KR20180076949A - Polymer electrolyte membrane for fuel cell and manufacturing method thereof - Google Patents

Abstract

The present invention relates to a polymer electrolyte membrane for a fuel cell and a manufacturing method thereof. The polymer electrolyte membrane comprises a porous support sheet, an ion conductive polymer, and first and second ion conductive polymer membranes. The porous support sheet is composed of polymer nanofiber including a non-charge polymer and an ion conductive polymer. The ion conductive polymer is impregnated inside the porous support sheet. The first and second ion conductive polymer membranes are formed on an upper part and a lower part of the porous support sheet. The present invention relates to the polymer electrolyte membrane for a fuel cell, and the manufacturing method thereof capable of highly improving durability and a charging/discharging feature of a cell by including excellent mechanical properties and ion conductivity.

Description

TECHNICAL FIELD [0001] The present invention relates to a polymer electrolyte membrane for a fuel cell,

The present invention relates to a polymer electrolyte membrane for a fuel cell and a method of manufacturing the same. More particularly, the present invention relates to a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer, A polymer electrolyte membrane comprising a polymer and first and second ion conductive polymer membranes formed on upper and lower portions of the porous support sheet, has excellent mechanical properties and ionic conductivity, and thus has excellent durability and charge / Film and a method of manufacturing the same.

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

BACKGROUND ART Fuel cells include a polymer electrolyte fuel cell (PEMFC), a direct methanol fuel cell (DMFC), a phosphoric acid fuel cell (PAFC), an alkaline fuel cell (AFC), a molten carbonate fuel cell (MCFC) And a battery (SOFC).

Among them, polymer electrolyte fuel cells have been actively studied because they have high energy density and high output. Such a polymer electrolyte fuel cell differs from other fuel cells in that a solid polymer electrolyte membrane is used instead of a liquid electrolyte as an electrolyte.

If the polymer electrolyte membrane of the fuel cell is not sufficiently supplied with water, the hydrogen ion conductivity will drop sharply, which will shorten the performance in the short term and accelerate deterioration of the electrolyte membrane partly or entirely in the long term to promote the lifetime of the fuel cell.

Korean Unexamined Patent Publication No. 2009-0039180 discloses an ion conductive composite membrane impregnated with an ion conductive polymer resin in a porous mat made of a fluoropolymer resin fiber.

However, when the fluoropolymer resin is used as the polymer electrolyte membrane, the sulfonic acid group having the hydrogen ion conduction function is strongly hydrophobic and has a problem of lowering the ion conductivity during the production of the membrane. In addition, impregnation with a hydrophilic ion conductive polymer resin due to strong hydrophobicity There is a problem that the rigidity is degraded because it is not properly performed.

Korean Patent Publication No. 2009-0039180

In order to solve the above problems, an object of the present invention is to apply a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer, wherein the porous support sheet comprises an ion conductive polymer impregnated in the porous support sheet And to provide a polymer electrolyte membrane for fuel cells having excellent mechanical properties and ionic conductivity by producing a polymer electrolyte membrane.

Another object of the present invention is to provide a method of manufacturing a polymer electrolyte membrane for a fuel cell capable of improving the durability and charge / discharge characteristics of a battery by providing first and second ion conductive polymer membranes on the upper and lower portions of the porous support sheet, .

The present invention relates to a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer; An ion conductive polymer impregnated inside the porous support sheet; And first and second ion conductive polymer membranes formed on upper and lower portions of the porous support sheet, respectively.

(A) preparing a polymer mixture solution by mixing a polymer with a nonconductive polymer and an ion conductive polymer in a solvent; (b) electrospinning the polymer mixture solution to form a porous support sheet; And (c) impregnating the porous support sheet with an ion conductive polymer. The present invention also provides a method of manufacturing a polymer electrolyte membrane for a fuel cell.

The polymer electrolyte membrane for a fuel cell according to the present invention comprises a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer and an ion conductive polymer impregnated in the porous support sheet, There is an advantage of conductivity.

Also, since the first and second ion conductive polymer membranes are formed on the upper and lower portions of the porous support sheet, the ion conductivity is very excellent, so that the durability and charge / discharge characteristics of the fuel cell can be improved.

1 is a SEM photograph of a porous support sheet produced in an embodiment of the present invention.

Hereinafter, the present invention will be described in more detail with reference to one embodiment.

The present invention relates to a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer; An ion conductive polymer impregnated inside the porous support sheet; And first and second ion conductive polymer membranes formed on upper and lower portions of the porous support sheet, respectively.

According to a preferred embodiment of the present invention, the non-conductive polymer has excellent strength and can maintain the strength even when the thickness is less than 20 탆. The non-conductive polymer preferably has a tensile strength of 30 MPa or more. The tensile strength is a minimum strength capable of maintaining the structure of the membrane electrode assembly (MEA) for a fuel cell and stacking.

Specifically, the non-conductive polymer may be at least one selected from the group consisting of hydrocarbon-based, fluorine-based, and silicone-based polymers. More specifically, the hydrocarbon-based polymer may be at least one selected from the group consisting of polymethyl methacrylate, polyimide, and polyether ether ketone. The fluorine-based polymer may be at least one selected from the group consisting of polyvinylidene fluoride, chlorotrifluoroethylene, and ethylene tetrafluoroethylene. The silicon-based polymer may be at least one selected from the group consisting of polysilane, polycarbosilane and polysiloxane.

According to a preferred embodiment of the present invention, the ion conductive polymer constituting the polymer nanofibers, the ion conductive polymer impregnated in the porous support sheet, and the first and second ion conductive The polymer membrane may be made of the same ion conductive polymer material.

When the porous support sheet composed of the polymer nanofibers is prepared by mixing the ion conductive polymer with the non-conductive polymer, the porous support sheet itself has excellent ion conductivity and is very useful for transferring hydrogen ions generated from the anode electrode to the cathode electrode There is an advantage.

The ion conductive polymer having ionic conductivity of 0.05 S / cm or more can be used. The ionic conductivity should be maintained at least 0.05 S / cm or more as a factor affecting the fuel cell operation performance, so that the operation performance is not deteriorated. The ion conductive polymer may be at least one selected from the group consisting of perfluorosulfone acid, polyimide, polyethersulfone, polyphenylene sulfide, polyphosphazene, and polyether ketone.

According to a preferred embodiment of the present invention, the polymer nanofibers may be prepared by mixing the non-charged polymer and the ion conductive polymer in a weight ratio of 5: 5 to 7: 3. When the ratio of the non-charged polymer in the mixing ratio is increased, the rigidity of the porous support sheet is increased but the ion conductivity can be reduced. Also, when the ratio of the ion conductive polymer is increased, the ionic conductivity is increased, but the rigidity of the porous support sheet may be lowered. Preferably, the non-conductive polymer and the ion conductive polymer are mixed in a weight ratio of 6: 4.

According to a preferred embodiment of the present invention, the polymer nanofibers have a nano-sized fiber length and thus have a large specific surface area as compared with conventional fibers. When the porous support sheet is formed of the polymer nanofiber having such a large specific surface area, the ion conductivity of the ion conductive polymer can be maintained by increasing the impregnation amount of the ion conductive polymer.

The polymer nanofibers having an average fiber length of 100 to 300 nm can be used. If the average fiber length is less than 100 nm, the strength of the porous support sheet may be lowered. If the average fiber length is more than 300 nm, the porosity of the porous support sheet may be lowered and the impregnation amount of the ion conductive polymer may be lowered.

According to a preferred embodiment of the present invention, the porous support sheet may have an average pore size of 50 to 100 nm and a porosity of 75 to 95%. If the average pore size is less than 50 nm and the porosity is less than 70%, the impregnation amount of the ion conductive polymer is decreased, and the performance of the polymer electrolyte membrane may be deteriorated. When the average pore size is more than 100 nm and the porosity is more than 95%, the impregnation amount of the ion conductive polymer is too much, and the impregnation uniformity may be lowered.

According to a preferred embodiment of the present invention, the ion conductive polymer impregnated in the porous support sheet may be impregnated with 60 to 75 wt% of the total weight of the porous support sheet. If the impregnation amount of the ion conductive polymer is less than 60 wt%, the effect of ionic conductivity is insufficient. If the impregnation amount is more than 75 wt%, the charge transfer resistance due to the increase in thickness may be increased.

According to a preferred embodiment of the present invention, the porous support sheet may have a thickness of 10 to 20 탆. If the thickness of the porous support sheet is less than 10 탆, the strength may be lowered, and if it is more than 20 탆, the charge transfer resistance may increase.

According to a preferred embodiment of the present invention, the first and second ion conductive polymer membranes formed on the upper and lower portions of the porous support sheet may each have a thickness of 3 to 5 탆. If the thickness of each of the first and second ion conductive polymer films is less than 3 mu m, a uniform layer can not be formed, and if more than 5 mu m, the charge transfer resistance can be increased.

According to another aspect of the present invention, there is provided a method of manufacturing a polymer electrolyte membrane for a fuel cell, comprising the steps of: (a) preparing a polymer mixture solution by mixing a polymer with a nonconductive polymer and an ion conductive polymer; (b) electrospinning the polymer mixture solution to form a porous support sheet; And (c) impregnating the porous support sheet with the ion conductive polymer.

According to a preferred embodiment of the present invention, the solvent in step (a) is selected from the group consisting of dimethylacetamide, tetramethyl urea, dimethyl sulfoxide, triethyl phosphate, N- At least one selected from the group consisting of N-methyl-2-pyrrolidone, trimethyl phosphate, tetrahydrofuran (THF) and methyl ethyl ketone .

According to a preferred embodiment of the present invention, in the step (b), electrospinning can produce the polymer mixture solution having fibers having nanosized fiber length. The polymer nanofibers thus prepared can be electrospun to form a web-like porous support sheet.

At this time, the electrospinning may be performed under the condition of a voltage of 10 to 15 kV and a humidity of 30 to 40%. If the voltage during the electrospinning is less than 10 kV, the nanofiber may not be properly formed, and if the voltage is more than 15 kV, the nanofiber may be thinned. If the humidity is above 40%, the nanofibers can clump when dried. Low humidity is favorable for nanofiber manufacturing, but process costs for environmental maintenance increase.

According to a preferred embodiment of the present invention, the step (c) may be carried out by impregnating the porous support sheet with the ion conductive polymer by the following two methods.

First, in the step (c), the porous conductive sheet may be impregnated with the ion conductive polymer at a temperature of 25 to 30 DEG C for 1 to 3 minutes. If the porous support sheet is impregnated with the ion conductive polymer in this manner, the liquid ion conductive polymer can easily penetrate into the porous support sheet, thereby uniformly penetrating the porous support sheet, thereby increasing the internal uniformity.

Second, the step (c) may include: (c-1) forming first and second ion conductive polymer films on both surfaces of the porous support sheet to produce a laminate; And (c-2) hot-pressing the laminate. At this time, the first and second ion conductive polymer membranes may be made of the same ion conductive polymer material.

According to a preferred embodiment of the present invention, in the step (c-2), the hot pressing process may be performed at a temperature of 120 to 160 ° C and a pressure of 0.1 to 5 MPa for 1 to 5 minutes. In this case, if the temperature and pressure conditions are not satisfied during the hot pressing process, there is a problem that the interface between the support and the ion conductive polymer is separated.

When the stacked body having the first and second ion conductive polymer films formed on both sides of the porous support sheet is hot-pressed as described above, the ion conductive polymer is impregnated into the porous support sheet and the surface thickness of the polymer electrolyte membrane is made uniform have.

Therefore, the polymer electrolyte membrane for a fuel cell according to the present invention comprises a porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer, and an ion conductive polymer impregnated in the porous support sheet, And ion conductivity.

Also, since the first and second ion conductive polymer membranes are formed on the upper and lower portions of the porous support sheet, the ion conductivity is very excellent, so that the durability and charge / discharge characteristics of the fuel cell can be improved.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited by the following Examples.

Example

Dimethylacetamide Polyvinylidene fluoride (PVdF) and nafion were mixed in a weight ratio of 6: 4 to 100 ml of solvent to prepare a polymer mixture solution. Then, the polymer mixture solution was electrospun under conditions of a pressure of 13 kV, a humidity RH of 35% and a temperature of 25 ° C to prepare a porous support sheet composed of polymer nanofibers having an average fiber diameter of 100 nm. At this time, the porous support sheet had a porosity of 85%, an average pore size of 70 nm, and a thickness of 15 탆.

The porous support sheet was laminated on one surface of the sheet, and a first ion conductive polymer membrane having a thickness of 8 탆 was laminated by a thermal compression bonding method.

Next, a second ion conductive polymer membrane having a thickness of 15 탆 was laminated on the other surface of the porous support sheet in the same manner as above.

Next, the laminate composed of the first ion conductive polymer membrane, the porous support sheet and the second ion conductive polymer membrane was hot pressed for 3 minutes at a temperature of 140 ° C and a pressure of 1 MPa to prepare a polymer electrolyte membrane. At this time, it was confirmed that the thickness of each of the first and second ion conductive polymer membranes in the prepared polymer electrolyte membrane was 3 μm.

As a result, it was found that the first and second ion conductive polymers were partially impregnated into the interior of the porous support sheet through the hot press process. At this time, it was confirmed that the ion conductive polymer impregnated into the porous support sheet was impregnated with 70 wt% of the whole porous support sheet.

Comparative Example

Commercial Nafion (NRE212, DuPont) was prepared as a polymer electrolyte which is a polymer electrolyte membrane material.

Experimental Example 1

SEM measurement was performed to confirm the nanofiber thickness and pore structure of the porous support sheet prepared in the above examples. The results are shown in Fig.

1 is a SEM photograph of a porous support sheet produced in an embodiment of the present invention. FIG. 1 (a) shows polymer nanofibers showing an average fiber thickness of 100 nm. FIG. 1 (b) shows the surface of the porous support sheet, showing that a uniform pore structure was formed by the nanofibers.

Experimental Example 2

The polymer electrolyte membranes prepared in the above Examples and Comparative Examples were applied to fabricate a fuel cell by a conventional method. The ion conductivity of each fuel cell thus prepared was measured, and the results are shown in Table 1 below.

division Example Comparative Example Ion conductivity (S / cm) 0.116 0.110

According to the results of Table 1, it was confirmed that the ion conductive polymer was uniformly impregnated in the porous support sheet in the case of the above example, and the ion conductivity was improved as compared with the comparative example.

Claims (16)

A porous support sheet composed of a polymer nanofiber including a non-conductive polymer and an ion conductive polymer;
An ion conductive polymer impregnated inside the porous support sheet; And
First and second ion conductive polymer membranes respectively formed on upper and lower portions of the porous support sheet;
A polymer electrolyte membrane for a fuel cell.
The method according to claim 1,
Wherein the non-conductive polymer is at least one selected from the group consisting of hydrocarbon-based, fluorine-based, and silicone-based polymers.
The method according to claim 1,
Wherein the ion conductive polymer constituting the polymer nanofibers, the ion conductive polymer impregnated in the porous support sheet, and the first and second ion conductive polymer membranes are all made of the same ion conductive polymer material. membrane.
The method of claim 3,
Wherein the ion conductive polymer is at least one selected from the group consisting of perfluorosulfonic acid, polyimide, polyethersulfone, polyphenylene sulfide, polyphosphazine, and polyether ketone.
The method according to claim 1,
Wherein the polymer nanofibers are prepared by mixing the non-charged polymer and the ion conductive polymer in a weight ratio of 5: 5 to 7: 3.
The method according to claim 1,
Wherein the polymer nanofibers have an average fiber length of 100 to 300 nm.
The method according to claim 1,
Wherein the porous support sheet has an average pore size of 50 to 100 nm and a porosity of 75 to 95%.
The method according to claim 1,
Wherein the ion conductive polymer impregnated in the porous support sheet is impregnated with 60 to 75% by weight of ion conductive polymer based on the total weight of the porous support sheet.
The method according to claim 1,
Wherein the porous support sheet has a thickness of 10 to 20 占 퐉.
The method according to claim 1,
Wherein the first and second ion conductive polymer membranes formed on the upper and lower portions of the porous support sheet each have a thickness of 3 to 5 占 퐉.
(a) preparing a polymer mixture solution by mixing a polymer and an ion conductive polymer in a solvent;
(b) electrospinning the polymer mixture solution to form a porous support sheet; And
(c) impregnating the porous support sheet with an ion conductive polymer;
Wherein the polymer electrolyte membrane for a fuel cell comprises a polymer electrolyte membrane.
The method according to claim 11,
In step (a), the solvent may be selected from the group consisting of dimethylacetamide, tetramethyl urea, dimethyl sulfoxide, triethyl phosphate, N-methyl-2-pyrrolidone (N- wherein the polymer electrolyte membrane is at least one selected from the group consisting of methyl-2-pyrrolidone, trimethyl phosphate, tetrahydrofuran (THF), and methyl ethyl ketone. Way.
12. The method of claim 11,
Wherein the electrospinning in the step (b) is performed under a condition of a voltage of 10 to 15 kV and a humidity of 30 to 40%.
12. The method of claim 11,
Wherein the step (c) comprises impregnating the porous support sheet with the ion conductive polymer at a temperature of 25 to 30 ° C for 1 to 3 minutes.
12. The method of claim 11,
The step (c)
(c-1) forming first and second ion-conductive polymer membranes on both surfaces of the porous support sheet to produce a laminate; And
(c-2) hot-pressing the laminate;
≪ RTI ID = 0.0 > 1, < / RTI >
16. The method of claim 15,
Wherein the hot pressing process is performed at a temperature of 120 to 160 ° C. and a pressure of 0.1 to 5 MPa for 1 to 5 minutes in the step (c-2).

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