The hydrogen/bromine flow battery is a promising candidate for large-scale energy storage due to fast kinetics, highly reversible reactions and low chemical costs. However, today's conventional hydrogen/bromine flow batteries use membrane materials (such as Nafion), platinum catalysts, and carbon-paper electrode materials that are expensive. In addition, platinum catalysts can be poisoned and corroded when exposed to HBr and Br-2, compromising system lifetime. To reduce the cost and increase the durability of H-2/Br-2 flow batteries, new materials are developed. The new Nafion/polyvinylidene fluoride electrospun composite membranes have high perm-selectivity at a fraction of the cost of Nafion membranes; the new nitrogen-functionalized platinum-iridium catalyst possesses excellent activity and durability in HBr/Br-2 environment; and the new carbon-nanotube-based Br-2 electrodes can achieve equal or better performance with less materials when compared to baseline electrode materials. Preliminary cost analysis shows that the new materials reduce H-2/Br-2 flow-battery energy-storage system stack and system costs significantly. The resulting advanced H-2/Br-2 flow batteries offer high power, high efficiency, substantially increased durability, and expected reduced cost. (C) The Author(s) 2015. Published by ECS. All rights reserved.