JP2010009851A - Electrolyte membrane for fuel cell - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrolyte membrane for a fuel cell which maintains high proton conductivity and in which dimension changes caused by income and outgo of water can be suppressed. <P>SOLUTION: The electrolyte membrane for the fuel cell contains a proton conductive material in which a first electrolyte resin is filled in inorganic particulates of hollow shape having a through-hole on the surface and a second electrolyte resin. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electrolyte membrane for a fuel cell that can maintain high proton conductivity and suppress dimensional changes due to water balance.

  A fuel cell directly converts chemical energy into electrical energy by supplying fuel and an oxidant to two electrically connected electrodes and causing the fuel to be oxidized electrochemically. Unlike thermal power generation, fuel cells are not subject to the Carnot cycle, and thus exhibit high energy conversion efficiency. A fuel cell is usually formed by laminating a plurality of single cells having a basic structure of a membrane / electrode assembly in which an electrolyte membrane is sandwiched between a pair of electrodes. Among them, a solid polymer electrolyte fuel cell using a solid polymer electrolyte membrane as an electrolyte membrane has advantages such as easy miniaturization and operation at a low temperature. It is attracting attention as a power source for the body.

In the solid polymer electrolyte fuel cell, when hydrogen is used as the fuel, the reaction of the formula (1) proceeds at the anode (fuel electrode).
_{^{H 2 → 2H + + 2e -}} ... (1)
The electrons generated by the equation (1) reach the cathode (oxidant electrode) after working with an external load via an external circuit. Then, the proton generated in the formula (1) moves by electroosmosis from the anode side to the cathode side in the solid polymer electrolyte membrane in a state of being hydrated with water.

Further, when oxygen is used as the oxidizing agent, the reaction of the formula (2) proceeds at the cathode.
_{^{2H + + (1/2) O 2}} + 2e - → H 2 O ... (2)
The water produced at the cathode mainly passes through the gas diffusion layer and is discharged to the outside. As described above, the fuel cell is a clean power generation device that has no emissions other than water.

  A polymer electrolyte membrane operable in a temperature range of a commonly used solid polymer electrolyte fuel cell is composed of an organic polymer type proton conductive material having a polymer as a basic skeleton or main chain. Problems with the proton-conducting material include dimensional changes such as expansion and contraction of the membrane during water absorption and drainage, and creep or thermal contraction due to heat. Under the operating environment of fuel cells, it is known that the balance of water and heat changes more frequently depending on the load and the external environment, but the accompanying dimensional change of the membrane is important to shorten the life of the electrolyte membrane. This is a problem and is also a very difficult problem for the current organic polymer type proton conductive material.

  On the other hand, an electrolyte membrane combining an inorganic proton conductor and a non-proton conductive polymer, which is different from the electrolyte membrane using the organic polymer type proton conductive material, has been proposed. Patent Document 1 is typified by tungsten oxide or tin oxide hydrate in order to maintain stable proton conductivity and mechanical strength even at a temperature of 100 ° C. or more, which is the heat resistance limit of conventional fluorine-based electrolyte membranes. A proton conducting membrane containing a metal oxide hydrate and an aprotic conducting polymer is disclosed.

Japanese Patent Laid-Open No. 2002-289051

  When the proton conductive membrane disclosed in Patent Document 1 is used as an electrolyte membrane for a fuel cell, the proton conductivity is stable under high temperature and low humidification conditions. However, in comparison with Nafion, which is an organic polymer that has been used in the past, the value of proton conductivity itself, in particular, the proton conductivity in the operating environment (temperature, humidity) with the highest power generation efficiency for fuel cells is not sufficient. There wasn't. Further, the invention of Patent Document 1 does not pay attention to the dimensional stability of the electrolyte membrane.

As a result of intensive studies on the proton conductive material, the present inventors have developed a material in which hollow inorganic fine particles having through holes on the surface are filled with an electrolyte resin, and the material impairs mechanical properties and shape. It has been found that high proton conductivity is exhibited without any patent application (Japanese Patent Application No. 2007-246203).
In the above patent application, hollow inorganic fine particles having through holes on the surface are mixed with a monomer having a sulfonic acid group or a precursor group thereof, and the monomer is filled in the inorganic fine particles under reduced pressure. A method for producing a proton conductive material for polymerizing the monomer is also proposed. According to this method, the polymer is filled into the inorganic fine particles by the subsequent polymerization reaction by a simple operation of filling the inorganic fine particles into the inorganic fine particles from the through holes of the inorganic fine particles, without impairing the mechanical properties and shape. A proton conductive material capable of improving proton conductivity can be provided.

  The present inventors have further studied the above proton conductive material and found an electrolyte membrane for a fuel cell exhibiting high proton conductivity and dimensional stability. That is, the present invention has been accomplished through the above-described research, and provides an electrolyte membrane that can maintain high proton conductivity and suppress dimensional changes due to changes in the balance of water and heat. With the goal.

  An electrolyte membrane for a fuel cell according to the present invention includes a proton conductive material in which hollow inorganic fine particles having through holes on the surface are filled with a first electrolyte resin, and a second electrolyte resin. .

The electrolyte membrane for a fuel cell having such a configuration is the first electrolyte filled in a cavity of the inorganic fine particles, which is an outer shell of the proton conductive material, in the proton conductive material contained in the electrolyte membrane. Since the myriad proton conductive groups of the resin are exposed from the through-holes on the surface of the inorganic fine particles, the proton conductivity is high, and the first electrolyte resin is confined in the inorganic fine particles having a fixed particle diameter. Therefore, since the proton conductive material does not swell and contract, no dimensional change occurs due to the balance of water and heat.
Further, the electrolyte membrane for a fuel cell of the present invention can be used even if it is normally in a state of high fluidity such as introducing a large amount of proton conductive groups into the structure of the first electrolyte resin. In the invention, since it is held in the cavity of the inorganic fine particles, it is possible to achieve improvement in both shape retention and proton conductivity in the proton conductive material.
Furthermore, the electrolyte membrane for fuel cells of the present invention can further improve proton conductivity by using the second electrolyte resin as a binder resin for forming a membrane. In the electrolyte membrane for a fuel cell according to the present invention, since the second electrolyte resin is not limited to a specific electrolyte resin, the degree of freedom in selecting a resin is high. By appropriately selecting the type of the resin, the fuel cell The most suitable electrolyte membrane can be obtained according to the purpose and purpose.

  In the electrolyte membrane for a fuel cell of the present invention, when the proton conductive material and the second electrolyte resin are contained in 100 parts by weight of the total of these two components, the proton conductive material is 60-5. It is preferable that the second electrolyte resin is 40 to 95 parts by weight.

  The electrolyte membrane for a fuel cell having such a configuration can sufficiently have a film forming property for forming an electrolyte membrane while maintaining high proton conductivity and shape retention.

  In the fuel cell electrolyte membrane of the present invention, it is preferable that the first electrolyte resin in the inorganic fine particles has a Si—O skeleton.

  The electrolyte membrane for a fuel cell having such a configuration is obtained by filling the inorganic fine particles with a monomer serving as a raw material for the first electrolyte resin in the proton conductive material contained in the electrolyte membrane and polymerizing the monomer. Since the polymerization reaction can be easily caused when the electrolyte resin is synthesized, the production is easy. In the electrolyte membrane for a fuel cell of the present invention, since the monomer has a high affinity with the inorganic fine particles and can be easily filled, the synthesis of the proton conductive material contained in the electrolyte membrane can be performed quickly. It can be carried out.

In the fuel cell electrolyte membrane of the present invention, the inorganic fine particles are preferably SiO ₂ .

The electrolyte membrane for a fuel cell having such a structure has mechanical characteristics because the inorganic fine particles, which are the outer shells of the proton conductive material, are formed of SiO ₂ which is a chemically stable and rigid inorganic material. And can maintain a stable shape without contraction / expansion due to the balance of water and heat.

  In the electrolyte membrane for a fuel cell of the present invention, the proton conductive material preferably has an ion exchange capacity larger than the ion exchange capacity of the inorganic fine particles.

  The electrolyte membrane for fuel cells having such a configuration can ensure proton conductivity higher than that of the inorganic fine particles by filling the first electrolyte resin into the inorganic fine particles.

  In the fuel cell electrolyte membrane of the present invention, the proton conductive material preferably has an ion exchange capacity of 0.5 meq / g or more.

  The fuel cell electrolyte membrane having such a configuration can have sufficient proton conductivity.

  The electrolyte membrane for fuel cells of the present invention preferably has an ion exchange capacity larger than the ion exchange capacity of the electrolyte membrane using only the second electrolyte resin.

  The electrolyte membrane for a fuel cell having such a configuration has a proton conductivity higher than that of the second electrolyte resin itself by including the proton conductive material in which the first electrolyte resin is filled in the inorganic fine particles. can do.

  In the fuel cell electrolyte membrane of the present invention, the proton conductive material preferably has an average particle size of 0.05 to 10 μm.

  The electrolyte membrane for a fuel cell having such a configuration can be formed with an appropriate thickness.

  In the electrolyte membrane for a fuel cell according to the present invention, the second electrolyte resin is preferably a perfluorocarbon sulfonic acid polymer.

  Since the electrolyte membrane for fuel cells having such a configuration contains a perfluorocarbon sulfonic acid polymer having high proton conductivity, proton conductivity can be further improved.

According to the present invention, in the proton conductive material contained in the electrolyte membrane, the countless proton conductivity of the first electrolyte resin filled in the cavity of the inorganic fine particles, which is the outer shell of the proton conductive material. Since the group is exposed from the through-holes on the surface of the inorganic fine particles, the proton conductivity is high, and the first electrolyte resin is confined in the inorganic fine particles having a fixed particle size. Since there is no swelling and shrinkage of the conductive material, there is no dimensional change due to water and heat balance.
Further, according to the present invention, even if the fluidity is normally high, such as introducing a large amount of proton conductive groups into the structure of the first electrolyte resin, Since it is held in the cavities of the inorganic fine particles, it is possible to achieve both improvement in shape retention and proton conductivity in the proton conductive material.
Furthermore, according to the present invention, proton conductivity can be further improved by using the second electrolyte resin as a binder resin for film formation. Further, according to the present invention, since the second electrolyte resin is not limited to a specific electrolyte resin, the degree of freedom in resin selection is high, and the use / purpose of the fuel cell can be selected by appropriately selecting the type of the resin. Therefore, an optimum electrolyte membrane can be obtained.

  An electrolyte membrane for a fuel cell according to the present invention includes a proton conductive material in which hollow inorganic fine particles having through holes on the surface are filled with a first electrolyte resin, and a second electrolyte resin. .

  Hereinafter, the proton conductive material contained in the fuel cell electrolyte membrane of the present invention will be described in detail with reference to the drawings. FIG. 1 is a view showing a typical example of a proton conductive material contained in an electrolyte membrane for a fuel cell according to the present invention, and is a view obtained by cutting a particulate proton conductive material. The lower right circle is an enlarged view of the cross section, and is a diagram schematically showing the structural formula of the first electrolyte resin. The broken line connecting the silicon atom and the sulfonic acid group in the lower right circle represents an alkyl chain. The proton conductive material 100 includes a first electrolyte resin 1 and inorganic fine particles 2, and the hollow inorganic fine particles 2 are filled with the electrolyte resin 1. The inorganic fine particles 2 have innumerable through holes, and the electrolyte resin 1 is exposed on the particle surface through the through holes.

  As in the structural formula schematically shown in the lower right circle of FIG. 1, the electrolyte resin 1 preferably has a Si—O skeleton. The electrolyte resin 1 has a proton conductive group such as a sulfonic acid group. The sulfonic acid group is preferably exposed on the surface of the proton conductive material 100 through the through holes of the inorganic fine particles 2 as shown in the lower right circle of FIG.

A typical example of the electrolyte resin having a Si—O skeleton is a polymer in which a Si—O skeleton is formed by polymerizing a monomer. Such a polymer can easily cause a polymerization reaction when the inorganic fine particles are filled with a monomer as a raw material of the electrolyte resin and polymerized to synthesize the electrolyte resin. Further, since the monomer has a high affinity with the inorganic fine particles and can be easily filled, the proton conductive material can be synthesized quickly. Furthermore, since the electrolyte resin has a strong polymer chain called a Si—O skeleton, proton conductive groups do not leak out of the proton conductive material.
The polymerization of the monomer here includes addition polymerization and polycondensation. In addition, a resin that is a polymer having a large molecular weight from the beginning cannot be used because it is difficult to fill at the time of decompression. Therefore, a monomer can be used for filling.

As the monomer, a compound that is a repeating unit of the electrolyte resin to be filled in the cavity of the hollow inorganic fine particles is used.
For example, when it is desired to fill inorganic fine particles with perfluorocarbon sulfonic acid conventionally used in the field of polymer electrolyte fuel cells, a monomer that forms a fluorocarbon skeleton such as fluoroethylene can be used.
When it is desired to fill the inorganic fine particles with an electrolyte resin having a Si—O skeleton, a hydrocarbonoxysilane compound and / or a silanol compound having a sulfonic acid group or a precursor group thereof can be used. The hydrocarbonoxysilane compound that can be used here is a sulfonic acid group or a precursor group thereof bonded directly or indirectly to a silicon atom, and a hydrocarbonoxy group that may contain a different atom is bonded to the same silicon atom. A compound having a bonded structure. The hydrocarbonoxy group is a group in which an oxygen atom is bonded to an aliphatic or aromatic hydrocarbon group such as an alkoxy group or an aryloxy group, and the oxygen atom is bonded to a silicon atom. is there. The hydrocarbonoxy group may contain a hetero atom. When the sulfonic acid group or its precursor group is indirectly bonded to the silicon atom, it may be bonded via, for example, an aliphatic or aromatic hydrocarbon group, and the hydrocarbon group is bonded to a hetero atom. May be included. The silanol compound that can be used here is a compound having a structure in which a sulfonic acid group or a precursor group thereof is bonded directly or indirectly to a silicon atom and a hydroxyl group is bonded to the same silicon atom.
Examples of the hydrocarbonoxysilane compound and / or the silanol compound include, for example, a Si atom, a sulfonic acid hydrocarbon group (which may contain a different atom), a hydroxyl group (—OH) and / or an alkoxy group or an aryl group. A silicon compound bonded to an oxy group (which may contain a different atom) is preferably used. More specifically, those having a structure represented by the following formula (1), formula (2) and formula (3) can be mentioned.

（式中、Ｒ^１は炭素数１〜４の脂肪族炭化水素基又は炭素数６〜１０の芳香族炭化水素基であり、且つ、ｎ＝１〜４である。）

(In the formula, R ¹ is an aliphatic hydrocarbon group having 1 to 4 carbon atoms or an aromatic hydrocarbon group having 6 to 10 carbon atoms, and n = 1 to 4).

  As the monomer having a sulfonic acid group precursor group, a compound that can be derived from the above-described monomer having a sulfonic acid group can be used. For example, in the above formulas (1), (2), and (3) Examples of the corresponding monomer include those having a structure represented by the following formula (4), formula (5), and formula (6).

（式中、Ｒ^２〜Ｒ^９は互いに独立であり、水素原子、異種原子を含んでいてもよく好ましくは炭素数１〜４の脂肪族炭化水素基、及び異種原子を含んでいてもよく好ましくは炭素数６〜１０の芳香族炭化水素基からなる群から選択される官能基である。また、ｎ＝１〜４である。Ｘ^１〜Ｘ^４は互いに独立であり、チオール基、スルフィニル基、スルホン酸フルオリド、スルホン酸クロリド、スルホン酸ブロミド、スルホン酸ヨージド、スルホン酸リチウム、スルホン酸カリウム又はスルホン酸ナトリウム等のスルホン酸基の前駆体基のうちのいずれかから選択される官能基である。）

(In the formula, R ^{2 to} R ⁹ are independent of each other, and may contain a hydrogen atom, a heteroatom, or preferably an aliphatic hydrocarbon group having 1 to 4 carbon atoms and a heteroatom. Is a functional group selected from the group consisting of aromatic hydrocarbon groups having 6 to 10 carbon atoms, and n = 1 to ^4. X ^{1 to} X ⁴ are independent of each other, and are a thiol group or a sulfinyl group. , Sulfonic acid fluoride, sulfonic acid chloride, sulfonic acid bromide, sulfonic acid iodide, lithium sulfonic acid, potassium sulfonate, sodium sulfonate, and other functional groups selected from precursor groups of sulfonic acid groups .)

  In synthesizing the electrolyte resin, two or more monomers may be used.

As a method for converting a precursor group of a sulfonic acid group into a sulfonic acid group, for example, when the precursor group is a thiol group or a sulfinyl group, it is converted into a sulfonic acid group by adding an oxidizing agent such as hydrogen peroxide. Or when the precursor group is sulfonic acid fluoride, sulfonic acid chloride, sulfonic acid bromide, sulfonic acid iodide, lithium sulfonic acid, potassium sulfonic acid, sodium sulfonic acid or the like, an acid such as hydrochloric acid or sulfuric acid, or It can be converted to a sulfonic acid group by adding a base such as an aqueous sodium hydroxide solution.
Further, the precursor group of the sulfonic acid group is not limited to the above, and includes, for example, the case where X ^{1 to} X ⁴ in the above formulas (4) to (6) are terminal olefins. In this case, it can be converted into an alkyl group having a sulfonic acid group at the terminal by treating with sulfur trioxide and then treating with a base.

  In addition, the electrolyte resin 1 may be a polymer electrolyte usually used in a fuel cell. Polyelectrolyte here refers to polyether polymer ketone, polyether ketone, polyether sulfone, polyphenylene sulfide, in addition to fluorine-based polymer electrolytes such as perfluorocarbon sulfonic acid resin represented by Nafion (trade name). Protonic acid groups such as sulfonic acid groups, carboxylic acid groups, phosphoric acid groups, and boronic acid groups on hydrocarbon polymers such as engineering plastics such as polyphenylene ether and polyparaphenylene, and general-purpose plastics such as polyethylene, polypropylene, and polystyrene ( Hydrocarbon polymer electrolytes into which proton conductive groups) have been introduced.

  The inorganic fine particles 2 are required to have a sufficient filling amount inside the particles, and have a low internal resistance to flow and are easy to be filled when the monomer as the raw material of the electrolyte resin 1 is filled. It is not necessarily limited to a complete hollow body, and may have some internal structures in the form of partitions on the pillars.

  In addition, the through-holes on the surface of the inorganic fine particles 2 have a low resistance to flow when the monomer as the raw material of the electrolyte resin 1 is filled, and the monomer is addition-polymerized or polycondensed inside the particles. It is required that the electrolyte resin produced in this way has a size in an appropriate range that does not easily flow out.

In order to satisfy the properties of the inside of the inorganic fine particles 2 and the through holes as described above, the inorganic fine particles 2 are preferably SiO ₂ . Since the proton conductive material 100 has a rigid shell made of SiO _2, it has an advantage of excellent mechanical properties.

As the inorganic fine particles, it is preferable to use microcapsules (trade name: Washin microcapsules) whose main component is SiO ₂ , but other inorganic fine particle porous hollow bodies may be used. Specifically, in addition to the above SiO ₂ , silsesoxane, zeolite, and the like can be given. However, mesoporous silica does not correspond to the hollow inorganic fine particles used in the present invention because the first electrolyte resin easily flows out from the inside of the particles and it is difficult to hold the first electrolyte resin.
As a method for producing inorganic fine particles, styrene monomer is polymerized in the presence of a vinyl monomer having a cationic surfactant group to obtain polystyrene fine particles having an ionic group on the surface. The polystyrene fine particles are subjected to a hydrolytic condensation reaction of tetraethoxysilane to form silica on the surfaces of the polystyrene fine particles. Next, hollow silica microcapsules are obtained by dissolving and removing polystyrene with a solvent.
The microcapsules must be treated with an acid such as hydrochloric acid prior to the production of the proton conductive material to remove impurities in advance.

The proton conductive material 100 preferably has an ion exchange capacity larger than the ion exchange capacity of the inorganic fine particles 2 itself, and the ion exchange capacity of the proton conductive material 100 is 0.5 meq / g or more. Is preferred. If the ion exchange capacity of the proton conductive material 100 is smaller than the ion exchange capacity of the inorganic fine particles 2, no improvement in ion conductivity can be expected even if an ion conductive group is added. Further, if the proton exchange capacity of the proton conductive material 100 is less than 0.5 meq / g, sufficient power generation efficiency cannot be expected when the proton conductive material 100 is used for an electrolyte membrane of a fuel cell. .
Therefore, the proton conductive material having the ion exchange capacity as described above can ensure proton conductivity higher than the inorganic fine particles by filling the first electrolyte resin in the inorganic fine particles. In addition, when used for an electrolyte membrane of a fuel cell, sufficient proton conductivity can be exhibited.

The proton conductive material 100 preferably has an average particle size of 0.05 to 10 μm.
If the average particle size of the proton conductive material 100 is less than 0.05 μm, it is not large enough to hold a sufficiently filled electrolyte resin. Conversely, when the average particle size of the proton conductive material 100 exceeds 10 μm, it cannot be used for an electrolyte membrane having an appropriate thickness.
More preferably, from the viewpoint of avoiding particle destruction, the bulk density of the inorganic fine particles 2 may be 5% or more of the true density of the inorganic fine particles 2.

  As a filling condition of the above-mentioned monomer into the inorganic fine particles, it is preferable to carry out 1 to 200 mmHg, 20 to 100 ° C., and 1 to 6 hours as the degree of vacuum. Moreover, as polymerization conditions in the inorganic fine particles of the monomer, it is preferable to perform heat treatment at 80 to 150 ° C. for 2 to 24 hours under reduced pressure.

The electrolyte membrane for a fuel cell of the present invention contains a second electrolyte resin together with the proton conductive material described above. Since the second electrolyte resin is not limited to a specific resin, the degree of freedom in resin selection is high.
An optimal electrolyte membrane can be obtained by appropriately selecting the type of the second electrolyte resin according to the use and purpose of the fuel cell. For example, the above-described fluorine-based polymer electrolyte resin, hydrocarbon-based polymer electrolyte resin, or the like can be used. In addition, a plurality of them can be mixed with the proton conductive material and used for the electrolyte membrane.

  The electrolyte membrane for a fuel cell of the present invention preferably has an ion exchange capacity that is larger than the ion exchange capacity of the electrolyte membrane using only the second electrolyte resin. If the ion exchange capacity of the fuel cell electrolyte membrane of the present invention is smaller than the ion exchange capacity of the electrolyte membrane using only the second electrolyte resin, the above proton conductive material is added and mixed. Even so, it is not possible to improve the ion conductivity.

  Of the electrolyte resins described above, the second electrolyte resin is preferably a perfluorocarbon sulfonic acid polymer. This is because the proton conductivity of the electrolyte membrane of the present invention can be further improved because it contains a perfluorocarbon sulfonic acid polymer having high proton conductivity.

When the content of the proton conductive material and the second electrolyte resin is 100 parts by weight of the total of these two components, the proton conductive material is 60 to 5 parts by weight, and the second electrolyte resin is It is preferable that it is 40-95 weight part. When the proton conductive material is less than 5 parts by weight, it is difficult to obtain an electrolyte membrane having high proton conductivity, which is an effect of the present invention. Moreover, when there is less said 2nd electrolyte resin than 40 weight part, the film forming property for forming an electrolyte membrane may become inadequate.
More preferably, the proton conductive material is 40 to 10 parts by weight and the second electrolyte resin is 60 to 90 parts by weight, and the proton conductive material is 30 to 15 parts by weight, and the second electrolyte. Most preferably, the resin is 70 to 85 parts by weight.

As a method for forming an electrolyte membrane, after dissolving the second electrolyte resin in an appropriate solvent, the proton conductive material is added and stirred well, and the solution is spread almost evenly on a smooth surface such as a glass plate. Thereafter, drying is preferably performed under an inert gas stream such as nitrogen gas or argon gas. In addition, when a solvent remains in a film | membrane, high temperature vacuum drying can also be performed. At this time, as a solvent, dimethyl sulfoxide (DMSO), N-methylpyrrolidone (NMP), dimethylacetamide (DMA), or a mixed solvent thereof can be used.
In addition to this, a conventionally used method can be employed as a method for forming the electrolyte membrane, and the main methods include a melt extrusion method, a doctor blade method, and the like.

According to the present invention, in the proton conductive material contained in the electrolyte membrane of the present invention, the countless proton conductivity of the first electrolyte resin filled in the cavity of the inorganic fine particles, which is the outer shell of the proton conductive material. Since the group is exposed from the through-holes on the surface of the inorganic fine particles, the proton conductivity is high, and the first electrolyte resin is confined in the inorganic fine particles having a fixed particle size. Since there is no swelling and shrinkage, there is no dimensional change due to water and heat balance.
Further, according to the present invention, the inorganic fine particles are used in the present invention even if the fluidity is normally high, such as introducing a large amount of proton conductive groups into the structure of the first electrolyte resin. Therefore, both shape retention and proton conductivity can be improved in the proton conductive material.
Furthermore, according to the present invention, proton conductivity can be further improved by using the second electrolyte resin as a binder resin for film formation. Further, according to the present invention, since the second electrolyte resin is not limited to a specific electrolyte resin, there is a high degree of freedom in resin selection, and by appropriately selecting the type of resin, the second electrolyte resin can be adapted to the application and purpose of the fuel cell. And an optimum electrolyte membrane can be obtained.

1. Pretreatment of inorganic fine particles 10.0 g of microcapsules (trade name: Washin Microcapsule) as hollow inorganic fine particles having through-holes on the surface were added to 200 mL of 0.1N hydrochloric acid and stirred for one day. Thereafter, the mixture was allowed to stand to precipitate microcapsules, and the supernatant was removed. After adding 200 mL of distilled water and stirring well, it was allowed to stand and the supernatant was removed in the same manner. Thus, addition of distilled water, stirring, and removal of the supernatant were repeated until pH = 7.
Finally, the remaining precipitate was dried under reduced pressure at 120 ° C. under vacuum for 6 hours.

2. Proton conductive material production [Synthesis example]
0.10 g of the pre-treated microcapsules described above was added to 1.54 g of a 3- (trihydroxysilyl) -1-propanesulfonic acid solution (manufactured by Gelest) having a concentration of 30 wt% as a monomer having a sulfonic acid group. Then, pressure reduction (100 mmHg, 25 degreeC, 2 hours) was performed in order to fill the said microcapsule with the said monomer. The pressure was further reduced for 3 hours to remove moisture. Subsequently, the monomer was polymerized by heat treatment at 80 ° C. for 12 hours under reduced pressure. Then, after homogenizing using a mortar, it wash | cleaned 3 times with ion-exchange water, and dried under reduced pressure (120 degreeC, 6 hours). As a result, 0.36 g of a proton conductive material which was a white solid was obtained.

3. Production of electrolyte membrane [Example 1]
Under a nitrogen flask, 0.10 g (75 parts by weight) of Nafion (trade name), which is a kind of perfluorocarbon sulfonic acid polymer, was dissolved in 1.5 mL of DMA, and the proton conductive material synthesized in the above synthesis example. 033 g (25 parts by weight, average particle size 3 to 5 μm) was added, and the mixture was stirred at room temperature for 1 day under nitrogen.
After confirming that it was well dispersed visually, stirring was terminated and the solution was spread almost uniformly on the glass plate. When the solution on the glass plate was allowed to stand at 60 ° C. for 24 hours under a nitrogen stream, a wet gel film was obtained. In order to remove the residual solvent in the wet gel film, it was dried under reduced pressure at 120 ° C. under vacuum for 12 hours to obtain a translucent and flexible electrolyte film.

[Example 2]
Under a nitrogen flask, 0.10 g (83 parts by weight) of Nafion (trade name), which is a kind of perfluorocarbon sulfonic acid polymer, was dissolved in 1.5 mL of DMA, and the proton-conductive material synthesized in the above synthesis example was obtained in a 0. 020 g (17 parts by weight, average particle size 3 to 5 μm) was added, and the mixture was stirred at room temperature for 1 day under nitrogen. The subsequent casting method and drying method of the electrolyte membrane are the same as in Example 1.

[Example 3]
In an eggplant flask, 0.10 g (91 parts by weight) of Nafion (trade name), which is a kind of perfluorocarbon sulfonic acid polymer, was dissolved in 1.5 mL of DMA, and the proton conductive material synthesized in the above synthesis example was added in an oxygen flask. 010 g (9 parts by weight, average particle size 3 to 5 μm) was added, and the mixture was stirred at room temperature for 1 day under nitrogen. The subsequent casting method and drying method of the electrolyte membrane are the same as in Example 1.

4). Measurement and Evaluation of Proton Conductivity of Electrolyte Membrane Proton conductivity was measured by measuring AC impedance of the electrolyte membrane of Example 1 and a Nafion membrane which is a kind of perfluorocarbon sulfonic acid polymer electrolyte membrane. The electrolyte membrane and Nafion membrane of the present invention were allowed to stand for 3 hours at a relative humidity of 95% or 80% and 80 ° C., and the impedance was measured after each was in an equilibrium state.

FIG. 2 is a bar graph showing the proton conductivity of the electrolyte membrane for fuel cells of the present invention at a relative humidity of 95% or 80%, showing the result of comparison with the Nafion membrane.
The proton conductivity (left bar graph) of the fuel cell electrolyte membrane of the present invention at 95% relative humidity is 0.09 (S / cm) or more, and the proton conductivity of the Nafion membrane at the same relative humidity (two from the left). It was found that the proton conductivity was more than double that of the second bar graph) less than 0.04 (S / cm).
In addition, the electrolyte membrane for a fuel cell of the present invention has a higher proton than 0.035 (S / cm) (third bar graph from the left) and Nafion membrane (right bar graph) even at a relative humidity of 80%. It was found to show conductivity.

5). Measurement and Evaluation of Dimensional Change of Electrolyte Membrane Two of the electrolyte membrane of Example 1 and a Nafion membrane, which is a kind of perfluorocarbon sulfonic acid polymer electrolyte membrane, molded into a length of 10 mm, a width of 10 mm, and a thickness of 0.05 mm Prepared one by one. The electrolyte membrane of Example 1 and the Nafion membrane were allowed to stand one by one under condition 1 (80 ° C., in water) and one by one under condition 2 (80 ° C., under atmospheric pressure). After 30 minutes, the dimension (length in the planar direction) of each film was measured with a micrometer.
The difference between the dimension in condition 1 and the dimension in condition 2 is defined as the dimensional change amount, and the value obtained by dividing the dimensional change amount by the initial dimension of the film before being left under condition 1 or condition 2 is the dimensional change rate. It was.

  Table 1 is a table showing the dimensional change rate in the surface direction of the electrolyte membrane for fuel cells of the present invention, and is a table showing the result of comparison with the Nafion membrane. The dimensional change rate of the electrolyte membrane of the present invention remained around 2%. This shows that significant dimensional change suppression was achieved, as is clear when compared with a Nafion membrane that exhibited a dimensional change rate of nearly 20%.

6). Summary From the above measurement results, it has been clarified that the electrolyte membrane of the present invention exhibits higher proton conductivity and shape retention than the perfluorocarbon sulfonic acid polymer electrolyte membrane of the prior art.

It is the figure which showed the typical example of the proton-conductive material contained in the electrolyte membrane for fuel cells of this invention, and is the figure which cut the particulate proton-conductive material into pieces. It is the bar graph which showed the proton conductivity in 95% or 80% of relative humidity of the electrolyte membrane for fuel cells of this invention, and is the figure which showed the result compared with the Nafion membrane.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... 1st electrolyte resin 2 ... Inorganic fine particle 100 ... Proton conductive material

Claims (9)

  A fuel cell electrolyte membrane, comprising: a proton conductive material in which hollow inorganic fine particles having through holes on the surface are filled with a first electrolyte resin; and a second electrolyte resin.   When the content of the proton conductive material and the second electrolyte resin is 100 parts by weight of the total of these two components, the proton conductive material is 60 to 5 parts by weight, and the second electrolyte resin is The electrolyte membrane for a fuel cell according to claim 1, wherein the electrolyte membrane is 40 to 95 parts by weight.   The electrolyte membrane for a fuel cell according to claim 1 or 2, wherein the first electrolyte resin in the inorganic fine particles has a Si-O skeleton. The electrolyte membrane for a fuel cell according to any one of claims 1 to 3, wherein the inorganic fine particles are SiO ₂ .   The electrolyte membrane for a fuel cell according to any one of claims 1 to 4, wherein the proton conductive material has an ion exchange capacity larger than that of the inorganic fine particles.   The electrolyte membrane for a fuel cell according to any one of claims 1 to 5, wherein an ion exchange capacity of the proton conductive material is 0.5 meq / g or more.   The electrolyte membrane for a fuel cell according to any one of claims 1 to 6, which has an ion exchange capacity larger than an ion exchange capacity of an electrolyte membrane using only the second electrolyte resin.   The electrolyte membrane for a fuel cell according to any one of claims 1 to 7, wherein the proton conductive material has an average particle size of 0.05 to 10 µm.   The electrolyte membrane for a fuel cell according to any one of claims 1 to 8, wherein the second electrolyte resin is a perfluorocarbon sulfonic acid polymer.

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