JP2000133281A - Separator for fuel cell, its manufacture, and fuel cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance gas sealing capability, conductivity, flexibility, and make thin by forming a sheet by binding conductive fibers with a synthetic resin, and specifying the content of the conductive fibers. SOLUTION: A separator is a sheet-like material prepared by binding conductive fibers with a synthetic resin, and the content of the conductive fibers is made 20-55 wt.%. Preferably, electrical resistance of the separator is 1 Ω/cm2 or less. Although the sheet-like material is favorable to be thick in the standpoint of gas sealing, but thinning is required to make a cell small, and the thickness is preferable to be 0.02-2.0 mm. Preferably, gas sealing capability is required to have a gas leakage amount of 2 cc/minute/cm2 or less. As the conductive fiber, bent pitch family carbon fiber is preferable, and as the synthetic resin for binding conductive fibers, a polyphenylene sulfide resin and polypropylene are preferable.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel cell separator such as a phosphoric acid type fuel cell, a solid polymer type fuel cell separator used for an electric vehicle power source, a portable power source, an emergency power source, etc., a method of manufacturing the same, and a fuel cell. About.

[0002]

2. Description of the Related Art So-called fuel cells, which take out chemical energy during the reaction between hydrogen and oxygen as electric power, are being used for various purposes such as electric vehicles. This fuel cell secures a practical voltage by stacking cell units in series, and it is required that the separator used for the fuel cell be both electrically conductive and non-permeable (gas sealing). Have been. Further, in recent years, downsizing of fuel cells has been demanded for use in electric vehicles, and accordingly, thinner separators have been demanded.

Hitherto, as a fuel cell separator,
Generally, a so-called carbon powder sintering type plate material in which a gas passage is cut into a plate material obtained by sintering carbon powder is used, but it is inferior to gas seals, and is liable to be broken by cutting or mounting work. Therefore, there was a limit to the reduction in thickness.

Therefore, conventionally, in order to realize gas sealing properties and thinning, for example, Japanese Patent Application Laid-Open No. Hei 5-307797 discloses a papermaking sheet made of pulp and precursor fibers which become carbon fibers by firing acrylic fibers or the like. In addition, a method has been proposed in which a carbonaceous powder-suspended organic polymer material solution is impregnated and further coated, and then a plurality of these are stuck together and subjected to a heat stabilization treatment and a heat baking treatment.

[0005]

However, Japanese Patent Application Laid-Open No. 5-3
Since the separator described in Japanese Patent No. 079767 is fired in the final step, it is inferior in gas sealing property due to generation of minute pinholes due to organic substances in this carbonization step, so that it is necessary to obtain sufficient non-breathability in order to obtain sufficient air permeability. It was inevitable. In addition, since the separator itself is brittle, it has been difficult to mount it on a moving body such as an automobile or carry it.

The problem to be solved by the present invention is to provide a fuel cell separator which is excellent in gas sealability and electrical conductivity, can be thinner than ever, and is excellent in flexibility, and the use of the separator. It is to provide a fuel cell.

[0007]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies to solve the above-mentioned problems, and as a result, it has been found that a specific synthetic resin sheet-shaped material containing conductive fibers has conductivity, gas sealability, and thinness. The present invention has been found to satisfy the requirements for compactness and flexibility, and to be able to provide a small battery that is suitable for space saving and can be mounted on and carried in a car by using this.

That is, the present invention provides a fuel cell separator in which an electrolyte is sandwiched between electrodes, and a fuel cell separator disposed outside the electrolyte is a sheet-like material in which conductive fibers are bound and solidified with a synthetic resin, and The content of the conductive fiber is 20 to 5;
5% by weight of a fuel cell separator,

An electrolyte is sandwiched between electrodes, and a fuel cell separator disposed outside the electrode is a synthetic resin sheet containing conductive fibers and has an electric resistance of 1%.
A separator for a fuel cell, which has a resistance of Ω / cm ² or less.

It is characterized in that the sheet is formed by laminating a non-woven fabric or paper made of conductive fibers and synthetic resin fibers, and then applying heat and pressure at a temperature not lower than the melting point of the synthetic resin constituting the synthetic resin fibers. The present invention relates to a method for manufacturing a fuel cell separator, and a fuel cell comprising an electrolyte sandwiched between electrodes, and a plurality of battery units each having the separator disposed outside the electrolyte.

The conductive fiber used in the present invention is not particularly limited, but may be various metal fibers such as stainless steel, PAN-based carbon fiber made of acrylic fiber, coal or petroleum pitch, or naphthalene-based pitch. Various types of carbon fibers such as pitch-based carbon fiber, phenolic resin-based carbon fiber, rayon-based carbon fiber, vapor grown carbon fiber, and various conductive materials such as polyacetylene, polyphenylene, polypyrrole, polythiophene, polyaniline, and polyacene. Polymer fibers, inorganic or organic fibers, and metal deposited or plated fibers can be used alone or in combination. Among these, carbon fibers are particularly preferred from the viewpoint of corrosion resistance, and among them, pitch-based carbon fibers are preferred from the viewpoint of excellent conductivity.

Among these pitch-based carbon fibers, from the viewpoint of the uniformity of the entanglement, the fiber shape is preferably a opened carbon fiber. Here, a curved carbon fiber has a specific volume larger than that of a straight carbon fiber when the aspect ratio of one fiber is 50 or more. Specifically, the specific volume is 9 cm when the aspect ratio is converted to 500. ³ / g or more. For example, pitch-based carbon fibers produced by a vortex method are suitable. As such a curved carbon fiber, the smaller the fiber diameter is, the more advantageous the conductivity is. Specifically, the diameter is 5 μm.
Those having a range of m to 20 μm are preferred. Although the length and the like are not limited, the length of the bent carbon fiber
It is preferable that the aspect ratio be 10% by weight or more from the viewpoint of conductive performance.

Next, as the synthetic resin for binding the conductive fibers, various polymer substances are applied and are not particularly limited. For example, polyethylene, polypropylene, polystyrene, ABS resin, nylon 6 Polyamide resins such as nylon 66, nylon 46, modified nylon 6T, nylon MXD6, and polyphthalamide;
Polyacetal, polycarbonate, modified polyphenylene ether, polybutylene terephthalate, polyethylene terephthalate, polycyclohexylene terephthalate, polyphenylene sulfide, polythioether sulfone, thermoplastic polyimide, polyether ether ketone, polyether nitrile, polyarylate, polysulfone, polyether sulfone , Polyetherimide, polyamideimide, liquid crystal polymer, polytetrafluoroethane, fluorine resin such as polyvinylidene fluoride,
Wholly aromatic polyester, polyimide, phenolic resin,
Melamine resin, diallyl phthalate resin, epoxy resin, vinyl ester resin, polyamino bismaleimide,
Various thermoplastic resins and thermosetting resins, such as triazine resin, cross-linked polyimide, thermoplastic elastomer such as polyester / polyester elastomer, polyester / polyether elastomer, water glass, silica sol,
An inorganic polymer such as alumina sol may be mentioned, and is appropriately selected from these depending on the operating temperature of each fuel cell, heat resistance and durability against the electrolyte. For example, for a phosphoric acid type fuel cell application, a polyphenylene sulfide resin is preferable from the viewpoint of corrosion resistance and heat resistance, and for a polymer electrolyte fuel cell, polypropylene is preferable from the viewpoint of corrosion resistance and mechanical strength.

[0014] The separator of the present invention is a sheet-shaped product obtained by solidifying the conductive fibers with the synthetic resin, and has a conductive fiber content of 20 to 55% by weight as described above, or The electric resistance is 1 Ω / cm ² or less.

When the conductive fiber content is less than 20% by weight, no conductivity is exhibited, and when it exceeds 55% by weight, the gas sealing property is poor.

That is, in order to enhance the conductivity, it is essential that the conductive fibers be uniformly distributed in the synthetic resin matrix and that the conductive fibers be present at a high density in order to secure the contact points between the conductive fibers. It is. On the other hand, the non-breathability of the sheet-shaped article is obtained by forming a continuous layer of conductive fibers and a synthetic resin that binds and solidifies the conductive fibers. Therefore, according to the present invention, when the amount of the conductive fiber is less than the above 20% by weight, the contact points between the conductive fibers are not sufficiently secured, resulting in poor conductivity. Continuity is impaired, and gas sealability, which is the original characteristic of a separator, cannot be obtained. In addition, the range of 30 to 50% by weight is particularly preferable from the viewpoint that the performance balance is further improved.

On the other hand, when the electric resistance exceeds 1 Ω / cm ² , the conductivity is poor and the above-mentioned problem is caused.

Further, the thickness of the sheet-shaped material is more advantageous for the gas sealing property, which is one of the objects of the present invention, but on the other hand, a thinner battery is required for miniaturization of the battery. Therefore, the thickness of the sheet-shaped article of the present invention is 0.02.
-2.0 mm, especially preferably in the range of 0.1-1.0 mm.

As described above, the separator of the present invention is characterized by having excellent gas sealing properties, and more specifically, preferably has a gas leak rate of ² cc / min / cm ² or less.

The method for producing such a fuel cell separator is not particularly limited. For example, a synthetic resin comprising a synthetic fiber and a non-woven fabric or paper made of conductive fibers and synthetic resin fibers may be superposed. A method of heating and pressing at a temperature equal to or higher than the melting point to form an integrated sheet-shaped object,
A method of laminating a nonwoven fabric or paper made of conductive fibers and a thermoplastic resin film, melting and integrating by heating and pressing to form a sheet-shaped product, impregnating a felt made of conductive fibers with a thermosetting resin, Examples of the method include a method of curing to form a sheet, a method of melting and mixing the conductive fiber and the thermoplastic resin, and extruding the film into a sheet. Among them, in particular, the production method of the present invention relating to the present invention, that is, laminating with a nonwoven fabric or paper made of conductive fibers and synthetic resin fibers, and then heating and pressing at a temperature equal to or higher than the melting point of the synthetic resin constituting the synthetic resin fibers to integrate And a nonwoven fabric or paper made of conductive fibers and synthetic resin fibers, and a resin sheet made of the same kind of synthetic resin as the synthetic resin fibers, and then the melting point of the synthetic resin. A method (method) for producing a separator for a fuel cell, wherein the sheet-shaped material is integrated by heating and pressing as described above.
However, it is preferable because of easy production. Among them, the latter method is particularly preferable because it has good gas sealing properties and is excellent in all performance balances.

That is, in the above-described sintered plate of carbon powder, the gas passage is required to be cut in the sintered plate of carbon powder, the process is complicated, and the process is complicated.
The separator described in Japanese Patent No. 307967 requires complicated steps such as impregnation of a paper-made sheet with a carbonaceous powder-suspended organic polymer substance solution, coating, bonding, heat stabilization, and heat baking. Therefore, the separator of the present invention, in addition to various properties such as conductivity, gas sealing properties, and thinning, is excellent in productivity with much less complicated steps in the manufacturing method than in the conventional product. .

Further, by using a mixed non-woven fabric or paper composed of conductive fibers and synthetic resin fibers, a uniform sheet-shaped product can be obtained only by melting the resin fibers under heat and pressure. The resin sheet to be superimposed on the resin has a small flow due to melting, and easily retains a continuous layer.

Here, the nonwoven fabric can be obtained by a known method using conductive fibers and synthetic resin fibers.
For example, a needle punch method, a resin bond method, a spun bond method, a thermal bond method, a wet method, and the like can be given.

The paper can be obtained by a known method using conductive fibers and synthetic resin fibers. For example, paper making, dehydration,
It can be manufactured by a process such as drying.

Here, the thickness of the nonwoven fabric or paper is not particularly limited, but may be 0.02 to 3.0.
mm.

Next, the resin sheet made of the same kind of synthetic resin as the synthetic resin fibers constituting the nonwoven fabric or paper in the method is not particularly limited, but it may be uniaxially or biaxially stretched even if it is not stretched. It may be a sheet,
A non-stretched sheet is preferable from the viewpoint that workability during heating and pressurization with a nonwoven fabric or paper and dispersibility of the conductive fibers in the separator are improved.

As the conductive fiber in the method and the method, any of the above-mentioned conductive fibers can be used, and as the synthetic resin fiber in the method, and the synthetic resin fiber and the resin sheet in the method, the conductive fiber can be used. It goes without saying that any of the polymer substances exemplified as the synthetic resin to be applied can be used.

In the case of a ribbed separator, the separator can be obtained by laminating and adhering a sheet-shaped member and a sheet-shaped member from which a groove corresponding to a gas passage has been removed in advance.

Next, as a method of integrating the above-mentioned nonwoven fabric or paper and a resin sheet by heat and pressure molding,
Continuous press molding such as batch-type press molding, continuous batch-type press molding, and double-belt press may be used.

Although the separator thus obtained can be used for a fuel cell composed of only a single cell unit, it is extremely useful as a fuel cell of the present invention described in detail below. That is, the battery of the present invention is a fuel cell characterized in that an electrolyte is sandwiched between electrodes, and a plurality of battery units each having the separator disposed outside thereof are stacked.

Here, the fuel cell uses a power generation system in which hydrogen obtained by reforming the fuel is used as a main fuel, and chemical energy generated when the hydrogen reacts with oxygen is used as electric power. The fuel cell according to the invention is formed by stacking a plurality of battery units for generating power in series. Here, although the configuration of the battery unit is not particularly specified, for example, a structure in which the components shown in FIGS. Specifically, as shown in FIGS. 2 and 3, the battery unit is configured such that the negative electrodes 4 and 9 and the positive electrodes 6 and 10 are in close contact with the electrolyte plate 5 therebetween, and the separators 3 and 8 are formed of hydrogen when the batteries are stacked. And oxygen as well as a current collector. Further, in the case of a ribbed separator, a structure in which a groove (recess 7) is provided in the separator as a gas flow path, and in the case of a ribbed electrode, a groove (recess 11) is provided in the electrode.

The number of stacked battery units depends on the application and the required voltage, and is not particularly limited.
It is preferably 00 sheets.

Further, the fuel cell of the present invention specifically includes
KOH electrolyte, alkaline fuel cell using pure hydrogen as fuel, H ₃ PO ₄ electrolyte, phosphoric acid fuel cell using crude hydrogen as fuel, fluoroplastic acid electrolyte, solid high that the crude hydrogen as fuel It can be used as a molecular fuel cell and the like.

The fuel cell of the present invention described in detail above is resistant to impact and can be miniaturized. For example, in addition to electric vehicles, portable power supplies, emergency power supplies, etc. It can be used as a power source for various moving objects such as spacecraft.

[0035]

The present invention will be described below with reference to examples. In addition, the air permeability test, the electric resistance, and the impact test in the examples were performed as follows.

[Air permeability test] Air permeability was measured according to JIS P811.
7 (Gurley densometer), 1
The measurement shows the time (unit: second) in which 00 cc of air passes.

[Electrical Resistance] The electrical resistance in the thickness direction was determined by sandwiching a test piece between two flat copper plates, 5 kg / m ^2.
The resistance between the copper plates was measured under a pressure of. The obtained value was divided by the area of the test piece and expressed in (unit: Ω / cm ² ).

[Impact test] JIS K5400-199
0 In accordance with 8.3.1 “General paint test method, impact resistance, falling ball method”, a 300 g steel ball was dropped from a height of 30 cm, and the presence or absence of defects was visually evaluated.

Example 1 40 parts by weight of curved mesophase pitch-based carbon fiber / 60 parts by weight of polyphenylene sulfide resin fiber, basis weight 30
Two sheets of mixed felt of 0 g / m ² were stacked, sandwiched between heating plates at 305 ° C., and heated and pressed under a pressure of 10 kg / cm ² for 20 minutes to obtain a sheet-shaped separator. The separator has a thickness of 0.6 mm, air permeability of 600 seconds or more, and an electrical resistance of 0.
It was 5 Ω / cm ² . When an impact test was performed using this separator, no change in appearance was observed.

The polyphenylene sulfide resin film of Example 2 songs like mesophase pitch-based carbon fiber 70 parts by weight / the polyphenylene sulfide resin fibers made 30 parts by weight per unit area of mixed felt 120 g / m ^2, unit weight 160 g / m ^2, wherein Pile the mixed felt in order, put it between 305 ° C heating plate, 5kg
The sheet was heated and pressed under a pressure of / cm ² for 20 minutes to obtain a sheet-shaped separator. The thickness of the separator was 0.4 mm, the air permeability was 600 seconds or more, and the electric resistance was 0.6 Ω / cm ² . When an impact test was performed using this separator, no change in appearance was observed.

Example 3 45 parts by weight of curved mesophase pitch-based carbon fiber / 55 parts by weight of polyphenylene sulfide resin fiber, basis weight 30
A mixed felt of 0 g / m ² was sandwiched between heating plates at 305 ° C., and heated and pressed under a pressure of 10 kg / cm 2 for 20 minutes to obtain a sheet-shaped material. The sheet-shaped object is 0.3 m thick
m, and the electrical resistance value was 0.5Ω / cm ² .

Next, the sheet-shaped material was placed in a groove having a groove width of 2 m.
m, and punching was performed at a groove interval of 2 mm to obtain a punched molded plate.

Next, as shown in FIG. 1, the above-mentioned stamped and formed plate (symbol 1 in FIG. 1) was vertically stacked on the sheet-shaped separator (symbol 2 in FIG. 1) obtained in Example 1, and 290 ° C.
And heated and pressed under a pressure of 10 kg / cm ² for 10 minutes, and melt-bonded to obtain a grooved separator.
The separator had a thickness of 1.2 mm, air permeability of 600 seconds or more, and an electric resistance value of 1.1 Ω / cm ² . When an impact test was performed using this separator, no change in appearance was observed.

Example 4 A mixed felt consisting of 30 parts by weight of mesophase pitch-based carbon fiber / 15 parts by weight of general-purpose pitch-based carbon fiber / 55 parts by weight of polypropylene resin fiber having a basis weight of 400 g / m ² was prepared.
The sheet-shaped separator was sandwiched between heating plates at 190 ° C. and heated and pressed under a pressure of 20 kg / cm ² for 15 minutes. The separator had a thickness of 0.4 mm, a gas permeability of 600 seconds or more, and an electric resistance of 0.9 Ω / cm ² . When an impact test was performed using this separator, no change in appearance was observed.

Example 5 Using the separator obtained in Example 3, a separator, a plate electrode (negative electrode), an electrolyte plate, a plate electrode (positive electrode) and a separator were laminated as shown in FIG. 2 to prepare a battery unit.
Forty battery units are stacked in series and 1
A 5 × 15 × 20 cm fuel cell for 25 V was prepared. It can be seen that a commercially available 25 V fuel cell is usually about 40 cm, which is about half the height.

COMPARATIVE EXAMPLE 1 A paper sheet made of acrylic fiber and pulp was impregnated with a phenol methanol solution in which a carbonaceous powder and a powdered phenol resin were suspended, laminated, prebaked, and repeatedly impregnated. The separator (specific gravity: 1.3, thickness: 2 mm) was manufactured by performing a baking treatment. When an impact test was performed using this separator, defects occurred.

According to the present invention, a fuel cell separator excellent in gas sealability and conductivity, thinner than ever, and excellent in flexibility, and a fuel cell using the separator Can be provided.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example (Example 3) of a separator (ribbed separator) of the present invention.

FIG. 2 is a perspective view showing a basic configuration of a flat panel fuel cell using a separator type with ribs.

FIG. 3 is a perspective view showing a basic configuration of a flat panel fuel cell using a ribbed electrode type.

[Explanation of symbols]

1: punching plate 2: sheet-like object 3: Ribbed separator 4: plate electrode (negative electrode) 5: electrolyte plate 6: plate electrode (cathode) 7: recess (O ₂ passage) 8: plate type separator 9: Ribbed Electrode (negative electrode) 10: ribbed electrode (positive electrode) 11: recess (H ₂ passage)

Claims (11)

[Claims] 1. A fuel cell separator in which an electrolyte is sandwiched between electrodes, and a fuel cell separator further disposed outside the separator is a sheet-shaped material in which conductive fibers are bound and solidified with a synthetic resin, and
A separator for a fuel cell, wherein the content of the conductive fiber is 20 to 55% by weight. 2. A fuel cell separator in which an electrolyte is sandwiched between electrodes and further disposed outside thereof is a synthetic resin sheet containing conductive fibers and has an electric resistance of 1 Ω / cm ² or less. A separator for a fuel cell, characterized in that: 3. The sheet-shaped article has a thickness of 0.02 to 2.0.
3. The fuel cell separator according to claim 1, wherein 4. The fuel cell separator according to claim 1, wherein the conductive fiber is a curved pitch-based carbon fiber. 5. The fuel cell separator according to claim 1, wherein the synthetic resin is a polyphenylene sulfide resin. 6. The fuel cell separator according to claim 1, wherein a gas leak amount is 1 cc / min / cm ² or less. 7. A sheet-shaped article which is laminated with a nonwoven fabric or paper made of conductive fibers and synthetic resin fibers, and then heated and pressed at a temperature equal to or higher than the melting point of the synthetic resin constituting the synthetic resin fibers. Of producing a fuel cell separator. 8. A nonwoven fabric or paper made of a conductive fiber and a synthetic resin fiber is overlapped with a resin sheet made of the same kind of synthetic resin as the synthetic resin fiber, and then heated and pressed at a temperature not lower than the melting point of the synthetic resin to be integrated. The method according to claim 7, wherein the sheet is formed into a sheet shape. 9. The method according to claim 7, wherein the conductive fibers are curved pitch-based carbon fibers. 10. The production method according to claim 7, wherein the synthetic resin is a polyphenylene sulfide resin. 11. A fuel comprising an electrolyte sandwiched between electrodes, and further comprising a plurality of battery units provided with the separator according to claim 1 disposed outside the electrolyte. battery.