A Stable and High-Capacity Redox Targeting-Based Electrolyte for Aqueous Flow Batteries

Aqueous redox flow batteries (ARFBs) have received considerable attention for large-scale energy storage because of their salient feature of decoupled energy storage and power generation; however, their deployment is critically constrained by low energy density and relatively high cost. Here, we report a low-cost, high-capacity ferrocyanide/ ferricyanide ([Fe(CN)(6)](4-/3-))-based electrolyte system via the redox targeting reactions with Prussian blue (Fe-4[Fe(CN)(6)](3), PB). The [Fe(CN)(6)](4-/3-)-PB electrolyte exhibits an excellent capacity retention of 99.991% per cycle and an unprecedented capacity of 61.6 Ah L-1. A Zn/[Fe(CN)(6)](3-) -PB flow cell with energy density of 97.4 Wh L-1 at 20 mA cm(-2) and a [Fe(CN)(6)](4-/3-)/Br- flow cell with PB as the sole solid material were demonstrated. The battery chemistry and associated redox targeting reactions were scrutinized with computational, neutron diffraction, and spectroscopic studies. The ultra-stable and capacity-intensive [Fe(CN)(6)](4-/3-)-PB electrolyte system presents an intriguing paradigm for advanced cost-effective large-scale energy storage.