3RD INTERNATIONAL CONGRESS ON TECHNOLOGY - ENGINEERING & SCIENCE - Kuala Lumpur - Malaysia (2017-02-09)

Anion Exchange Membrane Based On Poly(arylene Ether Ketone) For Vanadium Redox Flow Battery Applications
Renewable energy has been considered as solution for energy and environmental problems because the amount is unlimited and it is eco-friendly energy source. But it has drawbacks such as intermittent supply and low efficiency because it relies on natural phenomena. To overcome this problem, energy storage system (ESS) is needed. By using ESS, the excess amount of generated electricity can be saved and saved energy can be used whenever it is needed. Vanadium redox flow battery (VRFB) is one kind of ESS, which converts electricity to chemical energy by redox reaction in each electrolyte tank. For the operation of VRFB, ion exchange membrane plays important role. Ion exchange membrane provides ion transfer channel for charge carriers, and it prevents electrolyte of each electrode from cross-mixing. Commercially, Nafion membrane is used for ion exchange membrane for VRFB. Although Nafion has high proton conductivity and good chemical stability, high vanadium ion permeability, which is main factor of self-discharge reaction, is major defect to be used in VRFB. So many researches have been conducted to find substitute for Nafion. Among various materials, hydrocarbon based polymer attracts researchers for its low cost, simple synthetic process. In this study, anion exchange membrane (AEM) based on poly(arylene ether ketone) (PAEK) with imidazolium group is synthesized for vanadium redox flow battery application. PAEK is one of the hydrocarbon based polymer which has good mechanical and chemical stability, and it can be modified easiliy by introducing functional groups. Imidazolium group is one kind of positively charged functional groups, which can reduce permeability of vanadium ion by Donnan exclusion phenomena. The PAEK backbone is synthesized from polycondensation reaction of 4,4’-bis(4-hydroxyphenyl) valeric acid with 4,4-difluorobenzophenone, and the imidazolium group was introduced using 1,3-aminopropyl imidazole. The chemical structure of synthesized polymer was confirmed by 1H-NMR. The ion exchange capacity of synthesized membrane showed higher IEC than Nafion. In addition, synthesized membranes showed much lower vanadium ion permeability than Nafion. Durability is also important property for ion exchange membrane. The cycling charge-discharge test with 35 cycles was conducted with synthesized membrane, and it did not show significant degradation of performance.
Dukjoon Kim, Yeonho Ahn