Preparation of polymer electrolytes based on the polymerized imidazolium ionic liquid and their applications in lithium batteries

The polymer electrolytes based on a polymerized ionic liquid (PIL) as polymer host and containing 1,2-dimethyl-3-butylimidazolium bis(trifluoromethanesulfonyl)imide (BMMIM-TFSI) ionic liquid, lithium TFSI salt, and nanosilica are prepared. The PIL electrolyte presents a high ionic conductivity, and it is 1.07 × 10^-3 S cm^-1 at 60°C, when the BMMIM-TFSI content reaches 60% (the weight ratio of BMMIM-TFSI/PIL). Furthermore, the electrolyte exhibits wide electrochemical stability window and good lithium stripping/plating performance. Preliminary battery tests show that Li/LiFePO₄ cells with the PIL electrolytes are capable to deliver above 146 mAh g^-1 at 60°C with very good capacity retention.