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

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.