A blend membrane consisting of sulfonated poly(ether sulfone) (SPES) and sulfonated poly(ether ether ketone) (SPEEK) (we name it as SPES/SPEEK membrane) for vanadium redox flow battery (VRB) has been fabricated and characterized. The swelling behavior and water uptake of SPES/SPEEK membrane are evaluated in terms of the morphology phase characterization by atom force microscopy (AFM). The results indicate that SPES/SPEEK membrane possesses significantly strong mechanical strength, high water uptake and low permeability of VO2+ ions. The performance of VRB single cell with SPES/SPEEK membrane shows significantly lower charge capacity loss, higher coulombic efficiency (CE) and energy efficiency (EE) (98% vs. 91% and 84% vs. 79.5%, respectively) compared to that with Nafion 212 membrane. Furthermore, the SPES/SPEEK membrane presents good cell performance up to 100 cycles (more than 265 h) with no significant decline in CE and EE. With all the good properties and low cost, the SPES/SPEEK membrane shows promising prospects for application in VRB. (c) 2012 Elsevier B.V. All rights reserved.