One-step preparation of anti-freezing and flame-retardant eutectic gel electrolyte for assembling flexible and high-performance zinc-ion battery

Flexible zinc-ion batteries have attracted considerable attention as a promising candidate due to their intrinsic safety, high specific capacity, low cost, and environmental benefits. The choice of electrolyte plays a critical role for the battery performance. The eutectic gel electrolyte with the good merits has attracted many attentions recently. However, the high viscosity of the deep eutectic solvent (DES) will impair the gel ionic conductivity. To achieve a stable and high ionic conductive electrolyte, combined a zinc deep eutectic solvent (ZDES) with a small amount of water directly dissolved a polyvinyl alcohol (PVA) to form a highly stable eutectic gel electrolyte (PVA-ZDES) via a one-step process. This gel electrolyte has a robust physical crosslinked network, offering good mechanical properties (maximum tensile strength of 0.74 MPa), fine ionic conductivity (4.55 × 10-3 S cm-1), a stable electrochemical window (∼2.1 V), anti-freezing and flame-retardant ability. The assembled Zn‖PANI button battery based on the eutectic gel electrolyte have provided remarkable cycling stability (79% capacity retention after 2000 cycles at 1 A g-1) and excellent low-temperature performance (down to -35oC). Additionally, the in-situ assembly of a flexible soft-package battery has achieved depending on the rapid gelation, which can simplify the manufacturing process and optimize the electrode-electrolyte interface. This study has proposed a novel approach for designing and industrial producing the flexible and safe zinc-ion battery electrolytes in some extreme environments.