KR101138871B1 - Polymer electrolyte membrane, manufacturing method thereof, and fuel cell employing the same - Google Patents

Abstract

A polymer electrolyte membrane which is stable under high temperature and no humidification conditions and has a high proton conductivity, can be produced such a polymer electrolyte membrane, and has a high power generation characteristic by using a method for producing a polymer electrolyte membrane having high productivity and using such a polymer electrolyte. Provide a fuel cell. The polymer is produced by wet film formation of a mixed solution obtained by dissolving a (hydrocarbon-based) polymer electrolyte having an acidic functional group and a free acid source composed of any one of free acid, a mixture of free acid and Lewis base, or a mixture of free acid and organic salt in a polar organic solvent. A method for producing a polymer electrolyte membrane is obtained which obtains a polymer electrolyte membrane doped with free acid in an electrolyte.

Description

Polymer electrolyte membrane, manufacturing method and fuel cell employing the same {Polymer electrolyte membrane, manufacturing method according, and fuel cell employing the same}

Disclosed are a method for producing a polymer electrolyte membrane, a polymer electrolyte membrane, and a fuel cell.

In fuel cells, which are applicable to electrochemical devices and are particularly drawing attention as the next generation of clean energy, the development of electrolyte membranes capable of conducting protons under unhumided or low-humidity, which makes it possible to operate at high temperatures of 100 ° C. or higher recently, has been actively conducted. ought. In this way, when an electrolyte membrane capable of proton conduction at a high temperature that does not depend on water is provided, it can be expected to be used as a home cogeneration or an automobile for use in simplifying a fuel cell system.

As a very suitable for home cogeneration or automotive use, there is a polymer polymer fuel cell (PEFC), PEFC is a polymer electrolyte membrane having a proton conductivity is composed of a catalyst and a gas diffusion layer It has a membrane electrode assembly (MEA: Membrane Electrode Assembly) interposed by a fuel electrode and an oxygen electrode, and by supplying hydrogen gas to the fuel electrode and air or oxygen to the oxygen electrode, an electrochemical reaction of the following equation takes place and thus electromotive force is generated. It is a structure to get.

(Fuel ^{_{electrode) H 2 → 2H + + 2e}} -

(Oxygen _{^{Electrode) 2H + + 1 / 2O 2}} + 2e - → H 2 O

As for the polymer electrolyte membrane having the above-mentioned proton conductivity, Nafion (registered trademark), sulfonated polyether ether ketone, etc., manufactured by DuPont, USA, have been known. Proton conduction of such a polymer electrolyte is generally applied to fuel cells in a constant wet state by humidification or the like because water molecules around sulfonic acid are interposed in conduction. Therefore, the operating temperature is generally 80 ° C. or lower, and this limitation causes problems such as carbon monoxide poisoning of the catalyst. Therefore, selective carbon monoxide removal is required, which makes fuel cell systems more complicated and expensive. Situation.

In view of such a problem, various proposals regarding the PEFC which drive at 100 degreeC or more are made | formed. In general, in the power generation above 100 ° C, it is suggested that the degree of poisoning by carbon monoxide can be reduced by improving the catalytic activity, and furthermore, the fuel cell life is improved. However, a fuel cell using an electrolyte system that does not depend on a water medium has been proposed, focusing on polybenzimidazole doped with phosphoric acid because water molecules cannot be stably present in an operation in a medium temperature region of about 150 ° C. See, for example, US Pat. No. 55,25436 specifications). In such a fuel cell, power generation is possible even in a medium temperature region of about 150 ° C.

In addition to the technique described in US Patent No. 5525436, the fuel cell using a molten salt at room temperature as a proton transfer medium is devised. As such a fuel cell, for example, a method of immobilizing a room temperature molten salt is a liquid, centering on the invention of using a common room temperature molten salt as a proton transfer medium (for example, refer to International Publication No. 03/083981). As a combination with polyarylene (see, for example, Japanese Patent Application Laid-Open No. 2006-32213), a combination with polybenzimidazoles, etc. (see, for example, Japanese Patent Application Laid-Open No. 2005-166598), Zwitter Combinations with ion-type molten salts and acids (see, for example, Japanese Patent Application Laid-Open No. 2005-228588 and Japanese Patent Application Laid-Open No. 2004-38683), and the like have been studied. There was a problem in that the polarization characteristic in the characteristic identification was very low. For example, although the polarization curve is shown in the document (International Publication No. 03/083981), the data which is continuously developed is not shown, and the data which can be developed in the document (Japanese Patent Laid-Open No. 2006-32213) are Not shown. In addition, although the document (Japanese Patent Laid-Open No. 2005-228588) and the document (Japanese Patent Laid-Open No. 2004-38683) describe the results of the continuous energization test as the result of the electrochemical measurement, the characteristics are very low.

On the other hand, a technique in which phosphoric acid is doped into a perfluorosulfonic acid polymer electrolyte represented by conventional Nafion (registered trademark) (for example, R. Savinell et al., J. Electrochem. Soc. 141, (1994) L46 Electrolytics doped with common molten salt (see, eg, J. Sun et al., Electrochemica Acta, 46, (2001) 1703-1708) or strong acids with triazoles doped with sulfonated polysulfones. The presence or absence of proton transfer is also confirmed in the combination of weak bases (see, for example, Japanese Patent Laid-Open No. 2006-32213), but the power generation characteristics are not sufficiently mentioned, and the technique is not practically used for fuel cells. In this case, it is a fact that sufficient verification is not performed.

However, as shown in the literature (R. Savinell et al., J. Electrochem. Soc. 141, (1994) L46), in the case of using an acidic proton medium such as phosphoric acid, As shown in benzimidazole, it is thought that the transfer of protons necessary for power generation can be achieved relatively easily, so that power generation is possible.

However, as described in R. Savinell et al., J. Electrochem. Soc. 141, (1994) L46, a method of doping phosphoric acid after wet film formation of a polymer electrolyte membrane in a solution in which the polymer electrolyte is dissolved is generally used. However, there are problems such as a large change in the physical properties of the film before and after the dope, and a long time required to dope the amount of phosphoric acid until equilibrium. In addition, when considering a continuous process of directly forming a polymer electrolyte membrane by using a polymer electrolyte doped with phosphoric acid, a container for doping phosphoric acid and a supporting roll for supporting the polymer electrolyte membrane should be made of an acid resistant material. In order to increase the productivity of the membrane, various problems must be solved.

On the other hand, as disclosed in the literature (Atsuo Muneuchi et al., Fuel cell Vol. 7 No. 2 (2007) 86), the membrane using a polymer electrolyte membrane doped with phosphoric acid in the synthesis of the monomer constituting the polymer electrolyte A technique for continuously carrying out the steps up to manufacturing an electrode assembly (Membrane-Electrode Assembly, MEA) has been proposed.

However, in this method, it is expected that a large scale acid-resistant facility is required, and that conditions such as hydrolysis of polyphosphoric acid as a solvent need to be set by trial and error.

In addition, as a polymer electrolyte capable of operating a fuel cell at 100 ° C. or higher without humidification, a molten salt or the like has been examined in addition to the polymer electrolyte membrane doped with phosphoric acid as described above (see, for example, Hongjun Chen, et al. ., Electrochem. Comm., 9 (2007) 469), a phenomenon in which sufficient power generation characteristics cannot be obtained.

As a method of using the above-described molten salt or the like as a proton transfer medium, a method of polymerizing monomers in the molten salt (for example, Kamimura Toshiaki et al., 47th Battery Discussion Society (2006) 178) Or a method of wet-forming a solution made compatible with a polymer electrolyte in a solution state (see, for example, Kim Je-Duk et al., 47th Korean Society for Battery Discussion (2006) 176). The method of obtaining such a self-supporting film is generally considered to be higher in productivity than the method of doping phosphoric acid in a polymer electrolyte membrane. However, in the characteristic of the electrolyte membrane itself, the necessity of investigating or developing additional proton conduction mechanisms is required to obtain practical power generation characteristics.

In this way, any acid-doped electrolyte or a molten salt-type electrolyte has sufficient proton conductivity and power generation characteristics under high humidity and no humidification conditions, for example, 100 ° C. or higher, and high productivity in the production of acid-doped electrolyte membranes. How to have not been proposed yet.

Therefore, the present invention has been made in view of the above problems,

A polymer electrolyte membrane which is stable under high temperature and no humidification conditions and has a high proton conductivity, can be produced such a polymer electrolyte membrane, a method for producing a polymer electrolyte membrane with high productivity, and a fuel cell having high power generation characteristics by using such a polymer electrolyte. It aims to provide.

The present inventors have conducted extensive research to solve the above problems, and as a result, a predetermined polymer electrolyte having an acidic functional group can be used in a free acid such as phosphoric acid and a polar organic solvent, thereby forming an acid-doped polymer electrolyte membrane. It discovered that it could form into a film by wet film forming, and came to complete this invention based on this discovery.

That is, according to one embodiment of the present invention, a free acid source composed of any one of a (hydrocarbon based) polymer electrolyte having an acidic functional group and a mixture of free acid, free acid and Lewis base, or a mixture of free acid and organic salt is added to the polar organic solvent. There is provided a method for producing a polymer electrolyte membrane in which the mixed solution dissolved is wet formed to obtain a polymer electrolyte membrane doped with the free acid in the polymer electrolyte.

Here, in the manufacturing method of the polymer electrolyte membrane, the main skeleton of the polymer electrolyte is preferably an aromatic engineering plastic. As said aromatic engineering plastics, polyether sulfone or polybenzimidazole is mentioned, for example.

In the method for producing the polymer electrolyte membrane, the free acid is preferably an acidic inorganic phosphorus compound or an acidic organic phosphorus compound. As said acidic inorganic phosphorus compound, phosphoric acid, polyphosphoric acid, or phosphonic acid is mentioned, for example, As said acidic organic phosphorus compound, vinylphosphonic acid or ethylphosphonic acid is mentioned, for example.

In the method for producing the polymer electrolyte membrane, the organic salt is preferably a quaternary ammonium cation.

In the method for producing the polymer electrolyte membrane, the polar organic solvent is preferably an amide organic solvent.

Examples of the amide organic solvents include dimethylacetamide, N-methyl-2-pyrrolidone or dimethylformamide.

Further, in the method for producing the polymer electrolyte membrane, the number of moles (nA) of the acidic functional groups of the polymer electrolyte, the number of moles of the free acid (nB) and the number of moles of the Lewis base (nC) satisfy the relationship of nA + nB> nC. It is desirable to.

In the method for producing the polymer electrolyte membrane, it is preferable to dissolve 20 to 80 parts by weight of the free acid based on 100 parts by weight of the polymer electrolyte in the polar solvent.

In the method for producing a polymer electrolyte membrane, the free acid is vinyl phosphonic acid, and after the wet film formation, the vinyl phosphonic acid doped in the polymer electrolyte may be polymerized. In this case, the mixed solution in which the polyfunctional polymerizable compound is dissolved in the polar organic solvent may be wet formed, and after the wet film formation, the polyfunctional polymerizable compound and the vinylphosphonic acid may be copolymerized. As said polyfunctional polymerizable compound, a polyfunctional vinyl compound, a diacrylate, or a dimethacrylate is mentioned, for example.

In order to solve the above problems, according to another embodiment of the present invention, a polymer electrolyte membrane doped with a free acid consisting of an acidic inorganic phosphorus compound or an acidic organic phosphorus compound is provided with an aromatic engineering plastic having an acidic functional group as a main skeleton do.

Here, in the polymer electrolyte membrane, examples of the aromatic engineering plastics include polyether sulfone or polybenzimidazole.

Further, in the polymer electrolyte membrane, examples of the acidic inorganic phosphorus compound include phosphoric acid, polyphosphoric acid, or phosphonic acid. Examples of the acidic organic phosphorus compound include vinylphosphonic acid or ethylphosphonic acid. Can be.

In order to solve the above problems, according to another embodiment of the present invention, there is provided a fuel cell having a membrane electrode assembly using the above-described polymer electrolyte membrane.

According to one embodiment of the present invention, a predetermined polymer electrolyte having an acidic functional group and a free acid such as phosphoric acid are mixed with a polar organic solvent, and an acid-doped polymer electrolyte membrane is formed by a wet membrane to form a high temperature and no humidification condition. It is possible to provide a polymer electrolyte membrane having a high proton conductivity, which is stable even under such conditions, a polymer electrolyte membrane can be produced, a method of producing a polymer electrolyte membrane having high productivity, and a fuel cell having high power generation characteristics by using such a polymer electrolyte. Done.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated in detail with reference to an accompanying drawing.

(Production of Acid Doped Polymer Electrolyte Membrane by Wet Film Production)

First, before describing this invention, the knowledge acquired when this inventors completed this invention is demonstrated.

<About the phenomenon>

As described above, conventionally, a polymer electrolyte membrane doped with an acid such as phosphoric acid cannot be directly obtained by a wet preparation membrane. For this reason, although it is not disclosed in the literature etc. for general knowledge, generally, the polymeric material which can dope or hold acid, such as phosphoric acid, is described by Z. Zhou et al., J. Am. Chem. Soc. 127, ( 2005) 10825) and the polymer structure described in (Y. Aihara et al., ECS Trans., 3 (2006) 123), the structure containing a nitrogen-containing compound in the polymer backbone. In the polymer material, when the polymer itself has a basic property, the acid doped to the basic polymer (for example, polybenzimidazole: PBI) shows an interaction, and the acid is stably formed to form a salt structure. I think it can be maintained. Therefore, even if the polymer itself is dissolved in a solvent at the time of wet film formation, when acid is mixed with the polymer solution in which the polymer is dissolved in the solvent, when the polymer is basic, the acid-based complex is immediately impregnated with the acid mixed with the base in the polymer solution. Form. Since this acid group complex is insoluble in a solvent, precipitation arises in a solution. In addition, the acid group-based composites are poor in moldability, and it is very difficult to form the composites themselves into a film.

On the other hand, it is known that complexation of phosphoric acid and a polymer has been considered relatively long ago. For example, in G. Zukowska et al., Solid State Ionics, 119 (1999) 289 or in G. Zukowska et al., Chem. Mater, 12 (2000) 3578, NN-dimethylformamide Disclosed is a technique capable of forming an electrolyte by using polyvinylidene fluoride or polyglycidyl methacrylate as a polymer skeleton, referred to as a gel of (DMF) and phosphoric acid, and providing a proton conductor. Such electrolytes include the material compositions disclosed in G. Zukowska et al., Solid State Ionics, 119 (1999) 289 or G. Zukowska et al., Chem. Mater, 12 (2000) 3578; As apparent from the range of the evaluation temperature, it is not an electrolyte that can withstand high temperatures.

In addition, since the polymer structure of the electrolyte is not all a structure including a basic unit, it is possible to use the polymer electrolyte and the acid in the solvent. However, the role of polymers in the techniques of G. Zukowska et al., Solid State Ionics, 119 (1999) 289 and G. Zukowska et al., Chem. Mater, 12 (2000) 3578, Using only a macromolecular skeleton such as polyvinylidene fluoride or polyglycidyl methacrylate, the gel of DMF and phosphoric acid is retained, and the power generation characteristics when used in a fuel cell have not been studied at all.

As described above, in any acid-doped polymer electrolyte membrane, it has a high productivity that a polymer electrolyte membrane can be directly obtained from a solution in which the polymer electrolyte is dissolved by a wet film formation, and the obtained polymer electrolyte membrane is stable under conditions of high temperature and no humidification. It is not proposed to have high proton conductivity. In addition, it has not been proposed that a fuel cell using such an acid-doped polymer electrolyte membrane is stable under high temperature and no humidification conditions and has excellent power generation characteristics.

For this phenomenon, the present inventors explain the examination of a method for directly obtaining a polymer electrolyte which is stable under high temperature and no humidification conditions and has a high proton conductivity by wet film formation.

<Review on Fabrication Conditions of Polymer Electrolyte Membrane>

First, the experiment which investigated the solubility to basic polar organic solvent using polyphosphoric acid as an example of the acid doped to a polymer electrolyte is demonstrated. In this experiment, N-methyl-2-pyrrolidone (hereinafter referred to as "NMP"), dimethylacetamide (hereinafter referred to as "DMAc"), dimethylformamide (hereinafter referred to as "DMF") Polyphosphoric acid was dissolved in three polar organic solvents. The amount of polyphosphoric acid added to the polar organic solvent was 10% by weight, 20% by weight, 30% by weight, 40% by weight, or 50% by weight. The results are shown in Table 1 below.

In addition, in Table 1 below, (circle) shows soluble (at room temperature (25 degreeC)), (triangle | delta) shows soluble at 60 degreeC, and x is insoluble, respectively.

[Table 1]

NMP DMAc DMF 10 wt% ○ × ○ 20 wt% ○ × ○ 30 wt% △ × △ 40 wt% × × × 50 wt% × × ×

As shown in Table 1, NMP and DMF were able to dissolve polyphosphoric acid up to 20 weight% at room temperature, and were able to dissolve polyphosphoric acid up to 30 weight% at 60 degreeC. On the other hand, DMAc could not be dissolved even in 10% by weight of polyphosphoric acid. This result shows that it is preferable to use NMP and DMF as a polar organic solvent in dissolving polyphosphoric acid.

Next, the experiment which investigated the solubility with respect to a basic polar organic solvent using the polymer which has a sulfonic acid group as an example of the polymer electrolyte which has an acidic functional group is demonstrated. In this experiment, as the polar organic solvent used, three kinds of solvents were used as in the case of polyphosphoric acid, and sulfonated polyether ether ketone was dissolved as one example of a polymer having sulfonic acid groups in each of these polar organic solvents. The amount of the polymer having a sulfonic acid group added to the polar organic solvent was 10% by weight, 20% by weight, 30% by weight, 40% by weight, or 50% by weight. The results are shown in Table 2 below. In Table 1 below, ○ represents soluble and x represents insoluble. In addition, (triangle | delta) is a soluble but very high viscosity and shows a state in which stirring is difficult.

TABLE 2

NMP DMAc DMF 10 wt% ○ ○ ○ 20 wt% ○ ○ ○ 30 wt% △ ○ △ 40 wt% △ △ × 50 wt% × × ×

As shown in Table 2, although NMP is soluble at 10-40 weight%, the viscosity became high at 30-40 weight%. In addition, while DMAc is soluble at 10 to 40% by weight, the viscosity increased at 40% by weight. In addition, DMF was soluble at 10 to 30% by weight, but increased in viscosity at 30% by weight. From this result, it is preferable to use DMAc and NMP as a polar organic solvent in dissolving a polymer electrolyte, and DMAc is especially preferable.

By the way, in order to form a polymer electrolyte membrane directly doped with an acid by wet film formation, both the polymer electrolyte and the acid doped with it need to be dissolved in a polar organic solvent. However, since DMAc cannot dissolve polyphosphoric acid as shown in Table 1 above, it can be said that NMP is the most preferable solvent in order to dissolve both polyphosphoric acid and a polyelectrolyte having a sulfonic acid group.

After obtaining the above examination results, the present inventors further examined, and the knowledge that DMAc which melt | dissolved the polyelectrolyte which has a sulfonic acid group can dissolve polyphosphoric acid can be acquired, and based on this knowledge, the present inventors The present invention has been completed. Hereinafter, a method for producing a polymer electrolyte membrane according to the present invention, a polymer electrolyte membrane obtained by the production method and a fuel cell using the same will be described in detail.

[Production method of polymer electrolyte membrane according to the present invention]

A method for producing a polymer electrolyte membrane according to the present invention is to obtain a polymer electrolyte membrane doped with a free acid in a polymer electrolyte by wet forming a polymer electrolyte having an acidic functional group and a mixed solution in which a free acid source is dissolved in a polar organic solvent. In more detail, the manufacturing method of the polymer electrolyte membrane which concerns on this invention is divided roughly into the following four processes.

(1) Solution manufacturing process

(2) film forming process

(3) predrying process

(4) drying process

(About a solution manufacturing process)

First, the (1) solution manufacturing process is demonstrated. In the solution preparation step, a mixed solution in which a polymer electrolyte having an acidic functional group (for example, a polymer compound having a sulfonic acid group), a free acid (for example, polyphosphoric acid), and the like are dissolved in a polar organic solvent is prepared. This mixed solution is prepared by adding a polymer having an acidic functional group and a free acid to a polar organic solvent and stirring using a mechanical stirrer, a magnetic stirrer, or the like. Of course, the mechanism used for stirring is not limited to a mechanical stirrer or a magnetic stirrer, If another polymer and free acid can be mixed and dissolved in a polar solvent, you may use another mechanism. In addition, since bubbles may be generated by stirring during the preparation of the mixed solution, it is preferable to deflate the mixed solution during stirring by vacuum defoaming, centrifugal defoaming or the like. Below, the raw material used for manufacture of a mixed solution is demonstrated in detail.

<About a polymer electrolyte having an acidic functional group>

The polymer electrolyte having an acidic functional group used in the solution preparation process according to one embodiment of the present invention is not particularly limited, but the compatibility with an acid to be dope in the polymer electrolyte, compatibility with a polar solvent, processability at the time of film forming, heat resistance, etc. In consideration, it is preferable that the main skeleton is an aromatic engineering plastic. The aromatic engineering plastic is not particularly limited as long as it is an engineering plastic having aromatic properties. For example, polyether sulfone, sulfonated polybenzimidazole, sulfonated polyether ether ketone, sulfonated as having an acid functional group as a sulfonic acid group. Polysulfone, sulfonated polyphenylene oxide, sulfonated polysulfone, sulfonated aromatic polyimide, sulfonated aromatic polyamide, sulfonated polycarbonate, sulfonated polyethylene terephthalate, sulfonated polyarylate, sulfonated polyetherimide, etc. Can be mentioned.

Moreover, a phosphoric acid group, a phosphonic acid group, a carboxylic acid group, a sulfonylamide group etc. are mentioned besides the said sulfonic acid group as an acidic functional group, Especially a sulfonic acid group, a phosphoric acid group, and a phosphonic acid group are preferable.

<About Yuriyama Garden>

In this invention, a "free acid source" means what consists of any one of a free acid, a mixture of a free acid, and a Lewis base, or a mixture of a free acid and an organic salt. The free acid used in the present invention is not particularly limited, and various acids such as phosphoric acid, phosphonic acid, phosphinic acid, sulfuric acid, methylsulfonic acid, trifluoromethylsulfonic acid, and trifluoromethanesulfonylamidesulfonic acid may be mentioned. Especially, it is preferable that it is an acidic inorganic phosphorus compound or an acidic organic phosphorus compound from a thermal stability viewpoint. As such an acidic inorganic phosphorus compound, phosphoric acid, polyphosphoric acid, phosphonic acid, phosphinic acid, etc. are mentioned, For example, phosphoric acid, polyphosphoric acid, or phosphonic acid is especially preferable.

Moreover, as an acidic organophosphorus compound, it is represented by alkyl phosphonic acid or methyl phosphate ester, ethyl phosphate ester, butyl phosphate ester, etc. which are represented, for example by allyl phosphonic acid, methyl phosphonic acid, ethyl phosphonic acid, etc. which are represented by vinyl phosphonic acid. The acidic phosphoric acid ester etc. which are mentioned are mentioned, Among these, vinyl phosphonic acid or ethyl phosphonic acid is especially preferable.

In addition, in the present invention, as the Lewis base which can be used in admixture with the free acid, for example, an azole compound such as imidazole, triazole, benzimidazole, benzotriazole, pyridine, pyridazine, pyrimidine, pyridazine, Nitrogen-containing heterohexacyclic compounds such as triazine, nitrogen-containing condensed polycyclic heterocyclic compounds such as quinoline, quinoxaline, indole, and phenazine, and nucleic acid bases such as purine, uracil, thymine, cytosine, and adeninguanine Can be mentioned.

In addition, in this invention, the organic salt which can be mixed and used with a free acid is a neutral salt which consists of an organic compound cation and an oxo acid anion. The organic compound cation is usually a cation of a heterocyclic compound, especially a cation of a 3 to 6 membered heterocyclic compound containing 1 to 5 hetero atoms, particularly 3 to 6 containing 1 to 5 nitrogen atoms as a hetero atom. Cations of the ring compound, and the like, and among these, imidazolium cation, pyrrolidinium cation, piperidinium cation, pyridinium cation and the like are preferable. Moreover, a linear quaternary ammonium cation, quaternary phosphonium cation, etc. can also be used.

Among the above cations, imidazolium cation and linear quaternary ammonium cation are particularly preferable, and among these cations, 1,3-substituted imidazolium cation and imidazolium cation represented by the following general formula (1) are preferable.

[Formula 1]

In Formula 1, R ₁ is an alkyl group having 1 to 6 carbon atoms, R ₂ is an alkyl group having 1 to 30 carbon atoms. R ₂ is more preferably 1 to 25 carbon atoms, still more preferably 1 to 20 carbon atoms, and most preferably an alkyl group having 1 to 16 carbon atoms.

Examples of the imidazolium cation represented by the general formula (1) include 1,3-dimethylimidazolium cation, 1-ethyl-3-methylimidazolium cation, 1-methyl-3-propylimidazolium cation, and 1-. Butyl-3-methylimidazolium cation, 1-methyl-3-pentylimidazolium cation, 1-hexyl-3-methylimidazolium cation, 1-heptyl-3-methylimidazolium cation, 1-methyl- 3-octylimidazolium cation, 1-decyl-3-methylimidazolium cation, 1-dodecyl-3-methylimidazolium cation, 1-ethyl-3-propylimidazolium cation, 1-butyl-3 -Ethyl imidazolium cation, etc. are mentioned.

Namely, as the organic salt in the present invention, for example, 1,3-dimethylimidazolium dihydrogen phosphite (DMIP), 1-butyl-3-methylimidazolium dihydrogen phosphite (BMIP), 1 Hexyl-3-methylimidazolium dihydrogen phosphite (HMIP), 1-methyl-3-octylimidazolium dihydrogen phosphite (MOIP), 1-dodecyl-3-methylimidazolium dihydro Rosen phosphite (C12MIP), 1-hexadecyl-3-methylimidazolium dihydrogen phosphite (C16MIP), 1-dodecyl-3-methylimidazolium hydrogensulfite (C12MIS), etc. are mentioned. .

<About polar organic solvent>

As the polar organic solvent used in the solution preparation process according to the embodiment of the present invention, considering the compatibility between the polymer electrolyte having an acidic functional group and the acid doped therein, for example, the amide organic solvent is a nitrogen-containing compound. desirable. As such an amide organic solvent, for example, formamide, N-methylformamide, N, N-dimethylformamide, N-methylacetamide, N, N-dimethylacetamide, N-methylpropioamide, 2- Pyrrolidinone, N-methylpyrrolidone, etc. are mentioned, Especially, a dimethylacetamide, N-methyl- 2-pyrrolidone, or a dimethylformamide is preferable.

<About the amount of Lewis base mixed>

When a mixture of the polymer electrolyte and the free acid and the Lewis base is added to the polar organic solvent, the number of moles of acidic functional groups (nA), the number of moles of free acid (nB) and the number of moles of Lewis base (nC) are nA + nB. It is desirable to satisfy the relationship of> nC. This is to produce a proton that becomes a carrier of charge by shifting the pH of the mixed solution toward the acidic side.

<The mixing ratio of polymer electrolyte and free acid>

In addition, in the solution preparation process according to an embodiment of the present invention, the mixing ratio of the polymer electrolyte and the free acid dissolved in the polar solvent is preferably 20 to 80 parts by weight based on 100 parts by weight of the polymer electrolyte. The reason for this blending ratio is defined based on the examples described later, and therefore, the examples will be described.

(About a film forming process)

Next, (2) the film forming step will be described.

In the film forming step, the polymer electrolyte membrane doped with the free acid is directly formed by wet film forming using the mixed solution prepared in the solution manufacturing step. More specifically, in the film forming process according to an embodiment of the present invention, the polymer electrolyte membrane is formed by casting the mixed solution prepared in the solution manufacturing process on the substrate using a known coating method. As a coating method, the method of casting to a base material using a die coater, a comma coater (trademark), a doctor blade, an application roll, etc. is mentioned, for example. As the base material for casting the mixed solution, for example, PET (poly (ethylene terephthalate)), polyimide (glass), or the like can be used.

(About a predrying process)

Next, (3) a predrying process is demonstrated. In the preliminary drying step, the polymer electrolyte membrane cast on the substrate in the film forming step is at least 10 minutes (if no blower), preferably at least 20 minutes, more preferably at 40 to 80 ° C, preferably at about 60 ° C. Allow to dry for about a minute. This preliminary drying step is intended to form the surface of the polymer electrolyte membrane and to remove the residue of the polar organic solvent contained in the polymer electrolyte membrane. According to a study conducted by the inventors (see Examples described later), when the hot plate is used as a drying means and in a non-blowing state without a blower, preliminary drying is performed at 60 ° C. for about 10 minutes to form a film surface. If it is carried out for about minutes, the film can be peeled off on the substrate, and if it is carried out for about 40 minutes, it becomes possible to volatilize at least 80% by weight of the polar organic solvent. Here, if the drying temperature is too high, preliminary drying is too fast, it is not preferable because the surface formation proceeds first, so that the solvent in the bulk does not easily fall out to cause defects or wrinkles or stress relaxation. On the contrary, if the drying temperature is too low, it takes time for drying and the productivity is remarkably lowered. For this reason, in the present invention, the conditions of the pre-drying step are defined at 40 to 80 ° C. (preferably around 60 ° C.) for at least 10 minutes or more (when there is no blower), preferably for 20 minutes or more, preferably for about 40 minutes. It was.

(About drying process)

Next, (4) a drying process is demonstrated. In the drying step (hereinafter sometimes referred to as "main drying"), the polymer electrolyte membrane having the membrane surface formed in the predrying step is at least 20 minutes at 110 ° C to 150 ° C (preferably 130 ° C or less) (when there is no blower). ) To dry. This drying process aims at removing the water | moisture content and polar organic solvent contained in a polymer electrolyte membrane. According to a study conducted by the inventors (see Examples described later), when the oven is used as a drying means, and in a non-blowing state without a blower, drying is performed at 110 ° C. to 150 ° C. for 20 minutes or more, it is included in the polymer electrolyte membrane. Moisture or polar organic solvent is volatilized and it becomes possible to dry sufficiently. From these results, in this invention, the conditions of a drying process were prescribed | regulated at least 20 minutes at 110 degreeC-150 degreeC.

(About an effect)

After the film-shaped polymer electrolyte membrane is formed, the process of doping the free acid into the membrane is conventionally a batch process, and since the polymer electrolyte membrane absorbs a large amount of free acid, there is a problem that the acid is liberated on the surface of the electrolyte membrane. . In addition, unless the acid is dope in a large amount until the equilibrium swelling in which the acid swells in the polymer electrolyte membrane becomes equilibrium, the proton conductivity becomes insufficient. Therefore, since the polymer electrolyte membrane has to be immersed in an acid for a long time, there is a problem that the productivity decreases and the mechanical strength of the membrane also decreases.

On the other hand, according to the manufacturing method of the polymer electrolyte membrane which concerns on this invention, it becomes possible to make a polymer and free acid compatible in polar organic solvent, and to form a film by the casting method. Therefore, a uniform dope film (acid-doped polymer electrolyte membrane) can be obtained directly after film forming. Therefore, according to the manufacturing method of the polymer electrolyte membrane which concerns on this invention, productivity of the acid-doped polymer electrolyte membrane can be improved. In the present invention, a polymer having an acidic functional group (for example, a sulfonic acid group) is used as the polymer, and the acidic functional group contributes to proton conduction. In addition, since the interaction between the acid to be dope and the acidic functional group in the polymer is weak, a polymer electrolyte membrane having high proton conductivity even at a low acid dope rate is obtained. In this way, since the acid doping rate can be lowered, it is not necessary to dope the acid until the equilibrium swelling of the polymer, so that the polymer electrolyte membrane prepared by the method of the present invention can have high mechanical strength.

(About secondary processing)

In the method for producing a polymer electrolyte membrane according to one embodiment of the present invention, when vinyl phosphonic acid is used as the free acid, the polymer electrolyte membrane after film formation may be semisolidified by secondary processing. That is, you may improve the intensity | strength of a film | membrane by superposing | polymerizing the vinyl phosphonic acid doped in the polymer electrolyte after a film forming process. Thereby, the mechanical strength of the film-formed polymer electrolyte membrane can be improved. As a method of polymerizing vinylphosphonic acid, for example, a method of irradiating a film-like polymer electrolyte membrane with ultraviolet light, β-rays, γ-rays, electron beams, or a combination thereof, or a method using a polymerization initiator can be used. It does not specifically limit. As the polymerization initiator, for example, an azo-based polymerization initiator represented by azobisisobutyronitrile, dimethyl 2,2'-azoisobutyrate, a peroxide-based polymerization initiator represented by benzoyl peroxide, or di-t-butyl peroxide And radical living polymerization initiators substituted for 2,2,6,6-tetrapiperidinyloxyl, and photopolymerization initiators such as Irgacure651, 184, 369 can be used in polymerization by ultraviolet light.

In addition, in the above-mentioned solution preparation process, a mixed solution in which a polyfunctional polymerizable compound is dissolved in a polar organic solvent in addition to a polymer electrolyte and a free acid source is prepared, and the mixed solution is formed into a film by wet film formation. You may copolymerize a compound and vinylphosphonic acid. By copolymerizing the polyfunctional polymerizable compound with vinyl phosphonic acid in this manner, the water-soluble component of vinyl phosphonic acid can be reduced, and the mechanical strength of the formed polymer electrolyte membrane can be improved. As a result, an increase in battery internal resistance caused by the outflow of acid components into the generated water during power generation is suppressed, thereby enabling long-term operation. As a method of polymerizing vinylphosphonic acid, the method of irradiating an ultraviolet-ray, (beta) ray, (gamma) ray, an electron beam, or a combination thereof to the film-form polymer electrolyte membrane formed into a film, for example, the method of using a polymerization initiator, etc. can be used. . As the polyfunctional polymerizable compound, for example, polyfunctional vinyl compounds such as divinylbenzene, divinylphenylphosphine, divinylsiloxane, triethylene glycol diacrylate, trimethylolpropane triacrylate, pentaerythritol tetraacrylic And polyfunctional acrylate compounds such as triethylene glycol dimethacrylate and the like can be used.

[Structure of Polymer Electrolyte Membrane According to the Present Invention]

In the above, the manufacturing method of the polymer electrolyte membrane which concerns on this invention was demonstrated in detail, Next, the structure of the polymer electrolyte membrane which concerns on this invention manufactured by such a method is demonstrated.

The polymer electrolyte membrane according to the present invention is doped with a free acid composed of an acidic inorganic phosphorus compound or an acidic organic phosphorus compound, with an aromatic engineering plastic having an acidic functional group as a main skeleton. Here, for example, polyethersulfone, polybenzimidazole, etc. can be used as the aromatic engineering plastics, and for example, phosphoric acid, polyphosphoric acid, phosphonic acid, etc. can be used as the acidic inorganic phosphorus compound, acidic As the organophosphorus compound, for example, vinylphosphonic acid, ethylphosphonic acid and the like can be used, detailed description thereof will be omitted.

(About an effect)

According to the polymer electrolyte membrane according to the present invention as described above, as described above, a polymer having an acidic functional group (for example, a sulfonic acid group) is used as the polymer which becomes the main skeleton of the polymer electrolyte membrane, and the acidic functional group is proton conductive. Contribute to. In addition, since the interaction between the acid to be dope and the acidic functional group in the polymer is weak, the polymer electrolyte membrane according to the present invention can have high proton conductivity even at a low acid dope rate. In addition, since the doping ratio of the acid can be reduced in this way, it is not necessary to dope the acid until the equilibrium swelling of the polymer, so that the polymer electrolyte membrane according to the present invention can have high mechanical strength.

In addition, when vinyl phosphonic acid is used as the free acid and vinyl phosphonic acid is polymerized after film formation, vinyl phosphonic acid doped in a polymer electrolyte mainly composed of aromatic engineering plastics is polymerized to improve the mechanical strength of the film. have. Moreover, when copolymerizing with vinyl phosphonic acid using a polyfunctional polymerizable compound, not only the mechanical strength of a film | membrane improves but also the water-soluble component of vinyl phosphonic acid can be reduced, and the acid by the produced | generated water in power generation by this is made. The outflow of minutes becomes avoidable and long-term operation becomes possible.

[Fuel cell according to the present invention]

A fuel cell according to the present invention includes a membrane electrode assembly (MEA: Membrane Electrode Assembly) using the above-described polymer electrolyte membrane. Since the polymer electrolyte membrane according to the present invention is stable under conditions of high temperature (for example, about 150 ° C.) and no humidification and has high proton conductivity and mechanical strength, the fuel cell according to the present invention using the same has electromotive force characteristics, current- It is excellent in power generation characteristics such as voltage characteristics and battery life.

The fuel cell according to one embodiment of the present invention can be manufactured by a known method using the polymer electrolyte membrane obtained as described above.

That is, in the case of PEFC, for example, both sides of the polymer electrolyte membrane obtained as described above are interposed with a catalyst layer as an electrode, a gas diffusion layer is provided, and these are integrated to manufacture an MEA. Next, a unit cell is formed by interposing both sides of the MEA with a separator such as a metal separator, and a plurality of unit cells can be arranged to manufacture a fuel cell stack.

Next, the present invention will be described in more detail using examples.

(Review on the Mixing Ratio of Polymer Electrolyte and Free Acid)

First, the result examined by the present inventors about the compounding ratio of a polymer electrolyte and a free acid is demonstrated.

Experimental Example 1

First, as an example of a sulfonated polymer as a polymer electrolyte, sulfonated polyether ether ketone is used, polyphosphoric acid (hereinafter referred to as "PPA") as a free acid, DMAc as a polar organic solvent, and 100 parts by weight of polymer When the amount of PPA to 20 to 160 parts by weight, the range of the amount of PPA that can produce a uniform mixed solution was examined. The results are shown in Table 3 below.

In addition, as mentioned above, although PPA is insoluble in DMAc normally, it becomes soluble in DMAc which melt | dissolved the sulfonated polymer.

[Table 3]

Table 3 shows the compounding ratio (parts by weight) of PPA to polymers, the amount of DMAc and PPA (g), and the state of the mixed solution after preparation. In order to obtain a uniform polymer electrolyte membrane, it is necessary to obtain a uniform mixed solution. As shown in Table 3, in order to obtain a uniform mixed solution, the amount of PPA for the sulfonated polymer is preferably 20 to 80 parts by weight. , 80 parts by weight can be seen that particularly preferred.

In addition, the result of forming into a film the mixed solution manufactured as mentioned above by the casting method is shown in Table 4 below. In the polymer electrolyte membrane according to the present experimental example, about 0.5 cm ³ of the prepared mixed solution was used, cast with a gap of 500 µm on a substrate, and dried to form a film. In addition, drying was performed for 30 minutes in 120 degreeC in oven after preliminary drying at 60 degreeC on a hotplate for 1 hour.

[Table 4]

Table 4 shows the compounding ratio (part by weight) of PPA to the polymer, the film thickness of the obtained polymer electrolyte membrane, and the state of the membrane. As shown in Table 4, it can be seen that the amount of PPA for the sulfonated polymer is not leached out of phosphoric acid at 20 to 80 parts by weight, and in particular, it is understood that a film having a uniform amount of PPA at 80 parts by weight is obtained.

Experimental Example 2

In Experimental Example 2, except for using NMP as a polar organic solvent, the range of the amount of PPA which can produce a uniform mixed solution like Example 1 was examined. The results are shown in Table 5 below.

TABLE 5

Table 5 shows the compounding ratio (part by weight) of PPA to polymer, the amount of NMP and PPA (g), and the state of the mixed solution after preparation.

As shown in Table 5, in order to obtain a uniform mixed solution, it can be seen that the amount of PPA to the sulfonated polymer is preferably 20 to 80 parts by weight.

In addition, even when the amount of PPA was 100 parts by weight, it was possible to obtain a uniform mixed solution, but it was difficult to cast to the substrate because the viscosity was very high and there was almost no fluidity. Therefore, from the viewpoint of obtaining a uniform polymer electrolyte membrane, the amount of PPA for the sulfonated polymer is preferably 80 parts by weight or less. In addition, from the viewpoint of proton conductivity, the larger the amount of PPA, the more advantageous. However, if PPA exceeds 120 parts by weight, casting to a substrate becomes impossible, and thus a polymer electrolyte membrane cannot be obtained.

As can be seen from the results shown in Tables 3 and 5 above, even when either DMAc or NMP having different solubility in PPA was used, the same results were obtained for the blending ratio of PPA to the sulfonated polymer.

In addition, as a result of forming the mixed solution prepared as described above by the casting method as in Experimental Example 1, as shown in Table 6, the amount of PPA for the sulfonated polymer was 20 to 80 parts by weight of the outside of phosphoric acid. It can be seen that there is no leaching of the furnace, and in particular, a uniform film is obtained at an amount of 80 parts by weight of PPA.

TABLE 6

(Review on preliminary drying time)

Next, the result which the present inventors examined about the drying time in a predrying process is demonstrated.

<Experimental Example 3>

In this Experimental Example, a mixed solution cast on a polyimide glass substrate (here, 20 wt% of sulfonated polyether ether ketone (S-PEEK) as a polymer was dissolved in DMAc so as to be 60 wt% based on the polymer weight). Solution with PPA) was dried on a hot stirrer to check the volatilization amount of the solvent. The volatilization amount of the solvent measures the change amount (reduction amount) of the weight of the membrane at the time of drying time 10 minutes, 20 minutes, 30 minutes, 40 minutes, 50 minutes, and 60 minutes, and the amount of change in the weight of the membrane to the weight of the membrane before drying. The ratio is shown as the ratio of the volatilized solvent. In addition, this experiment was performed in the airless state without a blower. The results are shown in Table 7 below.

TABLE 7

As shown in Table 7, the surface of the polymer electrolyte membrane was formed when the drying time had elapsed for 10 minutes, and it was possible to peel off the film on the glass substrate after 20 minutes had elapsed. That is, it turns out that it is necessary to dry at least 10 minutes at 60 degreeC, and to send it to this drying of a post process. In addition, it can be said that preliminary drying is necessary for at least 20 minutes if the substrate used for casting is peeled off after preliminary drying and subjected to wind from the blower on both sides in this drying. On the contrary, if it is sent to this drying of a post process with a base material (back film) affixed, it turns out that predrying is enough about 10 minutes.

(Review about this drying temperature)

Next, the result which the present inventors examined about the drying temperature in the drying (main drying) process after preliminary drying is demonstrated.

Experimental Example 4

In this experimental example, a mixed solution cast on a polyimide glass substrate (here, 20 wt% of sulfonated polyether ether ketone (S-PEEK) as a polymer was dissolved in DMAc so as to be 60 wt% based on the polymer weight). The effect of drying temperature was investigated using PPA blended solution). In addition, after performing preliminary drying at 60 degreeC for 1 hour so that the produced polymer electrolyte membrane might not be influenced by the preliminary drying time, 20 minutes of main drying were performed at 110 degreeC, 130 degreeC, 150 degreeC, and 170 degreeC, respectively. The results of this experimental example are shown in Table 8 below.

[Table 8]

As shown in Table 8, at the drying temperature of 110 ° C., the surface of the film is in a slightly wet state under the influence of the doped phosphoric acid and the polar organic solvent, but it is considered that sufficient drying occurs at a drying temperature higher than 130 ° C. In addition, when it exceeds 150 degreeC, it is thought that the weight change according to dehydration of phosphoric acid appears, and the drying temperature of 110 degreeC or more and less than 150 degreeC is considered preferable. In addition, the phenomenon that the film discolored slightly multicolored at 130 degreeC or more was observed. This is thought to be a change in color due to dehydration of the adsorbed water around sulfonic acid. Since proton conduction is dominant in the contribution of phosphoric acid, there is almost no problem on the performance of proton conductivity of the polymer electrolyte membrane.

(Review about temperature and time of this drying)

Next, the result which the present inventors examined about the drying temperature and drying time in the drying (main drying) process after preliminary drying is demonstrated.

Experimental Example 5

In this experimental example, a mixed solution cast on a polyimide glass substrate (here, 20 wt% of sulfonated polyether ether ketone (S-PEEK) as a polymer was dissolved in DMAc so as to be 60 wt% based on the polymer weight). The effect of drying temperature and drying time were investigated using PPA blended solution). After the preliminary drying at 60 ° C. for 20 minutes on the prepared polymer electrolyte membrane, the main drying was carried out at drying temperatures of 110 ° C., 130 ° C., 150 ° C. and 170 ° C. for 20 minutes, 40 minutes, 60 minutes and 80 minutes, respectively. It was done. The results of this experimental example are shown in Table 9 below.

TABLE 9

As shown in Table 9, the weight loss of the polymer electrolyte membrane was about 10% at 20 minutes of drying at any temperature. That is, it can be seen that more than 80% of the solvent can be removed by the sum of the predrying and the main drying. In addition, it can be seen from the results shown in Table 9 that the influence of the solvent removal amount by the drying temperature is relatively small, but the change of the solvent removal amount with the drying time is large. Moreover, when manufacturing with a real machine, considering that printing (cast) and drying are carried out between rolls using PET etc. as a base material, it can be said that the drying temperature below 150 degreeC is preferable, and at drying time, Even if it is dried for 20 minutes or more, since the amount of change in the weight of the polymer electrolyte membrane does not change so much, it can be said that it is enough for about 20 minutes. Of course, if it dries for a long time, the removal amount of water and a solvent will increase by that much, and even if it is 20 minutes or more in balance with productivity, there is no problem.

(Influence on Ionic Conductivity of Free Acid Blend)

Next, the result which the present inventors examined about the influence on the ion conductivity of a free acid compounding quantity is demonstrated.

<Experimental Example 6>

In this experimental example, sulfonated polyether ether ketone (S-PEEK) was used as a polymer having an acidic functional group, PPA was used as a free acid, and a mixed solution dissolved in each of DMAc and NMP was used as a polar organic solvent. Ion conductivity at 130 ° C. of the polymer electrolyte membrane thus formed was measured. The measuring method of ion conductivity is as follows. Each electrolyte membrane was drilled in a circle of 13 mm Φ and inserted into a bipolar platinum blocking electrode cell having a Teflon (registered trademark) housing, fixed in a thermostat, heated to 150 ° C, and left for one day. Measured. The resistance measurement was performed using SI1287 Electrochemical Interface and SI1260 Impedance / gain phase analyzer from Solartron, UK. Ionic conductivity was computed from the obtained bulk resistance and cell constant. The results are shown in Table 10 below. In addition, in Table 10 below, "PPA20" etc. represent the compounding quantity of PPA with respect to a polymer, For example, if it is PPA20, it means that 20 weight part of PPA exists in a polymer electrolyte membrane with respect to 100 weight part of polymers.

TABLE 10

As shown in Table 10, when the compounding quantity of PPA was 20-80 weight part with respect to 100 weight part of polymers, all showed favorable proton conductivity. In addition, it is understood that the proton conductivity does not depend on the kind of the polar organic solvent, but the amount of PAA increases up to 20 to 60 parts by weight, and slightly decreases at 80 parts by weight as 60 parts by weight as a peak. From these results, it is understood that the blending amount of free acid such as PPA is preferably 20 parts by weight or more and 80 parts by weight or less, more preferably 40 to 80 parts by weight, and most preferably 60 parts by weight with respect to 100 parts by weight of the polymer electrolyte. .

Evaluation of Physical Properties of Polymer Electrolyte Membrane

A polymer electrolyte membrane was prepared using three types of polymer electrolytes synthesized by the method described below, and the proton conductivity of the produced polymer electrolyte membrane and the power generation characteristics of the fuel cell produced using the obtained polymer electrolyte membrane were evaluated. The test method of proton conductivity and power generation characteristics is as follows.

<Test method of ion conductivity measurement>

Each electrolyte membrane was drilled in a circle of 13 mm Φ and inserted into a bipolar platinum blocking electrode cell having a Teflon (registered trademark) housing, fixed in a thermostat, heated to 150 ° C, and left for one day. Measured. The resistance measurement was performed using SI1287 Electrochemical Interface and SI1260 Impedance / gain phase analyzer from Solartron, UK. Ionic conductivity was computed from the obtained bulk resistance and cell constant.

<Test Method of Power Generation Characteristics of Fuel Cell>

The produced electrolyte membrane was cut into 2.8 cm angles by inserting it into a commercial gas diffusion electrode (electrode with a catalyst from US Electrochem; electrode with a catalyst Pt 1mg / cm ² attached to carbon paper; EC-20-10-7). A membrane-electrode assembly (MEA) was produced. Next, the gasket of the Teflon (registered trademark) and the MEA were sandwiched by a carbon separator in which a gas flow path was formed, and then, the current collector plate and the end plate were disposed outside the anode, and fastened with bolts to form a test cell. The test cell was heated to 150 ° C. while purging with nitrogen, and hydrogen and oxygen were introduced into the cell directly (via a humidifier) via a mass flow that controls the flow rate from the bomb. HZ-3000, an electrochemical measuring device manufactured by Hokuto Electric Industries, was used to investigate the polarization and continuous power generation characteristics of power generation.

Synthesis of Polymer Electrolyte

Next, a method for synthesizing the polymer electrolyte will be described.

(A) "J. Kerres et al., Electrochem. Syst. 3 (2000) 129 ', sulfonated polyetheretherketone (hereinafter referred to as "S-PEEK") as shown in the following formula (2) by sulfonating polyetheretherketone. Ew (equivalent weight) ) = 570). Specifically, 50 g of polyether ether ketone (PEEK450P, manufactured by Mitsui Toatsu Chemical Co., Ltd.) was dispersed in 98% sulfuric acid and reacted at 35 ° C. for 24 hours, followed by rinsing the reaction solution in cooling water little by little and washing with water until the pH became neutral. Repeated. The sulfonated polyether ether ketone obtained was determined to have an Ew of 570 by the combustion-ion chromatography method.

(B) "R. Guan et at., Euro Polym. Based on the contents described in J., 41 (2005) 1554, sulfonated polyethersulfone as described in the following formula (3) by sulfonating polyethersulfone (hereinafter referred to as "S-PES"). 550). Specifically, 20 g of polyether sulfone (poly 1,4-phenylene ether sulfone, manufactured by Aldrich Co., Ltd.) was dispersed in 100 mL of 98% sulfuric acid, followed by reaction at room temperature for 2 hours, and then 80 mL of chlorosulfonic acid was slowly added dropwise. After holding the reaction solution at about 10 ° C. for about 1 hour, the reaction solution was poured into the cooling water little by little as in (A), and water washing was repeated until the pH became neutral. The sulfonated polyether sulfone thus obtained was determined to have an Ew of 550 using a reverse titration method. However, when the dropwise amount of chlorosulfonic acid was set to 60 mL or 70 mL, the sulfonation degree expected of the obtained polymer Ew was not obtained unlike the paper. Here, the sample with 80 mL of chlorosulfonic acid dropping quantity was used as a sample with a clear Ew of 550.

(C) 『X. Based on the contents described in Glipa et al., Solid State Ionics 97 (1997) 323, sulfonated polybenzimidazoles as shown in the following formula (4) by sulfonating polybenzimidazole (hereinafter referred to as "S-PBI" Ew = 770). Specifically, polybenzimidazole was first synthesized as follows, and then sulfonated after ionization. In 35 g of polyphosphoric acid (manufactured by Kishida Chemical Co., Ltd.), 3,4-diamino benzoic acid (2.60 g, manufactured by Tokyo Chemical Co., Ltd.), 1.83 g of 3,3'-diaminobenzidine (Aldrich) and 1.42 g of iso Phthalic acid (manufactured by Tokyo Chemical Co., Ltd.) was added thereto and reacted at 200 ° C for 5 hours.

The reaction solution was poured into a large amount of cold water, the reaction solution was poured into the cooling water little by little, and water washing was repeated until the pH became neutral.

Polybenzimidazole obtained by performing vacuum drying at 60 ° C. for 24 hours was dissolved in dimethylacetamide (manufactured by Kishida Chemical Co., Ltd.), and then subjected to retylation using lithium hydride (manufactured by Aldrich). Here, the ratio PBI: LiH described in the paper as the molar ratio is described to lose activity by reacting with moisture of the impurity.

Thereafter, the synthesized 4-bromomethylbenzenesulfonic acid was added in excess, stirred at 75 ° C. for 24 hours under a nitrogen atmosphere, and then charged in excess tetrahydrofuran to reprecipitate.

Thereafter, the solution was dissolved once in dimethylacetamide, the insoluble portion was filtered off, and then charged again in ultrapure water. The precipitate was filtered and then vacuum dried at 60 ° C. for 24 hours to obtain sulfonated polybenzimidazole. Ew was determined to be 770 from the quantification of sulfur by combustion-ion chromatography as in (A).

Next, the prepared polymer solution was precipitated in water to obtain the polybenzimidazole-based polymer.

[Formula 2]

(3)

[Formula 4]

In addition, the solubility of the non-sulfonated polymer and the sulfonated polymer, which are the raw materials of the sulfonated polymer, and the polar organic solvent and the compatibility of N-methylpyrrolidone (NMP) containing phosphoric acid, respectively, were investigated. The NMP in which phosphoric acid was dissolved was assumed to have dissolved 2.00 g of polyphosphoric acid (116% phosphoric acid) in 12.00 g of NMP. In addition, as a judgment of solubility, it judged whether 20% by weight of the polymer was added to the polar organic solvent and stirred to prepare a transparent solution. The results are shown in Table 11 below.

TABLE 11

As shown in Table 11, it can be seen that the sulfonated S-PEEK and S-PES are not dissolved in any of DMAc and NMP, but are dissolved in the same solvent by sulfonation. On the other hand, S-PBI is soluble in both DMAc and NMP, but when phosphoric acid is mixed, it forms a precipitate. However, it was confirmed that sulphonation makes it soluble in the same solvent even in the mixture of phosphoric acid. Using this material, a polymer electrolyte membrane according to one embodiment of the present invention was prepared as follows.

Example 1

2.50 g of sulfonated polybenzimidazole (S-PBI) synthesized according to the above procedure was taken, and 2.50 g of polyphosphoric acid was added to 12.00 g of N-methylpyrrolidone (NMP), which was stirred at room temperature per day.

Next, an NMP solution of S-PBI and polyphosphoric acid was added to a uniform phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform mixed solution. This was formed on a glass substrate by a cast method using a doctor blade. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the polymer electrolyte membrane was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and was peeled off from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 130 micrometers.

[Example 2]

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure was taken, and 2.00 g of polyphosphoric acid was added to NMP 12.00 g and stirred at room temperature per day.

Next, an NMP solution of S-PEEK and polyphosphoric acid was added to a uniform phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform mixed solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 138 micrometers.

Example 3

3.00 g of sulfonated polyether sulfone (S-PES) synthesized according to the above procedure was taken, and 2.00 g of polyphosphoric acid was added to NMP 12.00 g and stirred at room temperature per day.

Next, an NMP solution of S-PES and polyphosphoric acid was added to a uniform phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the polymer electrolyte membrane was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and was peeled off from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 135 micrometers.

Example 4

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure was taken, and 2.00 g of polyphosphoric acid and 1.00 g of benzimidazole were added to NMP 12.00 g and stirred at room temperature per day.

Next, an NMP solution of S-PEEK, polyphosphoric acid and benzimidazole was added to a uniform phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the casting method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 134 micrometers.

Example 5

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure was taken, and 2.00 g of polyphosphoric acid and 1.00 g of 1-methyl-3-butyltrifluorosulfoimide (EMITFSI) were added to NMP 12.00 g. In addition, the mixture was stirred at room temperature for one day.

Next, an NMP solution of S-PEEK, polyphosphoric acid and EMITFSI was added to a uniform phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 125 µm.

[Example 6]

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure was taken, and 1.00 g of vinylphosphonic acid was added to NMP 12.00 g and stirred at room temperature per day.

Next, an NMP solution of S-PEEK and vinylphosphonic acid was added to the homogenized phosphoric acid-NMP solution and stirred at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 125 µm.

Example 7

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure, 4.00 g of vinylphosphonic acid, 2.00 g of polyethylene glycol dimethacrylate, and 0.3 g of azobisisobutyronitrile were added to 10.00 g of dimethylacetamide. It was dissolved and stirred at 25 ° C. for 3 hours to prepare a uniform solution. The solution was cast on a glass substrate using a doctor blade, dried at 80 ° C. for 3 hours to remove dimethylacetamide, and then heat treated at 100 ° C. for 19 hours in vacuum and 0.5 ° C. for 0.5 hours. It peeled from the glass substrate and obtained the self-supporting film | membrane. The thickness of the obtained film was 175 mu m. Further, the obtained polymer electrolyte membrane was immersed in hot water at 80 ° C. for 30 minutes, and the dissolution rate of the acid and the crosslinking agent component in the membrane before dipping was calculated from the amount of the acid and the crosslinking agent component eluted in the immersion liquid. The conductivity of the polymer electrolyte membrane at 150 ° C. was measured by the alternating current impedance method and found to be 0.61 mS / cm.

In addition, the detail of the measuring method of a dissolution rate is as follows. That is, 0.07 g of the membrane sample was immersed in 2 g of pure water and allowed to stand for 30 minutes in an 80 ° C oven. Thereafter, the membrane was taken out of pure water, 1 g of immersion liquid was taken, and placed in a glass bottle, and heated at 150 ° C. for 30 minutes. The weight of the residue remaining in the bottle was measured, and the dissolution rate was calculated from the following equation.

Dissolution rate (%) = [1- (weight of residue eluted in membrane sample)

/ (Total weight of acid component and crosslinking agent component in the sample film)] × 100

Example 8

A self-supporting film was obtained in the same manner as in Example 7, except that 2.30 g of vinylphosphonic acid, 2.30 g of polyethylene glycol dimethacrylate, and 0.2 g of azobisisobutyronitrile were used. The dissolution rate of the acid and the crosslinking agent component of the membrane was 5%, and the conductivity at 150 ° C. was 0.02 mS / cm.

Comparative Example 1

3.00 g of sulfonated polyether ether ketone (S-PEEK) synthesized according to the above procedure was taken and added to NMP 12.00 g, followed by stirring at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 80 µm.

Comparative Example 2

3.00 g of the sulfonated polyether ether ketone (S-PEEK) synthesized as described above was added to NMP 12.00 g in which 1.00 g of benzimidazole was dissolved, and stirred at room temperature for 3 hours to obtain a uniform solution. This was formed into a film by the cast method using the doctor blade on the glass substrate. After drying the obtained polymer electrolyte membrane at 80 ° C. for 3 hours, the resultant was dried at 120 ° C. for 2 hours to remove NMP as a solvent, and peeled from a glass substrate to obtain a self-supporting membrane. The thickness of the obtained film was 85 µm.

(About evaluation result of ion conductivity)

The result of measuring the proton conductivity of the membrane of Examples 1-5 in the polymer electrolyte membrane obtained as mentioned above is shown in FIG. 1, and the result of measuring the proton conductivity of the membrane of Example 8 is shown in FIG. 1 is an Arrhenius plot of the ion conductivity of Examples 1 to 5 of the present invention, wherein the vertical axis represents ion conductivity [Scm ⁻¹ ] and the horizontal axis represents temperature (1000 / T) [K ⁻¹ ]. 2 is an Arenius plot of ion conductivity of Example 8 of the present invention, where the vertical axis represents ion conductivity [Scm ⁻¹ ] and the horizontal axis represents temperature (1 / T) [K ⁻¹ ].

As shown in FIG. 1 and FIG. 2, the polymer electrolyte membranes of Examples 1 to 5 and Example 8 of the present invention have a proton conductivity that can be sufficiently developed even under conditions of high temperature (about 150 ° C) and no humidification. Able to know.

(Evaluation result of development characteristic)

Next, a test cell of a fuel cell was fabricated as described above using the polymer electrolytes of Examples 2 and 3 among the polymer electrolyte membranes obtained as described above, and the power generation characteristics (polarization characteristics) were evaluated. 3 and 4 are shown. 3 is a graph showing the polarization curve of the fuel cell test cell fabricated using the polymer electrolyte membrane of Example 2 of the present invention, wherein the vertical axis represents voltage [V] and the horizontal axis represents current [mA]. 4 is a graph showing the polarization curve of the fuel cell test cell fabricated using the polymer electrolyte membrane of Example 3 of the present invention, wherein the vertical axis represents voltage [V] and the horizontal axis represents current [mA].

As shown in Figs. 3 and 4, the test cells prepared using the polymer electrolytes of Examples 2 and 3 of the present invention have excellent polarization characteristics even under the conditions of high temperature (˜150 ° C.) and no humidification. It can be seen that. Moreover, the open circuit voltage (OCV) of Example 2 was 0.987 [V], and the OCV of Example 3 was 0.872 [V], and all showed high values.

As mentioned above, although one Example which was very suitable was described, referring an accompanying drawing, Of course, this invention is not limited to this example. It will be apparent to those skilled in the art that various modifications or changes can be made within the scope of the claims, and naturally, they also belong to the technical scope according to the embodiment of the present invention.

1 is an Arrhenius plot showing the ionic conductivity of Examples 1 to 5 of the present invention,

2 is an Arrhenius plot showing the ionic conductivity of Example 8 of the present invention,

3 is a graph showing a polarization curve of a fuel cell test cell fabricated using the polymer electrolyte membrane of Example 2 of the present invention.

4 is a graph showing a polarization curve of a fuel cell test cell manufactured using the polymer electrolyte membrane of Example 3 of the present invention.

Claims (20)

A polymer electrolyte having an acidic functional group, Wet forming a mixed solution in which a mixture of a free acid and an organic salt containing a quaternary ammonium cation is dissolved in a polar organic solvent to obtain a polymer electrolyte membrane doped with a mixture of free acid and an organic salt containing a quaternary ammonium cation in the polymer electrolyte. Method for producing a polymer electrolyte membrane, characterized in that. The method of claim 1, wherein the main skeleton of the polymer electrolyte is an aromatic engineering plastic. The method of claim 2, wherein the aromatic engineering plastic is polyether sulfone or polybenzimidazole. The method of claim 1, wherein the free acid is an acidic inorganic phosphorus compound or an acidic organic phosphorus compound. The method of claim 4, wherein the acidic inorganic phosphorus compound is phosphoric acid, polyphosphoric acid or phosphonic acid. The method of claim 4, wherein the acidic organic phosphorus compound is vinylphosphonic acid or ethylphosphonic acid. delete The method of claim 1, wherein the polar organic solvent is an amide organic solvent. The method of claim 8, wherein the amide organic solvent is dimethylacetamide, N-methyl-2-pyrrolidone or dimethylformamide. delete The method of claim 1, wherein 20 to 80 parts by weight of the free acid is dissolved in the polar solvent based on 100 parts by weight of the polymer electrolyte. The method of claim 1, wherein the free acid is vinyl phosphonic acid, After the wet film formation, polymerizing the vinyl phosphonic acid doped in the polymer electrolyte. The method according to claim 12, wherein the mixed solution in which the polyfunctional polymerizable compound is further dissolved in the polar organic solvent is wet formed into a film. The method for producing a polymer electrolyte membrane, wherein the polyfunctional polymerizable compound and the vinyl phosphonic acid are copolymerized after the wet film formation. The method of claim 13, wherein the polyfunctional polymerizable compound is a polyfunctional vinyl compound, diacrylate or dimethacrylate. A polymer electrolyte membrane comprising an aromatic engineering plastic having an acidic functional group as a main skeleton and a mixture of a free acid selected from an acidic inorganic phosphorus compound and an acidic organic phosphorus compound and an organic salt containing a quaternary ammonium cation. The polymer electrolyte membrane according to claim 15, wherein the aromatic engineering plastic is polyethersulfone or polybenzimidazole. The polymer electrolyte membrane of Claim 15, wherein the acidic inorganic phosphorus compound is phosphoric acid, polyphosphoric acid, or phosphonic acid. The polymer electrolyte membrane of Claim 15, wherein the acidic organophosphorus compound is vinylphosphonic acid or ethylphosphonic acid. A fuel cell comprising the membrane electrode assembly using the polymer electrolyte membrane according to any one of claims 15 to 18. The method according to claim 15, wherein the organic salt, 1,3-dimethylimidazolium dihydrogenphosphite (DMIP), 1-butyl-3-methylimidazolium dihydrogenphosphite (BMIP), 1-hexyl-3-methylimidazolium dihydrogenforce Hite (HMIP), 1-methyl-3-octylimidazolium dihydrogenphosphite (MOIP), 1-dodecyl-3-methylimidazolium dihydrogenphosphite (C12MIP), 1-hexadecyl-3 -Polymer electrolyte membrane which is methyl imidazolium dihydrogen phosphite (C16MIP) or 1-dodecyl-3-methyl imidazolium hydrogensulfite (C12MIS).

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