2-Acrylamido-2-methylpropane sulfonic acid (AMPS) grafted poly(vinylidene fluoride) (PVDF) membrane for improved vanadium redox flow battery (VRFB) performance

Polymer modification techniques are crucial for customizing material properties to suit specific applications, particularly in energy storage systems. This study investigates the modification of poly(vinylidene fluoride) (PVDF) membranes via atom transfer radical polymerization (ATRP) to graft 2-acrylamido-2-methylpropane sulfonic acid (AMPS) onto the fluorinated backbone. The successful grafting was confirmed via nuclear magnetic resonance (NMR) spectroscopy, while the membrane structure was evaluated using infrared (IR) and X-ray photoelectron spectroscopies (XPS). Thermogravimetric analysis (TGA) and universal testing machine (UTM) tests verified the thermal and mechanical stability of the membranes. Electrochemical analysis showed sustained performance over 300 cycles. The FluorCat-25 membrane demonstrated high coulombic efficiency (>98 %), voltage efficiency (83 %), and energy efficiency (81 %) at a current density of 100 mA cm⁻². Notably, FluorCat-25 achieved a peak power density of 353 mW cm⁻², surpassing that of Nafion-117 (304 mW cm⁻²), with >85 % capacity retention, indicating its superior performance and suitability for VRFB applications. These findings position FluorCat-25 as a promising candidate for efficient and durable energy storage solutions in VRFB technology.