High-performance SAnPEK membranes with selective porogen-induced ion transport channels for aqueous organic redox flow batteries

Aqueous organic redox flow batteries (AORFBs) have attracted extensive attention as a promising energy storage technology, but they still face challenges in developing high-performance membranes, especially membranes with high ionic conductivity, selectivity, and excellent stability. In this work, a new strategy of selective porogen-induced ion transport channels formation is used to construct highly conductive and selective ion transport channels in low-sulfonated SAnPEK membranes. The original SAnPEK-virgin membrane exhibits a high area resistance of 0.93 Ωcm². The SAnPEK-3 membrane, which is made by adding only 1.82 wt% of the selective porogen sodium p-hydroxybenzenesulfonate, exhibits a low area resistance of 0.257 Ωcm², which is 37.6 % of the SAnPEK-virgin membrane and even lower than the benchmark Nafion212 membrane (0.276 Ωcm²). The SAnPEK-3 membrane also exhibits excellent selectivity and high mechanical strength (39.2 MPa). In AORFB, the SAnPEK-3 membrane shows an energy efficiency of up to 91.47 % at 40 mA cm⁻², which is better than the commercial Nafion117 membrane (82.95 %) and Nafion212 membrane (90.86 %). Moreover, the SAnPEK-3 membrane shows excellent cycle stability in 9600 cycle tests. The proposed method for preparing membranes with selective porogen-induced ion transfer channels can significantly improve membrane conductivity and is easy to scale up.