Synthesis and characterization of anion exchange blend membranes for vanadium redox flow battery applications

Abstract

Due to the increasing concerns of fossil fuel using and environmental issues, the world needs to develop renewable energy sources and clean energy conversion devices, e.g. fuel cells, flow batteries and electrolyzers. Vanadium redox flow batteries (VRFBs) are considered promising energy storage system for large scale applications due to their long cycle lives, low cost, design flexibility and safety. Ion exchange membrane (IEM) is polymeric material composed of ionic head groups as fixed ions in polymeric backbone and transportable ions. Those types of membranes can be used in various applications which are energy related devices mentioned above. Therefore, developments of ion exchange membranes are required with improved properties to increase the efficiency of energy applications. Aim of this work is to develop ion exchange membranes with improved properties and to display better performances in VRFB compared to commercial reference membranes. Because currently available IEMs in VRFBs are limited due to fast vanadium ions cross-over or/and low ionic conductivity resulting in low performances in the battery. To overcome those drawbacks and to be used in vanadium redox flow battery, ion exchange membranes were developed either by blending or via new synthetic procedures. Thus, novel ion exchange polymers and/or membranes were developed, analyzed and applied in vanadium redox flow battery. In this dissertation, therefore, polymers synthesis, membranes preparation and applications of ion exchange membranes have been studied. This dissertation is divided into mainly three parts. The first part introduces a general background of the subject regarding ion conducting polymers and applications in vanadium redox flow battery. The second part is the papers published during the thesis work. The last part of this dissertation is overall discussion on the results and summary.