Triblock copolymer based anion exchange membranes (AEMs) as separators in electrochemical devices
The present disclosure is directed to triblock copolymer based anion exchange membranes (AEMs) and methods for making same. The membranes are useful as separators in electrochemical devices, such as fuel cells, electrolyzers, and redox flow batteries.
1. An acid stable anion exchange membrane (AEM) comprising:
a chloromethylated polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) triblock copolymer, wherein a chloromethylation reaction yielding the chloromethylated SEBS triblock copolymer comprises chlorobenzene; and
one or more functionalizing cations.
2. The acid stable AEM of claim 1 , wherein the one or more functionalizing cations comprise at least one trimethylamine (TMA) cation.
3. The acid stable AEM of claim 1 , wherein a molar ratio of styrene to (ethylene-ran-butylene) is from 30:70 to 55:45.
4. The acid stable AEM of claim 1 , wherein a perm-selectivity is at least about 70%.
5. A redox flow battery comprising the acid stable AEM of claim 1 , wherein a current efficiency of the redox flow battery is at least about 97%.
6. The acid stable AEM of claim 1 , having a chloride ion conductivity at 70° C. of less than about 30 mS/cm.
7. The acid stable AEM of claim 1 , having an ion exchange capacity of less than about 1.75 mmol/g.
8. A method for preparing an acid stable anion exchange membrane (AEM) comprising:
chloromethylating a polystyrene-block-poly(ethylene-ran-butylene)-block-polystyrene (SEBS) triblock copolymer, wherein the chloromethylating comprises dissolving the SEBS triblock copolymer in chlorobenzene to form a mixture and allowing the mixture to react at about 80° C. for about 7 days; and
functionalizing the SEBS triblock copolymer with at least one cation.
9. The method of claim 8 , wherein the functionalizing is conducted at about 30° C. and for about 2 days.
10. The method of claim 8 , wherein the at least one cation is a trimethylamine (TMA) cation.
11. The method of claim 8 , wherein a molar ratio of styrene to (ethylene-ran-butylene) is from 30:70 to 55:45.