Nature-Derived Organic Mesomeric Electrolyte For Low Cost And High Capacity Aqueous Flow Battery

Organic redox flow batteries have the potential to surpass the challenges posed by inorganic electrolytes commonly used in flow batteries, thus achieving high performance and a sophisticated storage solution for the grid. Herein, we demonstrated a high performance aqueous organic redox flow battery (AORFB) utilizing a redox active resource from nature, IC, as the anolyte. The IC-H is obtained through substitution of sodium ions with protons (H+). The aqueous solubility was increased dramatically from 0.035 M to 0.760 M (theoretical capacity ~37.0 Ah L-1 and theoretical energy density ~28.2 Wh L-1) in protic solvents by enhancing hydrogen bonding. The revealed diffusion coefficients (IC-Na: 3.38 ×10-5 and IC-H: 2.23 ×10-5 cm 2 s −1) and reaction rate constants (IC-Na: 2.32 × 10-4 and IC-H: 2.82 ×10-4 cm s-1) indicate rapid reaction kinetics. The highly soluble constructs high-performance AORFB, when paired with bromine/hydrobromic acid catholyte, exhibiting high capacity of 24.2 Ah L-1 at 40 mA cm-2 with round-trip energy efficiency and capacity retention exceeding 77 % and 99.96 % per cycle. Moreover, computational study signifies the prospect of further improvements in solubility and voltage window by tuning the structure. Therefore, the environmentally benign and earth-abundant natural dye represents a promising choice for green and sustainable redox active anolyte of AORFB.