Interfacial Engineering by a Functional Polymer Additive Ensuring Highly Reversible Zn Metal Anodes

Aqueous zinc-ion batteries are plagued by dendrite growth and uncontrollable side reactions, which stem from an incompatible electrode-electrolyte interface. Herein, interfacial engineering by dextran sulfate sodium is developed to enhance the stability of the electrode-electrolyte interface. Experimental results and computational characterizations reveal that this polymer additive self-assembles into a protective layer on the anode surface, which isolates the anode from direct contact with water molecules, and can enter the Zn²⁺ solvation sheath to replace partial water molecules, thus synergistically mitigating the occurrence of side reactions. The enrichment of zincophilic and negatively charged sulfate groups in the polymer enhances Zn affinity and leads to homogeneous nucleation. Remarkably, with the assistance of this polymer additive, the Zn-Zn symmetric cells exceptionally survive for 10188 h at 2 mA cm^-2, and more reversible Zn plating and stripping are realized in the Zn-Cu asymmetric cells. More importantly, the assembled Zn-I₂ batteries deliver 50000 cycles at 10 A g^-1. The pouch cell exhibits stable performance for over 288 cycles at 6 mA cm^-2. This work highlights the vital role of molecular-level design of polymer additives in stabilizing the Zn metal anode.