Double Eutectic Electrolytes With Optimized Inner-Outer Solvation Shell Engineering for Interphase-Stabilized Zinc-Metal Batteries.

Abstract

Eutectic electrolytes (EEs) are promising for zinc-metal batteries. However, traditional EEs suffer from high viscosity and severe ion migration hysteresis. Although hydration improves ion transport, it simultaneously intensifies corrosion-related issues. Here, an original electrolyte system based on a double eutectic electrolyte (DEE) is proposed that employs strong Lewis acid-base interactions in the inner solvation shell alongside a reconstructed hydrogen-bonding network in the outer solvation shell, thereby achieving a good balance between ion transport kinetics and corrosion challenges. Moreover, the DEE modulates the electrochemical interface to form a stable and effective solid electrolyte interphase (SEI) layer, mitigating water corrosion and promoting uniform Zn deposition. Thus, symmetric cells based on the DEE demonstrate significantly extended cycle lives of 5900 h at 1 mA cm^-2, 1 mAh cm^-2 with minimal voltage polarization, and maintain over 3300 h even at 4 mA cm^-2, 4 mAh cm^-2. The system also demonstrates outstanding performance at -20 °C, sustaining long-term cycling up to 8000 h at 0.5 mA cm^-2. Furthermore, full cells with a low N/P ratio of 5.89 achieve stable cycling for 1000 cycles with 82.4% capacity retention, and pouch cells (mass loading: 103 mg) exhibit excellent durability over 2000 cycles at 0.5 A g^-1.