Radical stabilization in organic flow batteries enabled by chirality

The practical realization of organic redox flow batteries (RFBs) for grid-scale energy storage is limited by complex active material degradation pathways frequently featuring one or more free radical species. Here we develop strategies for stabilization of mono- and di-radicals in organic 2e- electrolytes. Leveraging steric differences between isomers of cyclic triindole catholytes, we show that capacity fade arising from radical-based processes can be controlled by adjusting the chirality, intramolecular chiral induction, and degree of out of plane torsion – all without influencing redox potential. We further show that diradical decomposition follows at least two pathways, the preference for which can be biased using chirality, suggesting the presence of a chirality induced spin selectivity (CISS) effect. Once stabilized, triindole radicals can be co-formulated directly with viologen based electrolytes in 2e- symmetric, membraneless and all-organic full-cell configurations with little fade, air-tolerance, > 75% energy efficiency, robust self-discharge resistance and plausible pathways for large scale production.