Dual-Cation Solvation Polymer Gel for Ultra-Stable Zn Anodes in Rechargeable Flexible Zn-Air Batteries

In semi-open rechargeable flexible zinc-air batteries (RFZABs), the polymer gel electrolyte, influenced by high-water-activity solvation structures during cycling, experiences slow ion conduction and severe dendrite growth, significantly reducing the durability of the zinc anode. This limits its application and development in wearable RFZABs. Thus, modifying the traditional single Zn²⁺ solvation structure is crucial for enhancing anode stability. Here, a dual-cation solvation strategy is proposed that fundamentally redefines polymer gel electrolyte chemistry and zinc deposition behavior. By incorporating L-cystine (Lcys) as a dynamic modulator within a polyvinyl alcohol (PVA) matrix, Zn²⁺ and Zr⁴⁺ are coordinated to form a robust dual-metal solvation network, which imparts multiple functional advantages: i) competitive solvation by Zr⁴⁺ lowers water activity in the Zn²⁺ coordination shell, effectively suppressing dendritic growth; ii) weakened PVA chain interactions create a "sliding-rail" dynamic solvation structure enhancing Zn²⁺ migration; and iii) solvated Zr⁴⁺ and Zr₃Zn₁[(OH)₂(H₂O)₄]₄ ⁸⁺ clusters cooperatively promotes uniform Zn deposition along the (002) crystal plane. As a result, Zn//Zn symmetric cells exhibit an ultralong cycling lifespan of 1628 h, and RFZABs demonstrate stable operation for over 212 h. This dual-cation solvation design offers a scalable and effective pathway for advancing durable, high-performance flexible energy storage systems.