Fuel cells, electrolyte membranes and subgaskets

Abstract

To easily repair defects inside a fuel cell.SOLUTION: A fuel cell (100) includes a membrane electrode assembly (3), and a sub-gasket (5), and the membrane electrode assembly (3) includes an electrolyte membrane (1) and a pair of electrodes (2) on both sides of the electrolyte membrane (1). The electrolyte membrane (1), the sub-gasket (5), or both contain a self-healing material, and the self-healing material is a polymer containing a self-healing unit.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a fuel cell, an electrolyte membrane, and a subgasket. [Background technology]

[0002] A polymer electrolyte fuel cell generates electricity by chemically reacting hydrogen gas and oxygen gas supplied as fuel gases. Generally, a polymer electrolyte fuel cell has a structure in which a membrane electrode assembly, which performs the chemical reaction, is sandwiched between a pair of separators.

[0003] A membrane electrode assembly has an electrolyte membrane disposed between a pair of electrodes. The electrolyte membrane uses a polymer electrolyte, and defects such as pinholes or cracks may occur during the manufacturing process or after long-term use after manufacturing. Since defects affect power generation performance, a method has been proposed for repairing pinholes by causing a sol-gel phase transition of a gelling agent encapsulated in the electrolyte membrane (see Patent Document 1). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-042531 Summary of the Invention [Problem to be solved by the invention]

[0005] When using the gelling agent, the temperature is controlled to a predetermined temperature for the sol-gel phase transition. Since it is difficult to detect defects in the electrolyte membrane inside a sealed fuel cell from the outside, temperature control work is required periodically to repair the defects.

[0006] Resin materials are also used for the subgasket, which acts as a support around the electrolyte membrane. Therefore, just like the electrolyte membrane, defects can occur in the subgasket. The subgasket also serves to seal fuel gas inside the fuel cell, and defects can reduce its sealing ability.

[0007] An object of the present invention is to easily repair defects inside a fuel cell. [Means for solving the problem]

[0008] One aspect of the present invention is a fuel cell (100) comprising a membrane electrode assembly (3) and a subgasket (5), wherein the membrane electrode assembly (3) comprises an electrolyte membrane (1) and a pair of electrodes (2) on either side of the electrolyte membrane (1), and the electrolyte membrane (1), the subgasket (5), or both, comprise a self-repairing material, and the self-repairing material is a polymer containing units with self-repairing properties.

[0009] Another aspect of the present invention is an electrolyte membrane (1) for a fuel cell (100), the electrolyte membrane (1) including a self-repairing material, the self-repairing material being a polymer including a unit having self-repairing properties.

[0010] Another aspect of the present invention is a subgasket (5) provided at the end of a membrane electrode assembly (3) of a fuel cell (100), the subgasket (5) including a self-repairing material, the self-repairing material being a polymer including units with self-repairing properties. [Effects of the Invention]

[0011] According to the present invention, defects inside a fuel cell can be easily repaired. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a cross-sectional view showing the configuration of a fuel cell according to an embodiment of the present invention. [Figure 2] FIG. 2 is a cross-sectional view showing the configuration of a cell. [Figure 3] FIG. 1 is a conceptual diagram showing a block copolymer in which no self-repairing unit is introduced. [Figure 4] FIG. 1 is a conceptual diagram showing an example of a block copolymer into which a unit having self-repairing properties has been introduced. [Figure 5]FIG. 1 is a conceptual diagram showing an example of a block copolymer into which a unit having self-repairing properties has been introduced. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, embodiments of the fuel cell, electrolyte membrane, and subgasket of the present invention will be described with reference to the drawings. The configurations described below are examples (typical examples) of the present invention, and the present invention is not limited to these configurations.

[0014] (fuel cell) FIG. 1 shows the configuration of a fuel cell 100 according to this embodiment. The fuel cell 100 of this embodiment is mounted on a mobile object such as a vehicle, and supplies driving power to the mobile object by generating electricity through a chemical reaction of fuel gas, but the present invention can also be applied to fuel cells in stationary power generation systems and the like, in addition to mobile objects.

[0015] 1, the fuel cell 100 includes a plurality of stacked cells 10, a pair of current collector plates 11, a pair of insulator plates 12, and a pair of end plates 13, each disposed on either side of each cell 10 in the stacking direction. The fuel cell 100 also includes a gas pipe 14 attached to at least one of the end plates 13. The gas pipe 14 communicates with a manifold (not shown).

[0016] Four through holes P1 to P4 are provided in the cells 10, the collector plate 11 on the gas pipe 14 side, the insulator plate 12, and the end plate 13. The four through holes P1 to P4 communicate with the gas pipe 14 and penetrate in the stacking direction of the cells 10. Fuel gas is supplied and discharged through these through holes P1 to P4.

[0017] The fuel cell 100 includes seals 15 between each of the current collector plates 11, insulator plates 12, end plates 13, and gas pipes 14. The seals 15 are, for example, O-rings that surround the outside of the through-holes P1 to P4 and are made of an elastomer material. The seals 15 come into contact with the adjacent members to seal the outer peripheries of the through-holes P1 to P4, thereby preventing gas leakage from the through-holes P1 to P4. The seals 15 may be made of only an elastomer material, or may further contain additives such as reinforcing materials to maintain the shape of the seals 15.

[0018] The pair of end plates 13 are fastened together with fastening members such as bolts and nuts, and a fastening force acts on the fuel cell 100 in the stacking direction of each component of the fuel cell 100 sandwiched between the end plates 13. This fastening force fixes the stack structure of each component between the end plates 13 and seals the fuel gas inside the fuel cell 100.

[0019] FIG. 2 shows a schematic configuration of the cell 10. 2, the cell 10 includes a membrane electrode assembly (MEA) 3, a pair of separators 4 arranged on either side of the MEA 3, and a subgasket 5 surrounding the outer periphery of the MEA 3. The MEA 3 includes an electrolyte membrane 1 and a pair of electrodes 2. The pair of electrodes 2 sandwich the electrolyte membrane 1.

[0020] (electrolyte membrane) The electrolyte membrane 1 is an ion-conductive polymer electrolyte membrane. Examples of polymer electrolytes that can be used for the electrolyte membrane 1 include perfluorosulfonic acid polymers such as Nafion (registered trademark) and Aquivion (registered trademark), aromatic polymers such as sulfonated polyether ether ketone (SPEEK) and sulfonated polyimide, and aliphatic polymers such as polyvinyl sulfonic acid and polyvinyl phosphoric acid.

[0021] From the viewpoint of improving durability, the electrolyte membrane 1 can be a composite membrane in which a porous substrate 1a is impregnated with a polymer electrolyte. The porous substrate 1a is not particularly limited as long as it has pores capable of supporting the polymer electrolyte, and a membrane in a porous, woven, nonwoven, fibril, or other form can be used. The material of the porous substrate 1a is also not particularly limited, but from the viewpoint of improving ion conductivity, the above-mentioned polymer electrolytes can be used. Among them, fluorine-based polymers such as polytetrafluoroethylene, polytetrafluoroethylene-chlorotrifluoroethylene copolymer, and polychlorotrifluoroethylene have excellent strength and shape stability.

[0022] Of the pair of electrodes 2, one electrode 2 is the anode, also called the fuel electrode, and the other electrode 2 is the cathode, also called the air electrode. Hydrogen gas is supplied to the anode as the fuel gas, and air containing oxygen gas is supplied to the cathode.

[0023] At the anode, electrons (e - ) and protons (H + ) occurs. The electrons move to the cathode via an external circuit (not shown). This electron movement generates a current in the external circuit. The protons move to the cathode via the electrolyte membrane 1.

[0024] At the cathode, electrons transferred from the external circuit convert oxygen gas (O2) into oxygen ions (O 2- ) is generated. The oxygen ions are transferred to the protons (2H + ) to form water (H2O).

[0025] The electrode 2 includes a catalyst layer 21. In this embodiment, the electrode 2 includes a gas diffusion layer 22 to improve the diffusibility of the fuel gas. The gas diffusion layer 22 is disposed on the separator side of the catalyst layer 21.

[0026] The catalyst layer 21 promotes the reaction between hydrogen gas and oxygen gas by the catalyst. The catalyst layer 21 includes a catalyst, a carrier that supports the catalyst, and an ionomer that coats these. Examples of the catalyst include metals such as platinum (Pt), ruthenium (Ru), iridium (Ir), rhodium (Rh), palladium (Pd), and tungsten (W), as well as mixtures and alloys of these metals. Among these, platinum, and mixtures and alloys containing platinum are preferred from the viewpoints of catalytic activity, resistance to carbon monoxide poisoning, heat resistance, and the like.

[0027] Examples of the carrier include conductive porous metal compounds having pores such as mesoporous carbon and Pt black. Mesoporous carbon is preferred from the viewpoints of good dispersibility, large surface area, and little particle growth at high temperatures even when a large amount of catalyst is supported. As the ionomer, an ion-conductive polymer electrolyte similar to that of the electrolyte membrane 1 can be used.

[0028] The gas diffusion layer 22 can diffuse the fuel gas supplied to the cell 10 uniformly over the entire surface of the catalyst layer 21 . The gas diffusion layer 22 can be formed by disposing a gas diffusion layer sheet as the outermost layer of the MEA 3. Examples of the gas diffusion layer sheet include porous fiber sheets such as carbon fibers that have electrical conductivity, gas permeability, and gas diffusivity, as well as metal sheet materials such as foam metal and expanded metal.

[0029] (subgasket) The subgasket 5 is a film or plate provided on the outer peripheral edge of the MEA 3. The subgasket 5 protects the edge of the electrolyte membrane 1 and functions as a support for the MEA 3. A resin with low electrical conductivity can be used as the material for the subgasket 5. There are no particular limitations on the resin material, and examples include polyphenylene sulfide (PPS), glass-filled polypropylene (PP-G), polystyrene (PS), silicone resin, and fluorine-based resin.

[0030] The separator 4 is also called a bipolar plate. The separator 4 is made of a conductive material such as carbon or stainless steel.

[0031] The separator 4 of this embodiment has a surface on which recesses 4a are formed. When the surface of the separator 4 on which the recesses 4a are formed faces the MEA 3, a flow path 20 is formed between the separator 4 and the MEA 3. The flow path 20 is not only a supply path for fuel gas but also a discharge path for water produced by chemical reactions during power generation.

[0032] The separator 4 of this embodiment has a plurality of ribs 4b on its surface. These ribs 4b form recesses 4a on the surface of the separator 4. Note that, as long as the recesses 4a can be formed on the surface of the separator 4, grooves may be formed on the surface of the separator 4, or both ribs 4b and grooves may be formed. The recesses 4a on one separator 4 form a flow path that communicates from through hole P1 to through hole P2, and the recesses 4a on the other separator 4 form a flow path that communicates from through hole P3 to through hole P4.

[0033] (self-healing material) The electrolyte membrane 1, the subgasket 5, or both contain a self-repairing material. This self-repairing material is a polymer containing units with self-repairing properties. Self-repairing properties refer to the ability of a material to recombine and recover from a broken portion even if a crack or the like occurs. The recombination may be, for example, a covalent bond, a hydrogen bond, an ionic bond, or a coordinate bond, or may be a bond based on an electrostatic interaction, a hydrophobic interaction, a π-electron interaction, or any other intermolecular interaction.

[0034] The self-repairing unit is, for example, a repeating unit of a polar olefin monomer represented by the following general formula (1). [ka] [In general formula (1), Z represents a heteroatom selected from the group consisting of oxygen, nitrogen, phosphorus, sulfur, and selenium. R1 represents an alkyl group having 1 to 30 carbon atoms. n is an integer of 1 or 2 depending on the atomic type of Z. R2 represents a hydrocarbylene group having 1 to 5 carbon atoms. R3 represents a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms.]

[0035] In the general formula (1), Z is preferably oxygen from the viewpoint of self-repairing property. n The position is preferably the ortho position. R1 may be a linear, branched, or cyclic alkyl group, and preferably has 1 to 20 carbon atoms, more preferably 1 to 10 carbon atoms, and even more preferably 1 to 6 carbon atoms. R2 is preferably a linear or branched alkylene group having 1 to 3 carbon atoms, or a cyclic alkylene group having 3 to 5 carbon atoms. The alkyl group represented by R3 is linear or branched, and specific examples thereof include a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, and an n-hexyl group. R3 is preferably a hydrogen atom. The substitution position of R3 is preferably the meta position. R3 may be bonded to each other and fused with the aromatic ring on which R3 is substituted to form a saturated fused ring such as naphthalene. In addition, in R1 to R3, a hydrogen atom bonded to a carbon atom may be substituted with a halogen atom such as a fluorine atom, or a bond such as -O-, -S-, -SO2-, or -CO- may be introduced into the carbon bond.

[0036] The self-repairing unit can be obtained by polymerizing one or more polar olefin monomers represented by the general formula (1) using a metallocene complex containing scandium or yttrium as the central metal. Examples of the metallocene complex include the scandium complex (C5ME4SiMe3)Sc(CH2C6H4NMe2-o).

[0037] From the viewpoint of adjusting the mechanical properties of the self-repairing material, the self-repairing unit preferably contains a repeating unit of a polar olefin monomer represented by general formula (1) and a repeating unit of a non-polar olefin monomer.

[0038] Examples of non-polar olefin monomers include ethylene, α-olefins, tetrafluoroethylene, substituted and unsubstituted styrenes, dienes, and cyclic olefins having 3 to 20 carbon atoms. Examples of α-olefins include linear α-olefins having 3 to 20 carbon atoms such as propylene, 1-butene, 1-pentene, 1-hexene, 1-octene, 1-decene, 1-dodecene, 1-tetradecene, 1-hexadecene, 1-octadecene, and 1-eicosene; and branched α-olefins having 4 to 20 carbon atoms such as 4-methyl-1-pentene, 3-methyl-1-pentene, and 3-methyl-1-butene. Examples of dienes include linear dienes having 3 to 20 carbon atoms such as 1,3-butadiene, 1,3-pentadiene, 1,4-pentadiene, 1,3-hexadiene, 1,4-hexadiene, 1,5-hexadiene, and 2,4-hexadiene, branched dienes having 4 to 20 carbon atoms such as 2-methyl-1,3-butadiene, 2,4-dimethyl-1,3-pentadiene, and 2-methyl-1,3-hexadiene, and cyclic dienes having 4 to 20 carbon atoms such as cyclohexadiene. Examples of cyclic olefins include norbornenes such as 2-norbornene and dicyclopentadiene; cyclohexadiene, etc.

[0039] Examples of the self-repairing unit include units represented by the following formulas (2) and (3). [ka] [In formula (2) or formula (3), R4 represents a non-polar substituent such as an alkyl group, and x and y represent the number of repetitions.]

[0040] In particular, scandium-catalyzed copolymers of anisylpropylene and ethylene have been confirmed to exhibit high self-healing properties (see "Synthesis of Self-Healing Polymers by Scandium-Catalyzed Copolymerization of Ethylene and Anisylpropylenes," Haobing Wang et al., J. Am. Chem. Soc., American Chemical Society, 2019, 141, pp. 3249-3257).

[0041] As described above, the self-repairing material containing repeating units of polar olefin monomers polymerized using a metallocene complex self-repairs even when no action other than that caused by the fuel cell 100 itself, such as irradiation with infrared rays, ultraviolet rays, or the like, or an action of applying energy such as heating or pressurization, is input from outside the fuel cell 100. Therefore, there is no need to apply an action to repair defects that have occurred in the electrolyte membrane 1, and it is possible to omit devices or operations separate from the fuel cell 100 for applying an action from outside the fuel cell 100.

[0042] Furthermore, the self-repairing materials bond and repair themselves through contact with each other. As described above, the fuel cell 100 is fastened by the fastening members in the stacking direction of each component of the fuel cell 100, and therefore the electrolyte membrane 1 or subgasket 5 is also fastened in the stacking direction. Therefore, the fastening force increases due to the vibration of the vehicle while traveling and the thermal expansion or wet expansion of the electrolyte membrane 1 during power generation, and the electrolyte membrane 1 or subgasket 5 is easily crushed by the components on both sides that sandwich the electrolyte membrane 1 or subgasket 5. The crushed electrolyte membrane 1 or subgasket 5 expands in the in-plane direction (xy plane), making it easy for the cut portions of the self-repairing materials to come into contact with each other, facilitating spontaneous self-repair even when no external action is input to the fuel cell 100.

[0043] The fastening member for fastening the electrolyte membrane 1 or the subgasket 5 may be a fixing member for fixing the stack of cells 10, and the fastening direction may be an in-plane direction (xy plane) of the cells 10 instead of the stack direction (z direction). Also, a fastening member provided separately from the fastening members for fixing the components of the fuel cell 100 may be used to apply a fastening force for promoting contact of the self-repairing material.

[0044] Furthermore, it has been confirmed that the self-repairing material exhibits the same self-repairing properties as under dry conditions, even in the presence of water molecules, 1 M NaOH, or 1 M HCl. Such a self-repairing material can self-repair defects in the electrolyte membrane 1 even in an environment where water is produced by power generation in the fuel cell 100.

[0045] The self-repairing material contained in the electrolyte membrane 1 and the subgasket 5 will be described in detail below.

[0046] (Self-repairing materials in electrolyte membranes) In the electrolyte membrane 1, the self-repairing material may be used as a polymer electrolyte or may be a material used in combination with a polymer electrolyte.

[0047] <Self-healing materials as polymer electrolytes> A polyelectrolyte is typically a polymer containing repeating units with ion-exchange groups. A polyelectrolyte self-healing material further contains a unit with self-healing properties within the polymer.

[0048] Examples of polymer electrolytes containing repeating units having ion exchange groups include fluorine-based polymers having ion exchange groups, aliphatic polymers having ion exchange groups, and aromatic polymers having ion exchange groups.

[0049] Examples of fluorine-based polymers having ion exchange groups include perfluorosulfonic acid polymers such as Nafion (registered trademark).

[0050] Examples of aliphatic polymers having an ion exchange group include polyvinyl sulfonic acid and polyvinyl phosphoric acid.

[0051] Examples of aromatic polymers having ion exchange groups include sulfonated polyether ether ketone (SPEEK), sulfonated polyethersulfone (SPES), sulfonated polyphenylsulfone (SPPSU), sulfonated polyimide, sulfonated polyetherimide, sulfonated polysulfone, and sulfonated polystyrene.

[0052] The polymer can be obtained by polymerizing an olefin monomer having an ion exchange group, or by introducing an ion exchange group into a polymer of an olefin monomer by sulfonating it, etc. The polymer may be a copolymer of an olefin monomer having an ion exchange group and a non-polar olefin monomer.

[0053] The ion exchange group is not particularly limited, and may be either an anionic group or a cationic group. Examples of anionic groups include sulfonic acid groups, phosphoric acid groups, carboxylic acid groups, boronic acid groups, and sulfonylimide groups. Among these, sulfonic acid groups are preferred because of their excellent ionic conductivity. Counter cations are not particularly limited, but include alkali metal ions, H + Monovalent cations such as quaternary ammonium ions are preferred.

[0054] Examples of cationic groups include unsubstituted amino groups, N-alkylamino groups, N-dialkylamino groups, and other amino groups; nitrogen-containing heterocycles such as pyridyl groups and imidazolyl groups; and quaternary ammonium groups such as N-trialkylammonium groups, N-alkylpyridinium groups, N-alkylimidazolium groups, thiouronium groups, and isothiouronium groups. The counter anion of the quaternary ammonium group is not particularly limited, but may be PF6 - , SbF6 - , AsF6 - Halide anions of group 5B elements such as BF4 -Halide anions of group 3B elements such as I - (I3 - ), Br - , Cl - halogen anions such as ClO4 - Halide anions such as AlCl4 - , FeCl4 - , SnCl5 - Metal halide anions such as NO3 - Nitrate anion, p-toluenesulfonate anion, naphthalenesulfonate anion, CH3SO3 - , CF3SO3 - Organic sulfonate anions such as CF3COO - , C6H5COO - Carboxylic acid anions such as OH - Monovalent anions such as are preferred.

[0055] The olefin monomer into which an ion exchange group is introduced is not particularly limited as long as it allows the introduction of an ion exchange group, and examples thereof include olefins such as ethylene, propylene, 1-butene, 4-methyl-1-pentene, 1-hexene, 1-octene, and 1-decene; vinyl halides such as tetrafluoroethylene; aromatic vinyls such as styrene, o-methylstyrene, p-methylstyrene, m-methylstyrene, 2,4-dimethylstyrene, ethylstyrene, p-tert-butylstyrene, α-methylstyrene, α-methyl-p-methylstyrene, o-chlorostyrene, m-chlorostyrene, p-chlorostyrene, p-bromostyrene, 2-methyl-1,4-dichlorostyrene, 2,4-dibromostyrene, and vinylnaphthalene; cyclic olefins such as cyclopentene, dicyclopentadiene, 2-norbornene, and 5-ethylidene-2-norbornene; methyl (meth)acrylate, (meth)acrylonitrile, and (meth)acrylamide.

[0056] As the non-polar olefin monomer, the same monomers as the non-polar olefin monomers listed as the units having self-repairing properties can be used.

[0057] The form of the copolymer is not particularly limited, and may be, for example, a block copolymer, a statistical copolymer, a graft copolymer, an alternating copolymer, a star copolymer, or a combination thereof.

[0058] When the self-healing polymer electrolyte is a block copolymer, the hydrophilic block is formed by repeating units of olefin monomers having ion exchange groups, and the hydrophobic block is formed by repeating units of non-polar olefin monomers. The hydrophilic block, the hydrophobic block, or both may contain the self-healing units described above.

[0059] The hydrophilic block containing a self-repairing unit is formed, for example, by polymerizing an olefin monomer having an ion exchange group and a polar olefin monomer represented by general formula (1) using the metallocene complex. Since repeating units of the polar olefin monomer are formed in the hydrophilic block, the self-repairing property of the hydrophilic block is exhibited. When the olefin monomer into which the ion exchange group is introduced is a non-polar olefin monomer, repeating units of the polar olefin monomer and repeating units of the non-polar olefin monomer are formed in the hydrophilic block, which is more preferable.

[0060] The hydrophobic block containing the self-repairing unit is formed, for example, by polymerizing a non-polar olefin monomer and a polar olefin monomer represented by general formula (1) using a metallocene complex. The polymerization forms repeating units of the polar olefin monomer or repeating units of the polar olefin monomer and repeating units of the non-polar olefin monomer in the hydrophobic block, thereby manifesting the self-repairing property of the hydrophobic block.

[0061] When the polymer electrolyte is a block copolymer, it is preferable that the terminal block of the block copolymer contains a unit having self-repairing properties. When a polymer electrolyte membrane is used as the electrolyte membrane 1, the block copolymer is oriented and the ends of the molecular chains tend to come into contact with each other, so that the self-repairing properties are easily exhibited.

[0062] Similarly, from the viewpoint of exhibiting self-repairing properties, when the polymer electrolyte is a statistical copolymer or a graft copolymer containing a hydrophilic block and a hydrophobic block, it is preferable that the terminal unit is a unit having self-repairing properties.

[0063] In the case of statistical copolymers or graft copolymers, which are more difficult to orient than block copolymers, the molecular chains may come into contact with each other at the inner side than the ends depending on the orientation conditions in the membrane. Therefore, when the polymer electrolyte is a statistical copolymer or a graft copolymer, at least one block inside the ends can contain a self-repairing unit.

[0064] Figure 3 shows an example of a block copolymer without the self-healing unit introduced, while Figures 4 and 5 show examples of the block copolymer after the self-healing unit has been introduced. The block copolymer M shown in FIG. 3 includes a hydrophobic block M10 formed by a non-polar olefin monomer M1 and a hydrophobic block M20 formed by an olefin monomer M2 having an ion-exchange group.

[0065] When a polar olefin monomer M3 represented by general formula (1) is added during the formation of the terminal block M10 of this block copolymer M, repeating units of a non-polar olefin monomer M1 and a polar olefin monomer M3 are introduced into the terminal block M10, as shown in Figure 4. Alternatively, repeating units of a non-polar olefin monomer M1 and repeating units of a polar olefin monomer M3 are introduced into the terminal block M10, as shown in Figure 5. Both blocks M10 contain repeating units of a polar olefin monomer represented by general formula (1), and therefore exhibit self-healing properties.

[0066] The copolymer can be obtained by adding each monomer to a system containing a metallocene complex and polymerizing the monomers. As the polymerization method, any method such as solution polymerization, suspension polymerization, liquid-phase bulk polymerization, emulsion polymerization, gas-phase polymerization, or solid-phase polymerization can be used. When a solvent is used in the polymerization reaction, the solvent used need only be inert to the polymerization reaction, and examples thereof include aprotic polar solvents such as N,N-dimethylformamide, N,N-dimethylacetamide, N-methyl-2-pyrrolidone, and dimethyl sulfoxide; chlorine-based solvents such as dichloromethane, chloroform, 1,2-dichloroethane, chlorobenzene, and dichlorobenzene; alcohols such as methanol, ethanol, and propanol; and alkylene glycol monoalkyl ethers such as ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. These solvents can be used alone, or two or more of them can be mixed and used as needed.

[0067] By appropriately adjusting the addition method, heating conditions, etc., it is possible to produce copolymers such as block copolymers, statistical copolymers, graft copolymers, and combinations thereof.

[0068] For example, in the case of a statistical copolymer or an alternating copolymer, a mixture of two or more monomers can be polymerized in the presence of a catalyst composition. In the case of a block copolymer, the monomers of each block can be sequentially supplied to the reaction system and reacted. Specifically, after each monomer of the hydrophilic block is reacted, each monomer of the hydrophobic block is supplied and reacted. Furthermore, a self-repairing unit can be selectively introduced into the hydrophilic block by supplying a polar olefin monomer represented by general formula (1) together with the monomer of the hydrophilic block.

[0069] The copolymer may be crosslinked from the viewpoint of improving mechanical strength. Examples of a crosslinking method using a crosslinking agent include a method in which a composition is obtained by dissolving a polymer electrolyte and a crosslinking agent in a solvent, and the composition is crosslinked by heating or irradiating with light. The crosslinking agent is not particularly limited, and known crosslinking agents such as divinylbenzene can be used.

[0070] Instead of introducing a self-repairing unit during the synthesis of the polymer electrolyte, a self-repairing unit may be added to an existing polymer electrolyte. For example, a polar olefin monomer represented by general formula (1) and, if necessary, a non-polar olefin monomer may be polymerized to an existing polymer electrolyte having a functional group such as a vinyl group, and repeating units derived from these monomers may be added. In this way, the polymer electrolyte may be molecularly designed to have a highly reactive functional group, such as a vinyl group or an ethynyl group, at its terminal so that self-repairing properties can be imparted later.

[0071] <Materials used in combination with polymer electrolytes> The electrolyte membrane 1 containing the self-repairing material may be a membrane formed from a resin composition in which the self-repairing material is mixed with a polymer electrolyte. The self-repairing material may also be mixed with the polymer electrolyte impregnated into the porous substrate 1a. Even if a defect occurs in the electrolyte membrane 1, the self-repairing material present in the gyroid or layered form in the membrane comes into contact with each other, recombines, and self-repairs the defect.

[0072] The electrolyte membrane 1 may include a cross-linking agent, a reinforcing agent, a reinforcing layer, etc. The electrolyte membrane 1 may include a self-repairing material as these materials used in combination with the polymer electrolyte.

[0073] The crosslinking agent is not particularly limited, and examples thereof include divinylbenzene, peroxide-based crosslinking agents, and thiol-based crosslinking agents. Furthermore, copolymers having both acidic and basic substituents may be mixed with the polymer electrolyte to further enhance the ionic conductivity of the electrolyte membrane 1. As such a crosslinking agent, a polymer containing a self-repairing unit may be used. As with the polymer electrolyte, the self-repairing unit may be introduced into a portion of the crosslinking agent molecule during synthesis of the crosslinking agent, or may be introduced into the crosslinking agent after synthesis, as long as it can leave a functional group capable of undergoing a crosslinking reaction in the molecule.

[0074] The reinforcing agent may be a polymer electrolyte such as fibril PTFE, etc. As the reinforcing agent, a polymer containing a self-repairing unit, similar to the polymer electrolyte described above, may be used.

[0075] The reinforcing layer is provided, for example, on a polymer electrolyte membrane. The reinforcing layer made of a self-repairing material can be formed, for example, by applying a reinforcing layer composition containing the self-repairing material to the surface of the polymer electrolyte membrane. The porous substrate 1a is a reinforcing layer provided in the membrane. For example, when expanded polytetrafluoroethylene (ePTFE) is used as the porous substrate 1a, a metallocene complex is used to synthesize PTFE containing a unit having self-repairing properties, as in the case of the above polymer electrolyte, and the synthesized PTFE can be stretched to obtain ePTFE having self-repairing properties.

[0076] (Self-healing materials in subgaskets) The self-repairing material in the subgasket 5 may be used as the resin material of the subgasket 5 or may be a material used in combination with the resin material.

[0077] <Self-repairing resin materials> The self-healing material as a resin material is, for example, a copolymer of a monomer of the resin material and a polar olefin monomer represented by general formula (1). By polymerizing each monomer with a metallocene complex, a unit derived from the polar olefin monomer represented by general formula (1) is formed in the copolymer, and thus a unit with self-healing properties can be introduced into the resin material. If necessary, a non-polar olefin monomer may be added and polymerized.

[0078] Polyethylene terephthalate (PET), polyethylene naphthalate (PEN), or the like, which have excellent mechanical strength, are generally used as the resin material for the subgasket 5. However, if a polymer containing a self-repairing unit is used as the resin material, it can self-repair even if a defect occurs and maintain sufficient mechanical strength. Therefore, the resin material is not limited to PET or PEN, and general-purpose resin materials such as olefin resins such as polypropylene and polyethylene can also be used.

[0079] The form of the copolymer is not particularly limited, and may be, for example, a block copolymer, a statistical copolymer, a graft copolymer, an alternating copolymer, a star copolymer, or a combination thereof. For example, the self-repairing material used as the resin material may be a block copolymer containing a block of repeating units derived from propylene and a block of repeating units derived from a polar olefin monomer such as anisylpropylene, or an alternating copolymer in which propylene and anisylpropylene are arranged alternately.

[0080] As in the case of polymer electrolytes, in order to improve the self-repairing property upon contact, in the case of block copolymers, it is preferable that the terminal block contains a self-repairing unit, and in the case of statistical copolymers or graft copolymers, the terminal or one or more blocks inside the terminal may contain a self-repairing unit.

[0081] Furthermore, similar to the polymer electrolytes described above, it is also possible to introduce self-repairing units into a resin material after synthesis, rather than during synthesis. For example, a self-repairing unit can be introduced into a resin material whose molecular structure has been designed to have functional groups such as vinyl groups or ethynyl groups by polymerizing a polar olefin monomer represented by general formula (1) and, if necessary, a non-polar olefin monomer using a metallocene complex.

[0082] <Materials used in combination with resin materials> The subgasket 5 containing the self-repairing material may be a film formed from a resin composition in which the self-repairing material is mixed with a resin material such as PEN. The self-repairing material may also be used as a crosslinking agent or reinforcing agent added to the resin composition of the subgasket 5, or as a reinforcing layer included in the subgasket 5.

[0083] As described above, according to this embodiment, the electrolyte membrane 1, the subgasket 5, or both contain a self-repairing material. This self-repairing material is a polymer containing units with self-repairing properties. Even if a defect such as a crack occurs and the bond is severed, the severed portion rebonds due to contact between the self-repairing units, so the defect inside the fuel cell 100 can be easily repaired. This allows for a long-term guarantee of power generation performance and makes maintenance easy. [Example]

[0084] The present invention will be explained in more detail below by way of examples, but the present invention is not limited to the following examples.

[0085] An olefin monomer having an ion exchange group and a nonpolar olefin monomer were polymerized to obtain a block copolymer containing a hydrophilic block and a hydrophobic block as polymer electrolyte (a). Furthermore, anisylpropylene was introduced using a scandium catalyst during the synthesis of the hydrophobic block of polymer electrolyte (a), and a block copolymer containing a self-healing unit in the terminal block was obtained as polymer electrolyte (b). Using the membranes of each polymer electrolyte (a) and (b) as electrolyte membranes, cells (A) and (B) with a configuration similar to cell 10 shown in Figure 2 were manufactured.

[0086] Each cell (A) and (B) was placed in a humidity chamber at -30°C for 1 hour, followed by 100°C for 1 hour, and this hot-cooling test was repeated five times. After leaving the cells at room temperature (25°C, 60% RH) for a certain period of time, the electrolyte membrane of each cell (A) and (B) was visually inspected for damage. Defects such as cracks were observed in cell (A) using polymer electrolyte (a) without anisylpropylene. On the other hand, no defects were observed in cell (B) using polymer electrolyte (b) with anisylpropylene, confirming the high self-repairing ability of cell (B). [Explanation of symbols]

[0087] 100... fuel cell, 10... cell, 1... electrolyte membrane, 2... electrode, 3... membrane electrode assembly, 4... separator, 5... subgasket

Claims

1. A plurality of stacked cells (10), A fastening member; A fuel cell (100) comprising: Each of the plurality of cells (10) has a membrane electrode assembly (3) and a subgasket (5), The membrane electrode assembly (3) comprises an electrolyte membrane (1) and a pair of electrodes (2) on both sides of the electrolyte membrane (1), the electrolyte membrane (1), the subgasket (5), or both, comprise a self-repairing material; The self-repairing material is a polymer containing a unit having self-repairing properties, The self-repairing unit is a repeating unit of a polar olefin monomer represented by general formula (1), The self-repairing property is a property in which, when a break occurs in the self-repairing material, the self-repairing material rebonds due to an interaction between one part of the self-repairing material and another part of the self-repairing material; the interaction is a covalent bond, a hydrogen bond, an ionic bond, a coordinate bond, an electrostatic interaction, a hydrophobic interaction, a π-electron interaction, a dipole-dipole interaction, or a van der Waals force; The fastening member fastens the subgasket (5) or the electrolyte membrane (1) in the stacking direction of the plurality of cells (10) or in the in-plane direction of each of the plurality of cells (10). Fuel cell (100). 【Chemical 1】 (In the formula, Z is a heteroatom selected from the group consisting of oxygen, nitrogen, phosphorus, sulfur, and selenium; R 1 is an alkyl group having 1 to 30 carbon atoms; n is an integer of 1 or 2 depending on the atomic type of Z; R 2 is a hydrocarbylene group having 1 to 5 carbon atoms; and R 3 is a hydrogen atom, a halogen atom, or an alkyl group having 1 to 10 carbon atoms.)

2. The self-repairing material is contained in the electrolyte membrane (1) as a polymer electrolyte, or in the subgasket (5) as a resin material of the subgasket (5). The fuel cell (100) of claim 1.

3. the polymer electrolyte is a block copolymer including a hydrophilic block having an ion exchange group and a hydrophobic block, The hydrophilic block, the hydrophobic block, or both of them contain the self-repairing unit. The fuel cell (100) of claim 2.

4. The self-repairing material is a material used in combination with a polymer electrolyte in the electrolyte membrane (1), or a material used in combination with a resin material of the subgasket (5) in the subgasket (5). The fuel cell (100) of claim 1.

5. the polymer containing a self-repairing unit is a block copolymer, a statistical copolymer, or a graft copolymer; The terminal block of the block copolymer, the statistical copolymer, or the graft copolymer contains the unit having the self-repairing property. The fuel cell (100) of any one of claims 1, 2 and 4.

6. the polymer containing the self-repairing unit is a statistical copolymer or a graft copolymer, At least one block located inside the terminal of the statistical copolymer or the graft copolymer contains the unit having the self-repairing property. The fuel cell (100) of any one of claims 1, 2 and 4.

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