Optimizing Bromine Complexation and Kinetics: a Bisimidazole Strategy for High‐Performance Zn‐Br Static Batteries

Abstract

Abstract Zinc–bromine (Zn–Br) static batteries are promising for large‐scale energy storage, yet the practical application is hindered by the long‐standing trade‐off about bromine complexing agents (BCAs) between bromine complexation strength and redox kinetics. Herein, we report a rationally designed bisimidazolium salt, 1,4‐bis(3‐methylimidazolium‐1‐yl) butane dibromide ([bMImB]Br₂), which features a symmetric molecular structure that reconciles this contradiction. [bMImB]Br₂ demonstrates strong bromine affinity, stemming from its high atomic charge of N + and low solubility—properties comparable to those of tetraalkyl‐quaternary ammonium salts. Simultaneously, it retains low steric hindrance typical of monoimidazole compounds, thereby enabling fast electrode kinetics. As a result, Zn–Br batteries incorporating [bMImB]Br₂ deliver a high specific energy of 116 Wh·kg⁻¹, alongside an average coulombic efficiency (CE) of 99.22% and energy efficiency (EE) of 89.35% at 10 mAh·cm⁻ 2 (0.5 C) for over 150 cycles. Furthermore, the flexible pouch cell maintains a discharge capacity of 110 mAh and 99.7% CE over 100 cycles, even under mechanical deformation. This work offers a generalizable molecular design strategy for developing next‐generation BCAs in halogen‐based energy storage systems.