Waste Biopolymer-Derived Self-Adjustable Interface for Practical Ah-Level Aqueous Zinc-Ion Batteries

Aqueous zinc-ion batteries (AZIBs) are promising for grid-scale energy storage, yet their practical viability is severely hindered by uncontrolled dendrite growth and parasitic reactions of the Zn negative electrode. Herein, inspired by the "waste-to-resource" design concept, we develop a sustainable waste biopolymer extracted from municipal sludge as a versatile electrolyte additive for high-performance Ah-level pouch cells. Combined experiments and theoretical calculations reveal that the designed biopolymer spontaneously self-assembles into a self-adjustable interface with stable and well-balanced hydrophilic-hydrophobic properties via the competitive adsorption rearrangement of amino acid segments. The self-adjustable interface fundamentally remodels the electric double layer (EDL) to achieve Zn²⁺ local self-enrichment and a water-poor interfacial solvation shell, which significantly facilitates Zn²⁺ transference and accelerates Zn²⁺ desolvation kinetics, thus effectively suppressing interfacial parasitic reactions and dendrite growth. Consequently, the Zn negative electrode achieves high reversibility at 20 mA cm^-2, and the VO₂‖Zn full cell sustains remarkable cycling stability for 15 000 cycles. Furthermore, a 2.2 Ah pouch cell demonstrates operational stability for 250 cycles. This work establishes a viable route to develop economic and sustainable electrolyte additives from waste.