Dynamic Solvation Structure Boosts Long-Life and High-Capacity Aqueous Zn Batteries.

Abstract

Aqueous Zn metal batteries (AZMBs) are promising candidates for next-generation energy storage due to their low cost and high safety. However, uncontrolled Zn dendrite growth under high current densities remains a critical challenge. Solvation structure engineering shows considerable potential in mitigating dendrite formation, but its effectiveness under realistic electric field conditions remains to be fully understood. In this work, we applied in situ extended x-ray absorption fine structure (EXAFS) spectroscopy and in situ Raman spectroscopy to directly probe the solvation behavior of Zn²⁺ under an applied electric field. By introducing a cost-effective electrolyte additive, we achieve a responsive "dynamic solvation structure" that adapts to rapid charge/discharge conditions, enhancing Zn stripping kinetics and promoting reversible Zn deposition. In situ and ex situ characterization techniques reveal that the additive effectively reduces polarization, suppresses inactive Zn accumulation, and facilitates fast charge transfer at the solid/electrolyte interface, significantly improving Zn cycling stability. As a result, our strategy demonstrates outstanding electrochemical performance, delivering a 650 mAh Zn─I₂ pouch cell with a high-utilization Zn anode (50%) and high-loading cathode for 300 cycles. This study presents a novel approach for optimizing Zn² ⁺ solvation dynamics, thereby paving the way for high-performance AZMBs.