JP2004265856A - Solid polymer fuel cell separator, its manufacturing method, manufacturing device for same, and solid polymer fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a separator for a solid polymer fuel cell with a low cost and high durability, which is capable of improving the characteristics of the cell by reducing a contact resistance thereof by increasing a contact area of an indented part with an electrode. <P>SOLUTION: The separator for a solid polymer fuel cell has a flat part at a peripheral part, and indented parts serving as gas passages at the part excluding the flat part. An angle between a vertical wall part of the indentation and a horizontal part is 100° or less, and the contact area with the electrode is 30% or more of a projected area of an electrode part forming the gas flow passage. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

  The present invention relates to a separator used in a polymer electrolyte fuel cell used in an automobile, a small-scale power generation system and the like using electric power as a drive source, a manufacturing apparatus, a manufacturing method thereof, and a polymer electrolyte fuel cell using the separator About.

  Due to the growing awareness of environmental conservation, the transition from current internal combustion engines using fossil fuels to electrically driven vehicles using solid polymer fuel cells using hydrogen and distributed cogeneration systems is being studied worldwide. Yes. In order to make these new technologies widely available to the general public, it is necessary to promote technological development related to cost reduction and high reliability, including fuel supply systems.

In recent years, the development of fuel cells for electric vehicles has begun to progress rapidly with the successful development of solid polymer materials.
Unlike conventional alkaline fuel cells, phosphoric acid fuel cells, molten carbonate fuel cells, solid electrolyte fuel cells, etc., solid polymer fuel cells use a hydrogen ion permselective organic membrane as the electrolyte. In addition to pure hydrogen, the fuel cell uses hydrogen gas, etc. obtained by reforming alcohol, and takes out electric power by electrochemically controlling the reaction with oxygen in the air. System. Solid polymer membranes function well even if they are thin, and the electrolyte is fixed in the membrane, so it functions as an electrolyte if the dew point in the battery is controlled, so fluidity such as aqueous electrolytes and molten salt electrolytes Another characteristic is that the battery itself can be designed in a compact and simplified manner.

The polymer electrolyte fuel cell is actually a single cell with a sandwich structure consisting of a separator having a hydrogen flow path, a fuel electrode, a solid polymer membrane, an air (oxygen) electrode, and a separator having an air (oxygen) flow path. A stack in which the single cells are stacked is used. Therefore, both surfaces of the separator have independent flow paths, one side being hydrogen and the other side being a flow path of air and generated water.
As a constituent material of a polymer electrolyte fuel cell that operates in the region below the boiling point of the cooling aqueous solution, the temperature is not so high, and it is possible to sufficiently exhibit corrosion resistance and durability in that environment, Furthermore, carbon-based materials have been used by cutting to form an arbitrary flow path shape, but stainless steel and titanium have been used with the aim of reducing costs and downsizing, that is, reducing the thickness of separators. Technological development related to the application of

Conventionally, as stainless steel for fuel cells, for example, as disclosed in Patent Document 1, there is stainless steel for fuel cells that operates in a molten carbonate environment where high corrosion resistance is required.
Further, as disclosed in Patent Document 2 and the like, the invention of stainless steel for solid oxide fuel cells that operates at a high temperature of several hundred degrees has been made.
Further, in Patent Document 3, for the purpose of obtaining a separator for a fuel cell having a low contact resistance with an electrode of a unit cell, an inner peripheral portion is formed by stretching (also referred to as press molding) stainless steel (SUS304). And a bulge-molded portion comprising a large number of irregularities is formed, and a gold plating layer having a thickness of 0.01 to 0.02 μm is formed on the bulge tip side end surface of the bulge-molded portion. A separator is disclosed, and when a fuel cell is formed, a separator for a fuel cell is interposed between stacked unit cells, and is formed on an end surface of a bulging tip of a unit cell electrode and a bulging molded portion. In addition, a technique is disclosed in which a reaction gas passage is defined between a fuel cell separator and an electrode so as to be in contact with the gold plating layer.
Moreover, in patent document 4, in order to process cheaply, the corrugated perforated bipolar plate which was press-processed is disclosed.
JP-A-4-247852 JP-A-6-264193 JP-A-10-228914 JP-A-5-29909

Stainless steel with an increased alloy composition such as Cr, Ni, and Mo to improve long-term reliability has a lower workability than SUS304, so it is difficult to press-mold into a corrugated shape. In addition, when the cross section is corrugated, the contact area with the electrolyte membrane is reduced and the fuel cell characteristics are deteriorated.
The present invention provides a polymer electrolyte fuel by increasing the contact area between the convex part and the concave part and the electrode and reducing the contact resistance with respect to the solid polymer fuel cell separator described above without breaking during molding. It aims at improving the battery characteristic of a battery.

In order to solve the above-mentioned problems, the present invention has been completed as a result of detailed examination through various mold shapes, analysis of molding conditions, and trial production. The gist of the present invention is as follows.
(1) It has a flat part in the periphery, and the part excluding the periphery has a convex part and a concave part to be a gas flow path, and the angle formed by the vertical wall part and the horizontal part of the convex part and the concave part is 80 ° to 100 °. A solid polymer fuel cell separator, wherein a contact area between a horizontal portion and an electrode in a convex portion or a concave portion is 30 to 50% of a projected area of the concave and convex portion on the electrode.
(2) The solid polymer fuel cell separator according to (1), wherein the material is made of stainless steel or titanium.
(3) In the apparatus for manufacturing a polymer electrolyte fuel cell separator, which has a flat portion around the periphery, and a portion excluding the periphery has a convex portion and a concave portion that serve as a gas flow path, the clearance c ( mm), shoulder r (mm), groove depth d (mm), and groove period p (mm) satisfy the equations (1) to (4), respectively. manufacturing device.
1.1 <c / t <1.6 (1)
2 <r / t <5 (2)
2 <d / t <8 (3)
2 <p / t <24 (4)
Where t: plate thickness of workpiece (mm)
(4) The solid according to (1) or (2), wherein the manufacturing apparatus according to (3) is used for coining to a thickness of 0.5 to 1.0 times the original thickness of the workpiece. A method for producing a polymer fuel cell separator.
(5) The method for producing a separator for a polymer electrolyte fuel cell according to (4), wherein a mineral oil lubricant or a solid lubricant is applied to a workpiece and coining is performed.
(6) A polymer electrolyte fuel cell comprising the polymer electrolyte fuel cell separator according to (1) or (2).

  INDUSTRIAL APPLICABILITY According to the present invention, it is extremely effective as a technique for improving the cell characteristics of a solid polymer fuel cell by increasing the contact area between the convex and concave portions of the solid polymer fuel cell separator and the electrode and reducing the contact resistance. Is.

Details of the present invention will be described below.
An example of a cross-sectional view of a separator for a polymer electrolyte fuel cell according to the present invention is shown in FIG.
In the solid polymer fuel cell separator 1 having a flat portion around the periphery, and a portion excluding the periphery having a convex portion and a concave portion serving as a gas flow path, the vertical wall portion 3 of the convex portion and the concave portion. The angle α formed by the horizontal portion 2 is 100 ° or less, and the contact area between the horizontal portion 2 and the electrode (16 in FIG. 3 described later) in the convex portion or the concave portion is 30 of the projected area of the concave and convex portion on the electrode. It has been found that by satisfying% or more, the contact area between the projections and depressions of the separator and the electrode can be increased, and the cell characteristics of the polymer electrolyte fuel cell can be improved.

  On the other hand, if the angle α formed by the vertical wall portion 3 and the horizontal portion 2 of the concavo-convex portion is less than 80 °, the workpiece is broken during molding, so the angle α is defined as 80 ° or more. Further, when the contact area between the horizontal part 2 and the electrode in the convex part or the concave part exceeds 50% of the projected area of the concave and convex part on the electrode, the chemical reaction is promoted to obtain a predetermined electromotive force, and the fuel gas flows over the entire electrode surface Therefore, it is defined as 50% or less.

FIG. 2 shows a sectional view of the mold of the manufacturing apparatus according to the present invention. The concave and convex shoulders r (12, 13), the groove depth d (10, 11), and the groove period p (8, 9) of the upper mold 6 and the lower mold 7 forming a pair of upper and lower sides are equal. When the thickness of the workpiece is t (mm), the vertical wall clearance c (14), shoulder r, groove depth d, and groove period p of the concave and convex portions of the upper and lower molds are (1 ) To (4), the separator can be molded without breakage.
1.1 <c / t <1.6 (1)
2 <r / t <5 (2)
2 <d / t <8 (3)
2 <p / t <24 (4)
If the combination is outside the above range, it is extremely difficult to form the vertical wall portion at an angle of 100 ° or less without causing the work material (stainless steel or titanium) to crack or break.

By using the mold having the concavo-convex shape to coining the workpiece plate thickness to 1.0 times or less of the original thickness, (1) or (2) according to the present invention, The polymer electrolyte fuel cell separator 1 having no defective parts such as cracks and fractures can be formed. On the other hand, cracking is likely to occur when the workpiece thickness is coined to less than 0.5 times the original thickness, so the thickness of the workpiece is set to 0.5 times or more the original thickness.
Also, by applying a mineral lubricant or solid lubricant such as molybdenum disulfide to the work material and reducing the frictional force on the work surface, cracks and fractures can be reduced, and the vertical wall during coining The angle of the vertical wall can be increased due to the material flowing into the part. As a mineral oil-based lubricant, a general metal processing lubricant, rust preventive oil, or the like can be used. As an example of the lubricant, Idemitsu Kosan Co., Ltd., product name: Daphne Oil Coat Z-3 can be mentioned.
By using the polymer electrolyte fuel cell separator according to the present invention for a polymer electrolyte fuel cell, a lightweight, highly efficient and highly reliable fuel cell can be obtained.

  The vertical wall clearance c (14) = 0.12 mm, the shoulder r (12,13) = 0.25 mm, and the groove depth d (10,11) = 0 based on the workpiece thickness 0.1 mm. A mold having a thickness of 0.5 mm, a groove period p (8,9) = 2.0 mm, a separator size of 150 mm × 250 mm, and an unevenness size of 100 mm × 200 mm was manufactured. The materials of the molds 6 and 7 were SKD11, and the workpiece was austenitic stainless steel SUS316.

By setting the groove depth d (10, 11) of the molds 6 and 7 to 0.5 mm and performing coining processing by 0.55 mm, which is 0.5 times the original thickness of the workpiece, convex portions and concave portions are formed. The angle α formed by the vertical wall portion and the horizontal portion of the cross section of the gas flow path having the repeated structure is 85 °, and the contact area between the horizontal portion of the concave portion or convex portion and the electrode is the projected area of the concave and convex portion on the electrode Solid polymer fuel cell separators 1 of 40% each were formed. In the production of the polymer electrolyte fuel cell separator according to the present invention, even when a total of 500 sheets were produced, the probability of occurrence of cracks and breaks was 0.8% or less.
In addition, under the same conditions as described above, by applying a general rust preventive oil using a petroleum-based hydrocarbon of a mineral oil-based lubricant as a lubricating base oil to the uneven surface of the concavo-convex portion with a brush, The probability of occurrence was improved to 0.4% or less.

  Thereafter, the separator surface was subjected to metal plating treatment, and then, as shown in FIG. 3, an acid-resistant rubber seal plate 15, an electrode 16 made of a carbon fiber current collector, a fluororesin solid, as shown in FIG. A fuel cell stack consisting of a multilayer in which a B cycle including a cooling water flow path is laminated at a rate of once every four times on an A cycle with the polymer membrane 17, the electrode 16 and the seal plate 15 sandwiched therebetween is tested. As a result, it was confirmed that neither gas leakage nor water leakage occurred even when the operation was performed for a total of 5000 hours, and that the fuel cell functioned well using the separator manufactured by the manufacturing apparatus of the present invention.

It is an example of sectional drawing of the separator manufactured by this invention. It is a schematic diagram which shows the example of metal mold | die cross-sectional shape among this invention. It is the schematic diagram which showed an example which builds a polymer electrolyte fuel cell stack using the separator manufactured by this invention.

Explanation of symbols

1: Separator 2: Horizontal part 3: Vertical wall part 4: Groove depth 5: Groove period 6: Upper mold 7: Lower mold 8: Groove period (upper mold)
9: Groove period (lower mold) 10: Groove depth (upper mold)
11: Groove depth (lower mold) 12: Shoulder (upper mold)
13: Shoulder (lower mold) 14: Vertical wall clearance 15: Seal plate 16: Electrode (carbon fiber current collector)
17: Solid polymer film α: Angle between vertical wall and horizontal

Claims (6)

The periphery has a flat part, and the part other than the periphery has a convex part and a concave part that serve as a gas flow path, and the angle formed by the vertical wall part and the horizontal part of the convex part and the concave part is 80 ° to 100 °. A separator for a polymer electrolyte fuel cell, wherein a contact area between a horizontal portion and an electrode in a portion or a recess is 30 to 50% of a projected area of an uneven portion on the electrode. 2. The polymer electrolyte fuel cell separator according to claim 1, wherein the material is made of stainless steel or titanium. In the apparatus for manufacturing a polymer electrolyte fuel cell separator having a flat portion at the periphery and a portion excluding the periphery having a convex portion and a concave portion that serve as a gas flow path, the clearance c (mm) of the vertical wall portion of the concave and convex portion, Production of a separator for a polymer electrolyte fuel cell, wherein the shoulder radius r (mm), groove depth d (mm), and groove period p (mm) satisfy the equations (1) to (4), respectively. apparatus.
1.1 <c / t <1.6 (1)
2 <r / t <5 (2)
2 <d / t <8 (3)
2 <p / t <24 (4)
Where t: plate thickness of workpiece (mm) The solid polymer fuel cell according to claim 1 or 2, wherein the manufacturing apparatus according to claim 3 is used for coining to a plate thickness of a workpiece of 0.5 to 1.0 times the original thickness. Manufacturing method for the separator. 5. The method for producing a separator for a polymer electrolyte fuel cell according to claim 4, wherein the workpiece is coated with a mineral oil lubricant or a solid lubricant and coined. 3. A polymer electrolyte fuel cell using the polymer electrolyte fuel cell separator according to claim 1.

Images