Membranes and separators for redox flow batteries

Ion-exchange membranes are performance- and cost-relevant components of redox flow batteries. Currently used materials are largely ‘borrowed’ from other applications that have different functional requirements. The trend toward higher current densities and the complex transport phenomena of the different species in flow batteries need to be taken into consideration for the design of next-generation membrane/separator materials. In this article, the key requirements and current development trends for membranes and separators for the vanadium redox flow battery are highlighted and discussed.