KR20080013533A - Method of preparing polymer membrane for fuel cell - Google Patents

Abstract

A method for producing a polymer electrolyte membrane for a fuel cell is provided to accomplish uniform dispersion of inorganic additives in a polymer electrolyte membrane, thereby preventing methanol crossover and improving the quality of a fuel cell. A method for producing a polymer electrolyte membrane for a fuel cell comprises: a step(S1) of providing a composition for forming a polymer electrolyte membrane comprising a cation exchange resin, inorganic additives and an organic solvent; a step(S2) of evaporating the organic solvent in the composition to provide a highly concentrated composition for forming a polymer electrolyte membrane; a step(S3) of applying the highly concentrated composition onto a substrate to form a polymer electrolyte layer; and a step(S4) of separating the polymer electrolyte layer from the substrate to provide a polymer electrolyte membrane.

Description

Manufacturing method of polymer electrolyte membrane for fuel cell {METHOD OF PREPARING POLYMER MEMBRANE FOR FUEL CELL}

1 is a process diagram schematically showing a method for producing a polymer electrolyte membrane for a fuel cell according to an embodiment of the present invention.

2 schematically illustrates a membrane-electrode assembly for a fuel cell according to another embodiment of the present invention.

3 is a view schematically showing the structure of a fuel cell system according to another embodiment of the present invention.

[Industrial use]

The present invention relates to a method for producing a polymer electrolyte membrane for a fuel cell, and more particularly, it is possible to evenly disperse the inorganic additives in the polymer electrolyte membrane to prevent crossover of fuel through the polymer electrolyte membrane, thereby improving the performance of the fuel cell The present invention relates to a method for producing a polymer electrolyte membrane for a fuel cell.

[Prior art]

A fuel cell is a power generation system that directly converts the chemical reaction energy of hydrogen and oxygen contained in hydrocarbon-based materials such as methanol, ethanol and natural gas into electrical energy.

This fuel cell is a clean energy source that can replace fossil energy, and has the advantage of generating a wide range of outputs by stacking unit cells, and having an energy density of 4-10 times that of a small lithium battery. It is attracting attention as a compact and mobile portable power source.

Representative examples of the fuel cell include a polymer electrolyte fuel cell (PEMFC) and a direct oxidation fuel cell (Direct Oxidation Fuel Cell). When methanol is used as the fuel in the direct oxidation fuel cell, it is called a direct methanol fuel cell (DMFC).

The polymer electrolyte fuel cell has an advantage of having a high energy density and a high output, but requires attention to handling hydrogen gas and reforms fuel for reforming methane, methanol, natural gas, etc. to produce hydrogen as fuel gas. There is a problem that requires additional equipment such as a device.

On the other hand, the direct oxidation fuel cell has a lower energy density than the polymer electrolyte fuel cell, but it is easy to handle fuel and has a low operating temperature, so that it can be operated at room temperature, in particular, it does not require a fuel reformer.

In such a fuel cell system, the stack that substantially generates electricity is comprised of a number of unit cells consisting of a membrane-electrode assembly (MEA) and a separator (also called a bipolar plate). It has a stacked structure of several tens. The membrane-electrode assembly is called an anode electrode (also called a “fuel electrode” or an “oxidation electrode”) and a cathode electrode (also called “air electrode” or “reduction electrode”) with a polymer electrolyte membrane containing a hydrogen ion conductive polymer therebetween. ) Is located.

The principle of generating electricity in a fuel cell is that fuel is supplied to an anode electrode, which is a fuel electrode, adsorbed to a catalyst of the anode electrode, and the fuel is oxidized to generate hydrogen ions and electrons. Reaching the cathode electrode, hydrogen ions pass through the polymer electrolyte membrane and are delivered to the cathode electrode. An oxidant is supplied to the cathode, and the oxidant, hydrogen ions, and electrons react on the catalyst of the cathode to generate electricity while producing water.

It is an object of the present invention to provide a method for producing a polymer electrolyte membrane for a fuel cell which can prevent crossover of fuel through the polymer electrolyte membrane and can improve the performance of the resulting fuel cell.

Another object of the present invention is to provide a fuel cell membrane-electrode assembly comprising a polymer electrolyte membrane prepared by the above method.

 Still another object of the present invention is to provide a fuel cell system including a polymer electrolyte membrane prepared by the above method.

In order to achieve the above object, the present invention is to prepare a composition for forming a polymer electrolyte membrane comprising a cation exchange resin, an inorganic additive and an organic solvent, and then by evaporating the organic solvent in the prepared composition for forming a polymer electrolyte membrane of high concentration Preparing a polymer electrolyte membrane-forming composition, applying the high concentration polymer electrolyte membrane-forming composition to a substrate to form a polymer electrolyte layer, and separating the polymer electrolyte layer from the substrate to produce a polymer electrolyte membrane. A method for producing a polymer electrolyte membrane for batteries is provided.

The present invention also provides a fuel cell membrane-electrode assembly comprising a polymer electrolyte membrane for a fuel cell prepared by the above method.

The present invention also provides a system for a fuel cell comprising the polymer electrolyte membrane produced by the above production method.

Hereinafter, the present invention will be described in more detail.

The polymer electrolyte membrane of a fuel cell serves as an insulator that electrically separates the anode electrode and the cathode electrode, or acts as a medium for transferring hydrogen ions from the anode electrode to the cathode electrode during cell operation, and separates the oxidant or fuel supplied to the membrane-electrode assembly. Play a role at the same time.

However, there is a problem in that the fuel supplied to the anode electrode moves to the cathode electrode side through the polymer electrolyte membrane during operation of the fuel cell, and as a result, the battery characteristics of the fuel cell are deteriorated.

In order to prevent such fuel crossover, a method of preparing a polymer electrolyte membrane by adding a plate-like inorganic additive is used. The polymer electrolyte membrane thus prepared has a delamination of the inorganic additives of the layered structure into the nano phase due to the penetration of the cation exchange resin chain, which makes the delivery path long when the fuel passes through the polymer electrolyte membrane. In other words, it serves as a fuel shutoff.

However, when using an inorganic additive, there is a problem that an excess of an organic solvent must be used in order to insert the cation exchange resin into the plate-shaped inorganic additive. In addition, solvent casting is generally used to evaporate the excess organic solvent used in the filmmaking process. In the casting process, non-uniform dispersion such as weighting or agglomeration of inorganic additives is likely to occur. There exists a problem that the battery characteristic of this is reduced.

In contrast, in the present invention, the inorganic additive in the polymer electrolyte membrane can be uniformly dispersed by using the organic solvent contained in the composition at a high concentration before the coating of the composition for forming the polymer electrolyte membrane including the inorganic additive. In addition, the prepared polymer electrolyte membrane can prevent the crossover of fuel through the polymer electrolyte membrane, and as a result can improve the performance of the fuel cell.

1 is a process diagram briefly showing a method of manufacturing a membrane-electrode assembly according to an embodiment of the present invention.

Referring to Figure 1, the method for producing a polymer electrolyte membrane according to an embodiment of the present invention to prepare a composition for forming a polymer electrolyte membrane including a cation exchange resin, an inorganic additive and an organic solvent (S1), Evaporating an organic solvent in the polymer electrolyte membrane-forming composition to prepare a composition for forming a polymer electrolyte membrane in a high concentration (S2), and applying a composition for forming the polymer electrolyte membrane in a high concentration to form a polymer electrolyte layer (S3) And separating the polymer electrolyte layer from the substrate to prepare a polymer electrolyte membrane (S4).

More specifically, first, a composition for forming a polymer electrolyte membrane including a cation exchange resin, an inorganic additive, and an organic solvent is prepared (S1).

The polymer electrolyte membrane-forming composition is preferably prepared by dissolving a cation exchange resin in an organic solvent and then mixing an inorganic additive. In this way, the cation exchange resin chain more easily penetrates between the layers of the inorganic additive so that the layers of the inorganic additive are peeled off into a nano-sized plate.

The cation exchange resin serves to transfer hydrogen ions in the polymer electrolyte membrane, and any cation polymer resin having hydrogen ion conductivity may be used. Representative examples thereof include a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, phosphonic acid groups and derivatives thereof in the side chain.

Specific examples of the polymer resin include fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone A hydrogen ion conductive polymer selected from the group consisting of a polymer, a polyether-etherketone-based polymer, a polyphenylquinoxaline-based polymer, a copolymer thereof, and a mixture thereof may be used, and preferably poly (perfluorosulfonic acid) , Poly (perfluorocarboxylic acid), copolymer of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid group, defluorinated sulfide polyether ketone, aryl ketone, poly (2,2'-m-phenylene ) -5,5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole), copolymers thereof and these Into a mixture of Hydrogen ion conductive polymers selected from the group consisting of can be used.

The organic solvent is N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl acetamide (DMA), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone, methylethyl Ketone (MEK), tetramethylurea, trimethylphosphate, butyrolactone, isophorone, carbitol acetate, methylisobutyl ketone, N-butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethyl acetoacetate, Any one selected from the group consisting of glycol ethers, propylene carbonates, ethylene carbonates, dimethyl carbonates, diethyl carbonates, and mixtures thereof can be used.

The cation exchange resin is preferably prepared by dissolving 1 to 10 parts by weight with respect to 100 parts by weight of an organic solvent. In the case where the cation exchange resin is used in an amount less than 1 part by weight, the cation exchange resin is easily inserted between the inorganic additive layers, but the drying process is long and the viscosity decreases, making the polymer electrolyte membrane difficult to form. It is not preferable because the additive intercalation process becomes long.

The dissolution step is carried out by stirring at 80 to 150 ° C, more preferably at 100 to 120 ° C. In the above temperature range, the cation exchange resin may be sufficiently dissolved, thereby increasing the penetration effect into the inorganic additive when mixing the inorganic additive.

The inorganic additive increases the mechanical strength of the polymer electrolyte membrane and serves to reduce fuel crossover.

Examples of the inorganic additives include silica (fumed silica), and trade names include Aerosil, Cab-O-sil, etc., alumina, mica, and zeolite (trade names SAPO-5, XSM-5, AIPO- 5, VPI-5, MCM-41, etc.), barium titanate, ceramic, inorganic silicate, zirconium hydrogen phosphate, α-Zr (O _a1 PCH _a2 OH) _a (O _b1 PC _b2 H _b4 SO _b5 H) _b · nH ₂ O (where, a1, a2, a, b1 , b2, b4, b5 and b are the same or independently represent an integer of 0 to 14 to each other, n is an integer of 0 to 50), ν-Zr ( PO _a1 ) (H _a2 PO _a3 ) _a (HO _b1 PC _b2 H _b3 SO _b4 H) _b nH ₂ O (where a1, a2, a3, a, b1, b2, b3, b4 and b are the same or Independently of each other, an integer from 0 to 14, n is an integer from 0 to 50), Zr (O _a1 PC _a2 H _a3 ) _a Y _b (where a1, a2, a3, a and b are the same or independently of each other) an integer of from 0 to _{14), Zr (O a1 PCH} a2 OH) a Y b · nH 2 O ( where, a1, a2, a and b are same or Are independently from 0 to 14, an integer to each other, n is an integer of 0 to 50), α-Zr (O a1 PC a2 H a3 SO a4 H) a · nH 2 O ( where, a1, a2, a3, a4 and a is the same or independently of each other is an integer from 0 to 14, n is an integer from 0 to 50), α-Zr (O _a1 POH) H ₂ O (where a1 is an integer from 0 to 14), (P ₂ O ₅ ) _a (ZrO ₂ ) _b (where a and b are the same or independently of each other an integer from 0 to 14) glass, P ₂ O ₅ -ZrO ₂ -SiO ₂ Preference is given to using those selected from the group consisting of glass, and mixtures thereof, more preferably inorganic silicates.

The inorganic silicates include pyrophylite-talc, montmorillonite (MMT), fluorohectorite, kaolinite, vermiculite having a plated layered structure. Vermiculite, illite, mica, or brittle mica are preferred. This is because such inorganic silicates are dispersed in the cation exchange resin in the nano phase, and polymer chains can be easily intercalated on the dispersed inorganic silicate plate to easily delamination.

In addition, the inorganic additive, in particular, the inorganic silicate is preferably used by treating with an organic agent. In the case of treatment with the organic agent, a low molecular weight organic agent is inserted between the plate-shaped inorganic silicate layer structure that is difficult to peel and disperse in the polymer resin due to the strong van der Waals attraction force, so that the polymer resin penetrates easily. It becomes preferable because it becomes easy to peel and disperse | distribute.

As the organic agent, an alkylamine having 1 to 20 carbon atoms, an alkylene diamine having 1 to 20 carbon atoms, a quaternary ammonium salt having 1 to 20 carbon atoms, aminohexane, or a nitrogen-containing heterocyclic compound may be used. Specific examples of the alkylamine include methylamine hydrochloride, propyl amine, butyl amine, octyl amine, decyl amine, dodecyl amine, hexadecyl amine, octadecyl amine, or N-methyl octadecyl amine. . Examples of the alkylene diamine include 1,6-hexamethylene diamine, 1,12-dodecane diamine, and the like. The quaternary ammonium salts include dimethyl quaternary ammonium, benzyl quaternary ammonium, 2-ethylhexyl quaternary ammonium, bis-2-hydroxyethyl quaternary ammonium, methyl quaternary ammonium, tetramethylammonium chloride and octadecyl trimethyl bromide. Ammonium, dodecyltrimethyl ammonium bromide, dioctadecyl dimethyl ammonium bromide, bis (2-hydroxyethyl) methyl octadecyl ammonium chloride, and the like can be used. As the aminohexane, 6-aminohexane, 12-aminohexane, or the like can be used. As the nitrogen-containing heterocyclic compound, 1-hexadecylpyridium chloride or the like can be used.

As described above, the inorganic additive, in particular the inorganic silicate, may be used by treating with an organic agent, but the inorganic silicate which has already been organicized may be directly used. Examples of the organic silicate treated as such are Southern trade names Cloisite6A, Cloisite10A, Cloisite15A, Cloisite20A, Cloisite25A, Cloisite30B and the like, and it is preferable to use Cloisite10A.

The said inorganic additive may use an inorganic additive as it is, or may disperse | distribute in an organic solvent, and may prepare and use an inorganic additive liquid. In the present specification, the inorganic additive liquid means that the inorganic additive liquid is not limited to the state as long as the inorganic additive such as suspension state and dispersion state of the inorganic additive and the organic solvent is added to the liquid organic solvent.

When the inorganic additive is used in the liquid state, the inorganic additive liquid is prepared by adding the inorganic additive to the organic solvent. In this case, 1-propanol, 2-propanol or a mixture thereof may be used as the organic solvent.

The inorganic additive is preferably added in an amount of 0.5 to 10 parts by weight, more preferably 1 to 5 parts by weight, based on 100 parts by weight of the cation exchange resin. When the amount of the inorganic additive is less than 0.5 parts by weight, it is not preferable because the degree of dispersion is small and the degree of permeation of hydrocarbon fuel is increased. When the amount of the inorganic additive is more than 10 parts by weight, the amount of the inorganic additive is dispersed in the cation exchange resin in the prepared polymer electrolyte membrane. It is not preferable because there is a problem that the plate-like inorganic additive is not peeled off and the mechanical strength is lowered.

Thereafter, the prepared polymer electrolyte membrane-forming composition may be uniformly mixed by mechanical mixing or ultrasonic mixing.

By evaporating the organic solvent in the prepared polymer electrolyte membrane-forming composition to prepare a high concentration polymer electrolyte membrane-forming composition (S2).

The evaporation step of the organic solvent may be carried out by heat treatment or may be carried out under vacuum. It is preferable to carry out under vacuum.

The evaporation treatment of the organic solvent is preferably carried out so that the composition after the evaporation treatment has a solute content of 25 to 45% by weight, more preferably 30 to 40% by weight relative to the total weight of the composition. If the content of the solute is lower than 25% by weight, the viscosity is lowered and the flowability is increased, which is not preferable because of difficulty in the coating process during application for forming the polymer electrolyte layer. The application process at the time of application for the formation of the high molecular electrolyte layer is not easy and is not preferable. Accordingly, during the evaporation treatment, it is preferable that the vacuum conditions are appropriately adjusted to the vacuum pressure and the temperature so as to include the solute within the above content range.

After evaporating the organic solvent contained in the polymer electrolyte membrane composition by the evaporation process as described above, the concentration of the solution is evaporated to 30 to 40% by the solute mass ratio to prepare a high concentration of the polymer electrolyte membrane composition.

Next, the high concentration polymer electrolyte membrane-forming composition is applied to one surface of a substrate and dried to form a polymer electrolyte layer (S3).

As the substrate, a release film or a glass substrate may be used, and it is more preferable to use a release film which can easily separate the formed polymer electrolyte membrane without tearing the pattern.

Examples of the release film include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoroalkyl vinyl ether copolymer (PFA), and ethylene / tetrafluoro Fluorine resin films such as ethylene (tethylene / tetrafluoroethylene (ETFE)), polyvinylidene fluoride, or polyimide (Kapton ^® , manufactured by DuPont), polyethylene, polypropylene, polyethylene Non-fluorine polymer films such as terephthalate (polyethylene terephthalate) and polyester (Mylar ^® , manufactured by DuPont) can be used.

The thickness of the release film is preferably 50 to 100 μm, and when the thickness of the release film is less than 50 μm, it is easy to tear during peeling of the polymer electrolyte membrane, and thus it is difficult to control the tension. not.

In addition, the release film may have a pattern. Accordingly, when the polymer electrolyte membrane having a pattern is to be manufactured, the pattern may be formed simultaneously with the preparation of the electrolyte membrane without the need for undergoing an additional pattern forming process for the prepared polymer electrolyte membrane. The pattern formed on the release film may be formed in an appropriate shape according to the pattern to be formed on the polymer electrolyte membrane, and the pattern formation method on the release film may be formed using a conventional pattern formation method.

According to the viscosity of the composition, the coating process of the polymer electrolyte membrane-forming composition onto the substrate may be screen printing, spray coating, coating with a doctor blade, gravure coating, dip coating, silk screen, painting, slots. The die may be implemented by a method selected from the group consisting of a slot method, and a combination thereof, but is not limited thereto. More preferably, the doctor blade method which can apply | coat a polymer electrolyte membrane to uniform thickness can be used.

Thereafter, the coated polymer electrolyte membrane-forming composition is dried to form a polymer electrolyte layer.

Subsequently, the polymer electrolyte layer may be separated from the substrate to prepare a polymer electrolyte membrane (S4).

The polymer electrolyte membrane prepared by the above-described manufacturing method has a plate-shaped inorganic additive evenly dispersed in the cation exchange resin, which significantly increases the mechanical properties of the polymer electrolyte membrane, and is delivered when liquid or gaseous fuel passes through the polymer electrolyte membrane. By lengthening the path, fuel permeation can be significantly reduced.

The polymer electrolyte membrane prepared by the manufacturing method of the present invention may be used in a polymer electrolyte fuel cell (PEMFC), a direct oxidation fuel cell (PEFCC), or the like. In particular, it has an excellent fuel permeation blocking effect can be used more effectively in a direct oxidized fuel cell that crossover of fuel is a problem, it can be used most effectively in a direct methanol fuel cell (DMFC).

The polymer electrolyte membrane prepared as described above may be positioned between the cathode electrode and the anode electrode to form a membrane-electrode assembly.

2 is a schematic cross-sectional view of a membrane-electrode assembly for a fuel cell of the present invention.

Referring to FIG. 2, the membrane-electrode assembly 112 according to an embodiment of the present invention includes the polymer electrolyte membrane 10 and the fuel cell electrodes 20 and 20 disposed on both surfaces of the polymer electrolyte membrane 10, respectively. Include '). The electrode includes electrode substrates 40 and 40 'and catalyst layers 30 and 30' formed on the surface of the electrode substrate.

In the membrane-electrode assembly 112, the electrode 20 disposed on one surface of the polymer electrolyte membrane 10 is called an anode electrode (or a cathode electrode), and the electrode 20 ′ disposed on the other surface is called a cathode electrode ( Or anode electrode). The anode electrode 20 generates an oxidation reaction that generates hydrogen ions and electrons from the fuel delivered to the catalyst layer 30 through the electrode material 40, and the polymer electrolyte membrane 10 is generated at the anode electrode 20. The hydrogen ions are moved to the cathode electrode 20 ', and the cathode electrode 20' is transferred to the catalyst layer 30 'through the hydrogen ions and the electrode base 40' supplied through the polymer electrolyte membrane 10. It causes a reduction reaction to produce water from the oxidant.

 The electrode substrates 40 and 40 'play a role of supporting the electrode and diffuse the fuel and the oxidant to the catalyst layer so that the fuel and the oxidant can easily access the catalyst layer.

As the electrode substrates 40 and 40 ', conductive substrates are used, and representative examples thereof include carbon paper, carbon cloth, carbon felt, or metal cloth (porous material composed of metal cloth in fiber state). It means that the metal film is formed on the surface of the film or the cloth formed of polymer fibers) may be used, but is not limited thereto.

The electrode substrates 40 and 40 'are preferably water-repellent treated with a fluorine-based resin because it prevents the reactant diffusion efficiency from being lowered by water generated when the fuel cell is driven. Examples of the fluorine-based resin include polytetrafluoroethylene, polyvinylidene fluoride, polyhexafluoropropylene, polyperfluoroalkyl vinyl ether, polyperfluorosulfonyl fluoride alkoxy vinyl ether, and fluorinated ethylene propylene ( Fluorinated ethylene propylene), polychlorotrifluoroethylene or copolymers thereof can be used.

In addition, a microporous layer (not shown) may be formed on the electrode substrates 40 and 40 'to enhance the diffusion effect of the reactants in the electrode substrate.

The microporous layer is generally a conductive powder having a small particle diameter, for example, carbon powder, carbon black, acetylene black, activated carbon, carbon fiber, fullerene, carbon nanotube, carbon nanowire, carbon nano horn (carbon nano) -horn or carbon nano ring.

The microporous layer is prepared by coating a composition comprising a conductive powder, a binder resin and a solvent on the electrode substrate. As the binder resin, polytetrafluoroethylene, polyvinylidene fluoride, polyvinyl alcohol, cellulose acetate, and the like may be preferably used. The solvent may be ethanol, isopropyl alcohol, n-propyl alcohol, butyl alcohol, or the like. Alcohol, water, dimethylacetamide, dimethylsulfoxide, N-methylpyrrolidone and the like can be preferably used. The coating process may be screen printing, spray coating, or coating using a doctor blade according to the viscosity of the composition, but is not limited thereto.

The catalyst layers 30 and 30 'catalyze the associated reactions (oxidation of fuel and reduction of oxidant) and include a catalyst.

As the catalyst, any one that can be used as a catalyst by participating in the reaction of the fuel cell may be used, and as a representative example, a platinum-based catalyst may be used. The platinum-based catalyst may be platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy or platinum-M alloy (M is Ga, Ti, V, Cr, Mn, Fe, Co, Ni, At least one catalyst selected from the group consisting of Cu, Zn, Sn, Mo, W, and Rh). As described above, the anode electrode and the cathode electrode may use the same material, but in order to prevent the catalyst poisoning caused by CO generated during the anode electrode reaction in the direct oxidation fuel cell, a platinum-ruthenium alloy catalyst is used as the anode. It is more preferable as an electrode catalyst. Specific examples include Pt, Pt / Ru, Pt / W, Pt / Ni, Pt / Sn, Pt / Mo, Pt / Pd, Pt / Fe, Pt / Cr, Pt / Co, Pt / Ru / W, Pt / Ru One or more selected from the group consisting of / Mo, Pt / Ru / V, Pt / Fe / Co, Pt / Ru / Rh / Ni, and Pt / Ru / Sn / W can be used.

In addition, such a catalyst may be used as the catalyst itself (black), or may be used on a carrier. As the carrier, carbon-based materials such as graphite, denka black, ketjen black, acetylene black, carbon nanotube, carbon nanofiber, carbon nanowire, carbon nanoball, or activated carbon may be used, and alumina, silica, zirconia, Or inorganic fine particles such as titania may be used, but carbon-based materials are generally used.

The catalyst layers 30 and 30 'may further include a binder resin to improve adhesion between the catalyst layer and the polymer electrolyte membrane 10 and transfer hydrogen ions.

It is preferable to use a polymer resin having hydrogen ion conductivity as the binder resin, more preferably a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. Any polymer resin which has can be used.

Representative examples of the polymer resin include fluorine polymer, benzimidazole polymer, polyimide polymer, polyetherimide polymer, polyphenylene sulfide polymer, polysulfone polymer, polyether sulfone polymer, polyether ketone At least one selected from the group polymer, the polyether-ether ketone polymer, or the polyphenylquinoxaline polymer, and more preferably poly (perfluorosulfonic acid) (generally sold as Nafion), poly (Perfluorocarboxylic acid), copolymers of tetrafluoroethylene and fluorovinyl ether containing sulfonic acid groups, defluorinated sulfide polyether ketones, aryl ketones, poly (2,2'-m-phenylene)- 5,5'-bibenzimidazole (poly (2,2 '-(m-phenylene) -5,5'-bibenzimidazole), poly (2,5-benzimidazole), or copolymers thereof One or more Can be.

It is also possible to substitute H with Na, K, Li, Cs or tetrabutylammonium in the cation exchanger of such a hydrogen ion conductive polymer. In the cation exchanger of the hydrogen-ion conductive polymer, NaOH is substituted when H is replaced with Na, and tetrabutylammonium hydroxide is substituted when replacing with tetrabutylammonium, and K, Li or Cs may be substituted with an appropriate compound. It can be substituted. Since this substitution method is well known in the art, detailed description thereof will be omitted.

The binder resin may be used in the form of a single substance or a mixture, and may also be optionally used with a nonconductive compound for the purpose of further improving adhesion to the polymer electrolyte membrane. It is preferable to adjust the usage-amount so that it may be suitable for a purpose of use.

Examples of the non-conductive compound include polytetrafluoroethylene (PTFE), tetrafluoroethylene-hexafluoropropylene copolymer (FEP), tetrafluoroethylene-perfluoro alkylvinyl ether copolymer (PFA), ethylene / tetrafluoro Ethylene / tetrafluoroethylene (ETFE), ethylenechlorotrifluoro-ethylene copolymer (ECTFE), polyvinylidene fluoride, copolymer of polyvinylidene fluoride-hexafluoropropylene (PVdF-HFP), dode At least one selected from the group consisting of silbenzenesulfonic acid and sorbitol is more preferred.

The polymer electrolyte membrane 10 is positioned between the anode or cathode electrodes 20 and 20 'having the above structure.

The polymer electrolyte membrane 10 functions as an ion exchange that transfers hydrogen ions generated in the catalyst layer of the anode electrode to the catalyst layer of the cathode electrode, and is the same as described above.

The present invention also provides a fuel cell system comprising the membrane-electrode assembly.

The fuel cell system includes at least one electricity generating unit including the membrane-electrode assembly and the separator, and includes a fuel supply unit supplying fuel to the electricity generating unit and an oxidant supply unit supplying an oxidant to the electricity generating unit.

The electricity generating unit includes a membrane-electrode assembly, a separator (also called a bipolar plate), and serves to generate electricity through an oxidation reaction of a fuel and a reduction reaction of an oxidant.

The fuel supply unit serves to supply fuel to the electricity generation unit, and the oxidant supply unit serves to supply an oxidant such as oxygen or air to the electricity generation unit. Fuels in the present invention include hydrogen or hydrocarbon fuels in gas or liquid state. Representative examples of the hydrocarbon fuel include methanol, ethanol, propanol, butanol or natural gas.

A schematic structure of the fuel cell system of the present invention is shown in FIG. 3, which will be described in more detail with reference to the following. Although the structure shown in FIG. 3 shows a system for supplying fuel and oxidant to an electric generator using a pump, the fuel cell system of the present invention is not limited to such a structure, and does not use a pump, but uses a fuel diffusion method. Of course, it can also be used in the battery system structure.

 The fuel cell system 100 of the present invention includes at least one electricity generation unit 115 for generating electrical energy through an oxidation reaction of a fuel and a reduction reaction of an oxidant, a fuel supply unit 120 for supplying the fuel, And an oxidant supply unit 130 for supplying an oxidant to the electricity generating unit 115.

In addition, the fuel supply unit 120 for supplying the fuel may include a fuel tank 122 storing fuel and a fuel pump 124 connected to the fuel tank 122. The fuel pump 124 serves to discharge the fuel stored in the fuel tank 122 by a predetermined pumping force.

The oxidant supply unit 130 supplying the oxidant to the electricity generating unit 115 includes at least one oxidant pump 132 that sucks the oxidant with a predetermined pumping force.

The electricity generator 115 includes a membrane-electrode assembly 112 for oxidizing and reducing a fuel and an oxidant, and a separator 114 and 114 'for supplying fuel and an oxidant to both sides of the membrane-electrode assembly. At least one electricity generating unit 115 gathers to form a stack 110.

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

(Example 1)

A commercially available 5 wt% Nafion / H ₂ O / 2-propanol (Solution Technology Inc., EW = 1,100) solution was evaporated under reduced pressure at room temperature to give a solid Nafion resin. The obtained solid Nafion resin was added in an amount of 5 parts by weight based on 100 parts by weight of dimethylacetamide (Aldrich, DMAc) and mechanically stirred at 100 ° C. for 24 hours to prepare a cation exchange resin solution (5% by weight Nafion / DMAc). It was.

Montmorillonite (Southern Clay Product, Cloisite 10A) treated with an organic agent was added to the cation exchange resin solution in an amount of 2 parts by weight based on 100 parts by weight of the cation exchange resin, and then a magnetic stirrer was used at 100 ° C. for 24 hours. Mixing the ultrasonic wave was applied to prepare a composition for forming a polymer electrolyte membrane in which the cation exchange resin chain penetrated between the layers of montmorillonite to remove silicates.

The prepared polymer electrolyte membrane-forming composition was treated under vacuum (vacuum pressure: 15-20 torr, temperature: 65-75 ° C.) for 1 hour to evaporate the solvent to prepare a composition for forming a polymer electrolyte membrane of high concentration. At this time, the content of the solute in the prepared high concentration polymer electrolyte membrane-forming composition was 35% by weight.

The prepared polymer electrolyte membrane-forming composition was applied to a polytetrafluoroethylene film by a doctor blade method and then dried to form a polymer electrolyte layer. The polymer electrolyte layer was separated from the polytetrafluoroethylene film to prepare a polymer electrolyte membrane.

(Comparative Example 1)

A polymer electrolyte membrane was prepared in the same manner as in Example 1, except that the solvent evaporation process was not performed on the polymer electrolyte membrane composition.

Methanol permeability was measured for the polymer electrolyte membranes prepared according to Example 1 and Comparative Example 1.

The methanol permeability is measured by placing a polymer electrolyte membrane sample in the center of a two-zone diffusion cell and circulating 15 wt% methanol / deionized water mixed liquid and deionized water at both ends of the methanol permeated through the electrolyte membrane. The concentration was evaluated by measuring the change in refractive index.

As a result of the measurement, the polymer electrolyte membrane of Example 1 exhibited excellent methanol barrier properties compared to the polymer electrolyte membrane having the same thickness and components of Comparative Example 1. This is because, in the case of Comparative Example 1, the dispersion of the inorganic additives in the polymer electrolyte membrane was not uniform such that the inorganic additives were concentrated and aggregated under the polymer electrolyte membrane.

In addition, a single cell including the polymer electrolyte membrane prepared in Example 1 and Comparative Example 1 was prepared, and the battery characteristics of the prepared single cell were evaluated.

Aqueous dispersion of 10 wt% Nafion (Nafion ^® , manufactured by Dupont) in 3.0 g of Pt black (Hispec ^® 1000, manufactured by Johnson Matthey) and Pt / Ru black (Hispec ^® 6000, manufactured by Johnson Matthey) in 3 ml of isopropyl alcohol 4.5 g was added dropwise, followed by mechanical stirring to prepare a composition for forming a catalyst layer.

The composition for forming the catalyst layer was coated on one surface of carbon paper with an area of 5 × ⁵ cm ² and a thickness of 50 mm to prepare an electrode. Thereafter, two electrodes were manufactured in the same manner, and used as a cathode electrode and an anode electrode, respectively.

A membrane-electrode assembly was prepared by placing the polymer electrolyte membrane prepared in Example 1 or Big Bridge Example 1 between the cathode electrode and the anode electrode and performing heat treatment at 110 ° C.

The prepared membrane-electrode assembly was inserted between two gaskets, and then inserted into two separators having a predetermined gas flow channel and cooling channel, and pressed between copper end plates to prepare a unit cell. .

For the prepared unit cell, 1M methanol solution was used as the anode fuel, and air was injected into the cathode to observe voltage-current characteristics at 70 ° C.

As a result of the measurement, the unit cell including the polymer electrolyte membrane of Example 1 prepared using the composition for forming a polymer electrolyte membrane of high concentration through the evaporation process, to the unit cell comprising the polymer electrolyte membrane of Comparative Example 1 prepared by a conventional method It showed a superior power density.

The voltage-current characteristics of the unit cell including the polymer electrolyte membrane of Example 1 according to the change of temperature and voltage were evaluated. The voltage-current characteristics were measured at varying driving temperatures of 50 ° C., 60 ° C., and 70 ° C. at voltages of 0.45 V and 0.4 V, respectively. The results are shown in Table 1 below.

  Temperature Output density (mW / cm ² ) of the unit cell of Example 1 At 0.45V At 0.4V  50 ℃ 35 50  60 ℃ 47 67  70 ℃ 61 87

As shown in Table 1, the single cell including the polymer electrolyte membrane of Example 1 prepared by the manufacturing method of the present invention showed an excellent power density in a wide temperature range of 50 ℃ to 70 ℃.

In addition, the voltage-current characteristics of the unit cell including the polymer electrolyte membrane of Example 1 according to the fuel concentration change were evaluated. The voltage-current characteristics were measured by varying the concentrations of methanol to 1, 3, 5, and 7M at voltages of 0.45V and 0.4V, respectively, and measuring the respective output densities. The results are shown in Table 2 below.

Methanol concentration (M) Output density (mW / cm ² ) of the unit cell of Example 1 At 0.45V At 0.4V One 61 87 3 38 74

As shown in Table 2, the unit cell including the polymer electrolyte membrane of Example 1 prepared by the manufacturing method of the present invention showed excellent output density even when using a high concentration of methanol.

In the polymer electrolyte membrane prepared by the method for preparing a polymer electrolyte membrane of the present invention, inorganic additives are evenly dispersed in the polymer electrolyte membrane, thereby preventing crossover of fuel through the polymer electrolyte membrane, and thus improving the performance of the fuel cell. have.

Claims (16)

Preparing a polymer electrolyte membrane-forming composition comprising a cation exchange resin, an inorganic additive, and an organic solvent; Preparing a composition for forming a polymer electrolyte membrane having a high concentration by evaporating an organic solvent in the composition for forming a polymer electrolyte membrane; Forming a polymer electrolyte layer by applying the high concentration of the polymer electrolyte membrane-forming composition to a substrate; And A method of manufacturing a polymer electrolyte membrane for a fuel cell comprising separating the polymer electrolyte layer from the substrate to produce a polymer electrolyte membrane. The method of claim 1, Wherein said cation exchange resin is a polymer resin having a cation exchange group selected from the group consisting of sulfonic acid group, carboxylic acid group, phosphoric acid group, phosphonic acid group and derivatives thereof in the side chain. The method of claim 1, The cation exchange resin is 1 to 10 parts by weight based on 100 parts by weight of the organic solvent is a method for producing a polymer electrolyte membrane for a fuel cell. The method of claim 1, The inorganic additive is silica, alumina, zeolite, barium titanate, ceramics, inorganic silicate, zirconium hydrogen _{phosphate, α-Zr (O a1 PCH} a2 OH) a (O b1 PC b2 H b4 SO b5 H) b · nH 2 O (where a1, a2, a, b1, b2, b4, b5 and b are the same or independently of each other an integer from 0 to 14, n is an integer from 0 to 50), ν-Zr (PO _a1 ) ( H _a2 PO _a3 ) _a (HO _b1 PC _b2 H _b3 SO _b4 H) _b nH ₂ O (where a1, a2, a3, a3, a1, b2, b3, b4 and b are the same or independently of each other 0 N is an integer from 0 to 50, n is an integer from 0 to 50, Zr (O _a1 PC _a2 H _a3 ) _a Y _b (where a1, a2, a3, a and b are the same or independently of each other 0 to 14) Zr (O _a1 PCH _a2 OH) _a Y _b nH ₂ O (where a1, a2, a and b are the same or independently of each other an integer from 0 to 14, n is an integer from 0 to 50) , α-Zr (O _a1 PC _a2 H _a3 SO _a4 H) _a nH ₂ O, where a1, a2, a3, a4 and a are the same or Are independently an integer from 0 to 14, n is an integer from 0 to 50), α-Zr (O _a1 POH) H ₂ O (where a1 is an integer from 0 to 14), (P ₂ O ₅ ) _a (ZrO ₂ ) _b (where a and b are the same or independently of each other an integer from 0 to 14) in the group consisting of glass, P ₂ O ₅ -ZrO ₂ -SiO ₂ glass, and mixtures thereof The method for producing a polymer electrolyte membrane for a fuel cell. The method of claim 4, wherein The inorganic silicate is pyrophylite-talc, montmorilonite (MMT), fluorohectorite, kaolinite, vermiculite (plate-like layered structure) vermiculit, illite, mica, mica brittle mica, and a mixture thereof. The method of claim 1, The inorganic additive is a method of producing a polymer electrolyte membrane for a fuel cell that is treated with an organic agent. The method of claim 1, The inorganic additive is 0.5 to 10 parts by weight based on 100 parts by weight of the cation exchange resin manufacturing method of a polymer electrolyte membrane for a fuel cell. The method of claim 1, The organic solvent is N-methyl-2-pyrrolidone (NMP), dimethylformamide (DMF), dimethyl acetamide (DMA), tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), acetone, methyl ethyl ketone (MEK), tetramethylurea, trimethylphosphate, butyrolactone, isophorone, carbitol acetate, methylisobutylketone, N-butyl acetate, cyclohexanone, diacetone alcohol, diisobutyl ketone, ethylacetoacetate, glycol A method for producing a polymer electrolyte membrane for a fuel cell, which is selected from the group consisting of ether, propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, and mixtures thereof. The method of claim 1, The evaporation process of the organic solvent is a method for producing a polymer electrolyte membrane for a fuel cell that is carried out under vacuum. The method of claim 1, The substrate is a method for producing a polymer electrolyte membrane for a fuel cell that is a glass substrate or a release film. The method of claim 10, The release film is a polytetrafluoroethylene, tetrafluoroethylene-hexafluoropropylene copolymer, tetrafluoroethylene- perfluoroalkyl vinyl ether copolymer, ethylene / tetrafluoroethylene, polyvinylidene fluoride, poly A method for producing a polymer electrolyte membrane for a fuel cell, which is selected from the group consisting of mead, polyethylene, polypropylene, polyethylene terephthalate, polyester, copolymers thereof, and mixtures thereof.  The method of claim 10, The release film is a method of producing a polymer electrolyte membrane for a fuel cell having a pattern. The method of claim 1, The coating process of the composition for forming a polymer electrolyte membrane may include screen printing, spray coating, coating using a doctor blade, gravure coating, dip coating, silk screen, painting, slot die, and the like. A method for producing a polymer electrolyte membrane for a fuel cell which is carried out by a method selected from the group consisting of a combination of these. The method of claim 13, The coating step of the composition for forming a polymer electrolyte membrane is a method for producing a polymer electrolyte membrane for a fuel cell that is carried out by a coating method using a doctor blade. A fuel cell membrane-electrode assembly comprising a polymer electrolyte membrane prepared according to any one of claims 1 to 14. A fuel cell system comprising a polymer electrolyte membrane prepared according to any one of claims 1 to 14.

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