JP2010006940A - Solid polymer electrolyte composition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a solid polymer electrolyte composition having excellent ionic conductivity and oxidation resistance. <P>SOLUTION: The solid polymer electrolyte composition includes: a solid polymer electrolyte comprising 100 pts.mass aromatic polyimide having at least one repeating unit selected from the group consisting of repeating units represented by formula (I) and formula (II) and 0.1 to 100 pts.mass at least one acid selected from phosphoric acid, polyphosphoric acid, sulfuric acid and methane sulfonic acid; and a polymer having ionic conductivity. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a solid polymer electrolyte composition comprising an aromatic polyimide and a fuel cell using the same.

  A solid polymer electrolyte is a solid polymer material having an electrolyte group in a polymer chain, and has a property of selectively permeating a cation or an anion by firmly binding to a specific ion. It is formed into particles, fibers, or membranes, and is used for various applications such as electrodialysis, diffusion dialysis, and battery membranes.

  A fuel cell is provided with a pair of electrodes on both sides of an ion-conducting solid polymer electrolyte membrane, supplying hydrogen gas, methanol, or the like as fuel to one electrode (fuel electrode), and oxygen gas or air as an oxidant. It supplies to an electrode (air electrode) and obtains an electromotive force. In water electrolysis, hydrogen and oxygen are produced by electrolyzing water using a solid polymer electrolyte membrane.

  To the perfluorosulfonic acid membrane having high ion conductivity known as Nafion (registered trademark, manufactured by DuPont), Aciplex (registered trademark, manufactured by Asahi Kasei Co., Ltd.), Flemion (registered trademark, manufactured by Asahi Glass Co., Ltd.) Representative fluorine-based electrolyte membranes are widely used as solid polymer electrolyte membranes for fuel cells and water electrolysis because of their excellent chemical stability.

  Moreover, salt electrolysis produces sodium hydroxide, chlorine, and hydrogen by electrolyzing a sodium chloride aqueous solution using a solid polymer electrolyte membrane. In this case, since the solid polymer electrolyte membrane is exposed to chlorine, high temperature, and high concentration sodium hydroxide aqueous solution, it is not possible to use a hydrocarbon electrolyte membrane having poor resistance to these. For this reason, solid polymer electrolyte membranes for salt electrolysis are generally resistant to chlorine and high-temperature, high-concentration sodium hydroxide aqueous solution, and in addition, partly on the surface to prevent back diffusion of generated ions. A perfluorosulfonic acid film into which a carboxylic acid group is introduced is used.

  By the way, a fluorine-based electrolyte typified by a perfluorosulfonic acid membrane has a C—F bond and thus has a very high chemical stability. For the fuel cell, water electrolysis, or salt electrolysis described above. In addition to these solid polymer electrolyte membranes, they are also used as solid polymer electrolyte membranes for hydrohalic acid electrolysis, and also widely applied to humidity sensors, gas sensors, oxygen concentrators, etc. using ionic conductivity Has been.

  However, the fluorine-based electrolyte has a drawback that it is difficult to manufacture and is very expensive. Therefore, fluorine-based electrolyte membranes are used in limited applications such as space or military polymer electrolyte fuel cells, and are used for consumer applications such as polymer electrolyte fuel cells as low-pollution power sources for automobiles. Application was difficult.

  Therefore, an electrolyte membrane obtained by sulfonating an aromatic hydrocarbon polymer represented by engineering plastics has been proposed as an inexpensive solid polymer electrolyte membrane. (For example, see Patent Documents 1, 2, 3, 4, and 5). An aromatic hydrocarbon electrolyte membrane obtained by sulfonating these engineering plastics has an advantage of easy production and low cost when compared with a fluorine electrolyte membrane represented by Nafion. However, it has a drawback that it is very weak in terms of oxidation resistance.

  According to Non-Patent Document 1, it is reported that, for example, sulfonated polyether ether ketone and polyether sulfone deteriorate from an ether portion adjacent to sulfonic acid. From this, it is considered that when an electron donating group is present in the vicinity of the sulfonic acid, the oxidative degradation starts therefrom. Therefore, for the purpose of improving oxidation resistance, a sulfonated polyphenylenesulfone whose main chain is composed of only an electron-withdrawing group and an aromatic ring has been proposed (Patent Document 6), and sulfonated by introducing a sulfonic acid into a site adjacent to the sulfonate group. Polysulfone has been proposed (Non-Patent Document 2).

  However, according to Patent Document 7, the aromatic hydrocarbon electrolyte membrane is deteriorated not only by oxidative deterioration but also by a sulfonic acid group, which is an ion conductive substituent directly bonded to the aromatic ring, under strong acid and high temperature. It is considered that the ionic conductivity is decreased due to desorption, and sulfonated polyphenylenesulfone and sulfonated polysulfone as described in Patent Document 6 and Non-Patent Document 2 cannot avoid deterioration due to sulfonic acid desorption. Therefore, it is not desirable that the ion conductive substituent is a sulfonic acid, and Patent Document 7 proposes to use an alkylsulfonic acid instead of the sulfonic acid. This is effective in improving the decrease in ionic conductivity due to elimination of sulfonic acid, but the main chain of the aromatic polymer used contains an electron-donating group, which is inferior in oxidation resistance.

On the other hand, azole polymers are expected as solid electrolyte membranes for fuel cells as polymers having excellent heat resistance and chemical resistance.
For example, a sulfonated azole polymer has been reported as an azole polymer having ion conductivity (Patent Document 8). However, as described above, a sulfonic acid group introduced on an aromatic ring using a polymer as a raw material is likely to undergo a desulfonic acid reaction due to acid or heat, and is sufficiently durable to be used as an electrolyte membrane for a fuel cell. I can not say.

Non-patent document 3, for example, reports an azole polymer having a hydroxyl group and a method for producing the azole polymer. Moreover, there is a report example about the conductivity measurement of the ion implantation product of the azole polymer film having a hydroxyl group (Non-patent Document 4).
However, none of these has been focused on as a functional group for ion-conducting a hydroxyl group, and none of them has sufficiently exemplified durability under the conditions for use with a fuel cell.
Further, Patent Document 9 is an example in which a polybenzazole-based polymer is cited as a reinforcing material for a solid polymer electrolyte membrane, that is, a support membrane for an ion exchange membrane.

JP-A-6-93114 JP-A-9-245818 Japanese Patent Laid-Open No. 11-116679 Japanese National Patent Publication No. 11-510198 Japanese National Patent Publication No. 11-515040 JP 2000-80166 A JP 2002-110174 A JP 2002-146018 A JP 2005-68396 A Polymer Papers Vol. 59, no. 8, p. 460-473 Journal of Polymer Science: Part A: Polymer Chemistry, 1996, Vol. 34, p. 241-243 Polymer, 1994, Vol. 35, p. 3091 Polymeric Materials Science and Engineering, 1991, Vol. 64, p.171-172

  Provided is a solid polymer electrolyte composition excellent in ion conductivity and oxidation resistance, comprising a solid polymer electrolyte comprising an aromatic polyimide and a polymer having ion conductivity.

  The present invention relates to a solid polymer electrolyte composition excellent in ion conductivity and oxidation resistance, comprising a solid polymer electrolyte obtained from an aromatic polyimide as a specific copolymer and a polymer having ion conductivity. That is, the gist of the present invention is as follows.

で表される繰り返し単位よりなる群から選ばれる少なくとも１種の繰り返し単位からなる芳香族ポリイミド１００質量部と、リン酸、ポリリン酸、硫酸、メタンスルホン酸から選ばれる少なくとも１種の酸０．１〜１００質量部とからなる固体高分子電解質と、イオン伝導性を有する高分子とからなる固体高分子電解質組成物。
２．固体高分子電解質が厚さ１０〜２００μｍｍのフィルム形状である上記１項に記載の固体高分子電解質組成物。
３．イオン伝導性を有する高分子がパーフルオロカーボンスルホン酸樹脂である上記１項または２項に記載の固体高分子電解質組成物。
４．固体高分子電解質とイオン伝導性を有する高分子とがそれぞれフィルム状であり、それらの積層体となっている上記１〜３項のいずれかに記載の固体高分子電解質組成物。 1. Formulas (I) and (II) below

100 parts by mass of an aromatic polyimide composed of at least one repeating unit selected from the group consisting of repeating units represented by: at least one acid selected from phosphoric acid, polyphosphoric acid, sulfuric acid, and methanesulfonic acid 0.1 A solid polymer electrolyte composition comprising a solid polymer electrolyte comprising ˜100 parts by mass and a polymer having ion conductivity.
2. 2. The solid polymer electrolyte composition according to 1 above, wherein the solid polymer electrolyte is in the form of a film having a thickness of 10 to 200 μm.
3. 3. The solid polymer electrolyte composition according to 1 or 2 above, wherein the polymer having ion conductivity is a perfluorocarbon sulfonic acid resin.
4). 4. The solid polymer electrolyte composition according to any one of the above items 1 to 3, wherein the solid polymer electrolyte and the polymer having ion conductivity are each in the form of a film and are a laminate thereof.

  Low cost, high durability solid excellent in oxidation resistance and the like suitable for electrolyte membranes used in fuel cells, water electrolysis, hydrohalic acid electrolysis, salt electrolysis, oxygen concentrators, humidity sensors, gas sensors, etc. A polymer electrolyte composition can be obtained. The solid polymer composition is suitable as a fuel cell material.

  The present invention is a solid polymer electrolyte composition excellent in ion conductivity and oxidation resistance, comprising a solid polymer electrolyte comprising an aromatic polyimide and a polymer having ion conductivity. More preferably, it is a solid polymer electrolyte composition in which the solid polymer electrolyte is in the form of a film having a thickness of 10 to 200 μm. More preferably, it is a solid polymer electrolyte composition in which the solid polymer electrolyte and the polymer having ion conductivity are each in the form of a film and are a laminate thereof.

で表される繰り返し単位よりなる群から選ばれる少なくとも１種の繰り返し単位からなる芳香族ポリイミド１００質量部と、リン酸、ポリリン酸、硫酸、メタンスルホン酸から選ばれる少なくとも１種の酸０．１〜１００質量部からなる固体高分子電解質である。 <Solid polymer electrolyte>
The solid polymer electrolyte used in the present invention has the following formulas (I) and (II):

100 parts by mass of an aromatic polyimide composed of at least one repeating unit selected from the group consisting of repeating units represented by: at least one acid selected from phosphoric acid, polyphosphoric acid, sulfuric acid, and methanesulfonic acid 0.1 It is a solid polymer electrolyte consisting of ˜100 parts by mass.

（上記式中、ＸはＦ、Ｃｌ、Ｂｒ、Ｉから選らばれる１種類以上のハロゲン、Ｒ^１は炭素数１〜１０の炭化水素基を表す）

（上記式中、ＸはＦ、Ｃｌ、Ｂｒ、Ｉから選らばれる１種類以上のハロゲン、Ｒ^２は炭素数１〜１０の炭化水素基を表す）
で表される芳香族テトラカルボン酸誘導体のいずれか１種以上と、下記式（Ｂ）および（Ｃ）

で表される芳香族ジアミンおよびその塩酸塩、硫酸塩、リン酸塩からなる群から選ばれる少なくとも１種とを反応させて得られる（以下、前記式（Ａ−１）、（Ａ−２）、（Ａ−３）、（Ｂ）、および（Ｃ）を総称して原料モノマーということがある）。 (Method for producing aromatic polyimide (precursor))
Polyamic acid (also referred to as polyamic acid), which is a precursor of an aromatic polyimide composed of at least one repeating unit selected from the group consisting of repeating units represented by the formulas (I) and (II), has the following formula ( A-1), (A-2), and (A-3)

(In the above formula, X represents one or more halogens selected from F, Cl, Br, and I, and R ¹ represents a hydrocarbon group having 1 to 10 carbon atoms)

(In the above formula, X represents one or more halogens selected from F, Cl, Br, and I, and R ² represents a hydrocarbon group having 1 to 10 carbon atoms)
Any one or more of the aromatic tetracarboxylic acid derivatives represented by the following formulas (B) and (C)

It is obtained by reacting at least one selected from the group consisting of an aromatic diamine represented by the following formula and its hydrochloride, sulfate, and phosphate (hereinafter, the formulas (A-1) and (A-2)): , (A-3), (B), and (C) may be collectively referred to as raw material monomers).

  As the aromatic tetracarboxylic dianhydride, various tetracarboxylic anhydrides can be copolymerized for the purpose of improving the properties of the resulting polymer. Specific examples of such aromatic tetracarboxylic acid anhydrides include 3,3 ', 4,4'-biphenyltetracarboxylic acid anhydride, 4,4'-oxydiphthalic acid anhydride, and the like.

  As the aromatic diamine, various diamines can be copolymerized for the purpose of improving the properties of the obtained polymer. Specific examples of such diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 1,8-diaminonaphthalene, 2,6-diaminonaphthalene, 2,7 -Diaminonaphthalene, 2,5-diaminopyridine, 2,6-diaminopyridine, 3,5-diaminopyridine, 3,3'-diaminobiphenyl, 3,3'-dichlorobenzidine, 3,3'-diaminodiphenyl ether, 3 4,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl ether, and the like.

  The solvent used for carrying out the polymerization is not particularly limited, but dissolves the raw materials as described above and is substantially non-reactive with them, and preferably has a specific viscosity of at least 1.0, more preferably 1. Any solvent can be used as long as it is possible to obtain two or more polymers. For example, N, N, N ′, N′-tetramethylurea (TMU), N, N-dimethylacetamide (DMAC), N, N-diethylacetamide (DEAC), N, N-dimethylpropionamide (DMPR), N, N-dimethylbutyramide (NMBA), N, N-dimethylisobutyramide (NMIB), N-methyl-2-pyrrolidinone (NMP), N-cyclohexyl-2-pyrrolidinone (NCP), N-ethylpyrrolidone-2 (NEP), N-methylcaprolactam (NMC), N, N-dimethylmethoxyacetamide, N-acetylpyrrolidine (NARP), N-acetylpiperidine, N-methylpiperidone-2 (NMPD), N, N′-dimethylethyleneurea N, N′-dimethylpropyleneurea, N, N, N ′, N′-tetramethylmalonami , It may be mentioned N- amide solvents such as acetyl pyrrolidone, p- chlorophenol, phenol, m- cresol, p- cresol, such as 2,4-di-chlorophenol phenolic solvent or mixtures thereof.

Among these, preferred solvents are N, N-dimethylacetamide (DMAC) and N-methyl-2-pyrrolidinone (NMP).
In this case, in order to increase the solubility, an appropriate amount of a known inorganic salt may be added before, during or at the end of polymerization. Examples of such inorganic salts include lithium chloride and calcium chloride.

  The polymer can be produced in the same manner as the solution polymerization of polyamide in the above-mentioned solvent obtained by dehydrating the raw material monomer. The reaction temperature at this time is 80 ° C. or lower, preferably 60 ° C. or lower. The concentration at this time is preferably about 1 to 20% by mass as the monomer concentration.

In producing the aromatic polyimide used in the present invention, trialkylsilyl chloride can be used for the purpose of increasing the degree of polymerization of the polymer.
In addition, an aliphatic or aromatic amine or a quaternary ammonium compound is used for capturing an acid such as a hydrogen halide produced when the raw material monomer of the formula (A-2) or (A-3) is used. Can be used together.

  In order to obtain the aromatic polyimide used in the present invention, the amount of the diamine represented by (B) or (C) is the mole of the aromatic dicarboxylic acid compound represented by (A) in the organic solvent. The ratio with respect to the number is preferably 0.90 to 1.10, more preferably 0.95 to 1.05, and it is preferable to form a wholly aromatic polyimide.

  In this wholly aromatic imide, it is preferable to seal the end of the polymer. When sealing with an end-capping agent, the end-capping agent includes benzoyl chloride, phthalic anhydride and its substitute, hexahydrophthalic anhydride and its substitute, succinic anhydride and its substitute, and amine component. Includes, but is not limited to, aniline and substituted products thereof.

(About molding method)
When the polymer electrolyte used in the present invention is used for a fuel cell, it is preferably in a membrane state, that is, in a film form. Although there is no restriction | limiting in particular in the manufacturing method of an aromatic polyimide membrane, The method (solution casting method) which forms into a film from a solution state can utilize preferably. Specifically, for the solution casting method, for example, the polymer solution of polyamic acid obtained by the above-described method is cast-coated on a glass plate, the solvent is removed, drying, heat treatment, and imidization are performed by molecular cyclization reaction. Proceed to obtain an aromatic polyimide film. The solvent used for film formation is not particularly limited as long as it dissolves the polymer and can be removed thereafter. N, N-dimethylacetamide, N, N-dimethylformamide, dimethyl sulfoxide, N-methyl-2- Aprotic polar solvents such as pyrrolidone and hexamethylphosphonamide, and strong acids such as polyphosphoric acid, methanesulfonic acid, sulfuric acid, and trifluoroacetic acid can be used, but are not limited thereto.

A plurality of these solvents may be used as a mixture within a possible range. As a means for improving the solubility, a solvent obtained by adding a Lewis acid such as lithium bromide, lithium chloride, or aluminum chloride to an organic solvent may be used. The polymer concentration in the solution is preferably in the range of 0.1 to 30% by mass. If it is too low, the moldability will deteriorate, and if it is too high, the workability will deteriorate.
In addition, the polymers described above may form lyotropic liquid crystals in a solvent, and it is preferable to use a polymer dope exhibiting liquid crystallinity for molding.

  In the sense of improving the mechanical properties and orientation properties of the aromatic polyimide film, for example, polyamic acid is cast and partially isoimidized with a condensing agent by the method described in JP-A-2002-30519, to give self-supporting property, It can also be preferably used to obtain an aromatic polyimide film by removing the solvent after stretching and orientation and then proceeding to imidization by drying, heat treatment, and molecular cyclization reaction.

In order to improve the conductivity, it is important to add at least one acid selected from phosphoric acid, polyphosphoric acid, sulfuric acid, and methanesulfonic acid to the molded body.
As an addition method, any method of adding to the dope in advance, adding at the time of solidification, and adding after drying can be used.

  As described above, the thickness of the solid polymer electrolyte in the form of a film is preferably 10 to 200 μm, particularly preferably 20 to 100 μm. A thickness of more than 10 μm is preferable to obtain a membrane strength that can withstand practical use, and a thickness of less than 200 μm is preferable in order to reduce membrane resistance, that is, improve power generation performance. In the case of the solution casting method, the film thickness can be controlled by the solution concentration or the coating thickness on the substrate. When the film is formed from a molten state, the film thickness can be controlled by stretching a film having a predetermined thickness obtained by a melt press method or a melt extrusion method at a predetermined magnification.

<Polymer having ion conductivity>
The polymer having ion conductivity used in the present invention is, for example, a monomer homopolymer, block copolymer, random copolymer, -SO ₃ having an ion exchange group such as —SO ₃ H. Examples thereof include perfluorocarbon sulfonic acid resins and polyether ether ketone sulfonic acid resins having ion conductivity, such as those obtained by introducing an ion exchange group such as an H group by post-treatment. In particular, the polymer having ion conductivity is preferably a perfluorocarbon sulfonic acid resin. In addition, it is preferable that the polymer which has ion conductivity used by this invention is a film | membrane state, ie, a film form, and the thickness in that case has preferable 10-200 micrometers.

<Laminated body, composite membrane (solid polymer electrolyte composition)>
The solid polymer electrolyte composition of the present invention comprises an aromatic polyimide and a polymer having ion conductivity. Even a solid polyelectrolyte composed of a composition of an aromatic polyimide and an ionic conductive polymer is a laminate of a layer composed of an aromatic polyimide and a layer composed of an ionic conductive polymer. Also good. In the case of the composition, it is preferably 1 to 800 parts by mass, preferably 3 to 300 parts by mass, and more preferably 5 to 100 parts by mass with respect to 100 parts by mass of the aromatic polyimide. In the case of a laminate, a layer made of a polymer having ion conductivity may be provided on one side or both sides of a layer made of aromatic polyimide. Examples of the lamination method include, but are not limited to, a known press method, hot press method, cast method, spin coating method, and laminate method.

  EXAMPLES Hereinafter, although an Example and a comparative example demonstrate this invention further more concretely, this invention is not limited at all by these. In addition, each measured value in the following examples is a value obtained by the following method.

[Specific viscosity]
It is a value obtained by the following formula based on the relative viscosity (η _rel ) measured at 30 ° C. with a polymer concentration of 0.5 g / dl using NMP.
η _inh = (lnη _rel ) / C
(Η _inh is the specific viscosity [dl / g], η _rel is the relative viscosity, and C is the polymer concentration [g / dl])

[Ion conductivity measurement]
The solid polymer electrolyte composition (membrane) of the present invention was measured for impedance in the thickness direction of the membrane in the frequency range of 0.1 Hz to 65 kHz using an electrochemical impedance measuring device (manufactured by Solartron, SI1287), and ionic conductivity Was measured. In the above measurement, the solid polymer electrolyte composition (laminate) was stored at 80 ° C. in a 90% RH atmosphere.

[Oxidation resistance test]
A Fenton reagent (containing 40 ppm of iron) heated to 60 ° C. consisting of adding 1.9 mg of iron sulfate heptahydrate to 20 ml of 30% hydrogen peroxide solution, the solid polymer electrolyte composition (laminate) of the present invention. The time until the electrolyte membrane was dissolved in the Fenton reagent was determined.

[Measurement method of phosphorus atom content]
The sample was placed in a wet decomposition vessel with reflux cooling, and after adding concentrated sulfuric acid, while heating after adding concentrated sulfuric acid, nitric acid was gradually added dropwise to prevent the sample from scattering and the organic matter was completely decomposed. After standing to cool, pure water was added and the volume was fixed in a white transparent glass container, and phosphorus atoms were quantified by ICP emission spectrometry.

[Reference Example 1] (Polymer polymerization)
Under a nitrogen stream, 11.1 parts by mass of calcium chloride was added to the flask and dried at 250 ° C. for 1 hour. After the temperature in the flask was returned to room temperature, 350 parts by mass of N-methyl-2-pyrrolidinone (NMP) , And 5 parts by weight of 5 (6) -amino-2- (4-aminophenyl) benzimidazole (cas. Reg. No. 7621-86-5). This solution was kept at 0 ° C. by external cooling, and after stirring for 1 hour, 7.74 parts by mass of diethyl 2,5-bis (chlorocarbonyl) terephthalate was added and reacted at 0 ° C. for 5 hours and at room temperature for 40 hours. An acid polymer dope was obtained. The specific viscosity of the obtained polymer was 1.5 [dl / g].

[Reference Example 2] (Cast film production)
The polymer dope obtained in Reference Example 1 was developed on a glass with a doctor knife and immersed in NMP: water = 30: 70 solvent for 1 hour to obtain a self-supporting film. The obtained film was heated at 80 ° C. for 5 minutes, 200 ° C. for 10 minutes, 250 ° C. for 10 minutes, 350 ° C. for 10 minutes, and 400 ° C. for 10 minutes to obtain a wholly aromatic polyimide film (thickness 25 μm). The obtained membrane was immersed in a methanol solution containing 50% by mass of phosphoric acid for 12 hours to obtain a solid electrolyte membrane having a phosphorus atom content of 3.5% by mass (11% by mass in terms of phosphoric acid).

[Example 1] (Preparation of laminate (solid polymer electrolyte composition))
A laminate (solid polymer electrolyte composition) was prepared by sandwiching both sides of a film obtained in Reference Example 2 with a Nafion film made by Du Pont having a film thickness of 170 μm, and its ionic conductivity and oxidation resistance were measured. . The measurement results are shown in Table 1.

Claims (4)

Formulas (I) and (II) below

100 parts by mass of an aromatic polyimide composed of at least one repeating unit selected from the group consisting of repeating units represented by: at least one acid selected from phosphoric acid, polyphosphoric acid, sulfuric acid, and methanesulfonic acid 0.1 A solid polymer electrolyte composition comprising a solid polymer electrolyte comprising ˜100 parts by mass and a polymer having ion conductivity.   The solid polymer electrolyte composition according to claim 1, wherein the solid polymer electrolyte is in the form of a film having a thickness of 10 to 200 μm.   The solid polymer electrolyte composition according to claim 1 or 2, wherein the polymer having ion conductivity is a perfluorocarbon sulfonic acid resin.   The solid polymer electrolyte composition according to any one of claims 1 to 3, wherein the solid polymer electrolyte and the polymer having ion conductivity are each in the form of a film and are a laminate thereof.