Densely quaternized anion exchange membranes synthesized from Ullmann coupling extension of ionic segments for vanadium redox flow batteries

作者：Chen, Yu; Lin, Qilang; Zheng, Yuying; Yu, Yan; Chen, Dongyang^*

来源：Science China-Materials, 2019, 62(2): 211-224.

DOI：10.1007/s40843-018-9299-y

• anion exchange membranes
• quaternary ammonium
• poly(fluorenyl ether ketone)s
• Ullmann coupling extension
• phase separation

Membranes with high ion conductivity and selectivity are important for vanadium redox flow batteries. Herein, densely quaternized anion exchange membranes based on quaternary ammonium functionalized octa-benzylmethyl-containing poly(fluorenyl ether ketone)s (QA-OMPFEKs) were prepared from the (i) condensation polymerization of a newly developed octa-benzylmethyl-containing bisphenol monomer via Ullmann coupling, (ii) bromination at the benzylmethyl sites using N-bromosuccinimide, and (iii) quaternization of the bromomethyl groups using trimethylamine. The QA-OMPFEK-20 with an ion exchange capacity (IEC) of 1.66 mmol g(-1)exhibited a higher SO42- conductivity (9.62 mS cm(-1)) than that of the QA-TMPFEK-40 (4.82 mS cm(-1)) at room temperature, which had a slightly higher IEC of 1.73 mmol g(-1) but much lower QA density. The enhanced SO42- conductivity of QA-OMPFEK-20 was attributed to the ion-segregated structure arising from the densely anchored QA groups, which was validated by SAXS observation. Furthermore, the QA-OMPFEK-20 showed much lower VO2+ permeability (1.24x10(-)(14)m(2)s(-1)) than QA-TMPFEK-40 (5.40x10(-)(13)m(2)s(-1)) and Nafion N212 (5.36x10(-12)m(2)s(-1)), leading to improved Coulombic and energy efficiencies in Vanadium redox flow batteries (VRFBs). Therefore, the Ullmann coupling extension is a valuable approach for the development of high performance anion exchange membranes for VRFBs.

• 出版日期2019-2
• 单位福州大学