A Sustainable and Scalable Approach for In‐Situ Induction of Gradient Nucleation Sites in Biomass‐Derived Interface Layers for Ultra‐Stable Aqueous Zinc Metal Batteries

Aqueous zinc metal batteries are promising candidates for large‐grid energy storage due to their safety, cost‐effectiveness, and durability. However, challenges like dendrite growth, corrosion, and the hydrogen evolution reaction (HER) on the zinc anode hinder their performance. Herein, we propose a sustainable and scalable approach to form a copper gluconate@carboxymethyl chitosan@kaolin (CuCK) interface layer, inducing gradient nucleation sites via in‐situ galvanic and galvanostatic processes. The biomass‐based CuCK coating features a gradient CuxZny alloy structure that homogenizes interfacial electric field distribution and enhances electrochemical stability. Furthermore, the incorporated Cu2+‐loaded kaolin and carboxymethyl chitosan regulate Zn2+ flux, accelerate Zn2+ desolvation, and suppress HER. The resulting Zn@CuCK anode achieves a high cumulative capacity of 5500 mAh cm−2 in symmetrical cells, exhibits excellent durability in Zn@CuCK//NaV3O8·1.5H2O full cells across a wide temperature range (−30 to 60 °C), and endows the assembly of pouch cells with high energy density.