Electric-field-reinforced affinitive electrolytes for highly reversible aqueous zinc metal batteries.

Abstract

Aqueous Zn metal batteries offer a safe, low-cost route to grid-scale energy storage yet suffer from dendrite growth and corrosion issues. Conventional electrolyte designs largely overlook electric-field-driven interfacial dynamics such as solvation structure evolution and component redistribution during operation. Here, we propose an affinitive additive strategy featuring high donor number and dipole moment, exemplified by N,N-dimethylurea (DMU), to dynamically modulate Zn²⁺ solvation and the structure of the electric double layer under operational electric fields. Guided by physically grounded molecular descriptors, we identify additives capable of electric-field-induced interfacial enrichment, during which strong dipole-field coupling promotes their incorporation into the Zn²⁺ solvation shell and promotes more uniform Zn deposition. As a result, the optimized electrolyte achieves a coulombic efficiency of ~99.9% for Zn plating/stripping with only 2 wt% additive. It also sustains stable operation for 700 h at 60% depth of discharge, outperforming the baseline electrolyte. Descriptor-guided screening further reveals that other candidates follow the same pattern, suggesting broader applicability of this approach. Practical Zn | |ZnI₂ full cells with high areal capacity (~3 mAh cm^-2) and low N/P ratio (~1.8) achieve 750 stable cycles at 0.15 A g^-1 with 84.5% capacity retention.