Radical Stabilization of a Tripyridinium–Triazine Molecule Enables Reversible Storage of Multiple Electrons.

A novel organic molecule, 2,4,6‐tris[1‐(trimethylamonium)propyl‐4‐pyridiniumyl]‐1,3,5‐triazine hexachloride, was developed as a reversible six‐electron storage electrolyte for use in an aqueous redox flow battery (ARFB). Physicochemical characterization reveals that the molecule evolves from a radical to a biradical and finally to a quinoid structure upon accepting four electrons. Both the diffusion coefficient and the rate constant were sufficiently high to run a flow battery with low concentration and kinetics polarization losses. In a demonstration unit, the assembled flow battery affords a high specific capacity of 33.0 Ah L−1 and a peak power density of 273 mW cm−2. This work highlights the rational design of electroactive organics that can manipulate multi‐electron transfer in a reversible way, which will pave the way to development of energy‐dense, manageable and low‐cost ARFBs. [ABSTRACT FROM AUTHOR]