Dynamic diversity of soft medium-range homo-radical self-assembly and rigid metal-organic network in non-aqueous redox flow batteries

Understanding the physical and electrochemical rate processes which occur in the bulk of nonaqueous electrolytic solution is a major step towards control and design of electrochemical systems, e.g., nonaqueous redox flow batteries. Here, a combination of experimental SAXS ,conductance measurements, and computational molecular dynamics, is used to probe the dynamics of nonaqueous electrolytes as a varying function of the battery state of charge (SOC), and electrolyte concentration. Two solutions were compared: one contained metal cation electrolyte prone to form rigid hetero-charge network, and one contained phenothiazine organic catholyte preferring softer homo-radical stacking. For the latter, conductivity data show that a faster charge transport is present at high electrolyte concentration. This discrepancy in behavior becomes less pronounced as we go to lower concentration and is absent in the dilute limit. Our findings indicate enhanced dynamics in terms of bulk ionic conductivity driven by a softer medium-range emergent homo-radical stacking structure.