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 × 10 –5 S cm –1 at 30 °C and reaches 5.92 × 10 –4 S cm –1 at 60 °C, which is considered a satisfactory value for potential application in lithium-ion batteries. The specific discharge capacity of the LiFePO 4 /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 °C. In order to further improve the conductivity, Li 1.3 Al 0.3 Ti 1.7 (PO 4 ) 3 (LATP) ceramic electrolyte particles are dispersed in a PIL polymer matrix to prepare the PIL-LiTFSI-LATP composite electrolyte. LiFePO 4 /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 °C). This work may provide a unique way to prepare a new series of electrolytes for high-performance solid-state lithium batteries.