Self-assembled interfacial protective layer toward high-performance aqueous zinc-ion batteries

Aqueous zinc-ion batteries with intrinsic safety and good electrochemical performance are promising energy storage technologies, whereas challenges such as H₂ evolution and Zn dendrite formation have hindered the attainment of satisfactory cycling longevity. Herein, a self-assembled anode protection layer is successfully prepared for achieving stable zinc anode in aqueous zinc ion batteries. Specifically, the zinc anode placed in slightly acidic solution slowly releases Zn²⁺ which interacts with the ethylenediaminetetraacetic acid disodium salt molecule (EDTA-2Na) in the solution, triggering the self-assembly of the EDTA-2Na/Zn²⁺ composite interface layer (EDTA_x@Zn), which is firmly anchored to the zinc anode through complexing action. EDTA_x@Zn can prevent direct contact between the electrolyte and the zinc anode, reducing side reactions, in conjunction with abundant carbonyl and amino functional groups, which can provide zincophilic sites to homogenize Zn²⁺ flux and accelerate Zn²⁺ desolvation-deposition, thereby stabilizing the zinc deposition interface. The modified zinc anode delivers a remarkable lifespan of over 1700 h at 1 mA cm⁻², 0.5 mAh cm⁻² in Zn‖Zn symmetrical cells. Moreover, the Zn‖Cu asymmetric cell operates over 847 cycles with a coulombic efficiency nearly 100 %. As a proof of concept, when paired with the Br₂ cathode, the battery provides a retention rate of 98 % over 470 cycles. This work provides an avenue to improve the reversibility of zinc anodes, promoting the further development of advanced zinc ion batteries in flexible devices.