Toward Cheaper Vanadium Flow Batteries: Porous Polyethylene Reinforced Membrane with Superior Durability

Developing cheap and durable proton exchange membrane is crucial to promote the practical application of vanadium flow batteries (VFB). Here we report a simple and scalable method to fabricate a reinforced sulfonated poly(ether ether ketone) (SPEEK) membrane using a lithium-ion battery separator, ceramic-coated porous polyethylene (CCP), as a robust scaffold. With the confinement effect of the extremely stable CCP substrate, the reinforced SPEEK membrane (S@CCP) shows significantly improved chemical/mechanical stability and reduced vanadium ion permeability compared to the control SPEEK membrane. Accordingly, the S@CCP membrane demonstrates excellent rate performance and cycling stability than those of the benchmark Nafion 212 membrane. It exhibits stable performance over 1500 cycles at 160 mA cm–2 with 99% of CE, 76% of EE and 0.126% of capacity decay per cycle. Meanwhile, the S@CCP membrane is highly resistant to temperature fluctuations over a wide range of −20–60 °C. The superior durability, wide temperature adaptability, and low cost suggest that the S@CCP membrane offers great promise as an ideal membrane for VFB application.