Sulfonated 3D Printed Poly(ether Ether Ketone) Membrane Coated with Polydopamine for Application in Vanadium Redox Flow Batteries

Ion exchange membranes used in Vanadium Redox Flow Batteries (VRFB) must combine high proton conductivity with low vanadium ion permeability, something of a hurdle since these two types of ions move mainly through the membrane's hydrophilic regions. A novel approach to address this hurdle is by 3D printing sulfonated poly(ether ether ketone) membranes which are then coated with dopamine. 3D printing makes it possible to manufacture precise and regular structures, while sulfonation ensures the attachment of SO3H groups in wellstructured spaces of the membrane, thus promoting the transport of protons. Coating the membrane with polydopamine reduce the permeation of vanadium ions while enhancing chemical stability of the membrane. The 3D-SPEEK/PDA membranes therefore exhibited good properties against Nafion211, Fap450 and conventional SPEEK membranes. Moreover, the optimal application of a PDA coating on the 3D-SPEEK support membrane yielded cell performance (CE:-100%) at 100 mA.cm(-2) higher than the commercial membranes Nafion211 and Fap450 (CE:- 94% and 98%, respectively), as well as conventional SPEEK (CE:-97%). Meanwhile, the single cell assembled with the 3D-printed membrane exhibits a lower self-discharge rate and a more robust cyclic stability, thus demonstrating the great prospects of this 3D-SPEEK/PDA membrane for use in VRFB applications.