Regulating Zn 2+ Solvation Structure and Constructing a Hybrid Solid Electrolyte Interphase for Highly Stable Zn Anodes

Abstract

Aqueous zinc-iodine batteries present an enormous potential owing to their high safety and low cost for large-scale energy storage. Nevertheless, their practical viability is severely impeded by the thermodynamic instability of Zn anodes, which triggers hydrogen evolution reactions (HER), uncontrolled dendritic growth and polyiodide corrosion. Herein, we propose a synergistic dual-additive strategy utilizing 3mercaptopropionic acid (3-MPA) and ZnI 2 to stabilize Zn anodes via tailoring the electrode/electrolyte interface and modulating the primary solvation structure of Zn 2+ .Mechanistically, the preferential adsorption of MPA -and I -at the electrode/electrolyte interface regulates the in-situ formation of an organic/inorganic hybrid solid electrolyte interphase (SEI) rich in ZnS and ZnI 2 . This designed SEI effectively mitigates interfacial HER, suppresses polyiodide corrosion and facilitates uniform Zn 2+ flux.Within the bulk electrolyte, these additives also reconstruct the solvation sheath of Zn 2+ and disrupt the continuous hydrogen-bond network, thereby reducing the content of active water. Benefiting from the optimized interfacial environment, the Zn||Cu asymmetric cells achieve a high average coulombic efficiency of 98.7% over 5000 cycles. Moreover, Zn||I 2 full cells exhibit an exceptional capacity retention of 89.7% after 9000 cycles at 2 A g -1 . Ultimately, the electrochemical stability exhibited over a wide temperature range demonstrates the viability of this dual-additive strategy for practical all-climate energy storage applications.