Preparation and characterization of a novel layer-by-layer porous composite membrane for vanadium redox flow battery (VRB) applications

•LbL/porous-SPFEK composite membrane was prepared by a facile approach.•The pore was produced by introducing imidazole followed by extraction removing.•The pores introduced into the membrane can make the proton conductivity increased.•The LbL bilayers can reduce vanadium ions diffusion of the composite membranes.•VRB-SPFEK-20.7imidazole-(PDDA/PSS)8 showed the highest CE of 92.5% at 30 mA cm−2.

By the solution casting method, a novel porous membrane has been prepared for VRB by doping sulfonated poly(fluorenyl ether ketone) (SPFEK) with imidazole, and then imidazole was washed out by extraction with solution. The proton conductivity of porous membrane increased with increasing the content of imidazole, but proton/vanadium ion (H/V) selectivity decreased. Layer-by-layer (LbL) technique was used to improve the porous membrane with high selectivity. Moreover, the performance of VRB using SPFEK-20.7imidazole-(PDDA/PSS)8 membrane which is doped with 20.7 wt.% content of imidazole and then removed imidazole, and then deposited with eight LbL bilayers exhibits the highest columbic efficiency (CE) of 92.5% at 30 mA cm−2.

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