Dendrite-free Zn metal anodes enabled by iodoacetamide-mediated synergistic solvation-interface modulation

Abstract

The reversibility and stability of zinc (Zn) metal anodes in aqueous zinc-ion batteries (AZIBs) are constrained by dendrite formation and parasitic reactions. To address these issues, iodoacetamide (IAM) is introduced as an efficacious and eco-friendly electrolyte additive to achieve superior long-life AZIBs. The carbonyl and amide groups of IAM coordinatively reconstruct the Zn²⁺ solvation shell while disrupting hydrogen-bond networks, thereby reducing water-induced parasitic reactions. The preferential adsorption of IAM on Zn surfaces effectively suppresses hydrogen evolution reactions (HER) and triggers the formation of a robust solid electrolyte interphase (SEI) layer containing SO₃^2-, ZnS, and Zn₃N₂-based compounds. Zn₃N_2, with its exceptional ionic conductivity, promotes the rapid ion transport kinetics, while sulfurized composites facilitate the desolvation of hydrated Zn²⁺ ions and hydrophobicity for H₂O repulsion, synergistically enabling reduced interfacial energy barriers, suppressed parasitic side reactions, and thereby achieving highly stable and dendrite-free Zn deposition. The Zn||Zn symmetric cell with the IAM additive demonstrates a remarkable cycling stability of over 4500 h at 1 mA cm⁻² and an excellent cycle stability of 300 h at a depth of discharge (DOD) of 85.4 %. The Zn||PANI full cell maintains a high capacity retention of 85 % after 25,000 cycles at 10 A g⁻¹.