One-step preparation of epoxy resin-based ionic gel electrolyte for quasi-solid-state lithium metal batteries

Quasi-solid-state lithium metal batteries have attracted wide attentions in recent years due to their high energy density, flexibility, and high safety. In this work, a novel epoxy resin-based ionic gel electrolyte (IGE) is synthesized via one-step curing polymerization of epoxy monomer and amine hardener with soft segments in the presence of ionic liquid electrolytes. The morphology and molecular structure of IGE are characterized by scanning electron microscopy, atomic force microscope and attenuated total reflection Fourier transform infrared. The amorphous microstructure and high thermal stability (≥270 °C) are identified by X-ray diffraction and thermogravimetric analysis. The obtained IGEs show high room temperature ionic conductivity from 0.05 mS cm−1 to 1.69 mS cm−1 due to the formation of dual continuous ionic conduction. In addition, the evolution of solid electrolyte interface (SEI) between IGE and lithium metal is investigated by electrochemical impedance spectroscopy, galvanostatic charge-discharge test, and X-ray photoelectron spectroscopy. Finally, the Li/IGE/LiFePO4 cells can maintain a discharge capacity of 157 mAh g−1 at 0.1 C after 50 cycles at 60 °C and 132 mAh g−1 at 0.2 C after 150 cycles at room temperature.