Amphiphilic electrolyte additive as an ion-flow stabilizer enables superb zinc metal batteries

Abstract

Irreversible Zn plating/stripping along with interfacial degradation seriously affect the practical applications of aqueous zinc-ion batteries. Herein, 3-(hydroxy(phenyl)phosphoryl)propanoic acid (HPA) is introduced as an electrolyte additive that constructs a spherical micellar molecular network via association of amphiphilic groups and multiple coordination sites to directionally adsorb/transfer Zn²⁺ in aqueous electrolyte, thus serving as an ion-flow stabilizer. Moreover, the strong adsorption between HPA and the zinc surface induces the formation of an in situ organic–inorganic hybrid solid electrolyte interphase layer, which further promotes the charge transfer kinetics and suppresses interfacial parasitic reactions. As a result, an ultra-high average Zn plating/stripping efficiency of 99.91% over 2100 cycles at 4 mA cm⁻² is achieved. Additionally, the symmetrical cell with HPA exhibits outstanding reversibility at an unprecedentedly high current density of 120 mA cm⁻². Surprisingly, the initial coulombic efficiency of Zn//Cu cell is 71.74% after 7-day calendar aging, which is better than a cell without HPA (42.59%). Furthermore, the Zn//MnO₂ cell exhibits superior capacity retention of 80% after 1100 cycles at 2 A g⁻¹ compared to the cell without HPA (37%). This study provides an in-depth insight into understanding the molecular network regulation of aqueous-based electrolytes, thus shedding light on a universal approach toward ultra-stable battery applications.