Double-Layered Anion Exchange Membrane for Enhanced Aqueous Organic Redox Flow Battery Performance

Anion exchange membranes (AEMs) serve as critical components in aqueous organic redox flow batteries (AORFBs), yet their development is hindered by challenges including high resistance, elevated costs, and insufficient mechanical strength and durability. Here, we present a high-performance double-layered membrane (DLM) that overcomes these limitations. The DLM consists of a thin quaternized poly(alkyl-terphenylpyridinium) (QPAT) active layer and a hybrid support layer comprising a porous polyethylene (PE) scaffold infused with a QPAT polymer. The PE scaffold reinforces mechanical strength, allowing the membrane to remain stable even at reduced thickness, thereby achieving lower resistance. The hybrid layer’s dense structure and limited ion channels effectively prevent electrolyte crossover. Notably, the pure QPAT active layer in the DLM is only 1.8 μm thick, and the thickness of the wet membrane for DLM is merely 8% of the minimum thickness of conventional pure AEM’s wet membrane thickness, resulting in a 3% improvement in energy efficiency and a substantial reduction in material costs. In long-term cycling tests, the DLM exhibits outstanding durability, with a minimal discharge capacity decay rate of 0.0045% per hour, two-fifths that of standard QPAT membranes. These findings demonstrate that DLM combines superior mechanical strength, low ionic transport resistance, cost-efficiency, and long-term performance, providing a transformative solution for advancing AORFB technologies.