High-performance aqueous organic redox flow battery enabled by sulfonated anthrone-containing poly(aryl ether ketone) membranes

Aqueous organic redox flow batteries (AORFBs) have become a promising electrochemical energy storage technology due to their low cost, high safety, and sustainability. As key components of emerging AORFBs, membranes face challenges such as scarcity of available membranes and high prices. Moreover, currently available membranes have low battery performance because these membranes are not optimized for specific AORFBs. In this work, a new cation exchange membrane sulfonated anthrone-containing poly(aryl ether ketone) (SAnPEK) membrane was prepared for the first time and achieved significantly improved performance in (SPr)2V/K4[Fe(CN)6] AORFBs. SAnPEK membrane has excellent selectivity and high mechanical strength (> 50 MPa). SAnPEK membranes exhibit high conductivity in 1M NH4Cl solution. For example, SAnPEK-4 membranes exhibit low surface resistance (0.176 Ωcm2) in 1M NH4Cl solution, which is significantly better than Nafion117 (1.02 Ωcm2) and Nafion212 membranes (0.276 Ωcm2). SAnPEK membrane exhibtis impressive performance in (SPr)2V/K4[Fe(CN)6] AORFB. The SAnPEK-4 membrane exhibits high coulombic efficiency (CE) and excellent energy efficiency (EE) (CE=99.1%, EE=83.4% at 100 mAcm-2), and the EE for SAnPEK-4 membrane is significantly better than that for the Nafion117 membrane (CE=99.3%, EE=62.4%) and Nafion212 membrane (CE=99.1%, EE=80.8%, 100 mAcm-2). In addition, the SAnPEK-4 membrane exhibits excellent cycle stability over 3000 cycles in AORFB. As a high-performance, easy-to-prepare, low-cost cation exchange membrane, SAnPEK membranes have good application potential in AORFBs.