Lithium-Containing Zwitterionic Poly(Ionic Liquid)s as Polymer Electrolytes for Lithium-Ion Batteries

Abstract

Polymer electrolytes are considered as the good candidates for the new-generation-safe lithium-ion battery. Herein, a free-standing and flexible polymer electrolyte film based on a lithium-containing zwitterionic poly(ionic liquid) (PIL) was constructed with and without propylene carbonate (PC) by in-situ photopolymerization. In this system, the lithium-containing IL synthesized by equimolecular neutralization of imidazolium-type zwitterion 3-(1-vinyl-3-imidazolio)propanesulfonate (VIPS) and lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) can both serve as the polymeric matrix of the polymer electrolytes to maintain sufficient mechanical strength and form Li+-rich channels for lithium-ion transportation. The ion–dipole interaction between the lithium ion and the polar solvent PC can further improve the lithium-ion conduction, resulting in a comparable ionic conductivity of ∼10–3 S/cm at 30 °C. Charge–discharge cycling performance of Li/LiFePO4 half-cell equipped with the PIL-based polymer electrolyte indicates the possibility of practical application. Simultaneously, the lithium-containing zwitterionic PIL fabricated by this facile method provides a promising model system for understanding the molecular interactions in promoting the lithium-ion conduction.