Tailoring Membrane Surface Electrostatics to Regulate Zinc Deposition for Alkaline Zinc-Based Flow Battery

Membranes with selective ion transport and long-term stability remain urgently needed for energy devices, particularly in metal-based batteries, where dendrite penetration limits the battery cycling reversibility. Here, we develop a well-oriented charged composite membrane (CuAl-LDH-M) featuring a self-built surface electrostatic field to regulate zinc deposition. Using advanced surface probe microscopy, we directly quantify and map the positive surface potential of 0.2–0.8 V for CuAl-LDH-M, which facilitates the regulation of negatively charged zincate ions at the membrane–electrode interface. As a result, CuAl-LDH-M enables alkaline zinc–iron flow batteries (AZIFBs) to achieve epitaxial zinc deposition with a dense and uniform morphology. The AZIFBs show exceptional reversibility over a wide range of areal capacities (120–260 mAh cm–2) and sustain an energy efficiency of 84% at a high current density of 200 mA cm–2. This work offers insight into the role of membrane surface charge in regulating zinc deposition and inspires the design of next-generation membranes.