Membrane-electrode assembly and method for manufacturing the same

Abstract

Disclosed is a membrane-electrode assembly having improved adhesion and interface durability between a polymer electrolyte membrane and an electrode, and a manufacturing method of a membrane-electrode assembly, in which, in forming an electrode by directly coating a catalyst slurry on a polymer electrolyte membrane, the adhesion and interface durability between the polymer electrolyte membrane and the electrode can be improved without a separate additional step, thereby improving both the durability and productivity of the membrane-electrode assembly. The manufacturing method includes the steps of dispersing a catalyst and an ion conductor in a dispersion medium to obtain a catalyst slurry; coating the catalyst slurry onto a polymer electrolyte membrane; and drying the catalyst slurry coated onto the polymer electrolyte membrane to form an electrode. The dispersion medium is a solvent capable of forming a plurality of grooves on the surface of the polymer electrolyte membrane, and, when the electrode is formed by the drying step, at least some of the grooves are filled with the catalyst, the ion conductor, or a mixture thereof.

Description

Technical Field

[0001] This disclosure relates to a method for manufacturing a membrane-electrode assembly, and more specifically, to a membrane-electrode assembly having improved adhesion strength between the polymer electrolyte membrane and the electrode and improved durability of the interface therebetween, and a method for manufacturing a membrane-electrode assembly that enables the direct coating of a catalyst slurry onto the polymer electrolyte membrane to form the electrode, thereby improving the adhesion strength between the polymer electrolyte membrane and the electrode and the durability of the interface therebetween without any separate additional processes, thereby improving both the durability and productivity of the membrane-electrode assembly. Background Technology

[0002] Polymer electrolyte membrane fuel cells (PEMFCs) are configured to generate electricity using a structure in which stacked cell units (each cell unit includes a membrane electrode assembly (MEA) and a separator (also known as a bipolar plate)) are attracting attention as a next-generation energy source capable of replacing fossil fuels due to their high energy efficiency and environmentally friendly characteristics.

[0003] A membrane-electrode assembly typically includes an anode (also known as a fuel electrode), a cathode (also known as an air electrode), and a polymer electrolyte membrane disposed therebetween.

[0004] When fuel such as hydrogen is supplied to the anode, hydrogen ions (H+) are generated at the anode due to the oxidation reaction of hydrogen. + ) and electrons (e - The generated hydrogen ions are transferred to the cathode through the polymer electrolyte membrane, while the generated electrons are transferred to the cathode through an external circuit. Oxygen supplied to the cathode combines with the hydrogen ions and electrons, resulting in the formation of water through reduction.

[0005] Due to long-term operation of fuel cells, the low durability of the interface between the polymer electrolyte membrane and the electrode leads to performance degradation of the membrane-electrode assembly. This low durability is caused by insufficient adhesive strength between the polymer electrolyte membrane and the electrode.

[0006] To improve the adhesion strength between the polymer electrolyte membrane and the electrode, it has been proposed to use (i) physical methods, such as embossing, sanding, sandblasting or rubbing, or (ii) physical and chemical methods, such as plasma treatment or corona discharge treatment, to form irregularities on the surface of the polymer electrolyte membrane to improve its surface roughness.

[0007] However, the above method is not preferred in terms of process simplicity and limits the improvement of membrane-electrode assembly productivity because it requires a separate additional process to provide surface roughness for the polymer electrolyte membrane. Furthermore, the adhesion strength between the polymer electrolyte membrane and the electrode in the membrane-electrode assembly manufactured using the above method is insufficient, thus failing to ensure satisfactory interface durability. Summary of the Invention

[0008] Technical problem

[0009] Therefore, this disclosure relates to a membrane-electrode assembly and a method for manufacturing the same, which can solve the problems caused by the limitations and disadvantages of the aforementioned related technologies.

[0010] One object of this disclosure is to provide a membrane-electrode assembly having improved adhesion strength between the polymer electrolyte membrane and the electrode, as well as improved durability of the interface therebetween.

[0011] Another object of this disclosure is to provide a method for manufacturing a membrane-electrode assembly that enables the direct coating of a catalyst slurry onto a polymer electrolyte membrane to form an electrode, thereby improving the adhesion strength between the polymer electrolyte membrane and the electrode, as well as the durability of the interface therebetween, without any separate additional processes, thereby improving both the durability and productivity of the membrane-electrode assembly.

[0012] In addition to the objectives described above, other features and advantages of this disclosure will be described below, or will be readily understood by those skilled in the art from the following description of this specification.

[0013] Technical solution

[0014] According to one aspect of this disclosure, a membrane-electrode assembly is provided, comprising: a polymer electrolyte membrane; and a first electrode on a first surface of the polymer electrolyte membrane, wherein the first electrode includes a first catalyst and a first ion conductor, and a plurality of grooves are randomly formed on the first surface, each groove having a depth of less than 5 μm and a width of less than 10 μm, each groove being filled by a portion of the first electrode, and the content of the first ion conductor in the portion of the first electrode filling the groove is higher than the content of the first ion conductor in the remaining portion of the first electrode.

[0015] The difference between the content of the first ion conductor in the portion of the first electrode that fills the groove and the content of the first ion conductor in the remaining portion of the first electrode can be 2% to 12% of the content of the first ion conductor in the remaining portion of the first electrode.

[0016] According to another aspect of this disclosure, a method for manufacturing a membrane-electrode assembly is provided, comprising: dispersing a first catalyst and a first ionic conductor in a first dispersion medium to obtain a first catalyst slurry; coating the first catalyst slurry onto a first surface of a polymer electrolyte membrane; and drying the first catalyst slurry coated on the first surface to form a first electrode, wherein the first dispersion medium comprises: (i) a first component capable of partially dissolving the polymer electrolyte membrane at its first surface or causing deformation of the first surface to form a plurality of grooves on the first surface; and (ii) a second component different from the first component, wherein the first component is an alcohol, acetic acid, propionic acid, etc. The first catalyst slurry contains dimethylacetamide or a mixture of two or more thereof, wherein the alcohol is methanol, ethanol, propanol, ethoxyethanol, butanol or a mixture of two or more thereof, the second component is water, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF) or a mixture of two or more thereof, the first dispersion medium in the first catalyst slurry contains 83% to 98% by weight, the first component in the first dispersion medium contains 55% to 80% by weight, and when the first electrode is formed by the drying step, at least some of the grooves are filled with the first catalyst, the first ionic conductor or a mixture thereof.

[0017] The first catalyst slurry can be coated on the first surface with a coating thickness of 10 μm to 200 μm.

[0018] The drying step can be carried out at a temperature of 50°C to 150°C for 10 to 300 seconds.

[0019] The content of (i) the first dispersion medium in the first catalyst slurry, (ii) the content of the first component in the first dispersion medium, (iii) the coating thickness of the first catalyst slurry, (iv) the temperature of the drying step, and (v) the time of the drying step can be set such that each groove has a depth of less than 5 μm and a width of less than 10 μm.

[0020] The dispersion step can be performed using at least one selected from ultrasonic homogenizers, ball mills, roller mills, resonant acoustic mixers, high-pressure homogenizers, planetary mixers, and homogenizers.

[0021] The polymer electrolyte membrane may contain fluorine-based ionic conductors.

[0022] The drying process can be carried out by hot air drying, infrared drying, or hot plate drying.

[0023] The method may further include: after forming the first electrode, coating a second catalyst slurry on a second surface of the polymer electrolyte membrane opposite to the first surface, and drying the second catalyst slurry coated on the second surface to form the second electrode.

[0024] The step of coating the first catalyst slurry onto the first surface can be performed simultaneously with attaching the protective film to the second surface of the polymer electrolyte membrane.

[0025] The method may further include removing a protective film from the second surface before coating the second catalyst slurry onto the second surface.

[0026] The method may further include attaching a first protective sheet to the first surface on which the first electrode is formed before removing the protective film from the second surface.

[0027] The method may further include attaching a second protective sheet to a second surface on which a second electrode is formed.

[0028] The method may further include: attaching a first mask film having a first window to the first surface before coating the first catalyst slurry onto the first surface; removing the first mask film after forming the first electrode; attaching a second mask film having a second window to the second surface before coating the second catalyst slurry onto the second surface; and removing the second mask film after forming the second electrode, wherein the step of coating the first catalyst slurry onto the first surface can be performed by coating the first catalyst slurry onto the portion of the first surface exposed through the first window, and the step of coating the second catalyst slurry onto the second surface can be performed by coating the second catalyst slurry onto the portion of the second surface exposed through the second window.

[0029] The general description of this disclosure given above is for illustrative purposes only and does not limit the scope of the rights granted by this disclosure.

[0030] Beneficial effects

[0031] According to this disclosure, grooves of predetermined size randomly arranged on the surface of a polymer electrolyte membrane are filled with a portion of an electrode formed on that surface. As a result, the adhesive strength between the polymer electrolyte membrane and the electrode can be higher than that of conventional technologies. Therefore, a membrane-electrode assembly with higher durability of the interface between the polymer electrolyte membrane and the electrode than conventional technologies can be provided.

[0032] Traditional physical or physicochemical methods for improving the adhesion strength between the polymer electrolyte membrane and the electrode to enhance the durability of the interface degrade process simplicity and the productivity of membrane-electrode assemblies. However, the method for manufacturing the membrane-electrode assembly according to this disclosure allows for the direct coating of a catalyst slurry onto the polymer electrolyte membrane to form the electrode, improving the adhesion strength between the polymer electrolyte membrane and the electrode and the durability of the interface without separate additional processes. Therefore, the method according to this disclosure allows for the relatively simple and highly productive manufacture of membrane-electrode assemblies with excellent durability. Attached Figure Description

[0033] The accompanying drawings, which are included and incorporated in and form part of this specification to aid in understanding this disclosure, illustrate embodiments of the disclosure and, together with the detailed description of the disclosure, serve to illustrate the principles of the disclosure.

[0034] Fig. 1a to Fig. 1c The process of forming an electrode on a polymer electrolyte membrane according to the method of this disclosure is schematically illustrated;

[0035] Fig. 2 A method for manufacturing a membrane-electrode assembly according to one embodiment of the present disclosure is illustrated schematically;

[0036] Fig. 3 (a) and Fig. 3 (b) A method for manufacturing a membrane-electrode assembly according to another embodiment of the present disclosure is illustrated schematically;

[0037] Fig. 4 A method for manufacturing a membrane-electrode assembly according to yet another embodiment of the present disclosure is illustrated schematically;

[0038] Fig. 5 This is an optical micrograph showing the surface of the membrane-electrode assembly obtained in Example 1;

[0039] Fig. 6 (a) and Fig. 6 (b) are scanning electron micrographs showing the surface and cross-section of the membrane-electrode assembly obtained in Example 1, respectively;

[0040] Fig. 7 This is a graph showing the H2 permeation measured during 20,000 wet / dry cycles on the membrane-electrode assembly obtained in Example 1;

[0041] Fig. 8 (a) and Fig. 8 (b) is a graph showing the voltage retention and H2 permeation measured during 500 hours of OCV retention on the membrane-electrode assembly obtained in Example 1. Detailed Implementation

[0042] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. However, the following exemplary embodiments are provided only for a clear understanding of the contents of this disclosure and do not limit the scope of this disclosure.

[0043] Fig. 1a to Fig. 1c The process of forming an electrode on a polymer electrolyte membrane according to the method of this disclosure is illustrated schematically.

[0044] like Fig. 1a As shown, the method for manufacturing a membrane-electrode assembly according to this disclosure includes the step of coating a first catalyst slurry 210a onto a first surface of a polymer electrolyte membrane 100.

[0045] According to this disclosure, a first catalyst 211 and a first ion conductor 212 are dispersed in a first dispersion medium 213 to obtain a first catalyst slurry 210a. A portion 212a of the first ion conductor 212 is coated on at least a portion of the first catalyst 211, and the remaining portion 212b exists as a free ion conductor not coated on the first catalyst 211.

[0046] The first catalyst 211 may include a support 211a and a plurality of catalyst metal particles 211b dispersed on the support 211a.

[0047] The support 211a may be: (i) a carbon-based support; (ii) a porous inorganic oxide support, such as zirconium oxide, alumina, titanium dioxide, silicon dioxide or cerium dioxide; or (iii) a zeolite support.

[0048] For example, carbon-based supports can be graphite, conductive carbon black (super P), carbon fiber, carbon sheet, carbon black, Ketjen black, Denka black, carbon nanotubes (CNT), carbon spheres, carbon ribbons, fullerenes, activated carbon, carbon nanofibers, carbon nanowires, carbon nanospheres, carbon nanoangles, carbon nanocages, carbon nanorings, ordered nano / mesoporous carbon, carbon aerogels, mesoporous carbon, graphene, stable carbon, activated carbon, or combinations of two or more of them.

[0049] The catalyst metal particles 211b may include platinum or platinum-based alloys. Platinum-based alloys may be: (i) binary alloys, such as Pt-Co, Pt-Pd, Pt-Mn, Pt-Sn, Pt-Mo, Pt-Cr, Pt-W, Pt-Ir, Pt-Ru, Pt-Ni, or Pt-Fe; (ii) ternary alloys, such as Pt-Ru-W, Pt-Ru-Ni, Pt-Ru-Mo, Pt-Ru-Ir, Pt-Co-Mn, Pt-Co-Ni, Pt- Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni-Ir, or Pt-Cr-Ir; or (iii) quaternary alloys, such as Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, or Pt-Ru-Ir-Ni. However, this disclosure is not limited thereto.

[0050] The first ion conductor 212, dispersed together with the first catalyst 211 in the first dispersion medium 213, not only performs the hydrogen ion transfer function in the first electrode 210b, but also functions as an adhesive to increase the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b.

[0051] The first ionic conductor 212 can be a fluorine or hydrocarbon ionic conductor with an ion exchange group. The ion exchange group can be at least one proton exchange group selected from sulfonic acid group, carboxyl group, borate group, phosphate group, imide group, sulfonimide group, sulfonamide group and sulfonyl fluoride group.

[0052] Examples of fluorine-based ionic conductors include poly(perfluorosulfonic acid) and poly(perfluorocarboxylic acid). However, this disclosure is not limited thereto.

[0053] Examples of hydrocarbon ionic conductors include sulfonated polyimide (S-PI), sulfonated polyaryl ether sulfone (S-PAES), sulfonated polyether ether ketone (SPEEK), sulfonated polybenzimidazole (SPBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene ether, sulfonated polyether sulfone, sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfonate, sulfonated polyphenylene sulfide sulfonate nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile, and sulfonated polyarylene ether sulfone ketone. However, this disclosure is not limited thereto.

[0054] According to this disclosure, the first dispersion medium 213 is a solvent that partially and slightly removes the polymer electrolyte membrane 100 from the first surface or causes deformation of the first surface, such as wrinkling, thereby forming a plurality of grooves on the first surface. The term "groove" as used herein includes the concept of angular grooves, curved grooves, or mixed grooves caused by partial removal of the polymer electrolyte membrane 100 or surface deformation such as wrinkling.

[0055] For example, the first dispersion medium 213 may comprise: (i) a first component, such as an alcohol, acetic acid, propionic acid, dimethylacetamide, or a mixture of two or more thereof; and (ii) a second component different from the first component, such as water, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), or a mixture of two or more thereof. The alcohol may be methanol, ethanol, propanol, ethoxyethanol, butanol, or a mixture of two or more thereof.

[0056] The content of the first dispersion medium 213 in the first catalyst slurry 210a can be from 83% to 98% by weight. If the content of the first dispersion medium 213 deviates from the above-specified range, it will be difficult to form grooves on the surface of the polymer electrolyte membrane 100.

[0057] The content of the first component in the first dispersion medium 213 may be from 55% to 80% by weight.

[0058] The first catalyst 211 and the first ion conductor 212 can be dispersed in the first dispersion medium 213 using at least one selected from ultrasonic homogenizers, ball mills, roller mills, resonant acoustic mixers, high-pressure homogenizers, planetary mixers, and homogenizers.

[0059] The polymer electrolyte membrane 100 includes an ion conductor. Since the aforementioned specified ion conductors, which can be used to form the first catalyst slurry 210a, can also be used in the polymer electrolyte membrane 100, a detailed description of the ion conductors used in the polymer electrolyte membrane 100 will be omitted. The ion conductors included in the polymer electrolyte membrane 100 may be the same as or different from the first ion conductor 212 of the first catalyst slurry 210a.

[0060] According to this disclosure, in order to effectively form a plurality of grooves G on the first surface of the polymer electrolyte membrane 100 using the first dispersion medium 213 (i.e., to sufficiently increase the roughness of the first surface), the polymer electrolyte membrane 100 may preferably contain fluorine-based ionic conductors rather than hydrocarbon-based ionic conductors. However, some of the above-specified examples of the first component of the first dispersion medium 213 (e.g., dimethylacetamide) can sufficiently increase the surface roughness of hydrocarbon-based polymer electrolyte membranes, just as fluorine-based polymer electrolyte membranes do.

[0061] The polymer electrolyte membrane 100 may be: (i) a single membrane made essentially of only ion conductors, or (ii) a reinforced composite membrane configured such that the pores of the porous support are filled with ion conductors.

[0062] The reinforced composite membrane may include: two pure layers made essentially of only ionic conductors; and a coexisting layer in which a porous support and an ionic conductor exist. In the reinforced composite membrane type polymer electrolyte membrane 100, the apparent volume of the porous support (i.e., the volume of the coexisting layer) can be from 5% to 90% of the total volume of the polymer electrolyte membrane 100.

[0063] According to this disclosure, the first dispersion medium 213 contains 55% to 80% by weight of a first component (i.e., alcohol, acetic acid, propionic acid, dimethylacetamide, or a mixture of two or more thereof) that can partially and slightly remove the ionic conductors of the polymer electrolyte membrane 100 or cause surface deformation of the polymer electrolyte membrane, such as wrinkling. Fig. 1b As shown, multiple grooves G can be irregularly formed on the first surface of the polymer electrolyte membrane 100, thereby increasing the surface roughness of the polymer electrolyte membrane.

[0064] As mentioned above, the alcohol can be methanol, ethanol, propanol, ethoxyethanol, butanol, or a mixture of two or more of them.

[0065] The content of the first component in the first dispersion medium 213 may be from 55% to 80% by weight.

[0066] If the content of the first component in the first dispersion medium 213 is less than 55% by weight, it is difficult to form grooves on the surface of the polymer electrolyte membrane 100. Therefore, the surface roughness of the polymer electrolyte membrane 100 cannot be sufficiently increased. As a result, the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b, as well as the durability of the interface therebetween, cannot be sufficiently improved.

[0067] On the other hand, if the content of the first component in the first dispersion medium 213 is greater than 80% by weight, the ionic conductors of the polymer electrolyte membrane 100 are excessively removed or excessive surface deformation, such as wrinkling, is caused in the polymer electrolyte membrane 100. As a result, excessively large grooves (i.e., each groove has a depth greater than 5 μm and a width greater than 10 μm) are formed on the surface of the polymer electrolyte membrane 100. Therefore, the durability of the polymer electrolyte membrane 100 may be unintentionally reduced, or interfacial bonding defects may occur.

[0068] The second component, which is another component of the first dispersion medium 213 according to this disclosure, can be any component of a catalyst slurry commonly used in the manufacture of membrane-electrode assemblies, such as (i) a hydrophilic solvent including water (H2O); and / or (ii) an organic solvent selected from N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), and mixtures of two or more of them.

[0069] In one embodiment of this disclosure, the first catalyst slurry 210a may be coated on the first surface of the polymer electrolyte membrane 100 to a coating thickness of 10 μm to 200 μm, more specifically 20 μm to 200 μm.

[0070] If the coating thickness of the first catalyst slurry 210a is less than 10 μm, the surface roughness and electrode loading of the polymer electrolyte membrane 100 cannot be sufficiently increased. As a result, the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b and the durability of their interface cannot be sufficiently improved. On the other hand, if the coating thickness of the first catalyst slurry 210a is greater than 200 μm, the first dispersion medium 213 of the first catalyst slurry 210a cannot be completely removed during the subsequent drying process. This not only causes electrode formation defects but also adversely affects subsequent processes. Furthermore, excessive removal of the ionic conductors of the polymer electrolyte membrane 100 by the first dispersion medium 213, or excessive surface deformation of the polymer electrolyte membrane such as wrinkling (or the formation of excessively large grooves), may unintentionally reduce the durability of the polymer electrolyte membrane 100 or cause electrode formation defects.

[0071] In this disclosure, there are no particular limitations on the method of coating the first catalyst slurry 210a on the first surface of the polymer electrolyte membrane 100, as long as the coating thickness of the first catalyst slurry 210a can be controlled within the range specified above. For example, coating methods such as slot die coating, comma coating, or spray coating can be used.

[0072] Subsequently, the first catalyst slurry 210a, coated on the first surface of the polymer electrolyte membrane 100 according to the present disclosure, is dried to form the first electrode 210b. The drying step can be performed by hot air drying, infrared drying, or hot plate drying.

[0073] When the first electrode 210b is formed through the drying step, as Fig. 1c As shown, at least a portion of the groove G is filled with a first catalyst 211, a first ion conductor 212, or a mixture thereof.

[0074] As a result, according to this disclosure, the contact area between the first electrode 210b and the polymer electrolyte membrane 100 is increased. That is, the first catalyst slurry 210a is directly coated onto the polymer electrolyte membrane 100 to form the first electrode 210b, and the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b, as well as the durability of the interface therebetween, can be improved without additional processing. Therefore, according to this disclosure, both the durability and productivity of the membrane-electrode assembly can be improved.

[0075] Furthermore, according to this disclosure, since a plurality of grooves G are formed on the first surface of the polymer electrolyte membrane 100 when the first electrode 210b is formed using the first catalyst slurry 210a, the portion of the first electrode 210b filling the grooves G and the remaining portion thereof differ from each other in terms of the content of the first ion conductor 212. Specifically, the content of the first ion conductor 212 in the portion of the first electrode 210b filling the grooves G is higher than the content of the first ion conductor in the remaining portion of the first electrode 210b (e.g., 2% to 12% higher than the content of the first ion conductor 210 in the remaining portion).

[0076] In one embodiment of this disclosure, the drying step of removing the first dispersion medium 213 from the first catalyst slurry 210a can be carried out at a temperature of 50°C to 150°C, more specifically 50°C to 130°C, for 10 to 300 seconds, more specifically 10 to 200 seconds.

[0077] If the drying step is performed at a temperature below 50°C, the first dispersion medium 213 cannot be completely removed, resulting in electrode formation defects and adversely affecting subsequent processes. Furthermore, the residual first dispersion medium 213 penetrates too deeply into the polymer electrolyte membrane 100, thereby excessively removing the ionic conductors of the polymer electrolyte membrane 100, or causing excessive surface deformation of the polymer electrolyte membrane, such as wrinkling (or the formation of excessively large grooves), which reduces the durability of the polymer electrolyte membrane 100 or causes electrode formation defects. On the other hand, if the drying step is performed at a temperature above 150°C, the first dispersion medium 213 evaporates rapidly, thus failing to adequately remove the ionic conductors from the polymer electrolyte membrane 100 or achieve sufficient surface deformation of the polymer electrolyte membrane, such as wrinkling, caused by the first dispersion medium 213. Therefore, the surface roughness of the polymer electrolyte membrane 100 cannot be adequately increased. Consequently, the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b, as well as the durability of their interface, cannot be adequately improved. Furthermore, drying temperatures above 100°C can cause deformation and / or denaturation of the polymer electrolyte membrane 100, and can lead to deterioration in the performance and durability of the membrane-electrode assembly and fuel cell as the final products.

[0078] If the drying step lasts for less than 10 seconds, a portion of the first dispersion medium 213 will remain instead of evaporating, causing electrode formation defects and adversely affecting subsequent processes. Furthermore, the residual first dispersion medium 213 can excessively remove the ionic conductivity of the polymer electrolyte membrane 100 or cause excessive surface deformation, such as wrinkling, significantly reducing the durability of the polymer electrolyte membrane 100 or leading to electrode formation defects. On the other hand, if the drying step lasts for more than 300 seconds, deformation and / or denaturation of the polymer electrolyte membrane will not only reduce the ionic conductivity of the polymer electrolyte membrane 100 but also decrease the productivity of the membrane-electrode assembly.

[0079] According to this disclosure, in order to increase the surface roughness of the polymer electrolyte membrane 100 without degrading its durability and performance, it is preferable that only the first surface of the polymer electrolyte membrane 100 or only its vicinity is affected by the first dispersion medium 213. Therefore, in one embodiment of this disclosure, the content of (i) the first dispersion medium 213 in the first catalyst slurry 210a, (ii) the content of the first component in the first dispersion medium 213, (iii) the coating thickness of the first catalyst slurry 210a, (iv) the temperature of the drying step, and (v) the time of the drying step can be set such that the first dispersion medium 213 cannot pass through the first surface of the polymer electrolyte membrane and deform more than 70% of the thickness of the polymer electrolyte membrane 100.

[0080] Alternatively or additionally, in order to increase the surface roughness of the polymer electrolyte membrane 100 without degrading its durability and performance, a plurality of irregularly formed grooves G on the first surface of the polymer electrolyte membrane 100 may each have a depth D of less than 5 μm, preferably 0.05 μm to 5 μm, more preferably 0.1 μm to 4.5 μm, and a width W of less than 10 μm, preferably 0.5 μm to 10 μm, more preferably 1 μm to 9 μm. The content of (i) the first dispersion medium 213 in the first catalyst slurry 210a, (ii) the content of the first component in the first dispersion medium 213, (iii) the coating thickness of the first catalyst slurry 210a, (iv) the temperature of the drying step, and (v) the time of the drying step may be set such that each groove G has a depth D and a width W within the range specified above.

[0081] The membrane-electrode assembly manufactured according to the present disclosure as described above includes: a polymer electrolyte membrane 100; and a first electrode 210b on a first surface of the polymer electrolyte membrane 100, wherein the first electrode 210b includes a first catalyst 211 and a first ion conductor 212, and a plurality of grooves G are randomly formed on the first surface, and each groove G has a depth D of less than 5 μm and a width W of less than 10 μm.

[0082] The depth D / width W of the groove G can be obtained by observing the cross-sectional SEM image of the sample (2cm×2cm) to measure the thickness D / width W of each groove G and calculating the arithmetic mean of the measurements.

[0083] Furthermore, according to this disclosure, the content of the first ion conductor 212 in a portion of the filling groove G of the first electrode 210b is higher than the content of the first ion conductor 212 in the remaining portion of the first electrode 210b (e.g., 2% to 12% higher than the content of the first ion conductor 212 in the remaining portion).

[0084] As the first ion conductor 212 naturally moves downwards during the drying process of the first catalyst slurry 210a coated on the polymer electrolyte membrane 100, a relatively high content of the first ion conductor 212 exists in the groove G located below the normal surface of the polymer electrolyte membrane 100 (i.e., the surface on which no groove is formed). Therefore, the adhesion strength between the polymer electrolyte membrane 100 and the first electrode 210b and the durability of the interface therebetween can be improved.

[0085] The content of ion conductors in a specific portion of the first electrode 210b can be calculated as follows.

[0086] First, the content of ion conductors at each of five arbitrary points on the sample electrode (2cm×2cm) is measured using thermogravimetric analysis (TGA), and the arithmetic mean of the measured values ​​is calculated to obtain the content of the first ion conductor 212 in the remaining part of the first electrode 210b (i.e., the part outside the groove).

[0087] Subsequently, the remaining portion of the first electrode 210b is completely removed using a surface and interface cutting analysis system (SAICAS), thereby retaining a portion of the filling groove G of the first electrode 210b. The content of each ionic conductor in the portion of the filling groove G of the first electrode 210b is measured using a TGA method, and the arithmetic mean of the measured values ​​is calculated to obtain the content of the first ionic conductor 212 in the portion of the filling groove G of the first electrode 210b. According to this disclosure, each groove G of a predetermined size randomly arranged on the first surface of the polymer electrolyte membrane 100 is filled with a portion of the first electrode 210b formed on the first surface. As a result, the adhesive strength between the polymer electrolyte membrane 100 and the first electrode 210b can be higher than that of conventional techniques. Therefore, a membrane-electrode assembly with higher interfacial durability between the polymer electrolyte membrane 100 and the first electrode 210b than conventional techniques can be provided.

[0088] The second electrode 220b can be formed on the second surface of the polymer electrolyte membrane 100 using a method substantially the same as that used to form the first electrode 210b.

[0089] For example, the method for manufacturing a membrane-electrode assembly according to this disclosure may further include: a step of coating a second catalyst slurry 220a onto a second surface of a polymer electrolyte membrane 100 opposite to the first surface after forming a first electrode 210b; and a step of drying the second catalyst slurry 220a coated on the second surface to form a second electrode 220b.

[0090] The second catalyst slurry 220a can be obtained by dispersing the second catalyst and the second ion conductor in a second dispersion medium. The substances specified above for the first catalyst 211 can be used in the second catalyst, the substances specified above for the first ion conductor 212 can be used in the second ion conductor, and the components specified above for the first dispersion medium 213 can be used in the second dispersion medium.

[0091] In the following text, reference will be made to Fig. 2 A method for manufacturing a membrane-electrode assembly according to one embodiment of the present disclosure is described.

[0092] like Fig. 2 As shown, the membrane-electrode assembly according to this disclosure can be manufactured in batches.

[0093] Specifically, a polymer electrolyte membrane 100 is prepared with a protective film 10 attached to its second surface. The protective film 10 is configured to prevent the polymer electrolyte membrane 100 from folding or bending during processing and to facilitate handling of the polymer electrolyte membrane 100. There are no limitations on the material of the protective film 10, as long as the material has the mechanical properties necessary to achieve the above-mentioned objectives.

[0094] Subsequently, a first catalyst slurry 210a according to the present disclosure is coated onto a first surface of the polymer electrolyte membrane 100 to have a predetermined shape and size, and then dried to form a first electrode 210b. For example, a slit mold can be used to coat the first catalyst slurry 210a. Optionally, the first catalyst slurry 210a can be coated while a first mask film (not shown) having a first window of a predetermined shape and size is attached to the first surface, such that the first catalyst slurry 210a coats only the portion of the polymer electrolyte membrane exposed through the first window.

[0095] Subsequently, the protective film 10 is removed from the second surface of the polymer electrolyte membrane 100, and a second catalyst slurry 220a is coated on the second surface to have a predetermined shape and size, and then dried to form the second electrode. Fig. 2(Not shown in the image). In one embodiment of this disclosure, the second catalyst slurry 220a is the same as the first catalyst slurry 210a. However, the first catalyst slurry 210a and the second catalyst slurry 220a may be different from each other. The second catalyst slurry 220a may also be coated onto the second surface using a slit mold to have a predetermined shape and size, or it may be coated onto the second surface using a second mask film (not shown) having a second window to have a predetermined shape and size.

[0096] After the electrodes are formed, the first and second mask films are finally removed.

[0097] In the following text, reference will be made to Fig. 3 A method for manufacturing a membrane-electrode assembly according to another embodiment of the present disclosure is described.

[0098] like Fig. 3 As shown, the first electrode 210b and the second electrode 220b can be manufactured separately using a roll-to-roll process.

[0099] like Fig. 3 As shown in (a), a polymer electrolyte membrane 100 with a protective film 10 attached to its second surface is supplied by a PEM unwinding machine 1100.

[0100] The first coating machine 1210 coats the first catalyst slurry 210a according to the present disclosure onto the first surface of the polymer electrolyte membrane 100 supplied by the PEM unwinding machine 1100, so as to have a predetermined shape and size. As described above, the first dispersion medium 213 according to the present disclosure irregularly (i.e. randomly) forms a plurality of grooves G on the first surface of the polymer electrolyte membrane 100 to increase its surface roughness.

[0101] When the polymer electrolyte membrane 100 coated with the first catalyst slurry 210a passes through the first drying device 1310, the first dispersion medium 213 in the first catalyst slurry 210 is removed, and a first electrode 210b is formed. As described above, when the first electrode 210b is formed through the drying step, at least some of the grooves G are filled with the first catalyst 211, the first ion conductor 212, or a mixture thereof, thereby increasing the contact area between the first electrode 210b and the polymer electrolyte membrane 100. Therefore, the adhesive strength between the polymer electrolyte membrane 100 and the first electrode 210b, as well as the durability of the interface therebetween, is improved.

[0102] The polymer electrolyte membrane 100, together with the first electrode 210b formed on its first surface at predetermined intervals and the protective film 10 attached to its second surface, is wound onto a first winding machine 1510. Optionally, as Fig. 3As shown in (a), the first protective sheet 21 supplied by the first unwinding machine 1410 can be wound together with the polymer electrolyte membrane 100 onto the first winding machine 1510 to attach to the first surface on which the first electrode 210b is formed. The first protective sheet 21 is a sheet configured to protect the first electrode 210b and can be paper or a polymer film.

[0103] Subsequently, as Fig. 3 As shown in (b), the polymer electrolyte membrane 100 wound on the first winding machine 1510, the first electrode 210b formed on its first surface at predetermined intervals, and the first protective sheet 21 configured to protect the first electrode 210b are unwound. At this time, the protective film 10 attached to the second surface of the polymer electrolyte membrane 100 is removed from the second surface of the polymer electrolyte membrane 100 by the protective film winding machine 1600.

[0104] The second coating machine 1220 coats the second catalyst slurry 220a according to the present disclosure onto the second surface of the polymer electrolyte membrane 100 supplied by the first winding machine 1510, so as to have a predetermined shape and size. The dispersion medium in the second catalyst slurry 220a also irregularly forms a plurality of grooves G on the second surface of the polymer electrolyte membrane 100 to increase its surface roughness.

[0105] When the polymer electrolyte membrane 100 coated with the second catalyst slurry 220a passes through the second drying apparatus 1320, the dispersion medium in the second catalyst slurry 220a is removed, and a second electrode 220b is formed. As described above, when the second electrode 220b is formed through the drying step, at least some grooves are filled with a catalyst, an ionic conductor, or a mixture thereof, thereby increasing the contact area between the second electrode 220b and the polymer electrolyte membrane 100. Therefore, the adhesive strength between the polymer electrolyte membrane 100 and the second electrode 220b, as well as the durability of their interface, is improved.

[0106] The polymer electrolyte membrane 100, together with a first electrode 210b formed at predetermined intervals on its first surface, a second electrode 220b formed at predetermined intervals on its second surface, and a first protective sheet 21 configured to protect the first electrode 210b, is wound onto an MEA winding machine 1700. At this time, as... Fig. 3 As shown in (b), the second protective sheet 22 supplied by the second unwinding machine 1420 can be wound together with the polymer electrolyte membrane 100 onto the MEA winding machine 1700 to attach to the second surface on which the second electrode 220b is formed. The second protective sheet 22 is a sheet configured to protect the second electrode 220b and can be paper or a polymer film.

[0107] In an alternative embodiment of this disclosure, during the formation of the second electrode 220b, the first protective sheet 21 may be temporarily disposed between the first electrode 210b and the device to protect the first electrode 210b and the device (i.e., the first protective sheet may not be wound on the MEA winding machine 1700).

[0108] Reference Fig. 4 A method for manufacturing a membrane-electrode assembly according to another embodiment of the present disclosure is described.

[0109] exist Fig. 3 In the method shown, the first electrode 210b and the second electrode 220b are manufactured by separate roll-to-roll processes, while Fig. 4 In the method shown, the first electrode 210b and the second electrode 220b are manufactured by a single roll-to-roll process.

[0110] like Fig. 4 As shown, a polymer electrolyte membrane 100 with a protective film 10 attached to its second surface is supplied by a PEM unwinding machine 1100.

[0111] The first coating machine 1210 coats the first catalyst slurry 210a according to the present disclosure onto the first surface of the polymer electrolyte membrane 100 supplied by the PEM unwinding machine 1100, so as to have a predetermined shape and size. As described above, the first dispersion medium 213 according to the present disclosure irregularly forms a plurality of grooves G on the first surface of the polymer electrolyte membrane 100 to increase its surface roughness.

[0112] When the polymer electrolyte membrane 100 coated with the first catalyst slurry 210a passes through the first drying device 1310, the first dispersion medium 213 in the first catalyst slurry 210a is removed, and a first electrode 210b is formed. As described above, when the first electrode 210b is formed through the drying step, at least some of the grooves G are filled with the first catalyst 211, the first ion conductor 212, or a mixture thereof, thereby increasing the contact area between the first electrode 210b and the polymer electrolyte membrane 100. Therefore, the adhesive strength between the polymer electrolyte membrane 100 and the first electrode 210b, as well as the durability of the interface therebetween, is improved.

[0113] Subsequently, the polymer electrolyte membrane 100, together with the first electrode 210b formed at predetermined intervals on its first surface and the protective film 10 attached to its second surface, passes between the first pressure roller 1810 and the second pressure roller 1820. At this time, as Fig. 4As shown, the first protective sheet 21 supplied by the first unwinding machine 1410 also passes between the first pressure roller 1810 and the second pressure roller 1820, thereby attaching the first protective sheet to the first surface of the polymer electrolyte membrane 100 on which the first electrode 210b is formed. As described above, the first protective sheet 21 is a sheet configured to protect the first electrode 210b, and may be paper or a polymer film.

[0114] Subsequently, as Fig. 4 As shown, the protective film 10 attached to the second surface of the polymer electrolyte membrane 100 is removed from the second surface of the polymer electrolyte membrane 100 by a protective film winding machine 1600.

[0115] The second coating machine 1220 coats the second catalyst slurry 220a according to the present disclosure onto the second surface of the polymer electrolyte membrane 100 supplied by the first winding machine 1510, so as to have a predetermined shape and size. The dispersion medium in the second catalyst slurry 220a also irregularly forms a plurality of grooves G on the second surface of the polymer electrolyte membrane 100 to increase its surface roughness.

[0116] When the polymer electrolyte membrane 100 coated with the second catalyst slurry 220a passes through the second drying apparatus 1320, the dispersion medium in the second catalyst slurry 220a is removed, and a second electrode 220b is formed. As described above, when the second electrode 220b is formed through the drying step, at least some grooves are filled with a catalyst, an ionic conductor, or a mixture thereof, thereby increasing the contact area between the second electrode 220b and the polymer electrolyte membrane 100. Therefore, the adhesive strength between the polymer electrolyte membrane 100 and the second electrode 220b, as well as the durability of their interface, is improved.

[0117] The polymer electrolyte membrane 100, together with a first electrode 210b formed at predetermined intervals on its first surface, a second electrode 220b formed at predetermined intervals on its second surface, and a first protective sheet 21 configured to protect the first electrode 210b, is wound onto an MEA winding machine 1700. At this time, as... Fig. 4 As shown, the second protective sheet 22 supplied by the second unwinding machine 1420 can be wound together with the polymer electrolyte membrane 100 onto the MEA winding machine 1700 to adhere to the second surface on which the second electrode 220b is formed. The second protective sheet 22 is a sheet configured to protect the second electrode 220b and can be paper or a polymer film.

[0118] As described above, or during the formation of the second electrode 220b, the first protective sheet 21 may be temporarily placed between the first electrode 210b and the device to protect the first electrode 210b and the device (i.e., the first protective sheet may not be wound on the MEA winding machine 1700).

[0119] Optionally, the mask film can be used to form the first electrode 210b and the second electrode 220b at predetermined intervals so as to always have a predetermined shape and size. Specifically, the method according to one embodiment of the present disclosure may further include: attaching a first mask film (not shown) having a first window to a first surface before coating a first catalyst slurry 210a on the first surface; removing the first mask film after forming the first electrode 210b; attaching a second mask film having a second window to a second surface before coating a second catalyst slurry 220a on the second surface; and removing the second mask film after forming the second electrode 220b. Thus, the first catalyst slurry 210a supplied by the first coating machine 1210 can be coated only on the portion of the first surface exposed through the first window. In the same manner, the second catalyst slurry 220a supplied by the second coating machine 1220 can be coated only on the portion of the second surface exposed through the second window.

[0120] The present disclosure will be described in detail below with reference to specific embodiments. However, the following embodiments are provided only to aid in understanding the present disclosure and do not limit the scope of the present disclosure.

[0121] Example 1

[0122] 1 g of commercially available catalyst was placed in a reaction vessel and moistened with water. Then, 0.4 g of ionic conductor powder was added to the reaction vessel. Next, 40 g of a dispersion medium containing 60 wt% ethanol and 40 wt% water was added to the reaction vessel. The catalyst and ionic conductor were then dispersed in the dispersion medium using a homogenizer to obtain a catalyst slurry. The dispersion medium content in the catalyst slurry was 96.6 wt%.

[0123] While attaching a mask film, a catalyst slurry is coated onto the first surface of a fluorinated polymer electrolyte membrane, on which a protective film is attached, to a thickness of 130 μm using a slit mold. The coating is then dried at 80°C for 180 seconds to form the first electrode. The polymer electrolyte membrane is a reinforced composite membrane type polymer electrolyte membrane including a porous support. After removing the mask film, a protective sheet is attached to the first surface on which the first electrode is formed. Subsequently, the protective film is removed from the second surface, and then the mask film is attached to the second surface. The catalyst slurry is coated onto the portion of the second surface exposed through the window of the mask film to a thickness of 100 μm using a slit mold, and then dried at 80°C for 100 seconds to form the second electrode. The protective sheet is then removed from the first surface, thereby fabricating the membrane-electrode assembly.

[0124] Example 2

[0125] Except that the content of the dispersion medium in the catalyst slurry is 83.0% by weight, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0126] Example 3

[0127] Except that the content of the dispersion medium in the catalyst slurry is 98.0% by weight, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0128] Example 4

[0129] Except that the dispersion medium contains 55% by weight of ethanol and 45% by weight of water, the membrane-electrode assembly was manufactured using the same method as in Example 1.

[0130] Example 5

[0131] Except that the dispersion medium contains 80% by weight of ethanol and 20% by weight of water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0132] Example 6

[0133] Except that the dispersion medium contains methanol instead of ethanol, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0134] Example 7

[0135] Except that the dispersion medium contains propanol instead of ethanol, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0136] Example 8

[0137] Except that the dispersion medium contains ethoxyethanol instead of ethanol, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0138] Example 9

[0139] Except that the dispersion medium contains butanol instead of ethanol, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0140] Example 10

[0141] Except that the dispersion medium contains NMP instead of water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0142] Example 11

[0143] Except that the dispersion medium contains THF instead of water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0144] Comparative Example 1

[0145] Except that the dispersion medium contains 20% by weight ethylene glycol and 80% by weight water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0146] Comparative Example 2

[0147] Except that the content of the dispersion medium in the catalyst slurry is 80.0% by weight, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0148] Comparative Example 3

[0149] Except that the content of the dispersion medium in the catalyst slurry is 98.2% by weight, the membrane-electrode assembly was manufactured using the same method as in Example 1.

[0150] Comparative Example 4

[0151] Except that the dispersion medium contains 50% by weight of ethanol and 50% by weight of water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0152] Comparative Example 5

[0153] Except that the dispersion medium contains 90% by weight ethanol and 10% by weight water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0154] Comparative Example 6

[0155] Except that the dispersion medium contains 50% by weight ethoxyethanol and 50% by weight water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0156] Comparative Example 7

[0157] Except that the dispersion medium contains 50% by weight isopropanol and 50% by weight water, the membrane-electrode assembly is manufactured using the same method as in Example 1.

[0158] [Analysis of the surface and cross-section of the membrane-electrode assembly]

[0159] The surface and cross-section of the membrane-electrode assembly of Example 1 were observed using an optical microscope and a scanning electron microscope.

[0160] Fig. 5These are optical micrographs showing the surface of the membrane-electrode assembly obtained in Example 1. Fig. 6 (a) and Fig. 6 (b) are scanning electron micrographs (SEM images) showing the surface and cross-section of the membrane-electrode assembly obtained in Example 1, respectively.

[0161] from Fig. 5 and Fig. 6 As can be seen from the surface photograph in (a), for the membrane-electrode assembly of Example 1, although the electrode is formed while increasing the surface roughness of the polymer electrolyte membrane, unlike most other methods where the surface of the electrode even cracks, the electrode has a smooth surface without cracks during the electrode formation process.

[0162] In addition, from Fig. 6 (b) The cross-sectional SEM image shows that grooves (circled) with a depth of less than 5 μm and a width of less than 10 μm are formed on the surface of the polymer electrolyte membrane, and these grooves are filled with electrode material. That is, it can be seen that the contact area between the electrode and the polymer electrolyte membrane is increased. It is reasonable to predict that this increase in contact area will improve the adhesion strength and the durability of the interface.

[0163] In the same manner, cross-sectional SEM images of Examples 2 to 11 and Comparative Examples 1 to 7 were examined to check whether grooves with a depth of less than 5 μm and a width of less than 10 μm were formed on the surface of the polymer electrolyte membrane (the first surface on which the first electrode is formed). The results are shown in Table 1 below.

[0164] [Table 1]

[0165]

[0166] As can be seen from Table 1 above, grooves with a depth of less than 5 μm and a width of less than 10 μm were formed on the surface of the polymer electrolyte membrane of each membrane-electrode assembly manufactured according to Examples 1 to 11. Conversely, it can be seen that when the content of the dispersion medium in the catalyst slurry deviates from the scope of this disclosure (Comparative Examples 2 and 3), and when the content of the first component in the dispersion medium deviates from the scope of this disclosure (Comparative Examples 1 and Comparative Examples 4 to 7), grooves with a depth of less than 5 μm and a width of less than 10 μm were not formed. In particular, for Comparative Example 5, where the content of the first component in the dispersion medium was 90% by weight, grooves with a depth greater than 5 μm and a width greater than 10 μm were formed.

[0167] [Evaluation of the physical and chemical durability of membrane-electrode assemblies]

[0168] Based on the U.S. Department of Energy (DOE) durability assessment protocol, the physical and chemical durability of each membrane-electrode assembly in Example 1 and Comparative Example 1 was evaluated. Specifically, to evaluate the physical durability of the membrane-electrode assembly, 20,000 dry / wet cycles were performed, followed by H2 permeation measurement. The measurements are shown in Table 2 below. Fig. 7 This is a graph showing the H2 permeation measured during 20,000 wet / dry cycles on the membrane-electrode assembly obtained in Example 1.

[0169] In addition, to evaluate the chemical durability of the membrane-electrode assembly, the OCV retention method was performed for 500 hours, followed by measurement of H2 permeation and voltage loss. The measured values ​​are shown in Table 2 below. Fig. 8 (a) and Fig. 8 (b) is a graph showing the voltage retention and H2 permeation measured during 500 hours of OCV retention on the membrane-electrode assembly obtained in Example 1.

[0170] [Table 2]

[0171]

[0172] From Table 2 above and Fig. 7 As can be seen from the curves, compared with the membrane-electrode assembly of Comparative Example 1, the membrane-electrode assembly of Example 1 meets the DOE standard (H2 permeation ≤ 15 mA / cm). 2 (@20,000 wet / dry cycles), and exhibited very stable physical durability before / after the durability evaluation. Furthermore, from Table 2 above and... Fig. 8 As can be seen from the curves, compared with the membrane-electrode assembly of Comparative Example 1, the membrane-electrode assembly of Example 1 meets the DOE standard (voltage loss ≤20%@500 hours, H2 permeation ≤15mA / cm). 2 It exhibits chemical durability with less voltage loss (@500 hours).

[0173] Similar to the membrane-electrode assembly of Example 1, the membrane-electrode assemblies of Examples 2 to 11, in which grooves having a depth of less than 5 μm and a width of less than 10 μm are formed on the surface of the polymer electrolyte membrane, also exhibit excellent physical and chemical durability. Conversely, the membrane-electrode assemblies of Comparative Examples 2 to 7, in which grooves having a depth of less than 5 μm and a width of less than 10 μm are not formed on the surface of the polymer electrolyte membrane, exhibit relatively low physical and chemical durability.

[0174] As can be seen from the above evaluation results, the manufacturing method of the membrane-electrode assembly according to this disclosure can improve the durability of the membrane-electrode assembly without deteriorating the durability of the polymer electrolyte membrane.

Claims

1. A method for manufacturing a membrane-electrode assembly, the method comprising: The first catalyst and the first ionic conductor are dispersed in a first dispersion medium to obtain a first catalyst slurry; The first catalyst slurry is directly coated onto the first surface of the polymer electrolyte membrane; as well as The first catalyst slurry coated on the first surface is dried to form the first electrode, wherein... The first dispersion medium comprises: (i) a first component capable of partially dissolving the polymer electrolyte film at the first surface or causing deformation of the first surface to irregularly form a plurality of grooves on the first surface; and (ii) a second component different from the first component. The first component is an alcohol, acetic acid, propionic acid, dimethylacetamide, or a mixture of two or more of them. The alcohol is methanol, ethanol, propanol, ethoxyethanol, butanol, or a mixture of two or more of them. The second component is water, N-methylpyrrolidone (NMP), dimethyl sulfoxide (DMSO), tetrahydrofuran (THF), or a mixture of two or more of these. The content of the first dispersion medium in the first catalyst slurry is 83% to 98% by weight. The content of the first component in the first dispersion medium is 55% to 80% by weight. The first catalyst slurry is coated onto the first surface to a coating thickness of 10 μm to 200 μm. The drying process is carried out at a temperature of 50°C to 150°C for 10 to 300 seconds. When the first electrode is formed through a drying step, at least some of the grooves are filled with the first catalyst, the first ionic conductor, or a mixture thereof, and The difference between the content of the first ion conductor in the portion of the first electrode filling the groove and the content of the first ion conductor in the remaining portion of the first electrode is 2% to 12% of the content of the first ion conductor in the remaining portion of the first electrode. Each of the grooves has a depth of less than 5 μm and a width of less than 10 μm.

2. The manufacturing method according to claim 1, wherein, The dispersion is performed using at least one selected from ultrasonic homogenizers, ball mills, roller mills, resonant acoustic mixers, high-pressure homogenizers, planetary mixers, and homogenizers.

3. The manufacturing method according to claim 1, wherein, The polymer electrolyte membrane contains fluorine-based ionic conductors.

4. The manufacturing method according to claim 1, wherein, The drying process is carried out by hot air drying, infrared drying, or hot plate drying.

5. The manufacturing method according to claim 1, further comprising: After the first electrode is formed, a second catalyst slurry is coated on the second surface of the polymer electrolyte membrane opposite to the first surface; and The second catalyst slurry coated on the second surface is dried to form the second electrode.

6. The manufacturing method according to claim 5, wherein, The first catalyst slurry is coated onto the first surface while the protective film is attached to the second surface of the polymer electrolyte membrane.

7. The manufacturing method according to claim 6, further comprising: The protective film is removed from the second surface before the second catalyst slurry is coated onto the second surface.

8. The manufacturing method according to claim 7, further comprising: Before removing the protective film from the second surface, a first protective sheet is attached to the first surface on which the first electrode is formed.

9. The manufacturing method according to claim 8, further comprising: The second protective sheet is attached to the second surface on which the second electrode is formed.

10. The manufacturing method according to claim 5, further comprising: Before coating the first catalyst slurry onto the first surface, a first mask film having a first window is attached to the first surface; Remove the first mask film after forming the first electrode; Before coating the second catalyst slurry onto the second surface, a second mask film having a second window is attached to the second surface; as well as After the second electrode is formed, the second mask film is removed, wherein... The first catalyst slurry is coated onto the first surface by applying the first catalyst slurry to the portion of the first surface exposed through the first window. The second catalyst slurry is coated onto the second surface by applying the second catalyst slurry to the portion of the second surface exposed through the second window.

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