Electrolyte membrane, process for its production and polymer electrolyte fuel cell

• US 20050186461A1
• Filed: 03/30/2005
• Published: 08/25/2005
• Est. Priority Date: 09/30/2002
• Status: Active Grant

• Current Assignee: Asahi Glass Company, Limited (AGC, Inc.)
• Original Assignee: Asahi Glass Company, Limited (AGC, Inc.)
• Inventors: Hommura, Satoru, Higuchi, Yoshiaki, Kusano, Hiromitsu
• Granted Patent: US 7,749,629 B2
• Time in Patent Office: Days
• US Class Current: 429/483
• CPC Class Codes: C08J 5/22 Films, membranes or diaphragms
• CPC Class Codes: H01B 1/122 Ionic conductors
• CPC Class Codes: H01M 8/10 Fuel cells with solid electrolytes
• CPC Class Codes: H01M 8/1004 characterised by membrane-electrode assemblies [MEA] H01M8/12 takes precedence
• CPC Class Codes: H01M 8/1023 having only carbon, e.g. polyarylenes, polystyrenes or polybutadiene-styrenes
• CPC Class Codes: H01M 8/1039 halogenated, e.g. sulfonated polyvinylidene fluorides
• CPC Class Codes: H01M 8/106 characterised by the chemical composition of the porous support
• CPC Class Codes: H01M 8/1062 characterised by the physical properties of the porous support, e.g. its porosity or thickness
• CPC Class Codes: Y02E 60/50 Fuel cells
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product

Abstract

An electrolyte membrane characterized by comprising a porous body formed from a melt-moldable fluororesin and having interconnected pores and an ion exchange resin with which the interconnected pores are filled, is provided. Specifically, the porous body is formed, for example, from an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, a tetrafluoroethylene/[CF₂═CF—(OCF₂CFY)_a—O_c—(CF₂)_b—SO₃H] copolymer (wherein Y is a fluorine atom or a trifluoromethyl group, a is an integer of 0 to 3, b is an integer of from 0 to 12, and c is 0 or 1, provided that when b=0, C=0), or the like. An electrolyte membrane reinforced by such a porous body has high mechanical strength even if it is thin, and is excellent in dimensional stability when hydrated, and a polymer electrolyte fuel cell with a membrane-electrode assembly having the electrolyte membrane provides a high output and is excellent in durability.

Claims

1. An electrolyte membrane characterized by comprising a porous body formed from a melt-moldable fluororesin and having interconnected pores and an ion exchange resin with which the interconnected pores are filled.

2. The electrolyte membrane according to claim 1, wherein the ion exchange resin is made of a perfluorocarbon polymer having sulfonic acid groups.

3. The electrolyte membrane according to claim 2, wherein the perfluorocarbon polymer is a copolymer comprising polymerization units derived from tetrafluoroethylene and polymerization units derived from CF₂═

CF—

(OCF₂CFX)_m—

O_p—

(CF₂)_n—

SO₃H (wherein X is a fluorine atom or a trifluoromethyl group, m is an integer of from 0 to 3, n is an integer of from 0 to 12, and p is 0 or 1, provided that when n=0, p=0).

4. An electrolyte membrane characterized by comprising a porous body formed from at least one member selected from the group consisting of an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotrifluoroethylene, an ethylene/chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride and a tetrafluoroethylene/[CF₂═

CF—

(OCF₂CFY)_a—

O_c—

(CF₂)_b—

SO₃H] copolymer (wherein Y is a fluorine atom or a trifluoromethyl group, a is an integer of from 0 to 3, b is an integer of from 0 to 12, and c is 0 or 1, provided that when b=0, c=0) and having interconnected pores and an ion exchange resin with which the interconnected pores are filled.

5. The electrolyte membrane according to claim 4, wherein the ion exchange resin is made of a perfluorocarbon polymer having sulfonic acid groups.

6. The electrolyte membrane according to claim 5, wherein the perfluorocarbon polymer is a copolymer comprising polymerization units derived from tetrafluoroethylene and polymerization units derived from CF₂═

CF—

(OCF₂CFX)_m—

O_p—

(CF₂)_n—

SO₃H (wherein X is a fluorine atom or a trifluoromethyl group, m is an integer of from 0 to 3, n is an integer of from 0 to 12, and p is 0 or 1, provided that when n=0, p=0).

7. A process for producing an electrolyte membrane, which comprises mixing and kneading a melt-moldable fluororesin and an inorganic bulking agent, forming the mixture into a film, orientating the obtained film to form it into a porous body having a porosity of from 20 to 95%, and filling the porous body with an ion exchange resin.

8. The process for producing an electrolyte membrane according to claim 7, wherein the fluororesin is at least one member selected from the group consisting of an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotrifluoroethylene, an ethylene/chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride and a tetrafluoroethylene/[CF₂═

CF—

(OCF₂CFY)_a—

O_c—

(CF₂)_b—

SO₂F] copolymer (wherein Y is a fluorine atom or a trifluoromethyl group, a is an integer of from 0 to 3, b is an integer of from 0 to 12, and c is 0 or 1, provided that when b=0, c=0).

9. The process for producing an electrolyte membrane according to claim 7, wherein the film is orientated by laminating an assist film thereon.

10. A process for producing an electrolyte membrane, which comprises mixing and kneading at least one fluororesin selected from the group consisting of an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotrifluoroethylene, an ethylene/chlorotrifluoroethylene copolymer, polyvinylidene fluoride and polyvinyl fluoride, with a tetrafluoroethylene/[CF₂═

CF—

(OCF₂CFY)_a—

O_c—

(CF₂)_b—

SO₂F] copolymer (wherein Y is a fluorine atom or a trifluoromethyl group, a is an integer of from 0 to 3, b is an integer of from 0 to 12, and c is 0 or 1, provided that when b=0, c=0), forming the mixture into a film, orientating the obtained film to form it into a porous body having a porosity of from 20 to 95%, and filling the porous body with an ion exchange resin.

11. The process for producing an electrolyte membrane according to claim 10, wherein the film is orientated by laminating an assist film thereon.

12. The process for producing an electrolyte membrane according to claim 10, wherein after the porous body is prepared by orientation, or after the film is formed and before it is orientated, hydrolysis and a conversion treatment into an acid form are carried out.

13. A polymer electrolyte fuel cell, which has a membrane-electrode assembly comprising

an electrolyte membrane comprising a porous body formed from a melt-moldable fluororesin and having interconnected pores and an ion exchange resin with which the interconnected pores are filled, and

electrodes comprising catalyst layers containing a catalyst and an ion exchange resin and to be disposed on both sides of the electrolyte membrane, and gas diffusion layers to be disposed on both sides.

14. A polymer electrolyte fuel cell, which has a membrane-electrode assembly comprising

an electrolyte membrane comprising a porous body formed from at least one member selected from the group consisting of an ethylene/tetrafluoroethylene copolymer, a tetrafluoroethylene/perfluoro(alkyl vinyl ether) copolymer, a tetrafluoroethylene/hexafluoropropylene copolymer, polychlorotrifluoroethylene, an ethylene/chlorotrifluoroethylene copolymer, polyvinylidene fluoride, polyvinyl fluoride and a tetrafluoroethylene/[CF₂═

CF—

(OCF₂CFX)_r—

O_t—

(CF₂)_s—

SO₃H] copolymer (wherein Y is a fluorine atom or a trifluoromethyl group, r is an integer of from 0 to 3, s is an integer of from 0 to 12, and t is 0 or 1, provided that when s=0, t=0) and having interconnected pores and an ion exchange resin with which the interconnected pores are filled, and

electrodes comprising catalyst layers containing a catalyst and an ion exchange resin and to be disposed on both sides of the electrolyte membrane, and gas diffusion layers to be disposed on both sides.