Hollow fiber membrane for fuel cell humidifier, and humidifier and fuel cell system comprising same

Abstract

The present invention relates to a hollow fiber membrane for a fuel cell humidifier, a method for preparing the same, and a humidifier and a fuel cell system comprising the same, in which the hollow fiber membrane comprises a polymer and an antioxidant, and the antioxidant is provided on an inner surface and / or an outer surface.

Description

Technical Field

[0001] This invention relates to a novel hollow fiber membrane for a fuel cell humidifier, as well as a humidifier and a fuel cell system including the hollow fiber membrane. Background Technology

[0002] A fuel cell is a power-generating battery that converts the chemical energy of hydrogen and oxygen into electrical energy through an electrochemical reaction. Unlike conventional chemical batteries such as dry cell batteries or storage batteries, the advantage of fuel cells is that they can generate electricity continuously as long as hydrogen and oxygen are supplied, and there is no heat loss, making them approximately twice as efficient as internal combustion engines.

[0003] Furthermore, because fuel cells use hydrogen and oxygen as raw materials to produce water as a byproduct, they are environmentally friendly power generation devices that do not generate pollutants. Therefore, fuel cells not only have the advantage of being environmentally friendly, but also reduce concerns about resource depletion caused by increased energy consumption.

[0004] Fuel cells can be classified into polymer electrolyte membrane fuel cells (PEMFC), phosphoric acid fuel cells (PAFC), molten carbonate fuel cells (MCFC), solid oxide fuel cells (SOFC), and alkaline fuel cells (AFC).

[0005] Among them, PEMFCs are known to be suitable for transportation systems because they can operate at lower temperatures and have higher power density than other fuel cells.

[0006] Meanwhile, during the operation of a PEMFC, typically 2 moles of hydrogen react with 1 mole of oxygen in the fuel cell stack to form water. However, when incomplete reactions occur, byproducts such as peroxides or hydroxyl radicals may be generated.

[0007] The peroxides or hydroxyl radicals generated in this way may cause degradation of the polymer electrolyte membrane in the fuel cell stack, and techniques have been reported to incorporate small amounts of inorganic materials or other additives into the polymer electrolyte membrane to prevent such degradation.

[0008] However, since a certain level of pores must be distributed in the polymer electrolyte membrane in order for ions to pass through, the amount of inorganic materials such as inorganic particles is limited to a certain value to improve durability.

[0009] Therefore, there is still a need for technologies that can prevent the degradation of polymer electrolyte membranes even during long-term operation of fuel cells. Summary of the Invention

[0010] Technical issues

[0011] The present invention aims to protect the polymer electrolyte membrane from the effects of peroxides and / or hydroxyl radicals continuously generated in the fuel cell stack, thereby improving the durability of the fuel cell system.

[0012] Technical solution

[0013] According to one aspect, a hollow fiber membrane for a fuel cell humidifier is provided, the hollow fiber membrane comprising a polymer and an antioxidant, wherein the antioxidant is disposed on the inner and / or outer surfaces of the hollow fiber membrane.

[0014] According to another aspect, a method for preparing a hollow fiber membrane for a fuel cell humidifier is provided. The method includes preparing a casting solution containing a polymer and an antioxidant for forming a hollow fiber membrane, discharging the casting solution into a coagulation bath through a tubular spinning device, coagulating the spinning solution discharged into the coagulation bath in the coagulation bath, and then winding and drying to obtain the hollow fiber membrane, wherein the antioxidant is disposed on the inner surface and / or outer surface of the hollow fiber membrane.

[0015] According to another aspect, a humidifier for a fuel cell is provided, which includes the hollow fiber membrane.

[0016] According to another aspect, a fuel cell system is provided, comprising a fuel cell stack and a humidifier for the fuel cell, the fuel cell stack including a fuel cell comprising a polymer electrolyte membrane, the humidifier being in communication with the fuel cell stack, wherein an antioxidant flows out from the humidifier and flows into the fuel cell stack at a rate of 1 μg / 1000 hr or more.

[0017] Beneficial effects

[0018] In one aspect of the hollow fiber membrane, by distributing or dispersing an antioxidant on the inner and / or outer surfaces of the hollow fiber membrane, during the humidification of external air in the hollow fiber membrane, the antioxidant flows out of the hollow fiber membrane and into the fuel cell stack at a rate of 1 μg / 1000hr or more, thereby effectively preventing the degradation of the polymer electrolyte membrane of the fuel cell in the fuel cell stack and improving durability. Attached Figure Description

[0019] Figure 1 and Figure 2 This is an exploded perspective view of a humidifier for a fuel cell according to an embodiment of the present invention.

[0020] Figures 3 to 6 This is an enlarged cross-sectional view of a hollow fiber membrane according to an embodiment of the present invention.

[0021] Figure 7 and Figure 8This is a block diagram illustrating the configuration of a fuel cell system according to an embodiment of the present invention. Detailed Implementation

[0022] In the following description, since the inventive concept allows for various variations and many implementations, specific embodiments will be shown in the accompanying drawings and described in detail in the written description. However, this is not intended to limit the inventive concept to a particular mode of implementation, and it should be understood that all variations, equivalents, and alternatives without departing from the spirit and scope of the invention are included in the inventive concept.

[0023] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the inventive concept. Expressions used in the singular encompass those used in the plural unless they have a distinct meaning in the context. As used herein, it should be understood that terms such as “comprising,” “having,” and “including” are intended to indicate the presence of features, quantities, steps, actions, components, portions, ingredients, materials, or combinations thereof disclosed in the specification, and are not intended to exclude the possibility that one or more other features, quantities, steps, actions, components, portions, ingredients, materials, or combinations thereof may be present or added.

[0024] When describing a component as "connected" or "joined" to another component, it should be understood that the component may be directly connected or joined to the other component, or that new other components may reappear between the component and the other component. On the other hand, it should be understood that when describing a component as "directly connected" or "directly joined" to another component, there are no new other components between the component and the other component.

[0025] Throughout this specification, it should be understood that when a component such as a layer, film, region, or plate is referred to as being "on" another component, that component may be directly on the other component, or an intermediate component may be present on it. Throughout this specification, while terms such as "first" and "second" may be used to describe various components, these components are not limited by the terms used above. The terms above are used only to distinguish one component from another.

[0026] As used herein, the term "polymer" refers to a polymer formed by the polymerization of one or more monomer units and has the meaning of encompassing both polymer resins and polymer macromolecules.

[0027] The implementation methods described in this article are merely examples and can be modified in various ways.

[0028] According to one aspect, a hollow fiber membrane comprising a polymer and an antioxidant is provided, wherein the antioxidant is disposed on an inner surface and / or an outer surface.

[0029] Antioxidants can be disposed on at least one surface of the inner and outer surfaces of the hollow fiber membrane and can come into contact with external air passing through the humidified membrane, causing a portion of the antioxidant to flow out.

[0030] According to one embodiment, the hollow fiber membrane may have a network structure formed of a polymer, and may further include an antioxidant within the network structure.

[0031] According to one embodiment, the antioxidant can be dispersed and present in the polymer constituting the hollow fiber membrane. For example, the antioxidant can be in particulate form and can be dispersed and present in a structure embedded in the polymer. That is, the antioxidant can be dispersed and present within the network structure without forming bonds with the polymer that forms the framework of the hollow fiber membrane.

[0032] Since the antioxidant does not form bonds with the hollow fiber membrane, it can flow out and be transported to the fuel cell stack along with the humidified air as outside air passes through the hollow part of the hollow fiber membrane.

[0033] In one embodiment, the antioxidant can be configured to efflux from the hollow fiber membrane at a rate of 1 μg / 1000 hr or higher. The antioxidant can efflux in such or greater amounts, thereby suppressing chemical degradation of the polymer electrolyte membrane in the fuel cell stack caused by oxidizing agents.

[0034] According to one embodiment, the antioxidant can be included in the hollow fiber membrane by the preparation methods described below. For example, the antioxidant can be included in the hollow fiber membrane by mixing the antioxidant with the casting solution during membrane formation; the antioxidant can be included in the hollow fiber membrane during a phase inversion process in which the antioxidant is contained in the core liquid and discharged; or the antioxidant can be included in the hollow fiber membrane by preparing the hollow fiber membrane and then impregnating the hollow portion with an antioxidant solution to form an antioxidant coating on the inner surface of the hollow fiber membrane.

[0035] According to one embodiment, the antioxidant can be in a dispersed form or in the form of a coating on at least one surface of the inner and outer surfaces of the hollow fiber membrane. For example, the antioxidant can be in the form of particles attached to at least one surface of the inner and outer surfaces of the hollow fiber membrane, or multiple particles forming a coating.

[0036] For example, antioxidant particles can be evenly distributed across the entire surface without clogging the pores of the hollow fiber membrane.

[0037] According to one embodiment, an antioxidant may be included in an amount of 0.1 to 5 parts by weight relative to 100 parts by weight of the polymer.

[0038] According to one embodiment, the antioxidant can form an antioxidant coating disposed on at least one surface of the hollow fiber membrane, both the inner and outer surfaces. In this configuration, the antioxidant coating can be configured to allow a certain amount of antioxidant to leak out upon contact with outside air. For this leakage, the antioxidant should not form chemical bonds with the membrane's main polymer, and it is advantageous for the antioxidant to be located on the inner surface of the membrane. Therefore, when forming a humidifying membrane, crosslinking agents or additives that could cause crosslinking between the antioxidant and the main polymer should be excluded.

[0039] For example, antioxidant coatings can have a thickness of 1 μm to 50 μm to allow a certain amount of antioxidant to escape. When the thickness of the antioxidant coating is less than 1 μm, it may be difficult to obtain a sufficient amount of antioxidant efflux through contact with the outside air, and when the thickness exceeds 50 μm, it may be difficult to achieve sufficient moisture exchange with the outside air because the antioxidant coating becomes a resistance layer to the flow of outside air.

[0040] According to one embodiment, the antioxidant or antioxidant coating particles may cover all or part of the inner or outer surface of the hollow fiber membrane.

[0041] According to one embodiment, an antioxidant may be included in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the polymer forming the hollow fiber membrane.

[0042] When the antioxidant content is less than 0.01 parts by weight, it may be insufficient to prevent the deterioration of the hollow fiber membrane caused by peroxides or hydroxyl radicals generated during fuel cell reactions. When the antioxidant content is greater than 5 parts by weight, the pores of the hollow fiber membrane become blocked, reducing the moisture exchange performance and thus reducing the function of the membrane humidifier.

[0043] According to one embodiment, antioxidants may include phenolic antioxidants, amine antioxidants, metal antioxidants, organometallic antioxidants, sulfur or phosphorus antioxidants, or combinations thereof.

[0044] For example, phenolic antioxidants may include Irganox 1010 (pentaerythritol tetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, manufactured by BASF SE), Irganox 1076 (octadecyl 3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate, manufactured by BASF SE), Irganox 1330 (3,3',3',5',5'-hexa-tert-butyl-α,α',α”-(trimethylbenzyl-2,4,6-triyl)tri-p-cresol, manufactured by BASF SE), Irganox 3114 (1,3,5-tris(3,5-di-tert-butyl-4-hydroxybenzyl)-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF SE), Irganox... 3790 (1,3,5-tris[(4-tert-butyl-3-hydroxy-2,6-dimethylphenyl)methyl]-1,3,5-triazine-2,4,6(1H,3H,5H)-trione, manufactured by BASF SE), Irganox 1035 (thiodiethylidene bis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate], manufactured by BASF SE), Irganox 1135 (C7-C9 branched alkyl ester of 3,5-bis(1,1-dimethylethyl)-4-hydroxyphenylpropionic acid, manufactured by BASF SE), Irganox 1520L (4,6-bis(octylthiomethyl)-o-cresol, manufactured by BASF SE), Irganox 3125 (manufactured by BASF SE), Irganox 565 (2,4-bis(n-octylthio)-6-(4-hydroxy-3',5'-di-tert-butylaniline)-1,3,5-triazine, manufactured by BASF SE), ADEKAstab® AO-80 (3,9-bis[2-(3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propionyloxy)-1,1-dimethylethyl]-2,4,8,10-tetraoxellaspiro[5.5]undecane, manufactured by Adico Corporation), Smilizer® BHT, GA-80 and GS (all manufactured by Sumitomo Chemical Co., Ltd.), Cyanox® 1790 (manufactured by Cytec Industries Co., Ltd.) and Vitamin E (manufactured by Eisai Co., Ltd.) or any combination thereof.

[0045] Amine antioxidants may include phenyl-α-naphthylamine, phenyl-β-naphthylamine, N,N'-diphenyl-p-phenylenediamine, N,N'-dinathyl-p-phenylenediamine, hindered amine light stabilizers (HALS) compounds, or combinations thereof.

[0046] For example, phosphorus-based antioxidants may include tris(2,4-di-tert-butylphenyl) phosphite (Irgafos168), tris[2-[[2,4,8,10-tetra-tert-butyldibenzo[d,f][1,3,2]phosphine dioxane... -6-yl]oxy]ethyl]amine (Irgafos 12), bis(2,4-bis(1,1-dimethylethyl)-6-methylphenyl)ethyl phosphite (Irgafos 38), Adekastab 329K, Adekastab PEP36, Adekastab PEP-8, Sandstab P-EPQ, Weston 618, Weston 619G, Ultranox 626, (6-[3-(3-tert-butyl-4-hydroxy-5-methylphenyl)propoxy]-2,4,8,10-tetratert-butyldibenzo[d,f][1,3,2]dioxophosphorus (Smilizer GP) or combinations thereof.

[0047] For example, metal-based antioxidants may include cerium, nickel, tungsten, ruthenium, palladium, silver, rhodium, cesium, zirconium, cobalt, chromium, yttrium, manganese, iron, molybdenum, lead, vanadium, titanium, niobium, lanthanum, their ions, their oxides, their salts, or any mixture thereof.

[0048] For example, organometallic antioxidants may include Ce-crown complexes, Ce-phosphate complexes, Ce-bipyridine, or any mixture thereof.

[0049] For example, sulfur-based antioxidants may include dilauryl thiodipropionate (DLTDP), distearate thiodipropionate (DSTDP), di(tetrazyl) thiodipropionate (DMTDP), bis(2-methyl-4-(3-alkylthio)propionyloxy)-5-tert-butylphenol sulfide, tetra(methylene-3-(laurate)propionate)methane, or combinations thereof.

[0050] According to one embodiment, the hollow fiber membrane may include a polymer, which may be selected from known polymers suitable for forming hollow fiber membranes. For example, the polymer may include polyvinylidene fluoride (PVDF) polymers, polysulfone polymers, sulfonated polysulfones, cellulose acetate, cellulose triacetate, polymethyl methacrylate, Nafion, polystyrene (PS) polymers, polytetrafluoroethylene (PTFE) polymers, perfluorosulfonic acid (PFSA) polymers, polyphenylene sulfone (PPSU) polymers, polyethersulfone (PES) polymers, polyacrylonitrile (PAN) polymers, polyetherimide (PEI) polymers, polyimide (PI) polymers, or any combination of the above polymers.

[0051] For example, polymers may include polystyrene-based polymers.

[0052] Considering the required physical properties of hollow fiber membranes, hollow fiber membranes may include at least one of the polymers listed above as the main polymer, and may further include auxiliary polymers. For example, an auxiliary polymer is polyvinylpyrrolidone.

[0053] According to one embodiment, the polymer may be included in an amount of 90 parts by weight or more and less than 100 parts by weight or 95 to 99.999 parts by weight relative to 100 parts by weight of the hollow fiber membrane.

[0054] According to one embodiment, an auxiliary polymer may be included in an amount of 5 to 20 parts by weight relative to 100 parts by weight of the hollow fiber membrane.

[0055] According to one embodiment, the hollow fiber membrane can have a thickness of 0.5 nm to 1 mm.

[0056] According to one embodiment, the hollow fiber membrane may further comprise additives, such as surfactants, hydrophilic organic compounds, hydrophilic polymers, or crosslinking agents.

[0057] For example, additives may include at least one of polyethylene glycol, glycerin, diethylene glycol, triethylene glycol, ethanol, polyvinylpyrrolidone, water, zinc chloride, and lithium chloride.

[0058] Additives can be selected and added in appropriate amounts without impairing the original properties of the hollow fiber membrane. It will be apparent to those skilled in the art that other known materials can also be used in the preparation of hollow fiber membranes.

[0059] According to one aspect, a method for preparing a hollow fiber membrane for a fuel cell humidifier is provided, the method comprising providing a hollow fiber membrane configured to allow an antioxidant to flow out.

[0060] A humidifier supplies humidified air to the fuel cell stack. In this process, impurities in the humidified air can shorten the fuel cell's lifespan. Therefore, it is necessary to suppress the leaching of impurities caused by the decomposition of the hollow fiber material. Since hollow fibers are inherently formed from organic polymers, during fuel cell operation, when the hollow fibers are exposed to the high-temperature, high-humidity air generated from the stack, the polymer may deform or break down, or various impurity ions may be generated due to polymer decomposition. These impurities may be transported into the stack, leading to performance degradation of the fuel cell stack.

[0061] To address these issues and improve the durability of hollow fiber membranes, attempts have been made to add fluorinated materials as polymers or to provide a durable coating on the surface of the hollow fiber membrane. However, the addition of fluorinated materials and the application of durable coatings still have limitations, such as impairing the moisture exchange capacity of the hollow fiber membrane or reducing its heat resistance.

[0062] Therefore, while focusing on research into materials that cause hollow fiber membrane decomposition, the inventors also investigated a method for fundamentally removing oxidizing materials that flow into the membrane humidifier from the fuel cell stack along with hot and humid air. In this regard, since injecting a large amount of antioxidant into the fuel cell stack to remove oxidizing substances generated within the stack could become impurities and reduce efficiency, this invention was completed based on the insight that when the hollow fiber membrane included in the fuel cell humidifier is configured to allow a certain amount of antioxidant to flow out over a long period, the antioxidant can be continuously supplied to the fuel cell stack and contribute to the removal of oxidizing substances.

[0063] According to one embodiment, providing a hollow fiber membrane configured to allow antioxidant efflux may include preparing a casting solution for forming the hollow fiber membrane.

[0064] According to one embodiment, the method may include preparing a casting solution by mixing a polymer and an antioxidant in an organic solvent, wherein the spinning solution is obtained by mixing the antioxidant in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the polymer. In this case, the organic solvent used to prepare the casting solution may be a third solvent as described below, such as N-methyl-2-methylpyrrolidone.

[0065] The solvent may include at least one of a first solvent, a second solvent, and a third solvent. For example, the solvent may be a mixture of two of the first solvent, the second solvent, and the third solvent.

[0066] The first solvent may be a solvent that does not dissolve the polymer at room temperature (e.g., 23°C to 25°C) but can dissolve the polymer at high temperatures (e.g., above 80°C), and may include butanol, isobutanol, octanol, pentanol, isopentanol, dimethyl phthalate, diethyl phthalate, dibutyl phthalate, dioctyl phthalate, polyoxyethylene octylphenyl ether, or combinations thereof.

[0067] The second solvent may be a solvent that does not dissolve the polymer, and may include water, methanol, ethanol, isopropanol, acetone, hexane, pentane, benzene, toluene, carbon tetrachloride, o-dichlorobenzene, polyethylene glycol, or combinations thereof.

[0068] The third solvent can be a solvent that can dissolve the polymer even at room temperature, and can include N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, tetrahydrofuran, tetramethylurea, or trimethyl phosphate.

[0069] Considering the characteristics of polymer raw materials and the preparation of hollow fiber membranes with desired physical properties, those skilled in the art can use any one of the first solvent, the second solvent, and the third solvent, or a mixture of two or more of these solvents.

[0070] According to one embodiment, when the solvent is a mixture of two solvents, the mixing ratio of the solvents can be in the range of 1:9 to 9:1 by weight, but is not limited thereto, and those skilled in the art can select an appropriate range by taking into account the amount of polymer and antioxidant, the viscosity of the spinning solution, the porosity of the hollow fiber membrane and the physical properties of the final hollow fiber membrane.

[0071] According to one embodiment, the spinning solution may include a polymer forming the framework of the hollow fiber membrane, an antioxidant, and a solvent, and may further include additives as needed. The spinning solution has a structure in which the solvent is removed during the formation of the hollow fiber membrane, and the final product contains an antioxidant within the polymer framework.

[0072] According to one embodiment, the amount of polymer contained in the spinning solution can be in the range of 15 to 25 parts by weight relative to a total of 100 parts by weight. For example, the amount of polymer contained in the spinning solution can be in the range of 16 to 24 parts by weight, 17 to 23 parts by weight, 18 to 22 parts by weight, or 19 to 21 parts by weight.

[0073] According to one embodiment, the amount of antioxidant contained in the spinning solution may be greater than 0 to 5 parts by weight or 0.001 to 5 parts by weight relative to 100 parts by weight of the polymer forming the framework of the hollow fiber membrane.

[0074] According to one embodiment, when obtaining the spinning solution, taking into account the polymer, antioxidant, additives and solvent used, the temperature at which the polymer and antioxidant, as well as optional additives, are mixed in the solvent can be appropriately selected to be at room temperature or high temperature.

[0075] According to one embodiment, the time required to mix the spinning solution can be the time required for the polymer, antioxidant, and any additives to fully dissolve and / or disperse in the solvent.

[0076] According to one embodiment, the spinning solution can have a viscosity of 5000 cps to 50000 cps at a temperature of 35°C. When the viscosity of the spinning solution meets the above range, the spinning solution can be smoothly discharged through the spinneret without clogging.

[0077] To maintain the viscosity of the spinning solution within the aforementioned range, the temperature of the spinning nozzle can be adjusted to a temperature above a certain level. Alternatively, if necessary, the spinning solution can further contain a viscosity modifier to adjust the viscosity.

[0078] According to one embodiment, the spinning solution may further contain additives, taking into account the film-forming properties and porosity of the hollow fiber membrane, the dispersibility of the antioxidant, and the viscosity of the spinning solution.

[0079] For example, additives may include at least one of polyethylene glycol, glycerin, diethylene glycol, triethylene glycol, ethanol, polyvinylpyrrolidone, water, zinc chloride, and lithium chloride.

[0080] According to one embodiment, discharging the spinning solution into the coagulation bath may include discharging the discharged solution using a tubular spinning apparatus such as a two-tube spinning apparatus or a three-tube spinning apparatus, but one or more embodiments are not limited to this type of tube. Any discharge method capable of forming a hollow shape can be used without limitation.

[0081] According to one embodiment, when the spinning solution is discharged into the coagulation bath through a two-tube spinning apparatus, the composition of the spinning solution discharged from each tube of the two-tube apparatus can be the same or different. For example, when discharging the spinning solution using a three-tube spinning apparatus, the composition of the spinning solution through each tube can be the same or different. For example, when using a three-tube spinning apparatus, the composition of the spinning solution through the inner and outer tubes of the tubular structure can be the same, while the composition of the spinning solution through the middle tube between the inner and outer tubes can be different.

[0082] According to one embodiment, when discharging the spinning solution into the coagulation bath, the spinning temperature can be set to a temperature greater than or equal to the temperature used to mix the spinning solution. In this case, when using a multi-spinneret, the temperature of each spinneret can be set differently, so that the spinning solution can be optimally discharged at an appropriate temperature.

[0083] According to one embodiment, when discharging the spinning solution into the coagulation bath, the discharge rate can be in the range of 5 g / min to 100 g / min.

[0084] According to one embodiment, when the spinning solution is discharged through a tubular nozzle, the core solution can be simultaneously discharged into the hollow interior of the tube. The core solution may include a mixture of a second solvent and a third solvent.

[0085] According to one embodiment, the core solution can be prepared by mixing a second solvent and a third solvent in a volume ratio of 3:7 to 7:3. When the core solution meets the volume ratio range described above, the antioxidants contained in the spinning solution can be introduced into the hollow fiber membrane during the phase inversion process of the spinning material.

[0086] According to one embodiment, the core solution may further contain an antioxidant. Since the core solution also contains an antioxidant, the antioxidant can be dispersed on the inner surface of the hollow fiber membrane through phase separation during the hollow fiber membrane formation process. Thus, the antioxidant can be dispersed and present on the inner surface of the hollow fiber membrane at a high concentration. As described above, when the core solution containing the antioxidant is discharged simultaneously, the spinning solution may contain a small amount of antioxidant, or it may not contain any antioxidant.

[0087] According to one embodiment, the spun material discharged from the spinning device can come into contact with the coagulation liquid in the coagulation bath through an air gap.

[0088] The air gap can be the area where the spinning material comes into contact with air, or it can be supplied with artificial cooling air, taking into account the physical properties of the spinning material. For example, the length of the air gap can be set from 0.1 cm to 50 cm. The air gap is the section where a phase transformation occurs, through the exchange of moisture in the atmosphere with the organic solvent in the spinning solution. When the length of the air gap meets the above range, a sufficient phase transformation can occur, thereby obtaining a hollow fiber membrane with the desired pore structure.

[0089] The spinning material comes into contact with the coagulation liquid contained in the coagulation bath through an air gap, thereby solidifying to form a porous hollow fiber membrane.

[0090] According to one embodiment, the coagulation bath may be configured as a single coagulation bath, but one or more embodiments are not limited thereto. The coagulation bath may be configured such that two or more coagulation baths are placed consecutively. When two or more coagulation baths are present, the coagulating liquid used in each coagulation bath may be the same or different.

[0091] According to one embodiment, the coagulation solution contained in the coagulation bath is used to coagulate the discharge solution exiting through the spinneret into the form of a hollow fiber membrane. In this case, considering the porosity, pore structure, etc. of the hollow fiber membrane, those skilled in the art can appropriately select the coagulation solution from known coagulation solutions.

[0092] For example, an acidic solution or a second solvent such as water can be used as the coagulating liquid.

[0093] According to one embodiment, the hollow fiber membrane obtained by coagulation bath can undergo post-treatment.

[0094] According to one embodiment, post-processing may include chemical and / or physical treatment.

[0095] For example, post-treatment chemical processes may involve removing and drying the coagulated solution contained in the pores after the hollow fiber membrane is formed, and may include rinsing, washing, hot water treatment, etc. If necessary, the solutions used for rinsing, washing, hot water treatment, etc., may further contain antioxidants.

[0096] For example, physical treatments in post-processing can further include stretching or shrinking processes that control the size and shape of the pores inside the hollow fiber membrane to improve the strength and durability of the hollow fiber membrane.

[0097] According to one embodiment, after forming the hollow fiber membrane, a post-treatment can be performed whereby a solution containing a dissolved antioxidant is introduced into the hollow portion of the hollow fiber and then dried. This post-treatment allows an antioxidant coating to be formed on the inner surface of the hollow fiber membrane. This post-treatment of forming an antioxidant coating on the inner surface of the hollow fiber membrane can be performed separately from the above-described steps, or it can be performed after forming a hollow fiber membrane containing or without an antioxidant, with the aim of preparing a selective antioxidant coating only on its inner surface.

[0098] In the hollow fiber membrane for fuel cell humidifiers prepared by the above method, since the antioxidant is not bound to the hollow fiber membrane by a crosslinking agent or adhesive, but is dispersed inside the hollow fiber membrane or forms a coating on the inner surface, the antioxidant can easily dissolve into the outside air during the moisture exchange process of the hollow fiber membrane.

[0099] According to another aspect, a humidifier comprising a hollow fiber membrane is provided.

[0100] Regarding hollow fiber membranes, please refer to the above explanation; the following will refer to... Figure 1 and Figure 2 Instructions for humidifiers.

[0101] Figure 1 and Figure 2 This is a perspective view of a fuel cell humidifier 100 according to an embodiment of the present invention.

[0102] like Figure 1 and Figure 2 As shown, the humidifier 100 for fuel cells of the present invention includes an intermediate shell 110, a cover shell 120, a fixing part 130, and a hollow fiber membrane bundle 200.

[0103] Here, the hollow fiber membrane bundle 200 may have antioxidant particles distributed on the surface of each hollow fiber membrane, or may include an antioxidant coating on its surface. For a magnified view of the surface of the hollow fiber membrane, refer to... Figure 3 and Figure 4 .

[0104] The intermediate housing 110 is joined to the cover housing 120 to form the exterior of the humidifier 100 for a fuel cell. The intermediate housing 110 and the cover housing 120 can be made of rigid plastics such as polycarbonate or metal. The cross-sections of the intermediate housing 110 and the cover housing 120 in the width direction can have, for example, […]. Figure 1 The circular shape shown can also have, for example, the circular shape shown. Figure 2 The polygon shape shown can be a quadrilateral, square, trapezoid, parallelogram, pentagon, hexagon, etc., and can have rounded corners. Additionally, a circle can also be an ellipse.

[0105] The intermediate housing 110 has a second fluid inlet 112 for supplying the second fluid and a second fluid outlet 113 for discharging the second fluid.

[0106] exist Figure 1 and Figure 2 In the diagram, multiple hollow fiber membranes 210 are shown arranged in the intermediate housing 110 as a single hollow fiber membrane bundle 200, but the hollow fiber membranes 210 may also be separated and housed in two or more boxes arranged in the intermediate housing 110.

[0107] Fluid inlet / outlet 121 is formed in cover housing 120. Fluid inlet / outlet 121 formed in one cover housing 120 connected to the opposite end of intermediate housing 110 serves as a first fluid inlet, and fluid inlet / outlet 121 formed in the other cover housing 120 serves as a first fluid outlet. The first fluid flowing in through the fluid inlet / outlet 121 serving as the first fluid inlet travels through the internal channel (i.e., lumen) of the hollow fiber membrane 210 housed inside the intermediate housing 110, and then exits through the fluid inlet / outlet 121 serving as the first fluid outlet.

[0108] The ends of the hollow fiber membrane 210 are encapsulated in the fixing portion 130. The fixing portion 130 adheres to the hollow fiber membranes 210 and fills the gaps between the hollow fiber membranes 210 and the gap between the hollow fiber membranes 210 and the intermediate shell 110. Therefore, each of the opposite ends of the intermediate shell 110 is blocked by the fixing portion 130, and a channel for the passage of the second fluid is formed therein. The material of the fixing portion 130 is known, and its detailed description is omitted here.

[0109] Figures 3 to 6 This is an enlarged cross-sectional view showing a single hollow fiber in a hollow fiber membrane bundle according to an embodiment of the present invention. Figures 3 to 5The enlarged view illustrates an embodiment of the invention in which antioxidant particles or antioxidant coatings are disposed only on the outer surface of the hollow fiber membrane, but one or more embodiments are not necessarily limited thereto. Embodiments of the invention also correspond to the provision of antioxidant particles or antioxidant coatings on the inner surface of the hollow fiber membrane, or on both the inner and outer surfaces.

[0110] refer to Figures 3 to 6 Hollow fiber membranes 30, 40, 50, and 60 include cavities 300, 400, 500, and 600, wherein the cavities serve as channels for air movement and locations for moisture exchange. The hollow fiber membrane has an inner surface S2 facing the cavity and an outer surface S1 facing the outer side of the hollow fiber membrane. The hollow fiber membrane has a thickness region 310, 410, 510, or 610 between the inner surface S2 and the outer surface S1, and although not shown, the thickness region 310, 410, 510, or 610 has a porous structure. The porosity of the thickness region can be configured to allow moisture exchange between humid air supplied from the fuel cell stack and dry air supplied from outside air. Antioxidant particles 320 or 520 or an antioxidant coating 420 or 620 containing antioxidant particles are disposed on the outer surface S1 or the inner surface S2 of the hollow fiber membrane 30, 40, 50, or 60. In this configuration, the antioxidant particles 320 or 520 and the antioxidant coating 420 or 620 can be provided in an amount that does not close the pores disposed in the thickness regions 310, 410, 510, or 610. Furthermore, when the hollow fiber membranes 30, 40, 50, or 60 form a bundle, the antioxidant particles 320 or 520 and the antioxidant coating 420 or 620 can be configured not to close the gaps between adjacent hollow fiber membranes. That is, the thickness of the antioxidant coating 420 or 620 is configured not to exceed half the width of the gap between the hollow fiber membranes in the hollow fiber membrane bundle, and the antioxidant particles 320 or 520 are disposed in a manner that ensures uniform dispersion on the surface.

[0111] Although not shown, but except Figures 3 to 6 In addition to the structure shown, those skilled in the art will understand that structures with antioxidant particles and antioxidant coatings mixed on the inner or outer surface will not be described further here.

[0112] According to another aspect, a fuel cell system is provided, comprising a fuel cell stack and a humidifier, the fuel cell stack including a fuel cell containing a polymer electrolyte membrane, the humidifier being in communication with the fuel cell stack, wherein an antioxidant flows out of the humidifier and into the fuel cell stack at a rate of more than 1 μg / 1000 hr.

[0113] Reference Figure 7According to an embodiment of the present invention, a fuel cell system includes a fuel cell stack 1000, a hydrogen supply unit 2000, and an air supply unit 3000.

[0114] The fuel cell stack 1000 generates heat and steam by reacting hydrogen supplied from the hydrogen supply unit 2000 with oxygen supplied from the air supply unit 3000.

[0115] The fuel cell stack 1000 may include a membrane electrode assembly, an electrolyte membrane, a catalyst layer, cathode and anode electrodes, a gas diffusion layer, a separator, and gaskets, and each component may be manufactured using known methods with known materials.

[0116] The fuel cell stack 1000 generates electricity through a combined reaction of hydrogen and oxygen. Specifically, in the fuel cell stack 1000, hydrogen is supplied to the anode and oxygen to the cathode. At the anode, hydrogen ions are generated through the oxidation reaction of hydrogen, and the electrons generated at this time move to the cathode through wires. The hydrogen ions move to the cathode through the electrolyte membrane and come into contact with oxygen to form water vapor.

[0117] Because the oxygen reduction reaction at the cathode of a polymer electrolyte fuel cell proceeds with the intermediate reaction of hydrogen peroxide formation, hydrogen peroxide or hydroxyl radicals may be generated at the cathode. Furthermore, at the anode of a polymer electrolyte fuel cell, hydrogen peroxide or hydroxyl radicals may also be generated when oxygen molecules permeate through the polymer electrolyte membrane. The resulting hydrogen peroxide or hydroxyl radicals may lead to the degradation of the polymer electrolyte membrane, which is susceptible to oxidizing agents.

[0118] To prevent this degradation of the polymer electrolyte membrane, a method of introducing free radical scavengers onto the surface of the membrane has been proposed. However, when excessive free radical scavengers are used to improve durability, the pores of the ion exchange membrane become clogged, leading to a reduction in ion exchange capacity. Furthermore, during fuel cell operation, the free radical scavengers present on the surface of the polymer electrolyte membrane are lost, which reduces membrane durability and makes it difficult to achieve sufficient durability and lifespan characteristics.

[0119] The inventors of this invention conducted extensive research to address the degradation of fuel cell durability caused by hydrogen peroxide or hydroxyl radicals generated in the fuel cell stack. Based on the insight that fuel cell durability and lifespan characteristics are achieved when air containing antioxidants is continuously supplied from the humidifier 3200 included in the air supply unit 3000 located on the upstream side of the fuel cell stack, this invention was completed.

[0120] Specifically, the antioxidant flows out from the hollow fiber membrane included in the humidifier 3200 at a rate of more than 1 μg / 1000 hr and into the air flowing into the fuel cell stack.

[0121] The hydrogen supply unit 2000 supplies stored hydrogen to the fuel cell stack 1000. Any hydrogen supply unit can be used without restriction, as long as it can supply hydrogen to the fuel cell stack.

[0122] The air supply unit 3000 includes an air compressor 3100 that compresses outside air to generate a first fluid and a humidifier 3200 that humidifies the first fluid and delivers it to the fuel cell stack.

[0123] Air compressor 3100 receives outside air and supplies compressed first fluid to the humidifier. Air compressor 3100 can be a device for compressing fluids such as air, and may include, for example, a blower, a compressor, etc.

[0124] If necessary, a filter can be additionally installed before the air compressor inlet to block contaminants from entering, or a separate air filter can be provided.

[0125] The humidifier 3200 receives compressed air from the air compressor 3100 and then humidifies the air to supply the humidified air to the fuel cell stack.

[0126] The humidifier 3200 allows moisture exchange between air from outside and steam generated from the fuel cell stack 1000, and supplies humidified air to the fuel cell stack 1000.

[0127] According to another aspect, the fuel cell system includes a fuel cell stack 1000, a hydrogen supply unit 2000 for supplying hydrogen to the stack, an air supply unit 3000 for supplying air to the stack, and a filter unit. The air supply unit includes an air compressor 3100 and a humidifier 3200. The filter unit is disposed in the path of external air passing through the humidifier 3200 to the fuel cell stack and is configured to remove peroxides and / or hydroxyl radicals.

[0128] Reference Figure 8 The fuel cell system is described.

[0129] exist Figure 8 In the system, for the fuel cell stack 1000 and the hydrogen supply unit 2000, refer to Figure 7 The explanation, and refer to Figure 7 The description of humidifier 3200 also applies to air supply unit 3000, except that the hollow fiber membrane contained in humidifier 3200 does not contain antioxidants.

[0130] The filter unit 4000 may be disposed between the humidifier 3200 and the fuel cell stack 1000. Specifically, the filter unit 4000 may be disposed adjacent to the outlet of the outside air (e.g., the first fluid) passing through the humidifier, adjacent to the inlet of the first fluid flowing into the fuel cell stack, or adjacent to the path along which the first fluid moves between the humidifier and the fuel cell stack.

[0131] The filter unit 4000 may include a porous matrix and an antioxidant disposed on the surface of the porous matrix.

[0132] Porous matrices may include porous nonwoven fabrics. For example, the surface of a porous matrix may include a membrane with an average pore size of 50 nm to 10 μm. Porous matrices may optionally include either hydrophilic or hydrophobic membranes. For example, but not limited to, porous matrices may include membranes containing thermoplastic polymers, such as polyethylene, polypropylene, 1-octene, styrene, polyolefin (co)polymers, polyamides, poly-1-butene, poly-4-methyl-1-pentene, polyethersulfone, ethylene tetrafluoroethylene, polyvinylidene fluoride, polysulfone, polyacrylonitrile, polyamide, cellulose acetate, cellulose nitrate, regenerated cellulose, polyvinyl chloride, polycarbonate, polyethylene terephthalate, polyimide, polytetrafluoroethylene, ethylene trifluorochloroethylene, or combinations thereof.

[0133] Porous substrates can include any known substrate with a mesh-like shape.

[0134] Antioxidants can be provided on one surface or both opposite surfaces of the porous matrix. For example, antioxidants can be disposed on both opposite surfaces of the porous matrix, and the concentration of antioxidants disposed on the first surface facing the fuel cell stack 1000 can be higher than the concentration of antioxidants disposed on the second surface opposite to the first surface.

[0135] For information on antioxidants, please refer to the description above.

[0136] Hereinafter, embodiments and comparative examples will be used to describe the implementation of the present invention. However, the scope of the present invention is not limited to the embodiments.

[0137] Example

[0138] Example 1

[0139] A casting solution was prepared by mixing 20 wt% polystyrene (PS), 6 wt% polyvinylpyrrolidone (PVP), and 1 wt% antioxidant (Irganox 1010) with 73 wt% solvent N-methylpyrrolidone (NMP). A core solution was prepared by mixing NMP and ethanol at a volume ratio of 6:4. The casting solution was discharged through the outer tube of a dual-nozzle spray nozzle, and the core solution was discharged through the inner tube, thereby immersing the spinning material in a coagulation bath containing a coagulation solution. The spinning material contacted the coagulation solution in the coagulation bath to form a hollow fiber membrane. In this case, a 1:1 mixture of water and polyethylene glycol (PEG) was used as the coagulation solution, and the temperature was adjusted to 40°C. The hollow fiber membrane passing through the coagulation bath was washed with water at 40°C in a washing bath and then dried to obtain a hollow fiber membrane. In this case, the thickness of the hollow fiber membrane was 150 μm.

[0140] Comparative Example 1

[0141] A casting solution was prepared by mixing 20 wt% polystyrene (PS), 6 wt% polyvinylpyrrolidone (PVP), and 1 wt% antioxidant (Irganox 1010) with 73 wt% solvent N-methylpyrrolidone (NMP). A core solution was prepared by mixing NMP and ethanol at a volume ratio of 75:25. The casting solution was discharged through the outer tube of a dual-nozzle spray nozzle, and the core solution was discharged through the inner tube, thereby immersing the spinning material in a coagulation bath containing a coagulation solution. The spinning material contacted the coagulation solution in the coagulation bath to form a hollow fiber membrane. In this case, a 1:1 mixture of water and PEG was used as the coagulation solution, and the temperature was adjusted to 40°C. The hollow fiber membrane passing through the coagulation bath was washed with water at 40°C in a washing bath and then dried to obtain a hollow fiber membrane. In this case, the thickness of the hollow fiber membrane was 150 μm.

[0142] Comparative Example 2

[0143] A casting solution was prepared by mixing 20 wt% polystyrene (PS), 6 wt% polyvinylpyrrolidone (PVP), and 74 wt% solvent N-methylpyrrolidone (NMP). A core solution was prepared by mixing NMP and ethanol at a volume ratio of 6:4. The casting solution was discharged through the outer tube of a dual-nozzle spray nozzle, and the core solution was discharged through the inner tube, thereby immersing the spinning material in a coagulation bath containing a coagulation solution. The spinning material contacted the coagulation solution in the coagulation bath to form a hollow fiber membrane. In this case, a 1:1 mixture of water and PEG was used as the coagulation solution, and the temperature was adjusted to 40°C. The hollow fiber membrane passing through the coagulation bath was washed with water at 40°C in a washing bath and then dried to obtain a hollow fiber membrane. In this case, the thickness of the hollow fiber membrane was 150 μm.

[0144] Evaluation Example 1

[0145] A humidifier module comprising the hollow fiber membranes prepared in Example 1 and Comparative Example 1 was manufactured and installed on a fuel cell system. The amount of antioxidant remaining in the hollow fiber membrane was measured before the humidifier module was driven and after 1000 hours of driving the humidifier module, and is shown in Table 1 below.

[0146] Methods for determining the amount of antioxidants

[0147] use 1 The amount of antioxidant was measured by ¹H-NMR. The resulting hollow fiber membrane was dissolved in DMSO-D6 for determination, and the total amount was calculated by comparing the integral ratio of the proton peak of the main polymer to the proton peak of the antioxidant.

[0148] [Table 1]

[0149]

[0150] As shown in Table 1, in the membrane humidifier containing the hollow fiber membrane of Example 1, it was confirmed that the amount of antioxidant decreased after 1000 hours of fuel cell operation. This indicates that the antioxidant is delivered from the membrane humidifier to the fuel cell stack. In Comparative Example 1, although the casting solution contained antioxidant, it was confirmed that the final manufactured membrane humidifier did not contain antioxidant. This indicates that the core liquid mixing ratio is important in order to retain the antioxidant inside the hollow fiber membrane during membrane formation.

[0151] Evaluation Example 2

[0152] A humidifier module comprising the hollow fiber membranes prepared in Example 1 and Comparative Example 2 was manufactured and installed on a fuel cell system. The permeability of the polymer electrolyte membrane in the stack was measured using the following method before and after 1000 hours of operation of the humidifier module, and the results are shown in Table 2.

[0153] [Method for determining the gas permeability of polymer electrolyte membranes]

[0154] The polymer electrolyte membrane was cut into a circle with a diameter of 50 mm, mounted on a measuring fixture, and hydrogen gas was applied at a pressure of 0.5 bar. The amount of hydrogen passing through the polymer electrolyte membrane was measured, thereby determining the gas permeability of the polymer electrolyte membrane.

[0155] [Table 2]

[0156]

[0157] As shown in Table 2, it was confirmed that the polymer electrolyte membrane in the fuel cell stack that received antioxidants from the membrane humidifier exhibited suppressed chemical degradation caused by oxidizing substances, and therefore the permeability was reduced by about 30% compared with Comparative Example 2 without antioxidant supplementation.

[0158] It has been confirmed that when the hollow fiber membrane prepared according to Example 1 is applied to a membrane humidifier and used in a fuel cell system, the membrane humidifier serves to supply antioxidants to the fuel cell stack, thereby preventing chemical degradation of the polymer electrolyte membrane in the fuel cell stack.

Claims

1. A hollow fiber membrane for a fuel cell humidifier, comprising: polymer; and Antioxidants The antioxidant is disposed on the inner surface and / or the outer surface.

2. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The polymer forms a network structure, and The antioxidants are dispersed and present within the network structure.

3. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The antioxidant is configured to flow out from the hollow fiber membrane in an amount of more than 1 μg over 1000 hours when the fuel cell is driven.

4. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The polymers include polyvinylidene fluoride (PVDF) polymers, polysulfone polymers, sulfonated polysulfone, cellulose acetate, cellulose triacetate, polymethyl methacrylate, Nafion, polystyrene (PS) polymers, polytetrafluoroethylene (PTFE) polymers, perfluorosulfonic acid (PFSA) polymers, polyphenylene sulfone (PPSU) polymers, polyether sulfone (PES) polymers, polyacrylonitrile (PAN) polymers, polyetherimide (PEI) polymers, polyimide (PI) polymers, or any combination thereof.

5. The hollow fiber membrane for a fuel cell humidifier according to claim 4, wherein, The polymers include polysulfone polymers, sulfonated polysulfones, polystyrene (PS) polymers, polyethersulfone (PES) polymers, or any combination thereof.

6. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The polymer content is 90 parts by weight or more and less than 100 parts by weight relative to 100 parts by weight of the hollow fiber membrane.

7. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The antioxidants include phenolic antioxidants, amine antioxidants, metal antioxidants, organometallic antioxidants, sulfur antioxidants, phosphorus antioxidants, or combinations thereof.

8. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The antioxidant content is from 0.1 parts by weight to 5 parts by weight relative to 100 parts by weight of the polymer.

9. The hollow fiber membrane for a fuel cell humidifier according to claim 1, wherein, The hollow fiber membrane also contains polyvinylpyrrolidone.

10. A method for preparing a hollow fiber membrane for a fuel cell humidifier, the method comprising: Preparation of a casting solution containing polymers and antioxidants for forming hollow fiber membranes; The casting solution is discharged into the coagulation bath through a tubular spinning device; and The spinning solution discharged into the coagulation bath is coagulated in the coagulation bath, then wound and dried to obtain the hollow fiber membrane. The antioxidant is disposed on the inner and / or outer surface of the hollow fiber membrane.

11. The method for preparing a hollow fiber membrane for a fuel cell humidifier according to claim 10, wherein, The step of preparing the casting solution includes mixing the polymer and the antioxidant in an organic solvent to obtain the casting solution. The antioxidant is mixed in an amount of 0.01 to 5 parts by weight relative to 100 parts by weight of the polymer.

12. The method for preparing a hollow fiber membrane for a fuel cell humidifier according to claim 10, wherein, The tubular spinning device contains a core solution of a second solvent and a third solvent in a volume ratio of 3:7 to 7:3 in its hollow section. The second solvent includes water, methanol, ethanol, isopropanol, acetone, hexane, pentane, benzene, toluene, carbon tetrachloride, o-dichlorobenzene, polyethylene glycol, or combinations thereof, and The third solvent includes N-methyl-2-pyrrolidone, dimethyl sulfoxide, dimethylacetamide, dimethylformamide, methyl ethyl ketone, tetrahydrofuran, tetramethylurea, trimethyl phosphate, or combinations thereof.

13. The method for preparing a hollow fiber membrane for a fuel cell humidifier according to claim 12, wherein, The core fluid also contains antioxidants.

14. A fuel cell humidifier comprising the hollow fiber membrane according to any one of claims 1 to 9.

15. A fuel cell system comprising: A fuel cell stack including a fuel cell, the fuel cell including a polymer electrolyte membrane; and The humidifier of claim 14, wherein the humidifier is in communication with the fuel cell stack, The antioxidant flows out of the humidifier and into the fuel cell stack at a rate of more than 1 μg / 1000 hr.

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