KR100695107B1 - Electrolyte for fuel cell and fuel cell employing the same - Google Patents

Abstract

The present invention provides an electrolyte for a fuel cell and a fuel cell employing the same, comprising a proton conductive resin obtained by combining a main chain made of a polyurea resin with a side chain having an active hydrogen group bonded to an end thereof. The electrolyte has improved proton conductivity, heat resistance and mechanical strength.

Description

 Electrolyte for fuel cell and fuel cell employing the same {Electrolyte for fuel cell and fuel cell employing the same}

The present invention relates to a fuel cell electrolyte and a fuel cell employing the same, and more particularly, to a fuel cell electrolyte having a improved proton conductivity, heat resistance and mechanical strength, and a fuel cell employing the same.

In recent years, as the global environment worsens, the development of the spread of clean energy has become a very small task worldwide. For example, in traffic relations, urban air pollution due to exhaust gas from internal combustion engines such as automobiles has become a problem due to an increase in the number of vehicles driven due to the development of the transportation network. As a countermeasure, electric vehicles and automobiles for electric and internal combustion engines, called hybrid cars, have been developed. The use of fuel cells, etc., is also promising as an energy source that is lightweight and easy to handle and does not pollute the atmosphere. In addition, the introduction of fuel cells into the home is the same as in the transportation sector.

There are various types of fuel cells, such as alkali type, phosphoric acid type, molten carbonate type, solid polymer electrolyte type, solid polymer type, etc., depending on the type of electrolyte, which can operate at low temperature, is easy to handle, and also has a power density. The high solid polymer electrolyte type is attracting attention as an energy source for electric vehicles and households.

A proton conductive membrane is used for the electrolyte of this solid polymer electrolyte fuel cell. Proton conductive membranes require high ion conductivity for protons involved in the electrode reaction of a fuel cell. As such proton conductive membranes, super acidic acid-containing fluorine-based polymers have been known for a long time. However, such a polymer electrolyte material is very expensive because it is a fluorine-based polymer, and there is a problem that it is necessary to always supply water by humidifying from the fact that the medium for proton conduction is water.

By the way, the proton conductive membrane which contained ionic dissociation groups, such as a carboxylic acid group, a sulfonic acid group, and a phosphoric acid group, in an aromatic skeleton in order to make a proton conductivity is described in Unexamined-Japanese-Patent No. 2002-280019 or 2002-358978. However, the ion dissociation group is particularly susceptible to desorption at high temperatures, and may also impair the flexibility of the proton conductive membrane, and also has a problem of low proton conductivity. Although Japanese Unexamined Patent Publication No. 8-504293 has a related description, it does not disclose proton conductivity.

In addition, the cited document 'Development of ion-exchange membranes for solid polymer fuel cells' (GMC, published in May 2000, p.98)} introduces active hydrogen groups by reacting sultone with polybenzimidazole. It is described how to. However, only sulfonic acid groups can be introduced by this method, and this method cannot be applied to other active hydrogen groups.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a fuel cell electrolyte having excellent proton conductivity, heat resistance, and mechanical strength, and a fuel cell having the electrolyte.

The technical problem of the present invention is achieved by an electrolyte for a fuel cell comprising a proton conductive resin having a side chain having an active hydrogen group bonded to a terminal thereof formed of a polyurea resin.

Another technical problem of the present invention is achieved by a fuel cell having a cathode, an anode and the above-described electrolyte interposed therebetween.

At least one selected from the cathode and the anode includes an electrolyte including a proton conductive resin having a side chain having an active hydrogen group bonded to a terminal thereof formed of a polyurea resin.

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

The fuel cell electrolyte of the present invention is not particularly limited in form, and may be obtained in the form of a membrane, hereinafter referred to as "electrolyte membrane".

The electrolyte membrane of the present invention is composed of a proton conductive resin in which a main chain made of polyurea resin is bonded to a side chain formed by bonding an active hydrogen group to an end thereof.

According to the above constitution, an electrolyte membrane for fuel cells excellent in proton conductivity, heat resistance and mechanical strength can be obtained.

In addition, the electrolyte membrane for a fuel cell of the present invention is the above-described electrolyte membrane for a fuel cell, wherein an acryl isocyanate compound is combined with one or both of a urea group or a urethane group included in a polyurea resin, and active hydrogen is added to the acryl isocyanate compound. Group containing acrylate compound is compounded.

Moreover, the acryl isocyanate compound also contains the methacryl isocyanate compound which the methyl group couple | bonded with the alpha position. The active hydrogen group-containing acrylic isocyanate compound also includes an active hydrogen group-containing methacryl isocyanate compound having a methyl group bonded to an alpha position.

According to the above configuration, an electrolyte membrane for a fuel cell excellent in proton conductivity can be obtained.

In the fuel cell electrolyte membrane of the present invention, the active hydrogen group is at least one selected from sulfonic acid group, carbonic acid group, phosphoric acid group and hydroxyl group.

According to the said structure, the electrolyte membrane for fuel cells excellent in proton conductivity and flexibility can be obtained.

In the fuel cell electrolyte membrane of the present invention, a sultone compound is combined with either or both of a urea group or a urethane group included in the polyurea resin.

According to the above configuration, an electrolyte membrane for a fuel cell excellent in proton conductivity can be obtained.

In the electrolyte membrane for a fuel cell of the present invention, the hydroxyl group is bonded to a polyoxyalkylene chain.

According to the above configuration, an electrolyte membrane for a fuel cell excellent in proton conductivity can be obtained.

The fuel cell electrolyte membrane of the present invention is the fuel cell electrolyte membrane described above, and has a thermal decomposition temperature of 180 ° C. or higher and a storage modulus at 150 ° C. in the range of 1 × 10 ⁷ Pa to 1 × 10 ⁹ Pa.

According to the above structure, an electrolyte membrane for fuel cells having heat resistance can be obtained.

Next, the fuel cell of the present invention is characterized in that any one of the fuel cells has an electrolyte membrane described above.

According to the said structure, the high performance fuel cell excellent in the electric power generation characteristic can be provided.

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described in detail.

The electrolyte membrane for a fuel cell of the present invention is composed of a proton conductive resin formed by combining a main chain made of a polyurea resin with a side chain having an active hydrogen group bonded to an end thereof. The side chains in the present invention branch from the urea group and / or urethane group in the main chain of the polyurea resin. Other than this structure, high proton conductivity cannot be obtained.

More specifically, in the electrolyte membrane for fuel cells of the present invention, an acryl isocyanate compound is combined with any one or both of urea groups or urethane groups included in the polyurea resin, and an active hydrogen group-containing acrylate is combined with the acryl isocyanate compound. The compound is comprised by combining. The combined active hydrogen group-containing acrylate compound has at least one active hydrogen group selected from sulfonic acid group, carbonic acid group, phosphoric acid group, and hydroxyl group, and proton is conducted by the presence of this active hydrogen group, and proton conductivity is applied to the electrolyte membrane for fuel cell. Is given. The active hydrogen group may be a mixture of any of the above active hydrogen groups. Particularly preferred among these are sulfonic acid groups and phosphoric acid groups.

In addition, polyurea resin constituting the main chain is characterized by excellent heat resistance and chemical resistance, it is possible to increase the heat resistance and mechanical strength of the electrolyte membrane for fuel cells.

The polyurea resin has at least one selected from urea groups and urethane groups in its molecular structure, depending on the kind of raw material monomer. In these urea and urethane groups, there are active hydrogens bound to nitrogen. The isocyanate group of the acrylic isocyanate compound reacts with this active hydrogen to form a side chain of the acrylic isocyanate compound in the polyurea resin. This compounded acrylic isocyanate compound has a carbon double bond in the molecule. An active hydrogen group-containing acrylate compound having a carbon double bond in the molecule is polymerized with respect to this carbon double bond. The active hydrogen group-containing acrylate compound includes the active hydrogen group, and is located at almost the end of the side chain in which the active hydrogen group is formed.

In addition, the acryl isocyanate compound also contains the methacryl isocyanate compound which the methyl group couple | bonded with the alpha position. The active hydrogen group-containing acrylic isocyanate compound also includes an active hydrogen group-containing methacrylic isocyanate compound having a methyl group bonded to an alpha position.

As mentioned above, the proton conductive resin which the side chain which the active hydrogen group couple | bonded with the terminal is couple | bonded is formed in the main chain which consists of polyurea resin. By forming the proton conductive resin in the form of a membrane, the electrolyte membrane for a fuel cell according to the present invention can be obtained.

Polyurea resin is obtained by reaction of polyisocyanate and polyamine, for example.

Specific examples of the polyisocyanate are as follows. Examples of the compound having an aromatic ring include toluene diisocyante, diphenylmethane diisocyanate (hereinafter referred to as "MDI"), xylene diisocyanate, naphthalene diisocyanate, and the like. Isophorone diisocyanate, cyclohexane diisocyanate, and the like, and hexamethylene diisocyanate, lidine diisocyanate and the like as aliphatic compounds. As the polyisocyanate in the present invention, derivatives of the above-mentioned compounds may also be used.

These polyisocyanates can also be used together as needed. The NCO% of the polyisocyanate is usually 20 to 48 mol%, preferably 25% to 48 mol%. Outside this range, the heat resistance and mechanical strength of the electrolyte membrane for fuel cells are lowered.

Examples of the polyamine include aliphatic diamines (such as ethylenediamine and propylenediamine), alicyclic diamines (such as isophoronediamine), aromatic diamines ((polytetramethylene oxide-di-P-aminobenzoate), and (4, 4'-dia). Mino-3, 3'-diethylamino-5, 5'-diaminodiphenylmethane), (2, 2 ', 3, 3'-tetrachloro-4, 4'-diaminodiphenylmethane), ( 3, 3'-dichloro-4, 4'-diaminodiphenylmethane), (trimethylene-bis (4-aminobenzoate), (3, 5'- dimethylthiotoluenediamine), etc.] are mentioned. Of these polyamines, aromatic diamines are particularly preferred, and polyalkylene oxide-di-P-aminobenzoate is particularly preferred, and the amine titer is usually in the range of 28 to 200, and preferably 28 to 150. More preferably, the mechanical strength of the electrolyte membrane for a fuel cell is lowered outside this range.

The reaction of the polyisocyanate with the polyamine is usually in the NCO index 90 to 110, preferably 95 to 105. Outside this range, a film with good heat resistance and strength cannot be obtained.

Moreover, 2-methacryloyloxyethyl isocyanate, MOI (2-isocyanatoethyl methacrylate) etc. are mentioned as a specific example of acryl isocyanate compound.

Examples of the active hydrogen group-containing acrylate compound include 2-acrylamide-2-methylpropanesulfonic acid (hereinafter referred to as "TBAS"), styrene sulfonic acid, and the like having a sulfonic acid group. Acrylic acid (beta) -methacryloyloxyethyl hydrogen succinate (beta) -methacryloyloxyethyl hydrogen phthalate etc. are mentioned as an example which has a carbonic acid group. Examples of phosphate groups include mono (2-acryloyloxyethyl) added phosphate {mono (2-acryloyloxyethyl) added phosphate}, mono (2-methacryloyloxyethyl) added phosphate {mono (2-methacryloyloxyethyl ) added phosphate}, and the like. Trifunctional polyoxyalkyl, such as bifunctional polyoxyalkylenediglycol mono (meth) acrylate, such as monofunctional polyethyleneglycol mono (meth) acrylate and polypropylene glycol mono (meth) acrylate, having a hydroxyl group Lentri glycol mono (meth) acrylate etc. are mentioned. Among these, a bifunctional or more than one is preferable.

The reaction of the urea group (1) and / or the urethane group and the acryl isocyanate compound (2) in the polyurea resin is carried out by a known reaction in polyurethane in the presence of a solvent. An example of the reaction is shown in Scheme 1 below. In this reaction, dimethylformamide, dimethylsulfooxide, dimethylacetoamide, etc. are preferable as the solvent. You may use a urethanization catalyst as needed. As a urethanation catalyst, a tin compound is preferable.

Scheme 1

Moreover, in order to make an active-hydrogen-group containing acrylate compound (4) react with the reactant (3) of the urea group and / or urethane group in an polyurea resin, and an acryl isocyanate compound, well-known thermal polymerization and / or ultraviolet polymerization are mentioned. . Among these, especially ultraviolet polymerization is preferable. Examples of schemes are shown in Scheme 2 below. In this way, the proton conductive resin 5 can be obtained.

Scheme 2

Wherein n is a number from 1 to 100.

In addition to the above-mentioned method, the sulfonic acid group in the active hydrogen group may be introduced by reacting a sultone compound with either or both of the urea group and the urethane group in the polyurea resin. An example of the scheme is shown in Scheme 3 below. Specifically, sodium hydride or the like is added to the polyurea resin (6) to replace active hydrogen bonded to nitrogen contained in the urea group or urethane group with sodium (7), and then the sultone compound (8) is reacted with the sodium. Let's do it. At this time, the sultone compound cleaves into side chains and is compounded with the urea resin (9). In addition, the sulfonic acid group 10 derived from a sultone compound is formed in the terminal of a side chain by substituting with an acid. Examples of the sultone compound include (alkyl) propane sultone and butane sultone.

Scheme 3

In addition, the hydroxyl group in the active hydrogen group may be bonded to a polyoxyalkylene chain. Examples of the polyoxyalkylene chains include polyethylene oxide chains, polypropylene oxide chains, and polytetramethylene oxide chains. Of these, polyethylene oxide chains and polytetramethylene oxide chains are preferred in view of proton conductivity and mechanical properties. An example of the reaction for introducing the polyoxyalkylene chain is shown in Scheme 4 below. In this example, the acrylic isocyanate compound (12) is compounded with the polyurea resin (11), and further, the branched acrylate (13) having an ethylene oxide chain is polymerized at the carbon double bond at the terminal of the combined acrylic isocyanate compound. .

Scheme 4

Wherein x, y, z and w are each independently a number from 1 to 100.

Further, another example of the reaction for introducing the polyoxyalkylene chain is shown in Scheme 5 below. In this example, an acrylic isocyanate compound (12) is compounded with the polyurea resin (11), and a branched structure having a polyfunctional acrylate (14) and an ethylene oxide chain is formed at the carbon double bond at the terminal of the combined acrylic isocyanate compound. The acrylate 13 is polymerized.

Scheme 5

Wherein n is a number from 1 to 100.

The thermal decomposition temperature of the fuel cell electrolyte membrane is 180 ° C. or higher and the storage modulus at 150 ° C. is in the range of 1 × 10 ⁷ Pa to 1 × 10 ⁹ Pa. Outside this range, desirable heat resistance and mechanical properties cannot be obtained.

Next, the fuel cell concerning this invention is demonstrated concretely. The fuel cell according to the present invention is provided with a fuel membrane electrolyte membrane as the polymer membrane having proton conductivity.

The fuel cell is composed of a polymer film having proton conductivity and a cathode and an anode (a pair of electrodes) disposed in contact with both sides. Hydrogen in the fuel is electrochemically oxidized at the anode, producing protons and electrons. This proton is transported in the electrolyte membrane to reach the cathode to which oxygen is supplied.

On the other hand, electrons generated at the anode flow to the cathode through an external load connected to the fuel cell, and proton, oxygen, and electrons react at the cathode to generate water.

The electrode constituting the fuel cell is composed of a conductive material, a binder, and a catalyst. Any conductive material may be used as long as it has electrical conductivity, and various metals and carbon materials may be mentioned. For example, carbon black, such as acetylene black, activated carbon, graphite, etc. are mentioned, These are used individually or in mixture.

Moreover, although it is preferable to use the proton conductive resin of this invention as a binder, other resin can also be used. In such a case, the other resin is preferably a fluorine resin having water repellency. Among fluororesins, those having a melting point of 400 ° C. or lower are preferable, and examples thereof include polytetrafluoroethylene, tetrafluoroethylene-perfluoro alkylvinyl ether copolymer, and the like.

The catalyst of the electrode is not particularly limited as long as it is a metal that promotes the oxidation reaction of hydrogen and the reduction reaction of oxygen, and examples thereof include lead, iron, manganese, cobalt, chromium, gallium, vanadium, tungsten, ruthenium, iridium, Palladium, platinum, rhodium or their alloys.

As described above, according to the fuel cell electrolyte membrane of the present invention, proton conductivity, heat resistance, and mechanical strength can be improved. In addition, according to the fuel cell of the present invention, power generation characteristics can be further improved.

The fuel cell of the present invention may include an electrolyte including a proton conductive resin having a side chain having an active hydrogen group bonded to a terminal thereof in a main chain made of a polyurea resin to at least one selected from a cathode and an anode.

 EXAMPLE

Hereinafter, although an Example demonstrates this invention, this invention is not limited to this.

In addition, the measurement conditions of the physical property of the following Example are as follows.

 Proton conductivity: An electrode was formed by touching a platinum wire (diameter 0.2 mm) at 5 mm intervals on the surface of an electrolyte membrane having a size of 2 cm x 2 cm, and the resistance when alternating current (1 kHz) was applied was measured by an impedance analyzer. Proton conductivity was calculated by 1 / (R x T x D) from the electrode spacing, the slope of the resistance (R), the thickness (t) of the electrolyte membrane, and the width (D) of the electrolyte membrane. The proton conductivity was measured at 80 ° C. and 95% humidity.

Storage modulus: A viscoelasticity measuring device (Rheogel-E4000, manufactured by UMB Corporation) was used, and the temperature increase rate was 2 ° C, the temperature range was 20 to 300 ° C, the frequency was 100 Hz, and the displacement was 5 µm.

Pyrolysis temperature: The thermal analysis apparatus (The Max Science company make, a thermal analysis system WS002) was used, and it carried out at the temperature increase rate of 5 degree-C / min.

Example 1

20.8 parts by weight of MDI and 100 parts by weight of polytetramethylene oxide-di-P-aminobenzoate (amine value 89) are mixed, dissolved in 400 parts by weight of tetrahydrofuran (hereinafter referred to as THF), and a fluorine chalet (Schale). ), And THF was removed to obtain a polyurea resin.

1 g of polyurea resin obtained according to the above procedure was dissolved in 10 ml of THF, 0.4 g of MOI (2-isocyanate ethyl methacrylate) and 0.002 g of dibutyl tin dilaurylate were added to react at room temperature. Confirmed the loss. 1 part by weight of 50% by weight of a TBAS aqueous solution and 0.002 parts by weight of 2-hydroxy-2-methylpropiophenone as a polymerization initiator and 6 parts by weight of THF were added to the total amount of the solution, followed by degassing. Investigated for a minute. Thereafter, the reaction was washed with hot water (80 ° C.) for 1 hour and then dried. Thus, the proton conductive resin of Example 1 was obtained.

The obtained resin was molded into a sheet to obtain an electrolyte membrane. The proton conductivity of this electrolyte membrane was measured, which was 4 × 10 ^-4 S / cm.

Example 2

A polyurea resin was prepared in the same manner as in Example 1 above.

1 g of the obtained polyurea resin was dissolved in 10 ml of THF, 0.4 g of MOI and 0.002 g of dibutyl tin dilaurate were added to react at room temperature, and the disappearance of the isocyanate group was confirmed. 1.18 parts by weight of polyethylene glycol 400 monoacrylate and 0.002 parts by weight of 2-hydroxy-2-methylpropiophenone and 6 parts by weight of THF were mixed with respect to the total amount of the solution, followed by degassing, followed by ultraviolet light (400 W) for 7 minutes. Investigated. Thereafter, the reaction was washed with hot water (80 ° C.) for 1 hour and then dried. Thus, the proton conductive resin of Example 2 was obtained.

The obtained resin was molded into a sheet to obtain an electrolyte membrane. The proton conductivity of this electrolyte membrane was measured, which was 8 × 10 ⁻³ S / cm.

Example 3

A polyurea resin was prepared in the same manner as in Example 1 above.

2.5 g of the obtained polyurea resin was dissolved in 50 ml of dimethylformamide (DMF), placed in a reaction vessel, and the atmosphere in the vessel was replaced with nitrogen. Subsequently, 60% purity and 195 mg of NaH were added to the reaction vessel and reacted at -5 ° C for 15 minutes. Subsequently, a solution in which 360 mg of 1,3-propanesultone was dissolved in 5 ml of DMF was added and reacted at 50 ° C. for 2 hours. The reaction was filtered and transferred to 300 ml of diethyl ether to precipitate a polymer. Clear water was removed in a centrifuge, dissolved in 5 ml of DMF again, and 200 ml of 15% by volume aqueous hydrochloric acid solution was added to carry out proton exchange. After washing and drying again, it was dissolved in THF, cast into a chalet and dried, and then washed with hot water and dried again to obtain a proton conductive resin of Example 3.

The obtained resin was molded into a sheet to obtain an electrolyte membrane. The proton conductivity of this electrolyte membrane was measured, which was 5.4 × 10 ⁻⁴ S / cm.

In addition, the thermal decomposition temperature of the obtained proton conductive resin was 230 degreeC. In addition, the storage modulus at 150 ° C. was 1.0 × 10 ⁸ Pa.

Example 4

0.5 g of each of the proton conductive resins of Example 2 and Example 3 was dissolved in THF, and cast into a chalet to obtain an electrolyte membrane of Example 4. The proton conductivity of this electrolyte membrane was measured and found to be 5.4 × 10 ⁻⁴ to 8 × 10 ⁻³ S / cmS / cm.

Comparative Example 1

A polyurea resin was prepared in the same manner as in Example 1 above. This polyurea resin was dissolved in THF, and cast into a chalet to obtain an electrolyte membrane of Comparative Example 1. The proton conductivity of this electrolyte membrane was measured, which was 3 × 10 ^-6 S / cm.

As described above, it can be seen that the electrolyte membranes of Examples 1 to 4 significantly improved the proton conductivity compared with the electrolyte membrane of Comparative Example 1.

 According to the present invention, an electrolyte membrane for a fuel cell, which is a proton conductive membrane excellent in proton conductivity, heat resistance, and mechanical strength, can be produced.

Claims (8)

A main chain made of a polyurea resin, including a proton conductive resin having a side chain having an active hydrogen group bonded to the terminal thereof, At least one selected from the urea group and urethane group included in the polyurea resin, an acryl isocyanate compound is compounded, and an active hydrogen group-containing acrylate compound is compounded with the acryl isocyanate compound, or the polyurea An electrolyte for a fuel cell, wherein a sultone compound is combined with at least one selected from urea and urethane groups included in the resin. delete The fuel cell electrolyte of claim 1, wherein the active hydrogen group is at least one selected from a sulfonic acid group, a carbonic acid group, a phosphoric acid group, and a hydroxyl group. delete 4. The fuel cell electrolyte of claim 3, wherein the hydroxyl group is bonded to a polyoxyalkylene chain. The fuel cell electrolyte of claim 1, wherein the electrolyte has a pyrolysis temperature of 180 ° C. or higher and a storage modulus at 150 ° C. of 1 × 10 ⁷ Pa to 1 × 10 ⁹ Pa. A fuel cell comprising a cathode, an anode, and the electrolyte for a fuel cell according to any one of claims 1, 3, 5, and 6 interposed therebetween. The method of claim 7, wherein at least one selected from the cathode and the anode, A fuel cell, comprising: an electrolyte comprising a proton conductive resin having a side chain having an active hydrogen group bonded to a terminal thereof in a main chain made of a polyurea resin.