An Aqueous, Electrode-Decoupled Redox-Flow Battery for Long Duration Energy Storage

Abstract Redox-flow batteries (RFBs) enable large-scale energy storage at low cost due to the independent scaling of device power and energy, thereby unlocking energy arbitrage opportunities and providing a pathway to grid stability and resiliency. Herein we demonstrate an “electrode-decoupled” redox-flow battery (ED-RFB) with titanium and cerium elemental actives that has a clear pathway to achieve a levelized cost of storage (LCOS) of ca $0.025/kWh-cycle. A key enabling technology is our highly perm-selective modified poly(ether ketone)-based anion exchange membrane (AEM) that ensures long term separation of Ti and Ce species and enables capacity-fade-free cycling over 1300 hours of operation. Further, our Ti-Ce ED-RFB exhibits negligible capacity fade when the actives are charged to 90% state of charge (SOC), stored for close to 100-hours and then discharged, rendering it viable for long duration (load-following) grid-scale energy storage applications. Herein we introduce the Ti-Ce ED-RFB as a novel, low-cost long duration energy storage (LDES) system.