KR102525782B1 - Perfluorosulfonic acid ionomer coating composition for fuel cell membrane production and method for manufacturing the same - Google Patents

Abstract

The present invention relates to a perfluorosulfonic acid ionomer coating composition for manufacturing a fuel cell separator and a method for manufacturing the same. The present invention includes a perfluorosulfonic acid ionomer and a fluorine-containing silane compound in a dispersion in which water and alcohol are mixed, so that dispersibility of the perfluorosulfonic acid ionomer coating composition of the present invention can be improved, and the durability of a porous support membrane impregnated with the coating composition can be improved to prevent battery performance from deteriorating even after several operations of a fuel cell.

Description

Perfluorosulfonic acid ionomer coating composition for manufacturing fuel cell separator and method for manufacturing the same {Perfluorosulfonic acid ionomer coating composition for fuel cell membrane production and method for manufacturing the same}

The present invention relates to a perfluorosulfonic acid ionomer coating composition for manufacturing a fuel cell separator and a method for preparing the same.

Polymer electrolyte membrane fuel cells (PEMFCs) are based on a polymer electrolyte membrane (PEM) that selectively transmits only hydrogen ions (protons, H ⁺ ). It is a pollution-free energy conversion system that generates high-efficiency energy using -catalytic reaction.

Representative materials for polymer electrolyte membranes or catalyst binders of polymer electrolyte fuel cells include perfluorinated sulfonic acid ionomers (PFSA) such as DuPont's Nafion.

Perfluorine-based sulfonated ionomer (PFSA) is known to have high hydrogen ion conductivity and excellent chemical stability, but when operated in a dry state, the hydrogen ion conductivity rapidly deteriorates due to spontaneous evaporation of water and chemical/electrical problems under harsh conditions. Shows fatal weakness where chemical decomposition occurs. To solve this problem, a concept introduced is a porous support having excellent chemical durability, which is impregnated with a perfluorine/partial fluorine/hydrocarbon based hydrogen ion conductive ionomer (pore-filling membrane; PFM).

For effective PFM production, the ionomer must be completely dissolved or dispersed in a solvent. At this time, in order to achieve environmental problems, ease of molding, and complete removal of the solvent when removing the solvent for film formation, it is preferable to use water and alcohol co-solvent instead of the organic solvent. Thus, the perfluorosulfonic acid-based ionomer used in the manufacture of polymer electrolyte membranes, catalyst binders, and PFM is prepared by emulsion polymerization and used in an emulsion state of water and isopropyl alcohol co-solvent.

As examples of emulsion polymerization of perfluorosulfonic acid-based ionomers, methods for preparing perfluorinated sulfonated ionomer (PFSA) emulsions from fluorine monomers through aqueous emulsion polymerization are disclosed in US 2005/0096442 and US 7,071,271. This method is effective in preparing an aqueous emulsion of perfluorosulfonic acid-based ionomer (PFSA) having a relatively stable hydrophilicity under water and alcohol co-solvent conditions. However, due to the inherent synthetic characteristics of emulsion polymerization, there is a limit to obtaining high molecular weight, and when the fuel cell is operated by introducing it into a membrane electrode assembly (MEA), the operation performance of the fuel cell is lowered due to the low durability of the electrolyte membrane. there was.

Accordingly, the inventors of the present invention completed the present invention by inventing a coating composition having excellent ionic conductivity and significantly improving the mechanical durability of a polymer electrolyte membrane while searching for a new perfluorosulfonic acid ionomer coating composition to solve the above problems.

US Patent No. 7,071,271 (Announced on May 5, 2005)

An object of the present invention is to provide a perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator having excellent ionic conductivity and significantly improving mechanical durability of a polymer electrolyte membrane by deriving a specific particle size range suitable for coating a porous support.

In order to achieve the above purpose,

The present invention provides a perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator comprising a dispersion medium in which water and alcohol are mixed in a weight ratio of 2:8 to 5:5, a perfluorosulfonic acid ionomer, and a fluorine-containing silane compound.

The present invention can improve the dispersibility of the perfluorosulfonic acid ionomer coating composition of the present invention by including a perfluorosulfonic acid ionomer and a fluorine-containing silane compound in a dispersion medium containing water and alcohol, and a porous support impregnated in the coating composition The durability of the membrane is improved, and it is possible to suppress cell performance deterioration even after operating the fuel cell several times.

1 is a cross-sectional view showing a high-pressure reactor used to prepare a perfluorosulfonic acid ionomer coating composition for manufacturing a fuel cell separator of the present invention.

Hereinafter, a perfluorosulfonic acid ionomer coating composition for manufacturing a fuel cell separator and a manufacturing method thereof according to the present invention will be described in detail.

The terms or words used in this specification and claims should not be construed as being limited to ordinary or dictionary meanings, and the inventors may appropriately define the concept of terms in order to explain their invention in the best way. It should be interpreted as a meaning and concept consistent with the technical idea of the present invention based on the principle that there is.

The present invention provides a perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator comprising a dispersion medium in which water and alcohol are mixed, a perfluorosulfonic acid ionomer, and a fluorine-containing silane compound.

The weight ratio of water and alcohol blended in the dispersion medium is preferably about 2:8 to 5:5. If the ratio is out of the range, the size distribution of the particles may be too wide, and dispersion may not be achieved.

The alcohol may be an alcohol containing at least one hydroxyl group in a main chain having 1 to 10 carbon atoms. More preferably, an alcohol in which one or more hydroxyl groups are bonded to a main chain having 1 to 7 carbon atoms may be used, but the present invention is not limited thereto. The mixing ratio of the water and alcohol may vary depending on the type of alcohol.

Preferably, the alcohol is methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopentyl alcohol, 2-methyl-1-butanol, neo Pentyl alcohol, diethyl ketinol, methyl propyl ketinol, methyl isopropyl ketinol, dimethyl ethyl ketinol, 1-hexanol, 2-hexanol, 3-hexanol, 2-methyl-1-pentanol, 3- Methyl-1-pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentane ol, 3-methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol , 2-ethyl-1-butanol, 1-heptanol, 2-heptanol, 3-heptanol, 4-heptanol, and mixtures thereof.

The perfluorosulfonic acid ionomer refers to one of ion conductive polymers having a fixed ion (mainly anion) covalently attached to the side chain of the polymer, and the perfluorosulfonic acid ionomer includes a functional group containing sulfonic acid or a sulfonic acid salt. . The sulfonate may be any one selected from the group consisting of lithium sulfonate salt, sodium sulfonate salt, potassium sulfonate salt, magnesium sulfonate salt, calcium sulfonate salt, ammonium sulfonate salt, and alkylammonium sulfonate salt.

Preferably, the equivalent weight (EW) of the perfluorosulfonic acid ionomer may be 1000 to 1100 g/eq, and acid capacity may be 1.0 to 2.0 meq/g. If it is out of the above condition range, the average particle size range for coating the porous support may be out of range, or dispersion stability may be reduced.

The amount of perfluorosulfonic acid ionomer included in the coating composition is preferably 5 to 20 parts by weight based on 100 parts by weight of the dispersion medium. When the amount of the perfluorosulfonic acid ionomer is less than 5 parts by weight, the ionic conductivity is greatly reduced, which may be unsuitable for manufacturing a separator, and when the amount exceeds 20 parts by weight, the coating composition has poor dispersibility, resulting in reduced adhesion to the porous support. .

The average particle size of the ionomer in the ionomer coating composition is preferably 950 nm to 985 nm. If the average particle size of the ionomer is out of the numerical range, ionic conductivity may be reduced, which may be unsuitable for manufacturing a polymer electrolyte membrane, or mechanical strength of the polymer electrolyte membrane may be extremely low, resulting in poor practicality.

The fluorine-containing silane compound may be any one selected from the group consisting of 2-triethoxysilylethylpentadecafluordecylsulfide, 2-trimethoxysilylethylpentadecafluordecylsulfide, and mixtures thereof. The fluorine-containing silane compound is preferably 1 to 3 parts by weight based on 100 parts by weight of the dispersion medium. When the amount of the fluorine-containing silane compound is less than 1 part by weight, the durability enhancement effect of the polymer electrolyte membrane is hardly achieved, and when it exceeds 3 parts by weight, the ionic conductivity of the electrolyte membrane is reduced and the performance of the fuel cell may be deteriorated.

In a specific embodiment of the present invention, by adding 1 to 3 parts by weight of a fluorine-containing silane compound to a perfluorosulfonic acid ionomer coating composition, durability of a polymer electrolyte membrane prepared using the coating composition can be remarkably enhanced.

In addition, the perfluorosulfonic acid ionomer coating composition for preparing the fuel cell separator,

a) preparing a dispersion medium in which water and alcohol are blended in a weight ratio of 2:8 to 5:5;

b) preparing a mixture by adding a perfluorosulfonic acid ionomer and a fluorine-containing silane compound to the dispersion medium prepared in step a); and

c) preparing a perfluorosulfonic acid ionomer coating composition by introducing the mixture into a reactor and then reacting.

Hereinafter, the manufacturing method of the perfluorosulfonic acid ionomer coating composition for manufacturing a fuel cell separator of the present invention will be described in detail step by step.

In the manufacturing method of the present invention, step a) is a step of preparing a dispersion medium in which water and alcohol are mixed in a weight ratio of 2:8 to 5:5.

Since the dispersion medium has been described above, a description thereof will be omitted.

In the production method of the present invention, step b) is a step of preparing a mixture by adding a perfluorosulfonic acid ionomer and a fluorine-containing silane compound to the dispersion medium prepared in step a).

Since the perfluorosulfonic acid ionomer and the fluorine-containing silane compound have been described above, a description thereof will be omitted.

In the production method of the present invention, step c) is a step of preparing a perfluorosulfonic acid ionomer coating composition by introducing the mixture into a reactor and then reacting.

The temperature in the reactor is preferably 100 to 160°C. When the temperature is below 100° C., the particle size distribution of the ionomer may be too broad or not dispersed at all. On the other hand, when the temperature exceeds 160 ° C., the ionomer reactor may be damaged by the high-temperature dispersion, the chemical structure of the ionomer may be decomposed, or serious quality degradation may occur. Also, the pressure in the reactor is preferably 5 to 20 bar.

In the present invention, the reaction time is preferably completed within 6 to 9 hours. When the reaction time is less than 6 hours, there is a problem that the particle size distribution of the ionomer is widened, and when the reaction time exceeds 9 hours, there is a problem that the average particle size of the ionomer is excessively lowered, and economical efficiency is low.

Hereinafter, the present invention will be described in detail with reference to preparation examples and examples.

However, the following Preparation Examples and Examples are only to illustrate the present invention, and the content of the present invention is not limited by the following Preparation Examples and Examples.

<Preparation Example 1> Preparation of perfluorosulfonic acid ionomer coating composition

PFSA-based ionomer (EW: 1000g/eq, Acid Capacity: 1.0meq/g, and Density: 1.0g/ml) 5 parts by weight and 1 part by weight of 2-triethoxysilylethylpentadecafluorodecylsulfide (first silane) were added. Then, a perfluorosulfonic acid ionomer coating composition (dispersion) was prepared by reacting for 6 hours under conditions of a temperature of 120° C. and a pressure of 5 bar in the reactor.

The average particle size of the ionomer in the ionomer coating composition was measured using Malvern's nano particle size analyzer (Zetasizer Nano ZSP), and the results are shown in Table 1 below.

<Preparation Examples 2 to 9>

All processes were performed in the same manner as in Preparation Example 1 except that the temperature and time conditions in the reactor were changed as shown in Table 1 below.

Temperature (℃) time (h) Particle size (nm) Preparation Example 1 120 6 961 Preparation Example 2 180 6 924 Preparation Example 3 160 6 955 Production Example 4 100 6 983 Preparation Example 5 80 6 1284 Preparation Example 6 60 6 1563 Preparation Example 7 120 9 954 Preparation Example 8 120 12 942 Preparation Example 9 120 24 944

As a result, as shown in Table 1, when the reaction temperature is less than 100 ° C, the average particle size of the ionomer in the ionomer coating composition is excessively high, while when the reaction temperature exceeds 160 ° C, the average particle size of the ionomer is significantly lowered. confirmed that In addition, it was confirmed that the average particle size of the ionomer in the ionomer coating composition decreased as the reaction time increased. Therefore, by confirming that the ionomer coating compositions prepared in Preparation Examples 1, 3, 4 and 7 have an average particle size suitable for coating a porous support, the optimal reaction temperature and time (6 Reaction for 9 hours) was derived.

<Preparation Examples 10 to 18, Comparative Examples 1 to 6>

All processes were performed in the same manner as in Preparation Example 1 except that the content (parts by weight) of each component of the perfluorosulfonic acid ionomer coating composition was mixed as shown in Table 1 below.

Dispersion medium (parts by weight) PFSA (parts by weight) Fluorine-Containing Silane Compounds Particle size (nm) (parts by weight) IPA acetone H ₂ O 1st PFSA 2nd PFSA primary silane Second silane Preparation Example 1 80 - 20 5 - One - 961 Preparation Example 10 80 - 20 20 - One - 983 Preparation Example 11 80 - 20 30 - One - 1056 Preparation Example 12 40 - 60 5 - One - 1226 Preparation Example 13 - 80 20 5 - One - 1321 Preparation Example 14 - 80 20 20 - One - 1357 Preparation Example 15 - 80 20 30 - One - 1386 Preparation Example 16 - 40 60 5 - One - 1494 Comparative Example 1 80 - 20 5 - - - 972 Comparative Example 2 80 - 20 5 - 0.1 - 964 Comparative Example 3 80 - 20 5 - 5 - 1013 Comparative Example 4 80 - 20 5 - - One 998 Comparative Example 5 80 - 20 - 5 One - 869 Comparative Example 6 80 - 20 - 20 One - 893

(In Table 2, the first PFSA is a PFSA having an EW of 1000 g/eq, the second PFSA is a PFSA having an EW of 800 g/eq, and the first silane is 2-triethoxysilylethylpentadecafluordecylsulfide, the second silane is tetrafluorosilane.)

As a result, it was confirmed that the ionomer coating composition prepared according to the present invention had an average particle size suitable for coating a porous support.

However, in the case of Preparation Example 12, it was confirmed that the water content in the dispersion medium was high, and the particle size of the ionomer in the ionomer coating composition was excessively increased, making it difficult to disperse.

In addition, when acetone was selected as the type of organic solvent in the dispersion medium, the average particle size of the ionomer in the ionomer coating composition was relatively high.

<Example 1> Evaluation of dispersion stability

In order to confirm the dispersion stability of the ionomer coating composition prepared by the present invention, the ionomer coatings prepared in Preparation Examples 1, 10 to 16, and Comparative Examples 1 to 6 were prepared using Haake RheoStress 1 (Thermo Scientific Inc, USA) equipment. Put the spin needle in the composition and rotate it, measure the shear rate and shear stress, and use the obtained shear rate and shear stress to determine the dispersion stability (shear stress / (shear rate - shear stress) ) was calculated.

dispersion stability Preparation Example 1 1.146 Preparation Example 10 1.132 Preparation Example 11 1.014 Preparation Example 12 1.046 Preparation Example 13 1.015 Preparation Example 14 1.022 Preparation Example 15 1.017 Preparation Example 16 1.012 Comparative Example 1 1.11 Comparative Example 2 1.096 Comparative Example 3 1.064 Comparative Example 4 1.089 Comparative Example 5 1.073 Comparative Example 6 1.067

As a result, in the case of the ionomer coating composition prepared according to the present invention, as described in Table 3, it was confirmed that it had a level of dispersion stability suitable for coating a porous support.

However, in the case of Preparation Examples 11 and 15, the content of the PFSA ionomer in the ionomer coating composition was excessively included and the dispersion was not properly performed, so the dispersion stability was relatively low, and in the case of Preparation Examples 12 and 16, the dispersion medium The dispersion stability was measured to be relatively low due to the low alcohol content.

<Example 2> Durability evaluation of polymer electrolyte membrane

To evaluate the durability of the polymer electrolyte membrane using the ionomer coating composition prepared according to the present invention, the mechanical strength of the membrane was measured. Specifically, a PTFE porous support having an average thickness of 0.16 μm, an average pore size, and a porosity of 75% was impregnated with the ionomer coating compositions of Preparation Examples 1, 10, 13, and 14 and Comparative Examples 1, 2, and 4, and maintained at 80° C. After drying for 1 hour, a polymer electrolyte membrane was prepared by performing an annealing process at 180° C. for 10 minutes.

After cutting the prepared polymer electrolyte membrane into a size of 1 cm × 4 cm, it was hydrated in ultrapure water at 30 ° C. for 24 hours and expanded. Changes in the transverse, longitudinal, and plane directions of the polymer electrolyte membrane before and after expansion were measured using a digital micrometer. (%) was calculated.

Area change rate (%) Thickness change rate (%) Preparation Example 1 3 6 Preparation Example 10 0 4 Preparation Example 13 9 14 Preparation Example 14 7 11 Comparative Example 1 15 26 Comparative Example 2 12 19 Comparative Example 4 10 26

As a result, as shown in Table 4, when the polymer electrolyte membrane was prepared using the ionomer coating composition prepared according to the present invention, it was confirmed that the area and thickness change rates were significantly reduced and the durability of the membrane was greatly improved.

On the other hand, in the case of Comparative Examples 1 and 2, the durability of the membrane was measured relatively low because the first silane was not included or included in a very small amount in the ionomer coating composition, and in the case of Comparative Example 4 including a silane different from the present invention, the durability of the membrane was similarly appeared to be weak.

This means that when the electrolyte membrane impregnated with the coating composition containing the fluorine-containing silane compound of the present invention is used during operation of the fuel cell, the starting performance of the fuel cell can be maintained for a long period of time due to the excellent mechanical durability of the electrolyte membrane.

<Example 3> Evaluation of ionic conductivity

After preparing a polymer electrolyte membrane in the same manner as described in Example 2 using the ionomer coating compositions of Preparation Examples 1 and 10 and Comparative Examples 1 and 3, the in-plane ionic conductivity of the membrane was measured at temperature and Resistance (R) was measured using the alternating current impedance method using a four-electrode cell in which humidity is controlled. The ionic conductivity was measured by varying the temperature condition to 25, 40, 60 and 80 °C under the condition of 100% relative humidity (RH).

In-plane ionic conductivity (S/cm) as a function of temperature 25℃ 40℃ 60℃ 80℃ Preparation Example 1 0.092 0.111 0.140 0.168 Preparation Example 10 0.096 0.115 0.146 0.176 Comparative Example 1 0.099 0.121 0.144 0.179 Comparative Example 3 0.082 0.102 0.127 0.146

As a result, as shown in Table 5, when the polymer electrolyte membrane was prepared using the ionomer coating composition prepared according to the present invention, the ion conductivity was similar to that of the conventional polymer electrolyte membrane (Comparative Example 1) at each temperature condition. confirmed to have

However, in the case of Comparative Example 3 in which the first silane was excessively included in the ionomer coating composition, the ionic conductivity of the membrane was rather decreased.

This means that the polymer electrolyte membrane impregnated with the ionomer coating composition prepared according to the present invention maintains excellent ionic conductivity and has significantly improved durability compared to conventional polymer electrolyte membranes.

Although the present invention has been described through specific details and limited manufacturing examples and examples as described above, this is only provided to help the overall understanding of the present invention, and the present invention is not limited to the above manufacturing examples and examples. , Those skilled in the art in the field to which the present invention belongs can make various modifications and variations from these descriptions.

Therefore, the spirit of the present invention should not be limited to the described manufacturing examples and examples, and not only the claims to be described later, but also all equivalent or equivalent modifications to these claims fall within the scope of the spirit of the present invention. will do it

Claims (8)

It includes a dispersion medium in which water and alcohol are blended in a weight ratio of 2:8 to 5:5, a perfluorosulfonic acid ionomer, and a fluorine-containing silane compound,
A perfluorosulfonic acid ionomer coating composition for producing a fuel cell separator, characterized in that it comprises 5 to 20 parts by weight of a perfluorosulfonic acid ionomer and 1 to 3 parts by weight of a fluorine-containing silane compound based on 100 parts by weight of the dispersion medium.
delete According to claim 1,
The alcohol is methanol, ethanol, 1-propanol, isopropyl alcohol, butanol, isobutanol, 2-butanol, tert-butanol, n-pentanol, isopentyl alcohol, 2-methyl-1-butanol, neopentyl alcohol, di Ethyl Kebinol, Methyl Propyl Kebinol, Methyl Isopropyl Kebinol, Dimethyl Ethyl Kebinol, 1-Hexanol, 2-Hexanol, 3-Hexanol, 2-Methyl-1-Pentanol, 3-Methyl-1- Pentanol, 4-methyl-1-pentanol, 2-methyl-2-pentanol, 3-methyl-2-pentanol, 4-methyl-2-pentanol, 2-methyl-3-pentanol, 3- Methyl-3-pentanol, 2,2-dimethyl-1-butanol, 2,3-dimethyl-1-butanol, 2,3-dimethyl-2-butanol, 3,3-dimethyl-1-butanol, 2-ethyl -1-butanol, 1-heptanol, 2-heptanol, 3-heptanol and 4-heptanol, and any one alcohol selected from the group consisting of mixtures thereof, characterized in that perfluorinated fuel cell separator manufacturing A sulfonic acid ionomer coating composition.
According to claim 1,
A perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator, characterized in that the average particle size of the ionomer in the ionomer coating composition is 950 nm to 985 nm.
According to claim 1,
The perfluorosulfonic acid ionomer coating composition for preparing the fuel cell separator,
a) preparing a dispersion medium in which water and alcohol are blended in a weight ratio of 2:8 to 5:5;
b) preparing a mixture by adding a perfluorosulfonic acid ionomer and a fluorine-containing silane compound to the dispersion medium prepared in step a); and
c) preparing a perfluorosulfonic acid ionomer coating composition by introducing the mixture into a reactor and then reacting to prepare a perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator.
According to claim 5,
The perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator, characterized in that the temperature in the reactor of step c) is 100 to 160 ° C.
According to claim 5,
The pressure in the reactor in step c) is 5 to 20 bar (bar), characterized in that, the perfluorosulfonic acid ionomer coating composition for producing a fuel cell separator.
According to claim 5,
The reaction time of step c) is 6 to 9 hours, characterized in that, the perfluorosulfonic acid ionomer coating composition for preparing a fuel cell separator.

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