JP4451964B2 - Separator for polymer electrolyte fuel cell, gas channel spacer and polymer electrolyte fuel cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a polymer electrolyte fuel cell used for automobiles and small-scale power generation systems that use electric power as a direct drive source. More specifically, a polymer electrolyte fuel cell separator, a gas flow path spacer, and these are used. It relates to the polymer electrolyte fuel cell.
[0002]
[Prior art]
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 hydrogen ion permselective organic membranes as the electrolyte. The fuel cell is characterized by the fact that, in addition to pure hydrogen, hydrogen gas obtained by reforming alcohols is used as the fuel, and the reaction with oxygen in the air is controlled electrochemically. It is a system to take out.
[0003]
Solid polymer membranes function well even if they are thin, and the electrolyte is fixed in the membrane, so if you control the dew point in the battery, it functions as an electrolyte, 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.
[0004]
Conventionally, as stainless steel for fuel cells, JP-A-4-247852, JP-A-4-35844, JP-A-7-188870, JP-A-8-165546, JP-A-8-255892, and JP-A-8-311620, etc. As disclosed, there are fuel cell stainless steels operating in molten carbonate environments where high corrosion resistance is required.
Further, as disclosed in JP-A-6-264193, JP-A-6-293941, and JP-A-9-67672, inventions of solid oxide fuel cell materials that operate at a high temperature of several hundred degrees have been made. .
[0005]
On the other hand, 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 corrosion resistance and durability can be sufficiently exhibited in the environment. For some reasons, carbon-based materials have been used, but technological development related to the application of stainless steel and titanium is also progressing with the aim of reducing costs and miniaturization.
[0006]
In Japanese Patent Laid-Open No. 10-228914, for the purpose of obtaining a separator for a fuel cell having a small contact resistance with an electrode of a unit cell, a number of irregularities are formed on the inner peripheral portion by press-molding stainless steel (SUS304). Inventing a fuel cell separator, characterized in that a bulging molded part is formed, and a gold plating layer having a thickness of 0.01 to 0.02 μm is formed on the bulging tip side end face of the bulging molded part. As a method of using the fuel cell, a gold plating layer is formed between the unit cell electrodes and the bulging tip side end surface of the bulging molded portion by interposing the fuel cell separator between the stacked unit cells when forming the fuel cell. Has been disclosed in which a reaction gas passage is defined between a fuel cell separator and an electrode.
[0007]
However, it was found that there were the following three technical problems when a solid polymer fuel cell was prototyped based on this technology.
a) In an environment in a polymer electrolyte fuel cell that requires long-term durability, SUS304, which is a general-purpose steel grade, may be insufficient as an alloy component of a stainless steel separator. It is necessary to increase the content of
[0008]
b) In the case of stainless steel with an alloy composition such as Cr, Ni, Mo, etc., the passive oxide film of stainless steel is completely reduced during the plating process between the gold plating layer and the stainless steel substrate only by the wet gold plating method. It may remain without being generated, causing an interlayer resistance between the stainless steel and the gold plating layer, which may cause power loss. As a countermeasure, it is necessary to attach the noble metal while removing the film.
[0009]
c) The separator is assumed to have a shape in which a bulging formed part consisting of a large number of irregularities is formed on the inner peripheral part by press molding. Stainless steel with ductile cracks in the bulging formed part and a multi-stage process with low productivity as a countermeasure must be assembled, which does not necessarily lead to cost reduction, and further increases the alloy composition to improve long-term reliability Since steel is less workable than SUS304, it is difficult to press form into this shape.
[0010]
The inventors have already proposed means for solving the problems a) and b) in Japanese Patent Application No. 11-62813 and Japanese Patent Application No. 11-170142.
[0011]
[Problems to be solved by the invention]
In view of the above-mentioned problem c), the present invention is a solid polymer fuel made of stainless steel or titanium capable of simplifying the processing steps and realizing a production technology for a low-cost, high-durability solid polymer fuel cell. An object of the present invention is to provide a battery separator, a gas flow path spacer that can be applied to the battery separator, and a solid polymer fuel cell using these.
[0012]
[Means for Solving the Problems]
In order to solve the above-mentioned problems, the present invention has been intensively studied on a low-cost fuel cell structure system that can be mass-produced with a minimum of molding of stainless steel or titanium, based on the principle of operation of a polymer electrolyte fuel cell. As a summary, the following is the summary.
(1) A stainless steel solid polymer fuel cell separator comprising a flat portion having only a pair of opposite ends and a full-width corrugated plate portion formed by a gear roll therebetween.
(2) A titanium polymer electrolyte polymer fuel cell separator comprising a flat portion having only one pair at both ends and a full-width corrugated plate portion formed by a gear roll therebetween.
(3) The flat part of the stainless steel separator according to (1) or the titanium separator according to (2) has two or more holes serving as cooling water passages or gas passages. Solid polymer fuel cell separator.
(4) A gas flow path spacer that is used by being overlapped with the separator according to (3), and has a corrugated plate-like seal portion that can be fitted to the separator corrugated plate portion to ensure airtightness at a side end portion thereof. A gas flow path spacer characterized by that.
(5) A polymer electrolyte fuel cell comprising at least one of the separator according to (3) and the gas flow path spacer according to (4).
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Details will be described below with reference to the drawings.
FIG. 1 shows a specific shape example of the separator material described in (1) or (2). 1 is an example in which the corrugated plate has a cross-sectional shape of a sine wave W1, and 2 is an example in which it is a rectangular wave W2.
[0014]
Needless to say, the corrugated plate cross-sectional shape and the substrate dimensions are not limited to this drawing and should be variously selected as necessary. Such a shape can be easily and efficiently formed from a stainless steel or titanium thin plate or foil by a gear roll, and the processing mode is only bending. The elongation fracture phenomenon cannot occur.
[0015]
When designing a polymer electrolyte fuel cell structure using such a separator, the problems are the settings of the gas and cooling water flow paths to be supplied and discharged to the inside and outside, and the supplied gases and cooling water. It is how to realize a leak-proof seal to the outside. Therefore, the structure design method of the fuel cell stack using the above-described separator was devised. A specific example is shown in FIG.
[0016]
In the figure, reference numeral 3 denotes a separator formed by opening two holes h1, h2, h3 and h4 as gas flow paths in the flat portions described in (3). The function required for this separator is to separate the fuel gas containing hydrogen and the air gas containing oxygen so as not to mix inside the battery, and to conduct electricity to transmit the generated current to the adjacent cell.
In the figure, reference numeral 4 denotes the gas seal between the separator 3 and the solid polymer film 6 coated with the electrode catalyst 7 on both sides while gas is distributed to the electrode surface, as described in the above (4). It is a gas flow path spacer.
[0017]
The gas flow path spacer 4 is characterized in that a wave-like portion We is provided at a side end portion of the surface in contact with the separator 3, thereby ensuring gas sealing performance. The gas flow path spacer shape is the key to the use of the folding-type substrate of the present invention as a fuel cell separator.
[0018]
The central portion of the gas flow path spacer 4 is hollowed out so that the current generated in the electrode catalyst layer 7 is supplemented and transmitted to the separator 3 while the gas supply / discharge to the electrode catalyst layer 7 can be made uniform. A considered felt-like carbon fiber current collector 5 is installed. Further, the gas flow path spacer 4 is provided with holes h5, h6, h7 in the portions abutting against the four holes h1, h2, h3, h4 for gas supply / discharge installed in each flat portion of the separator 3. , H8, of which h6 and h7 are connected to the central hollow portion where the carbon fiber current collector 5 is installed.
[0019]
In the combined structure layer of the gas flow path spacer 4 and the current collector 5 illustrated in the second stage from the bottom of FIG. 2, the fuel gas (air gas) is separated from the h7 separator corrugated plate structure W and the carbon fiber current collector. The gas was supplied to the entire electrode through 5 and discharged from h6 as a reactive gas or an unreacted gas. The bottom row of Fig. 2 shows the combined structure layer of the gas flow path spacer and current collector that are turned upside down. Here, air gas (fuel gas) is supplied in the reverse direction of the second row from the bottom.・ Emission is performed.
[0020]
In the figure, 8 is a cooling water flow path spacer provided for the purpose of sealing cooling water from the outside, and 9 is a fuel cell stack that is deformed due to the displacement of the abutting separators when a load is applied vertically when the stack is manufactured. It is a deformation prevention plate made of the same material as the separator that is installed to prevent this.
[0021]
If the A cycles in the figure are repeatedly stacked, a series fuel cell stack without a cooling device is formed, and when several single cells are stacked, a cooling water flow path is also formed by inserting the B cycle. In order to optimize the reduction of fuel cell cost and the improvement of power generation efficiency, it is important to study a good combination of the A cycle and the B cycle. In the stack stacked in this way, cooling water passages that are open to the outside are formed on the front side and the back side in the arrangement of FIG. 2, but the cooling water is from the front (back) to the back (front). It will be supplied to and discharged from the outside of the stack.
[0022]
Furthermore, there is a concern that contact resistance may occur at the separator / carbon fiber current collector or separator / deformation prevention plate interface, leading to power loss. This is achieved while removing the oxide film described in Japanese Patent Application No. 11-170142. If a surface treatment for attaching a noble metal is performed, this problem can be avoided even if high corrosion resistance stainless steel with increased alloy components or titanium is used for durability reliability.
[0023]
As described above, a separator having a relatively simple shape can be used as a constituent material of a polymer electrolyte fuel cell. The key to realizing this was the shape of the gas flow path spacer.
[0024]
In FIG. 2, the present invention has been described with a separator whose corrugated plate has a sinusoidal cross section. However, the rectangular wave separator shown in FIG. 1 or a trapezoidal wave separator (not shown) is used. However, the same structural method can be applied only by matching the wave-like shape of the gas flow path spacer.
The material for the gas flow path spacer and the cooling water flow path spacer may be any resin that does not decompose or deform below the boiling point of the cooling water. Considering the sealing properties of gas and cooling water, and cost, silicon resin, butadiene A rubber-based resin, a fluorine-based resin, or the like is applicable.
[0025]
In addition, each member shown in FIG. 2 is a rod that is used to accurately position the stack or to apply pressure by tightening the entire stack, as long as the basic functions of the fuel cell are not impaired. It is also possible to provide holes or bolt holes.
[0026]
The period and amplitude of the separator corrugated plate are preferably smaller from the viewpoint of gas supply uniformity and current collection efficiency. However, experientially, if the period is about 2 mm and the amplitude is about 1 mm, molding with a gear roll is possible, and fuel cell performance Will also improve. From the viewpoint of reducing the contact resistance, the cross-sectional shape of the corrugated plate portion is less wasteful because the trapezoidal wave and the rectangular wave have a larger contact area than the sine wave.
[0027]
The thickness of the separator and the deformation prevention plate is preferably thin from the viewpoint of weight reduction and cost reduction. However, if it is too thin, the stack strength is weakened and deformation occurs when the stack is tightened. Moreover, there is anxiety that it is too thin from the viewpoint of corrosion resistance and safety. Empirically, it is possible to construct a stack by using a hard material that has been cold-worked in advance with a plate pressure of about 0.1 mm to increase the elastic limit. Stainless steel foil and titanium foil with higher corrosion resistance than SUS304 are possible. The durability reliability is also improved by using.
[0028]
【Example】
Based on the above-mentioned invention, a polymer electrolyte fuel cell was prototyped and gas sealing performance and power generation performance were confirmed. 3 in FIG. 3 is a fuel cell stack stacked according to the configuration shown in FIG. 2, and the vertical direction in FIG. 2 is indicated by arrows in FIG. Bolt holes were arranged for the purpose of positioning and total pressure on the four circumferences of each member, and the stack was tightened using high tension bolts and rigid end plates, but this is not shown in this figure. is there. In the stack cycle, the A cycle and the B cycle shown in FIG. 2 are alternately repeated, and the single cell composed of the A cycle or the B cycle is stacked in 50 stages.
[0029]
The dimensional image of each member is almost the same as that of FIG. 1, and the separator and the deformation prevention plate are made of 20Cr-15Ni-3Mo austenitic stainless steel with a thickness of 0.1 mm and type 2 industrial pure titanium. Two types of solid polymer fuel cells were manufactured using commercially available solid polymer membranes, catalyst electrodes, and carbon fiber current collectors. The gas channel and cooling water channel spacers were prepared by extruding silicone resin and precision molding.
[0030]
Reference numeral 11 in FIG. 3 is a side cap for supplying and discharging cooling water from the side of the stack, and the cap end in contact with the stack is sealed so as not to leak water by silicone resin. 12 and 14 are fuel gas introduction / discharge ports, and 13 and 15 are air gas introduction / discharge ports. Reference numerals 16 and 17 denote cooling water introduction / discharge ports. The prototype solid polymer fuel cell was operated at 80 ° C., and hydrogen and air as fuel gases were humidified and supplied at 90 ° C. to generate electric power. In any of the polymer electrolyte fuel cells, gas leakage and water leakage did not occur, and generation of electric power of about 60 V at an open circuit voltage and about 120 A at a short circuit current was confirmed. Thus, it has been found that even when the separator of the present invention and the gas flow path spacer are used, the fuel cell functions sufficiently.
[0031]
【The invention's effect】
Due to the growing awareness of environmental conservation, the transition from current internal combustion engines using fossil fuels to electrically powered 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.
Among the many problems in this field, the present invention enables high-corrosion resistant stainless steel and titanium to be used at low cost by minimizing the molding process as a separator for a polymer electrolyte fuel cell. It is extremely effective as a technology for realizing a low-cost solid polymer fuel cell.
[Brief description of the drawings]
FIG. 1 is a schematic view showing an example of a separator material of the present invention.
FIG. 2 is a schematic view showing an example of constructing a polymer electrolyte fuel cell stack using the separator of the present invention and a gas flow path spacer.
FIG. 3 is a schematic external view showing an example of a polymer electrolyte fuel cell experimentally applied to the present invention.
[Explanation of symbols]
1. 1. Separator material having a sinusoidal corrugated plate portion 2. Separator material having a rectangular corrugated plate. Separator 4. 4. Gas channel spacer 5. Carbon fiber current collector 6. Solid polymer film Catalyst electrode layer 8. Cooling water flow path spacer 9. Deformation prevention plate 10. 10. Polymer electrolyte fuel cell stack Side cap for supplying and discharging cooling water 12. Fuel gas inlet 13. Air gas inlet 14. Fuel gas outlet 15. Air gas outlet 16. Cooling water inlet 17. Cooling water outlet

Claims (5)

A solid polymer fuel cell separator made of stainless steel, comprising a flat portion having only a pair of opposite ends and a full-width corrugated plate portion formed by a gear roll therebetween. A solid polymer fuel cell separator made of titanium, comprising a flat portion having only a pair of ends and a full-width corrugated plate formed by a gear roll therebetween.   A solid polymer fuel comprising a flat portion of the stainless steel separator according to claim 1 or the titanium separator according to claim 2 having two or more holes serving as cooling water passages or gas passages. Battery separator.   A gas flow path spacer used by being overlapped with the separator according to claim 3, wherein the side wall has a corrugated seal portion that can be fitted to the separator corrugated plate portion to ensure airtightness. Gas flow path spacer.   A solid polymer fuel cell comprising at least one separator according to claim 3 and one or more gas flow path spacers according to claim 4.

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