Molecular Engineering of an Alkaline Naphthoquinone Flow Battery

Aqueous organic redox
flow batteries (AORFBs) have recently gained
significant attention as a potential candidate for grid-scale electrical
energy storage. Successful implementation of this technology will
require redox-active organic molecules with many desired properties.
Here we introduce a naphthoquinone dimer, bislawsone, as the redox-active
material in a negative potential electrolyte (negolyte) for an AORFB.
This dimerization strategy substantially improves the performance
of the electrolyte versus that of the lawsone monomer in terms of
solubility, stability, reversible capacity, permeability, and cell
voltage. An AORFB pairing bislawsone with a ferri/ferrocyanide positive
electrolyte delivers an open-circuit voltage of 1.05 V and cycles
at a current density of 300 mA/cm2 with a negolyte concentration
of 2 M electrons in alkaline solution. We determined the degradation
mechanism for the naphthoquinone-based electrolyte using chemical
analysis and predicted theoretically electrolytes based on naphthoquinones
that will be even more stable.