Solid Polymer Electrolyte Based on Polymerized Ionic Liquid for High Performance All-Solid-State Lithium-Ion Batteries

Polymerized ionic liquids (PILs) have several advantages over ionic liquids, such as easy handling, good electrochemical performance, and chemical compatibility. In this research, a solid-state electrolyte composite membrane was successfully fabricated by using an imidazolium-based polymerized ionic liquid as polymer matrix, a kind of porous fiber cloth as rigid frame, and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) as lithium salt. The ionic conductivity of the composite electrolyte with 2.0 mol/kg LiTFSI is 7.78 X 10(-5) S cm(-1) at 30 degrees C and reaches 5.92 x 10(-4) S cm(-1) at 60 degrees C, which is considered a satisfactory value for potential application in lithium-ion batteries. The specific discharge capacity of the LiFePO4/Li cell with as-prepared composite electrolyte is 138.4 mAh g(-1), and 90% of the discharge capacity is retained after 250 cycles at 60 degrees C. In order to further improve the conductivity, Li1.3Al0.3Ti1.7(PO4)(3) (LATP) ceramic electrolyte particles are dispersed in a PIL polymer matrix to prepare the PIL-LiTFSI-LATP composite electrolyte. LiFePO4/Li cells using PIL-LiTFSI-LATP (10 wt % LATP) as a solid-state electrolyte exhibit excellent rate performance and high capacity retention (close to 97% after 250 cycles at 60 degrees C). This work may provide a unique way to prepare a new series of electrolytes for high-performance solid-state lithium batteries.