An Inter‐Locking Quasi‐Solid Cathode for Zinc‐Bromine Batteries with Stable 32000 Cycles

Zinc-bromine static batteries employing solid bromine cathodes present compelling advantages of low-cost, high-safety, and extended-lifespan for large-scale energy storage applications. However, solid-state bromine cathodes suffer from polybromide-induced shuttle effects and substantial volume variations, leading to poor reversibility and severe self-discharge. Herein, an inter-locking, quasi-solid bromine cathode enabling energetic static zinc-bromine batteries are developed. Theoretical calculation and characterizations confirm that polyacrylamide (PAM) effectively encapsulates tribromide molecules within the charged bromine cathode, suppressing bromine dissolution and mitigating self-discharge. Meanwhile, its flexibility accommodates volume changes and maintains conductive integrity. The resultant zinc-bromine battery achieves ≈32000 cycles at 1 mAh cm^-2, with an ultralow decay rate of 0.00016% per cycle. Meanwhile, it delivers scalable areal capacity up to 50 mAh cm^-2. Pouch cell with 200 mAh demonstrates remarkable stability of 3500 cycles, while displays capacity retention of ≈93% after 48 h resting. The 1.5 Ah pouch cell delivers a practical energy density of 70 Wh kg^-1 based on the total mass of pouch cell, while its modular integration (≈18 Wh) enables storage of hybrid energy harvesting from solar and wind sources, demonstrating versatile applicability in multi-scenario energy systems. This strategy establishes a viable pathway for developing practical zinc-bromine batteries toward grid-scale energy storage applications.