer installed at the end.

(Embodiment 2)
FIG. 4 shows a schematic configuration of a cell of the fuel cell according to the second embodiment. In addition, the same code | symbol is attached | subjected to the same member as embodiment mentioned above, and the overlapping description is abbreviate | omitted.

  In the cell 30A of this embodiment, the gas diffusion layers 43A and 53A are two layers, the electrode catalyst layers 42 and 52 side are hydrophobic gas diffusion layers 431 and 531, the separators 41 and 51 side is a hydrophilic gas diffusion layer 432, 532. Here, the hydrophilicity and hydrophobicity of the hydrophobic gas diffusion layers 431 and 531 and the hydrophilic gas diffusion layers 432 and 532 are relative. For example, the hydrophilic gas diffusion layers 432 and 532 are hydrophobic gases. What is necessary is just to have hydrophilicity compared with the diffusion layers 431 and 531. For example, the hydrophobic gas diffusion layers 431 and 531 are normal gas diffusion layers, and the hydrophilic gas diffusion layers 432 and 532 are formed of a hydrophilic material, but may be gas diffusion layers subjected to hydrophilic treatment. . Alternatively, the hydrophilic gas diffusion layers 432 and 532 may be normal gas diffusion layers, and the hydrophobic gas diffusion layers 431 and 531 may be formed of a hydrophobic material or may be a gas diffusion layer subjected to hydrophobic treatment. Further, the hydrophobic gas diffusion layers 431 and 531 are formed of a hydrophobic material or subjected to a hydrophobic treatment, and the hydrophilic gas diffusion layers 432 and 532 are formed of a hydrophilic material or subjected to a hydrophilic treatment. It is good also as what you did.

  In this embodiment, condensate of water vapor generated by an electrochemical reaction is prevented from staying in the vicinity of the electrode catalyst layers 42 and 52, and the hydrophilic gas diffusion layers 432 and 532 on the separator 41 and 51 side of the condensate are obtained. Can be promoted. For this purpose, it is preferable that the hydrophilic gas diffusion layers 432 and 532 are made of a hydrophilic material or subjected to a hydrophilic treatment.

In addition, such a structure of the gas diffusion layers 43A and 53A, that is, the two-layer structure of the hydrophobic gas diffusion layers 431 and 531 and the hydrophilic gas diffusion layers 432 and 532, allows the gas flow paths 44 and 54 to be in the gas flow direction. By combining with a structure extending in the intersecting direction and intermittently provided in the gas flow direction, a more remarkable effect can be obtained. That is, in the structure in which the convex portions 44a and 54a and the concave portions 44b and 54b are extended in a direction intersecting the gas flow direction and are alternately provided alternately in the gas flow direction, the concave portions 44b and 54b are formed as shown in FIG. The region S that faces the convex portions 44a and 54a between the two is a gas retention region, but the condensed water can be retained in the region S even if the condensed water moves and is retained in the hydrophilic gas diffusion layers 432 and 532. There is an advantage that the gas flow is not hindered. Incidentally, in a normal separator structure, that is, a structure having a flow path in the gas flow direction, there is a possibility that the condensed water that is held may obstruct the gas flow.
Note that the two-layer structure of the gas diffusion layer of the present embodiment may be employed only on the cathode side where condensed water is generated.

(Other)
In the first and second embodiments described above, a microporous layer (MPL) may be provided on the electrode catalyst layer side, the separator side, or both of the gas diffusion layer, and a conventionally known microporous layer is adopted. I can do it.

  When MPL is provided on the electrode catalyst side, water retention in the electrode catalyst can be prevented, and at the same time, the contact area with the electrode catalyst layer surface can be increased to reduce the contact resistance. Further, the MPL provided on the separator side has an effect of reducing the in-plane gas gas permeability and efficiently introducing the gas into the catalyst and reducing the contact resistance with the separator. The MPL is generally formed by a coating technique, but may be provided in a predetermined pattern shape by pattern coating.

  In the two-layer structure of the gas diffusion layer of the second embodiment described above, a space (concave shape) may be formed at the interface between the two so that the gas flows into the space (concave shape). As a result, the gas flow resistance can be further reduced, and the gas diffusion efficiency can be improved.

  FIG. 5 shows a configuration in which the gas diffusion layer has a two-layer structure, a space (concave shape) is provided between the two layers, and a microporous layer (MPL) is provided on the electrode catalyst side and the separator side. In addition, the same code | symbol is attached | subjected to the same member as embodiment mentioned above, and the overlapping description is abbreviate | omitted.

  As illustrated, the gas diffusion layers 43B and 53B include hydrophobic gas diffusion layers 433 and 533 and hydrophilic gas diffusion layers 434 and 534, respectively. The hydrophobic gas diffusion layers 433 and 533 and the hydrophilic gas diffusion layers 434 and 534 have concave shapes 435 and 535 therebetween. The concave shapes 435 and 535 are formed long in the gas flow direction as shown in FIG. 6 showing the interfaces of the hydrophilic gas diffusion layers 434 and 534 on the hydrophobic gas diffusion layers 433 and 533 side. It is good also as a thing long in the direction which cross | intersects a flow. Further, the gas diffusion layers 43B and 53B include MPLs 436 and 536 and MPLs 437 and 537 on the electrode catalyst layers 42 and 52 side and the separators 41 and 51 side, respectively.

  In such an example, when MPLs 436 and 536 provided on the electrode catalyst layers 42 and 52 side are provided, water retention in the electrode catalyst is prevented, and at the same time, the contact area with the surface of the electrode catalyst layer is increased to reduce the contact resistance. be able to. Further, the MPLs 437 and 537 provided on the separators 41 and 51 side reduce the in-plane gas gas permeability so that the gas can be introduced into the catalyst more efficiently, and the contact resistance with the separators 41 and 51 There is an effect of reducing.

  Further, the hydrophobic gas diffusion layers 433 and 533 and the hydrophilic gas diffusion layers 434 and 534 are provided with concave shapes 435 and 535 therebetween, thereby reducing the gas flow resistance in the gas diffusion layers 43B and 53B. In addition, the diffusion efficiency of the gas into the catalyst can be improved.

  The present invention can be used in the industrial field of fuel cells for electric vehicles.

11 Fuel cell 30, 30A, 30B Cell 31 Electrolyte membrane 40 Anode 41, 51 Separator 42, 52 Electrode catalyst layer 43, 43A, 43B, 53, 53A, 53B Gas diffusion layer 44, 54 Gas flow path 45, 55 Inlet side manifold 46, 56 Exhaust side manifold 50 Cathode 431, 433, 531, 533 Hydrophobic gas diffusion layer 432, 434, 532, 534 Hydrophilic gas diffusion layer 435, 535 Concave shape 436, 437, 536, 537 Microporous layer (MPL)

Claims (5)

A fuel cell having a catalyst layer on both sides of a solid polymer electrolyte membrane, and a gas diffusion layer and a separator provided outside the catalyst layer,
On the gas diffusion layer side of the separator, the gas diffusion layer extends from one side where a gas introduction side manifold to the separator is provided to the other side where a gas discharge side manifold is provided. A gas flow path formed by repeating a convex portion that contacts and a concave portion that separates from the gas diffusion layer is provided,
The gas flow path is formed by connecting adjacent concave portions through the gas diffusion layer in contact with the convex portions.   The concave portion and the convex portion extend from one side in a direction intersecting a gas flow direction from the one side to the other side to the opposite side. 2. The fuel cell according to 1.   The gas diffusion layer includes a first layer on the catalyst layer side and a second layer on the separator side, the first layer is water repellent compared to the second layer, and the second layer is the first layer. The fuel cell according to claim 1, wherein the fuel cell is more hydrophilic than one layer.   The fuel cell according to claim 3, wherein the gas diffusion layer has a plurality of spaces between the first layer and the second layer. The fuel cell according to any one of claims 1 to 4, wherein hydrophilic spacers are provided at both ends in the extending direction of the convex portion and the concave portion.

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