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 Cu_xZn_y 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.