An anion-exchange membrane was prepared using a homogeneous blend mixture of poly(ether sulfone) (PES) and poly(vinylpyrrolidone) (PVP). Advantageous properties of each component were retained in this PES-PVP membrane, such as good mechanical strength, ion selectivity, and excellent hydrophilicity. This membrane can potentially be an alternative candidate for the separator in all-vanadium redox battery systems, given its good ionic conductivity, low permeability of positively charged vanadium ions, resistive property against oxidants, and low cost. Because cross-mixing of the positive and negative electrolytes can be effectively prevented, the coulombic efficiencies were higher than 99% when using these anion-exchange membranes in all-vanadium redox batteries, which is significantly higher than those obtained using expensive Nafion cation-exchange membranes. (C) 2012 Elsevier B.V. All rights reserved.