KR100612897B1 - Proton conductive electrolyte, preparing method thereof, and fuel cell using the same - Google Patents

Abstract

The present invention provides a proton conductive electrolyte comprising a polymerization product of a polyurethane compound, polyethylene (meth) acrylic acid, and a crosslinking agent, a method of manufacturing the same, and a fuel cell having the same. The proton conductive electrolyte of the present invention is less expensive to manufacture than conventional polybenzimidazole and Nafion, and is easy to manufacture a film by applying a solvent casting method, and also easy to control the thickness. In addition, it is a polymer electrolyte membrane having high mechanical strength and flexibility, and having greatly improved ion conductivity. By using the above-described proton conductive electrolyte, a fuel cell capable of operating under conditions of high temperature and no humidification of 100 ° C. or higher and having improved power generation performance can be manufactured.

Description

Proton conductive electrolyte, preparing method, and fuel cell using the same

1 is a graph showing the conductivity change with temperature in the proton conductive electrolyte according to Example 1 of the present invention,

FIG. 2 is a graph showing the relationship between the current density in the initial state and the battery voltage in the fuel cell according to the fourth embodiment of the present invention.

The present invention relates to a proton conductive electrolyte, a method for manufacturing the same, and a fuel cell using the same, and more particularly, a proton conductive electrolyte suitable for a high temperature fuel cell having excellent ion conductivity characteristics even at high temperature, and a method of manufacturing the same and the proton conductive electrolyte. It relates to a fuel cell.

Background Art Conventionally, ion conductors in which ions move by applying a voltage are known. This ion conductor is widely used as an electrochemical device, such as a battery and an electrochemical sensor.

For example, in fuel cells, in terms of power generation efficiency, system efficiency, and long-term durability of a component, good proton conductivity can be obtained in a low humidity operation condition of 100% to 300 ° C at a low humidity or a relative humidity of 50% or less. There is a demand for a stable proton conductor.

In the development of a conventional polymer electrolyte fuel cell, it has been considered in view of the above requirements. In a polymer electrolyte fuel cell using a perfluorocarbon sulfonic acid membrane as an electrolyte membrane, the relative humidity is 50% or less at an operating temperature of 100 to 300 ° C. In this case, there is a disadvantage in that sufficient power generation performance cannot be obtained.

In addition, a fuel cell using an electrolyte membrane containing a proton conductivity imparting agent, a fuel cell using a silica dispersion film, a fuel cell using an inorganic-organic composite membrane, a fuel cell using a phosphate dope graft membrane, or a fuel cell using an ionic liquid composite membrane have.

Also disclosed is a solid polymer electrolyte membrane made of polybenzimidazole doped with a strong acid such as phosphoric acid (US Pat. No. 5,525,436).

However, the above-described electrolyte membrane has a problem in that it is impossible to stably exhibit power generation performance at high temperatures. In particular, long-term stability under high operating temperatures of 100 to 300 ° C., no humidification or relative humidity of 50% or less is insufficient.

Accordingly, the technical problem to be achieved by the present invention is to solve the above-mentioned problems, maintain high ionic conductivity even at high temperature, suitable for high temperature polymer electrolyte membrane without deformation of electrolyte membrane, its production method and improved power generation performance using the same. To provide a fuel cell.

In the present invention to achieve the above technical problem,

Provided is a proton conductive electrolyte comprising a polymerization product of a polyurethane-based compound represented by Formula 1, a polyethylene (meth) acrylic acid represented by Formula 2, and a crosslinking agent.

[Formula 1]

Wherein R is a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C4-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C2-C20 hetero Arylene group,

a is a number from 10 to 500,

B is H ⁺ , NH 4 ⁺ or an alkali metal ion.

[Formula 2]

Wherein R 'is hydrogen or a methyl group ,

m is 70 to 90 mol%, n is 10 to 30 mol%,

b is a number from 50 to 1000.

Another technical problem of the present invention is to obtain a corresponding salt by adding a base to polyethylene acrylic acid (PEAA) represented by the following formula (2);

Adding a polyurethane compound, a crosslinking agent, and a solvent represented by Formula 1 to the salt to obtain a mixture; And

It is made by the method for producing a proton conductive electrolyte, characterized in that it comprises the step of preparing the above-mentioned proton conductive electrolyte by performing a polymerization reaction of the mixture.

[Formula 1]

Wherein R is a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C4-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C2-C20 hetero Arylene group,

a is a number from 10 to 500,

B is H ⁺ , NH ₄ ⁺ or an alkali metal ion,

[Formula 2]

Wherein R 'is hydrogen or a methyl group,

m is 70 to 90 mol%, n is 10 to 30 mol%,

b is a number from 50 to 1000.

Another technical problem of the present invention is a fuel field including a proton conductive electrolyte.

Is done by

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

The proton conductive electrolyte of the present invention polymerizes (crosslinks) a polyurethane-based compound represented by the following Chemical Formula 1 and a polyethylene (metha) acrylic acid represented by the following Chemical Formula 2 and a crosslinking agent, It is obtained by impregnating an acid. These electrolytes exhibit different physical and thermal properties depending on the degree of crosslinking. The electrolyte exhibits both high mechanical strength of polyethylene (meth) acrylic acid and flexibility of polyurethane, and is excellent in ion conductivity.

[Formula 1]

Wherein R is a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C4-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C2-C20 hetero Arylene group,

a is a number from 10 to 500,

B is H ⁺ , NH ₄ ⁺ or an alkali metal such as Li ⁺ , Na ⁺ , or K ⁺ ,

[Formula 2]

Wherein R 'is hydrogen or a methyl group,

m is 70 to 90 mol%, n is 10 to 30 mol%,

b is a number from 50 to 1000.

The weight average molecular weight of the water-dispersed polyurethane of Formula 1 is 5,000 to 500,000 and preferably about 10,000. In addition, the weight average molecular weight of polyethylene (meth) acrylic acid of the formula (2) is 10,000 to 500,000, preferably about 100,000.

Specific examples of the unsubstituted C1-C10 alkylene group in Chemical Formula 1 of the present invention include methylene, ethylene, propylene, isobutylene, sec-butylene, pentylene, iso-amylene, hexylene, and the like. At least one hydrogen atom of the alkylene may be a halogen atom, a hydroxy group, a nitro group, a cyano group, an amino group, an amidino group, a hydrazine, a hydrazone, a carboxyl group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid or a salt thereof, or C1 -C6 alkyl group, C2-C6 alkenyl group, C2-C6 alkynyl group, C1-C6 heteroalkyl group, C2-C6 aryl group, C6-C20 arylalkyl group, C6-C20 heteroaryl group, or C6-C20 It may be substituted with a heteroarylalkyl group.

The arylene group used alone or in combination refers to a divalent carbocycle aromatic system comprising one or more rings, which rings can be attached or fused together in a pendant manner. The term arylene includes aromatic radicals such as phenylene, naphthylene, tetrahydronaphthylene. The arylene group may have substituents such as haloalkylene, nitro, cyano, alkoxy and lower alkylamino. At least one hydrogen atom in the arylene group may be substituted with the same substituent as in the alkyl group described above.

The heteroarylene group includes 1, 2 or 3 heteroatoms selected from N, O, P or S, and the remaining ring atoms refer to a divalent monocyclic or bicyclic aromatic organic compound. At least one hydrogen atom of the hetero atoms may be substituted with the same substituent as in the alkyl group described above.

The cycloalkylene group refers to a group such as a hexylene group and the like, and at least one hydrogen atom of the cycloalkylene group described above may be substituted with the same substituent as in the alkyl group described above.

Specific examples of the polyurethane compound of Formula 1 include Primacor 5980 (Dow Chemical). Or dimethylol butanoic acid, dimethylol propionic acid, poly (tetramethylene ether glycol) poly (tetramethylene ether glycol) (PTMEG), poly (propylene glycol) (polyG) And various mixtures such as polycaprolactone diol (PCL).

As a specific example of the polyethylene (meth) acrylic acid, there is polyethylene acrylic acid in which R ′ is hydrogen in formula (2).

As the crosslinking agent, an aziridine-based compound is used, and as a specific example thereof

Modified diisocyanates such as isophorone diisocyanate and diepoxide compounds.

In the proton conductive electrolyte of the present invention, an oxazoline-based compound may be further added, if necessary, in addition to the aziridine-based compound. As such, further addition of an oxazoline-based compound can obtain the advantage of having high mechanical strength and high stability at high temperature, and thus more preferable.

An example of the oxazoline-based compound is EPOCROS (Nippon Shokubai).

Looking at the manufacturing method of the above-described proton conductive electrolyte is as follows.

First, a base is added to polyethylene (meth) acrylic acid of Formula 2 to make a corresponding salt to be dissolved in water. The base is not particularly limited, and examples thereof include ammonia water, triethylamine (TEA), tributylamine, sodium hydroxide (NaOH), potassium hydroxide (KOH), lithium hydroxide (LiOH), and the like. 30 to 100 parts by weight based on 100 parts by weight of polyethylene (meth) acrylic acid. If the content of the base is less than 30 parts by weight, polyethylene (meth) acrylic acid is not dissolved, which is not preferable.

To the salt of polyethylene (meth) acrylic acid, a polyurethane-based compound of formula (1) and a solvent are added and mixed.

The content of the polyethylene (meth) acrylic acid is 30 to 65 parts by weight based on 100 parts by weight of the polyurethane-based compound of Formula 1. If the content of polyethylene (meth) acrylic acid is less than 30 parts by weight, the mechanical strength is low and the phenomenon of dissolving in phosphoric acid at a high temperature occurs, and if it exceeds 65 parts by weight, a small amount of phosphoric acid is impregnated to lower the conductivity, which is not preferable. . And the content of the aziridine-based compound of the crosslinking agent is 10 to 30 parts by weight based on 100 parts by weight of the polyurethane-based compound of formula (1). If the content of the aziridine-based compound is less than 10 parts by weight, the mechanical properties are lowered. If the content of the aziridine compound is more than 30 parts by weight, the ion conductivity is lowered, which is not preferable.

If necessary, an oxazoline compound may be further added to the mixture, wherein the content of the oxazoline compound is 5 to 30 parts by weight based on 100 parts by weight of the polyurethane compound of Chemical Formula 1. If the content of the oxazoline-based compound is less than 5 parts by weight, the addition effect is insignificant, and if it exceeds 30 parts by weight, the impregnated amount of phosphoric acid is lowered due to the tendency of the polymer membrane to be brittle, thereby lowering the ion conductivity, which is not preferable.

An example of the solvent is water (deionized water), the content of which is adjusted so that the solid content of water is 18 to 30% by weight.

The mixture is cast and dried at 80 to 120 ° C. to carry out a polymerization (crosslinking) reaction. If the polymerization temperature is less than 80 ° C, the polymerization reactivity is lowered, and if it exceeds 120 ℃ crosslinking proceeds excessively by an excessive reaction is not preferable. And the polymerization reaction time varies depending on the polymerization temperature, but is carried out at 120 ℃ 2 hours to less than 100 ℃ for 4 hours.

As described above, when the polymerization is completed, an acid is impregnated therein to complete the proton conductive electrolyte.

As a non-limiting example of the acid, phosphoric acid or the like is used, and a higher amount thereof is advantageous in terms of ionic conductivity, but according to one embodiment, 150 to 500 weight based on 100 parts by weight of the polyurethane compound of Formula 1 Use wealth

The concentration of the phosphoric acid is not particularly limited, but an aqueous solution of 80 to 100% by weight, in particular 85% by weight, of phosphoric acid is used.

The temperature at the time of impregnation of the acid is preferably carried out at a high temperature (80 ℃) for 1 to 4 hours, especially 2 hours.

The proton conductive electrolyte obtained according to the above process consists of a polymerization reaction between the polyurethane-based compound of Formula 1, polyethylene (meth) acrylic acid of Formula 2, and an aziridine-based compound as a crosslinking agent. If the oxazoline-based compound is added during the preparation process, the proton conductive electrolyte is composed of a result of polymerization of the polyurethane-based compound of Formula 1, polyethylene (meth) acrylic acid, aziridine-based compound, and oxazoline-based compound of Formula 2.

The proton conductive electrolyte obtained according to the above procedure has a film thickness of 40 to 80 mu m.

The fuel cell of the present invention is a fuel cell using the proton conductive electrolyte obtained according to the above process as an electrolyte membrane. The electrolyte membrane is formed into a polymer fuel cell using a unit cell in which an oxidant distribution plate having an oxidant flow path formed between the oxygen electrode and the fuel electrode is formed at the oxygen electrode side, and a fuel distribution plate having the fuel flow path formed at the fuel electrode side.

In this way, even when the operating temperature is 100 to 300 ° C., even when no humidification or relative humidity is 50% or less, a solid polymer fuel cell exhibiting stable power generation performance (durability) for a long time can be obtained. It is useful as a fuel cell.

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

Example 1: When the weight ratio of polyethylene acrylic acid (PEAA), polyurethane and aridine-based compound is 0.5: 0.5: 0.2

30 parts by weight of a water dispersible polyurethane, 10 parts by weight of an aziridine compound and 20 parts by weight of EPOCROS (Nippon Shokubai) were blended into a result obtained by adding 100% ammonia water to 40 parts by weight of PEAA (trade name: Primacor 5980: Dow Chemical). Deionized water, which is a solvent, was added thereto and stirred.

The mixture was cast and dried at 120 ° C. for about 4 hours to form a film about 100 μm thick. The membrane was impregnated with 85% phosphoric acid at room temperature for 2 hours to produce a proton conductive electrolyte.

Example 2

A proton conductive electrolyte was prepared in the same manner as in Example 1 except that the weight ratio between PEAA, polyurethane, and an aridine compound was changed to 0.67: 0.47: 0.35.

Example 3

A proton conductive electrolyte was prepared in the same manner as in Example 1 except that the weight ratio between PEAA, polyurethane, and an aridine compound was changed to 0.58: 0.63: 0.27.

The change in conductivity over time of the proton conductive electrolyte membrane of Example 1 was investigated and is shown in FIG. 1. 1 shows a proton conductive electrolyte membrane (-◆-) obtained by impregnating water in a Nafion membrane for comparison with the case of Example 1, and a proton conductive electrolyte membrane (-■-) obtained by impregnating a carbonate in a Nafion membrane. And a case of the proton conductive electrolyte membrane (-Δ-) obtained by impregnating propylene carbonate (PC) on the Nafion membrane.

Referring to FIG. 1, as a result of a comparative experiment between a Nafion-H ₂ O system applied to a conventional PEMFC, a system using a Nafion-organic solvent (high boiling point organic solvent) and the proton conductive electrolyte membrane of Example 1 as an electrolyte , The proton conductive electrolyte membrane of Example 1 was found to have excellent conductivity characteristics at high temperatures.

Example 4

The solid polymer electrolyte membrane of Example 1 was sandwiched with a commercially available fuel cell electrode (Electrochemist) to form a membrane electrode assembly, and the fuel cell was operated with hydrogen / air under 110 ° C to 150 ° C and no humidification conditions. The electrode area was 3 cm 3 cm = 9 cm ² , and the gas supply amount was 100 ccm for hydrogen and 300 ccm for air.

Example 5-6

The operation was carried out in the same manner as in Example 4 except that the temperature was changed to 130 ° C. and 150 ° C. during the operation.

Figure 2 shows the current-voltage characteristics of the initial power generation, from which the fuel cell according to the fourth embodiment of the present invention is capable of operating at high temperatures, particularly in the same conditions showed better results than in the case of Nafion, It showed properties comparable to polybenzimidazole (PBI).

The proton conductive electrolyte of the present invention is less expensive to manufacture than conventional polybenzimidazole and Nafion, and is easy to manufacture a film by applying a solvent casting method, and also easy to control the thickness. In addition, it is a polymer electrolyte membrane having high mechanical strength and flexibility, and having greatly improved ion conductivity.

By using the above-described proton conductive electrolyte, a fuel cell capable of operating under conditions of high temperature and no humidification of 100 ° C. or higher and having improved power generation performance can be manufactured.

Claims (19)

A proton conductive electrolyte comprising a polymerization product of a polyurethane-based compound represented by the following formula (1), a polyethylene (meth) acrylic acid represented by the following formula (2), and a crosslinking agent.  [Formula 1]

Wherein R is a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C4-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C2-C20 hetero Arylene group, a is a number from 10 to 500, B is H ⁺ , NH ₄ ⁺ , or an alkali metal ion, [Formula 2]

Wherein R 'is hydrogen or a methyl group, m is 70 to 90 mol%, n is 10 to 30 mol%, b is a number from 50 to 1000. The proton conductive electrolyte according to claim 1, wherein the crosslinking agent is an aziridine compound. The proton conductive electrolyte according to claim 2, wherein the aziridine-based compound is selected from a modified diisocyanate and a diepoxide compound. The proton conductive electrolyte of claim 1, further comprising an oxazoline compound. The proton conductive electrolyte according to claim 4, wherein the content of the oxazoline-based compound is 5 to 30 parts by weight based on 100 parts by weight of the polyurethane-based compound of Formula 1. According to claim 1, Proton conductive electrolyte, characterized in that the content of polyethylene (meth) acrylic acid represented by the formula (2) is 30 to 65 parts by weight based on 100 parts by weight of the polyurethane-based compound of formula (1). The proton conductive electrolyte of claim 1, further comprising an acid. The proton conductive electrolyte according to claim 7, wherein the acid is phosphoric acid, and the acid content is 150 to 500 parts by weight based on 100 parts by weight of the polyurethane compound of Formula 1. Adding a base to polyethylene acrylic acid (PEAA) represented by Formula 2 to obtain a corresponding salt; Adding a polyurethane compound, a crosslinking agent, and a solvent represented by Formula 1 to the salt to obtain a mixture; And A method for producing a proton conductive electrolyte, comprising the step of preparing the proton conductive electrolyte of any one of claims 1 to 8 by performing a polymerization reaction of the mixture. [Formula 1]

Wherein R is a substituted or unsubstituted C1-C6 alkylene group, a substituted or unsubstituted C4-C20 cycloalkylene group, a substituted or unsubstituted C6-C20 arylene group, or a substituted or unsubstituted C2-C20 hetero Arylene group, a is a number from 10 to 500, B is H ⁺ , NH ₄ ⁺ or an alkali metal ion, [Formula 2]

Wherein R 'is hydrogen or a methyl group, m is 70 to 90 mol%, n is 10 to 30 mol%, b is a number from 50 to 1000. 10. The method of claim 9, further comprising the step of impregnating an acid to the result of the polymerization reaction. The method of claim 10, wherein the acid is phosphoric acid. The method for producing a proton conductive electrolyte according to claim 9, wherein the polymerization reaction is performed at 80 to 120 ° C. The proton of claim 9, wherein the base is at least one selected from ammonia water, triethylamine (TEA), tributylamine, sodium hydroxide (NaOH), potassium hydroxide (KOH) and lithium hydroxide (LiOH)). Method for producing a conductive electrolyte. The method of claim 9, wherein the polymerization reaction of the mixture, Casting the mixture, it is made through the process of drying at 80 to 120 ℃ proton conductive electrolyte production method characterized in that. The method for producing a proton conductive electrolyte according to claim 9, wherein the crosslinking agent is an aziridine compound. The compound of claim 15, wherein the aziridine-based compound is selected from modified diisocyanates and diepoxide compounds, The content of the aziridine-based compound is a method for producing a proton conductive electrolyte, characterized in that 10 to 30 parts by weight based on 100 parts by weight of the polyurethane-based compound of formula (1). 10. The method of claim 9, wherein an oxazoline compound is further added to the mixture. 18. The method of claim 17, wherein the content of the oxazoline-based compound is 5 to 30 parts by weight based on 100 parts by weight of the polyurethane compound of Formula 1. A fuel field comprising the proton conductive electrolyte of claim 1. G.

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