Suppression of extensive ice formation in hydrogel electrolytes enabling low-temperature aqueous Zn batteries

Abstract

The application of hydrogel electrolytes in aqueous Zn batteries presents a promising approach to addressing challenges at Zn anodes, leveraging their flexible texture and reduced water activity. However, freezing and low ionic conductivity, particularly at low temperatures, remain critical obstacles. In this work, an antifreeze hydrogel electrolyte (PVA-0.5SL) is developed by incorporating organic sulfolane (SL) into a PVA-based hydrogel, effectively reshaping the spatial distribution of chemical components and disrupting the H-bonding network. Through FTIR chemical imaging, Raman spectroscopy, and DSC analysis, we reveal that the optimal SL concentration induces the formation of SL–Zn salt aggregation, which interrupts the H-bonding network and significantly suppresses extensive ice crystallization at extremely low temperatures. The PVA-0.5SL hydrogel achieves a high ionic conductivity of 3.64 mS cm⁻¹ at −40 °C. A Zn‖PANI full cell utilizing PVA-0.5SL demonstrates excellent rate performance and an ultra-long cycle life of 2400 cycles at low temperatures. This study offers new insights into engineering antifreeze hydrogel electrolytes by tailoring H-bonding networks through the introduction of heterogeneous phases.