Sustainable and Multifunctional Natural Macromolecular Polymers for Aqueous Zn Metal Batteries

Aqueous zinc-ion batteries (AZIBs) have emerged as a highly competitive energy storage system, owing to their inherent safety, ideal capacity, and the abundance of zinc resources. However, the practical applications of AZIBs are significantly hampered by challenges such as uncontrolled dendrite growth, corrosion, and passivation of zinc anodes. Natural macromolecular polymers, leveraging their multifunctionality, sustainability, and multilevel structures featuring superior mechanical strength, demonstrate unique potential in the development of effective strategies for optimizing zinc anodes. This review is the first to systematically analyze, at both the microscopic and mesoscopic levels, the structure-function relationships between the structural/surface characteristics of natural polymers and their optimization effect on zinc anodes, and elucidates the relevant regulatory mechanisms. Concurrently, the research progress on optimizing zinc anodes with these natural polymers is sorted out and analyzed according to different optimization strategies, further illustrating the interrelationship among the structure/properties of natural polymers, zinc anode optimization strategies, and regulatory mechanisms. Additionally, the review identifies and outlines the crucial challenges faced by natural polymers in terms of optimizing zinc anodes. Ultimately, this review also delivers some prospects for future research directions and innovative engineering strategies focusing on natural polymers to construct ultra-stable zinc anodes for large-scale applications.