Polydopamine coated SPEEK membrane for a vanadium redox flow battery

In this work, sulfonated poly(ether ether ketone) (SPEEK) membranes have been first modified by a polydopamine (PDA) coating and then investigated as an ion exchange membrane for a vanadium redox flow battery (VRFB). The SEM results showed that the PDA film was successfully coated on the surface of the SPEEK membrane. The PDA film can serve as a blocking layer to protect the substrate SPEEK membrane from being corroded by the highly oxidative vanadium electrolyte. The obtained PDA coated SPEEK membranes showed much lower vanadium ion permeability, accompanied by higher mechanical strength and thermal stability than the pristine SPEEK membrane. Consequently, the VRFB with the optimal PDA/SPEEK membrane exhibited much higher coulombic efficiency and better discharge capacity retention than the pristine SPEEK membrane. This indicates that the PDA coated SPEEK membranes are of significant interest for VRFB applications.