The Chemistry behind Quinone Flow Batteries

Abstract

In order to make flow batteries cost-competitive for large-scale stationary storage, significant reductions must be made in the cost of the redox-active materials. We will show that organic molecules such as quinones offer dramatic cost reductions to the storage medium in comparison with metal-based electrolytes. Quinones also provide the ability to tune the redox and solubility properties of the molecules through the incorporation of various substituent groups onto the aromatic ring.We will report the synthesis, chemical, and electrochemical properties of several substituted quinone molecules. These results indicate that bulk solutions of quinones may be easily prepared and used as electrolyte solutions without purification. The reaction can be modified to affect the reduction potential of the solution, while maintaining rapid and reversible electrochemical kinetics. Finally, the unique electronic structure of quinone molecules is described to explain the origin of the fast, un-catalyzed two-electron redox kinetics.