A Zn‐Dendrite Dissolving Membrane to Increase the Cycling Life of Zinc Bromine Flow Batteries

Abstract Zn‐bromine flow batteries (ZBFBs) have recently emerged as a reliable option in large‐scale energy storage. However, the inevitable growth of Zn dendrites on the Zn anode can eventually puncture the membrane that separates the anode and cathode and reaches the cathode to cause an internal short circuit, which significantly impacts the cycling stability and shortens the battery lifespan. The coating of the membrane with a layer of tetrabutylammonium tribromide (TBABr ₃ ), which actively dissolves Zn metal and thus prevents dendrite penetration through the membrane, is reported. The TBABr ₃ ‐coated membrane with Zn‐dissolving capability is shown to effectively increase the number of charge–discharge cycles of ZBFBs, tripling the cycling lifetime up to 700 h (360 cycles) at an areal capacity of 20 mAh cm ⁻² , which gives a cumulative capacity of up to 7.2 Ah cm ⁻² . The work serves as a model for the development of membranes that can chemically dissolve Zn‐dendrites to improve the cycling stability of ZBFB systems.