JP2006344432A - Separator, fuel cell, fuel cell stack, manufacturing method of separator, and manufacturing method of separator assembly - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a cost by cutting down an amount of gold used while maintaining good adhesion of gold to a separator base material. <P>SOLUTION: A first coat layer 12 comprising a mixed material made by adding gold to a bedding material having conductivity and suppressing diffusion of gold is formed on the surface of a metallic separator base material 10, and gold plating is applied on the first coat layer 12 to form a second coat layer 13 comprising gold. An electrode is brought into contact with a coat layer 11 composed of the first coat layer 12 and the second coat layer 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a separator for a fuel cell, a fuel cell including the separator, a fuel cell stack in which a plurality of the fuel cells are stacked, a method for manufacturing the separator, and a separator assembly in which a pair of separators are stacked. Regarding the method.

  For example, a polymer electrolyte fuel cell includes an electrolyte membrane and a MEA (Membrane Electrode Assembly) composed of a pair of electrodes disposed on both sides thereof, and a pair of separators sandwiching the MEA, and is in a laminated form as a whole. .

  As a separator constituting this type of fuel cell, a main metal layer containing gold is formed on the surface of a separator base material made of aluminum via a base metal layer containing nickel, and the main metal layer is uniformly formed by base molding. It is known to improve adhesion and reduce the amount of expensive metal materials such as gold in the main metal layer (see, for example, Patent Document 1).

A separator is also known in which only the gold plating layer in contact with the electrode is formed thick to reduce the amount of expensive metal material used (see, for example, Patent Document 2).
JP 2003-123782 A JP 2001-345109 A

  According to the above technique, it is possible to improve the adhesion of gold to the separator substrate and reduce the amount of use to some extent, but from the demand for further cost reduction, the gold adhesion to the separator substrate is improved. There is a need to further reduce the amount of expensive gold used while maintaining it.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the amount of gold used while maintaining good adhesion of gold to a separator substrate, and to reduce costs.

  In order to achieve the above object, the separator of the present invention is a separator in which a fluid flow path is formed, and includes a metal separator base material and a coating layer formed on the separator base material. The coating layer includes a first coating layer formed of a mixed material in which gold is added to a base material that has conductivity and suppresses diffusion of gold.

  According to this configuration, since the first coat layer made of a mixed material in which gold is added to the base material is provided, by applying gold plating to the first coat layer, the adhesion of the gold plating can be improved, and from the gold plating Gold diffusion to the separator substrate side is suppressed. As a result, the gold plating can be made thin, the amount of expensive gold used can be greatly reduced, and the cost can be reduced.

  Further, if the amount of gold added to the base material is increased, good conductivity with the electrode can be ensured with only the first coat layer without performing gold plating on the first coat layer.

  The coat layer is preferably formed with a second coat layer made of gold on the first coat layer.

  It is preferable that the coat layer is formed only at a planned contact point with the electrode.

  A fuel cell according to the present invention includes the separator described above.

  According to this configuration, the amount of expensive gold used is greatly reduced, so that the cost can be reduced.

  The fuel cell stack according to the present invention is a fuel cell stack in which a plurality of the fuel cells are stacked, and the back surfaces of the adjacent separator base materials are brazed and joined.

  According to this configuration, the adhesion between the separators and the conductivity can be improved. As a result, the use of gold applied to improve the adhesion and conductivity on the back surface side of the separator substrate is eliminated or the amount used is reduced. And cost reduction can be achieved.

  The separator manufacturing method of the present invention is a separator manufacturing method in which a fluid flow path is formed, and is used as a base material having conductivity and suppressing gold diffusion on the surface of a metal separator substrate. Forming a coating layer having a first coating layer made of a mixed material to which gold is added;

  According to this method, since the coat layer having the first coat layer made of the mixed material obtained by adding gold to the base material is formed, the gold plating adhesion is improved by applying the gold plating to the first coat layer. The diffusion of gold from the gold plating to the separator base is suppressed. As a result, the gold plating can be made thin, the amount of expensive gold used can be greatly reduced, and the cost can be reduced.

  Further, if the amount of gold added to the base material is increased, good conductivity with the electrode can be ensured with only the first coat layer without performing gold plating on the first coat layer.

  The coat layer forming step preferably includes a step of forming a second coat layer made of gold on the first coat layer.

  In the coat layer forming step, it is desirable that the coat layer is formed only at a place where the separator base material is to come into contact with the electrode.

  The method for producing a separator assembly according to the present invention is a method for producing a separator assembly in which a pair of the above separators are joined, and a brazing material for applying a brazing material to the back surface of the separator substrate on which the coating layer is formed. It includes a coating step and a joining step of brazing and joining the back surfaces of the pair of separator bases with the brazing material.

  According to this configuration, the adhesion between the separators and the conductivity can be improved. As a result, the use of gold applied to improve the adhesion and conductivity on the back surface side of the separator substrate is eliminated or the amount used is reduced. And cost reduction can be achieved.

  According to the present invention, the gold adhesion to the separator base material can be improved and the gold diffusion to the separator base material side can be suppressed, so that the amount of expensive gold used can be greatly reduced and the cost can be reduced. Reduction can be achieved.

  Hereinafter, embodiments of a separator and a manufacturing method thereof according to the present invention will be described with reference to the drawings.

(Separator)
First, the structure of the separator according to the present invention will be described.

(First embodiment)
FIG. 1 is a perspective view showing a separator constituting a fuel cell, and FIG. 2 is a cross-sectional view of the separator according to the first embodiment.

  As shown in FIG. 1, a separator 1 constituting a solid polymer fuel cell is press-molded to form a plurality of convex portions 2 and concave portions 3 on the front and back surfaces, and the plurality of convex portions 2 and concave portions. Each 3 extends in one direction.

  The separator 1 is provided with an MEA comprising an electrolyte membrane and a pair of electrodes disposed on both sides of the separator 1, and the recess 3 communicates with a manifold 4 formed on one end of the separator 1. A gas flow path through which gas (for example, air) or fuel gas (for example, hydrogen) flows is used.

  The separator 1 is laminated and integrated with a separator 1 constituting another adjacent fuel cell, and the portion surrounded by the concave portion 3 on the back surface side of the convex portion 2 of each separator 1 is filled with cooling water. A cooling flow path is provided.

  As shown in FIG. 2, the separator 1 has a separator substrate 10 formed of, for example, aluminum, carbon steel, stainless steel, or the like. The separator substrate 10 has a coat layer 11 on its surface. The coat layer 11 includes a first coat layer 12 and a second coat layer 13, and the second coat layer 13 is formed via the first coat layer 12.

  For example, the first coat layer 12 is formed of a mixed material in which gold is added to a base material that has conductivity such as carbon or nickel and suppresses diffusion of gold. The first coat layer 12 is formed by coating the separator base material 10 when carbon is used as a base material, and is formed by plating the separator base material 10 when nickel is used. . Further, gold added to the base material is appropriately added at a ratio of 50% or less, for example.

  The second coat layer 13 formed on the first coat layer 12 is made of gold, and is formed by applying gold plating to the first coat layer 12. Thus, in the separator 1 in which the first coat layer 12 and the second coat layer 13 are formed in this way, MEA is laminated on the convex portion 2 on the front surface side (gas flow path surface side), while the back surface side ( The rear surface side (cooling channel surface side) of the separator 1 of another fuel cell is joined to the convex portion 2 on the cooling channel surface side.

  According to the separator 1 having the above-described structure, the second coat layer 13 made of gold plating is formed through the first coat layer 12 made of a mixed material in which gold is added to the base material. The adhesion of the layer 13 is enhanced, and the diffusion of gold from the second coat layer 13 to the first coat layer 12 and the separator substrate 10 is suppressed.

  Thereby, the 2nd coating layer 13 which consists of gold plating can be made thin, the usage-amount of expensive gold | metal | money can be reduced significantly, and cost reduction can be aimed at.

(Second Embodiment)
FIG. 3 is a cross-sectional view of the separator according to the second embodiment. Hereinafter, the same components as those in the above embodiment are denoted by the same reference numerals and the description thereof will be omitted, and differences in configuration and effect from the above embodiment will be mainly described.

  As shown in FIG. 3, in the separator 1, only the first coat layer 21 is formed on the separator substrate 10. The first coat layer 21 is formed of a mixed material in which gold is added to a base material that has conductivity such as carbon or nickel and suppresses the diffusion of gold.

  Here, the amount of gold added to the base material of the first coat layer 21 is larger than that in the first embodiment, and is appropriately added at a ratio of, for example, 50% or less.

  According to the separator 1 having the above-described structure, the first coat layer 21 made of a mixed material in which a considerable amount of gold is added to the base material is formed, and the MEA is brought into contact with the first coat layer 21. Since gold plating for improving conductivity as in the second coat layer 13 in one embodiment is not required, the amount of expensive gold used can be greatly reduced, and the cost can be reduced.

(Third embodiment)
FIG. 4 is a cross-sectional view of the separator according to the third embodiment. Hereinafter, the same components as those in the above embodiment are denoted by the same reference numerals and the description thereof will be omitted, and differences in configuration and effect from the above embodiment will be mainly described.

  As shown in FIG. 4, the separator 1 is obtained by forming the first coat layer 12 and the second coat layer 13 similar to those of the first embodiment only on the surface of the convex portion 12. In other words, in this separator 1, only the surface of the convex portion 12 that is a contact point with the MEA 31 and another contact point 1 has conductivity such as carbon or nickel and suppresses gold diffusion. For example, a first coat layer 12 made of a mixed material in which 50% or less of gold is added to the material is formed, and a second coat layer 13 is formed on the first coat layer 12 by performing gold plating.

  Thus, the first coating layer 12 and the first coating layer 12 on the inner surface of the cooling channel 33 formed by the gas channel 32 formed by the MEA 31 and the recess 3 of the separator 1 and the recess 3 on the back surface side of the separator 1 abutted with each other. The two-coat layer 13 is eliminated.

  And according to this separator 1, while forming the 2nd coat layer 13 which consists of gold plating via the 1st coat layer 12 which consists of a mixed material which added gold to a ground material, it is the 1st only in the part which needs conduction. Since the coat layer 12 and the second coat layer 13 are formed, the second coat layer 13 made of gold plating can be thinned by improving the adhesion of gold, and the area where gold is used can be reduced. Thereby, the usage-amount of expensive gold | metal | money can be reduced significantly and cost reduction can be aimed at.

  Further, since the first coat layer 12 and the second coat layer 13 on the inner surfaces of the gas flow path 32 and the cooling flow path 33 are eliminated, the cross-sectional areas of the gas flow path 32 and the cooling flow path 33 can be increased. In addition, it is possible to eliminate the change in the flow path area due to the thickness variation of the coat layers 12 and 13, and to improve the power generation efficiency and stabilize it.

  In this embodiment, the first coat layer 12 and the second coat layer 13 are formed only on the surface of the convex portion 2, but only the surface of the convex portion 2 as shown in the second embodiment, for example, Alternatively, the first coat layer 21 made of a mixed material in which gold is added at a ratio of 50% or less, for example, to a base material having conductivity such as carbon or nickel and suppressing the diffusion of gold may be formed.

(Separator assembly)
Next, the structure of the separator assembly according to the present invention will be described.

  FIG. 5 is a cross-sectional view showing a main part of a fuel cell stack formed by alternately laminating a plurality of separator assemblies and MEAs according to an embodiment of the present invention. Hereinafter, the same components as those in the above embodiment are denoted by the same reference numerals and the description thereof will be omitted, and differences in configuration and effect from the above embodiment will be mainly described.

  As shown in FIG. 5, each separator 1 of the separator assembly 40 formed by joining the surfaces (rear surfaces) of the cooling flow paths 33 of the pair of separators 1 is formed only on the surface side of the separator base material 10. 12 and the second coat layer 13 are formed. In these separators 1, the butted portions of the protrusions 2 of the separator base material 10 adjacent to each other are joined by a brazing material 41.

  Thus, according to this separator joined body 40, the second coat layer 13 made of gold plating is formed via the first coat layer 12 made of a mixed material in which gold is added to the base material, and the separators that are abutted against each other. Since the base materials 10 are joined to each other by the brazing material 41, the adhesion of the second coat layer 13 to the separator base material 10 is improved, and the second coat layer 13 made of gold plating can be made thin. It is possible to eliminate the use of gold applied to improve the adhesion to the back side of the metal, and to significantly reduce the amount of expensive gold used, thereby reducing the cost.

  Further, since the first coat layer 12 and the second coat layer 13 on the inner surfaces of the gas flow path 32 and the cooling flow path 33 are eliminated, the cross-sectional areas of the gas flow path 32 and the cooling flow path 33 can be increased. At the same time, it is possible to eliminate the change in the flow path area due to the variation in the thickness of each coat layer, and it is possible to improve and stabilize the power generation efficiency.

  In the case of this embodiment as well, as shown in the second embodiment, for example, the base material having conductivity such as carbon or nickel and suppressing the diffusion of gold is, for example, 50% or less of gold. The first coat layer 21 made of a mixed material to which is added may be formed.

(Manufacturing method of separator)
Next, the manufacturing method of a separator is demonstrated along FIG. Here, a case where the first coat layer and the second coat layer are formed only on the surface of the separator and the adjacent separators are brazed will be described.

(1) Coat layer forming step First, as shown in FIG. 6B, for example, carbon or nickel or the like is formed on the surface of the separator base 10 made of a metal plate such as stainless steel as shown in FIG. The first coating layer 12 is formed by sputtering a mixed material added with gold on a base material that has conductivity and suppresses diffusion of gold. Next, as shown in FIG. 6C, the second coat layer 13 is formed on the upper surface of the first coat layer 12 by performing gold plating.

(2) Brazing material application process Once the first coat layer 12 and the second coat layer 13 are formed, as shown in FIG. 6 (d), the back surface of the separator substrate 10 is coated with, for example, plating, printing, or melt spraying. A brazing material 41 is applied.

(3) Pressing Step Next, as shown in FIG. 6E, the separator substrate 10 is pressed to form the convex portion 2, the concave portion 3, and the like.

(4) Joining Step After the separator base material 10 is molded as described above, the brazing material 41 is melted in a state where the back surfaces of the separator base materials 10 adjacent to each other are abutted with each other as shown in FIG. And then cooled and cured. In this way, the separator base materials 10 are joined to each other by the brazing material 41.

  In addition, as a brazing method of the separator base materials 10 by the brazing material 41, there exist the method by resistance heating, the heating by a high temperature furnace, or a high frequency heating, for example. Moreover, as atmosphere at the time of brazing, it is good to set it as air | atmosphere, vacuum, or active atmospheres, such as fuel gas and nitrogen gas, and it is preferable to apply | coat a flux to the joining surface of separator base materials 10. preferable.

  Then, if the separator base materials 10 are joined to each other by brazing as described above, the separator base materials 10 are so-called self-alignment effects due to the surface tension of the molten brazing material 41 at the time of joining. Therefore, the bonding area can be made wide and stable. In addition, when the separator base materials 10 are joined to each other, the contact resistance between the separator base materials 10 can be reduced as much as possible by pressurizing the separator base materials 10 to each other.

  In the above example, the case where the first coat layer 12 and the second coat layer 13 are formed on the separator base material 10 has been described as an example. However, for example, it has conductivity such as carbon or nickel and diffuses gold. Only the first coat layer 21 made of a mixed material in which gold is added to the base material to be suppressed at a ratio of several tens of percent (for example, 50% or less) may be formed. In this case, in the coating layer forming step, After forming one coat layer 21, the process proceeds to a brazing material coating process in which a brazing material 41 is coated on the back surface of the separator substrate 10.

  In the above example, the brazing material 41 is applied to the entire back surface of the separator base material 10, but the brazing material 41 may be applied only to the joining portion.

  In this case, after the coat layer forming step, as shown in FIG. 7A, the separator base material 10 is pressed to form the convex portions 2 and the concave portions 3, and then the step shown in FIG. ), A brazing material application process is performed in which the brazing material 41 is applied only to the convex portions 2 on the back surface of the separator substrate 10. Then, when the brazing material 41 is applied only to the convex portions 2 on the back surface in this manner, the brazing material 41 is melted in a state where the separator base materials 10 are abutted with each other, and then cooled and cured to join. (See FIG. 6F).

It is a perspective view which shows the separator which comprises a fuel cell. It is sectional drawing of the separator which concerns on 1st Embodiment. It is sectional drawing of the separator which concerns on 2nd Embodiment. It is sectional drawing of the separator which concerns on 3rd Embodiment. It is sectional drawing which shows the principal part of the fuel cell stack containing a separator assembly. It is a schematic process drawing explaining the manufacturing method of a separator. It is a schematic process drawing explaining the modification of the manufacturing method of a separator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Separator, 10 ... Separator base material, 11 ... Coat layer, 12, 21 ... 1st coat layer, 13 ... 2nd coat layer, 31 ... Electrode, 41 ... Brazing material

Claims (9)

A separator formed with a fluid flow path,
A metal separator base material, and a coat layer formed on the separator base material,
The said coating layer is provided with the 1st coating layer formed from the mixed material which added the gold | metal | money to the base material which has electroconductivity and suppresses spreading | diffusion of gold | metal | money, The separator characterized by the above-mentioned.   The separator according to claim 1, wherein the coat layer is formed by forming a second coat layer made of gold on the first coat layer.   The separator according to claim 1, wherein the coat layer is formed only at a place where the electrode is scheduled to contact.   A fuel cell comprising the separator according to claim 1. A fuel cell stack in which a plurality of the fuel cells according to claim 4 are stacked,
A fuel cell stack, wherein the back surfaces of the separator base materials adjacent to each other are brazed and joined. A separator manufacturing method in which a fluid flow path is formed,
Including a forming step of forming a coating layer having a first coating layer made of a mixed material obtained by adding gold to a base material having conductivity and suppressing gold diffusion on the surface of a metallic separator base material. A method for manufacturing a separator.   The method for manufacturing a separator according to claim 6, wherein the coat layer forming step includes a step of forming a second coat layer made of gold on the first coat layer.   The method for manufacturing a separator according to claim 6 or 7, wherein, in the coating layer forming step, the coating layer is formed only in a portion where the separator base material is expected to come into contact with an electrode. A method for producing a separator joined body in which a pair of separators according to claim 1 is joined,
A brazing material application step of applying a brazing material to the back surface of the separator substrate on which the coating layer is formed;
And a joining step of brazing and joining the back surfaces of the pair of separator base materials with the brazing material.

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