Novel Anolyte Redox Active Organic Molecules for Redox Flow Battery Applications

Abstract

Non-aqueous redox flow batteries (NARFBs) offer several advantages over traditional aqueous electrolyte-based redox flow batteries, such as higher cell voltage, potentially higher energy density, and flexible operating temperatures. However, the current aqueous chemistries use toxic metals such as Vanadium and Chromium and highly acidic and oxidative acid mixtures. The efforts to develop metal-ligand based chemistries to tap the benefits of NARFBs have met with mixed success and only V(acac)3 based symmetric NARFBs have shown potential for long term operations. Even so, the solubility of V(acac)3 in non-aqueous solvents is low to compete with their aqueous counterpart. Moreover, modification of V(acac)3 to enhance the solubility has resulted in poor redox cyclability. As a result, recent research trends have shifted from the development of Metal-ligand complexes to small redox-active organic molecules (ROMs), which could provide higher solubility. However, due to the developing field, a few ROMs have been reported as stable electron donors and acceptors in their oxidized and reduced states. Therefore, we have focused on developing highly soluble anolyte materials with stable redox states. This presentation will discuss the design principle, synthesis, and electrochemical analysis of novel anolyte ROMs. The additional information about the kinetics, bulk electrolysis, and the performance in the full cell will also be discussed.