Selectivity enhancement of quaternized poly(arylene ether ketone) membranes by ion segregation for vanadium redox flow batteries

• 来源期刊: 中国科学:化学（英文版）
• 年，卷（期）: 2019,（4）
• 页码范围: 479-490
• 页数: 12页
• 语种: 英文

摘要

Quaternary ammonium densely functionalized octa-benzylmethyl-containing poly(arylene ether ketone)s (QA-OMPAEKs) with ion exchange capacities (IECs) ranging from 1.23 to 2.21 mmol g1 were synthesized from:(1) Ullmann coupling extension of tetra-benzylmethyl-containing bisphenol A;(2) condensation polymerization with activated dihalide in the presence of K2CO3;(3) selective bromination using N-bromosuccinimide;and (4) quantitative quaternization using trimethylamine.Both smallangle X-ray scattering (SAXS) and transmission electron microscope (TEM) characterizations revealed distinct nano-phase separation in QA-OMPAEKs as a result of the dense quaternization.The QA-OMPAEK-20 with an IEC of 1.98 mmol g-1 exhibited a high SO42-conductivity of 1 1.4 mS cm-1 and a low VO2+ permeability of 0.06×10-12 m2 S-1 at room temperature,leading to a dramatically higher ion selectivity than Nafion N212.Consequently,the vanadium redox flow battery (VRFB) assembled with QA-OMPAEK-20 achieved a Coulombic efficiency of 96.9％ and an energy efficiency of 84.8％ at a current density of 50 mA cm-2,which were much higher than those of the batteries assembled with Nafion N212 and a home-made control membrane without distinct nano-phase separation.Therefore,ion segregation is demonstrated to be a strategical route for the design of high performance anion exchange membranes (AEMs) for VRFBs.