In Situ Molecular Self-Assembly for Dendrite-Free Aqueous Zn-Ion Batteries

Abstract

The large-scale application of low-cost and environmentally-compatible aqueous Zn-ion batteries (AZIBs) is largely hindered by the Zn dendrite growth stemming from inhomogeneous Zn deposition. To tackle this challenge, 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid is introduced as electrolyte additive to in situ construct ordered self-assembled monolayers on the Zn anode (Zn@HEPES), providing uniform active sites as Zn²⁺ nucleus regulators that can be dynamically and spontaneously replenished according to environmental conditions. Meanwhile, because of the regulated Zn²⁺ solvation sheath and the hydrophobicity of Zn@HEPES, the direct contact between active water molecules and Zn anode is effectively ameliorated, which promotes the Zn²⁺ transport and deposition kinetics. The above synergistic effects enable highly reversible Zn redox chemistry to achieve a uniform and dense Zn electrodeposition with suppressed Zn dendrite growth. Consequently, the thus-derived Zn||Zn symmetric cells exhibit an excellent long-term stability for 4000 h at a current density of 1 mA cm⁻². Additionally, with the aid of Zn@HEPES, the full cells coupling Zn anode and MnO₂ cathode also demonstrate superior reaction reversibility and capacity retention. This work demonstrates a distinctive avenue at the molecular level for precisely regulating the Zn electrodeposition process to achieve practical AZIBs.