A Single Substance Organic Redox Flow Battery
Redox flow batteries (RFBs) 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. RFB & apos;s will be a vital part of a power grid based on alternative energy sources, such as wind and solar, which are inherently variable. Current technology in RFB & apos;s is largely based on sodium/sulfur chemistry, which requires high temperatures, and which operates well at large scale but is unsuitable for smaller or portable installations. Aqueous flow batteries based on the redox properties of vanadium, have also been quite extensively investigated, and although this chemistry is promising, it suffers from limitations of capacity and cost. Vanadium redox chemistry is based on a single metal, and this is a considerable advantage due to the problems of crossover when there are two distinct active materials, separated by a membrane. The proposal describes preparation of new materials for use in a single-substance organic based redox flow battery that uses non-aqueous solvent. Our team has designed and demonstrated materials for RFBs with equilibrium potentials unprecedented for an organic system, which can be cycled stably for extended periods. The materials have the unusual property of being both reversibly oxidized and reduced in non-aqueous solvent and these redox reactions are typically separated by 2.8 volts. A primary goal of this project will be to obtain maximum energy density by increasing the solubility of the active species to 0.6 M or higher allowing us to exceed the energy density of aqueous vanadium systems. A second goal will be to demonstrate the stability and energy efficiency of batteries using these materials. Both of these goals can be reached by judicious selection of the groups attached to redox active sub- structure that we describe herein. This novel organic system maintains the advantage of a single substance device, which minimizes the deleterious effects of crossover and reduces the need for a highly selective membrane. The single material system simplifies the fabrication of cells since only one standard method is needed. The all-organic system is potentially cheaper and greener than a metal based system. The synthetic route to the active material is short, and makes use of commodity reagents. An organic system may be particularly suitable for medium sized or portable applications, where it can operate in parallel with the typical solar or wind sources that are already in common use. If this system can be developed to the stage of commercialization, it will be a very useful addition to the management of the highly dispersed power grid. The commercialization plan for phase II will develop prototype devices and evaluate them for efficiency, cost and reliability. We will identify and test solvent-electrolyte and membrane combinations that maximize efficiency and minimize cost (target: & lt;$350/kWh at scale). A business management team will carry out market research and gain placement of devices in key market segments.
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