Ultrafast Anion‐Hopping Conduction in Organic Solvent via Imidazolium‐Grafted Dynamic Ion‐Conducting Spacers for Stable Non‐Aqueous Flow Batteries

Abstract

ABSTRACT Non‐aqueous flow batteries (NAFBs) require membranes with superior organic solvent resistance and high ionic conductivity in organic solvents to endure the corrosive effects inherent in non‐aqueous electrolytes. Herein, we designed a highly organic‐solvent‐resistant imidazolium‐grafted anion‐exchange membrane (AEM) for NAFBs, realizing rapid anion hopping conduction in organic solvents. The membrane exhibited an ultrafast ionic conductivity as high as 2.1 mS cm −1 in DMF‐based electrolyte which was much greater than that of the commercial Celgard membrane (only 0.45 mS·cm −1 ), coupled with exceptional barrier properties evidenced by ultralow active‐species permeability values of 1.6 × 10 −8 cm 2 s −1 for 2,1,3‐benzothiadiazole anolyte and 3.8 × 10 −9 cm 2 s −1 for 10‐methylphenothiazine catholyte, respectively. Moreover, the membrane demonstrated outstanding stability in aggressive organic solvent, achieving an average energy efficiency (EE) over 66.1% for over 330 cycles at 5 mA cm −2 in a NAFB cell test, which far exceeded the commercial Celgard membrane (with only 70 cycles with an average EE of 48.8%). This research presents a strategic advance in next‐generation membrane design for NAFBs with exceptional organic solvent resistance and high ionic conductivity.