Zinc-dual-halide complexes suppressing polyhalide formation for rechargeable aqueous zinc-halogen batteries.

Aqueous zinc-halogen batteries suffer from poor coulombic efficiency and short cycle life owing to the formation and dissolution of polyhalides in electrolytes. Herein, we apply a zinc-dual-halide complex strategy to confine free halides and suppress polyhalide formation. The high stabilities of zinc-dual-halide complexes are identified to be essential for effective confinement. The resulting Zn-Br and Zn-I cells deliver excellent rate capability and cycling stability, as well as high coulombic efficiency and energy efficiency.