Interfacial Regulation by Polycationic Polymers for Dendrite‐Free Zinc Deposition in Alkaline Zinc‐Iron Flow Batteries

ABSTRACT Zinc‐based flow batteries (ZFBs) have emerged as promising energy storage systems due to their high theoretical gravimetric capacity, low electrochemical potential, natural abundance of zinc, and cost‐effectiveness. However, their widespread adoption is hindered by the persistent issue of zinc dendrite formation. Herein, we report a facile yet effective strategy to suppress dendrite formation by introducing polyquaternium‐6 (PQ‐6) as a functional electrolyte additive. Spectroscopic and electrochemical analyses reveal that PQ‐6 preferentially adsorbs at the electrode‐electrolyte interface, forming a dynamic barrier that modulates the zincate ion diffusion from a two‐dimensional (2D) to a three‐dimensional (3D) mode and promotes homogeneous nucleation. Consequently, the PQ‐6 modified alkaline zinc‐iron flow battery (AZIFB) exhibits exceptional cycling stability (nearly 400 h, 1200 cycles) while maintaining high energy efficiency (70.37%) at a current density of 80 mA cm −2 . This work not only provides an effective strategy for mitigating zinc dendrite growth but also advances the development of sustainable and high‐performance zinc‐based flow batteries.