Dual-function regulation of organic complexes: anode upgrade for aqueous zinc-ion batteries

During the cycling of zinc anodes, issues such as dendrite growth, side reactions, and self-corrosion severely limit their cycle life and stability. In this study, cerium acetylacetonate [Ce(AcAc)₃, abbreviated as CAA] was innovatively introduced as a functional additive into the zinc sulfate (ZnSO₄) electrolyte. CAA combines the properties of rare-earth metal cerium ion (Ce³⁺) and acetylacetonate anion (AA^-) ligand. AA^- exhibits spontaneous adsorption characteristics, which can precisely regulate the electric double layer (EDL) structure and form a "water-deficient and zincophilic" inner Helmholtz plane (IHP) on the electrode surface. Meanwhile, AA^- can optimize the Zn²⁺ solvation structure in the form of [Zn(AA)(H₂O)₄]²⁺, significantly reduce the content of active water in the electrolyte, inhibit the hydrogen evolution reaction (HER), and mitigate uncontrollable side reactions. The Ce³⁺ facilitates the uniform deposition of zinc ions on the electrode surface through the electrostatic shielding effect, thereby suppressing dendrite growth. AA^-and Ce³⁺ act dually, complement each other's advantages, and reinforce one another, exerting a positive effect on the performance of Zn anodes, significantly enhancing their cycling stability and effectively extending their service life. Experimental results demonstrate that the electrolyte containing CAA (ZnSO₄/CAA) enables the Zn||Zn symmetric cell to cycle stably for more than 3200 h at a current density of 1 mA cm^-2. The Zn||MnO₂ full cell maintains 92% capacity after 2000 cycles at 3 A g^-1. This strategy offers a novel perspective into the electrolyte design of high-performance aqueous zinc-ion batteries.