Soft Template-Induced Porous Polyvinylidene Fluoride Membrane for Vanadium Flow Batteries

Abstract

Vanadium flow batteries (VFBs) are considered ideal for grid-scale, long-duration energy storage applications owing to their decoupled output power and storage capacity, high safety, efficiency, and long cycle life. However, the widespread adoption of VFBs is hindered by the use of expensive Nafion membranes. Herein, we report a soft template-induced method to develop a porous polyvinylidene fluoride (PVDF) membrane for VFB applications. By incorporating water-soluble and flexible polyethylene glycol (PEG 400) as a soft template, we induced the aggregation of hydrophilic sulfonated poly (ether ether ketone), resulting in phase separation from the hydrophobic PVDF polymer during membrane formation. This process led to the creation of a porous PVDF membrane with controllable morphologies determined by the polyethylene glycol content in the cast solution. The optimized porous PVDF membrane enabled a stable VFB performance for 200 cycles at a current density of 80 mA/cm², and the VFB exhibited a Coulombic efficiency of 95.2% and a voltage efficiency of 87.8%. These findings provide valuable insights for the development of highly stable membranes for VFB applications.

Keywords

Energy storage / Vanadium flow battery / Porous polyvinylidene fluoride membrane / Soft template-induced phase separation

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