High-Performance Alkaline Organic Redox Flow Batteries Based on 2-Hydroxy-3-carboxy-1,4-naphthoquinone

Aqueous redox flow batteries (ARFBs) based on the electrolyte solutions of redox-active organic molecules are very attractive for the application of large-scale electrochemical energy storage. We propose a high-performance ARFB system utilizing 2-hydroxy-3-carboxy-1,4-naphthoquinone (2,3-HCNQ) and K 4 Fe(CN) 6 as the anolyte and catholyte active species, respectively. The 2,3-HCNQ molecule exhibits high solubility and can carry out a reversible two-electron redox process with rapid redox kinetics. The assembled 2,3-HCNQ/K 4 Fe(CN) 6 ARFB delivered a cell voltage of 1.02 V and realized a peak power density of 0.255 W cm –2 . The 2,3-HCNQ/K 4 Fe(CN) 6 ARFB can be stably operated at a current density of 100 mA cm –2 for long-term cycling (with a capacity retention of ∼94.7% after 100 cycles).