Spontaneous Desaturation of the Solvation Sheath for High-Performance Anti-Freezing Zinc-Ion Gel-Electrolyte

Abstract

In recent years, gel-electrolyte becomes pivotal in preventing hydrogen evolution, reducing dendrite growth, and protecting the zinc metal anode for zinc-ion batteries. Herein, a polyvinyl alcohol-based water–organic hybrid gel electrolyte with Agar and dimethyl sulfoxide is designed to construct the spontaneous desaturation of the solvation sheath for reducing hydrogen evolution and dendrite growth at room temperature and even low temperature. According to experimental characterization and theoretical calculations, the well binding between multihydroxy polymer and H₂O is achieved in the hybrid desaturated gel-electrolyte to regulate the inner and outer sheath. The ionic conductivity of hybrid gel-electrolyte reaches 7.4 mS cm⁻¹ even at −20 °C with only 0.5 m zinc trifluoromethanesulfonate (Zn(OTf)₂). The Zn symmetric cells cycle over 1200 h under 26 and −20 °C with improved mechanical properties and electrochemical performance. The asymmetric Zn || Cu cell with hybrid gel electrolyte reaches ≈99.02% efficiency after 250 cycles. The capacity of full cell is maintained at around 74 mAh g⁻¹ with almost unchanged retention rate from 50 to 300 cycles at −20 °C. This work provides an effective strategy for desaturated solvation to reach anti-freezing and high-density Zn energy storage devices.