Creation of an Artificial Layer for Boosting Zn2+ Mass Transfer and Anode Stability in Aqueous Zinc Metal Batteries

Aqueous zinc metal batteries (AZMBs) are promising candidates for next-generation energy storage, but their commercialization is hindered by zinc anode challenges, notably parasitic reactions and dendrite growth. Herein, we present a biodegradable biomass-derived protective layer, primarily composed of curcumin, as a zincophilic interface for AZMBs. The curcumin-based layer, fabricated via a homogeneous solution process, exhibits strong adhesion, uniform coverage, and robust mechanical integrity. Rich polar functional groups in curcumin facilitate homogeneous Zn²⁺ flux and suppress side reactions. The curcumin-based layer shows a favorable affinity for zinc trifluoromethanesulfonate (Zn(OTf)₂) electrolyte, which is the representative of organic zinc salts, enabling optimal thickness for both protection and ion transport. The protected Zn anodes demonstrate an extended lifespan of 2500 h in symmetrical cells and a high Coulombic efficiency of 99.15%. Furthermore, Zn(OTf)₂-based system typically exhibits poor stability at high current densities. Fortunately, the lifespan of symmetrical cells was extended by 40-fold at the high current density. When paired with an NaV₃O₈·1.5H₂O (NVO) cathode, the system achieves 86.5% capacity retention after 3000 cycles at a large specific current density of 10 A g^-1. These results underscore the efficacy of the curcumin-based protective layer in enhancing the reversibility and stability of metal electrodes, specifically relieving the instability of Zn(OTf)₂-based systems at high current densities, advancing its commercial viability.