JP5278056B2 - Manufacturing method of fuel cell separator - Google Patents

Description

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

  A polymer electrolyte fuel cell is a device that supplies air and fuel (fuel fluid) to an air electrode and a fuel electrode (electrode), respectively, and obtains electric power by an electrochemical reaction at each electrode. Conventionally, in a polymer electrolyte fuel cell, a solid polymer membrane (electrolyte membrane), a catalyst layer provided on both sides of the solid polymer membrane, and the solid polymer membrane and each catalyst layer are sandwiched. A configuration (cell stack) is employed in which single cells including a gas diffusion layer are stacked in series via a separator such as a metal plate.

  The separator prevents the mixing of the air and fuel of each adjacent single cell, and electrically connects the single cells. The gas diffusion layer is configured by a thin plate made of a conductive porous material, a large number of grooves formed on the surface of the separator, and the like in order to supply a fuel fluid to each catalyst layer.

  For example, in Patent Document 1, the porous material is diffusion bonded to the separator to increase the contact area between the separator and the porous material, thereby reducing the electrical resistance and improving the efficiency.

JP 2004-186116 A

  In such a fuel cell, in order to obtain a large voltage, the number of single cells in the cell stack is increased, while a reduction in size and weight of the device is required. For this reason, for example, it is conceivable to make the gas diffusion layer thin. However, if the fluidity of the fluid is lowered by making the gas diffusion layer thin, it becomes difficult to smoothly supply the fuel fluid to each catalyst layer. For this reason, the efficiency of the electrochemical reaction is reduced, and the power generation efficiency may be reduced.

  In addition, due to a decrease in flowability in the gas diffusion layer, the water generated by the electrochemical reaction is likely to stay in the gas diffusion layer and be difficult to be discharged, resulting in a phenomenon that the reaction efficiency decreases or stops (so-called flooding). There is. Furthermore, when the flowability in the gas diffusion layer is low, the power of an auxiliary machine such as a pump that supplies a fuel fluid to the gas diffusion layer increases, and the power generation efficiency may be reduced.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a method for manufacturing a fuel cell separator that realizes a polymer electrolyte fuel cell that is small and light and has excellent power generation efficiency.

The present invention provides a metal slurry layer forming step of forming a metal slurry layer containing metal powder and a binder on the surface of a separator plate made of a metal flat plate, and forming a slit in the metal slurry layer on the separator plate, A slit forming step for forming small pieces, and firing the metal slurry layer to make the metal porous material while shrinking the small pieces and expanding the slit by the shrinkage, the flow path comprising the enlarged slit is the And a firing process for forming a gas diffusion layer disposed between the small pieces.
Here, the metal slurry layer may be formed by directly applying the metal slurry to the separator, or the metal slurry may be formed into a plate shape on a carrier sheet or the like and dried and peeled over the separator. .

  According to this manufacturing method, since the gas diffusion layer is formed by the plurality of small pieces made of the metal porous material and the flow path formed between the small pieces, the fuel fluid is smoothly passed through the entire gas diffusion layer through the flow path. Further, a fuel cell separator having excellent flowability can be realized, which can supply the fuel fluid uniformly to each electrode through the pores in the small pieces made of the metal porous material from the flow path.

  In this manufacturing method, the slit is preferably formed by cutting the metal slurry layer. In this case, the slit can be formed by a simple operation of cutting the metal slurry layer applied to the separator plate with a cutter or the like.

  In this manufacturing method, it is preferable that the metal slurry layer further includes a foaming agent, and further includes a foaming step of foaming the metal slurry layer before the slit forming step. In this case, by appropriately adjusting the content ratio of each material constituting the metal slurry layer, the particle size of the metal powder, the material of the foaming agent, the foaming temperature, etc., a metal porous material having an arbitrary porosity or pore diameter can be obtained. Can be formed. In addition, by appropriately adjusting the particle size of the metal powder, the amount of the binder, and the like, the shrinkage rate of the metal slurry layer in the firing step can be adjusted, so that the flow path in the gas diffusion layer can be formed with an arbitrary width.

  In this manufacturing method, it is preferable that the separator plate and the metal porous material are made of the same metal material. In this case, the corrosion of the fuel cell separator can be suppressed as compared with the case where the separator plate and the metal porous material are made of different metal materials.

  Moreover, in this manufacturing method, it is preferable that the said metal porous material consists of a corrosion-resistant metal. In this case, corrosion of the gas diffusion layer due to a corrosive environment such as sulfuric acid generated in the fuel cell can be suppressed.

  According to the method for manufacturing a fuel cell separator of the present invention, a fuel cell separator having a gas diffusion layer capable of uniformly diffusing the fuel fluid and supplying the fuel fluid uniformly and efficiently to each electrode can be realized. Therefore, even if the gas diffusion layer is made thin, sufficient flowability can be ensured, so that a fuel cell with good power generation efficiency can be realized while being small and light.

It is a perspective view which shows the manufacturing method of the separator for fuel cells of this invention. It is a schematic diagram which shows the manufacturing apparatus of the green sheet used as a metal slurry layer. It is a schematic diagram which shows a fuel cell provided with the separator for fuel cells manufactured by the method of this invention. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells. It is a top view which shows the other example of the shape of the flow path in the separator for fuel cells.

  Hereafter, the manufacturing method of the separator for fuel cells which concerns on this invention is demonstrated. The present invention includes a metal slurry layer forming step of forming a metal slurry layer 16 containing a metal powder and a binder on a surface 12a of a separator plate 12 made of a metal flat plate (FIG. 1A), and a metal slurry on the separator plate 12 A slit forming step of forming slits 16a in the layer 16 and forming a plurality of small pieces 16b (FIG. 1 (b)), and firing the metal slurry layer 16 to make the porous pieces while shrinking the small pieces 16b. This is a method for manufacturing a fuel cell separator having a firing step in which a slit 16a is enlarged by the contraction and a flow path 15 including the enlarged slit 16a forms a gas diffusion layer 14 disposed between the small pieces 16b. .

<Metal slurry layer forming step>
The metal slurry layer 16 of the present embodiment is formed by placing a green sheet G containing metal powder on the surface 12 a of the separator plate 12.
Green sheet G
Metal powder: Stainless steel (SUS316L) powder, 40-60% by weight, average particle size of about 10 μm
Binder: Polyvinyl alcohol, 5 to 15% by weight
Surfactant: Alkylbenzene sulfonate, 1 to 3% by weight
Foaming agent: hexane, 0.5 to 3% by weight
A foamable slurry S formed by mixing water and inevitable impurities: a kneaded product containing the remainder is formed into a sheet shape using the green sheet manufacturing apparatus 20 shown in FIG. 2, and is foamed and dried.

The green sheet manufacturing apparatus 20 peels from the carrier sheet 24 the foamed and dried material obtained by foaming and drying the slurry S applied to the surface of the carrier sheet 24 advanced by the rotating roller 22 to a uniform thickness using the doctor blade 26. By doing this, the green sheet G is continuously produced.
The foamable slurry S stored in the hopper 28 is supplied onto the advancing carrier sheet 24 and formed into a sheet with a predetermined thickness by a doctor blade 26 disposed at a predetermined height from the surface of the carrier sheet 24. Is done. The molded foamable slurry S is further conveyed by the carrier sheet 24 and sequentially passes through the foaming tank 30 and the heating tank 32. In the foaming tank 30 under a high humidity atmosphere (for example, humidity 75 to 95%, temperature 30 to 40 ° C., treatment time 10 to 20 minutes), the foamable slurry S is foamed without being dried. Next, the foamable slurry S in a foamed state is dried in the heating tank 32 (for example, 50 to 70 ° C., treatment time 50 to 70 minutes), whereby the metal powder is bonded by the binder and the pores are formed. Sheet G is manufactured.

  The green sheet G manufactured in this way is cut into a predetermined size and placed on the separator plate 12 (FIG. 1A), whereby the metal slurry layer 16 is formed on the separator plate 12. The separator plate 12 is made of the same stainless steel (SUS316L) as the metal powder of the foamable slurry S, and is a flat plate having a thickness of 0.15 mm.

<Slit formation process>
Next, slits 16a are formed in the metal slurry layer 16 formed on the separator plate 12, and a plurality of small pieces 16b are formed (FIG. 1B). The slit 16a is formed by cutting the metal slurry layer 16 with a cutter or the like.

<Baking process>
Next, the metal slurry layer 16 (each piece 16b) in which the slit 16a is formed is degreased (removing the binder) under predetermined degreasing conditions (for example, 450 to 650 ° C. in a vacuum, 25 to 35 minutes), and Firing is performed under predetermined firing conditions (for example, 1200 to 1300 ° C. and 50 to 70 minutes in a vacuum). By this firing treatment, the metal slurry layer 16 (each piece 16b) becomes a thin plate-like porous metal material. In this firing step, the porous metal material is arbitrarily uniformed by firing the separator plate 12 and the metal slurry layer 16 in a state of being sandwiched between the arranged flat compression members and pressed to an arbitrary thickness. The thickness of the porous metal material can be flattened, and the thickness of the porous metal material can be flattened. As the flat compression member, for example, a carbon plate sprayed with an oxide or a zirconia plate can be used.

  The porous metal material obtained by firing the metal slurry layer 16 has a porosity of 50 to 97%, a pore diameter of 10 μm to 2 mm, and pores that are open on the surface of the porous metal material are formed inside. Communicated with the pores.

  The metal slurry layer 16 shrinks as the binder is removed and the metal powder is sintered by being degreased and fired. Due to the shrinkage of the metal slurry layer 16, as shown in FIG. 1C, the slit 16 a is enlarged, and the flow path 15 including the enlarged slit 16 a is formed so as to extend between the small pieces 16 b in the surface direction. In addition, the slit 16a is formed in the metal slurry layer 16, and the metal slurry layer 16 (porous metal material) is prevented from cracking due to shrinkage by being divided into a plurality of small pieces 16b and firing.

  In addition, the fluid can be efficiently supplied to the entire gas diffusion layer 14 by setting the width of the flow path 15 to 3 mm or less. The width of the flow path 15 can be set to an arbitrary size by adjusting the shrinkage rate during firing of the metal slurry layer 16 and the formation width of the slit 16a. Moreover, the small piece 16b is diffusion-bonded to the separator plate 12 during the firing process.

  In this way, the plurality of small pieces 16 b and the flow path 15 formed on the surface 12 a of the separator plate 12 constitute a gas diffusion layer 14 in the fuel cell separator 10. A fuel cell 40 using the fuel cell separator 10 is shown in FIG. In this fuel cell 40, each fuel cell separator 10 is disposed so that the gas diffusion layer 14 is brought into contact with the catalyst layers 42 provided on both surfaces of the solid polymer membrane 41. In this fuel cell 40, by supplying fuel (hydrogen) to one gas diffusion layer 14 and air to the other gas diffusion layer 14, an electrochemical reaction is caused in each catalyst layer 42 to generate electric power. it can.

  The gas diffusion layer 14 of the fuel cell separator 10 includes a plurality of small pieces 16b made of a metal porous material, and a flow path 15 between the small pieces 16b. Therefore, the hydrogen or air supplied to the gas diffusion layer 14 quickly circulates through the entire gas diffusion layer 14 through the flow path 15, and further flows through the pores of the small pieces 16 b from the flow path 15 to each catalyst. The entire surface of the layer 42 can be uniformly reached.

  As described above, since the gas diffusion layer 14 has good flowability and fluid can be smoothly circulated even if the thickness is small, the fuel cell separator 10 can be made thin without deteriorating the power generation efficiency. The fuel cell in which the cells are stacked can be made thinner. Further, surplus hydrogen can be discharged from the gas diffusion layer 14 on the hydrogen supply side and water generated by the reaction on the air supply side. Therefore, the fuel cell 40 using the fuel cell separator 10 is excellent in hydrogen supply efficiency and prevents flooding due to water retention, so that efficient power generation is possible. Furthermore, since the gas diffusion layer 14 has good flowability, the pressure loss is small, so that the capacity of the pump for supplying hydrogen can be small, and the battery can be highly efficient and the apparatus can be downsized.

  Further, in the fuel cell separator 10, since the gas diffusion layer 14 and the separator plate 12 are joined by diffusion bonding, there is no contact resistance between the gas diffusion layer 14 and the separator plate 12. Therefore, the electrical resistance from the catalyst layer 42 to the separator plate 12 is small, and even when a large number of single cells are stacked, the power loss can be kept small.

As explained above, according to the fuel cell separator 10 of the present invention, a highly efficient and small fuel cell can be realized.
In addition, this invention is not limited to the thing of the structure of the said embodiment, In a detailed structure, it is possible to add a various change in the range which does not deviate from the meaning of this invention.

  For example, although the gas diffusion layer 14 is provided on the entire surface of the separator plate 12 in the above embodiment, the gas diffusion layer 54 may be provided on a part of the separator plate 52 as in the fuel cell separator 50 shown in FIG. . In this case, an inlet hole 52a through which the fluid supplied to the gas diffusion layer 54 circulates and an outlet hole 52b through which the fluid discharged from the gas diffusion layer 54 circulates are formed in the separator plate 52, and these inlet holes 52a and outlet holes 52b and the gas A sealing material 56 surrounding the diffusion layer 54 is provided. Thus, in the cell stack in which the fuel cell separators 50 are stacked, a fluid supply channel that connects the inlet holes 52a of the separator plates 52 and a fluid discharge channel that connects the outlet holes 52b are provided. be able to.

  In the fuel cell separator according to the present invention, the flow path of the gas diffusion layer can be provided in various shapes in order to improve drainage and adjust the residence time of the fluid in the gas diffusion layer. In the present invention, since the shape of the flow path is substantially the same as the shape of the slit, it is possible to form a flow path having an arbitrary shape simply by making the slit formed in the slit forming step an arbitrary shape.

For example, in the fuel cell separator 10 in which the flow paths 16b are provided in the lattice shape shown in FIG. 1C, the fluid can be circulated uniformly throughout the gas diffusion layer.
As shown in FIG. 5, in the fuel cell separator 60 in which the flow paths 65 are provided in a horizontal stripe shape, the diffusibility of the fluid in the lateral direction in the gas diffusion layer 64 can be improved. As shown in FIG. 6, in the fuel cell separator 70 in which the flow paths 75 are provided in the form of vertical stripes, drainage performance in the gas diffusion layer 74 can be improved.

As shown in FIG. 7, in the fuel cell separator 80 provided with the flow path 85 in a wavy line, and in the fuel cell separator 90 provided with the flow paths 95 extending alternately as shown in FIG. The residence time of the fluid in the inside can be lengthened.
As shown in FIG. 9, in the fuel cell separator 100 in which the density of the flow path 105 is partially different, the drainage performance can be increased as the density of the flow path 105 is higher in the gas diffusion layer 104.

  In the production method of the present invention, the metal slurry layer is not limited to the doctor blade method, but can be directly formed on the separator plate by an intermittent application method such as screen printing or a die coater method. Further, pattern application by screen printing or the like may be used. In these cases, after the metal slurry layer is foamed and dried on the separator plate, the slit forming step can be performed as it is. In addition, slits can be formed during pattern application.

Moreover, although the flat separator plate 12 is used in the embodiment, a roll separator plate may be used. In this case, the metal slurry layer can be continuously formed by a doctor blade method.
Moreover, the formation method of a slit is not limited to the method of cut | disconnecting the apply | coated metal slurry layer with a cutter, For example, the method of scraping a metal slurry layer in a linear form etc. may be sufficient.

  In the fuel cell separator of the present invention, the metal slurry layer may not have pores formed by a foaming agent as in the above embodiment. For example, a slurry containing a metal powder, a binder, and resin beads, and forming pores by erasing the resin beads by a firing process to form a porous metal material may be used.

  In the separator for a fuel cell of the present invention, the metal constituting the gas diffusion layer piece and the separator plate is not limited to SUS316SL, but is corrosion resistant alloy such as Ni—Cr—Mo alloy, and corrosion resistance such as titanium, niobium, and tantalum. A metal is preferred.

10, 50, 60, 70, 80, 90, 100 Separator for fuel cell 12, 52 Separator plate 14, 54, 64, 74, 84, 94, 104 Gas diffusion layer 15, 65, 75, 85, 95, 105 flow Path 16 Metal slurry layer 16a Slit 16b Small piece 20 Green sheet manufacturing device 22 Roller 24 Carrier sheet 26 Doctor blade 28 Hopper 30 Foaming tank 32 Heating tank 40 Fuel cell 41 Solid polymer film 42 Catalyst layer 52a Inlet hole 52b Outlet hole 56 Sealing material G Green sheet S Effervescent slurry

Claims (5)

A metal slurry layer forming step of forming a metal slurry layer containing a metal powder and a binder on the surface of a separator plate made of a metal flat plate;
Forming a slit in the metal slurry layer on the separator plate, and forming a plurality of small pieces; and
Gas diffusion in which the metal slurry layer is fired to form a metal porous material while shrinking the small pieces, and the slits are enlarged by the shrinkage, and a flow path including the enlarged slits is disposed between the small pieces. A method for producing a separator for a fuel cell, comprising a firing step for forming a layer.   The method of manufacturing a fuel cell separator according to claim 1, wherein the slit is formed by cutting the metal slurry layer. The metal slurry layer further includes a foaming agent,
The method for manufacturing a fuel cell separator according to claim 1 or 2, further comprising a foaming step of foaming the metal slurry layer before the slit forming step.   The method for producing a fuel cell separator according to any one of claims 1 to 3, wherein the separator plate and the metal porous material are made of the same metal material.   The method for producing a fuel cell separator according to any one of claims 1 to 4, wherein the metal porous material is made of a corrosion-resistant metal.

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