Sulfonate-Based Triazine Multiple-Electron Anolyte for Aqueous Organic Flow Batteries

Abstract

<p>A new highly soluble triazine derivative <b>(SPr)₃4TpyTz</b> showing three reversibleredox processes with fast kinetics and high diffusion coefficientshas been synthesized using an efficient, low-cost, and straightforwardsynthetic route. Concentrated single cell tests and DFT studies reveala tendency of the reduced triazine species to form aggregates whichcould be avoided by tuning the supporting electrolyte concentration.Under the right conditions, <b>(SPr)₃4TpyTz</b> shows no capacity decay and good Coulombic, voltage,and energy efficiencies for the storage of two electrons. The storageof further electrons leads to a higher capacity decay and an increaseof the electrolyte pH, suggesting the irreversible protonation ofthe generated species. So, a plausible mechanism has been proposed.A higher concentration of <b>(SPr)₃4TpyTz</b> shows slightly higher capacity decay and lowerefficiencies due to the aggregate formation.</p>