A Safe Gelatin-Doped Hydrogel Electrolyte for Long-Life Quasi-Solid-State Zn Metal Batteries

Aqueous rechargeable Zn-ion batteries show promise for next-gen energy storage due to inherent safety, low cost, and eco-friendliness. However, Zn metal anode application faces challenges: uncontrolled dendrite growth and parasitic side reactions at the electrode-electrolyte interface, compromising cycling stability and electrochemical performance. In this study, a dual-cross-linked gelatin-based hydrogel electrolyte was developed to effectively regulate the interfacial behavior of Zn anodes. In the design, gelatin was introduced to partially replace 40% of polyacrylamide (PAM) as the primary polymer matrix, aiming to enhance the coordination capability with Zn²⁺ and improve the interfacial compatibility of the electrolyte. In symmetric cells, a stable operation exceeding 1500 h is achieved at 0.5 mA cm^-2/0.5 mAh cm^-2. In full-cell configurations, a capacity retention of 86.3% is maintained after 500 cycles at a current density of 1 A g^-1. This study offers fundamental insights for developing stable Zn anodes toward high-performance Zn-ion batteries.