Electrode slurry for repairing cracks, catalyst layer for fuel cell, membrane-electrode assembly, and fuel cell

Abstract

Disclosed herein is an electrode slurry capable of repairing cracks in an electrode. According to an aspect of the present invention, provided is an electrode slurry for repairing cracks, the electrode slurry comprising at least 60 wt% of a first solvent that has a surface tension of at most 40 mN / m at 20oC, wherein the electrode slurry has a surface tension of at most 65 mN / m at 20 °C, a viscosity of at most 100 cP at 20 °C, and a total solids content of at most 12 wt%.

Description

Electrode slurry for crack repair, catalyst layer for fuel cell, membrane-electrode assembly and fuel cell

[0001] The present invention relates to an electrode slurry for crack repair, and more particularly, to an electrode slurry for crack repair, a catalyst layer for a fuel cell, a membrane-electrode assembly, and a fuel cell.

[0002] Fuel cells, which directly convert the chemical energy generated by fuel oxidation into electrical energy, are attracting attention as a next-generation energy source due to their high energy efficiency and environmental friendliness with low pollutant emissions. These fuel cells are generally structured with an anode and a cathode formed on either side of a polymer electrolyte membrane, and this structure is called a membrane electrode assembly (MEA). Fuel cells can be classified into alkaline electrolyte fuel cells and polymer electrolyte membrane fuel cells (PEMFC) depending on the type of electrolyte membrane. Among them, polymer electrolyte membrane fuel cells are attracting attention as a power source for portable, automotive, and home use due to their advantages such as low operating temperature of less than 100℃, fast start-up and response characteristics, and excellent durability. A representative example of such polymer electrolyte membrane fuel cells is the proton exchange membrane fuel cell (PEMFC), which uses hydrogen gas as fuel.

[0003] Meanwhile, in polymer electrolyte membrane fuel cells, the polymer electrolyte membrane can shrink or expand for various reasons, leading to cracks forming on the electrodes formed on one side of the membrane. When commercial electrode slurries are used to repair these cracks, they are applied only to the surrounding area, deepening the cracks.

[0004] An object of the present invention is to provide an electrode slurry capable of repairing cracks in an electrode.

[0005] Another object of the present invention is to provide an electrode slurry for crack repair that can improve durability, heat dissipation effect, efficiency of catalytic reaction or moisture retention ability.

[0006] Another object of the present invention is to provide a membrane-electrode assembly in which both performance and durability are improved.

[0007] Another object of the present invention is to provide a fuel cell including the membrane-electrode assembly.

[0008] The purposes of the present invention are not limited to those mentioned above, and other unmentioned purposes and advantages of the present invention can be understood through the following description and will be more clearly understood through the embodiments of the present invention. Furthermore, it will be readily apparent that the purposes and advantages of the present invention can be realized by the means and combinations thereof set forth in the claims.

[0009] According to the first aspect of the present invention for achieving the above object, a first solvent having a surface tension of 40 mN / m or less at 20°C is included at least 60 wt%, and o An electrode slurry for crack repair is provided, which has a surface tension of 65 mN / m or less at C, a viscosity of 100 cP or less at 20°C, and a total solid content of 12 wt% or less.

[0010] According to a second aspect of the present invention, in the first aspect, the first solvent may include at least one selected from the group consisting of alcohol, acetic acid, propionic acid, oleic acid, carbon tetrachloride, pyrrole, and pyridine.

[0011] According to a third aspect of the present invention, in the first or second aspect, the crack repair electrode slurry further includes a second solvent having a surface tension of more than 40 mN / m at 20°C, and the content of the second solvent may be 10 wt% or less based on the total weight of the crack repair electrode slurry.

[0012] According to a fourth aspect of the present invention, a crack repair electrode slurry further comprising functional nanoparticles in any one of the first to third aspects can be provided.

[0013] According to a fifth aspect of the present invention, in the fourth aspect, the functional nanoparticles may include at least one selected from the group consisting of radical scavengers, catalytic nanoparticles, heat-radiating nanoparticles, and hygroscopic nanoparticles.

[0014] According to a sixth aspect of the present invention, a crack repair electrode slurry may be provided, which further comprises a binder dispersion comprising a binder in any one of the first to fifth aspects. Here, the binder may be any one selected from the group consisting of a fluorine-based ion conductor, a hydrocarbon-based ion conductor, and a mixture thereof.

[0015] According to a seventh aspect of the present invention, a catalyst layer for a fuel cell is provided, comprising a first catalyst layer including a crack region and a second catalyst layer on the first catalyst layer, wherein a portion of the second catalyst layer corresponding to the crack region extends along the crack surface and includes a first region including a first binder and a second region different from the first region and including a second binder, and wherein a content of the first binder per unit volume of the first region is higher than a content of the second binder per unit volume of the second region.

[0016] According to the eighth aspect of the present invention, in the seventh aspect, the height of the first region in a direction intersecting the direction in which the crack surface extends may be greater than 0 μm and less than or equal to 2 μm.

[0017] According to a ninth aspect of the present invention, a membrane-electrode assembly comprising a catalyst layer for a fuel cell according to the seventh or eighth aspect is provided.

[0018] According to a tenth aspect of the present invention, a fuel cell is provided comprising a membrane-electrode assembly according to the ninth aspect.

[0019] The solutions to the above problems are not exhaustive and may be combined with several embodiments of the present disclosure. The various features of the present invention and their corresponding advantages and effects can be understood in more detail by referring to the detailed description below.

[0020] According to one aspect of the present invention, when repairing a crack in an electrode with a conventional commercial electrode slurry, the problem of the crack actually becoming deeper because it is applied only to the area surrounding the crack can be solved.

[0021] According to another aspect of the present invention, an electrode slurry can be provided that improves the performance and durability of a membrane-electrode assembly due to a repaired crack.

[0022] According to another aspect of the present invention, an electrode slurry having improved chemical durability, heat dissipation effect, catalytic reaction efficiency, or moisture retention ability can be provided.

[0023] In addition to the effects described above, specific effects of the present invention are described below while explaining specific details for carrying out the invention.

[0024] FIG. 1a is a cross-sectional view of a catalyst layer for a fuel cell with a crack repaired according to one embodiment of the present invention.

[0025] Figure 1b is an enlarged view of a portion of the second catalyst layer positioned at a position corresponding to the crack area of ​​Figure 1a.

[0026] Figure 2 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention.

[0027] Figure 3 is an optical microscope photograph of a catalyst layer for a fuel cell in which cracks have been repaired according to Example 1 and Comparative Example 1.

[0028] Figure 4 is a graph showing the performance of membrane-electrode assemblies according to Comparative Examples 1 and 2 and Example 1.

[0029] In this specification, singular expressions include plural expressions unless the context clearly indicates otherwise.

[0030] The terms "comprise" and / or "comprising" in this specification specify the presence of stated features, steps, numbers, operations, elements, elements and / or groups thereof, but do not preclude the presence or addition of one or more other features, steps, numbers, operations, elements, elements and / or groups thereof.

[0031] In this specification, “At least one of a, b and c” may include a, b or c alone, or a combination of two or more selected from the group consisting of a, b and c.

[0032] If multiple embodiments are described in this specification, the embodiments may be combined unless specifically stated otherwise. In this case, the effects of the present invention may be defined as including the effects derived from each embodiment and the effects resulting from the organic combination of the embodiments. For example, even if Embodiments 1 and 2 are described independently in this specification, Embodiments 1 and 2 may be organically combined with each other, unless the context clearly indicates otherwise, and the effects of the present invention may include the effects resulting from the combination of Embodiments 1 and 2.

[0033] The numerical range indicated by the term "to" in this specification refers to a numerical range that includes the values ​​described before and after the term as the lower limit and the upper limit, respectively. When multiple numerical values ​​are disclosed as the upper and lower limits of an arbitrary numerical range, the numerical range disclosed in this specification can be understood as any numerical range that has any one of the multiple lower limit values ​​and any one of the multiple upper limit values ​​as the lower limit and the upper limit, respectively. For example, when a to b, or c to d is described in the specification, it can be understood that a or more and b or less, a or more and d or less, c or more and d or less, or c or more and b or less is described.

[0034] As used herein, terms such as "about" or "substantially" mean a reasonable amount of variation from the term that does not significantly alter the final result. These terms may be interpreted to include a variation of at least ±5% or at least ±10%, provided that such variation does not alter the meaning of the term and render it invalid.

[0035] In this specification, the term "layer" or film may include cases where it is formed not only over the entire area when observing the area where the layer or film exists, but also cases where it is formed over only a portion of the area. For example, the surface of the layer or film may be defined to include a flat shape, a non-flat shape, and a combination thereof; or a continuous shape, a discontinuous shape, and a combination thereof. For example, when another element is formed as a layer or film directly on top of one element, the coverage of the other element on the surface of the one element may be defined as 1% or more, 5% or more, 10% or more, 20% or more, 30% or more, 40% or more, 50% or more, 60% or more, 70% or more, 80% or more, 85% or more, 90% or more, 95% or more, or 99% or more. For example, even when a plurality of particles form a clustered structure, it can be defined as a "layer" or "film". For example, a layer can also be a term that includes a shape in which the surface is irregularly or randomly formed.

[0036] In this specification, the average particle diameter of the particles is the particle diameter (D) when the cumulative percentage in the volume-based particle size distribution curve is 50% when measured by a laser diffraction particle size distribution measuring device. 50 ) can be defined. For example, the average particle diameter of the particles can be calculated by dispersing the target particles in a dispersion medium, introducing them into a commercially available laser diffraction particle size measuring device (e.g., Microtrac S3500), and measuring the difference in diffraction pattern according to particle size when the particles pass through a laser beam.

[0037] According to one aspect of the present invention, a solvent having a surface tension of 40 mN / m or less at 20°C is included at least 60 wt%, and oThe present invention provides an electrode slurry for crack repair, which has a surface tension of 65 mN / m or less at C, a viscosity of 100 cP or less at 20°C, and a total solid content of 12 wt% or less. According to one aspect of the present invention, when repairing a crack in an electrode with a conventional commercial electrode slurry, the problem that the depth of the crack actually deepens because the slurry is applied only to the peripheral area of ​​the crack can be solved, and an electrode slurry can be provided in which the performance and durability of a membrane-electrode assembly are improved due to the repaired crack.

[0038] Below, the configuration of the present invention is described in more detail.

[0039] 1. Electrode slurry for crack repair

[0040] The electrode slurry for crack repair according to the present invention comprises at least 60 wt% of a first solvent having a surface tension of 40 mN / m or less at 20°C. The surface tension refers to the property of the force by which the surface of the solvent contracts on its own to take up as small an area as possible, and can be measured using the capillary rise method or the Du Nouy tensiometer. Here, the first solvent is a factor that controls the viscosity and surface tension of the electrode slurry, and as a result, the crack repair effect can vary depending on the content of the first solvent.

[0041] In some embodiments of the present invention, the surface tension of the first solvent may be 5 to 40 mN / m at 20°C, and more specifically, 7 to 39 mN / m, 10 to 35 mN / m, 15 to 30 mN / m, 18 to 25 mN / m, 20 to 24 mN / m, or 21 to 23 mN / m. If the surface tension of the first solvent is outside the above numerical range, the electrode slurry may be applied only to the peripheral area of ​​the crack, and as the depth of the crack deepens, it may become difficult to repair the crack formed in the electrode.

[0042] In some embodiments of the present invention, the content of the first solvent may be greater than 60 wt%, more specifically 61 to 95 wt%, 62 to 94 wt%, 63 to 90 wt%, 64 to 85 wt%, 65 to 80 wt%, 65 to 75 wt%, 65 to 70 wt%, 65 to 68 wt%, 65 to 67 wt%, or 65 to 66 wt%, based on the total weight of the crack repair electrode slurry. If the content of the first solvent is outside the above numerical range, the electrode slurry may be applied only to the peripheral area of ​​the crack, and as the depth of the crack deepens, it may become difficult to repair the crack formed in the electrode.

[0043] In some examples, the first solvent is not particularly limited, but may specifically include one or more selected from the group consisting of alcohol, acetic acid, propionic acid, oleic acid, carbon tetrachloride, pyrrole, and pyridine, and may specifically be alcohol, and more specifically may be ethanol.

[0044] In some embodiments of the present invention, the electrode slurry for crack repair may further comprise a second solvent having a surface tension of more than 40 mN / m at 20°C. Here, the second solvent may be a factor that controls the viscosity and surface tension of the electrode slurry for crack repair. According to some embodiments of the present invention, by mixing the second solvent with the first solvent, the dispersion effect of the catalyst nanoparticles in the electrode slurry may be further improved.

[0045] According to some embodiments of the present invention, the content of the second solvent may be 10 wt% or less, and specifically 1 to 9 wt%, 2 to 8 wt%, 3 to 7 wt%, 4 to 6 wt%, or 5 to 6 wt%, based on the total weight of the electrode slurry for crack repair. When the content of the second solvent satisfies the numerical range, cracks in the electrode formed by shrinkage or expansion of the polymer electrolyte membrane can be effectively repaired.

[0046] In some examples, the second solvent is not particularly limited and may specifically include one or more selected from the group consisting of water, glycerol, and an aqueous sodium chloride solution of about 5 M or more.

[0047] The crack repair electrode slurry according to the present invention has a surface tension of 65 mN / m or less at 20°C, specifically 15 to 62 mN / m, and more specifically 20 to 60 mN / m, 30 to 60 mN / m, 35 to 59 mN / m, 40 to 55 mN / m, or 43 to 50 mN / m. If the surface tension of the crack repair electrode slurry at 20°C is outside the above numerical range, the electrode slurry may be applied only to the peripheral area of ​​the crack, and the depth of the crack may actually deepen, making it difficult to repair the crack formed in the electrode. The surface tension of the crack repair electrode slurry may be measured using the capillary rise method or a Du nouy tensiometer.

[0048] The electrode slurry for crack repair according to the present invention has a viscosity of 100 cP or less at 20°C, specifically 10 to 90 cP, and more specifically 15 to 85 cP, 20 to 80 cP, 25 to 75 cP, 30 to 70 cP, 35 to 65 cP, 38 to 60 cP, 38 to 50 cP, or 38 to 48 cP. If the viscosity of the electrode slurry for crack repair is outside the above numerical range, the electrode slurry is applied only to the peripheral area of ​​the crack, and the depth of the crack actually deepens, making it difficult to repair the crack formed in the electrode. The viscosity of the electrode slurry for crack repair can be measured using a viscosity meter commonly used in the relevant technical field.

[0049] The total solid content based on the total weight of the crack repair electrode slurry according to the present invention is 12 wt% or less, and specifically, may be 11 wt% or less, 10 wt% or less, 0.1 to 10 wt%, 1 to 10 wt%, 2 to 10 wt%, 3 to 10 wt%, 4 to 10 wt%, 5 to 10 wt%, 6 to 10 wt%, 7 to 10 wt%, 8 to 10 wt%, or 9 to 10 wt%. For example, the total solid content in the crack repair electrode slurry may be the content excluding the first and second solvents and the dispersion medium included in the binder dispersion. Specifically, if the total solid content based on the total weight of the electrode slurry for crack repair is outside the above numerical range, the electrode slurry may be applied only to the surrounding area of ​​the crack, and the depth of the crack may actually deepen, making it difficult to repair the crack formed in the electrode.

[0050] The electrode slurry for crack repair according to some embodiments of the present invention may further comprise functional nanoparticles. The functional nanoparticles may comprise, for example, at least one selected from the group consisting of radical scavengers, catalytic nanoparticles, heat-dissipating nanoparticles, and hygroscopic nanoparticles. Alternatively, the functional nanoparticles may comprise catalytic nanoparticles and further comprise at least one selected from the group consisting of radical scavengers, heat-dissipating nanoparticles, and hygroscopic nanoparticles.

[0051] The radical scavenger can capture oxygen radicals generated during operation of the fuel cell. The radical scavenger can be, for example, any one selected from the group consisting of a transition metal, an ion of a transition metal, an oxide of a transition metal, a complex of a transition metal, a noble metal, an ion of a noble metal, an oxide of a noble metal, a complex of a noble metal, and combinations thereof. The transition metal can be any one selected from the group consisting of cerium (Ce), manganese (Mn), tungsten (W), cobalt (Co), vanadium (V), nickel (Ni), chromium (Cr), zirconium (Zr), yttrium (Y), iridium (Ir), iron (Fe), titanium (Ti), molybdenum (Mo), lanthanum (La), and neodymium (Nd). The above precious metal may be any one selected from the group consisting of silver (Ag), platinum (Pt), ruthenium (Ru), palladium (Pd), and rhodium (Rh).

[0052] The above catalyst nanoparticle may be any one selected from the group consisting of platinum-based nanoparticles, OER (Oxygen evolution reaction) catalyst nanoparticles, and combinations thereof.

[0053] The above platinum-based nanoparticles are catalytic nanoparticles that participate in the reaction of the battery, and may be, for example, at least one selected from the group consisting of platinum (Pt), palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), and platinum-M (Pt-M). Specifically, the M may be at least one selected from the group consisting of palladium (Pd), ruthenium (Ru), iridium (Ir), osmium (Os), gallium (Ga), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), cobalt (Co), nickel (Ni), copper (Cu), silver (Ag), gold (Au), zinc (Zn), tin (Sn), molybdenum (Mo), tungsten (W), lanthanum (La), and rhodium (Rh). More specifically, the platinum alloy may be any one selected from the group consisting of Pt-Pd, Pt-Sn, Pt-Mo, Pt-W, Pt-Ru, Pt-Ru-W, Pt-Ru-Mo, Pt-Ru-Rh-Ni, Pt-Ru-Sn-W, Pt-Co, Pt-Co-Ni, Pt-Co-Fe, Pt-Co-Ir, Pt-Co-S, Pt-Co-P, Pt-Fe, Pt-Fe-Ir, Pt-Fe-S, Pt-Fe-P, Pt-Au-Co, Pt-Au-Fe, Pt-Au-Ni, Pt-Ni, Pt-Ni-Ir, Pt-Cr, Pt-Cr-Ir, and combinations thereof.

[0054] According to another embodiment of the present invention, the platinum-based nanoparticles may be supported on a carrier. The carrier may be, for example, one selected from the group consisting of a carbon-based carrier, a porous inorganic oxide, a zeolite, and a combination thereof. The carbon-based carrier may be, for example, selected from the group consisting of graphite, Super P, carbon fiber, carbon sheet, carbon black, Ketjen black, Denka black, acetylene black, carbon nanotube (CNT), carbon sphere, carbon ribbon, fullerene, activated carbon, carbon nanofiber, carbon nanowire, carbon nanoball, carbon nanohorn, carbon nanocage, carbon nanoring, carbon aerogel, graphene, stabilized carbon, activated carbon, and a combination of at least one or more thereof, but is not limited thereto. The above porous inorganic oxide may correspond to at least one selected from the group consisting of, for example, zirconia, alumina, titania, silica, and ceria. The surface area of ​​the carrier may be 50 m 2 / g or more may be preferable, and the average particle diameter may be 10 to 300 nm. If the surface area of ​​the carrier is less than the above numerical range, a uniform distribution of metal nanoparticles may not be obtained.

[0055] In some examples, the OER (oxygen evolution reaction) catalyst nanoparticles are nanoparticles that promote a reaction that generates oxygen gas and electrons through the oxidation of water. The OER catalyst nanoparticles may be, for example, any one selected from the group consisting of ruthenium oxide (RuO2), iridium oxide (IrO2), and combinations thereof.

[0056] In some examples, the heat-dissipating nanoparticles are nanoparticles that transfer heat generated during fuel cell operation to the outside of the catalyst layer, and may be, for example, one or more selected from the group consisting of metal nanoparticles, ceramic nanoparticles, and carbon nanoparticles.

[0057] In some examples, the metal nanoparticles may be selected from the group consisting of Al, Mg, Cu, Ni, Ag, and core-shell nanoparticles having excellent thermal conductivity. In the core-shell nanoparticles, a metal or metalloid belonging to groups 2 to 15 of the periodic table may be used as the core, and a metal having excellent thermal conductivity or being relatively stable may be used as the shell. The core-shell nanoparticles may be, for example, Cu@Ag, Fe@Al, or Cu@Au.

[0058] In some examples, the ceramic nanoparticles may be one or more selected from the group consisting of boron nitride, aluminum nitride, aluminum oxide, silicon carbide, and beryllium oxide. The ceramic nanoparticles have excellent thermal conductivity, so they can easily transfer heat to the outside of the catalyst layer and have the effect of preventing moisture within the catalyst layer from evaporating.

[0059] According to some embodiments of the present invention, the boron nitride may be hexagonal boron nitride (h-BN). The hexagonal boron nitride has properties and a plate-like structure similar to graphite, and thus may have excellent thermal conductivity, insulation, and chemical stability at high temperatures.

[0060] The above carbon nanoparticles may be, for example, at least one selected from the group consisting of carbon nanofibers, carbon black, acetylene black, carbon nanotubes (CNTs), carbon spheres, carbon ribbons, fullerenes, graphene, and activated carbon.

[0061] The hygroscopic nanoparticles may be nanoparticles that effectively absorb moisture generated during fuel cell operation. Specifically, the hygroscopic nanoparticles may include, for example, any one selected from the group consisting of porous silica, zeolite, and polyacrylonitrile (PAN).

[0062] According to another embodiment of the present invention, a crack repair electrode slurry may further include a binder dispersion to bind the catalyst nanoparticles together. The binder dispersion may be a mixture of a dispersion medium and a binder (ion conductor). For example, the dispersion medium may be appropriately modified depending on the type of the ion conductor.

[0063] In some embodiments of the present invention, the content of the binder dispersion may be 20 to 30 wt%, 21 to 29 wt%, 22 to 28 wt%, 23 to 27 wt%, 24 to 26 wt%, or 25 to 26 wt% based on the total weight of the electrode slurry for crack repair. According to some embodiments of the present invention, when the content of the binder dispersion satisfies the numerical range, the effect of binding functional nanoparticles to each other can be better implemented.

[0064] In some embodiments of the present invention, the content of the binder may be 5 to 25 wt%, 6 to 24 wt%, 7 to 23 wt%, 8 to 22 wt%, 10 to 20 wt%, 15 to 20 wt%, or 16 to 20 wt% based on the total weight of the binder dispersion. Here, the binder may mean the total solid content of the binder dispersion. According to some embodiments of the present invention, when the content of the binder satisfies the numerical range, the performance and physical durability of an electrode manufactured with the electrode slurry for crack repair can be further improved.

[0065] The above binder may be, for example, any one selected from the group consisting of fluorine-based ion conductors, hydrocarbon-based ion conductors, and mixtures thereof.

[0066] For example, the fluorine-based ion conductor may be any one selected from the group consisting of poly(perfluorosulfonic acid), poly(perfluorocarboxylic acid), a copolymer of tetrafluoroethylene and fluorovinyl ether containing a sulfonic acid group, a polystyrene-graft-ethylenetetrafluoroethylene copolymer, a polystyrene-graft-polytetrafluoroethylene copolymer, and mixtures thereof.

[0067] For example, the hydrocarbon-based ion conductor may be sulfonated polyimide (S-PI), sulfonated polyarylethersulfone (S-PAES), sulfonated polyetheretherketone (S-PEEK), sulfonated polybenzimidazole (S-PBI), sulfonated polysulfone (S-PSU), sulfonated polystyrene (S-PS), sulfonated polyphosphazene, sulfonated polyquinoxaline, sulfonated polyketone, sulfonated polyphenylene oxide, sulfonated polyethersulfone, sulfonated Sulfonated polyether ketone, sulfonated polyphenylene sulfone, sulfonated polyphenylene sulfide, sulfonated polyphenylene sulfide sulfone, sulfonated polyphenylene sulfide sulfone nitrile, sulfonated polyarylene ether, sulfonated polyarylene ether nitrile, sulfonated polyarylene ether ether nitrile,It may be any one selected from the group consisting of sulfonated polyarylene ether sulfone ketone and mixtures thereof.

[0068] The crack repair electrode slurry according to the present invention can be coated using any one method selected from the group consisting of slot-die coating, comma coating, spray coating, brushing, and doctor blade coating, for example. Since the crack repair electrode slurry can be applied using various coating methods, it can have the advantage of being easily applicable in industry.

[0069] 2. Catalyst layer for fuel cell and membrane-electrode assembly including same

[0070] According to another aspect of the present invention, a catalyst layer for a fuel cell repaired with the above-described crack repair electrode slurry and a membrane-electrode assembly including the same are provided.

[0071] Hereinafter, the configuration of the present invention will be described in detail with reference to Fig. 1a.

[0072] FIG. 1a is a cross-sectional view of a catalyst layer for a fuel cell with a crack repaired according to one embodiment of the present invention.

[0073] Referring to Fig. 1a, a catalyst layer (20) for a fuel cell according to the present invention may be disposed on at least one surface of a polymer electrolyte membrane (10). The catalyst layer (20) for a fuel cell may include a first catalyst layer (21) and a second catalyst layer (23) disposed on the first catalyst layer (21). Specifically, the first catalyst layer (21) may be an electrode in which a crack is formed due to shrinkage or expansion of the polymer electrolyte membrane (10), and the second catalyst layer (23) may be an electrode formed with the electrode slurry for crack repair.

[0074] The first catalyst layer (21) may include a crack region (CR) in which a crack is formed and a peripheral region (PR) of the crack region (CR). The electrode slurry for crack repair according to the present invention can effectively repair cracks that have occurred in the electrode by filling both the crack region (CR) and the peripheral region (PR) of the first catalyst layer (21), and at the same time, provide a catalyst layer (20) for a fuel cell having a uniform thickness.

[0075] The polymer electrolyte membrane (10) according to the present invention is not particularly limited, but may be, for example, a single membrane or a reinforced composite membrane in the relevant technical field. The reinforced composite membrane may be a composite membrane in which an ionomer is impregnated into a porous support to form an ionomer layer on the surface to enhance durability. The ionomer may be the same as or different from the ion conductor.

[0076] According to another aspect of the present invention, a catalyst layer for a fuel cell is provided, comprising: a first catalyst layer including a crack region; and a second catalyst layer on the first catalyst layer, wherein a portion of the second catalyst layer corresponding to the crack region extends along the crack surface and includes a first region including a first binder and a second region different from the first region and including a second binder, wherein a content of the first binder per unit volume of the first region is higher than a content of the second binder per unit volume of the second region.

[0077] Figure 1b is an enlarged view of a portion of the second catalyst layer positioned at a position corresponding to the crack area of ​​Figure 1a.

[0078] Referring to FIGS. 1A and 1B, a portion (CR') of the second catalyst layer corresponding to the crack region (CR) according to the present invention includes a first region (CR1) and a second region (CR2). Specifically, the first region (CR1) may be different from the second region (CR2). In some examples, the first region (CR1) may overlap the second region (CR2) in a direction intersecting the direction in which the crack surface (22) extends. In some examples, the first region (CR1) may be interposed between the second region (CR2) and the crack surface (22).

[0079] In the first region (CR1) according to the present invention, the content of binder (ionomer) per unit volume is distributed higher than in the second region (CR2), so that not only can the ion conductivity due to the ion channel be further increased, but also the binding force between catalyst particles can be further increased, thereby increasing the durability of the catalyst layer.

[0080] In some embodiments of the present invention, the height (h) of the first region (CR1) may be greater than 0 μm and less than or equal to 2 μm, and may be from 0.1 μm to 1.8 μm in a direction intersecting the direction in which the crack surface (22) extends. For example, the direction intersecting the direction in which the crack surface (22) extends may be a direction toward the inside or center of a portion (CR') of the second catalyst layer, and specifically, may be a direction perpendicular to the direction in which the crack surface (22) extends (e.g., a direction of a normal vector of the crack surface). Here, the direction in which the crack surface (22) extends may be any one of several directions that the crack surface can define.

[0081] In some examples, the shape of the crack surface (22) is not particularly limited, but may specifically be V-shaped in cross-section. In some other examples, the crack surface (22) may be formed irregularly or randomly as an interface where the first and second catalyst layers (21, 23) come into contact.

[0082] The first region (CR1) according to the present invention comprises a first binder. Specifically, the first binder can improve the adhesion between catalyst particles included in the first region and simultaneously provide an ion path. For example, the first binder may be any one selected from the group consisting of the above-described fluorine-based ion conductor, hydrocarbon-based ion conductor, and mixtures thereof.

[0083] The second region (CR2) according to the present invention comprises a second binder. Specifically, the second binder can improve the adhesion between catalyst particles included in the second region and simultaneously provide an ion path. For example, the second binder may be any one selected from the group consisting of the above-described fluorine-based ion conductor, hydrocarbon-based ion conductor, and mixtures thereof.

[0084] In some examples, the first and second binders may be the same or different from each other. Here, being the same or different from each other may mean that the types and properties of the binders are both the same or different.

[0085] The content of the first binder per unit volume of the first region (CR1) according to the present invention is higher than the content of the second binder per unit volume of the second region (CR2). Specifically, by adjusting the content of the first binder per unit volume of the first region to be higher than the content of the second binder per unit volume of the second region, not only can the ionic conductivity of the membrane-electrode assembly be further increased, but also the binding force between catalyst particles can be further increased, thereby increasing the durability of the catalyst layer.

[0086] In some embodiments of the present invention, the concentration of the binder per unit volume contained in the portion (CR') of the second catalyst layer corresponding to the crack area may increase from the inside of the portion (CR') of the second catalyst layer toward the crack surface. According to some embodiments of the present invention, since the concentration of the binder per unit volume increases from the inside of the portion (CR') of the second catalyst layer toward the crack surface, not only can the ionic conductivity of the membrane-electrode assembly be further increased, but also the bonding force between catalyst particles can be further increased, thereby increasing the durability of the catalyst layer.

[0087] According to another aspect of the present invention, a method for manufacturing a catalyst layer for a fuel cell may be provided, comprising the steps of: (S1) preparing an electrode having a crack formed therein; (S2) applying an electrode slurry for crack repair of some embodiments onto one surface of the electrode having the crack formed therein; and (S3) drying the resultant of step (S2). For example, the electrode having the crack formed therein may be a first catalyst layer.

[0088] 3. Fuel cell

[0089] Figure 2 is a schematic diagram illustrating a fuel cell according to one embodiment of the present invention.

[0090] According to another aspect of the present invention, a fuel cell including the membrane-electrode assembly is provided.

[0091] Referring to FIG. 2, a fuel cell (200) according to the present invention may include a fuel supply unit (210) that supplies a mixed fuel in which fuel and water are mixed, a reforming unit (220) that reforms the mixed fuel to generate a reformed gas containing hydrogen gas, a stack (230) that generates electrical energy by causing an electrochemical reaction between the reformed gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizer, and an oxidizer supply unit (240) that supplies an oxidizer to the reforming unit (220) and the stack (230).

[0092] The above stack (230) may be equipped with a plurality of unit cells that generate electrical energy by inducing an oxidation / reduction reaction of a reforming gas containing hydrogen gas supplied from the reforming unit (220) and an oxidizing agent supplied from the oxidizing agent supply unit (240).

[0093] Each unit cell refers to a unit cell that generates electricity, and may include the membrane-electrode assembly that oxidizes / reduces oxygen in a reforming gas containing hydrogen gas and an oxidizing agent, and a separator (also called a bipolar plate, hereinafter referred to as a "separator") for supplying the reforming gas containing hydrogen gas and the oxidizing agent to the membrane-electrode assembly. The separator is positioned on both sides of the membrane-electrode assembly with the membrane-electrode assembly at the center. At this time, the separator plates each positioned at the outermost side of the stack are specifically referred to as end plates.

[0094] Among the above separators, the end plate may be provided with a first supply pipe (231) in the shape of a pipe for injecting reformed gas containing hydrogen gas supplied from the reforming unit (220), and a second supply pipe (232) in the shape of a pipe for injecting oxygen gas, and the other end plate may be provided with a first discharge pipe (233) for discharging reformed gas containing hydrogen gas that is ultimately unreacted and remains in a plurality of unit cells to the outside, and a second discharge pipe (234) for discharging oxidant that is ultimately unreacted and remains in the unit cells to the outside.

[0095] In the above fuel cell, the separator, fuel supply unit, and oxidizer supply unit constituting the electricity generation unit are used in a typical fuel cell, and therefore, a detailed description thereof is omitted in this specification.

[0096] According to some embodiments of the present invention, 80 oWhen 0.45 V was applied to the fuel cell under C, 100% RH, and atmospheric pressure conditions, the current density measured using the fuel cell unit cell evaluation equipment was 2500 mA / cm 2 It could be strange.

[0097] In some embodiments of the present invention, after performing 20,000 wet-dry cycles under wet 2-minute-dry 2-minute repeated cycle conditions under air / air conditions at 80°C, the hydrogen crossover current density of the fuel cell is 15 mA / cm. 2 Below, 14 mA / cm 2 Below, 13 mA / cm 2 Below, 12 mA / cm 2 Below, 11 mA / cm 2 or less, or 10 mA / cm 2 It may be as follows. At this time, the lower the hydrogen permeation current density of the fuel cell, the better the crack repair effect.

[0098] Hereinafter, embodiments of the present invention will be described in detail so that those skilled in the art can easily implement the present invention. However, this is merely an example, and the scope of the present invention is not limited by the following contents.

[0099] [Manufacturing Preparation Example: Preparation of Materials]

[0100] Catalytic nanoparticles, with an average size of about 3 to 4 nm (D 50 ) having an average size (D) of about 30 to 40 nm. 50 ) was used, and ethanol was used as a solvent having a surface tension of less than 40 mN / m at 20°C, and water was used as a solvent having a surface tension of more than 40 mN / m at 20°C, and CeO2 with an average particle size of 15 nm was used as a radical scavenger, and OER catalyst nanoparticles with an average size (D 50) was used as IrO2 with a particle size of 30 nm, h-BN with an average particle size of 150 nm was used as heat-dissipating nanoparticles, porous silica (aerogel) with an average particle size of 50 nm was used as hygroscopic nanoparticles, and commercial Nafion D2020 dispersion (20 wt% PFSA) mixed with PFSA (perfluorosulfonic acid) and propanol (dispersing medium) was used as a binder.

[0101] [Manufacturing Example 1: Manufacturing of electrode slurry for crack repair]

[0102] <Comparative Example 1: Commercial electrode slurry that does not satisfy the parameters>

[0103] An electrode slurry was prepared consisting of 70 wt% of a solvent (water) having a surface tension exceeding 40 mN / m at 20°C, 5 wt% of a catalyst nanoparticle (Pt / C), and 25 wt% of a binder (Nafion solid content 20 wt%).

[0104] <Comparative Example 2: Commercial electrode slurry that does not satisfy the parameters>

[0105] An electrode slurry was prepared by comprising 50 wt% of a solvent (ethanol) having a surface tension of 40 mN / m or less at 20°C, 8 wt% of a solvent (water) having a surface tension of more than 40 mN / m at 20°C, 7 wt% of a catalyst nanoparticle (Pt / C), and 35 wt% of a binder (Nafion solid content 20 wt%).

[0106] <Example 1: Electrode slurry for crack repair satisfying parameters>

[0107] A crack repair electrode slurry was prepared, comprising 65 wt% of a first solvent (ethanol) having a surface tension of 40 mN / m or less at 20°C, 5 wt% of a second solvent (water) having a surface tension of more than 40 mN / m at 20°C, 5 wt% of a catalyst nanoparticle (Pt / C), and 25 wt% of a binder (Nafion solid content 20 wt%).

[0108] <Example 2: Crack repair electrode slurry containing radical scavenger>

[0109] An electrode slurry for crack repair was prepared in the same manner as in Example 1, except that 4.9 wt% of catalyst nanoparticles (Pt / C) and 0.1 wt% of radical scavenger (CeO2) were used instead of 5 wt% of catalyst nanoparticles (Pt / C) in Example 1.

[0110] <Example 3: Crack repair electrode slurry containing heat-dissipating nanoparticles>

[0111] An electrode slurry for crack repair was prepared in the same manner as in Example 1, except that 4.9 wt% of catalytic nanoparticles (Pt / C) and 0.1 wt% of heat-dissipating nanoparticles (h-BN) were used instead of 5 wt% of catalytic nanoparticles (Pt / C) in Example 1.

[0112] <Example 4: Crack repair electrode slurry containing hygroscopic nanoparticles>

[0113] In Example 1, instead of 5 wt% of catalytic nanoparticles (Pt / C), 4.9 wt% of catalytic nanoparticles (Pt / C) and hygroscopic nanoparticles (BET specific surface area of ​​about 640 m 2 An electrode slurry for crack repair was prepared in the same manner as in Example 1, except that 0.1 wt% of porous silica ( / g) was used.

[0114] <Example 5: Crack repair electrode slurry containing OER catalyst nanoparticles>

[0115] An electrode slurry for crack repair was prepared in the same manner as in Example 1, except that 4.9 wt% of catalyst nanoparticles (Pt / C) and 0.1 wt% of OER catalyst nanoparticles (IrO2) were used instead of 5 wt% of catalyst nanoparticles (Pt / C) in Example 1.

[0116] [Experimental Example 1: Characteristic Analysis of Electrode Slurry for Crack Repair]

[0117] The viscosity, surface tension and total solid content of the electrode slurry for crack repair according to the comparative examples and examples above were measured and are shown in Table 1 below.

[0118] 1) Viscosity (cp)

[0119] The viscosity of the above crack repair electrode slurry was measured using a Brookfield viscosity measuring device at 20°C.

[0120] 2) Surface tension (mN / m)

[0121] The surface tension of the electrode slurry for crack repair was measured at 20°C using a surface tension measuring device (Kruss K20) based on the De Nouy ring method.

[0122] 3) Total solids content

[0123] The electrode slurry for crack repair was sufficiently dried at a temperature of 100℃ or higher until the solvent and dispersion medium completely evaporated. The total solids content was measured based on the total weight of the electrode slurry for crack repair, and the total solids content ratio was calculated.

[0124] Viscosity at 20°C (cp) Surface tension at 20°C (mN / m) Total solids content (wt%) Comparative Example 11207210 Comparative Example 2485814 Example 1424910 Example 2454610 Example 3485010 Example 4404510 Example 5384310

[0125] [Experimental Example 2: Photograph of catalyst layer for fuel cell to which electrode slurry for crack repair is applied] FIG. 3 is an optical microscope photograph of a catalyst layer for fuel cell to which electrode slurry for crack repair is applied according to Example 1 and Comparative Example 1. Referring to FIG. 3, it can be confirmed that the number of cracks formed on the surface of the catalyst layer for fuel cell repaired with the electrode slurry for crack repair according to Example 1 is significantly smaller than that of Comparative Example 1.

[0126] [Manufacturing Example 2: Manufacturing of a Membrane-Electrode Assembly]

[0127] Each of the electrode slurries for crack repair according to Manufacturing Example 1 was slot die-coated with a wet thickness of 100 μm on a catalyst layer having a crack formed inside and disposed on one side of a polymer electrolyte membrane, and then dried at 90°C for 10 minutes to manufacture a membrane-electrode assembly including a catalyst layer for a fuel cell with the crack repaired.

[0128] [Experimental Example 3: Performance and Durability Evaluation of Membrane-Electrode Assemblies]

[0129] For the membrane-electrode assembly according to the above manufacturing example 2, the performance and durability were evaluated using the following measurement methods, and the results are shown in Table 2 below.

[0130] 1) Performance

[0131] 80 o The performance of the membrane-electrode assembly according to Manufacturing Example 2 was evaluated by measuring the voltage according to the current density using Scitech's fuel cell unit cell evaluation equipment under C, 100% RH, and atmospheric pressure conditions.

[0132] Figure 4 is a graph showing the performance of membrane-electrode assemblies according to Comparative Examples 1 and 2 and Example 1.

[0133] Referring to Fig. 4, Example 1, in which the crack was repaired, exhibited a higher current density at the same voltage compared to Comparative Examples 1 and 2, in which the crack was repaired.

[0134] 2) Physical durability and crack repair effect

[0135] The evaluation was conducted based on the Wet-dry durability evaluation protocol of the U.S. Department of Energy (DOE). Specifically, in order to evaluate the physical durability of the membrane-electrode assembly, 20,000 wet-dry cycles were performed under repeated 2-minute wet-dry cycles under air / air conditions at 80°C, and the hydrogen crossover current density was measured. The results are shown in Table 2. The membrane-electrode assemblies of the examples met the DOE standard (H2crossover ≤ 15 mA / cm 2 It showed a very stable physical durability satisfying 20,000 wet-dry cycles, indicating a crack repair effect. At this time, the hydrogen permeation current density was 10 mA / cm 2 If it is below, it may mean that the crack repair effect is better.

[0136] Sample hydrogen permeation current density (mA / cm) 2 )@0.2VW / D BeforeW / D AfterComparative Example 14.511.7Comparative Example 24.310.9Example 13.33.8Example 23.54.0Example 33.23.6Example 43.23.6Example 53.43.8

[0137] Referring to Table 2 above, it was confirmed that the membrane-electrode assemblies repaired with the electrode slurries of Examples 1 to 5 that satisfied the viscosity, surface tension, and total solids content at 20°C exhibited more stable physical durability than the membrane-electrode assemblies repaired with the electrode slurries of Comparative Examples 1 and 2. From the experimental results above, it can be inferred that if at least one of the four factors consisting of the content of the first solvent, the viscosity of the electrode slurry for crack repair, the surface tension, and the total solids content does not satisfy the appropriate range, neither the performance nor the crack repair effect of the repaired membrane-electrode assembly is achieved.

[0138] Although the preferred embodiments of the present invention have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0139] [Explanation of symbols]

[0140] 10: Polymer electrolyte membrane 20: Catalyst layer for fuel cell

[0141] 21: First catalyst layer 22: Crack surface

[0142] 23: Second catalyst layer CR: Crack region

[0143] PR: Peripheral area CR': Part of the second catalyst layer corresponding to the crack area

Claims

1. Containing at least 60 wt% of a first solvent having a surface tension of 40 mN / m or less at 20°C; 20 o At C, the surface tension is less than 65 mN / m, The viscosity is less than 100 cP at 20℃, The total solid content is 12% by weight or less, Electrode slurry for crack repair.

2. In paragraph 1, The above first solvent is, Containing at least one selected from the group consisting of alcohol, acetic acid, propionic acid, oleic acid, carbon tetrachloride, pyrrole, and pyridine. Electrode slurry for crack repair.

3. In paragraph 1, Further comprising a second solvent having a surface tension exceeding 40 mN / m at 20°C; Based on the total weight of the above crack repair electrode slurry, the content of the second solvent is 10 wt% or less. Electrode slurry for crack repair.

4. In paragraph 1, further comprising functional nanoparticles; Electrode slurry for crack repair.

5. In paragraph 4, The above functional nanoparticles are, Containing at least one selected from the group consisting of radical scavengers, catalytic nanoparticles, heat-dissipating nanoparticles and hygroscopic nanoparticles. Electrode slurry for crack repair.

6. In paragraph 1, A binder dispersion comprising a binder; further comprising: The above binder, Any one selected from the group consisting of fluorine-based ion conductors, hydrocarbon-based ion conductors and mixtures thereof, Electrode slurry for crack repair.

7. A first catalyst layer including a crack region; and A second catalyst layer on the first catalyst layer; A portion of the second catalyst layer corresponding to the crack area, a first region extending along the crack face and comprising a first binder; and A second region different from the first region and including a second binder, The content of the first binder per unit volume of the first region is higher than the content of the second binder per unit volume of the second region. Catalyst layer for fuel cells.

8. In paragraph 7, In a direction intersecting the direction in which the crack surface extends, the height of the first region is greater than 0 ㎛ and less than or equal to 2 ㎛. Catalyst layer for fuel cells.

9. A membrane-electrode assembly comprising a catalyst layer for a fuel cell according to Article 7.

10. A fuel cell comprising a membrane-electrode assembly according to paragraph 9.

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