Natural biopolymers derived kinematic and self-healing hydrogel coatings to continuously protect metallic zinc anodes

Zinc (Zn) dendrite growth and hydrogen evolution corrosion reaction of Zn metal anodes greatly affect the cycling performance and hinder the commercial application of high safety aqueous Zn ion batteries. Building an excellent protective layer to perfectly solve the above problems is still a big challenge, resulting from its high-cost raw materials and complicated preparation processes. Herein, in this work, natural pectin biopolymer with galacturonic acid structure was adopted as a functional coating on Zn anodes (Zn@pectin) to realize the excellent cycling properties. Abundant oxygen-containing groups endow pectin films with self-healing ability and response kinematic via multiple intermolecular hydrogen bonds and ligand binding with Zn metal after in-situ gelation with Zn²⁺ ions, which can sustain the complete structure and fit closely on Zn surface to address the fracture and separation of protective layers with Zn electrode. Functional pectin coatings can serve as a physical barrier to reduce the corrosion effects of H₂O molecules in aqueous electrolyte and regular the deposition behavior of Zn²⁺ ions to hamper the dendrite growth. Zn@pectin symmetric cell can stably cycle for 2500 h at a current density of 2 mA cm⁻² and a constant capacity of 2 mAh cm⁻². Zn-iodine full batteries possess the high capacity retention of 95 % after 4500 cycles at 1 A g⁻¹. This work provides a new strategy for the protection of Zn metal anodes and realizes the resource utilization of renewable biomass.