KR102090860B1 - Polymer electrolyte membrane, membrane electrode assembly comprising the same and fuel cell comprising the membrane electrode assembly - Google Patents

Abstract

The present specification relates to a polymer electrolyte membrane, a membrane electrode assembly comprising the same, and a fuel cell comprising the membrane electrode assembly.

Description

A polymer electrolyte membrane, a membrane electrode assembly comprising the same, and a fuel cell comprising the membrane electrode assembly TECHNICAL FIELD

The present specification relates to a polymer electrolyte membrane, a membrane electrode assembly comprising the same, and a fuel cell comprising the membrane electrode assembly.

Recently, as the depletion of existing energy resources such as oil and coal is predicted, interest in energy that can replace them is increasing. As one of these alternative energies, fuel cells are particularly attracting attention due to advantages such as high efficiency, no emission of pollutants such as NOx and SOx, and abundant fuel used.

A fuel cell is a power generation system that converts chemical reaction energy of a fuel and an oxidant into electrical energy, and hydrocarbons such as hydrogen, methanol, and butane are used as fuel, and oxygen is used as an oxidant.

Fuel cells include polymer electrolyte fuel cells (PEMFC), direct methanol fuel cells (DMFC), phosphoric acid fuel cells (PAFC), alkaline fuel cells (AFC), molten carbonate fuel cells (MCFC), and solid oxide fuel And SOFCs.

Republic of Korea Patent Publication No. 2003-0045324 (released on June 11, 2003)

This specification is intended to provide a polymer electrolyte membrane, a membrane electrode assembly comprising the same, and a fuel cell comprising the membrane electrode assembly.

The present specification is a sulfonated hydrocarbon-based polymer; And it provides a polymer electrolyte membrane comprising a sulfonated fluorine-based polymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).

[Formula 1]

[Formula 2]

In Formulas 1 and 2, R is a fluorinated alkylene group having 2 to 4 carbon atoms, X is a monovalent cation group, and m and n are each independently an integer of 1 to 15.

In addition, the present specification is a sulfonated hydrocarbon-based polymer; A sulfonated fluorine-based polymer comprising a repeating unit represented by Chemical Formula 1 and a repeating unit represented by Chemical Formula 2; And it provides a composition for a polymer electrolyte membrane comprising a solvent.

[Formula 1]

[Formula 2]

In Formulas 1 and 2, R is a fluorinated alkylene group having 2 to 4 carbon atoms, X is a monovalent cation group, and m and n are each independently an integer of 1 to 15.

In addition, the present specification is an anode; Cathode; And it provides a membrane electrode assembly comprising the polymer electrolyte membrane provided between the anode and the cathode.

In addition, the present specification provides a fuel cell including the membrane electrode assembly.

In addition, the present specification provides an electrochemical cell including a first electrode, a second electrode, and the polymer electrolyte membrane provided between the first electrode and the second electrode.

In addition, the present specification provides a battery module including the electrochemical cell as a unit cell.

The battery provided with the polymer electrolyte membrane according to the present specification has an advantage of improving performance at low humidity.

The battery provided with the polymer electrolyte membrane according to the present specification has an advantage of improving performance in a high current density region.

1 is a schematic view showing the principle of electricity generation in a fuel cell.
2 is a view schematically showing the structure of a membrane electrode assembly.
3 is a view schematically showing an embodiment of a fuel cell.
4 is a graph comparing current densities under operating conditions of 50% relative humidity in Example 1 and Comparative Example 1-2.

Hereinafter, the present specification will be described in detail.

The present specification is a sulfonated hydrocarbon-based polymer; And it provides a polymer electrolyte membrane comprising a sulfonated fluorine-based polymer.

The equivalent weight (EW) of the polymer electrolyte membrane is not particularly limited, but may be specifically 500 meq / g or more and 1000 meq / g or less. At this time, the equivalent weight refers to a unit molecular weight with respect to 1 mol of sulfonic acid groups (-SO ₃ H).

The sulfonated hydrocarbon-based polymer is not particularly limited as long as it is a hydrocarbon-based polymer having a sulfonic acid group, but sulfonated poly ether ether chitone, sulfonated poly chitone, sulfonated poly (phenylene oxide), sulfonated poly (phenyl) Len sulfide), sulfonated polysulfone, sulfonated polycarbonate, sulfonated polystyrene, sulfonated polyimide, sulfonated polyquinoxaline, sulfonated (phosphonated) polyphosphazene and sulfony Tited polybenzimidazole.

The sulfonated hydrocarbon-based polymer may have a weight average molecular weight of tens of thousands to millions. Specifically, the weight average molecular weight of the sulfonated hydrocarbon-based polymer may be selected from 10,000 to 1 million.

The equivalent of the sulfonated hydrocarbon-based polymer may be 500 meq / g or more and 1000 meq / g or less.

The present specification is a sulfonated hydrocarbon-based polymer; And it provides a polymer electrolyte membrane comprising a sulfonated fluorine-based polymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).

[Formula 1]

[Formula 2]

In Formulas 1 and 2, R is a fluorinated alkylene group having 2 to 4 carbon atoms, X is a monovalent cation group, and m and n are each independently an integer of 1 to 15.

Based on the sum of the weights of the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer, the content of the sulfonated fluorine-based polymer may be 1% by weight or more and 10% by weight or less. In this case, the performance of the fuel cell applied under low-humidity conditions is improved.

Based on the sum of the weight of the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer, the content of the sulfonated fluorine-based polymer may be 3% by weight or more and 10% by weight or less, and 3% by weight or more and 5% by weight or less It is preferred. In this case, the mechanical properties are maintained and the performance of the applied fuel cell is improved.

The equivalent of the sulfonated fluorine-based polymer may be 900 meq / g or less. When producing a polymer electrolyte membrane with a sulfonated fluorine-based polymer having an EW within the range, along with a sulfonated hydrocarbon-based polymer, there is an effect of improving the performance of the fuel cell under low-humidity conditions.

The equivalent of the sulfonated fluorine-based polymer may be 700 meq / g or more and 900 meq / g or less, and specifically 725 meq / g or more and 900 meq / g or less. The equivalent of the sulfonated fluorine-based polymer is preferably 725 meq / g or more and 850 meq / g or less.

The repeating unit represented by Chemical Formula 2 may be represented by any one of Chemical Formulas 3 to 5 below.

[Formula 3]

[Formula 4]

[Formula 5]

In Chemical Formulas 3 to 5, X is a monovalent cation group, and m is an integer from 1 to 15.

In Chemical Formulas 2 to 5, X is not particularly limited as long as it is a monovalent cationic group, but may be H ⁺ , NH ₄ ⁺ , K ⁺ , Li ⁺ or Na ⁺ .

The repeating unit represented by Chemical Formula 2 may be represented by any one of Chemical Formulas 4 to 5, and is preferably represented by Chemical Formula 5. In this case, the performance of the fuel cell applied under low-humidity conditions is improved.

The sulfonated fluorine-based polymer may include a repeating unit represented by Formula 1 and a repeating unit represented by Formula 5, wherein in Formulas 1 and 5, X is a monovalent cationic group, and m and n are respectively. It is an integer of 1-15 independently.

The sulfonated fluorine-based polymer may be composed of only repeating units represented by the following Chemical Formula 1 and repeating units represented by the following Chemical Formula 5.

The polymer electrolyte membrane further includes a porous support, and the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer may be impregnated in the pores of the porous support.

This specification is an anode; Cathode; And it provides a membrane electrode assembly comprising the polymer electrolyte membrane provided between the anode and the cathode.

The membrane electrode assembly may cite the above-described description of the polymer electrolyte membrane.

FIG. 1 schematically shows the principle of electricity generation in a fuel cell, and in a fuel cell, the most basic unit for generating electricity is a membrane electrode assembly (MEA), which is an electrolyte membrane M and this electrolyte membrane M It consists of an anode (A) and a cathode (C) formed on both sides of. Referring to Fig. Showing the electricity generating principle of a fuel cell 1, an anode (A) in the hydrogen or methanol, butane and the oxidation of the fuel (F) of the hydrocarbon and so on up the hydrogen ions (H ⁺⁾ and electron (e ^-), such as Is generated, and hydrogen ions move to the cathode C through the electrolyte membrane M. In the cathode C, hydrogen ions transferred through the electrolyte membrane M react with oxidizing agents such as oxygen (O) and electrons to generate water (W). The reaction causes electron movement to occur in the external circuit.

As shown in FIG. 2, the membrane electrode assembly may include an electrolyte membrane 10 and a cathode 50 and an anode 51 positioned to face each other with the electrolyte membrane 10 interposed therebetween. Specifically, the cathode includes the cathode catalyst layer 20 sequentially provided from the electrolyte membrane 10 and the cathode gas diffusion layer 30, and the anode includes the anode catalyst layer 21 and the anode sequentially provided from the electrolyte membrane 10. A gas diffusion layer 31 may be included.

The anode and the cathode may include an anode catalyst layer and a cathode catalyst layer, respectively.

The anode catalyst layer and the cathode catalyst layer may each include a catalyst and an ionomer.

Each catalyst ink forming the anode catalyst layer and the cathode catalyst layer may independently include a catalyst, an ionomer, and a solvent.

The catalyst is not limited as long as it can serve as a catalyst in a fuel cell, but may include one of platinum, transition metals and platinum-transition metal alloys.

Here, the transition metal is a group 3 to 11 element in the periodic table, and may be, for example, any one of ruthenium, osmium, palladium, molybdenum, and rhodium.

Specifically, the catalyst may be selected from the group consisting of platinum, ruthenium, osmium, platinum-ruthenium alloy, platinum-osmium alloy, platinum-palladium alloy, platinum-molybdenum alloy and platinum-rhodium alloy, but is not limited thereto. Does not.

The catalysts can be used by themselves as well as supported on a carbon-based carrier.

Examples of the carbon-based carrier include graphite (graphite), carbon black, acetylene black, denka black, cachon black, activated carbon, mesoporous carbon, carbon nanotube, carbon nanofiber, carbon nanohorn, carbon nanoring, carbon nanowire, A preferred example may be any one or two or more mixtures selected from the group consisting of fullerene (C60) and super P black.

The ionomer serves to provide a passage for ions generated by reaction between a fuel such as hydrogen or methanol and a catalyst to move to the electrolyte membrane. As the ionomer, a sulfonated polymer such as Nafion ionomer or sulfonated polytrifluorostyrene may be used.

As the solvent included in the catalyst ink, any one or a mixture of two or more selected from the group consisting of water, butanol, isopropanol, methanol, ethanol, n-propanol, n-butyl acetate and ethylene glycol is preferred. Can be used.

The process of introducing the catalyst layer may be performed by a conventional method known in the art, for example, directly coating the catalyst ink on the electrolyte membrane, or forming a catalyst layer on the release substrate, followed by thermal compression on the electrolyte membrane and release. It can be formed by removing the substrate, or coated on a gas diffusion layer to form a catalyst layer. At this time, the coating method of the catalyst ink is not particularly limited, but spray coating, tape casting, screen printing, blade coating, inkjet coating, die coating or spin coating may be used.

The anode gas diffusion layer and the cathode gas diffusion layer are respectively provided on one surface of the catalyst layer, and have a porous structure as a passage for reaction gas and water together with a role as a current conductor. Therefore, the gas diffusion layer may be formed of a conductive substrate.

As the conductive substrate, a conventional material known in the art may be used, but, for example, carbon paper, carbon cloth, or carbon felt may be preferably used, and is limited thereto. Does not work.

The gas diffusion layer may have a thickness of 200 μm or more and 500 μm or less. In this case, there is an advantage in that the reactant gas transfer resistance through the gas diffusion layer is minimized and the optimum condition is contained in the gas diffusion layer.

The present specification provides a fuel cell including the membrane electrode assembly. Specifically, the fuel cell may include two or more membrane electrode assemblies.

The fuel cell comprises: a stack comprising two or more membrane electrode assemblies according to the present specification and a separator provided between the membrane electrode assemblies; A fuel supply unit supplying fuel to the stack; And it provides a fuel cell including an oxidizing agent supply for supplying the oxidizing agent to the stack.

3 schematically shows the structure of a fuel cell, and the fuel cell includes a stack 60, an oxidizing agent supply unit 70, and a fuel supply unit 80.

The stack 60 includes one or more of the above-described membrane electrode assemblies, and when two or more membrane electrode assemblies are included, includes a separator interposed therebetween. The separator serves to prevent the membrane electrode assemblies from being electrically connected and to transfer fuel and oxidant supplied from the outside to the membrane electrode assembly.

The oxidizing agent supply unit 70 serves to supply the oxidizing agent to the stack 60. As the oxidizing agent, oxygen is typically used, and oxygen or air may be injected into the oxidizing agent supply unit 70 to be used.

The fuel supply unit 80 serves to supply fuel to the stack 60, and to a fuel tank 81 for storing fuel and a pump 82 for supplying fuel stored in the fuel tank 81 to the stack 60. Can be configured. As the fuel, gaseous or liquid hydrogen or hydrocarbon fuels may be used. Examples of hydrocarbon fuels include methanol, ethanol, propanol, butanol or natural gas.

The present specification provides an electrochemical cell including a first electrode, a second electrode, and the polymer electrolyte membrane provided between the first electrode and the second electrode.

The first electrode may be a positive electrode or a negative electrode, and the second electrode may be a positive electrode or a negative electrode as opposed to the first electrode. That is, when the first electrode is an anode, the second electrode may be a cathode, and when the first electrode is a cathode, the second electrode may be an anode.

The anode is a cathode that receives and reduces electrons when discharged, and means an anode that oxidizes and emits electrons when charged. The cathode is an anode that is oxidized to discharge electrons when discharged and means a cathode that receives electrons and is reduced when charged.

The electrochemical cell means a cell using a chemical reaction, and if a polymer electrolyte membrane is provided, the type is not particularly limited. For example, the electrochemical cell may be a fuel cell, a metal secondary cell, or a flow cell.

The present specification provides an electrochemical cell module that includes an electrochemical cell as a unit cell.

The electrochemical cell module may be formed by stacking by inserting a bipolar plate between unit cells.

The battery module may be specifically used as a power source for electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, or power storage devices.

The shape of the electrochemical cell is not limited, and may be, for example, coin, flat, cylindrical, horn, button, sheet or stacked.

The present specification is a sulfonated hydrocarbon-based polymer; And it provides a composition for a polymer electrolyte membrane comprising a sulfonated fluorine-based polymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2).

[Formula 1]

[Formula 2]

In Formulas 1 and 2, R is a fluorinated alkylene group having 2 to 4 carbon atoms, X is a monovalent cation group, and m and n are each independently an integer of 1 to 15.

The composition for the polymer electrolyte membrane may cite the above description of the polymer electrolyte membrane.

The composition for a polymer electrolyte membrane may further include a solvent. The type of the solvent is not particularly limited as long as it can dissolve the sulfonated hydrocarbon-based polymer and sulfonated fluorine-based polymer, and conventional materials known in the art can be used.

Based on the total weight of the composition for the polymer electrolyte membrane, the content of the sulfonated hydrocarbon-based polymer may be 4.5% by weight or more and 9.9% by weight or less, and the sulfonated fluorine-based polymer may be 0.05% by weight or more and 1% by weight or less , The solvent may be 90% by weight or more and 95% by weight or less. At this time, based on the sum of the weight of the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer, the content of the sulfonated fluorine-based polymer may be 1% by weight or more and 10% by weight or less.

The polymer electrolyte membrane may be coated, dried and cured to prepare a polymer electrolyte membrane. In this case, the method of applying the composition is not particularly limited, but spray coating, tape casting, screen printing, blade coating, die coating or spin coating may be used.

The composition for a polymer electrolyte membrane may be applied onto a substrate to produce a pure membrane without a support, or a reinforced membrane may be prepared by impregnating the pores of the support with a polymer electrolyte membrane composition.

Hereinafter, the present specification will be described in more detail through examples. However, the following examples are only intended to illustrate the present specification and are not intended to limit the present specification.

[Example]

[Example 1]

Based on the total weight of the solution, 4.75% by weight of hydrocarbon-based sulfonated multi-block polymer (EW: 535, weight average molecular weight: 950,000) and sulfonated fluorine-based polymer, 0.25% by weight of 3M polymer (EW: 825, product name: E -22122) was added to 95% by weight of dimethyl sulfoxide (DMSO) solvent to prepare a solution. At this time, the weight ratio of the hydrocarbon-based sulfonated multi-block polymer and sulfonated fluorine-based polymer was 95: 5.

Using the prepared solution, cast a polymer film on a substrate using a doctor blade on a horizontal plate of an applicator in a clean bench, hold it at 50 ° C for 2 hours or more (soft baking), put it in an oven set at 100 ° C and put it in a day. During drying, a blend composite membrane was prepared.

[Comparative Example 1]

A polymer electrolyte membrane was prepared in the same manner as in Example 1, except that a solution was prepared without a sulfonated fluorine-based polymer.

[Comparative Example 2]

A polymer electrolyte membrane was prepared in the same manner as in Example 1, except that 0.25% by weight of nafion (EW: 1100, product name: D2021) was used as the sulfonated fluorine-based polymer.

[Experimental Example 1]

The current density for Example 1 and Comparative Example 1-2 was measured by scanning 0 to 1500 mA / cm ² in a Constant Current mode using a PEMFC TEST Station, and operating conditions of 50% relative humidity based on 70 ° C. It was measured at. The results are shown in FIG. 4.

Through FIG. 4, it was confirmed through experiments that in Example 1, the performance at 50% RH was improved over the existing hydrocarbon-based electrolyte membranes (Comparative Examples 1 and 2).

Claims (13)

Sulfonated hydrocarbon-based polymers; And
A sulfonated fluorine-based polymer comprising a repeating unit represented by the following formula (1) and a repeating unit represented by the following formula (2),
Based on the sum of the weight of the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer, the content of the sulfonated fluorine-based polymer is 1% by weight or more and 10% by weight or less,
The polymer electrolyte membrane having a sulfonated fluorine-based polymer equivalent of 900 meq / g or less:
[Formula 1]

[Formula 2]

In Chemical Formulas 1 and 2,
R is an fluorinated alkylene group having 2 to 4 carbon atoms,
X is a monovalent cationic group,
m and n are each independently an integer of 1 to 15. delete delete The method according to claim 1, wherein the repeating unit represented by Formula 2 is a polymer electrolyte membrane represented by any one of the following Formulas 3 to 5:
[Formula 3]

[Formula 4]

[Formula 5]

In Chemical Formulas 3 to 5, X is a monovalent cation group, and m is an integer from 1 to 15. The method according to claim 1, The polymer electrolyte membrane further comprises a porous support,
The sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer are polymer electrolyte membranes that are impregnated in the pores of the porous support. Sulfonated hydrocarbon-based polymers; A sulfonated fluorine-based polymer comprising a repeating unit represented by Chemical Formula 1 and a repeating unit represented by Chemical Formula 2; And a solvent,
Based on the sum of the weight of the sulfonated hydrocarbon-based polymer and the sulfonated fluorine-based polymer, the content of the sulfonated fluorine-based polymer is 1% by weight or more and 10% by weight or less,
The sulfonated fluorine-based polymer has an equivalent of 900 meq / g or less for a polymer electrolyte membrane composition:
[Formula 1]

[Formula 2]

In Chemical Formulas 1 and 2,
R is an fluorinated alkylene group having 2 to 4 carbon atoms,
X is a monovalent cationic group,
m and n are each independently an integer of 1 to 15. delete delete The method according to claim 6, wherein the repeating unit represented by Formula 2 is a composition for a polymer electrolyte membrane represented by any one of the following Formulas 3 to 5:
[Formula 3]

[Formula 4]

[Formula 5]

In Chemical Formulas 3 to 5, X is a monovalent cation group, and m is an integer from 1 to 15. Anode; Cathode; And a polymer electrolyte membrane according to any one of claims 1, 4 and 5 provided between the anode and the cathode. A fuel cell comprising the membrane electrode assembly of claim 10. An electrochemical cell comprising a first electrode, a second electrode, and a polymer electrolyte membrane according to any one of claims 1, 4, and 5 provided between the first electrode and the second electrode. A battery module comprising the electrochemical cell of claim 12 as a unit cell.

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