Composite electrolyte with crosslinking agents

• US 6,962,959 B2
• Filed: 08/28/2003
• Issued: 11/08/2005
• Est. Priority Date: 08/28/2003
• Status: Expired due to Fees

• Current Assignee: Hoku Corp.
• Original Assignee: Hoku Scientific, Inc.
• Inventors: Taft, Karl Milton III, Kurano, Matthew Robert, Panambur, Gangadhar, Mada Kannan, Arunachala Nadar
• Primary Examiner(s): Cheung, William K.
• Application Number:
  US10/653,016
• Publication Number:
  US 20050048341A1
• Time in Patent Office: 803 Days
• Field of Search: 429/30, 429/33, 521/27, 525/326.1, 525/328.4, 525/328.5
• US Class Current: 525/326.1
• CPC Class Codes: C08G 65/4056 (I) or (II) containing sulfur as the sulfone group C08G75/23
• CPC Class Codes: C08G 65/48 Polymers modified by chemical after-treatment
• CPC Class Codes: C08G 75/24 Polysulfonates
• CPC Class Codes: C08J 5/2218 Synthetic macromolecular compounds
• CPC Class Codes: H01M 2300/0082 Organic polymers
• CPC Class Codes: H01M 2300/0091 in the form of mixtures
• 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 8/1025 having only carbon and oxygen, e.g. polyethers, sulfonated polyetheretherketones [S-PEEK], sulfonated polysaccharides, sulfonated celluloses or sulfonated polyesters
• CPC Class Codes: H01M 8/1027 having carbon, oxygen and other atoms, e.g. sulfonated polyethersulfones [S-PES]
• CPC Class Codes: H01M 8/1032 having sulfur, e.g. sulfonated-polyethersulfones [S-PES]
• CPC Class Codes: H01M 8/1039 halogenated, e.g. sulfonated polyvinylidene fluorides
• CPC Class Codes: H01M 8/1051 Non-ion-conducting additives, e.g. stabilisers, SiO2 or ZrO2
• CPC Class Codes: H01M 8/1072 by chemical reactions, e.g. insitu polymerisation or insitu crosslinking
• CPC Class Codes: H01M 8/1081 starting from solutions, dispersions or slurries exclusively of polymers
• 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

A covalent crosslinking of ion-conducting materials via sulfonic acid groups can be applied to various low cost electrolyte membrane base materials for improved fuel cell performance metrics relative to such base material. This proposed approach is due, in part, to the observation that many aromatic and aliphatic polymer materials have significant potential as proton exchange membranes if a modification can increase their physical and chemical stabilities without sacrificing electrochemical performance or significantly increasing the material and production costs.

Claims

1. A method for improving the physical and mechanical properties of ion-conducting materials, comprising:

providing an ion conducting base material;

providing a crosslinking agent; and

incorporating the crosslinking agent into the ion-conducting base material through hydroxyl and sulfonic acid condensation or through amine and sulfonic acid condensation.

2. A method as in claim 1, wherein the incorporation takes place in a non-aqueous environment.

3. A method as in claim 1, wherein the crosslinking agent has a chain that includes an aromatic polymer chain, an aliphatic polymer chain, an organic or inorganic polymer network, or any combination thereof.

4. A method as in claim 1, wherein, in addition to one or more of amine, hydroxyl, or sulfonic acid groups, the crosslinking agent has at least one functional group to form a covalent crosslinking bond with the ion conducting base material.

5. A method as in claim 1, wherein the ion conducting base material is an organically-based material, an inorganically-based material, or a composition thereof.

6. A method as in claim 1, wherein the ion conducting base material is organically based and containing aromatic or aliphatic structure.

7. A method as in claim 6, wherein the aromatic structure includes poly-aryl ether ketones and poly-aryl sulfones.

8. A method as in claim 6, wherein the aliphatic structure includes perflourinated or styrene co-polymer types.

9. A method as in claim 1, wherein the ion conducting base material contains one or more inorganic additives.

10. A method as in claim 9, wherein the inorganic additive is selected from the group consisting of clay, zeolite, hydrous oxide, and inorganic salt.

11. A method as in claim 10, wherein the clay includes an aluminosilicate-based exchange material selected from the group consisting of montmorillonite, kaolinite, vermiculite, smectite, hectorite, mica, bentonite, nontronite, beidellite, volkonskoite, saponite, magadite, kenyaite, zeolite, alumina, rutile.

12. A method as in claim 1, wherein the ion conducting base material has a given molecular weight and/or polymer structures with functional groups that include sulfonic acids, phosphoric acids, carboxylic acids, imidazoles, amines, and amides.

13. A method as in claim 1, wherein the crosslinking agent is hydroxyl terminated and the ion conducting base material is sulfonated, and wherein the incorporation includes direct covalent crosslinking between the hydroxyl terminated crosslinking agent and the sulfonated ion-conducting base material such that their reaction is in the form of

HO—

R₁—

OH+2(HSO₃)—

R₂→

R₂—

SO₂—

O—

R₁—

O—

SO₂-R₂+2HO

where R₁ is the hydroxyl terminated crosslinking agent'"'"'s main chain and R₂ is the sulfonated ion conducting base material.

14. A method as in claim 13, wherein the main chain includes one or more chains selected from a group consisting of an aromatic polymer chain, an aliphatic polymer chain, organic molecules and inorganic molecules.

15. A method as in claim 13, wherein the sulfonated ion conducting base material includes, one or more chains selected from a group consisting of an aromatic polymer chain, an aliphatic polymer chain, organic molecules and inorganic molecules.

16. A method as in claim 1, wherein the crosslinking agent is amine terminated and the ion conducting base material is sulfonated, and wherein the incorporation includes direct covalent crosslinking between the amine terminated crosslinking agent and the sulfonated ion-conducting base material such that their reaction is in the form of

H₂N—

R₁—

N—

H₂+2(HSO₃)—

R₂→

R₂—

SO₂—

NH—

R₁—

NH—

SO₂-R₂+2H₂O

where R₁ is the amine terminated crosslinking agent'"'"'s main chain and R₂ is the sulfonated ion conducting base material.

17. A method as in claim 1, wherein the crosslinking agent is sulfonic acid terminated and the ion conducting base material is amine or hydroxyl terminated, and wherein the incorporation includes direct covalent crosslinking between the sulfonic acid terminated crosslinking agent and the amine or hydroxyl terminated base ion-conducting material such that their reaction is in the respective form of

HO₃S—

R₃—

SO₃H+2(HO)—

R₄→

R₄—

SO₂—

O—

R₃—

O—

SO₂-R₄+2H₂O

or

HO₃S—

R₃—

SO₃H+2(H₂N)—

R₄→

R₄—

SO₂—

NH—

R₃—

NH—

SO₂-R₄+2H₂O

where R₃ is the sulfonic acid terminated crosslinking agent'"'"'s main and R₄ is the amine or hydroxyl terminated ion conducting base.

18. A method as in claim 1, wherein incorporation involves a reaction solvent, including a high boiling point, non-polar solvent selected from a group consisting of dimethyl sulfoxide (DMSO), n-methyl pyrrolidinone (NMP), dimethyl acetamide (DMAC) and dimethylformamide (DMF).

19. A method as in claim 1, wherein incorporation proceeds under azeotrophic distillation via a removal of water by toluene to facilitate reaction kinetics.

20. A method as in claim 1, wherein incorporation involves 0.1% to 8% crosslinking agent'"'"'s molar equivalents with respect to ion conducting base material'"'"'s sulfonic acid sites.

21. A method as in claim 1, wherein incorporation involves 0.1% to 8% cross linking agent'"'"'s molar equivalents with respect to ion conducting base material'"'"'s amine or hydroxyl group sites.

22. A method as in claim 1, wherein the ion conducting base material contains an inorganic cation exchange material.

23. A method as in claim 22, wherein the inorganic cation exchange material is selected from a group consisting of clay, zeolite, hydrous oxide, and inorganic salt.

24. A method as in claim 22, wherein the inorganic cation exchange material further includes a silica based material and a proton conducting polymer based material.

25. A method for adding functionality to ion-conducting materials, comprising

providing an ion conducting based material;

providing a crosslinking agent; and

incorporating the modified crosslinking agent into the ion-conducting base material through hydroxyl and sulfonic acid condensation or through amine and sulfonic acid condensation.