JP6956352B2 - Carbon fiber woven fabric and fuel cell for fuel cell gas diffusion layer - Google Patents

Description

The present invention relates to a carbon fiber woven fabric for a fuel cell gas diffusion layer (sheet) mounted on a transportation system such as a vehicle, a ship, or an aircraft, and a fuel cell in which the carbon fiber woven fabric is incorporated.

Conventionally, fuel cell power generation has been attracting attention as a new energy source due to the high level of interest in environmental issues. Among them, solid polymer fuel cells (hereinafter referred to as "fuel cells"), which are the mainstream for households and vehicles. ) Is a film electrode joint in which electrode catalyst layers are bonded to both sides of the polymer film, a gas diffusion layer (gas diffusion sheet) that guides fuel gas and oxidant gas to the electrode reaction region, and a gas introduction / discharge groove. Unit units (hereinafter referred to as "fuel cell cells") made of separators, sealing materials, etc. are repeatedly laminated, and hundreds of fuel cell cells are laminated and assembled in an area of approximately A4 size. It is a structure that tightens with a plate from both sides.

Among them, the gas diffusion layer incorporated in the fuel cell is mainly made of carbon fiber, which is highly expected for mass production at low cost. Here, the gas diffusion layer is generally a member formed in the form of a thin sheet of 1 mm or less.

The gas diffusion layer has a function of smoothly supplying two reaction gases, a fuel gas containing hydrogen and an oxidizing agent gas containing oxygen, from the outside of the fuel cell to the electrode catalyst layer of the membrane electrode assembly. Is. In addition to this, as a basic function of the gas diffusion layer,
1) Having a sufficiently low electrical resistance to efficiently extract electrical energy,
2) It has sufficient gas permeability to take out a large current and good diffusivity to discharge the generated water generated by the battery without clogging (clogging), so that a large current can be generated.
3) Having cushioning properties (elasticity) that can absorb uneven thickness of laminated members,
Etc. are required.

Since most of such a gas diffusion layer has a paper structure, it has a low cushioning property for absorbing uneven thickness, and above all, there are many steps that consume energy, so that there is a problem that manufacturing cost is high. Therefore, in order to popularize the fuel cell system, it is crucial to have low electric resistance, sufficient gas diffusivity, appropriate cushioning property, sufficient corrosion resistance, energy saving process and low cost.

Therefore, in Patent Document 1, in the warp or weft, a plurality of carbon fiber threads A and carbon fiber threads B thinner than the carbon fiber threads A are alternately arranged, so that the carbon fiber threads A are used on the surface of the woven fabric. The ridges protruding in a band shape are formed, and the concave ridges recessed in a groove shape are formed by the carbon fiber thread B, and the thickness of the carbon fiber thread A, the thickness of the carbon fiber thread B, and the thickness of the thread are formed. It is explained that the ratio (thickness of A) / (thickness of B), the width Wr of the convex portion, the width Wd of the concave portion, and the electric resistance value in the thickness direction are within a predetermined range.

Further, in Patent Document 2, the first gas diffusion layer constituting the anode side electrode and the second gas diffusion layer constituting the cathode side electrode are provided in the first and second flow paths provided in the first and second separators. It is described that the first and second gas flow paths are provided so as to face each other.

Japanese Unexamined Patent Publication No. 2012-12719 Japanese Unexamined Patent Publication No. 2000-1138999

Toshiaki Kusakari, 3 outsiders "Analysis of Gas Diffusion Resistance of Gas Diffusion Layer of Fuel Cell Using 1D Cell", Pre-printing of Academic Lecture (Autumn), Society of Automotive Engineers of Japan, No. 111-13, p. 1-3, issued in October 2013

However, when the carbon fiber woven fabric disclosed in Patent Document 1 is incorporated as an electrode for a single cell of a fuel cell, the contact between the surface of the carbon fiber woven fabric and the plane of the membrane electrode assembly is still in contact with the thick fiber portion. , The thin fiber portions are separated by half the difference in their fiber diameters compared to the thick fiber portions.

Therefore, the contact at that portion is relatively weak, the conduction of the fine fiber portion is small, and the power generation efficiency of the catalyst portion of the membrane electrode assembly is lowered. The power generation performance disclosed in the examples of the same document also ^{outputs only 0.65 V under the condition of 0.6 mA / cm 2} , which cannot be said to be good at all. This requires a large number of single cells for fuel cell applications for mobile vehicles that require large amounts of power.

Further, the gas diffusion layer incorporated in the fuel cell disclosed in Patent Document 2 requires precision processing of cutting fine grooves in the material (carbon paper or porous carbon) used for the gas diffusion layer. Therefore, in order to use the gas diffusion layer as a member, the manufacturing cost is high, including problems such as yield. This makes it difficult to supply members at low cost toward the realization of fuel cells for mobile vehicles in which a large number of members are incorporated.

Therefore, in the present invention, the thickness when laminated in the fuel cell is made small (thin), and the gas diffusion which can improve the adhesion when laminated by being sandwiched between the membrane electrode assembly and the separator and reduce the electric resistance. An object of the present invention is to provide a carbon fiber woven fabric for layers.

At the same time, it is an object of the present invention to provide a low-cost carbon fiber fabric for a fuel cell gas diffusion layer, which has excellent gas diffusivity in a fuel cell as a gas diffusion layer and can generate a large current.

In order to solve the above-mentioned problems, the present inventor has focused on carbon fiber woven fabrics and conducted intensive studies. We have come to discover the existence of carbon fiber woven fabrics with a special weave.

That is, with respect to the invention of the carbon fiber woven fabric for the fuel cell gas diffusion layer, in the carbon fiber woven fabric for the fuel cell gas diffusion layer formed by interweaving the warp and the weft, one of the warp and the weft is substantially untwisted. And. Further, on one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer, the number of untwisted yarns above the other yarn interwoven with the untwisted yarn is below the other yarn interwoven with the untwisted yarn. A carbon fiber woven fabric for a fuel cell gas diffusion layer, which is larger than the number of untwisted yarns.

Further, both the warp and the weft may be substantially untwisted. That is, in the carbon fiber woven fabric for the fuel cell gas diffusion layer formed by interweaving the warp and the weft, both the warp and the weft are substantially untwisted, and the warp is on one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer. Alternatively, one of the weft yarns may be a carbon fiber woven fabric for a fuel cell gas diffusion layer in which the number of yarns above the other yarn that is interwoven is larger than the number of yarns below the other yarn.

Further, the carbon fiber woven fabric for the fuel cell gas diffusion layer having a concave portion formed on the surface opposite to one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer described above may be used. Further, a carbon fiber woven fabric for a fuel cell gas diffusion layer in which the rigidity of the opposite surface on which the concave portion is formed is higher than the rigidity of the other one surface side may be used.

Regarding the invention of the fuel cell using the carbon fiber woven fabric for the fuel cell gas diffusion layer described above, the gas diffusion layer made of the carbon fiber woven fabric for the fuel cell gas diffusion layer and having a concave portion, and the separator having a plurality of grooves are used. A fuel cell cell comprising the A fuel cell having θ in the range of 10 ° or more and 35 ° or less was used.

Further, a fuel cell cell comprising a gas diffusion layer made of a carbon fiber woven fabric for a fuel cell gas diffusion layer and having a concave portion and a separator having a flat surface, and a surface having the concave portion of the gas diffusion layer. It may be a fuel cell in which the planes of the separator are in contact with each other.

In the present invention, the term "substantially untwisted yarn" refers to a sweet-twisted spun yarn in which yarn breakage occurs frequently in the weaving process, a spun yarn having a small number of twists so as not to become a yarn, or a long fiber having almost no twist. Suppose to say.

In the present invention, a carbon fiber woven fabric for a fuel cell gas diffusion layer formed by interweaving warp threads and weft threads, wherein at least one of the warp threads or the weft threads is substantially untwisted and carbon for the fuel cell gas diffusion layer. On one side of the textile fabric, the number of untwisted yarns above the other yarn interwoven with the untwisted yarn is greater than the number of untwisted yarns below the other yarn interwoven with the untwisted yarn. Carbon fiber woven fabric for use.

Membrane electrode assembly (MEA) on the surface side where the number of untwisted yarns above the other yarn interwoven with the untwisted yarn is greater than the number of untwisted yarns below the other yarn interwoven with the untwisted yarn By bringing the catalyst layers into contact with each other, the adhesion between the woven fabric and the catalyst layer of the membrane electrode assembly is improved. Since ion exchange is performed in the catalyst layer of the membrane electrode assembly, ion exchange and electron transfer are efficiently performed.

As a result, a sufficiently low electrical resistance can be realized to efficiently extract electrical energy. At the same time, the number of untwisted yarns on the other yarn that is interwoven with the untwisted yarn by contacting the untwisted yarn on the surface of the fabric with the catalyst layer of the membrane electrode assembly is the other that is interwoven with the untwisted yarn. It is also possible to flatten the surface under the yarn, which is larger than the number of untwisted yarns, and reduce the thickness while maintaining the action as a gas diffusion layer. Further, since it has a woven structure, the flexibility of absorbing dimensional variations in the thickness direction is improved as compared with carbon paper.

In addition, one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer (the number of untwisted yarns above the other yarn interwoven with the untwisted yarn is below the other yarn interwoven with the untwisted yarn). When a concave portion is formed on a surface opposite to the number of surfaces), the surface on which the concave portion is formed is brought into contact with the groove surface of the separator having a groove, so that a wider gas flow path is formed. Is formed.

As a result, the oxidant gas is supplied and diffused through this gas flow path, and at the same time, the water vapor generated in the catalyst layer of the membrane electrode assembly is quickly sucked out without clogging in the gas diffusion layer and discharged to the outside of the system. Therefore, a large current can be taken out. That is, in the large current region when the fuel cell is used, the inside of the fuel cell is in an overhumidified state, and good gas diffusion resistance can be obtained.

Further, the rigidity of the opposite surface (the surface in which the number of untwisted yarns above the other yarn interwoven with the untwisted yarn is greater than the number of untwisted yarns below the other yarn interwoven with the untwisted yarn) Also raise.

As a result, when the groove surface of the separator having a groove is brought into contact with the surface side forming the concave portion of the gas diffusion layer, the gas diffusion layer is prevented from entering the groove of the separator. As a result, a gas flow path is secured, and a high power generation capacity is maintained without impairing the ability to supply the oxidant gas or drain the generated water or the like.

Further, by forming a fuel cell in which the surface of the concave portion of the gas diffusion layer and the flat surface of the separator are in contact with each other, it is possible to realize a single cell of a thin fuel cell, which has a high power generation capacity and several hundreds. A fuel cell stack that can take out a large amount of power by combining a single cell can be realized with a thin weight, light weight, and low cost.

It is a schematic (perspective) figure which shows the weaving form of the carbon fiber woven fabric 1 which is one Embodiment of this invention. It is a woven structure diagram (in the case of twill weave) of the carbon fiber woven fabric 11 which shows one Embodiment of this invention when the warp yarn is substantially untwisted yarn. It is a weave structure diagram (in the case of satin weave) of the carbon fiber woven fabric 21 which shows one Embodiment of this invention when the warp yarn is substantially untwisted yarn. It is a woven structure diagram (in the case of warp ridge weave) of the carbon fiber woven fabric 31 which shows one Embodiment of this invention when the warp yarn is substantially untwisted yarn. FIG. 6 is a schematic cross-sectional view taken along the line AA of the carbon fiber woven fabric 31 shown in FIG. It is a schematic diagram which shows the method of measuring the rigidity of one side of a carbon fiber woven fabric. It is a schematic diagram which shows the state after pressurization to one side of the woven fabric in the method of measuring the rigidity of a carbon fiber woven fabric. It is a schematic diagram which shows the structure of the fuel cell 10 of this invention. It is a B arrow view of the grooved separator 5 shown in FIG. FIG. 8 is a view taken along the line A of the carbon fiber woven fabric 41 shown in FIG. It is a schematic diagram explaining the angle (intersection angle) θ at which the concave portion 4 of the carbon fiber woven fabric 41 and the groove 7 of the grooved separator 5 intersect. It is a schematic plan view of the test apparatus used for the water flow test of Example 2. FIG. 12 is a cross-sectional view taken along the line XX of the test apparatus used for the water flow test shown in FIG.

An example of the embodiment of the carbon fiber woven fabric for the fuel cell gas diffusion layer of the present invention will be described with reference to the drawings. FIG. 1 is a schematic (perspective) view showing a weaving form of a carbon fiber woven fabric 1 for a fuel cell gas diffusion layer (hereinafter referred to as “carbon fiber woven fabric 1”) according to an embodiment of the present invention. As shown in FIG. 1, the carbon fiber woven fabric 1 is a case where a plurality of warp threads 2 (2A to 2J) and weft threads 3 (3a to 3j) are interwoven by twill weaving.

The carbon fiber woven fabric 1 shown in FIG. 1 shows a case where the warp yarn 2 is a substantially untwisted yarn and the weft yarn 3 is a twisted yarn. As shown in FIG. 1, the twisted weft thread 3 has a shape whose cross section is relatively close to a circle. On the other hand, the weft 2 which is substantially untwisted has an elliptical cross section.

Next, in the relationship between one warp yarn 2A constituting the carbon fiber woven fabric 1 and a plurality of weft yarns 3A to 3J interwoven with the warp yarn 2A, one side (upper surface in FIG. 1) side will be focused on. As shown in FIG. 1, the warp yarn 2A, which is substantially untwisted yarn, first jumps over the warp yarn 3a and then passes under the two warp yarns 3b and 3c thereafter. Next, the warp 2A jumps over the three wefts 3d, 3e, and 3f, and then passes under the two wefts 3g and 3h in the same manner.

That is, when the carbon fiber woven fabric 1 of the present invention has the mixed weaving form shown in FIG. 1, the untwisted yarn (warp yarn 2) jumps over the three yarns (weft yarn) with respect to the other yarn (weft yarn 3). It is woven in a state where it keeps the regularity of passing under (down) two threads (weft) after that (up).

Therefore, on one side of the carbon fiber woven fabric 1, as shown in FIG. 1, the warp yarn 2A, which is a non-twisted yarn, is the other yarn (weft yarn) with respect to the other yarn (weft yarn 3a to 3j) interwoven with the warp yarn 2A. The number of untwisted yarns (warp yarns) on the top is larger than the number of untwisted yarns (warp yarns) below the other yarn (weft yarn) interwoven with the untwisted yarns (warp yarns). This regularity is the same for other warp threads 2B to 2J such as warp threads 2B.

When focusing on the warp threads 2 forming the carbon fiber woven fabric 1 of the present invention, the number of warp threads 2 jumping over the weft threads 3 or when focusing on the weft threads 3 forming the carbon fiber woven fabric 1. Can also refer to the number of weft threads 3 jumping over the warp threads 2 as the "floating number".

Next, another embodiment of the carbon fiber woven fabric 1 of the present invention will be described for each woven form. FIG. 2 is a woven structure diagram (in the case of twill weave) of the carbon fiber woven fabric 11 showing an embodiment of the present invention when the warp 12 is substantially untwisted, and FIG. 3 is a diagram in which the warp 22 is substantially untwisted. The woven structure diagram (in the case of Akiko weave) of the carbon fiber woven fabric 21 showing one embodiment of the present invention, FIG. 4 shows the carbon fiber showing one embodiment of the present invention when the warp 32 is substantially untwisted yarn. The woven structure diagram (in the case of vertical ridge weave) of the woven fabric 31 is shown respectively.

The weaving structure shown in FIG. 2 is the weaving structure of the carbon fiber woven fabric 11 when twill weaving is performed using a total of 100 threads of 10 warp threads (12A to 12J) and 10 weft threads (13a to 13j). Is. The black part in FIG. 2 shows the part where the warp thread 12 is woven (floating) above the weft thread 13, and the white part shows the part where the weft thread 13 is woven (floating) above the warp thread 12. ) Indicates the location. In the case of the woven structure (twill weave) shown in FIG. 2, the carbon fiber woven fabric 11 of the present invention has 60 warp threads 12 interwoven with respect to the weft threads 13, which are substantially untwisted. This is more than the number of warp threads 12 (40 threads) under the weft threads 13.

The weaving structure shown in FIG. 3 was interwoven by satin weaving using a total of 100 threads of 10 warp threads (22A to 22J) and 10 weft threads (23a to 23j), similarly to the weaving structure of FIG. This is the woven structure of the carbon fiber woven fabric 21 of the case. The black part in FIG. 3 shows the part where the warp 22 is woven (floating) above the weft 23 as in the case of FIG. 2, and the white part shows the weft 23 woven above the weft 22. Indicates a part that is rare (floating). In the case of the weaving structure shown in FIG. 3, the carbon fiber woven fabric 21 of the present invention has 80 warp threads 22 interwoven with respect to the weft threads 23, which are substantially untwisted. This is more than the number of warp threads 22 (20) below.

The woven structure shown in FIG. 4 is a carbon fiber when woven by warp ridge weaving using a total of 240 threads of 16 warp threads (32A to 32P) and 15 weft threads (33a to 33o). It is a woven structure of the woven fabric 31. The black part in FIG. 4 shows the part where the warp 32 is woven (floating) above the weft 33 as in the cases of FIGS. 2 and 3, and the white part shows the weft 33 above the warp 32. Indicates the woven (floating) part. In the case of the weaving structure shown in FIG. 4, the carbon fiber woven fabric 31 of the present invention has 168 warp threads 32 interwoven with respect to the weft threads 33, which are substantially untwisted. This is more than the number of warp threads 32 (72) below.

From the above, the case where one of the warp or weft that forms the carbon fiber fabric for the fuel cell gas diffusion layer is substantially untwisted has been described, but the carbon fiber fabric for the fuel cell gas diffusion layer of the present invention is the warp and the weft. Any of these may be substantially untwisted yarns. That is, in the carbon fiber woven fabric for the fuel cell gas diffusion layer formed by interweaving the warp and the weft, both the warp and the weft are substantially untwisted, and the warp is on one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer. Alternatively, the number of untwisted yarns above the other yarn in which one of the weft yarns is interwoven may be larger than the number of untwisted yarns below the other yarn interwoven with the untwisted yarn.

The weaving method of the carbon fiber woven fabric for the fuel cell gas diffusion layer of the present invention is a flat double weave in addition to the above-mentioned twill weave and satin weave, and the groove pattern is a vertical groove, a horizontal groove, a zigzag (stepped) groove, and an oblique weave. It may be a woven fabric in which spatially continuous grooves such as grooves are formed.

Further, the above-mentioned substantially untwisted yarn bundle appears on one side of the woven fabric, and the cross section of each yarn bundle becomes flat and spreads so as to increase the contact area with the catalyst surface of the membrane electrode assembly. A form that can be applied smoothly is desirable.

Further, in the case of twill weave, the warp / weft ratio (ratio of warp to weft) is preferably 2: 3 or 3: 4, and in the case of satin weave, 3, 4 or 5 satin weaves are preferable. Further, in the plain double weave, if the weft yarns are alternately driven with thick yarns and fine yarns such as 1/20 Nm and 1/100 Nm in metric count display, the uniform pitch of the warp yarns shifts as shown in FIG. It can also be a woven fabric (so-called warp ridged woven fabric) that forms grooves in the warp yarn direction.

Next, the structure of the concave portion provided on the carbon fiber woven fabric will be described with reference to FIG. FIG. 5 is a schematic cross-sectional view taken along the AA cutting line of the carbon fiber woven fabric 31 interwoven by the warp ridge weave shown in FIG. In the carbon fiber woven fabric 31 shown in FIG. 5, since the warp 32 is a non-twisted yarn as in the case of FIG. 4, the warp 32 has a relatively flat shape as shown in FIG. 5 when viewed from the AA cross-sectional direction. There is. Further, since the weft 33 is also a non-twisted yarn like the warp 32, its cross-sectional shape is substantially elliptical as in the case of the carbon fiber woven fabric 1 shown in FIG.

Then, in the carbon fiber woven fabric 31, wefts having a thickness difference of several times or more are alternately driven, and the thick and substantially untwisted weft is above one warp but below seven warps. It is a 7/1 satin weave, and the thin and substantially untwisted weft is a warp and a plain weave, so-called double weave.

As a result, the carbon fiber woven fabric 31 obtains a smooth surface suitable for the lower surface side shown in FIG. 5 to abut on the catalyst portion side of the membrane electrode assembly. Next, one surface (upper surface in FIG. 5) that comes into contact with the separator will be described. The lost fibers remaining in the raw machine (Kibata) are lost during firing shrinkage to form a gap, and the warp threads that are easily moved during shrinkage are brought closer to each other and disappear at regular intervals.

Therefore, the distance between the warp threads 32F and the warp thread 32H and the warp threads 32H and the warp threads 32J becomes wider than the other intervals, and the concave portion 4 (envelope portion indicated by the alternate long and short dash line) is formed, which is convenient in the warp thread direction. A carbon fiber woven fabric 31 is obtained. More importantly, since a large amount of warp (thick thread) 33 g or the like is present on the catalyst portion side of the membrane electrode assembly, the void ratio per unit thickness when sliced in the cross-sectional direction is the catalyst of the membrane electrode assembly. The separator side is larger than the partial side, and the water vapor generated on the catalyst partial side of the membrane electrode assembly is easily discharged to the separator side without dew condensation.

Next, the rigidity of the carbon fiber woven fabric of the present invention will be described. First, by applying the cured resin to one side or both sides of the carbon fiber woven fabric and drying it, the rigidity of the side to which the resin is applied can be increased as compared with before the resin is applied.

Specifically, for example, a liquid in which a resole-type thermosetting resin is dispersed is applied to one or both sides of a carbon fiber woven fabric, dried, and then compressed with a smooth plate in an inert gas atmosphere. By heating and cooling, the resin is cured while maintaining the gas supply, permeability, and gas diffusivity. At this time, the pressure is applied in the same manner as in the carbonization treatment, and the resin is fired in a temperature range of 600 ° C. to 1250 ° C. in which the resin has low resistance in an inert gas.

Water phenol is preferable as the resol type thermosetting resin, and water phenol ink or paste in which conductive carbon black or graphite is uniformly dispersed in distilled water can be used. Further, the coating method may be a gravure printing method, a doctor blade method, a spray spraying method, or a direct coating method using a die having a uniform mouthpiece width.

In either method, it is desirable that the increased weight of the carbon fibers after the dispersion is applied and heat-cured is in the range of 5 to 50% with respect to the weight of the carbon fiber woven fabric before the resin is applied. The cured resin to be applied to one side of the carbon fiber woven fabric is among cured resins such as PVA (polyvinyl alcohol), SBR (styrene / butadiene rubber), PVDF (polyvinylidene fluoride), and PTFE (polytetrafluoroethylene). Can be appropriately selected according to the required rigidity.

A method for measuring the rigidity of the carbon fiber woven fabric to which the resin is applied and cured by the above method will be described with reference to FIGS. 6 and 7. FIG. 6 is a schematic view showing a method of measuring the rigidity of one side of the carbon fiber woven fabric, and FIG. 7 is a schematic view showing a state after pressurization of the woven fabric to one side in the method of measuring the rigidity of the carbon fiber woven fabric.

Regarding the method of measuring the rigidity of the carbon fiber woven fabric of the present invention, as shown in FIG. 6, the carbon fiber woven fabric is placed on a flat block, and a U-shaped jig (grooved block) is placed above the carbon fiber woven fabric. : Groove width w) is pressurized with a predetermined pressure P. The carbon fiber woven fabric pressed by the U-shaped jig shows some floating in the U-shaped gap portion (groove portion) of the jig as shown in FIG. The degree of rigidity of the carbon fiber woven fabric is measured by measuring the amount of floating (the amount of penetration into the groove) δ of the carbon fiber woven fabric.

Next, an embodiment of the invention of the fuel cell 10 composed of the carbon fiber woven fabric 41 and the grooved separator 5 described above will be described with reference to FIGS. 8 to 11. 8 is a schematic view showing the configuration of the fuel cell 10 of the present invention, FIG. 9 is a view taken along the line B of the grooved separator 5 shown in FIG. 8, and FIG. 10 is a view taken along the line A of the carbon fiber woven fabric 41 shown in FIG. FIG. 11 is a schematic view illustrating an angle (intersection angle) θ at which the concave portion 4 of the carbon fiber woven fabric 41 and the groove 7 of the grooved separator 5 intersect. In FIG. 8, other components such as a polymer film and a catalyst layer existing between the carbon fiber woven fabric 41 and the membrane electrode assembly 8 are not shown.

As shown in FIG. 8, the fuel cell 10 of the present invention includes the carbon fiber woven fabric 41 described above, a grooved separator 5 in contact with the surface side of the carbon fiber woven fabric 41 having the concave portion 4, and the carbon fiber woven fabric. It is composed of a membrane electrode assembly 8 that is in contact with the surface side opposite to the surface side having the concave portion 4 of 41. As shown in FIG. 9, a plurality of grooves 7 of the grooved separator 5 are provided in the vertical direction. On the other hand, a plurality of recessed portions 4 of the carbon fiber woven fabric 41 are provided in an oblique direction.

Therefore, when the carbon fiber woven fabric 41 and the grooved separator 5 are used as the fuel cell 10 and these members are overlapped with each other, the concave portion 4 of the carbon fiber woven fabric 41 is the grooved separator 5 as shown in FIG. It is configured with an angle θ with respect to the groove 7. In other words, the fuel cell 10 is formed by contacting the carbon fiber woven fabric 41 and the grooved separator 5 with an angle (intersection angle) θ formed by the concave portion 4 and the groove 7. .. This angle θ is preferably 10 ° or more and 35 ° or less from the viewpoint of improving the gas diffusion resistance value, which is one of the characteristics of the fuel cell 10.

A fuel cell (hereinafter referred to as "cell") was produced using each GDL of the material of the present invention and the comparative material, and the power generation performance of the cell was measured. The measurement result will be described. The GDL used for this measurement will be described. 2 types of the present invention materials (the present invention materials 1 and 2) and 2 types of the comparative materials (comparative materials 1 and 2). It is a GDL (a weaving method in which the warp threads pass under the two weft threads after passing over the three weft threads), and only the warp threads are substantially untwisted. Further, the material 2 of the present invention is the invention. Similar to the material 1, the twill weave GDL shown in FIGS. 1 and 2 is used, and both the warp and the weft are assumed to be substantially untwisted.

On the other hand, the comparative material 1 is a GDL of the same yarn as the material 1 of the present invention and a plain weave with the same pitch (a weaving method in which one warp goes over one weft and then passes under one weft). Therefore, it was assumed that only the warp threads were substantially untwisted. The comparative material 2 is a plain weave GDL having the same yarn as the material 2 of the present invention and having the same pitch, and both the warp and the weft are substantially untwisted. Table 1 shows the characteristics of each GDL (material of the present invention and comparative material) used in this measurement.

Next, the structure of the cell used in this measurement will be described. In the cell used for this measurement, a polymer membrane (electrolyte membrane: thickness 20 μm) is placed in the center, and catalyst layers (density 0.6 mg / cm ² ) are brought into close contact with both sides of the anode and cathode, and then GDL. Was arranged, and then a separator (with a straight groove) was attached to the outermost side in a form adjacent to each GDL.

The GDL used in this cell is SGL's GDL (product number: SGL24BC) for the hydrogen electrode (anode side), and the above-mentioned material of the present invention or comparative material (electrode area is 1 cm for each) for the air electrode (cathode side). ^{It was set} as each GDL of 2). The thickness of each GDL incorporated in the cell of this measurement was unified in the range of 100 to 150 μm.

To the above cell, pure hydrogen was pumped to the hydrogen electrode and air diluted with nitrogen was pumped to the air electrode at a flow rate of 1 L / min, and at the same time, both the hydrogen electrode and the air electrode had a gas humidification temperature of 55 ° C. The operating conditions of the cell were set so that the gas was supplied to the cell where the temperature of the power generation unit was 45 ° C. and the conditions were over-humidified. The average back pressure of both poles in this cell was 0.15 MPa (abs). The IV (current-voltage) characteristic of the cell was measured under the above conditions, and the gas diffusion resistance value (GDR) was calculated from Equation 1 with the current value when the voltage was 0.2 V as the limit current value.

In addition, this formula 1 was the same calculation formula as that disclosed in the specification of the prior art (Japanese Patent Laid-Open No. 2010-027510). Further, in the following equation, F: Faraday constant, R: gas constant, and Pav: average absolute pressure at the entrance and exit are shown.

After sufficiently performing the break-in operation common to each of the above cells, the limit current value ( _Ilim : A / cm ² ) of 0.2 V is obtained, and the gas diffusion resistance value (s / m) in overhumidification is determined. Calculated. As a result, the gas diffusion resistance value (GDR) of the cell using the material 1 of the present invention was 64 s / m, and the gas diffusion resistance value of the cell using the material 2 of the present invention was 68 s / m, and the material of the present invention was used. The gas diffusion resistance values of the cells were all lower than 70 s / m.

Here, "break-in operation" means improving the power generation capacity to a steady state while changing the power generation pattern (VI conditions and its time) and improving the familiarity between the polymer membrane, the catalyst layer, and the GDL. Therefore, it refers to the test run of the cell before the performance evaluation.

On the other hand, the gas diffusion resistance value of the cell using the comparative material 1 is 107 s / m, and the gas diffusion resistance value of the cell using the comparative material 2 is 109 s / m. The resistance values were all values exceeding 100 s / m.

From the above measurement results, one or both of the warp and weft yarns are substantially untwisted yarns, and one side of the carbon fiber woven fabric for the fuel cell gas diffusion layer is the other yarns interwoven with the untwisted yarns. By using a carbon fiber fabric (GDL) for a fuel cell gas diffusion layer in which the number of untwisted yarns on the top is larger than the number of untwisted yarns under the other yarn interwoven with the untwisted yarn, the one-sided side described above is used. A concave groove is formed on the surface opposite to the above.

As a result, by bringing the separator into contact with the surface on the opposite side, the water vapor generated in the cell (polymer membrane or catalyst layer) is quickly discharged to the outside of the cell through the concave groove of the GDL. More hydrogen gas and oxygen in the air could be taken into the cell, and the gas diffusion performance of the fuel cell could be improved.

Next, a water flow test was conducted to compare the flowability of the fluid (water) in each GDL of the material of the present invention and the comparative material. The GDL used in this test was the material 2 of the present invention and the comparative material 2 used in Example 1 (hereinafter, referred to as the material 3 of the present invention and the comparative material 3). A schematic plan view of the test apparatus used in this test is shown in FIG. 12, and a cross-sectional view taken along the line XX of FIG. 12 is shown in FIG.

As shown in FIGS. 12 and 13, this test apparatus is transparent from above with a GDL having a thickness of 0.1 mm, a width of 50 mm, and a length of 100 mm and a packing installed around the GDL on a steel pedestal. Seal the GDL with a resin plate and a steel holding plate. As shown in FIG. 13, the sealed GDL can confirm the water flow status of the GDL through a holding plate having an open central portion and a transparent resin plate. After that, tap water with a water pressure of 0.3 MPa is supplied from the pipe of this device (left side of the drawing), and the flow rate per unit time discharged from the pipe on the opposite side (right side of the drawing) is measured to determine the ease of water flow. Compared.

As a result of measuring the flow rate of tap water, the water flow rate of the test apparatus using the material 3 of the present invention was 38 cc per minute. On the other hand, the water flow rate of the test device using the comparative material 3 was 22 cc per minute. From the above measurement results, it was found that the material of the present invention has a structure that allows more fluid to pass through than the comparative material. Therefore, the GDL of the present invention can quickly discharge the water vapor generated in the cell to the outside of the cell even when it is in contact with the separator (whether or not there is a groove) in the cell.

Since the difference in the amount of deflection under a predetermined pressure was measured using the invention material and the comparative material, the measurement results will be described. In addition, since the same power generation performance as in Example 1 was measured using the same invention material and comparative material, the measurement results will also be described.

The GDL used for measuring the amount of deflection and the power generation performance of the GDL of this example is obtained by subjecting both sides of the material 1 of the present invention used in Example 1 as an invention material to a curing treatment (hereinafter referred to as the material 4 of the present invention). ) And as the comparative material, both sides of the comparative material 1 used in Example 1 were cured with a thermosetting resin (hereinafter referred to as the comparative material 4).

Regarding the curing treatment applied to both surfaces of the material 4 of the present invention and the comparative material 4, the material 1 of the present invention and the comparative material 1 used in Example 1 were subjected to a resol-type phenol aqueous solution (water in weight ratio: resol-type phenol resin = 100:). Soaked in (mixed at a ratio of 25), dried, and thermoset in an atmosphere of 200 ° C., and then further immersed in a PTFE solution (mixed at a ratio of water: PTFE = 100: 3 by weight). The material 4 of the present invention and the comparative material 4 were dried and heat-treated in an atmosphere of 340 ° C.

Next, a method for measuring the amount of deflection of GDL will be described. The above-mentioned GDL is installed on the flat block shown in FIG. 6, and the lift amount shown in FIG. 7 is pressed with a grooved block having a groove width (w) of 1 mm and a pressure (P) of 1.7 MPa from above. (Dimension of GDL that penetrated into the groove) δ was measured. The amount of lift δ of GDL was measured on both one side and the other side, respectively.

As a result of measuring the lift amount δ of the GDL using the material 4 of the present invention based on the above-mentioned measurement method, the lift amount δ1 = 81 μm on one side of the material 4 of the present invention, and the lift amount δ2 = 43 μm on the opposite side. there were. Here, with respect to one side surface of the material 4 of the present invention, only the warp threads are substantially untwisted, and the number of warp threads above the weft threads is larger than the number of warp threads below the weft threads (three warp threads are present). Refers to the surface that passes under the two weft threads after getting over the weft threads.

That is, since the amount of carbon fibers exposed on one side of the material 4 of the present invention is larger than that on the opposite side, it is considered that the floating amount δ1 of GDL is also larger than the floating amount δ2 on the opposite side. .. On the other hand, a concave groove is formed in the GDL on the opposite side of the surface as described above. Therefore, since the amount of carbon fibers exposed on one side is smaller than that on the opposite side, it is considered that the floating amount δ2 of GDL is smaller than the floating amount δ1 on the one side.

On the other hand, as a result of measuring the lift amount δ of GDL using the comparative material 4, the lift amounts δ1 and δ2 on both sides were both 54 μm, which were the same values. It is considered that this is because the weaving method of the comparative material 4 is a plain weave on both sides, and there is no difference in the expression form of the warp and the weft on either side.

Next, the power generation performance was measured using the same GDLs of the material 4 of the present invention and the comparative material 4 as in the case of Example 1, and the measurement results will be described. Since the cell structure used in this measurement and the basis for measuring and calculating the gas diffusion resistance value are the same as in the case of the first embodiment, detailed description thereof will be omitted.

The gas diffusion resistance value (GDR) of the cell using GDL of the material 4 of the present invention was 53 s / m. On the other hand, the gas diffusion resistance value of the cell using the comparative material 4 was 151 s / m in (GDR), which was almost three times the resistance value of the GDL of the material 4 of the present invention. The gas diffusion resistance value of the material 4 of the present invention is any of the measurement results of the materials 1 and 2 of the present invention (material 1 = 64 s / m, material 2 = 68 s / m) used in the measurement of Example 1. It exceeded the result.

From the above measurement results of the amount of deflection and the measurement result of the power generation performance (gas diffusion resistance value), a concave groove is formed on one surface depending on the form of the GDL weaving of the invention material 4, and thus hardened on that surface. By applying the treatment, the rigidity of the GDL itself could be increased. As a result, even when the GDL and the separator come into contact with each other, it is possible to prevent the carbon fibers of the GDL from entering the groove of the separator and prevent the flow of hydrogen gas and air flowing through the groove of the separator. The power generation efficiency of the battery can be improved.

1, 11, 21, 31, 41 (for fuel cell gas diffusion layer) Carbon fiber woven fabric 2, 12, 22, 32 Warp 3, 13, 23, 33 Weft 4 Recessed portion 5 (grooved) Separator 7 Separator 5 Groove 8 Membrane electrode assembly 10 Fuel cell cell θ Crossing angle

Claims (6)

A carbon fiber woven fabric for a fuel cell gas diffusion layer formed by interweaving warp threads and weft threads, wherein one of the warp threads or the weft threads is substantially untwisted and comes into contact with the catalyst layer of the membrane electrode joint. one surface of the fuel cell gas diffusion layer carbon fiber fabric make, said the other being non-twist yarns and interweaving the number of non-twist yarns made on the yarn of the non-twist yarns made under the other yarns A carbon fiber woven fabric for a fuel cell gas diffusion layer, which is characterized in that the number is larger than the number. A carbon fiber woven fabric for a fuel cell gas diffusion layer formed by interweaving warp threads and weft threads, wherein both the warp threads and the weft threads are substantially untwisted threads, and the fuel is brought into contact with the catalyst layer of the membrane electrode assembly. On one side of the carbon fiber fabric for the battery gas diffusion layer, the number of threads of either the warp or the weft above the other interwoven yarn is greater than the number below the other yarn. A carbon fiber fabric for a fuel cell gas diffusion layer, which is characterized by a large number of fibers. The carbon fiber fabric for a fuel cell gas diffusion layer according to claim 1 or 2, wherein a recess is formed on the other surface of the carbon fiber fabric for the fuel cell gas diffusion layer. The other rigid surfaces, fuel cell gas diffusion layer for carbon fiber woven fabric according to claim 3, wherein the higher than the rigidity of said one surface. A fuel cell cell comprising the carbon fiber woven fabric for the fuel cell gas diffusion layer according to claim 3 or 4, having the gas diffusion layer having the concave portion and the separator having a plurality of grooves, and the gas diffusion. The surface having the concave portion of the layer and the surface having the groove portion of the separator are in contact with each other, and the angle θ formed by the concave portion of the gas diffusion layer and the groove portion of the separator is 10 ° or more and 35 ° or less. A fuel cell that is characterized by being in the range of. The fuel cell according to claim 3 or 4, further comprising a gas diffusion layer made of the carbon fiber woven fabric for the fuel cell gas diffusion layer and having the concave portion and a separator having a flat surface, wherein the gas diffusion layer is provided. A fuel cell in which a surface having a concave portion and a flat surface of the separator are in contact with each other.

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