KR101987529B1 - Polymer electrolyte membrane and fuel cell comprising the same - Google Patents

Abstract

The present invention relates to a polymer electrolyte membrane and a fuel cell including the same, wherein the polymer electrolyte membrane is characterized in that a porous support is impregnated with a poly (arylene ether ketone) copolymer having a specific structure.

Description

TECHNICAL FIELD [0001] The present invention relates to a polymer electrolyte membrane and a fuel cell including the polymer electrolyte membrane.

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a polymer electrolyte membrane used in manufacturing fuel cells and a fuel cell including the same.

A fuel cell is an energy conversion device that converts chemical energy into electrical energy by electrochemical reaction of hydrogen or methanol as fuel and oxygen or air as oxidant. Such a fuel cell includes a membrane-electrode assembly composed of an anode, an oxygen cathode, and an electrolyte membrane.

The electrolyte membrane serves to transfer hydrogen ions generated from the fuel electrode to the oxygen electrode and serves as a diaphragm to prevent the fuel from mixing with oxygen. Such an electrolyte membrane can be classified into a fluorinated PEM electrolyte membrane and a hydrocarbon-based PEM electrolyte membrane depending on the material.

The hydrocarbon-based electrolyte membrane has a lower manufacturing cost than the fluorine-based electrolyte membrane and has an excellent thermal stability. However, in the hydrocarbon-based electrolyte membrane, a hydrophilic ionic group is introduced to have hydrogen ion conductivity at the level of the fluorine-based electrolyte membrane. The introduction of such a hydrophilic ionic group excessively induces swelling phenomenon due to moisture to increase the durability of the electrolyte membrane, There is a problem that stability is lowered.

In order to solve the above problems, there has been proposed a technique of introducing a cross-linking structure by covalent bond into a starting polymer and using the same to produce an electrolyte membrane, thereby lowering the water solubility of the electrolyte membrane. However, the raw polymer having a crosslinked structure has a high molecular weight, which makes it difficult to produce an electrolyte membrane using the polymer, and has limitations in improving the physical properties of the electrolyte membrane.

Korean Patent Laid-Open Publication No. 2015-0071889

In order to solve the above problems, it is an object of the present invention to provide a polymer electrolyte membrane having excellent physical properties such as hydrogen ion conductivity, tensile strength, elongation, and methanol permeability.

Another object of the present invention is to provide a fuel cell including the above polymer electrolyte membrane.

In order to accomplish the above object, the present invention provides a porous support comprising: a porous support; And a poly (arylene ether ketone) copolymer impregnated in the porous support and represented by any one of Chemical Formulas 1 to 3 below.

[Chemical Formula 1]

(2)

(3)

(In the formula 1,

Ar ₁ is a C ₆ to C ₃₀ arylene group substituted with a sulfone group,

Ar ₂ is a C ₆ to C ₃₀ aryl group substituted with a sulfone group,

R ₁ is selected from the group consisting of hydrogen and C ₁ to C ₁₈ alkyl groups, a plurality of R _{1 s} are the same as or different from each other,

m is an integer of 1 to 5, n is an integer of 4 to 30,

A is an integer of 5 to 120,

In the above Formulas 2 and 3,

Ar ₃ is a C ₆ to C ₃₀ aryl group substituted with a sulfone group,

R ₂ and R ₃ are each independently selected from the group consisting of hydrogen and a C ₁ to C ₁₈ alkyl group, a plurality of R _{2 s} are the same or different from each other, a plurality of R _{3 s} are the same as or different from each other,

x is an integer of 3 to 6, y is an integer of 4 to 9, and z is an integer of 3 to 10.)

The present invention also provides a fuel cell comprising: a fuel electrode; Oxygen pole; And a polymer electrolyte membrane.

The polymer electrolyte membrane of the present invention is excellent in physical properties such as hydrogen ion conductivity, tensile strength, elongation, and methanol permeability because it includes a porous support and a poly (arylene ether ketone) copolymer into which a hydrophilic moiety and a sulfone group are introduced. Therefore, when the polymer electrolyte membrane of the present invention is applied to a fuel cell, a fuel cell having excellent operation performance can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an electron microscope image of the polymer electrolyte membrane prepared in Example 1 of the present invention. FIG.

Hereinafter, the present invention will be described.

The present invention relates to a polymer electrolyte membrane comprising a copolymer designed to optimize physical properties of an electrolyte membrane, that is, a poly (arylene ether ketone) copolymer having a high molecular weight and having a hydrophilic moiety and a large amount of sulfonic acid groups, and a fuel Battery, which will be described in detail as follows.

1. Polymer Electrolyte membrane

The polymer electrolyte membrane of the present invention includes a porous support and a poly (arylene ether ketone) copolymer.

The porous support included in the polymer electrolyte membrane of the present invention plays a role of preventing the poly (arylene ether ketone) copolymer from flowing out to the outside. The material usable as such a porous support is not particularly limited, but it is preferable to use a fluororesin such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVDF) in view of the tensile strength and elongation of the polymer electrolyte membrane desirable. Also, the content of the porous support is not particularly limited. However, considering the dimensional stability, tensile strength, hydrogen ion conductivity, etc. of the polymer electrolyte membrane, it is preferably 35 to 50% by weight based on 100% by weight of the polymer electrolyte membrane.

The poly (arylene ether ketone) copolymer contained in the polymer electrolyte membrane of the present invention is impregnated into the porous support and serves as a pathway for hydrogen ions. These poly (arylene ether ketone) copolymers are selected from the group consisting of copolymers represented by the following general formulas (1) to (3).

[Chemical Formula 1]

(2)

(3)

In Formula 1,

Ar ₁ is a C ₆ to C ₃₀ arylene group substituted with a sulfone group, Ar ₂ is a C ₆ to C ₃₀ aryl group substituted with a sulfone group, R ₁ is a group consisting of hydrogen and a C ₁ to C ₁₈ alkyl group is selected and, the plurality of R ₁ are the same or different, m is an integer from 1 to 5, n is an integer from 4 to 30, a is an integer from 5 to 120,

In the above Formulas 2 and 3,

Ar ₃ is a sulfone group-substituted C ₆ to C ₃₀ aryl group, R ₂ and R ₃ are each independently selected from the group consisting of hydrogen and C ₁ to C ₁₈ alkyl groups, and a plurality of R _{2 s} are the same or different, and a plurality of R ₃ are the same or different, x is an integer from 3 to 6, y is an integer of 4 to 9, z is an integer of 3-10.)

The poly (arylene ether ketone) copolymer represented by the above general formulas (1) to (3) is characterized by having a large amount of sulfonic acid group due to its high molecular weight and having a hydrophilic moiety introduced therein. The poly (arylene ether ketone) copolymer having such characteristics is excellent in electrochemical characteristics and has a high molecular weight, so that leakage after impregnation with the porous support is minimized. Therefore, when the polymer electrolyte membrane including the poly (arylene ether ketone) copolymer is applied to a fuel cell, the movement path of the hydrogen ions is shortened and the movement path of the secured hydrogen ions is maintained for a long time. And this excellent fuel cell can be provided.

The poly (arylene ether ketone) copolymer represented by the formula (1) is a biphenylene in which Ar ₁ is substituted with a sulfone group, Ar ₂ is naphthyl substituted by a sulfone group, and R ₁ Methyl is preferable. Specifically, the poly (arylene ether ketone) copolymer represented by the formula (1) may be represented by the following formula (5).

[Chemical Formula 5]

In the above formula (5), definitions of m, n and A are the same as those described above.

The poly (arylene ether ketone) copolymer represented by the formula (1) is preferably a crosslinked polymer of an oligomer represented by the following formula (4) impregnated in a porous support in consideration of impregnation efficiency. That is, the poly (arylene ether ketone) copolymer represented by Formula 1 is impregnated with a porous support by impregnating a porous support with an oligomer represented by Formula 4, followed by crosslinking reaction. The poly (arylene ether ketone) copolymer represented by the above formula (1) is a copolymer having a crosslinked structure and has a large molecular weight. Therefore, impregnation of the poly (arylene ether ketone)

[Chemical Formula 4]

In Formula 4, R ₁ , m, n and A are as defined above.

The poly (arylene ether ketone) copolymer represented by the above formulas 2 and 3 is preferably naphthyl in which R ₂ and R ₃ are methyl and Ar ₃ is substituted with sulfone group, considering the synthesis process and characteristics thereof. Specifically, the poly (arylene ether ketone) copolymer represented by Formula 2 may be represented by Formula 6, and the poly (arylene ether ketone) copolymer represented by Formula 3 may be represented by Formula 7 below.

[Chemical Formula 6]

(7)

The weight average molecular weight of the poly (arylene ether ketone) copolymer of the present invention is not particularly limited, but it is preferably 50,000 to 200,000 in view of the physical properties of the polymer electrolyte membrane. In particular, the poly (arylene ether ketone) copolymer represented by the formula (1) preferably has a weight average molecular weight of 70,000 to 120,000.

The degree of sulfonation of the poly (arylene ether ketone) copolymer of the present invention is not particularly limited, but it is preferably 55 to 75% in consideration of hydrogen ion conductivity and the like.

The content of the poly (arylene ether ketone) copolymer of the present invention is not particularly limited. However, considering the tensile strength, hydrogen ion conductivity, etc. of the polymer electrolyte membrane, the content of the poly (arylene ether ketone) %.

The polymer electrolyte membrane of the present invention preferably has a ratio (a: b) of the thickness (b) of the prepared polymer electrolyte membrane to the thickness (a) of the porous support used in the range of 1: 1.2 to 1.4 .

The method for producing the polymer electrolyte membrane of the present invention is not particularly limited, but may be prepared by controlling the production process according to the impregnated poly (arylene ether ketone) copolymer.

Specifically, the polymer electrolyte membrane comprising the poly (arylene ether ketone) copolymer represented by Formula 1 may be prepared by introducing a porous support, which has been washed and dried, into an oligomer- The oligomer represented by the general formula (4) is impregnated into the porous support, and then the crosslinking reaction is carried out.

The polymer electrolyte membrane comprising the poly (arylene ether ketone) copolymer represented by Chemical Formulas 2 and 3 may be prepared by subjecting a porous support obtained by washing and drying to a poly (arylene ether ketone) copolymer represented by Chemical Formula 2 or 3, The copolymer may be added to the dissolved impregnation solution to impregnate the copolymer.

The main solvent contained in the impregnation solution is not particularly limited as long as it is an organic solvent known in the art. However, considering the solubility of the polymer or copolymer, dimethylsulfoxide (DMSO), dimethylacetamide (DMAc) It is preferably pyrrolidone (NMP). The auxiliary solvent contained in the impregnation solution is not particularly limited, but is preferably an alcohol-based solvent.

Since the polymer electrolyte membrane of the present invention includes any one of the poly (arylene ether ketone) copolymers represented by the above general formulas (1) to (3), high tensile strength and elongation can be exhibited. Specifically, the polymer electrolyte membrane of the present invention may have a tensile strength of 30 to 50 MPa and an elongation of 50 to 110%.

3. Fuel cell

The present invention provides a fuel cell including the above-described polymer electrolyte membrane. Specifically, the fuel cell of the present invention includes a fuel electrode (anode); An oxygen electrode; And a membrane / electrode assembly including the above-described polymer electrolyte membrane.

The fuel electrode is a place where the oxidation reaction of the fuel occurs, and the components and the manufacturing method are not particularly limited as long as they are well known in the art. The oxygen electrode is a place where a reduction reaction of oxygen occurs, and the component and the production method are not particularly limited as long as they are well known in the art. The fuel electrode and the oxygen electrode may include a gas diffusion layer and a catalyst layer promoting an oxidation reaction of the fuel or a reduction reaction of oxygen.

The polymer electrolyte membrane is located between the fuel electrode and the oxygen electrode.

Such a fuel cell of the present invention is excellent in operation performance because it includes a polymer electrolyte membrane having excellent physical properties such as tensile strength, elongation, hydrogen ion conductivity and methanol permeability.

Hereinafter, the present invention will be described in detail with reference to examples. However, the following examples are illustrative of the present invention, and the present invention is not limited by the following examples.

[ Example  1] A polymer comprising a copolymer of the formula (1) Electrolyte membrane  Produce

0.01 mol of 4,4'-bis (4-hydroxyphenyl) -valeric acid, 0.03 mol of potassium carbonate, 100 mL of DMSO, and 50 mL of tulurene were placed in a 250 mL flask equipped with a Dean-Stark trap, a nitrogen inlet and a mechanical stirrer. , And the mixture was stirred at room temperature for about 2 hours and then heated to 145 DEG C for reaction for 4 hours. 0.01 mol of sulfonated 4,4'-difluorobenzophenone was mixed with 20 mL of DMSO and stirred at room temperature for 4 hours to prepare a solution. The solution was then added to the stirred flask while removing water and toluene by reflux distillation The reaction temperature was raised to 165 ° C and the reaction proceeded.

After the reaction, the temperature was lowered to room temperature and the synthesized oligomer solution was slowly dropped in 1000 mL of IPA to obtain a precipitate. Only the precipitate was obtained through a glass filter, washed several times with 2000 mL of IPA to wash the precipitate, and then dried in an oven at 80 ° C for one day to prepare an intermediate.

0.01 mol of each of the prepared intermediate, N-hydroxysuccinimide (NHS) and N, N'-dicyclohexylcarbodiimide (DCC) was added to 30 ml, 5 ml and 5 ml DMF, After completely dissolving by stirring, the mixture was reacted at 40 DEG C for 12 hours. The precipitate was removed from the reaction-completed solution and precipitated with IPA to obtain the product, which was then dried in an oven at 80 ° C for one day.

PAEK having side branches thus obtained was dissolved in a mixed solution of dimethylacetamide and ethanol (volume ratio = 1: 1) in an amount of 10% by weight, and then 70 mol% of 3-amino-1,5-naphthalene disulfonic acid salt, And 15 mol% of 2'-benzidine disulfonic acid (BDSA) was added to dissolve. To this solution, polyvinylidene fluoride (PVDF) was added in an amount of 50 parts by weight based on 100 parts by weight of the PAEK, and the mixture was homogeneously mixed. Subsequently, the obtained mixture was cast on a glass plate, dried in an oven at 105 ° C for 72 hours, impregnated with distilled water to remove unreacted materials, and further dried in a 100 ° C vacuum oven for 24 hours to prepare a polymer electrolyte membrane.

[ Example  2] The polymer comprising the copolymer of formula (2) Electrolyte membrane  Produce

0.01 mol of bisphenol A, 0.02 mol of potassium carbonate, 60 mL of DMSO and 60 mL of toluene were added to a 250 mL four-necked round-bottomed flask with a Dean Stark trap, a nitrogen inlet and a mechanical stirrer, After stirring for a time, the temperature was raised to 145 캜 and allowed to react for 4 hours. 0.01 mol of sulfonated 4,4'-difluorobenzophenone was mixed with 60 mL of DMSO and stirred at room temperature for 4 hours to prepare a solution. The solution was added to the stirred flask while removing water and toluene by reflux distillation The reaction was carried out after the temperature was raised to 165 ° C.

After the reaction, the temperature was lowered to room temperature and the synthesized oligomer solution was slowly dropped in 1000 mL of IPA to obtain a precipitate. Only the precipitate was obtained through a glass filter, washed several times with 2000 Ml of IPA for washing of the precipitate, and dried in an oven at 80 ° C for one day to prepare a copolymer.

The prepared copolymer was dissolved in a mixed solution of dimethylacetamide and ethanol (volume ratio = 1: 1) in an amount of 10% by weight, and then decafluorobiphenyl (DFBP) was dissolved in the molar ratio. To this solution, polyvinylidene fluoride (PVDF) was added in an amount of 50 parts by weight based on 100 parts by weight of the copolymer and uniformly mixed. Subsequently, the obtained mixture was cast on a glass plate, dried in an oven at 105 ° C for 72 hours, impregnated with distilled water to remove unreacted materials, and further dried in a 100 ° C vacuum oven for 24 hours to prepare a polymer electrolyte membrane.

[ Example  3] A polymer comprising a copolymer of the formula (3) Electrolyte membrane  Produce

0.01 mol of 4,4'-bis (4-hydroxyphenyl) -valeric acid, 0.03 mol of potassium carbonate, 100 mL of DMSO, and 50 mL of tulurene were placed in a 250 mL flask equipped with a Dean-Stark trap, a nitrogen inlet and a mechanical stirrer. , And the mixture was stirred at room temperature for about 2 hours and then heated to 145 DEG C for reaction for 4 hours. 0.01 mol of sulfonated 4,4'-difluorobenzophenone was mixed with 20 mL of DMSO and stirred at room temperature for 4 hours to prepare a solution. The solution was then added to the stirred flask while removing water and toluene by reflux distillation The reaction temperature was raised to 165 ° C and the reaction proceeded.

After the reaction, the temperature was lowered to room temperature and the synthesized oligomer solution was slowly dropped in 1000 mL of IPA to obtain a precipitate. Only the precipitate was obtained through a glass filter, washed several times with 2000 mL of IPA to wash the precipitate, and then dried in an oven at 80 ° C for one day to prepare an intermediate.

0.01 mol of each of the prepared intermediate, N-hydroxysuccinimide (NHS) and N, N'-dicyclohexylcarbodiimide (DCC) was added to 30 ml, 5 ml and 5 ml DMF, After completely dissolving by stirring, the mixture was reacted at 40 DEG C for 12 hours. The precipitate was removed from the reaction-completed solution and precipitated with IPA to give the product. 0.01 mol of PAEK having NHS in the side branch thus obtained, 0.012 mol of 3-amino-1,5-naphthalene diallyl sulfonate, 0.02 mol of K ₂ CO ₃ , 50 mL of DMAc and 15 mL of cyclohexane were placed in a four-necked flask, At reflux distillation for 12 hours. When the reaction was completed, the temperature was lowered to room temperature, and the solution was precipitated with IPA to obtain a precipitate. The resulting precipitate was dried in a 60 ° C vacuum oven for 24 hours to prepare a copolymer having sulfonate groups in side branches.

The prepared copolymer was dissolved in a mixed solution of dimethylacetamide and ethanol (volume ratio = 1: 1) in an amount of 10% by weight, and then decafluorobiphenyl (DFBP) was dissolved in the molar ratio. To this solution, polyvinylidene fluoride (PVDF) was added in an amount of 50 parts by weight based on 100 parts by weight of the copolymer and uniformly mixed. Subsequently, the obtained mixture was cast on a glass plate, dried in an oven at 105 ° C for 72 hours, impregnated with distilled water to remove unreacted materials, and further dried in a 100 ° C vacuum oven for 24 hours to prepare a polymer electrolyte membrane.

[ Comparative Example  One]

Nafion 117 from DuPont was applied.

[ Experimental Example  One]

The surface and cross section of the polymer electrolyte membrane prepared in Example 1 were confirmed by an electron microscope and the results are shown in FIG.

Referring to FIG. 1, it can be confirmed that the copolymer is well impregnated into polyvinylidene fluoride (PVDF) used as a porous support.

[ Experimental Example  2]

The physical properties of the polymer electrolyte membranes of Examples 1 to 3 and Comparative Example 1 were evaluated by the following methods, and the results are shown in Table 1 below.

1. Tensile Strength: A sample having a size of 10 mm × 40 mm in width was prepared from each of the prepared polymer electrolyte membranes, and tensile strength was measured using a tensile strength meter (UTM-model 5565, Lloyd) Respectively.

2. Ion exchange capacity: Ion exchange capacity (IEC) was measured by the inverse titration method. Specifically, 0.1 g of each of the produced polymer electrolyte membranes was added to 20 mL of 0.05 N NaOH solution, and the mixture was stirred at room temperature for 3 days. At this time, when the sulfonic acid group of the copolymer reacted with NaOH and the concentration of OH in the solution became low, the solution was titrated with a 0.05 N HCl solution and a pH meter.

3. The water content: How to measure the weight change of the absorption of the prepared polymer electrolyte membrane, respectively before water (W _dry) and after absorption (W _wet) was calculated by Equation 1. Specifically, the polymer electrolyte membrane prepared in the 90 oven was dried to measure the dry weight, and the polymer electrolyte membrane was immersed in distilled water for 24 hours to measure the weight of the polymer electrolyte membrane Respectively.

[Equation 1]

4. Ion Conductivity: Bekktech cell (trade name, Bekktech, USA) was used for ion conductivity measurement. Hydrogen was used as the measurement gas source and the gas was flowed at 300 cc / min. The resistance values were measured under the conditions of 100% humidity and ion conductivity was calculated using the following equation (2). Where L is the distance between the anode and cathode fixed at 0.425 cm in the Bekktech cell, R is the resistance of the polymer electrolyte membrane, and W and T are the width and thickness of the polymer electrolyte membrane, respectively.

&Quot; (2) "

The tensile strength
(MPa) Ion exchange capacity
(meq g ^-1 ) Moisture content
(%) Ion conductivity
(S · cm ^-1 ) Example 1 27.71 1.43 22.97 0.075 Example 2 32.85 1.42 21.89 0.071 Example 3 28.32 1.36 22.35 0.065 Comparative Example 1 20.76 0.91 20.48 0.06

Referring to Table 1, it can be seen that the polymer electrolyte membrane of the present invention has excellent tensile strength, ion exchange capacity, moisture content, and ionic conductivity.

Claims (10)

A porous support; And
A poly (arylene ether ketone) copolymer impregnated in the porous support and represented by the following Chemical Formula 1,
Wherein the poly (arylene ether ketone) copolymer represented by the formula (1) is a crosslinked polymer of an oligomer represented by the following formula (4).
[Chemical Formula 1]

[Chemical Formula 4]

In Formula 1,
Ar ₁ is a C ₆ to C ₃₀ arylene group substituted with a sulfone group,
Ar ₂ is a C ₆ to C ₃₀ aryl group substituted with a sulfone group,
R ₁ is selected from the group consisting of hydrogen and C ₁ to C ₁₈ alkyl groups, a plurality of R _{1 s} are the same as or different from each other,
m is an integer of 1 to 5, n is an integer of 4 to 30,
A is an integer of 5 to 120; The method according to claim 1,
35 to 50% by weight of the porous support; And
And 50 to 65% by weight of the poly (arylene ether ketone) copolymer. The method according to claim 1,
The poly (arylene ether ketone) copolymer has a weight average molecular weight of 50,000 to 200,000. The method according to claim 1,
Wherein the poly (arylene ether ketone) copolymer has a degree of sulfonation of 55 to 75%. The method according to claim 1,
Wherein the Ar ₁ is biphenylene substituted with a sulfone group, and Ar ₂ is substituted with a sulfone group. delete The method according to claim 1,
Wherein R < ₁ > is methyl. delete The method according to claim 1,
A polymer electrolyte membrane having a tensile strength of 30 to 50 MPa and an elongation of 50 to 110%. Fuel electrode;
Oxygen pole; And
A fuel cell comprising the polymer electrolyte membrane according to any one of claims 1 to 5, 7 and 9.

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