A Single Substance Organic Redox Flow Battery

Alternative energy sources, such as wind and solar are inherently variable. Steady power to the grid can be achieved by the use of redox flow batteries to store and release power. Redox flow batteries are batteries that use a solution of redox active material that can flow past the electrodes, become charged, and then be stored in an auxiliary tank. Such a battery can have a storage capacity that is much larger than conventional batteries and separates the usual connection between energy and power. Current technology for flow batteries is largely based on sodium/sulfur chemistry which requires high temperatures, or on the aqueous redox chemistry of vanadium. Our project is dedicated to producing redox flow batteries based on organic redox chemistry that can provide high energy density at lower cost, and avoids the use of toxic metals. Our redox chemistry is based on a single substance being both oxidized and reduced, and this is a considerable advantage due to the problems of crossover when two distinct active materials are separated by a membrane. In our Phase I project we prepared new materials for use in a single-substance organic based redox flow battery that were of much higher solubility, affording higher energy density, than the previous examples of this type. This was accomplished by variation of the side groups attached to a redox active core and solubility as high as 2 M was observed. We tested the electrochemical properties, verified the feasibility for use in redox flow applications, and developed a synthetic method for producing these materials on a large scale. The goal of this Phase II project is to demonstrate prototype redox flow batteries based on new, single substance, organic active materials. The overall technical goal will be reached by pursuing three research and development objectives. These objectives are to: (i) optimize these novel organic systems with respect to cycle life duration and efficiency, (ii) select the most effective electrode and membrane combination, and (iii) scale-up the syntheses and do prototype validation. The prototypes will be fabricated at two levels, 3.8 W and 40 W. The 3.8 W prototype will be a single cell device to demonstrate the advantage of the single substance active material and allow optimization of membrane and electrode selection. The 40 W prototype will have a multi-cell stack and will provide data for overall validation of efficiency and durability. Commercial Applications and Other Benefits: The data obtained will be input into modeling software to obtain design parameters for 1-10kW devices. The 10kW device will be offered to customers and investors in the Phase III commercialization. A system at this scale will be a cost effective addition to management of the power grid.