Highly Selective Proton-Conducting Composite Membranes for Redox Flow Batteries

Redox flow batteries (RFBs) are a type of electrical energy storage device in which the reactants (and reaction products) are stored in liquid tanks. Redox flow batteries have many advantages over conventional batteries, and when fully developed could provide the utility industry with improved methods for dynamic operation of the electricity supply grid by providing energy storage for load leveling and peak shaving. Redox flow batteries also provide a means to store intermittent renewable energy from solar and wind sources. However important technical developments are needed if redox flow batteries are to fulfill their commercial potential. Most redox flow batteries require the use of ion exchange membranes, typically in the form of perfluorinated acid polymer membranes. Unfortunately, this type of membrane is expensive and is poorly selective, reducing the efficiency of the device. The Phase I study successfully demonstrated a composite ion exchange membrane which several attractive features for use in redox flow batteries, including, high proton conductivity, low permeability to reactive species, potential for scalable manufacturing from low cost starting materials and good stability in an aggressive liquid electrolyte. In vanadium redox flow battery performance tests, the composite membrane demonstrated superior technical performance characteristics over the standard perfluorinated acid polymer membrane. Further development of the composite membrane will reduce the purchase cost of redox flow batteries, providing improvements in efficiencies, performance, and durability. During Phase II, Lynntech will further advance the performance characteristics of the composite membrane and will demonstrate the membranes electrochemical performance capabilities over a range of test conditions, in a variety of use scenarios. The Phase II study will also address industrialization of the membrane production process. The proposed research will contribute significantly to the development of low-cost and durable stationary power systems, which ultimately have the potential to change the way in which electrical energy is generated, distributed, marketed, and used.