Aqueous Flow Batteries Utilizing Redox-Active Organic Molecules: Phenazine Derivatives As a Promising Anolyte Material

Redox flow batteries have gained increased attention for grid energy storage. The decoupling of power and energy between stack and electrolyte tanks offers tunability to system parameters and, when based on an aqueous electrolyte, offers a level of safety not available in traditional lithium ion batteries. The current state-of-the-art aqueous flow battery is the vanadium redox flow battery. While this system possesses desirable features of high solubility, high cell voltage, and long cycling life, the high cost of vanadium has prevented wide-scale deployment. Redox-active organic molecules have emerged as a promising alternative to vanadium. Systems based on organics offer significant synthetic tunability to optimize critical design parameters of solubility, cell voltage, and cycle life. If derived from low-cost commodity chemicals, organic systems offer a pathway to lower-cost flow battery electrolytes. Presented will be our investigation of phenazine-based anolyte species. Our approach toward molecular functionalization will be detailed, which has yielded systems that offer beyond 2e - equivalent concentrations and high cell voltages up to 1.4 V when coupled with a ferricyanide catholyte.