Harnessing Ion-Dipole Interactions for Water-Lean Solvation Chemistry: Achieving High-Stability Zn Anodes in Aqueous Zinc-Ion Batteries.

Abstract

The reversibility and stability of aqueous zinc-ion batteries (AZIBs) are largely limited by water-induced interfacial parasitic reactions. Here, dimethyl(3,3-difluoro-2-oxoheptyl)phosphonate (DP) is introduced to tailor primary solvation sheath and inner-Helmholtz configurations for robust zinc anode. Informed by theoretical guidance on solvation process, DP with high permanent dipole moments can effectively substitute the coordination of H2O with charge carriers through relatively strong ion-dipolar interactions, resulting in a water-lean environment of solvated Zn2+. Thus, interfacial side reactions can be suppressed through a shielding effect. Meanwhile, lone-pair electrons of oxygen and fluorinated features of DP also reinforce the interfacial affinity of metallic zinc, associated with exclusion of neighboring water to facilitate reversible zinc planarized deposition. Thus, these merits endow the Zn anode with a high-stability performance exceeds 3800 hours at 0.5 mA cm-2 and 0.5 mAh cm-2 for Zn||Zn batteries and a high average Coulombic efficiency of 99.8 % at 4 mA cm-2 and 1 mAh cm-2 for Zn||Cu batteries. Benefiting from the stable zinc anode, the Zn||NH4V4O10 cell maintains 80.3 % of initial discharge capacity after 3000 cycles at 5 A g-1 and exhibits a high retention rate of 99.4 % against to the initial capacity during the self-discharge characterizations.