Membranes and anion conductive polymers

Patent metadata

Field	Value
Publication number	US-11658322-B2
Application number	US-202017088519-A
Country	US
Kind code	B2
Filing date	Nov 3, 2020
Priority date	Nov 4, 2019
Publication date	May 23, 2023
Grant date	May 23, 2023

Abstract

A major challenge in the development of anion exchange membranes for fuel cells is the design and synthesis of highly stable (chemically and mechanically) and conducting membranes. Membranes that can endure highly alkaline environments while rapidly transporting hydroxides are desired. A design for using cross-linked polymer membranes is disclosed to produce ionic highways along charge delocalized pyrazolium and homoconjugated triptycenes. The ionic highway membranes show improved performance in key parameters. Specifically, a conductivity of 111.6 mS cm−1 at 80° C. was obtained with a low 7.9% water uptake and 0.91 mmol g−1 ion exchange capacity. In contrast to existing materials, these systems have higher conductivities at reduced hydration and ionic exchange capacities, emphasizing the role of the highway. The membranes retain more than 75% of initial conductivity after 30 days of alkaline stability test. This effective water management through ionic highways is confirmed by density functional theory and Monte Carlo studies. A single cell with platinum group metal catalysts at 80° C. showed a high peak density of 0.73 W cm−2 (0.45 W cm−2 from silver-based cathode) and stable performance during 400 h tests.

First claim

What is claimed is:

1. A membrane, comprising:
a cationic polymer comprising a cationic ring;
an anionic species configured to move within the cationic polymer; and
a crosslinker;
wherein a conductivity of the anionic species is at least 100 mS cm −1 ,
wherein the crosslinker crosslinks the cationic polymer, and
wherein a water uptake of the membrane is no more than 50%.

2. The membrane of claim 1 , wherein the cationic polymer comprises a poly(triptycene ether sulfone).

3. The membrane of claim 1 , wherein the crosslinker comprises a pyrazolium ion or a salt thereof.

4. The membrane of claim 1 , wherein the crosslinker is fully substituted.

5. The membrane of claim 1 , wherein a pKa of the cationic ring of the cationic polymer/and or crosslinker is at least 16.

6. The membrane of claim 1 , wherein the water uptake of the membrane is no more than 20%.

7. The membrane of claim 1 , wherein the water uptake of the membrane is no more than 8%.

8. The membrane of claim 1 , wherein the water uptake of the membrane is no more than 5%.

9. The membrane of claim 1 , wherein the membrane is used in an electrochemical cell.

10. The membrane of claim 1 , wherein the membrane is used in a fuel cell.

11. The membrane of claim 1 , wherein the cationic polymer is at least 10% crosslinked by the crosslinker.

12. The membrane of claim 1 , wherein the cationic polymer is at least 40% crosslinked by the crosslinker.

13. The membrane of claim 1 , wherein the cationic polymer is at least 75% crosslinked by the crosslinker.

14. A method of preparing the membrane of claim 1 , comprising:
reacting a cationic polymer comprising a cationic ring with a crosslinker, wherein the crosslinker crosslinks the cationic polymer to form the membrane; and
exposing the membrane to water;
wherein a water uptake of the membrane is no more than 50%.

15. The method claim 14 , wherein the cationic polymer comprises a poly(triptycene ether sulfone).

16. The method claim 14 , wherein the crosslinker comprises a pyrazolium ion or a salt thereof.

17. The method of claim 14 , wherein the anionic species has a conductivity in the membrane of at least 100 mS cm −1 .

18. The method of claim 14 , further comprising substituting C—H bonds on the cationic ring of the cationic polymer and/or the crosslinker.

19. The membrane of claim 1 , wherein the cationic ring of the cationic polymer is fully substituted.

Assignees

• Massachusetts Inst Technology

Inventors

• Swager Timothy Manning
• Grossman Jeffrey C
• Lin Sibo
• Kim Yoonseob
• Wang Yanming
• France-Lanord Arthur
• Wu You-Chi
• Li Yifan
• Wang Yichong

Classifications

• H01M2008/1095

  Fuel cells with polymeric electrolytes · CPC title

• H01M8/1032 Primary

  having sulfur, e.g. sulfonated-polyethersulfones [S-PES] · CPC title

• H01M8/1027

  having carbon, oxygen and other atoms, e.g. sulfonated polyethersulfones [S-PES] · CPC title

• B01J47/12 Primary

  characterised by the use of ion-exchange material in the form of ribbons, filaments, fibres or sheets, e.g. membranes (electrodialysis or electro-osmosis B01D61/42) · CPC title

• H01M2300/0082

  Organic polymers · CPC title