Stability and Performance of Commercial Membranes in High-Temperature Organic Flow Batteries

Redox flow batteries (RFB) often operate at extreme pH conditions and may require cooling to prevent high temperatures. The stability of the battery membranes at these extreme pH-values at high temperatures is still largely unknown. In this paper, a systematic screening of the performance and stability of nine commercial membranes at pH 14 and pH ≤ 0 with temperatures up to 80 °C is conducted in an organic aqueous RFB. Swelling, area resistance, diffusion crossover, battery performance and membrane stability after 40-80 °C temperature treatment are shown, after which a recommendation is made for different user scenarios. The Aquivion E98-05 membrane performed best for both the Tiron/2,7-AQDS battery and the DHPS/Fe(CN)₆ battery at 40 mA/cm², with stable results after 1 week of storage at 80 °C. At 80 mA/cm², E-620-PE performed best in the DHPS/Fe(CN)₆ battery, while Sx-050DK performed best in the Tiron/2,7-AQDS battery.