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.