Bulk-to-interphase polybromide confinement and electric-field-responsive recovery enable Ah-level aqueous zinc-bromine batteries at room/low temperatures

Abstract

Aqueous Zn-Br2 batteries are promising candidates for grid-scale energy storage owing to their low cost and inherent safety. However, their areal capacity and cycling stability are severely limited by detrimental polybromide shuttling, which arises from concentration-gradient-driven diffusion and often overlooked internal-electric-field-accelerated electromigration. Herein, a bulk-to-interphase synergistic regulation strategy is proposed integrating electrostatic micropore confinement in the cathode bulk with additional interfacial anchoring and electric-field-responsive recovery at the cathode/electrolyte interphase. Poly(quaternary ammonium)-functionalized activated carbon (N+-AC) hosts are rationally designed to trap polybromide anions within positively charged micropores of cathode bulk, thereby suppressing concentration-gradient-driven leakage while maintaining fast conversion kinetics. Simultaneously, 1-butyl-3-methylimidazolium chloride (1, 3-MI) electrolyte additive absorbed on cathode surface provide additional polybromide anchoring at the interphase. Importantly, theoretical calculations and in-situ characterizations demonstrate that an electric-field-responsive 1, 3-MI accumulation layer forms spontaneously during discharge, dynamically attracting polybromides and inhibiting their electromigration toward the anode, thus promoting their recovery to the cathode for reversible redox conversion. Consequently, the N+-AC||Zn full cell with 1, 3-MI achieves stable cycling over 1000 cycles at an ultrahigh areal capacity of 10 mAh cm−2. Furthermore, Ah-level Zn-Br2 pouch cells operate stably at both room and subzero temperatures, validating the practical potential of this electric-field-aware bulk-to-interphase regulation strategy under complex climatic conditions.