Gas diffusion layer of fuel cell and preparation method thereof

Abstract

The present application discloses a gas diffusion layer of a fuel cell thinned by integrally forming a substrate and a fine pore layer and a method for preparing the same. The gas diffusion layer of a fuel cell constituting a unit cell of the fuel cell comprises: a substrate layer formed by impregnating a first slurry mixed with carbon powder and polytetrafluoroethylene (PTFE) inside a carbon fiber substrate; and a fine pore layer formed by coating a second slurry mixed with carbon powder and polytetrafluoroethylene (PTFE) having a higher viscosity than the first slurry on the surface of the substrate layer.

Description

Technical Field

[0001] The present disclosure relates to a gas diffusion layer of a fuel cell and a method for preparing the same, and more particularly, to a gas diffusion layer that can be thinned by integrally forming a substrate and a fine pore layer and a method for preparing the same. Background Art

[0002] A fuel cell is a power generation device that converts the chemical energy of a fuel into electrical energy by utilizing an electrochemical reaction in a cell stack. It can be used not only to provide driving power for industry, homes, and vehicles, but also to provide power for portable devices and small electronic products. Recently, as a highly efficient and clean energy source, the application areas of fuel cells are expanding.

[0003] Figure 1 is a view showing a unit cell of a conventional fuel cell. Figure 2 is a cross-sectional view showing a gas diffusion layer of a conventional fuel cell.

[0004] like Figure 1 As shown, in a unit cell of a conventional fuel cell, a membrane-electrode assembly (MEA) 10 is located at the innermost side, and the membrane-electrode assembly includes a polymer electrolyte membrane 11 that can enable hydrogen ions (protons) to move, and catalyst layers coated on two opposite surfaces of the electrolyte membrane that allow hydrogen and oxygen to react with each other, namely, an anode layer 12 and a cathode layer 13.

[0005] In addition, a gas diffusion layer (GDL) 20 is stacked on the outside of the membrane electrode assembly 10, that is, on the outside of the membrane electrode assembly 10 where the anode layer 12 and the cathode layer 13 are located, and a separator plate 30 is formed on the outside of the gas diffusion layer 20. The separator plate 30 has a flow field for supplying fuel and discharging water generated by the reaction.

[0006] At this time, if Figure 2 As shown, the gas diffusion layer 20 is formed by forming a fine-porous layer (microporous layer: MPL) on a substrate 21 made of carbon fibers.

[0007] In addition, the matrix 21 is generally formed by impregnating a hydrophobic agent such as polytetrafluoroethylene (PTFE) in carbon fibers, and the carbon fibers may be in the form of carbon fiber cloth, carbon fiber felt, and carbon fiber pager, for example.

[0008] In addition, after preparing the fine porous layer 22 by mixing carbon powder including carbon black, acetylene black carbon and black pearls carbon with a hydrophobic substance such as polytetrafluoroethylene (PTFE), the fine porous layer 22 can be coated on one surface or both opposite surfaces of the substrate 21 according to the purpose.

[0009] At the same time, hydrogen ions and electrons are generated in the anode layer 12 through the oxidation reaction of hydrogen. The hydrogen ions and electrons generated at this time move to the cathode layer 13 through the polymer electrolyte membrane 11 and the wires respectively. In the cathode layer 13, water is generated through the electrochemical reaction of protons and electrons moved from the anode layer 12 with oxygen in the air, and electrical energy is generated at the same time by the flow of electrons.

[0010] Furthermore, the gaseous reaction gas supplied to the fuel cell and liquid water generated by the chemical reaction are discharged while moving from the cathode layer 13 of the membrane electrode assembly 10 toward the fine pore layer 22 of the gas diffusion layer 20 , the substrate 21 , and the separator plate 30 .

[0011] Meanwhile, a method of reducing the cell pitch (cell interval) to increase the output density of a fuel cell stack has been studied, and thus attempts have been made to reduce the thickness of individual products constituting the cell.

[0012] For example, a method of reducing the thickness of a substrate serving as a substrate coated with a fine porous layer to thin the gas diffusion layer is being attempted.

[0013] In particular, recently, since porous separator plates have been used to improve the diffusion performance of the reaction gas supplied to the battery and to effectively discharge the generated water, and when the porous separator plates are used, the reaction gas is supplied from the separator plates to the gas diffusion layer by forced convection, thereby reducing the importance of the function of the matrix of the gas diffusion layer.

[0014] However, since the fine porous layer constituting the gas diffusion layer cannot form a layer itself, it is difficult to remove the substrate to make the gas diffusion layer thinner.

[0015] The contents described as the background art are provided only to enhance the understanding of the background of the present disclosure and should not be construed as admitting that the contents correspond to conventional techniques known to those skilled in the art to which the present disclosure belongs. Summary of the invention

[0016] The present disclosure provides a gas diffusion layer of a fuel cell and a method for preparing the same, wherein a substrate and the fine pore layer are integrally formed by impregnating a slurry for forming a fine pore layer into the interior of a substrate, rather than removing the substrate, to make the gas diffusion layer thinner.

[0017] According to one aspect of the present disclosure, a gas diffusion layer of a fuel cell constituting a unit cell of the fuel cell includes: a substrate layer formed by impregnating a first slurry mixed with carbon powder and polytetrafluoroethylene (PTFE) into an interior of a carbon fiber substrate; and a fine pore layer formed by coating a second slurry mixed with carbon powder and polytetrafluoroethylene (PTFE) having a higher viscosity than the first slurry on a surface of the substrate layer.

[0018] The first slurry impregnated in the interior of the base layer may be impregnated in the entire area of ​​the base layer.

[0019] The first slurry impregnated inside the matrix layer may be impregnated inside the matrix layer in a predetermined pattern, and the pattern of the first slurry impregnated in the matrix layer is a pattern corresponding to a region facing the lands in the channels and lands formed in the separator plates constituting the unit cells of the fuel cell.

[0020] The first slurry impregnated inside the substrate layer can be impregnated in the entire area of ​​the substrate layer, and when the first slurry is impregnated inside the substrate layer, a predetermined pattern of the first slurry impregnated inside the substrate layer can be divided into a high-density pattern of impregnating a relatively large amount of the first slurry and a low-density pattern of impregnating a relatively small amount of the first slurry, and the high-density pattern of the pattern of the first slurry impregnated inside the substrate layer can be a pattern corresponding to an area facing the platform in the platform and the channel formed in the separation plate of the unit cell constituting the fuel cell.

[0021] Based on the thickness direction of the base layer, the base layer can be divided into a high-density region impregnated with a relatively large amount of the first slurry and a low-density region impregnated with a relatively small amount of the first slurry.

[0022] The gas diffusion layer of the fuel cell can be classified into a low-humidity gas diffusion layer and a high-humidity gas diffusion layer. The low-humidity gas diffusion layer can have a fine porous layer on the surface of a low-density area formed in the substrate layer, and the high-humidity gas diffusion layer can have a fine porous layer on the surface of a high-density area formed in the substrate layer.

[0023] The thickness of the base layer may be 50 μm to 80 μm, and the thickness of the fine pore layer may be 20 μm to 40 μm.

[0024] The solid content of the first slurry may be 5% to 10%, and the solid content of the second slurry may be 10% to 15%.

[0025] Cerium oxide may be further mixed in any one or both of the first slurry and the second slurry.

[0026] According to one aspect of the present disclosure, there is provided a method for preparing a gas diffusion layer of a unit cell constituting a fuel cell, the method comprising: a substrate preparation step of preparing a substrate by using carbon fiber; a slurry preparation step of preparing a first slurry with relatively low viscosity and a second slurry with relatively high viscosity by mixing carbon powder and polytetrafluoroethylene (PTFE); a substrate layer forming step of forming a substrate layer by impregnating the first slurry into the interior of the substrate; and a fine pore layer forming step of forming a fine pore layer by coating the second slurry on the surface of the substrate layer.

[0027] The slurry preparation step may include preparing a first slurry by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the first slurry is 5% to 10%, thereby making the viscosity of the first slurry 10000cps to 100000cps; and preparing a second slurry by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the second slurry is 10% to 15%, thereby making the viscosity of the second slurry 100000cps to 500000cps.

[0028] The matrix preparing step may include preparing the matrix by using only carbon fibers, and the matrix layer forming step includes impregnating the first slurry in the entire area of ​​the interior of the matrix by applying the first slurry on one surface of the matrix and then sucking the first slurry from an opposite surface of the matrix.

[0029] The base layer forming step may include forming the base layer by adjusting the suction amount of the first slurry so that the base layer is divided into a high density region impregnated with a relatively large amount of carbon powder and a low density region impregnated with a relatively small amount of carbon powder based on the thickness direction of the base layer.

[0030] The gas diffusion layer of the fuel cell can be classified into a low-humidity gas diffusion layer and a high-humidity gas diffusion layer, and the fine pore layer forming step may include: when preparing the low-humidity gas diffusion layer, forming the fine pore layer by coating the second slurry on the surface of the low-density area formed in the substrate layer; when preparing the high-humidity gas diffusion layer, forming the fine pore layer by coating the second slurry on the surface of the high-density area formed in the substrate layer.

[0031] The substrate preparation step may include preparing the substrate by using only carbon fiber, and the substrate layer forming step may include: after setting a mask having through holes in a predetermined pattern on one surface of the substrate, applying the first slurry on the surface of the substrate, and impregnating the first slurry in the interior of the substrate in a predetermined pattern by sucking the first slurry from the opposite surface of the substrate, and the predetermined pattern formed in the mask may be a pattern corresponding to an area facing the platform in a platform and a channel formed in a separator of a unit cell constituting a fuel cell.

[0032] The method may further include, after the fine pore layer forming step, a sintering step of sintering the carbon powder and polytetrafluoroethylene (PTFE) included in the first slurry and the second slurry by heat treatment.

[0033] According to an embodiment of the present disclosure, since the base layer and the fine pore layer are integrally formed by impregnating a slurry for forming the fine pore layer into the interior of the base layer and coating the same or similar kind of slurry on the surface of the base layer, the rigidity of the gas diffusion layer can be maintained while the thickness of the gas diffusion layer can be thinned.

[0034] In addition, since the base layer is formed by impregnating the interior of the carbon fiber matrix with a slurry including carbon powder, the slurry including carbon powder is filled in the pores between the carbon fiber matrixes, thereby making it easy to ensure the rigidity of the base layer itself, and since the bonding force between the base layer and the fine pore layer is improved, peeling of the base layer and the fine pore layer can be prevented.

[0035] In addition, carbon powder may be further impregnated in the carbon fiber matrix forming the matrix, thereby ensuring excellent electrical conductivity of the gas diffusion layer.

[0036] Furthermore, according to the present disclosure, generally, when a base layer is provided to form a gas diffusion layer, a process of separately impregnating PTFE in a carbon fiber base and performing a heat treatment can be omitted.

[0037] Furthermore, when the slurry is impregnated inside the base layer, since the slurry is impregnated in a predetermined pattern, the discharge efficiency of the generated water can be adjusted. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and other aspects, features and advantages of the present disclosure will become more apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

[0039] Figure 1 is a view showing a unit cell of a conventional fuel cell;

[0040] Figure 2 is a cross-sectional view showing a gas diffusion layer of a conventional fuel cell;

[0041] Figure 3 is a cross-sectional view showing a gas diffusion layer of a fuel cell according to an embodiment of the present disclosure;

[0042] Figure 4 is a view showing a process of preparing a gas diffusion layer of a fuel cell according to an embodiment of the present disclosure;

[0043] Figure 5A and Figure 5B is a view showing a process of preparing a gas diffusion layer of a fuel cell according to another embodiment of the present disclosure;

[0044] Figure 6 is a view showing a stacked state of a gas diffusion layer and a separator plate of a fuel cell according to another embodiment of the present disclosure; and

[0045] Fig. 7A and Figure 7B is a view illustrating a gas diffusion layer of a fuel cell and a process of preparing the gas diffusion layer of the fuel cell according to still another embodiment of the present disclosure. DETAILED DESCRIPTION

[0046] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the present disclosure is not limited to the embodiments disclosed below, but can be implemented in various different forms, and the embodiments only make the disclosure of the present disclosure complete, and are provided to fully inform the scope of the present disclosure to those of ordinary skill in the art. In the accompanying drawings, the same reference numerals represent the same elements.

[0047] Figure 3 is a cross-sectional view showing a gas diffusion layer of a fuel cell according to an embodiment of the present disclosure. Figure 4 is a diagram illustrating a process of preparing a gas diffusion layer of a fuel cell according to an embodiment of the present disclosure.

[0048] As shown in the accompanying drawings, the gas diffusion layer 100 of the fuel cell according to an embodiment of the present disclosure includes: a substrate layer 110, which is formed by impregnating a first slurry S1 mixed with carbon powder and polytetrafluoroethylene (PTFE) into the interior of a carbon fiber substrate; and a pore layer 120, which is formed by coating a second slurry S2 mixed with carbon powder and polytetrafluoroethylene (PTFE) and having a higher viscosity than the first slurry S1 on the surface of the substrate layer 110.

[0049] The base layer 110 is formed by impregnating the first slurry S1 inside the base 111 made of carbon fiber. At this time, the base 111 is configured to impregnate the first slurry S1 mixed with carbon powder and polytetrafluoroethylene (PTFE) inside the base 111 made only of carbon fiber. Therefore, the rigidity of the base layer 110 itself can be ensured by filling the pores formed between the carbon fibers with carbon powder and PTFE.

[0050] Meanwhile, the carbon fiber used for the base 111 constituting the base layer 110 may be in the form of carbon fiber cloth, carbon fiber felt, and carbon fiber paper.

[0051] In addition, the carbon powder constituting the first slurry may be carbon black, acetylene carbon black, black pearl carbon, etc., used alone or in combination. In the embodiment, carbon black is used as the carbon powder.

[0052] The fine pore layer 120 is formed by coating the second slurry S2 on the surface of the base layer 110. At this time, the composition of the second slurry S2 is the same as or similar to that of the first slurry S1, but the first slurry S1 and the second slurry S2 have different solid contents.

[0053] For example, since the first slurry S1 needs to be impregnated inside the substrate 111, the first slurry S1 is kept at a low viscosity by reducing the solid content of the first slurry S1. Meanwhile, since the second slurry S2 is coated on the surface of the substrate layer 110, the second slurry S2 is kept at a high viscosity by increasing the solid content of the second slurry S2, thereby enhancing the function of the gas diffusion layer.

[0054] Preferably, the first slurry S1 is prepared by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the first slurry S1 is 5% to 10%, so that the viscosity of the first slurry S1 is 10000cps to 100000cps. In addition, the second slurry S2 is prepared by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the second slurry S2 is 10% to 15%, so that the viscosity of the second slurry S2 is 100000cps to 500000cps. Then, the solvent for forming the first slurry S1 and the second slurry S2 may include isopropyl alcohol (IPA), n-propyl alcohol (NPA) and deionized water (DI water). In addition, the first slurry S1 and the second slurry S2 may further include a dispersant so that the carbon powder and PTFE can be uniformly dispersed in the solvent.

[0055] In addition, the first slurry S1 and the second slurry S2 may further include cerium oxide as a hydrogen peroxide decomposition catalyst. At this time, cerium oxide may be included in both the first slurry S1 and the second slurry S2, or may be included in any one selected from the first slurry S1 and the second slurry S2.

[0056] At the same time, the first slurry S1 prepared with the same or similar components as the second slurry S2 constituting the pore layer 120 is impregnated into the interior of the base layer 110, and the base layer 110 and the pore layer 120 are integrally formed by coating the second slurry S2 on the surface of the base layer 110 to form the pore layer 120, so that the rigidity of the gas diffusion layer can be maintained while the thickness of the gas diffusion layer can be thinned.

[0057] For example, the thickness of the base layer 110 may be 50 μm to 80 μm, and the thickness of the pore layer 120 may be 20 μm to 40 μm. In this way, the thickness of the base layer 110 is thinner than the thickness of a conventional general base (about 260 μm to 270 μm), but due to the influence of the first slurry S1 entirely impregnated inside the base layer 110, the rigidity of the base layer 110 can be maintained at a desired level.

[0058] A method of manufacturing the above-mentioned gas diffusion layer will be described with reference to the accompanying drawings.

[0059] The method for preparing a gas diffusion layer of a fuel cell according to the present disclosure includes: a substrate preparation step of preparing a substrate 111 by using carbon fibers; a slurry preparation step of preparing a first slurry S1 having a relatively low viscosity and a second slurry S2 having a higher viscosity than the first slurry S1; a substrate layer formation step of forming a substrate layer 110 by impregnating the first slurry S1 inside the substrate 111; and a fine pore layer formation step of forming a fine pore layer 120 by coating the second slurry S2 on the surface of the substrate layer 110. In addition, after the fine pore layer formation step, a sintering step of sintering the carbon powder and PTFE included in the first slurry S1 and the second slurry S2 by heat treatment is further included.

[0060] In the substrate preparation step, the substrate 111 is prepared by using carbon fibers as in the conventional art. However, in the conventional art, after the substrate 111 is prepared by using carbon fibers, a hydrophobic substance such as polytetrafluoroethylene (PTFE) is impregnated to impart hydrophobicity to the substrate 111, but in the present embodiment, hydrophobicity is imparted to the substrate 111 by impregnating the first slurry in the substrate layer formation step, so that hydrophobicity is not imparted to the substrate 111 alone in the substrate preparation step. Therefore, the substrate 111 is prepared by using only carbon fibers in the substrate preparation step. For example, the substrate 111 may be in the form of carbon fiber cloth, carbon fiber felt, carbon fiber paper, or the like.

[0061] The slurry preparation step is a step of preparing the first slurry S1 and the second slurry S2 constituting the base layer 110 and the pore layer 120, and the first slurry S1 and the second slurry S2 have the same composition, but the first slurry S1 and the second slurry S2 have different solid contents so that the viscosity of the first slurry S1 and the second slurry S2 is different.

[0062] For example, since the first slurry S1 needs to be impregnated inside the substrate 111, the first slurry S1 is kept at a low viscosity by reducing the solid content of the first slurry S1. To this end, the first slurry S1 is prepared by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the first slurry S1 is 5% to 10%, thereby making the viscosity of the first slurry S1 10000 cps to 100000 cps.

[0063] At the same time, since the second slurry S2 is coated on the surface of the base layer 110, the second slurry S2 is kept at a high viscosity by relatively increasing the solid content of the second slurry S2, thereby enhancing the function of the gas diffusion layer. To this end, the second slurry S2 is prepared by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the second slurry S2 is 10% to 15%, thereby making the viscosity of the second slurry S2 100000 cps to 500000 cps.

[0064] At this time, the solvent used to form the first slurry S1 and the second slurry S2 may use IPA, NPA and deionized water. In addition, the first slurry S1 and the second slurry S2 may further include a dispersant so that the carbon powder and PTFE can be uniformly dispersed in the solvent.

[0065] The base layer forming step is a step of forming the base layer 110 by impregnating the first slurry S1 into the interior of the base 111, and the first slurry S1 is impregnated into the entire area of ​​the interior of the base 111 by applying the first slurry S1 to one surface of the prepared base 111 and then sucking the first slurry S1 from the opposite surface of the base 111.

[0066] For example, Figure 4 As shown, in a state where the substrate 111 is prepared in a roll shape, the substrate 111 is moved while being unrolled, the first slurry S1 is supplied to one surface of the substrate 111 on a moving path of the substrate 111, and the first slurry S1 supplied by the scraper 1 is applied to a predetermined thickness. In this state, when the first slurry S1 is sucked by using the suction device 2 provided on the opposite surface of the substrate, the first slurry S1 is impregnated into the inside of the substrate 111 while being dispersed.

[0067] The pore layer forming step is a step of forming the pore layer 120 by applying the prepared second slurry S2 on the surface of the base layer 110 , and the second slurry S2 is applied to the surface of the base layer 110 formed by impregnating the first slurry S1 inside the base 111 .

[0068] For example, Figure 4As shown, a pool 3 containing the second slurry S2 and a coating roller 4 installed in the pool 3 to apply the second slurry S2 contained in the pool 3 to the base layer 110 are provided on a path where the base layer 110 formed by immersing the first slurry S1 inside the base 111 continuously moves. Therefore, while the base layer 110 moves in close contact with the coating roller 4, a predetermined amount of the second slurry S2 is coated on the surface of the base layer 110 by the coating roller 4.

[0069] In this way, when the fine porous layer 120 is coated on the surface of the base layer 110, the carbon powder and PTFE included in the first slurry S1 and the second slurry S2 are sintered by heat treatment. Here, heat treatment refers to heating the PTFE to a temperature above the melting point of PTFE (about 350°C). Therefore, when the fine porous layer 120 is sintered, the dispersion performance of the PTFE included in the first slurry S1 and the second slurry S2 is improved. Here, sintering refers to a process in which the PTFE particles are melted by heating the slurry mixed with carbon powder and PTFE, and the PTFE having fluidity is evenly dispersed in the entire area of ​​the slurry.

[0070] The gas diffusion layer according to the present disclosure prepared as described above can effectively discharge the generated water compared to a conventional general gas diffusion layer.

[0071] The reason is that, Figure 2 The conventional general gas diffusion layer 20 shown is formed by forming a fine pore layer 22 (microporous layer: MPL) on a substrate 21 made of carbon fiber. At this time, in order to form the fine pore layer 22, a slurry in which carbon powder and a hydrophobic substance such as polytetrafluoroethylene (PTFE) are mixed is applied to the surface of the substrate 21, and a part of the applied slurry penetrates into the surface of the substrate at a predetermined depth. Therefore, the conventional gas diffusion layer 20 should sequentially pass through three regions including the fine pore layer, the substrate penetrated by the fine pore layer, and the substrate to discharge the generated water.

[0072] However, since the gas diffusion layer 100 according to the present disclosure is configured to impregnate the first slurry S1 inside the base layer 110 , it is only necessary to sequentially pass through two regions including the fine pore layer and the base layer impregnated with the first slurry to discharge the generated water.

[0073] In this way, the gas diffusion layer 100 according to the present disclosure can reduce the number of steps of channels through which the generated water is discharged and reduce the resistance of the path through which the generated water is discharged, compared with the conventional general gas diffusion layer 20, thereby smoothly discharging the generated water.

[0074] In addition, the conventional general gas diffusion layer 20 is configured such that the carbon fibers constituting the substrate 21 form a plurality of layers, and at this time, microscopically unoccupied spaces are formed between the carbon fiber layers. Therefore, there is no medium between the carbon fiber layers for moving the generated water in the thickness direction of the substrate 21, and therefore, when the generated water is discharged in the thickness direction of the substrate, the generated water temporarily stays between the carbon fiber layers constituting the substrate 21. Therefore, the efficiency of the generated water flowing in the thickness direction of the substrate 21 is reduced.

[0075] However, in the gas diffusion layer 100 according to the present disclosure, the first slurry S1 is impregnated between the carbon fiber layers constituting the base layer 110 and serves as a medium for moving the generated water.

[0076] Therefore, even if the generated water is discharged in the thickness direction of the base layer 110, the generated water does not remain between the carbon fiber layers as in the conventional technology, and the first slurry S1 can flow smoothly as a medium. Therefore, the efficiency of the generated water flowing in the thickness direction of the base is improved.

[0077] Meanwhile, the present disclosure may improve the discharge efficiency of generated water by forming a pattern at a position where the first slurry is impregnated in the substrate.

[0078] Figure 5A and Figure 5B is a view showing a process of preparing a gas diffusion layer of a fuel cell according to another embodiment of the present disclosure. Figure 6 is a view showing a stacked state of a gas diffusion layer and a separator plate of a fuel cell according to another embodiment of the present disclosure.

[0079] Similar to the gas diffusion layer of the above-described embodiment, a gas diffusion layer 200 of a fuel cell according to another embodiment of the present disclosure includes a base layer 210 and a fine pore layer 220 .

[0080] However, the base layer 210 restricts the position of the first slurry S1 impregnated therein to form a predetermined pattern in a region where the first slurry S1 is impregnated.

[0081] For example, Figure 6 As shown, the pattern formed by impregnating the first slurry S1 in the base layer 210 is a pattern corresponding to the lands 31 and the areas facing the lands 31 in the channels 32 formed in the separator plate 30 constituting the unit cells of the fuel cell.

[0082] Therefore, the base layer 210 is configured to form a predetermined pattern in the area 212 where a relatively large amount of the first slurry S1 is impregnated in the base 211. Therefore, the hydrophobicity of the area facing the platform 31 of the separation plate 30 can be increased by increasing the density of the first slurry S1 impregnated in the area to prevent water from accumulating in the corresponding area. Therefore, by guiding the flow of the generated water to the area opposite to the channel 32 of the separation plate 30, the generated water can be smoothly discharged through the channel 32 of the separation plate 30.

[0083] At the same time, if Figure 5B As shown, the base layer 210 can be divided into an area 212 in which the first slurry S1 is impregnated while limiting the position of the first slurry S1 impregnated inside the base layer 210 and an area 211 in which the first slurry S1 is not impregnated, but the present disclosure is not limited thereto, and the base layer 210 can be divided into an area in which the first slurry S1 is impregnated in the entire area inside the base layer 210 but a relatively large amount of the first slurry S1 is impregnated and an area in which a relatively small amount of the first slurry S1 is impregnated.

[0084] For example, the amount of the first slurry S1 impregnated inside the base layer 210 may be varied by using a predetermined pattern, and may be divided into a high-density pattern (corresponding to Figure 6 212) and a low-density pattern (corresponding to Figure 6 211).

[0085] Therefore, if Figure 6 As shown, similar to the case where the area 212 impregnated with the first slurry S1 and the area 211 not impregnated with the first slurry S1 are divided, it can be divided into a high-density pattern and a low-density pattern. At this time, the high-density pattern in which the first slurry S1 is impregnated in the base layer 210 is a pattern corresponding to the area facing the platform 31 in the channel 32 formed in the separation plate 30 of the unit cell constituting the fuel cell.

[0086] Therefore, by guiding the flow of the generated water to the area opposite to the channel 32 of the separation plate 30 , the generated water is smoothly discharged through the channel 32 of the separation plate 30 .

[0087] A method of manufacturing a gas diffusion layer according to another embodiment of the present disclosure as described above will be described with reference to the accompanying drawings.

[0088] The method for preparing a gas diffusion layer according to another embodiment of the present disclosure as in the above-mentioned embodiment includes a substrate preparation step, a slurry preparation step, a substrate layer formation step, and a fine pore layer formation step. In addition, a sintering step is further included after the fine pore layer formation step. At this time, the substrate preparation step, the slurry preparation step, the fine pore layer formation step, and the sintering step are performed in the same manner as the above steps.

[0089] Furthermore, even in the base layer forming step, the first slurry S1 is impregnated inside the base 211 by applying the first slurry S1 on one surface of the base 211 and sucking the first slurry S1 from the opposite surface of the base 211. However, before applying the first slurry S1, a mask 5 having through holes of a predetermined pattern is provided on one surface of the base 211, and then the first slurry S1 is applied to the surface.

[0090] Therefore, if the first slurry S1 is sucked from the opposite surface of the base 211 , while the first slurry S1 is impregnated inside the base 211 , the region 212 impregnated with a relatively large amount of the first slurry S1 is formed to have a predetermined pattern corresponding to the pattern of the through holes formed in the mask 5 .

[0091] At this time, the predetermined pattern of through holes formed in the mask 5 is a pattern corresponding to the lands 31 formed in the separator plate 30 constituting the unit cells of the fuel cell and the regions facing the lands 31 in the channels 32 .

[0092] Therefore, if Figure 5B As shown, the base layer 210 is configured to form a predetermined pattern in a region 212 where a relatively large amount of the first slurry S1 is impregnated in the base 211. Then, other regions of the base layer 210 except the region 212 where a large amount of the first slurry S1 is impregnated may be completely excluded from the impregnation of the first slurry S1, but may be impregnated with a relatively small amount of the first slurry S1 due to the characteristics of the preparation process.

[0093] Meanwhile, the present disclosure may be implemented by dividing the gas diffusion layer into a low-humidity gas diffusion layer and a high-humidity diffusion layer.

[0094] Fig. 7A and Figure 7B is a view showing a process of preparing a gas diffusion layer of a fuel cell according to still another embodiment of the present disclosure.

[0095] Fig. 7A is a view showing a low humidity gas diffusion layer for a low humidity environment, and Figure 7B is a view showing a high humidity gas diffusion layer used in a high humidity environment.

[0096] Like the above-described embodiment, a gas diffusion layer according to still another embodiment of the present disclosure includes base layers 110 and 310 and fine pore layers 120 and 320 .

[0097] At this time, the base layers 110 and 310 are divided into high-density regions 111 and 311 impregnated with a relatively large amount of the first slurry S1 and low-density regions 112 and 312 impregnated with a relatively small amount of the first slurry S1 based on the thickness direction of the base layers 110 and 310 .

[0098] Therefore, if Fig. 7A As shown, the low humidity diffusion layer for a low humidity environment is configured to form a fine pore layer 120 on the surface of a low density region 112 formed in a base layer 110 .

[0099] In order to prepare the low humidity gas diffusion layer, first, in the step of forming the base layer 110, based on the thickness direction of the base, a high density region 111 impregnated with a relatively large amount of the first slurry S1 is formed at the upper part of the base and a low density region 112 impregnated with a relatively small amount of the first slurry S1 is formed at the lower part of the base. In addition, when the base layer 110 passes through the coating roller 4 to be coated with the second slurry S2, the low density region 112 moves toward the coating roller 4, thereby forming a fine pore layer 120 on the low density region 112 of the base layer 110.

[0100] In addition, if Figure 7B As shown, the high humidity diffusion layer for a high humidity environment is configured to form a fine pore layer 320 on the surface of a high density region 311 formed in a base layer 310 .

[0101] In order to prepare the high humidity gas diffusion layer, first, in the step of forming the base layer 310, a high density region 311 impregnated with a relatively large amount of the first slurry S1 is formed at the upper part of the base and a low density region 312 impregnated with a relatively small amount of the first slurry S1 is formed at the lower part of the base, based on the thickness direction of the base. In addition, when the base layer 310 passes through the coating roller 4 to be coated with the second slurry S2, the base layer 310 is turned over so that the high density region 311 moves facing the coating roller 4, thereby forming a fine pore layer 320 on the high density region 311 of the base layer 310. In order to turn over the base layer 310 while the base layer 310 is moving, conveying rollers 6 and 7 may be provided at the front and rear ends of the coating roller 4.

[0102] Although the present disclosure is described with reference to the preferred embodiments, the present disclosure is not limited thereto but is defined by the appended claims. Therefore, those skilled in the art may make various modifications and changes to the present disclosure without departing from the technical concept of the appended claims.

Claims

1. A gas diffusion layer of a fuel cell constituting a unit cell of a fuel cell, comprising: The substrate layer is formed by impregnating a first slurry mixed with carbon powder and polytetrafluoroethylene (PTFE) into the interior of the carbon fiber substrate; as well as The fine-porous layer is formed by coating a second slurry which is a mixture of carbon powder and polytetrafluoroethylene (PTFE) and has a higher viscosity than the first slurry on the surface of the base layer, wherein, when the first slurry is impregnated into the interior of the base layer, a predetermined pattern in which the first slurry is impregnated into the interior of the base layer is divided into a high-density pattern in which a relatively large amount of the first slurry is impregnated and a low-density pattern in which a relatively small amount of the first slurry is impregnated, and The high-density pattern of the pattern in which the first slurry is impregnated inside the base layer is a pattern corresponding to a region facing the lands among lands and channels formed in a separator plate constituting the unit cells of the fuel cell.

2. The gas diffusion layer according to claim 1, wherein: The first slurry impregnated in the interior of the base layer is impregnated in the entire area of ​​the base layer.

3. The gas diffusion layer according to claim 1, wherein: Based on the thickness direction of the base layer, the base layer is divided into a high-density region impregnated with a relatively large amount of the first slurry and a low-density region impregnated with a relatively small amount of the first slurry.

4. The gas diffusion layer according to claim 3, wherein: The gas diffusion layer of the fuel cell is classified into a low humidity gas diffusion layer and a high humidity gas diffusion layer, The low-humidity gas diffusion layer has the fine pore layer on the surface of the low-density region formed in the base layer, and The high-humidity gas diffusion layer has the fine pore layer on the surface of the high-density region formed in the base layer.

5. The gas diffusion layer according to claim 1, wherein: The thickness of the base layer is 50 μm to 80 μm, and The thickness of the fine pore layer is 20 μm to 40 μm.

6. The gas diffusion layer according to claim 1, wherein: The solid content of the first slurry is 5% to 10%, and The second slurry has a solid content of 10% to 15%.

7. The gas diffusion layer according to claim 1, wherein: Cerium oxide is further mixed in either or both of the first slurry and the second slurry.

8. A method for preparing a gas diffusion layer constituting a unit cell of a fuel cell according to claim 1, comprising: A matrix preparation step, preparing the matrix by using carbon fibers; A slurry preparation step, preparing a first slurry with relatively low viscosity and a second slurry with relatively high viscosity by mixing carbon powder and polytetrafluoroethylene (PTFE); a base layer forming step of forming a base layer by impregnating the first slurry into the interior of the base; as well as The fine pore layer forming step forms a fine pore layer by coating the second slurry on the surface of the base layer.

9. The method according to claim 8, wherein: The slurry preparation step comprises: preparing the first slurry by mixing carbon powder and polytetrafluoroethylene (PTFE) with a solvent so that the solid content of the first slurry is 5% to 10% and the viscosity of the first slurry is 10000 cps to 100000 cps; and The second slurry is prepared by mixing carbon powder and polytetrafluoroethylene (PTFE) with the solvent such that the solid content of the second slurry is 10% to 15% and the viscosity of the second slurry is 100,000 cps to 500,000 cps.

10. The method according to claim 8, wherein: The matrix preparation step comprises: The matrix is ​​prepared by using only the carbon fibers, and The base layer forming step comprises: The first slurry is impregnated in the entire area of ​​the interior of the substrate by sucking the first slurry from the opposite surface of the substrate after coating the first slurry on one surface of the substrate.

11. The method according to claim 10, wherein: The base layer forming step comprises: The base layer is formed by adjusting the suction amount of the first slurry so that the base layer is divided into a high-density region impregnated with a relatively large amount of carbon powder and a low-density region impregnated with a relatively small amount of carbon powder based on the thickness direction of the base layer.

12. The method according to claim 11, wherein: The gas diffusion layer of the fuel cell is classified into a low humidity gas diffusion layer and a high humidity gas diffusion layer, The pore layer forming step comprises: When preparing the low-humidity gas diffusion layer, the fine pore layer is formed by coating the second slurry on the surface of the low-density region formed in the base layer; and When the high-humidity gas diffusion layer is prepared, the fine pore layer is formed by coating the second slurry on the surface of the high-density region formed in the base layer.

13. The method according to claim 8, wherein: The matrix preparation step comprises: By preparing the matrix using only the carbon fibers, The base layer forming step comprises: After a mask having through holes in a predetermined pattern is disposed on one surface of the substrate, the first slurry is coated on the surface of the substrate, and the first slurry is impregnated into the interior of the substrate in the predetermined pattern by sucking the first slurry from an opposite surface of the substrate, and The predetermined pattern formed in the mask is a pattern corresponding to a region facing the lands among the channels and lands formed in the separator plates constituting the unit cells of the fuel cell.

14. The method according to claim 8, further comprising: After the fine pore layer forming step, a sintering step is performed in which the carbon powder and polytetrafluoroethylene (PTFE) included in the first slurry and the second slurry are sintered by heat treatment.

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