JP2020021549A - Laminated electrolyte membrane and fuel cell including the same - Google Patents

Abstract

To provide a laminated electrolyte membrane thin in thickness and excellent in mechanical strength and gas barrier.SOLUTION: A laminated electrolyte membrane includes a first electrolyte membrane containing a first proton conducting polymer and a synthetic resin, and a second electrolyte membrane containing a second proton conducting polymer, the second electrolyte membrane being integrated with the first electrolyte membrane. The synthetic resin is a condensable resin, and such a resin may be at least one selected from the group consisting of, for example, a polyvinyl acetal resin, polyimide, a phenol formaldehyde resin, a melamine formaldehyde resin, an urea resin and polyamide.SELECTED DRAWING: Figure 1

Description

  The present disclosure relates to an electrolyte membrane having proton conductivity used as an electrolyte layer of a fuel cell.

  A fuel cell is a clean power generation device that generates power by an electrochemical reaction between a fuel and an oxidant to generate water. The fuel cell includes, for example, an electrolyte membrane having proton conductivity, two catalyst layers arranged so as to sandwich the electrolyte membrane, and two gas diffusions arranged so as to sandwich the electrolyte membrane through each catalyst layer. And two separators arranged so as to sandwich the electrolyte membrane via each gas diffusion layer. Many polymer electrolyte membranes have been proposed as electrolyte membranes having proton conductivity (Non-Patent Documents 1 to 3).

Applied Energy, 88, 981-1007 (2011) J. Hydro. Eng., 38, 4901-4934 (2013) J. ECS., 164, F387-F399 (2017)

  The electrolyte membrane having proton conductivity plays a role of transporting protons and blocking gas. From the viewpoint of improving proton conductivity, it is effective to make the electrolyte membrane thinner. On the other hand, when the electrolyte membrane becomes thin, the mechanical strength of the electrolyte membrane decreases, and the gas barrier properties also decrease. That is, the conventional polymer electrolyte membrane has a limit in thinning.

  One aspect of the present disclosure is a first electrolyte membrane including a first proton conductive polymer and a synthetic resin, and a second electrolyte membrane including a second proton conductive polymer and integrated with the first electrolyte membrane. And wherein the synthetic resin is a condensable resin.

  Another aspect of the present disclosure relates to a first electrolyte membrane including a first proton conductive polymer and a synthetic resin, and a second electrolyte including a second proton conductive polymer and integrated with the first electrolyte membrane. A synthetic electrolyte membrane, wherein the synthetic resin is at least one selected from the group consisting of polyvinyl acetal resin, polyimide, phenol formaldehyde resin, melamine formaldehyde resin, urea resin, and polyamide.

  Yet another aspect of the present disclosure relates to a fuel cell including the above-mentioned laminated electrolyte membrane and a pair of catalyst layers sandwiching the laminated electrolyte membrane from both sides.

  According to the present disclosure, a laminated electrolyte membrane that is thin and has excellent mechanical strength and gas barrier properties can be obtained.

It is a conceptual diagram which contrasts the conventional electrolyte membrane (a) and the laminated electrolyte membrane (b) which concerns on one Embodiment of this indication. 1 is a schematic cross-sectional view illustrating a structure of a single cell of a fuel cell according to an embodiment of the present disclosure.

  The laminated electrolyte membrane according to the embodiment of the present disclosure includes a first electrolyte membrane including a first proton conductive polymer and a synthetic resin, and a second electrolyte membrane including a second proton conductive polymer, and is integrated with the first electrolyte membrane. A second electrolyte membrane. Here, the laminated electrolyte membrane satisfies at least one condition selected from the following conditions AC.

  Condition A is a condition that the synthetic resin is a condensable resin. The condensable resin is a resin obtained by polycondensing a precursor thereof. The precursor of the synthetic resin (condensable resin) is condensed or ring-opened, for example, in a solution to produce a synthetic resin. Here, the precursor of the synthetic resin may be any as long as it can be dissolved in a solution containing the first proton-conducting polymer and condensed or opened in the solution to produce the synthetic resin. Since such a synthetic resin is sufficiently mixed with the first proton conductive polymer in the liquid phase and is complexed, the first proton conductive polymer can be reinforced at a molecular level. The synthetic resin may have a crosslinked structure.

  Condition B is a condition that the synthetic resin is at least one selected from the group consisting of polyvinyl acetal resin, polyimide, phenol formaldehyde resin, melamine formaldehyde resin, urea resin, and polyamide. Usually, these synthetic resins can simultaneously satisfy the condition A. Above all, polyvinyl acetal resin, phenol formaldehyde resin, melamine formaldehyde resin, and urea resin can form a crosslinked structure, so that the mechanical strength of the first electrolyte membrane is easily increased. The polyvinyl acetal resin is acetalized polyvinyl alcohol, and may be, for example, formalized polyvinyl alcohol (so-called vinylon).

  Condition C is a condition that the tensile strength of the first electrolyte membrane is higher than the tensile strength of the second electrolyte membrane. The tensile strength is measured according to JIS K7161 (2014). The method for measuring the tensile strength of the first and second electrolyte membranes is not particularly limited, but may be compared by the tensile strength in a direction perpendicular to the thickness direction of the electrolyte membrane. For example, the first or second electrolyte membrane may be peeled off from the laminated electrolyte membrane, the respective tensile strengths may be measured, and the tensile strengths may be compared. Further, the tensile strength (Nt) of the entire laminated electrolyte membrane may be compared with the tensile strength (N2) of the membrane having the same thickness as the laminated electrolyte membrane and entirely composed of the second proton conductive polymer. . If Nt> N2, condition C is satisfied. It is preferable that the tensile strength (n1) of the first electrolyte membrane and the tensile strength (n2) of the second electrolyte membrane satisfy 1.1 ≦ n1 / n2.

  The proton conductive polymer is generally a polymer having a plurality of acid groups in the molecule. The proton transfer in the proton conductive polymer is performed, for example, via a sulfonic acid group, a phosphate group, or the like. The first proton conductive polymer and the second proton conductive polymer may be the same proton conductive polymer or different proton conductive polymers.

Hereinafter, the proton conductive polymer having a sulfonic acid group will be described.
The proton conductive polymer having a sulfonic acid group has an EW (Equivalent Weight) value of at least 2000 g / mol or less. Here, the EW value represents the number of grams of the polymer in a dry state per mole of the sulfonic acid group. For example, when the dried polymer Wg contains n moles of sulfonic acid groups, the EW value is represented by the W / n ratio. Therefore, the smaller the EW value, the more sulfonic acid groups, and the higher the proton conductivity.

  The EW value is determined from the equivalent of sulfonic acid groups (ion exchange capacity). The ion exchange capacity (IEC) is the amount ([A] ml) of the NaOH solution required for performing titration of the proton conductive polymer sample using a NaOH solution having a predetermined concentration and neutralizing the sample until the pH becomes 7. And the concentration of the NaOH solution ([B] g / ml) by the following formula.

  Ion exchange capacity (IEC) (meq / g) = [A] × [B] / sample weight (g)

  The synthetic resin is an artificially or industrially synthesized resin other than the first and second proton conductive polymers. The synthetic resin may have some proton conductivity, but from the viewpoint of maintaining the mechanical strength, the EW value of the synthetic resin may be at least more than 2000 g / mol.

  The content of the synthetic resin in the first electrolyte membrane may be, for example, 1% by mass or more, preferably 5% by mass or more, from the viewpoint that the mechanical strength of the first electrolyte membrane can be set to a sufficiently large value. On the other hand, from the viewpoint of ensuring sufficient proton conductivity in the first electrolyte membrane, the content of the synthetic resin may be, for example, 60% by mass or less.

  The second electrolyte membrane generally does not contain a synthetic resin, but may contain a small amount of a synthetic resin. Therefore, the content of the synthetic resin satisfies the relationship of the second electrolyte membrane <the first electrolyte membrane. From the viewpoint of securing sufficient gas barrier properties and flexibility, it is sufficient that more than 99% by mass of the second electrolyte membrane is the second proton conductive polymer. In this case, it can be said that the second electrolyte membrane does not substantially contain a synthetic resin. However, from the viewpoint of proton conductivity, the second electrolyte membrane preferably does not contain a synthetic resin. In the vicinity of the boundary between the first electrolyte membrane and the second electrolyte membrane, the synthetic resin diffused from the first electrolyte membrane may be present in the second electrolyte membrane.

  The stacked electrolyte membrane preferably includes a pair of second electrolyte membranes sandwiching the first electrolyte membrane from both sides. In this case, the laminated electrolyte membrane includes at least one layer of the first electrolyte membrane and at least two layers of the second electrolyte membrane. According to such a sandwich structure, gas barrier properties can be further improved. Further, when the catalyst layer and the second electrolyte membrane are brought into contact, the interface resistance between the laminated electrolyte membrane and the catalyst layer is easily suppressed.

  FIG. 1A is a conceptual diagram of a conventional electrolyte membrane 1a. The conventional electrolyte membrane 1a does not substantially contain a synthetic resin and is formed only of a proton conductive polymer. When the conventional electrolyte membrane 1a is thinned, mechanical strength cannot be maintained, productivity is reduced, and gas barrier properties are also reduced. If a fibrous reinforcing material (for example, polytetrafluoroethylene (PTFE) fiber) is added to the conventional electrolyte membrane 1a, the electrolyte membrane 1a can be thinned. However, it is impossible to obtain the electrolyte membrane 1a thinner than the thickness of the fiber. Further, such a fibrous reinforcing material is generally expensive. Further, the conventional electrolyte membrane 1a tends to swell due to water content or the like.

  From the viewpoint of obtaining a thin electrolyte membrane having excellent mechanical strength and gas barrier properties, it contains a synthetic resin and has a sufficiently thin electrolyte membrane (first electrolyte membrane). It is effective to laminate a thin electrolyte membrane (second electrolyte membrane). The synthetic resin functions as a reinforcing material for the first electrolyte membrane. Therefore, the first electrolyte membrane has a higher mechanical strength than the second electrolyte membrane, so that the first electrolyte membrane can be easily thinned. However, defects such as cracks and pinholes are liable to occur in the first electrolyte membrane containing a synthetic resin, and it may be difficult to secure high gas barrier properties by itself. On the other hand, when the second electrolyte membrane is laminated on the first electrolyte membrane, gas barrier properties are greatly improved even when the second electrolyte membrane is extremely thin.

  FIG. 1B is a conceptual diagram of the laminated electrolyte membrane 1 according to an embodiment of the present disclosure. The laminated electrolyte membrane 1 in the illustrated example includes a first electrolyte membrane 11 and a pair of second electrolyte membranes 12 sandwiching the first electrolyte membrane 11 from both sides. As a result, even if defects such as cracks and pinholes are generated in the first electrolyte membrane 11, the influence of the defects is reduced, gas barrier properties are not significantly impaired, and swelling due to water content and the like is suppressed. Further, the productivity of the laminated electrolyte membrane 1 is also improved by the improvement in mechanical strength due to the contribution of the first electrolyte membrane 11. In this case, the thickness of the laminated electrolyte membrane 1 can be extremely reduced while maintaining the mechanical strength. Further, synthetic resin is less expensive than reinforcing materials.

  As at least one of the first proton conductive polymer and the second proton conductive polymer, at least one selected from the group consisting of a fluoropolymer and a hydrocarbon polymer can be used. Both fluorine-based polymers and hydrocarbon-based polymers have excellent proton conductivity.

  Among the proton conductive polymers, the fluoropolymer may be fluorohydrocarbonsulfonic acid, perfluorocarbonsulfonic acid, or the like. The perfluorocarbon sulfonic acid has, for example, a tetrafluoroethylene skeleton and a perfluoro side chain having a sulfonic acid group. As such a perfluorocarbon sulfonic acid, for example, a non-crosslinked copolymer of tetrafluoroethylene and a perfluorovinyl monomer may be mentioned. The perfluorovinyl monomer may be, for example, vinyl ether, and among them, (2-sulfoethoxy) propyl vinyl ether is preferable. When the first proton conductive polymer is a fluoropolymer, the second proton conductive polymer is also preferably a fluoropolymer. The perfluorocarbon sulfonic acid has, for example, the following general formula (A):

Indicated by Here, x, y, m, and n can be, for example, x = 1.5 to 14, y = 500 to 1500, m = 0 to 3, and n = 1 to 5, respectively.

  Among the proton conductive polymers, hydrocarbon-based polymers have, for example, a skeleton in which aromatic rings such as benzene rings are linearly bonded. At least a part of the aromatic ring is sulfonated by a sulfonic acid group, a sulfoalkyl group or the like. Specifically, examples of the hydrocarbon polymer include a polyphenylsulfone skeleton, a polyetheretherketone skeleton, a polyimide skeleton, a polyethersulfone skeleton, a polyetherimide skeleton, a polysulfone skeleton, a polystyrene skeleton, and a polyarylene ether sulfoneketone skeleton. Having a structure in which the aromatic ring contained in the skeleton is sulfonated. When the first proton conductive polymer is a hydrocarbon polymer, the second proton conductive polymer is also preferably a hydrocarbon polymer.

  The first proton conductive polymer and the second proton conductive polymer may have the same kind of skeleton. For example, when the first proton conductive polymer has a tetrafluoroethylene skeleton, it is preferable that the second proton conductive polymer also has a tetrafluoroethylene skeleton. Further, the first proton conductive polymer has, for example, a polyphenylsulfone skeleton, a polyetheretherketone skeleton, a polyimide skeleton, a polyethersulfone skeleton, a polyetherimide skeleton, a polysulfone skeleton, a polystyrene skeleton, or a polyarylene ether sulfoneketone skeleton. When it has, it is preferable that the second proton conductive polymer also has a corresponding skeleton. By adopting the same kind of skeleton in this manner, the dimensional change of each electrolyte membrane due to external force, thermal expansion, and the like becomes almost the same, so that separation between the first electrolyte membrane and the second electrolyte membrane hardly occurs. . Further, since the behavior of the laminated electrolyte membrane becomes uniform, a decrease in durability and a decrease in proton conductivity of the laminated electrolyte membrane are suppressed.

  The EW value (EW2) of the second electrolyte membrane may be smaller than the EW value (EW1) of the first electrolyte membrane. At this time, it is preferable that the second electrolyte membrane is brought into contact with the catalyst layer. For example, when the laminated electrolyte membrane has a three-layer structure including a pair of second electrolyte membranes sandwiching the first electrolyte membrane from both sides, the pair of second electrolyte membranes are in contact with the anode and cathode catalyst layers, respectively. When the second electrolyte membrane having a small EW value and having a relatively large number of sulfonic acid groups comes into contact with the catalyst layer, more proton transfer paths can be secured and the rate of proton supply can be suppressed. When more proton transfer paths are secured, local concentration of power generation can be prevented, so that deterioration of the catalyst and the electrolyte membrane is likely to be suppressed.

  When the EW value decreases (the number of sulfonic acid groups increases), hydrophilicity increases, so that it is difficult to form a membrane using a proton conductive polymer, and the mechanical strength of the electrolyte membrane tends to decrease. On the other hand, in the case of the laminated electrolyte membrane, the mechanical strength is secured by the first electrolyte membrane, so that the EW value of the second electrolyte membrane can be sufficiently reduced. In other words, even when the second electrolyte membrane having a small EW value and a small mechanical strength is used, the overall mechanical strength of the laminated electrolyte membrane can be kept high.

  The ratio EW2 / EW1 of the EW value (EW2) of the second electrolyte membrane to the EW value (EW1) of the first electrolyte membrane satisfies, for example, 0.2 ≦ EW2 / EW1 <1, and more preferably 0.5 ≦ EW2. /EW1≦0.9 is satisfied. EW1 satisfies, for example, 400 g / mol <EW1 ≦ 2000 g / mol, and EW2 satisfies, for example, 400 g / mol ≦ EW1 ≦ 1500 g / mol.

  The thickness of the laminated electrolyte membrane may be, for example, 15 μm or less, and may be as small as 10 μm or less. At that time, sufficient mechanical strength can be maintained without using a reinforcing material or the like. On the other hand, in the case of a conventional electrolyte membrane containing no synthetic resin, it is difficult to maintain mechanical strength if the thickness is 15 μm or less unless a reinforcing material or the like is used.

  The first electrolyte membrane may include a fibrous reinforcing material from the viewpoint of further increasing the mechanical strength. However, when the fibrous reinforcing material is used, the thickness T1 of the first electrolyte membrane is regulated by the thickness of the fiber. obtain. Therefore, it is preferable that the first electrolyte membrane does not include a fibrous reinforcing material.

  When the laminated electrolyte membrane has a three-layer structure including a pair of second electrolyte membranes sandwiching the first electrolyte membrane from both sides, the thickness (T1) of the first electrolyte membrane is equal to the thickness (T2) of the second electrolyte membrane. It may be larger than. Here, T2 is the thickness of each of the pair of second electrolyte membranes. Therefore, the thickness (T) of the three-layer laminated electrolyte membrane is derived from the equation T = T1 + 2 × T2. By setting T1 ≧ T2, the mechanical strength can be efficiently increased while reducing the overall thickness T of the laminated electrolyte membrane. The ratio of T1 to T2: T1 / T2 satisfies, for example, 1.0 ≦ T1 / T2 ≦ 300, and more preferably satisfies 1.5 ≦ T1 / T2 ≦ 100.

  T1 satisfies, for example, 1 μm ≦ T1 ≦ 150 μm, and T2 satisfies, for example, 0.5 μm ≦ T2 ≦ 50 μm. For example, when it is desired to improve the proton conductivity of the laminated electrolyte membrane, the thickness T of the laminated electrolyte membrane is preferably 15 μm or less. This is because the proton movement distance is shortened, and the proton resistance is reduced. On the other hand, when importance is attached to the gas barrier properties of the laminated electrolyte membrane, the thickness T of the laminated electrolyte membrane is not limited to 15 μm or less, and may be more than 15 μm.

  Next, a fuel cell according to an embodiment of the present disclosure includes the above stacked electrolyte membrane, and a pair of catalyst layers sandwiching the stacked electrolyte membrane from both sides. The catalyst layer may include a third proton conductive polymer. As the third proton conductive polymer, at least one selected from the group consisting of a fluoropolymer and a hydrocarbon polymer can be used.

  The third proton conductive polymer may be the same proton conductive polymer as at least one of the first proton conductive polymer and the second proton conductive polymer. It may be a proton conductive polymer different from the proton conductive polymer.

  When the laminated electrolyte membrane has a three-layer structure including a pair of second electrolyte membranes sandwiching the first electrolyte membrane from both sides, the skeleton of the third proton conductive polymer is the same as the skeleton of the second proton conductive polymer. It is preferred that For example, when the second proton conductive polymer has a tetrafluoroethylene skeleton, the third proton conductive polymer preferably also has a tetrafluoroethylene skeleton. Since the third proton conductive polymer contained in the catalyst layer and the second proton conductive polymer of the second electrolyte membrane in contact with the catalyst layer have the same kind of skeleton, the interface resistance between the catalyst layer and the laminated electrolyte membrane is increased. Can be reduced.

  Hereinafter, a method for manufacturing a three-layer laminated electrolyte membrane including a pair of second electrolyte membranes sandwiching the first electrolyte membrane from both sides will be illustratively described.

[1] Production of First Electrolyte Membrane First, a mixed solution containing a first proton conductive polymer and a synthetic resin or a precursor of a synthetic resin is prepared. The mixed solution may be prepared by any method. For example, it is also possible to prepare a first solution containing the first proton conductive polymer and a second solution containing a synthetic resin or a precursor of a synthetic resin, and mix and prepare the first solution and the second solution. Good. The solvent of the mixed solution, the first solution or the second solution is not particularly limited, but preferably contains at least water from the viewpoint of easy handling. The thickness of the first electrolyte membrane can be controlled by, for example, the concentration of the first proton conductive polymer or the concentration of the synthetic resin or its precursor in the mixed solution.

  Hereinafter, a method for producing the first electrolyte membrane will be further described with respect to typical synthetic resins. The following synthetic resins are all condensable resins that can be formed by condensation of a precursor in a solution or can be formed through ring opening.

(1) When using a polyvinyl acetal resin (here, vinylon) First, a first solution containing a first proton conductive polymer is prepared. As the first proton conductive polymer, for example, perfluorocarbon sulfonic acid or Nafion (Nafion (registered trademark)) can be used. As the solvent of the first solution, a mixed solvent of alcohol and water can be used. As the alcohol, for example, propanol can be used.

  Further, a second solution containing polyvinyl alcohol (PVA), which is a precursor of vinylon, is prepared. For example, water can be used as the solvent of the second solution.

  Next, the first solution and the second solution are mixed, and the obtained mixed solution is cast on a substrate having a smooth surface, and dried to form an intermediate film. The intermediate membrane is a composite of the first proton conductive polymer and PVA. Then, by dipping the intermediate film in an acidic aqueous solution containing formaldehyde, PVA is formalized (acetalized), and vinylon having a crosslinked structure is generated. The formalization reaction is a kind of dehydration condensation reaction. As a result, a first electrolyte membrane in which vinylon, which is a synthetic resin, and the first proton conductive polymer are composited is obtained. Since vinylon has a crosslinked structure, it has excellent mechanical strength.

(2) When using polyimide A second solution containing a polyamic acid is prepared and mixed with the first solution as described above to prepare a mixed solution. Polyamic acid is a precursor of a synthetic resin, polyimide, and is generally synthesized from aromatic diamine and aromatic tetracarboxylic dianhydride as raw materials. Thereafter, an intermediate film may be formed from the mixed solution, and the polyamide acid contained in the intermediate film may be imidized by heating or using an imidizing agent. As a result, a first electrolyte membrane in which the synthetic resin polyimide and the first proton conductive polymer are combined is obtained. The imidization reaction is a dehydration condensation reaction of polyamic acid.

(3) When using a phenol formaldehyde resin A second solution containing a phenol compound is prepared and mixed with the first solution described above to prepare a mixed solution. Thereafter, an intermediate film is formed from the mixed solution, and the intermediate film is immersed in an acidic aqueous solution or an alkaline aqueous solution containing formaldehyde, whereby the addition reaction (formolation) of formaldehyde to the phenol compound and the condensation reaction proceed. As a result, a first electrolyte membrane in which the phenol formaldehyde resin, which is a synthetic resin, and the first proton conductive polymer are composited is obtained. A phenol resin has a three-dimensional crosslinked structure.

(4) When using a melamine formaldehyde resin A second solution containing a melamine compound is prepared and mixed with the first solution as described above to prepare a mixed solution. Thereafter, an intermediate film is formed from the mixed solution, and the intermediate film is immersed in an alkaline aqueous solution containing formaldehyde, whereby the addition reaction (formylation) of formaldehyde to the melamine compound proceeds. Thereafter, by heating the intermediate film, methylol melamine undergoes a polycondensation reaction (methyleneation) and cross-links in a network to form a melamine formaldehyde resin. As a result, a first electrolyte membrane in which the melamine formaldehyde resin, which is a synthetic resin, and the first proton conductive polymer are composited is obtained.

(5) When Urea Resin is Used A second solution containing a urea compound is prepared and mixed with the first solution as described above to prepare a mixed solution. Thereafter, an intermediate film is formed from the mixed solution, and the intermediate film is immersed in an acidic aqueous solution or an alkaline aqueous solution containing formaldehyde, whereby the addition reaction (methylolation) of formaldehyde to the urea compound and the polycondensation reaction (methylenation) proceed. I do. As a result, a first electrolyte membrane in which the urea resin, which is a synthetic resin, and the first proton conductive polymer are combined is obtained.

(6) When Using Polyamide A second solution containing a polyamide precursor is prepared and mixed with the first solution described above to prepare a mixed solution. Thereafter, an intermediate film is formed from the mixed solution, and heat polymerization is performed to produce a polyamide. As a result, a first electrolyte membrane in which the synthetic resin polyamide and the first proton conductive polymer are complexed is obtained. As the polyamide precursor, water-soluble caprolactam, water-soluble AH salt and the like can be used. Caprolactam is a cyclic compound that forms a polymer upon ring opening. The AH salt is an equivalent mixture of a dicarboxylic acid and a diamine. As the dicarboxylic acid, adipic acid, sebacic acid and the like can be used. As the diamine, diaminobutane, hexamethylenediamine, or the like can be used.

[2] Production of second electrolyte membrane Next, a second electrolyte membrane is formed on at least one surface of the first electrolyte membrane, and the first electrolyte membrane and the second electrolyte membrane are integrated. For example, a third solution containing the second proton conductive polymer may be prepared, the third solution may be cast on at least one surface of the first electrolyte membrane, and dried to form a laminated electrolyte membrane. For the second proton conductive polymer, for example, perfluorocarbon sulfonic acid can be used. As the solvent of the second solution, a mixed solvent of alcohol and water may be used. The thickness of the second electrolyte membrane can be controlled, for example, by the concentration of the second proton conductive polymer in the third solution. Note that the second electrolyte membrane may be formed first, and the first electrolyte membrane may be formed so as to be laminated thereon. Further, after forming the laminated film of the intermediate film and the second electrolyte film, the intermediate film may be changed to a synthetic resin.

Hereinafter, the fuel cell according to the present embodiment will be illustratively described.
The fuel cell includes the above-mentioned laminated electrolyte membrane and a pair of catalyst layers sandwiching the laminated electrolyte membrane from both sides. A gas diffusion layer may be disposed on each of the main surfaces of the pair of catalyst layers on the side opposite to the stacked electrolyte membrane.

  FIG. 2 is a schematic cross-sectional view illustrating the structure of the fuel cell (single cell) 10 according to the embodiment of the present disclosure. Usually, a plurality of unit cells 10 are stacked to form a stack, but here, one unit cell 10 is shown alone.

  The single cell 10 includes a membrane electrode assembly (MEA) 5 and an anode-side separator 6A and a cathode-side separator 6B arranged so as to sandwich the membrane electrode assembly 5. The membrane electrode assembly 5 includes a laminated electrolyte membrane 1, an anode catalyst layer 2 </ b> A and an anode gas diffusion layer 3 </ b> A sequentially disposed on one surface side of the laminated electrolyte membrane 1, and a laminated electrolyte membrane 1 on the other surface side of the laminated electrolyte membrane 1. It comprises a cathode catalyst layer 2B and a cathode gas diffusion layer 3B which are arranged, and a pair of seal members 4 which sandwich a peripheral portion of the laminated electrolyte membrane 1. A fuel gas flow path 7A is formed on the surface of the anode separator 6A on the side of the anode gas diffusion layer 3A. An oxidizing gas passage 7B is formed on the surface of the cathode separator 6B on the side of the cathode gas diffusion layer 3B.

  Each catalyst layer includes, for example, a carbon material, catalyst particles supported on the carbon material, and a third proton conductive polymer. As the carbon material, a conductive material such as carbon black and carbon nanofiber can be used. Noble metals such as platinum, cobalt and ruthenium can be used for the catalyst particles.

  Each gas diffusion layer includes, for example, a water-repellent layer having conductivity and a base layer supporting the water-repellent layer. The water repellent layer contains, for example, a conductive agent and a water repellent. Examples of the conductive agent include carbon black. As a water repellent, a carbon paper, a carbon cloth, or the like is used for a base layer including a fluororesin such as polytetrafluoroethylene. Further, a gas diffusion layer having no base material layer may be used. Such a gas diffusion layer can be obtained by forming a mixture containing a conductive agent, a fluororesin and the like into a sheet.

  As a material of each separator, for example, a carbon material, a metal material, or the like can be used. As shown in FIG. 2, a gas flow path can be formed on one surface of each separator by a plurality of concave portions or convex portions.

  Hereinafter, the present disclosure will be described in more detail based on examples. However, the present disclosure is not limited to the following embodiments.

[Example 1]
(1) As a first solution Preparation of Laminated electrolyte membrane, 5 wt% Nafion (registered trademark) solution (DE520,1-propanol / 2-propanol / H 2 O, EW value 1000 g / mol, manufactured by Wako Pure Chemical Co., )It was used.

  As a second solution, an aqueous polyvinyl alcohol (PVA) solution (PVA content: 3.5% by mass) was prepared.

  The first solution and the second solution were mixed at a mass ratio of 95: 5 to obtain a mixed solution.

  As the third solution, the same as the first solution was used.

  First, the third solution was cast on a glass substrate so as to have a thickness of about 2 μm, and dried at room temperature for 12 hours or more to form a second electrolyte membrane. Next, a mixture of the first solution and the second solution was cast on the second electrolyte membrane so as to have a film thickness of about 6 μm, and dried at room temperature for 12 hours or more to form an intermediate film. Finally, the third solution was cast on the intermediate film so as to have a thickness of about 2 μm and dried for 12 hours or more to form a three-layer laminated film.

Next, the laminated film was heat-treated at 60 ° C. for 3 hours and then at 180 ° C. for 3 hours. Thereafter, a formalization reaction of PVA was performed using H ₂ SO ₄ , Na ₂ SO ₄ and HCHO to convert the PVA into vinylon.

Thereafter, activation was performed for 2 hours with boiling water, 2 hours with a 1 M aqueous H ₂ O ₂ solution at 80 ° C., 2 hours with a 1 M aqueous H ₂ SO ₄ solution at 80 ° C., and 2 hours with boiling water. A 10 μm three-layer laminated electrolyte membrane was completed.

(2) Preparation of Catalyst Layer 100 parts by mass of carbon black and 30 parts by mass of catalyst particles (Pt) supported thereon were dispersed in an appropriate amount of water, and an appropriate amount of ethanol was added to the obtained dispersion. And 40 parts by mass of perfluorocarbonsulfonic acid (Nafion (registered trademark), EW value: 1100 g / mol) were further added to prepare a catalyst dispersion for a catalyst layer.

  Next, a catalyst dispersion is applied to a smooth surface of the two PET sheets at a uniform thickness by using a screen printing method, and dried to form an anode catalyst layer and a cathode catalyst layer (thickness: 10 μm). did.

<Preparation of single cell>
The obtained catalyst layers were respectively transferred to both surfaces of the laminated electrolyte membrane, and an anode catalyst layer was formed on one surface of the laminated electrolyte membrane and a cathode catalyst layer was formed on the other surface. Next, a pair of gas diffusion layers including a water-repellent layer containing carbon black and polytetrafluoroethylene as main components and a carbon paper were prepared, and bonded to each catalyst layer to form an anode and a cathode. Next, an MEA was formed by disposing a frame-shaped seal member so as to surround the anode and the cathode. Next, the MEA was sandwiched between the anode-side separator having the fuel gas flow path and the cathode-side separator having the oxidizing gas flow path, thereby completing the single cell A1.

<Evaluation>
Hydrogen gas humidified with steam having a dew point of 65 ° C is supplied to the anode so as to have a utilization rate of 75%, and oxygen gas humidified with steam having a dew point of 65 ° C is supplied to the cathode so as to have a utilization rate of 55%. did. The cell temperature was set at 80 ° C. Then, the current density with respect to the electrode area of the anode and the cathode is varied from 0 to about 3.0 A / cm ² using the load control device, and the IV characteristics, the maximum output density, and the impedance (resistance) of the single cell A1 are measured. did.

[Example 2]
As the perfluorocarbon sulfonic acid used for the first solution, instead of Nafion, a 6% by mass Aquivion (registered trademark) solution (D83-06A, 1-propanol / 2-propanol / H ₂ O, EW value 830 g / mol, Solvay) The procedure was the same as in Example 1 except for the use of Then, in the same manner as in Example 1, a laminated electrolyte membrane having a three-layer structure with a thickness of about 10 μm was produced, and a single cell A2 of a fuel cell was assembled and evaluated.

[Comparative Example 1]
In the same manner as in Example 1 except that a commercially available perfluorocarbon sulfonic acid film (NRE212 (registered trademark), EW value: 1100 g / mol, manufactured by DuPont) having a thickness of 50 μm was used instead of the laminated electrolyte membrane, was used. A single cell B1 of the fuel cell was assembled and evaluated.

  Table 3 shows the relative values (multiples) between the maximum output density and the resistance value of the single cells A1 and A2 when the maximum output density and the resistance value of the single cell B1 are respectively set to 1.

  According to Table 3, it can be understood that the resistance of the single cells A1 and A2 is significantly reduced as compared with the single cell B1, and that the influence of the thickness of the electrolyte membrane is large. Due to the low resistance of the electrolyte membrane, the maximum output density has been greatly improved. In addition, in the case of the single cell A2 in which the EW value of the first electrolyte membrane is lower, it is understood that the resistance hardly increases even in a high current density region, and a high electromotive force can be maintained.

  The laminated electrolyte membrane according to the present disclosure is suitable as a material used for a fuel cell used for, for example, an automobile, a portable electronic device, a power source for outdoor leisure, an emergency backup power source, and the like. In particular, since the effect can be easily obtained at a high current density, it is most suitable for a fuel cell for a high output use.

1: laminated electrolyte membrane, 1a: conventional electrolyte membrane, 2A: anode catalyst layer, 2B: cathode catalyst layer, 3A: anode gas diffusion layer, 3B: cathode gas diffusion layer, 4: seal member, 5: membrane electrode assembly (MEA), 6A: anode side separator, 6B: cathode side separator, 7A: fuel gas flow path, 7B: oxidizing gas flow path, 11: first electrolyte membrane, 12: second electrolyte membrane, 10: fuel cell ( Single cell)

Claims (12)

A first electrolyte membrane including a first proton conductive polymer and a synthetic resin,
A second electrolyte membrane including a second proton conductive polymer and integrated with the first electrolyte membrane;
With
The laminated electrolyte membrane, wherein the synthetic resin is a condensable resin.   The laminated electrolyte membrane according to claim 1, wherein the synthetic resin is at least one selected from the group consisting of a polyvinyl acetal resin, a polyimide, a phenol formaldehyde resin, a melamine formaldehyde resin, a urea resin, and a polyamide.   The at least one of the first proton conductive polymer and the second proton conductive polymer is at least one selected from the group consisting of a fluoropolymer and a hydrocarbon polymer. 3. The laminated electrolyte membrane according to item 1.   The laminated electrolyte membrane according to any one of claims 1 to 3, further comprising a pair of the second electrolyte membranes sandwiching the first electrolyte membrane from both sides.   The laminated electrolyte membrane according to claim 4, wherein the thickness of the first electrolyte membrane is larger than the thickness of the second electrolyte membrane.   The laminated electrolyte membrane according to any one of claims 1 to 5, wherein the thickness of the laminated electrolyte membrane is 15 µm or less.   The laminated electrolyte membrane according to any one of claims 1 to 6, wherein the first electrolyte membrane does not include a fibrous reinforcing material.   The multilayer electrolyte membrane according to any one of claims 1 to 7, wherein the first proton conductive polymer and the second proton conductive polymer have the same kind of skeleton.   The laminated electrolyte membrane according to any one of claims 1 to 8, wherein the content of the synthetic resin in the first electrolyte membrane is 1% by mass or more and 60% by mass or less. A first electrolyte membrane including a first proton conductive polymer and a synthetic resin,
A second electrolyte membrane including a second proton-conducting polymer and integrated with the first electrolyte membrane;
With
The laminated electrolyte membrane, wherein the synthetic resin is at least one selected from the group consisting of polyvinyl acetal resin, polyimide, phenol formaldehyde resin, melamine formaldehyde resin, urea resin, and polyamide. A laminated electrolyte membrane according to any one of claims 1 to 10,
A pair of catalyst layers sandwiching the laminated electrolyte membrane from both sides,
A fuel cell comprising: The catalyst layer includes a third proton conductive polymer,
The fuel cell according to claim 11, wherein the skeleton of the third proton conductive polymer is the same as the skeleton of the second proton conductive polymer.

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