Electroconductive sheet

Abstract

As shown in fig. 1, an electroconductive sheet 10 according to the present invention has a first electroconductive layer 12 and a second electroconductive layer 14. The first electroconductive layer 12 contains a first thermoplastic resin 122 and first electroconductive particles 124. At least some of the first electroconductive particles 124 penetrate the thickness of the first electroconductive layer 12. The second electroconductive layer 14 contains a second thermoplastic resin and electroconductive fibers. The electroconductive fibers are arranged so as to extend in the direction of the surface of the second electroconductive layer 14.

Description

Conductive sheet

[0001] The present invention relates to an electrically conductive sheet, and more particularly to an electrically conductive sheet that can be used as a separator for a fuel cell.

[0002] Conventionally, conductive sheets used as fuel cell separators have been developed that are made of metal materials and carbon materials. Fuel cell separators made of carbon materials are advantageous in terms of lighter weight and chemical resistance compared to separators primarily made of metal materials. On the other hand, fuel cell separators made of carbon materials sometimes lack sufficient strength, and in particular, have a higher probability of gas leakage due to cracking than metal separators. Furthermore, fuel cell separators made of carbon materials have drawbacks, such as a decrease in conductivity when binder components such as resins are added to prevent cracking. Various proposals have been made to address these issues.

[0003] Patent Document 1 discloses a fuel cell separator characterized by having a conductive gas barrier layer (B) on a conductive layer (A) made of conductive fibers bound and solidified with a synthetic resin.

[0004] Patent Document 2 discloses a fuel cell separator precursor obtained by impregnating a porous sheet containing a conductive filler with a resin composition containing a thermoplastic resin and a conductive filler.

[0005] JP 2001-15131 A JP 2019-40719 A

[0006] The present invention provides a novel conductive sheet that can have good gas impermeability and conductivity.

[0007] After extensive research, the inventors have found that the above-mentioned problems can be solved by the following means, and have thus completed the present invention. That is, the present invention is as follows: <Aspect 1> A conductive sheet having a first conductive layer and a second conductive layer, wherein the first conductive layer contains a first thermoplastic resin and first conductive particles, at least a portion of the conductive particles penetrating the thickness of the first conductive layer, and the second conductive layer contains a second thermoplastic resin and conductive fibers, the conductive fibers being arranged so as to extend in the plane direction of the second conductive layer. <Aspect 2> The conductive sheet according to Aspect 1, which has the first conductive layer, the second conductive layer, and another first conductive layer in this order. <Aspect 3> The conductive sheet according to Aspect 1, which has the second conductive layer, the first conductive layer, and another second conductive layer in this order. <Aspect 4> The conductive sheet according to any one of Aspects 1 to 3, wherein the particle diameter of the first conductive particles measured by laser diffraction is 100 μm or more and 300 μm or less. <Aspect 5> The conductive sheet according to any one of Aspects 1 to 4, wherein the first conductive particles are carbonaceous particles. <Aspect 6> The conductive sheet according to any one of Aspects 1 to 5, wherein the conductive fibers are carbon fibers. <Aspect 7> The conductive sheet according to any one of Aspects 1 to 6, wherein the second conductive layer further contains second conductive particles. <Aspect 8> The conductive sheet according to any one of Aspects 1 to 7, wherein the first thermoplastic resin comprises at least polyamide. <Aspect 9> The conductive sheet according to any one of Aspects 1 to 8, wherein the second thermoplastic resin comprises at least polyphenylene sulfide or polyamide. <Aspect 10> The conductive sheet according to any one of Aspects 1 to 9, wherein the conductive sheet is a separator for a fuel cell. <Aspect 11> A fuel cell comprising the conductive sheet according to Aspect 10.

[0008] According to the present invention, a novel conductive sheet can be provided that can have good gas impermeability and conductivity.

[0009] Fig. 1 is a side cross-sectional view of a first embodiment of the conductive sheet of the present invention. Fig. 2(a) is a side cross-sectional view of a second embodiment of the conductive sheet of the present invention. Fig. 2(b) is a side cross-sectional view of a third embodiment of the conductive sheet of the present invention. Fig. 3 is a reduced side cross-sectional view of the second embodiment of the conductive sheet of the present invention.

[0010] <Conductive Sheet> As shown in FIG. 1 , the conductive sheet 10 of the present invention has a first conductive layer 12 and a second conductive layer 14, the first conductive layer 12 containing a first thermoplastic resin 122 and first conductive particles 124, at least a portion of the first conductive particles 124 penetrating the thickness of the first conductive layer 12, and the second conductive layer 14 containing a second thermoplastic resin and conductive fibers, the conductive fibers being arranged so as to extend in the plane direction of the second conductive layer 14.

[0011] In the first conductive layer, at least a portion of the first conductive particles penetrate the thickness of the first conductive layer, thereby ensuring conductivity in the thickness direction of the first conductive layer while achieving good gas impermeability. Meanwhile, in the second conductive layer, the conductive fibers are arranged so as to extend in the plane direction of the second conductive layer, thereby ensuring conductivity in the plane direction. Furthermore, in the second conductive layer, the conductive fibers are arranged so as to extend in the plane direction of the second conductive layer, thereby maintaining the strength of the second conductive layer in accordance with the tensile strength of the conductive fibers.

[0012] As shown in FIG. 2( a ), the conductive sheet of the second embodiment of the present invention has the first conductive layer 12, the second conductive layer 14, and another first conductive layer 12 in this order.

[0013] Furthermore, the conductive sheet of the third aspect of the present invention has the second conductive layer 14, the first conductive layer 12, and another second conductive layer 14 in this order, as shown in FIG. 2(b).

[0014] The conductive sheet of the present invention can have good conductivity and gas impermeability without using an expanded graphite sheet, that is, the conductive sheet of the present invention does not need to include an expanded graphite sheet.

[0015] Furthermore, since the first conductive layer and the second conductive layer of the conductive sheet of the present invention contain a thermoplastic resin, the first conductive layer and the second conductive layer can be integrally formed into an uneven shape as shown in FIG. 3 without impairing gas permeability.

[0016] The conductive sheet of the present invention can be used particularly as a separator for a fuel cell, and can also be used as a bipolar plate for a redox flow battery or a water electrolysis device.

[0017] Each component of the present invention will be described below.

[0018] <First Conductive Layer> The first conductive layer contains a first thermoplastic resin and first conductive particles, and at least a portion of the first conductive particles penetrates the thickness of the first conductive layer.

[0019] The thickness of the first conductive layer may be 30 μm or more and 300 μm or less. This thickness may be 30 μm or more, 40 μm or more, 50 μm or more, 60 μm or more, 70 μm or more, or 80 μm or more, and may be 300 μm or less, 250 μm or less, 220 μm or less, 200 μm or less, 180 μm or less, 150 μm or less, 140 μm or less, 130 μm or less, 120 μm or less, or 100 μm or less.

[0020] (First Thermoplastic Resin) As the first thermoplastic resin, it is preferable to use a resin that can withstand the chemical environment of the fuel cell, does not soften or melt at the reaction temperature of the fuel cell, and softens or melts during press molding. Examples of such resins that can be used include polypropylene, polyethylene, polyamide, polyphenylene sulfide (PPS), polyvinylidene fluoride (PVDF), polyetherimide (PEI), polyethylene terephthalate (PET), polyethylene naphthalate (PEN), liquid crystal polymer (LCP), polyimide (PI), polycarbonate (PC), polyphenylene ether (PPE), polysulfone (PSU), polyethersulfone (PES), polyetheretherketone (PEEK), polyurethane, epoxy resin, silicone resin, urea resin, phenolic resin, thermosetting polyimide, thermosetting isocyanate, and polymers or mixtures of two or more of the above.

[0021] In particular, when the first conductive particles are carbonaceous particles, the first thermoplastic resin preferably contains at least a polar resin, such as polyamide, polyimide, polyurethane, epoxy resin, urea resin, etc., and particularly, the use of these resins is preferable from the viewpoint of improving wettability with the first conductive particles and thereby improving gas impermeability at the interface between the first thermoplastic resin and the first conductive particles. Examples of polyamides that can be used include nylon, particularly semi-aromatic nylon.

[0022] The melting point of the first thermoplastic resin may be 200° C. or higher, 210° C. or higher, 220° C. or higher, 230° C. or higher, 240° C. or higher, 250° C. or higher, or 260° C. or higher, and may be 350° C. or lower, 340° C. or lower, 330° C. or lower, 320° C. or lower, 310° C. or lower, 300° C. or lower, 290° C. or lower, or 280° C. In particular, the melting point of the first thermoplastic resin may be the same as, lower than, or higher than the melting point of the second thermoplastic resin.

[0023] The glass transition temperature (Tg) of the first thermoplastic resin may be 70°C or more, 80°C or more, or 90°C or more, and may be 150°C or less, 140°C or less, or 130°C or less.

[0024] Here, in the present invention, the melting point and thermal decomposition temperature can be measured by differential thermal analysis-thermogravimetric analysis (TG-DTA) under conditions of a nitrogen atmosphere and a heating rate of 10 ° C. / min. Specifically, a sample is heated under a nitrogen atmosphere at a heating rate of 10 ° C. / min, and a curve (TG curve) with mass on the vertical axis and temperature on the horizontal axis and a curve (DTA curve) with temperature difference on the vertical axis and temperature on the horizontal axis are obtained by differential thermal analysis-thermogravimetric analysis (TG-DTA) in accordance with JIS K0129, whereby the melting point and thermal decomposition temperature can be obtained. More specifically, when an endothermic peak is observed in the DTA curve at a position where no mass loss is observed in the TG curve, the temperature at which this minimum value is obtained can be determined as the melting point. Furthermore, when a downward shift of the baseline of the DTA curve is observed at a position where no mass loss is observed in the TG curve, the glass transition temperature (Tg) can be determined as the temperature at the point where a line equidistant in the vertical axis direction from the extended line of each baseline intersects with the curve of the transition portion of the baseline.

[0025] (First Conductive Particles) At least a portion of the first conductive particles penetrates the thickness of the first conductive layer.

[0026] The particle diameter of the first conductive particles may be, for example, 70 μm or more and 500 μm or less, for example, 70 μm or more, 80 μm or more, 90 μm or more, or 100 μm or more, or 500 μm or less, 480 μm or less, 450 μm or less, 430 μm or less, 400 μm or less, 380 μm or less, 350 μm or less, 330 μm or less, 300 μm or less, 280 μm or less, 250 μm or less, 230 μm or less, 200 μm or less, 190 μm or less, or 180 μm or less. In particular, the particle diameter of the first conductive particles may be larger than the thickness of the first conductive layer. The particle diameter of the first conductive particles can be adjusted by known grinding means such as a ball mill or a bead mill.

[0027] In the present invention, the term "particle size" refers to the median diameter (D50) calculated on a volume basis by laser diffraction. This particle size is calculated assuming that the particles are spherical, and therefore the particle size of the first conductive particles may be larger than the thickness of the first conductive layer.

[0028] The first conductive particles may be, for example, carbonaceous particles, such as graphite particles and carbonaceous composite conductive fillers.

[0029] The content of the first conductive particles may be 25% by mass or more and 80% by mass or less, based on the mass of the first conductive layer. This content may be 25% by mass or more, 30% by mass or more, 35% by mass or more, 40% by mass or more, 45% by mass or more, 50% by mass or more, or 55% by mass or more, and may be 80% by mass or less, 75% by mass or less, 70% by mass or less, or 65% by mass or less.

[0030] (First Conductive Particles: Carbonaceous Composite Conductive Filler Particles) The carbonaceous composite conductive filler particles have graphite particles and amorphous carbon coating the graphite particles.

[0031] Here, the presence of amorphous carbon on the surface of the carbonaceous conductive filler particles can be confirmed by the G-band (1450 to 1700 cm) obtained in the Raman spectroscopy of the conductive filler. －１ ) D-band (1100-1450 cm －１ ) is 0.5 or more, particularly 0.5 or more and 1.1 or less. This ratio is less than 0.5 for graphite alone, and exceeds 1.1 for amorphous carbon alone. Therefore, the ratio of 0.5 or more and 1.1 or less is considered to be due to the fact that the amorphous carbon layer on the surface is thin or there are gaps in the amorphous carbon layer on the surface, which allows the spectrum due to the bonds derived from graphite to be obtained in addition to the spectrum due to the bonds derived from amorphous carbon.

[0032] The graphite particles contained in the carbonaceous composite conductive filler particles may be graphite particles in any form, such as flake-like, spherical, blocky, or thin flake-like, but from the viewpoint of conductivity, flake-like or spherical graphite particles are preferably used.

[0033] In the carbonaceous composite conductive filler particles, the ratio of graphite particles to the total of amorphous carbon and graphite particles may be 10% by mass to 95% by mass. A small ratio is preferable because the graphite particles are covered with amorphous carbon, thereby suppressing problems such as peeling at the interface between the resin material and the graphite particles and cleavage of the graphite particles themselves. On the other hand, a large ratio is preferable because it utilizes the good conductivity of the graphite particles. This ratio may be 10% by mass or more, 20% by mass or more, 30% by mass or more, 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and may be 95% by mass or less, 90% by mass or less, 85% by mass or less, or 80% by mass or less.

[0034] Here, with regard to the present invention, the "ratio of graphite particles to the total of amorphous carbon and graphite particles" can be determined based on the weight ratio of various raw materials in the production stage of the carbonaceous composite conductive filler particles and the residual rate after firing (carbon yield), with the residual rate of the graphite particles used being set at 100 mass%.

[0035] In the carbonaceous composite conductive filler particles, the graphite particles dispersed in the amorphous carbon may have a D50 of 1 μm to 100 μm. The D50 of the graphite particles may be 1 μm or more, 2 μm or more, 3 μm or more, 4 μm or more, 5 μm or more, 7 μm or more, 10 μm or more, 15 μm or more, 25 μm or more, or 20 μm or more, or may be 100 μm or less, 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, 50 μm or less, 40 μm or less, or 30 μm or less.

[0036] The carbonaceous composite conductive filler particles can be produced by any method. For example, graphite particles can be dispersed in a resin material to obtain a graphite particle-containing resin block in which the graphite particles are dispersed, the graphite particle-containing resin block can be optionally cured and / or infusibilized, and then fired in an inert atmosphere to amorphously carbonize the resin material, thereby obtaining a graphite particle-containing amorphous carbon block, which can then be pulverized and optionally classified to obtain the carbonaceous composite conductive filler particles. The graphite particles can be dispersed in the resin material by any known method.

[0037] The resin material used herein that turns into amorphous carbon can be any thermoplastic resin or curable resin that turns into amorphous carbon when baked in an inert atmosphere. Examples of thermoplastic resins include, but are not limited to, thermoplastic polyimide resin (TPI), chlorinated polyvinyl chloride resin (CPVC), polyvinyl chloride resin (PVC), polyetherimide resin (PEI), and polyacrylonitrile resin (PAN). Examples of thermosetting resins include, but are not limited to, polyimide resin, furan resin, and phenolic resin.

[0038] <Second conductive layer> The second conductive layer contains a second thermoplastic resin and conductive fibers, and the conductive fibers are arranged so as to extend in the surface direction of the second conductive layer.

[0039] Additionally, the second conductive layer may further contain optional second conductive particles.

[0040] (Second Thermoplastic Resin) As the second thermoplastic resin, those listed as the first thermoplastic resin can be used alone or in combination.

[0041] In particular, in the second embodiment of the conductive sheet of the present invention, it is preferable that the second thermoplastic resin contains at least polyphenylene sulfide (PPS), and in particular that this be used, from the viewpoint of obtaining chemical resistance.

[0042] In the second embodiment of the conductive sheet of the present invention, it is preferable that the second thermoplastic resin contains at least a polyamide, and in particular that this be used, from the viewpoint of reducing gas permeability.

[0043] For the melting point and glass transition temperature of the second thermoplastic resin, reference can be made to the description of the first thermoplastic resin.

[0044] (Conductive Fiber) As the conductive fiber, for example, carbon fiber, metal fiber, etc. can be used.

[0045] As the carbon fiber, for example, milled fiber, chopped fiber, etc. can be used. These may be used alone or in combination.

[0046] The average length of the conductive fibers can be, for example, 100 μm or more, 300 μm or more, 500 μm or more, 1.0 mm or more, 1.5 mm or more, 2.0 mm or more, 2.5 mm or more, or 2.8 mm or more, and can be 50.0 mm or less, 45.0 mm or less, 40.0 mm or less, 35.0 mm or less, 30.0 mm or less, 25.0 mm or less, 20.0 mm or less, 15.0 mm or less, 12.0 mm or less, 10.0 mm or less, 8.0 mm or less, 5.0 mm or less, 4.0 mm or less, or 3.5 mm or less.

[0047] The average fiber diameter of the conductive fibers can be 1 μm or more, 3 μm or more, or 5 μm or more, and can be 50 μm or less, 40 μm or less, 30 μm or less, 20 μm or less, 15 μm or less, or 10 μm or less.

[0048] The content of the conductive fibers may be 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, or 28% by mass or more, relative to the mass of the second conductive layer, and may be 75% by mass or less, 70% by mass or less, 65% by mass or less, 60% by mass or less, 55% by mass or less, 50% by mass or less, 45% by mass or less, 40% by mass or less, 35% by mass or less, or 32% by mass or less.

[0049] (Second Conductive Particles) The second conductive particles may be particles interposed between the conductive fibers.

[0050] The particle diameter of the second conductive particles may be 10 μm or more and 100 μm or less. This particle diameter may be 10 μm or more, 20 μm or more, or 30 μm or more, and may be 200 μm or less, 180 μm or less, 150 μm or less, 130 μm or less, 100 μm or less, 90 μm or less, or 80 μm or less.

[0051] The content of the second conductive particles may be 5% by mass or more and 60% by mass or less, relative to the mass of the second conductive layer, and may be 5% by mass or more, 10% by mass or more, 15% by mass or more, 20% by mass or more, 25% by mass or more, 30% by mass or more, or 35% by mass or more, and may be 60% by mass or less, 55% by mass or less, 50% by mass or less, or 45% by mass or less.

[0052] <Fuel Cell> The fuel cell of the present invention has the above-described fuel cell separator.

[0053] The fuel cell may have a general configuration as long as it has the above-mentioned fuel cell separator, and may, for example, have a fuel cell separator, a cathode gas diffusion layer, a cathode catalyst electrode layer, an electrolyte layer, an anode catalyst electrode layer, and a fuel cell separator in this order.

[0054] Any known material used as a cathode gas diffusion layer, a cathode catalyst electrode layer, an electrolyte layer, an anode catalyst electrode layer, or a fuel cell can be used.

[0055] The present invention will be specifically explained with reference to examples and comparative examples, but the present invention is not limited to these.

[0056] <<Preparation of Fuel Cell Separator>> <Example 1> Using 50 parts by mass of polyphenylene sulfide (PPS) fiber (melting point 278°C, Tg 93°C) as the second thermoplastic resin and 50 parts by mass of carbon fiber (length longer than 1 mm) as the conductive fiber, a separator having a basis weight of 100 g / m was prepared by a dry method. ２A nonwoven fabric sheet was prepared and cut into a piece with a diameter of 88 mm. Next, carbonaceous composite conductive filler particles pulverized to a particle diameter of less than 75 μm as second conductive particles were dispersed in ethanol at 2 mass % to obtain a filler dispersion. This filler dispersion was added dropwise to the nonwoven fabric sheet in an amount 20 times the mass of the nonwoven fabric so that the second conductive particles were added at 40 mass %, and then dried to obtain a precursor for the second conductive layer.

[0057] Next, a 60 μm-thick semi-aromatic nylon film (PA9T, melting point 262°C, Tg 125°C) serving as the first thermoplastic resin was cut into an 88 mm diameter piece. 0.5 g of first conductive particles were evenly sprinkled on top of the first piece, and a second conductive layer precursor was then layered on top of that. Next, 0.5 g of the first conductive particles were sprinkled on top of that, and a 60 μm-thick semi-aromatic nylon film was layered on top of that, creating a five-layer structure of semi-aromatic nylon film / first conductive particles / second conductive layer precursor / first conductive particles / semi-aromatic nylon film. This was then molded into a corrugated shape to obtain a flat fuel cell separator of Example 1 having a first conductive layer / second conductive layer / first conductive layer in that order. Molding was performed by pressing at a temperature of 315°C and a pressure of 15 MPa, followed by cooling to 140°C under pressure and removal. The first conductive particles were carbonaceous composite conductive filler particles pulverized to a particle size of 110 μm or more and less than 180 μm, and the content of the first conductive particles in the first conductive layer after molding was in the range of 50 to 60 mass %.

[0058] When the cross section of the resulting fuel cell separator was observed with a scanning electron microscope, the thickness of the first conductive layer after molding was found to be in the range of 90 to 120 μm.

[0059] Example 2 A fuel cell separator of Example 2 was produced in the same manner as Example 1, except that 50 parts by mass of semi-aromatic nylon (PA9T) fiber (melting point 262°C, Tg 125°C) was used instead of 50 parts by mass of polyphenylene sulfide (PPS) fiber (melting point 278°C, Tg 93°C) as the second thermoplastic resin.

[0060] Example 3 A fuel cell separator of Example 3 was produced in the same manner as Example 1, except that carbonaceous composite conductive filler particles having a particle size of 150 μm or more and less than 220 μm were used instead of the carbonaceous composite conductive filler particles having a particle size of 110 μm or more and less than 180 μm.

[0061] Example 4 A fuel cell separator of Example 4 was produced in the same manner as in Example 1, except that a 60 μm thick PPS film was used instead of the nylon film.

[0062] Comparative Example A 100 μm thick expanded graphite sheet was sandwiched between the second conductive layer precursor prepared in Example 1 on both sides, and molded in the same manner as in Example 1 to prepare a fuel cell separator for the comparative example.

[0063] Reference Example Before sandwiching the expanded graphite sheet with nonwoven fabric sheets from above and below, a composition for an intervening conductive resin layer was applied to both sides of the expanded graphite sheet so that the film thickness after drying would be 25 μm, and then dried to provide an intervening conductive resin layer. This was then sandwiched between the same nonwoven fabric sheets as in Example 1 from above and below, and molded in the same manner as in Example 1 to produce a fuel cell separator of the Reference Example.

[0064] The composition for the intervening conductive resin layer was a mixture of carbon black, graphite, CNT, and PVDF resin melted in NMP solvent.

[0065] <Evaluation> <Gas Permeability> The gas permeability of the prepared fuel cell separator was measured by a differential pressure method in accordance with JIS K7126-1: 2006. Helium was used as the test gas, and the pressure of the test gas on the high-pressure side was set to 100 kPa.

[0066] <Resistance> Carbon paper was placed on both sides of the prepared fuel cell separator, which was then sandwiched between gold-plated flat electrodes and a pressure of 1 MPa was applied. Next, a current of 1 A was applied to the flat electrodes, and the voltage between the electrodes was measured. The resistance at the interface between the flat electrode and the carbon paper was then subtracted from the resulting resistance to measure the resistance.

[0067] <Acid Resistance> The prepared fuel cell separator was cut into a rectangle with a width of 3 mm and a length of 30 mm, and the bending strength (three-point bending) was measured with a support distance of 20 mm. Next, the bending strength was measured in the same manner before and after immersion in a sulfuric acid aqueous solution of Ph2 at 80°C for 96 hours, and the acid resistance was evaluated according to the following evaluation criteria. A: The bending strength after immersion decreased by 5% or less. B: The bending strength after immersion decreased by more than 5%.

[0068] The configurations and evaluation results of the Examples, Comparative Examples, and Reference Examples are shown in Table 1. Note that the "Not Measurable" column for gas permeability in Table 1 indicates that the amount of gas permeation over time could not be measured due to rupture of the fuel cell separator.

[0069]

[0070] It can be seen from Table 1 that the fuel cell separators of the Examples have good gas impermeability and electrical conductivity. In particular, with regard to gas impermeability, the fuel cell separators of the Examples obtained better results than the fuel cell separators of the Comparative Examples and Reference Examples, which used expanded graphite sheets.

[0071] Furthermore, the fuel cell separators of Examples 1 to 3, which used polyamide as the first thermoplastic resin, were particularly good in both gas permeability and resistance.

[0072] Furthermore, the fuel cell separators of the Examples had acid resistance equivalent to that of the Comparative Examples and Reference Examples which used expanded graphite sheets.

[0073] 10: Conductive sheet 12: First conductive layer 122: First thermoplastic resin 124: First conductive particles 14: Second conductive layer

Claims

1. A conductive sheet having a first conductive layer and a second conductive layer, wherein the first conductive layer contains a first thermoplastic resin and first conductive particles, and at least a part of the conductive particles penetrates through the thickness of the first conductive layer; and the second conductive layer contains a second thermoplastic resin and conductive fibers, and the conductive fibers are arranged so as to spread in the plane direction of the second conductive layer.

2. The conductive sheet according to claim 1, having the first conductive layer, the second conductive layer, and another first conductive layer in this order.

3. The conductive sheet according to claim 1, having the second conductive layer, the first conductive layer, and another second conductive layer in this order.

4. The conductive sheet according to claim 1 or 2, wherein the particle diameter of the first conductive particles measured by the laser diffraction method is 100 μm or more and 300 μm or less.

5. The conductive sheet according to claim 1 or 2, wherein the first conductive particles are carbonaceous particles.

6. The conductive sheet according to claim 1 or 2, wherein the conductive fibers are carbon fibers.

7. The conductive sheet according to claim 1 or 2, wherein the second conductive layer further contains second conductive particles.

8. The conductive sheet according to claim 1 or 2, wherein the first thermoplastic resin contains at least polyamide.

9. The conductive sheet according to claim 1 or 2, wherein the second thermoplastic resin contains at least polyphenylene sulfide or polyamide.

10. The conductive sheet according to claim 1 or 2, which is a separator for a fuel cell.

11. A fuel cell having the separator for a fuel cell according to claim 10.

Images